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Download English Transcript: Basic Principles of Biomechanics Part 1

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Welcome to the Basics of Biomechanics. This is a simple guide that will teach you the basic principles of biomechanics that we can later apply to the upper limb, the spine, and the lower limb. In this section, we'll be looking at basic concepts in joint anatomy and the types of diarthrodial joints, joint function in the form of kinematic chains, and arthrokinematics.

We'll also be looking at muscle and tendon physiology, muscle physiology and biomechanics, common injuries in muscle, injury grading of muscle, and related sports and rehabilitation. We'll also be looking at ligament physiology, common injuries in ligaments, injury grading of the ligament injuries, and related sports and rehabilitation.

Before we go into the details of joints and anatomy, we need to know the fundamentals of anatomical positioning, the axes of rotation, and the anatomy of a synovial joint. The axes of rotation- this is characterized by three lines that dissect the body. The x-axis is a line that runs transversely across the body, from left to right. The y-axis is a line that runs vertically through the body from cranial to caudal. And the z-axis is a frontal line that runs from anterior to posterior. The x, y, and z-axes combined in pairs form different planes, as you'll see ahead of this slide. We will work in these planes and see what movements go about these planes.

The sagittal plane divides the body into left and right halves. It is demarcated by the y and z-axes combined. The movements of flexion and extension move through this plane. If we had to visualize flexion at the shoulder joint, we would see the anterior movement of the upper extremity through the sagittal plane, where there was a point of rotation about the x-axis at the centre of rotation of the shoulder joint.

The coronal plane divides the body into anterior or ventral and posterior or dorsal halves. It is demarcated by the y and x-axes combined. Movements of abduction and adduction are seen to move through this plane. If we had to visualize abduction of the shoulder joint, we would see the upper limb being elevated through the coronal plane, laterally away from the body. The point of rotation would be seen at the shoulder joint, rotating about the z-axis.

The transverse plane divides the body into superior and inferior halves. It is demarcated by the x and z-axes combined. Movements of rotation move through this plane. If we had to visualize the medial rotation of the upper limb with the elbow bent, we would see the translation of the hand medially towards the tummy. This is a rotation at the centre point of the joint about the y-axis of the shoulder joint.

The anatomy of a typical diarthrodial joint is also known as a synovial joint. It is characterized by free-moving ends, or epiphyses, encapsulated within a synovial lined joint space. The articular surfaces are free to move relative to each other because of no connective tissue directly connecting the surfaces. The shape of the joint surfaces dictates the motion potential of the joints itself.

Joint function-- the structure of the joints of the human body reflect the functions that the joints are designed to serve. The demand on the limb or segment that needs to move will dictate the type, shape, and size of joint needed. As the joints become larger and have more range of motion, the less stable the joint is. Therefore, we'll see more stabilizing factors in some joints, and less range of motion in others. This can be seen as an example in the shoulder joint or the glenohumeral joint specifically, where there's an extensive range of motion, but at the sacrifice of stability. The rotator cuff muscles and the rotator interval capsule have to apply different forces in order to stabilize the shoulder as accessory stabilizers for the joint.

These two diagrams are an example of how the joint functions and how the associated tissues replace the stabilization because of the joint shape. As said above, the glenohumeral joint is a large joint with very little stability in order to allow for large ranges of motion. The small stabilizers-being the rotator cuff muscles and the rotator interval capsule-- maximize stability as best as possible.

Here are a few examples of synovial joints and their specific locations. Your condyloid joint is found at the atlantooccipital joint. The ball and socket joint are found at the glenohumeral joint. And the coxofemoral joint- the gliding joint which is found at articular processes between vertebrae. The saddle joint is found at the carpometacarpal joints. The pivot joint is found at the dens of the axis between the atlas and the axis. And the hinge joint, which is also found at the
elbow.

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Download English Transcript: Basic Principles of Biomechanics Part 2

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Kinematic chains. This is a biomechanical term used for a series of rigid links that are interconnected by joints, which allow the limb to move in a predictable manner. It can either be an open kinematic chain or a closed kinematic chain.
In an open kinematic chain, one joint is able to move independently to the proximal joints and has the freedom to move through space. In a closed kinematic chain, the distal end of the limb is fixed, but the segments are able to move. There is no net change in limb position, but the movement has occurred. For example, when standing and shifting off balance, yet you have not moved from your original position.

In order to understand gross muscle contraction, we need to understand the concept of muscle length-tension relationships. In this diagram, we can see the relative link between the length of muscle tissue and the ability to contract as muscle contractile tissue.

We have an optimal zone, which is needed for maximal actin and myosin interaction. If the actin and myosin are packed too closely together, the sarcomere is unable to contract, as there is a restriction of space. Therefore, the sarcomere is rendered useless.
If the actin and myosin are separated too far apart, there is no ability for the calcium to create the polar bond and linkage. And therefore, there is no contraction, as there is no linkage between actin and myosin.

Active and passive inhibition. These are two biomechanical concepts that describe the behaviour of muscle when set in anatomical fields. Active inhibition is where the muscle contracts to the point where it cannot move the limb any further due to soft tissue obstruction. The muscle is still able to generate a contraction but is unable to move further.

In passive inhibition, the muscle cannot contract eccentrically, as the limb is stretched beyond the anatomical limits of the sarcomere. The muscle is unable to initiate contraction unless the length is reduced.

Muscle physiology and biomechanics. The muscles are our powerhouses and our movers of the body. Because of this, they tend to fatigue easily and can potentially get injured. By looking at the behaviour of muscle in contraction, we are able to determine when a muscle is injured, or underperforming due to altered mechanics and general muscle pain syndromes such as delayed onset muscle soreness.

Muscle testing is a simple and effective method of assessing muscle behaviour and potential injury. The factors that affect muscle strength are motor-unit summation and increased rate coding. In motor-unit summation, the more motor units the muscle uses to contract, the more summative contraction can be achieved. We see this in explosive forceful contractions such as that in sprinting.
In increased rate coding, increasing the rate of fire of each specific motor unit increases the total rate of recovery and re-contraction of the muscle. This is seen in the gradual buildup of muscle contraction, such as applying weight in weightlifting.

The factors affecting muscle tension are primarily dictated by the number of muscle fibres in that unit, and the size of the fibres i.e. the larger the fibres, the more tension that can be generated specific tension per cross-sectional area i.e. the smaller slow twitch fibres generate approximately 1.73 kilograms of tension per square centimetre. And larger fast twitch fibres generate about 2.23 kilograms of tension per square centimetre.

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Download English Transcript: Basic Principles of Biomechanics Part 3

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Injuries are usually seen as muscle strains. These are the most common and most feared by any athlete. They may occur due to overuse, for example, repetitive motion, such as pitching in baseball or due to forceful overload in a sports activity, for example, hamstring strain during the launch of a plate in the long jump. They are graded from grades 1 to grade 3. Here's a simple grading scale that can be used to understand and note what type of muscle strain you are dealing with.

In a grade 1 muscle strain, minor or microscopic tissue damage is noted. It is painful for the patient. They usually experience a severe cramp or spasm. It is not usually palpable. And it usually takes about 7 to 10 days for normal recovery back to 100% function. In grade 2, muscle strain, it is a moderate or macroscopic or partial thickness tear of muscle tissue. It is extremely painful for the patient. There is a muscle cramp or spasm. It is palpable by torn fibres in the muscle tissue. And rehabilitation is required for 10 to 21 days for normal recovery, usually between 80% and 100% return of normal muscle function depending on the thickness of the tear.

In grade 3 muscle strains, this is usually a severe maximal or full-thickness tear of the muscle tissue. The patient usually doesn't feel much pain, initially due to the loss of tension. It's usually a physical muscle deformity as the muscle has had a full-thickness tear. The muscle sheath or fascia may still remain attached to the tendon. Surgery and rehabilitation is usually required with a three-week to six-month recovery.

Tendonitis or tendonosis, are inflammatory conditions that affect the tendons directly. The most common mechanism of injury is due to overuse or increased leverage on the tendons in sports, such as racket-based sports. The most common forms are usually tennis elbow, golfer's elbow, and jumper's knee. The grading of tendon strains is similar to that of what we saw in muscle. Remember that we again grade on a  one, two and three scale as we did with muscle. Grade 1 tendon strain is minor or microscopic tissue damage. It is usually painful for the patient, not palpable, and has a seven to the 10-day recovery period, usually with non-steroidal anti-inflammatory drugs and/or compression.

In grade 2 tendon strains, it is a moderate or macroscopic effect on the tendon tissue. It is extremely painful for the patient. There is a palpable deficit in the tendon, usually in the form of swelling, such as in tenosynovitis. Rehabilitation is required, and it is commonly called an enthesopathy. Grade 3 tendon strains are known as severe or maximal or full-thickness tears of the tendon. It is usually associated with avulsion fractures as it's usually affected at the tendinous junction between the bone and the tendon.

Delayed Onset Muscle Soreness, or DOMS-- this is where the products of collagen breakdown from intense, rapid training may act as a chemotactic agent and inflammatory marker, causing macrophages to travel into the muscle tissue and begin an inflammatory response. The macrophages are non-specific phagocytes and break down imperfect and normal cells, thus causing tissue damage.
Hydroxyproline, or OHP, is a urine marker for early-onset DOMS. If DOMS is severe enough that it affects large amounts of tissue, the degradation will be seen by the rise of creatine kinase and may lead to rhabdomyolysis or other complications. Common treatments for DOMS include cryotherapy, regular stretching, ultrasound, light, low-resistance exercise, hyperbaric therapy, compression, massage therapy, and drugs in the form of non-steroidal anti-inflammatory drugs.

Ligaments-- ligament physiology. The ligaments are the primary restraints and guides for the joints. They provide the main line of support for normal joint motion. They are the last line of defence against joint hyperextension and instability. They are subject to continuous loading and are most affected by the phenomenon of "creep". Creep is a physiological phenomenon where there is tissue distortion over a period of time when a constant force is applied over a long period of time. We see this in general ligament laxity when a shoulder is overused or overstretched.

Common injuries of ligaments include ligament sprains. They are commonly due to joint malposition during a weight-bearing exercise. The most common version is an inversion sprain of the ankle, commonly in the running and in stop-or-start sports, such as netball or basketball. Joint hyperextension and instability, there's usually an overload of the ligaments, which may induce capsular stretching. There's also joint dislocation, which is common in contact sports due to the force of impact. And it commonly happens in juvenile-level sports where the ligaments are still stretching due to bone growth.
As seen before with muscle injury, we refer to a grade 1, grade 2, and grade 3 grading system for ligament damage. In grade 1 ligament sprains, you will see minor or microscopic tissue damage. It is painful for the patient. They usually experience acute or moderate swelling and minor hematoma formation. It is not usually a palpable defect. The joint's stability is usually maintained, but they may have minor instability masked by exaggerated apprehension and pain. It takes about 7 to 10 days to heal. And the weight bearing, or proprioception, is affected.
In a grade 2 ligament sprain, there is moderate or macroscopic partial thickness tearing. It is extremely painful for the patient. There is a large or significant swelling and hematoma. The muscle cramp or spasm may mask instability, but instability is seen easily with the naked eye. When the joint is placed under pressure or weight bearing, it is unbearable for the patient and proprioception is affected. Immobilization is required as soon as possible.

In a grade 3 ligament sprain, there is severe or maximal tissue tearing. The patient does not feel pain initially due to the loss of tension. There is gross joint instability, which is commonly seen and may also see repetitive joint dislocation if associated with a joint displacement. The proprioception is completely disrupted and may affect voluntary joint control. Surgery is commonly required with rehabilitation.

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Download English Transcript: Biomechanics of Spine Injuries in Sport

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Welcome to the basics of biomechanics. This is a simple guide to pick up on normal and abnormal biomechanical behaviour of the spine. In this section, we will be covering general spinal biomechanics, regional facet orientation, posture, and biomechanical syndromes of spinal posture.

Generals spinal biomechanics. The vertebral column resembles a curved rod composed of 33 vertebrae and 23 intervertebral disks. They are divided into the following five regions-- the cervical region, consisting of seven vertebrae; the thoracic or dorsal region, consisting of 12 vertebrae; the lumbar region, consisting of five vertebrae; the sacral region, consisting of five fused vertebrae; the coccygeal region, consisting of four fused vertebrae.

The vertebrae adhere to a common basic structural design but show regional variations in size and configuration that reflect the functional demands of a particular region. General spinal characteristics can be seen as follows. There is an increase in size from the cervical spine to the lumbar spine region.

In fetal life, the spine exhibits one long curve that is convex posteriorly as a C-shaped primary curve. The secondary curves that we see in the lumber and cervical regions develop secondarily in infancy. In an adult, there are four distinct anteroposterior curves. They are two in the thoracic and sacral regions, which are primary curves. They are convex posteriorly. And two in the cervical and lumbar region, which are secondary curves that are convex anteriorly. These develop as a result of the accommodation of forces on the skeleton to the upright posture.
A curved vertebral column provides a significant advantage to a straight rod, in that it is able to resist much higher compressive loads up to four times our own body weight. The image below represents the basic anatomical structure of the vertebrae, the supporting ligament structures, and the small anatomical differences between the different regions. Bear these in mind as we move further forward.

General vertebral anatomy. The vertebra consists of two major divisions-- the anterior vertebral body portion or the posterior vertebral or neural arch division. The vertebral body is designed to be the weight-bearing structure of the spinal column. It is suitably designed for this task, given its block-like shape, with a generally flat superior and inferior surface.

The vertebral body is not a solid block of bone but a shell of cortical bone reinforced by trabeculae, which provides resistance to compressive forces. They also disperse the forces through into the intervertebral disks found between two adjacent vertebral bodies. The posterior or vertebral or neural arch consists of pedicles, laminae, articular processes, spinous processes, and transverse processes. The posterior arch is designed to serve more as a bony protection of the neural arch from compression and torsion than bearing weight.

The intervertebral disk. This is a collection of fibrocartilage rings that surround an amorphous nucleus pulposus. It has two principal functions. Number one, to separate two vertebral bodies, thereby increasing available motion. And to two, transmit the load from one vertebral body to the next. The size of the intervertebral disk is related to both the amount of motion and the magnitude of the loads that must be transmitted. As said before, it is composed of an annulus fibrosus and a nucleus pulposus. Its main design focuses on both stability and not sacrificing flexibility.

The function of the spine as a whole. The motions available to the spinal column are seen as flexion and extension in the sagittal plane, lateral flexion through the coronal plane, and rotation about the y-axis. These motions appear to occur independently of each other. However, at the level of the individual motion segment, these motions are often coupled motions.
Spinal segmental flexion. At the segment, we see anterior tilting and gliding of the superior vertebra on the vertebra below. This causes a widening of the intervertebral foramen and separation of the spinous processes. Tension in the supraspinous and interspinous ligaments resists separation of the spinous processes and thus limits the extent of flexion. Passive tension in the zygapophyseal joints and ligamentum flavum, posterior longitudinal ligament, posterior annulus fibrosis, and the back extensors also imposes controls on excessive flexion.

Spinal segmental extension. This is seen as posterior tilting and gliding of the superior vertebra over the vertebra below and causes narrowing of the individual foramen. This is also seen as an approximation of the spinous processes. The amount of motion available in extension is limited by bony contact of the spinous processes and passive tension in the zygapophyseal joint capsules, anterior fibres of the annulus fibrosis, anterior trunk muscles, and the anterior longitudinal ligament. The only ligament that limits extension is the anterior longitudinal ligament.

Spinal segmental lateral flexion. This is seen where the superior vertebra laterally tilts over the vertebra below. There is some degree of rotation and translation over the adjacent vertebra below. The annulus fibrosis is compressed on the concavity of the curve and stretched on the convexity of the curve.

Passive tension in the annulus fibres, intertransverse ligaments, and anterior and posterior trunk muscles on the convexity of the curve limit lateral flexion. The direction of rotation that accompanies lateral flexion differs slightly from region to region because of the orientation of the facets.

Spinal segmental rotation. The superior vertebra rotates axially over the vertebra below. It rotates and translates less than what is seen in lateral flexion. The annulus fibrosis fibres are slightly angulated and alternate in the direction in each layer. This creates a central compressive force as the disk is twisted. Passive tension in the annulus fibres, intertransverse ligaments, and anterior and posterior trunk muscles on the convexity of the curve limits rotation.
Regional variances of the spine and facet joint orientation. Each vertebral section has small differences to accommodate force. The vertebrae are depicted as follows and have favourable functions to deal with varying loads and shifts of the centre of gravity through each region. The angulation of the spinal facets varies between segments.

In the cervical region, you see the facets facing coronally, with a 45-degree superior-to-inferior tilt. In the thoracic spine region, you see a 40 to 60-degree lateral front coronal plain and a 30-degree superior-to-inferior tilt. In the lumbar spine region, it is a 45-degree lateral and sagittal orientation of the facets. The changing orientation of facets is suspected due to the change from mobility in the cervical spine to anchoring in the thoracic spine for the vital organs and weight and load bearing in the lumbar spine.

Posture. The key concepts of posture are as follows. Postural control is the ability to maintain the stability of the body and body segments in response to forces applied to the body in any direction. The base of support is the area bounded posteriorly by the heels and anteriorly by a line joining the tips of the toes. The centre of gravity is the line of gravitational force as it transmits down the spine to the base of support. Perturbation is any sudden change in conditions displacing the body posture from equilibrium.

The basic elements of postural control. These control the body's orientation in space. They maintain the body's centre of gravity over the base of support and stabilize the head concerning the vertical so that eye gaze is appropriately orientated. This requires the optimal function of intact central nervous, visual, and musculoskeletal systems.

Control depends on correct information from proprioceptors in the joint capsules, tendons, ligaments, and the soles of feet, a completely healthy vestibular system, and a balanced visual system. Posture analysis. For the anterior view there is quite a list of key landmarks to identify on the anterior view.

We always look at the level of the eyes; the level of the ears at the external auditory meatus; the facial features, in case of any hemiplegia, ptosis, or Bell's palsy; the AC joints, to see if they are level and orientated correctly; the manubrium sterni; the antecubital fossae; the ASIS, or Anterior-Superior Iliac Spine; the knee joint line, for any deviations of genu valgus or genu varum; the patellae, for any patella alta or baja, squinting, or divergent patellae; the medial arch of the foot, for any arch collapse or pronation of the foot; and angulation of the first rays, to see any spreading or foot leg length deformities.

On posterior view, key landmarks to identify in the posterior view are as follows. The external occipital protuberance; the external auditory meatus; the AC, spine of scapula on ectomorphic patient body types; the inferior angle of the scapula, to see for any whinging or protrusion of the scapula; any elbow joint lines or carrying angles; the Posterior-Superior Illiac Spine, notified by dimples above the buttock area; the gluteal folds; the popliteal fossa; the Achilles tendons, for any calcaneas valgus or varus.

On the lateral view, key landmarks to identify the natural view are as follows. An anterior or posterior head carriage; the C/T junction for Dowager's hump or Pottenger's saucers; the thoracic profile for hyper or hypo-kyphosis; the chest profile for pectus cavus or pectus carinatum; anterior or posterior pelvic tilt on the line between the Anterior-Superior Iliac Spine and the Posterior-Superior Iliac Spine levels; the gluteal profile; the knees, whether they are in semi flexed position for posterior pelvic tilt, or hyperextended or genu recurvatum position for a severe anterior pelvic tilt; and the foot profile for plantar flexion or heel lift.
General postural syndromes. Kyphosis. This refers to an abnormal increase in the normal posterior convexity of the thoracic spine. It may be compensation for an increase in lumbar spine lordosis, or as a result of poor postural habits or developmental, such as Sherman's disease, or in secondary infections, such as TB, or secondary developmental disorders or autoimmune disorders, such as ankylosing spondylitis.

A gibbus or humpback deformity can result due to vertebral fractures. These are significantly different, with a sharp angulation in the thoracic curvature, compared to a general thoracic convexity. A Dowager's hump is a common recognizable condition often found in postmenopausal women, especially if there have osteoporosis.

It is a common postural problem that is developed from the prolonged anterior head carriage and results in the collapse of the vertebral bodies anteriorly, increasing compression due to the lack of anterior support resulting in the hump. Here are some simple diagrams of general postural syndromes, especially around kyphosis.

Scoliosis. This is a condition that involves lateral flexion and rotation of the vertebrae in a coupled motion. The adolescent form, or idiopathic type, makes up 80% all scoliosis cases. These curves are defined as structural curves. They are named according to the direction of the convexity and the location of the curve.
It is due to asymmetrical growth and development, which causes wedging of the vertebral bodies. These commonly need surgical intervention or bracing. The second type of scoliosis is known as functional or non-structural scoliosis, which can be reversed if the cause of the curve is corrected and structural changes are not present. Examples of non-structural scoliosis are leg length inequality and/or muscle spasm.

The following pictures depict the types of scoliosis that can be seen, such as a single thoracic curve, a single lumbar curve, a single thoracolumbar curve, and a double lumbar and thoracic curve. Postural syndromes to consider in the athlete. Upper crossed syndrome.

This is signified by tightness of the upper trapezius and levator scapula on the dorsal side, which crosses with tightness of the pectoral muscles. Weakness of the deep cervical flexors ventrally crosses with weakness of the middle and lower trapezius. This pattern of imbalance creates joint dysfunction at the atlanto-occipital joint, or C4-C5 segment also, cervicothoracic joint, glenohumeral joint, and the T4-T5 segment. Specific postural changes are seen in upper crossed syndrome, including forward head posture, increased cervical lordosis and thoracic kyphosis, elevated and protracted shoulders, and rotation or abduction and wringing of the scapula.

Lower crossed syndrome. This is signified by the tightness of the thoracolumbar extensors on the dorsal side, which crosses with the hip flexor muscles, and weakness of the deep abdominal muscles ventrally, which crosses with the weakness of the gluteal muscles. This pattern of imbalance creates joint dysfunction, particularly at the L4 and L5 segments, L5 and S1 segments, the sacroiliac joint, and the hip joint.

Specific postural changes are seen in lower crossed syndrome, which includes anterior pelvic tilt, increased lumbar lordosis, lateral lumbar shift, lateral leg rotation, and knee hyperextension or genu recurvatum. If the lordosis is deep and short, then imbalance is predominantly in the pelvic muscles. If the lordosis is shallow and extends into the thoracic area, then imbalance predominates in the trunk muscles.

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Download English Transcript: Cervical Spine Injuries in Sport

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I am Ulrik Sandstrom, I am a sports chiropractor from Sheffield in the UK, working in sports chiropractic for over 20 years. I have worked in professional rugby for the past 10 years, so cervical spine injuries are certainly something I have seen quite a lot of. 

We will little bit at specific mechanisms of injuries and a lot has been researched about this. The general consensus now is that the specific mechanism of injury predicts very little of what we are going to do with the athlete. The speed of impact, the direction of impact, and whether there was a coup or contra-coup, certainly in terms of managing cervical spinal injuries, are of very little value. Only really in acute pain, or in acute management when you are looking for red flags, and possibly some prognostic value in the mechanism of injury, but again, the research jury is certainly out on that. 

Essentially, you treat what you assess, so you assess the player or the athlete in front of you, and, based on that assessment, findings, those assessment findings, you treat accordingly. That is much more important than knowing how they were hit, what direction they were hit from. So yes, there is some value in getting this information, but don't forget that the actual basis on which you determine what you treat, as long as you have ruled out red flags, is very much based around what you see in front of you. 

I am going to talk briefly about the Quebec Task Force Classification. I am not going to go into any detail because it is all out there. I have put a little reference down at the bottom here, as you can see. It is a great reference there; you can go and read up on the Quebec task force classification. 

There are two of them. There is the original classification as we have got it here, rating from zero to four, zero is no neck pain. You are not going to see a lot of those with impact in sport, but grade one (1) is neck complaints of pain, stiffness, and tenderness, but without any physical signs that you can elicit.

Grade two (2) is musculoskeletal signs with a neck complaint such as decreased range of movement and point tenderness. On the grade three (3) we now go into significant neurological signs, so USRM signs are now reduced, sensorimotor and reflexes. And grade four (4) is the more catastrophic event, so you now have very significant structural pathology, such as a fracture or dislocation. 

The modified Quebec Task Force Classification now considers sort of global sensitization, hypersensitivity. It considers sympathetic nervous system disturbances and psychological and post-traumatic stress. When we start looking at possibly concussion symptoms, then these become a lot more important. There is again a reference at the bottom here.

Briefly going through that, Grade 0 and Grade I are identical to the standard Quebec Task Force Classification. But as you can see in Grade 2, they now expanded Grade 2 to include IIA, IIB, and IIC, where IIA we now have sensory impairment, local cervicomechanical hyperalgesia, in Grade IIB, we now get psychological impairment, elevated psychological stresses as tested on some of our questionnaires. 

Grade IIC, increased joint positioning error, so these are the tests where you sometimes see people sitting with lasers on top of their heads, closing their eyes, turning their head, repossessing their neck again, and you measure the error of essentially proprioceptive input from the cervical spine. So Grade IIC, We are starting to see error and generalized hypersensitivity, and again, significant post-traumatic stress. Grade 3, the modified task force now again looking at, as we can see, sensory impairment here, psychological impairment, so similar to what we saw in the Grade IIC. 

I will talk briefly about the Canadian Cervical Spine or C-spine rule, essentially, when should we image cervical spine trauma? We should basically look at high risk factors. High risk factors are over 65 years of age, we may not see a lot of those in, certainly, elite sport, paraesthesia in the extremities is a high-risk factor, and also dangerous mechanisms. As you can see here, the dangerous mechanisms are put a little addition to the slide here are hyperflexion, we will see an example of that later in this presentation, and axial load, so essentially anything that hyperflexes the cervical spine, or any axial load here as a mechanism of injury. We need to seriously consider getting a radiographic examination. 

Again, low risk factors, if they have any of the following, again, we look at neck mobility, and most of the time we will choose to not take radiographs. But there is, a lot more information on this out there, but certainly cervical spine rule is one to be aware of. We will see examples later on when that was used in a real live athlete that I saw.

 Any acute cervical pain with traumatic event, always consider concussion. If the force was big enough to cause a neck injury, it may also have caused a concussion. We now know that the line between a whiplash injury and concussion, in terms of symptomatology, is very, very blurred indeed, and we now are starting to think that most concussion has a very, very significant cervical component to it, and they are the other way around, too. So certainly, be aware of checking for concussion symptoms in acute cervical pain. Don't just think, oh, this is the neck injury. Always consider, if there was a significant enough force, that it could have been, that they could be suffering concussion symptoms also.

 We saw in the cervical spine, the Quebec Task Force, that some of those symptoms in the modified version was tight taking into account symptoms that could be attributed to concussion also. Classic example here from a rugby final that we were playing in. You can see Number 10, gets tackled here, quite a significant injury, and he  goes down and suffers concussion, as well as a whiplash injury. So always consider concussion in acute traumatic cervical pain.

In terms of management, pain management, reassurance is big in acute cervical pain. People, even elite athletes, often think that they are making a fragile structure. If you can reassure them that they will get better, again, we now know increasingly how important that is for recovery. Consider analgesia, consider taping, spinal manipulation, possibly consider low force or Activator to begin with, very much, again, to athlete tolerance. Our goal is to restore joint function because we know improving joint function improves pain modulation. 

Spinal manipulation, mobilization, consider again into least painful range, so if they are very restricted in one direction, consider adjusting them the other way. Again, as before, consider using Activator. We will see briefly later on, those of you who have heard me speak before will know I am a very big fan of functional muscle testing, and I will very often based my initial adjustment decision and direction around what I find on muscle tests. We have got a couple on that later on, as well. 

Soft tissue work, whatever your preferred acronym is, we have dry needling therapy, instrument- assisted soft tissue manipulation, massage, active release techniques. Again, whatever's in your toolbox in order to improve soft tissue function can be relevant here. We know that things such as cupping is becoming more and more used, and I have seen and also personally experienced very good effects with that, too. And then, of course, rehab. The acute cervical pain rehab, I getting back to function is active mainly based around range of movement stuff rather than necessarily strengthening at the acute stage. 

Radicular pain, always check for sensorimotor and reflex changes. Consider imaging or surgical evaluation if an athlete is either non-responsive to your treatment, or finding that there are unremitting and, obviously, if you have down going SMR findings, then a consideration for imaging evaluation should certainly be done. Try and find the source of neural irritation.

Remember double crush, so you can have a double crush injury, they could have an irritation of that neural pathway at any part of the pathway through the caudal tunnel, the ulnar nerve behind the elbow. 

Couple of tests here that are useful, doorbell test is one I use a lot. Literally get in front of the IVF, palpate through pressing. It will be tender, but of course what you're looking for is, does it reproduce the peripheral either upper arm pain, axillary pain, lower arm pain where the athlete is complaining of. The arm squeeze test is now being shown as one of the most valid and sensitive tests out there. I put a little link down at the bottom here for you to go and check out. If you Google "arm squeeze test" on YouTube, you will find ways to perform that. I use that test a lot now, and it is a very, very valid test to distinguish radicular arm pain from musculoskeletal arm pain. Neural tension test, again, you will find those out there. You should be aware of those already, but there's plenty of work out there for you to go and check out.

A stinger is something we see a lot of in rugby or any sort of tackle or impact-based sports. The guy getting the stinger here is not-- although the facial expression on this guy is not great, the guy who is getting the stinger is the guy who's tackling him. So, it is a traction injury of the lower cervical nerve routes and/or brachial plexus, usually caused by sudden depression of the shoulder girdle, i.e., you go in for a tackle, your shoulder gets depressed, you may even be forced contralateral, lateral flexion of the cervical spine, again, essentially tractioning through the brachial plexus. Usually associated with paraesthesia, pain, sometime neural deficit as well. 

This is where you will often see a player in an impact sport getting tackled, they drop to the floor, you will get the medical team coming in, and you will often see them immediately testing muscle strength, and essentially checking for neural integrity after a stinger. It can last from seconds to several months. They are often fragile for quite a long time, so once you've had one stinger and that neural sensitivity, it often takes a lot less impact for them to experience another stinger, so be aware of that. 

Management, cervical and thoracic adjusting, soft tissue release, particularly through pec minor and scalene muscles overlying the brachial plexus. Don't just go in adjusting the spine and nerve roots. Have a very good look at the soft tissues on top of the brachial plexus. Releasing in there will often have great effects on your athletes. 

Neurodynamic mobilization, you can do that with instruments as well. Inhibition, kinesiology taping of pec minor. Very briefly, the way that I do that is I will stretch the pec minor out as much as I can, and I will lay kinesiology tape along from the tip of the shoulder along the clavicle with zero tension on. Zero tension, and make sure you get it off the backing tape, lay it down with full stretch so that as you release the muscle into neutral, you should get little convolutions in the tape. When you get in convolutions, that essentially is an inhibition taping, and it'll reduce muscle tone. It is fantastic for neuron pain because it just relaxes that pec miner down and gives good release. 

Look at breathing patterns. If people got very poor diaphragmatic breathing and they are breathing from a lot of their accessory muscles, that will keep irritating that brachial plexus, too, so one to look at. Again, anterior head carriage, forward posture, will be a factor in recovery from a stinger, too. 

This is myotomal testing. If I find a weak muscle on particularly shoulder girdle stabilization, I will try and see if any cervical mobility or cervical movement will change my muscle tests. So very often We will find that shoulder flexion or shoulder abduction is inhibited in a cervical spine injury, and if rotation to one side makes that muscle test strong, that's the way that I will tend to adjust them. Again, the level I will find with motion palpation usually, but you often find if you adjust it that way, test after your adjustment, and you will often find immediately change in strength there. 

Anterior translation is another one that often you see, if you get particularly SMR findings. If you find that someone has, say, a weak wrist extension, and you then do anterior translation of the spine and you find an improvement in strength, it is often to me an indication that you have a discal compromise. As you translate forward, you essentially open the IVF behind the disc, creating more room for the nerve, and therefore more neural firing. 

We are going to finish with a real-life story. I have written consent from our player, who is the athlete coming in from the right here. Tom Croft, wearing number six, gets tackled in a game about five, six years ago. Let us watch the video again. Tom Crofty comes off the back of the scrum just here and goes out and tackles the number eight. Number eights are normally pretty big in rugby, and he somehow manages to come across. You can see in terms of the cervical spine rule, apart from the fact that scrum half knees him in the face afterwards, in terms of the cervical spine rule, we pretty much got the two risk factors here. We got a hyperflexion injury and an axial compression. 

Tom drops down. Immediately, the physios and the doctor are on the scene. Rugby physios are incredibly quick at getting to players who go down. Players in rugby generally are shouting swear words at this stage, saying, I am fine, I can get up, they will often claim they can play on, but they certainly want to walk off. If nothing else, they hate being spinal boarded off. 

However, the medical team basically suggested that he failed C-spine tests. Significant point tenderness of C-spine, so he was immobilized, ended up at a hospital where two years earlier, after a game, he had a glenoid fracture. We must hand over control to the hospital department, and are not allowed in. The hospital department examined him, took the necessary X-rays, reported back, and said, X-rays are clear. 

No fracture found, returned to the team in a sling. He came in to see me the next morning, and I assisted him. He had shoulder-tip pain and a little bit of paraesthesia but nothing presented but a very stiff neck. I did a full SRM, full workup. Cervical compression was negative, upper limb reflexes, sensation, muscle power was normal, pretty sensitive, the doorbell test suggested that there was subneural tension in there.  I diagnosed a stinger, particularly with a view of knowing that his X-rays were clear. 

Then he didn't get any better, and two days later we decide, well, I cannot do that but I adjusted his C- T junction very gently. He was pretty tight, so I wanted a little bit of stimulation in there, but I adjusted his C-T junction, I did a lot of soft tissue release first. He felt quite a bit better after my treatment, but two days later was not improving overall. So medical team decided, to get a scan done, and as you can see this is a pretty scary scenario. He had an unstable fracture at C6-C7, including a true subluxation, not in the chiropractic word. 

This is his MR finding, and you can see he has a significant structural deficits around, including the disc, significant core pressure, where you can see the fractures through the pedicle just here. And this is Tom Crofty post-surgery. The first thing we thought was, well, how on earth did they miss this at the hospital? How did they miss a spinal fracture when he was X-ray at the hospital immediately after the injury? We requested the X-rays which were taken, and the X-rays were, indeed, perfectly clear of his right shoulder. 

They had not taken any cervical spine X-rays because when Tom Crofty came in, probably linked to the fact that he already had a history of shoulder problems two years earlier, they neglected the fact that he had  hit his neck, and the neck was the issue when our team took over. So somewhere along the lines, as he presented to the radiographer, they decided he is complaining of shoulder pain, so we will X-ray his shoulder. When the report came back to us, it was just, yes, radiographs are clear, nothing to report. 

There are a couple of things that you can learn from this. Never assume and always check, always request radiographs but keep good dialogue with the medical team. I had to do a report on why I was manipulating someone who was later found out to have an unstable fracture of the cervical spine. Luckily, my decision at the time was to go very gentle and to do very light stimulation, mainly because of soreness and tenderness. There was still nothing, and in hindsight, reviewing the case, there was nothing on my initial examination to suggest that he had a catastrophic injury at all. 

The conclusion to this, and another learning curve, is that this is Tom Crofty first game back. This is our trial line just behind him here, and we have Danny Care, number nine, scrum half, the same team that we were playing when Tom Crofty got his injury.

This is about nine months later after cervical fusion, and Danny Care sees the try line, jumps over to try and score and Tom Croft decides to tackle him to try and prevent this try being scored, and with his head.

The medical team sitting on the bench, saw this happen on the big screen, and thought, what is he doing? I guess it is a way of testing your spinal, and your cervicospinal fusion. The great news is that the outcome of this tackle was the try was not given, it was a try saving tackle from Tom Croft in his first game back after a catastrophic cervical spine injury. 

In closing, make sure that you never assume, check and always double-check and make sure that athletes get their diagnosis and the correct radiographs. The other lesson you can learn from this, if you ever want to tackle someone with your head, go for the nine rather than the eight, because the nine is considerably lighter and easier to tackle with your head. You can see Tom Crofty here looking pretty happy and not lying on a spinal board, so it was a very effective way of testing his cervicospinal fusion.

[END]

Download English Transcript: ICSC07_Section 4_1. Running Physiology_Reviewed

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Anatomy and Biomechanics of the Spine and the Pelvis

The spine, or vertebral column, is broadly divided into five regions: the cervical spine, the thoracic spine, the lumbar spine, the sacrum, and the coccyx. Though these regions have similar morphology, they have variable biomechanical characteristics, giving rise to the spine's S-shaped curvature. The spinal column forms the central axis of weight-bearing and supports the head as well as transfers the weight of the trunk and abdomen to the legs. The spine provides structure and flexibility to the body. Its unique jointed structure of the spine allows rotation and bending. The spine, plus the rib cage in the thoracic region provides attachment site for multiple muscles.

The cervical spine comprises of 7 vertebrae. It is divided into 2 major segments. Cephalad, occiput and the top 2 vertebrae, the atlas (C1) and the axis (C2), form the craniocervical junction (CCJ). Caudally, C3 to C7, comprise the sub-axial spine, together supports the weight of the cranium and motion. The cervical vertebrae, as a group, produce a lordotic curve.

 The thoracic spine comprises of 12 vertebrae. Upper Thoracic Region (T1-T4) is closer to the cervical spine and has similarities in movement and function of the cervical spine. It provides support to the upper body and allows for the attachment of the rib cage. Mid Thoracic Region (T5-T8) makes up the central part of the thoracic spine. It is more rigid and less mobile compared to the upper and lower regions. It provides structural support and stability, protecting vital organs such as the heart and lungs. Lower Thoracic Region (T9-T12) makes up the lower thoracic spine as it transitions into the lumbar spine. It is more flexible compared to the mid thoracic region, allowing for a greater range of motion, and plays a crucial role in weight-bearing and movement.

The lumbar spine consists of five vertebrae, labelled L1 to L5. These vertebrae are larger than those in the cervical and thoracic regions to support the weight of the upper body and allow for movement and flexibility. The vertebral bodies are thick, cylindrical front portion that bears weight. The vertebral arches are rostral, forming the vertebral foramen (spinal canal) where the spinal cord passes through. The spinous processes project off the back of each vertebra, providing attachment points for muscles and ligaments. The transverse processes are laterally situated horizontal projections, serving as additional muscle and ligament attachment points.

Except at the craniocervical junction there are intervertebral discs between each vertebra throughout the spine, providing cushioning and support. Intervertebral discs are cartilaginous structures between adjacent vertebrae composed of annulus fibrosus and nucleus pulposus. The discs comprise about 25% of the length of the vertebral column.

The sacrum and the coccyx consist of five fused vertebrae each. In some cases, the coccyx may be one of four vertebrae. There are junctions between the broad regions of the spine; the cervicothoracic, the thoracolumbar and the lumbosacral junctions. Spinal junctions are frequent sites for degenerative changes over the long term resulting in stiffness and loss of motion.  

The spine, as a complete structure, can undergo axial, lateral, and sagittal rotations and axial, lateral, anterior, and posterior translations.

Pelvis is responsible for supporting upper body weight being defined as the middle part of the human body between the lumbar region of the abdomen superiorly and thighs inferiorly. The human pelvis is composed of the bony pelvis, the pelvic cavity, the pelvic floor, and the perineum. In addition to carrying upper body weight, this multi-surfaced girdle can transfer upper body weight to the lower limbs and act as attachment points for lower limb and trunk muscles.

Spinal and Pelvic Ligaments

The spinal ligaments serve to protect neural structures by restricting the motion of functional spinal units. The ligaments also absorb energy during high-speed and potentially injurious motions. The spinal ligaments are primarily collagenous, except for the ligamentum flavum, which is primarily comprised of elastin. The anterior longitudinal ligament originates at the base of the occiput and extends the entire length of the spine into the sacral region, along the anterior aspect of the spine. The fibres of the anterior longitudinal ligament firmly attach to each other as well as to the entire vertebral disc. 

The posterior longitudinal ligament also extends the length of the spine along the posterior aspect of each vertebral body and anterior to the spinal cord. The ligamentum flavum originates bilaterally on the anterior inferior aspect of the laminar portion of the superior vertebral body and inserts into the posterior superior aspect of the lamina of the inferior vertebrae. The intertransverse ligaments and interspinous ligaments join the transverse and spinous processes of adjacent vertebrae. The supraspinous ligament originates as the ligamentum nuchae of the neck and extends the length of the spine posterior to the interspinous ligament while attaching firmly to the tip of each spinous process. The capsule ligaments surround each facet joint.

The key ligaments of the pelvis are the sacrotuberous, sacrospinous, and iliolumbar ligaments that are present in both sexes. Further ligaments include the anterior sacroiliac, anterior sacrococcygeal, posterior sacroiliac, posterior sacrococcygeal, and pectineal ligaments. 

Mechanically, ligaments behave like other soft tissues in the body. They are viscoelastic in nature with non-linear functional elastic responses to loading. Their mechanical response has been characterised predominantly ex-vivo, and little is known about their in vivo mechanical environment. In general, it is believed that spinal ligaments do not enjoy the same margin of safety as bones do, as they can operate under conditions relatively close to their failure strengths. This belief is based on combining the ex-vivo mechanical behaviours of individual ligaments and functional spinal units with motion, radiographs, and mathematical models of the spine. 

Failure load is the amount of force at which a ligament or the functional spinal unit fails. The failure loads of spinal ligaments vary depending on the spinal region, and the specific ligament. Anterior Longitudinal Ligament (ALL) failure load is approximately 2500 N, posterior longitudinal ligament (PLL) failure load is approximately 400-600 N, ligamentum flavum failure load is approximately 300-500 N, interspinous ligament failure load is approximately 300 N, supraspinous ligament failure load is approximately 400 N and the capsular ligament (facet joint capsules) failure load is approximately 700 N.

Failure loads of FSUs are influenced by various factors, including the specific spinal segment (e.g., cervical, thoracic, lumbar), age, and condition of the spine. General failure loads for the cervical FSUs are approximately 1000-1500 N, 2000-3000 N for thoracic FSUs and 5000-6000 N for lumbar FSUs.

The mechanical load on the spinal functional units (FSUs) and ligaments during running varies based on intrinsic and extrinsic factors such as running speed, technique, individual biomechanics, sneakers and surface. When running, the spine experiences a combination of compressive, tensile, and shear forces. These forces are transmitted through the vertebrae, intervertebral discs, and associated ligaments. The lumbar spine, in particular, is subjected to significant compressive forces during running. These forces can be 3 to 5 times of the body weight, depending on running speed and form. For an individual weighing 70 kg (approximately 686 N), this translates to compressive forces of 2058 to 3430 N.

Shear forces, which act parallel to the plane of the vertebral bodies, are also present but are generally lower in magnitude compared to compressive forces. These forces can be influenced by running mechanics and the incline of the running surface.

Ligaments provide stability and limit excessive movement between vertebrae. During running, these ligaments experience dynamic loading as the spine flexes, extends, and rotates. ALL and PLL experience tensile forces as they resist the anterior-posterior motion of the vertebrae. The forces can be substantial but typically remain well below their failure thresholds of 100-300 N. Ligamentum flavum stretches and recoils with spinal motion. Forces in the ligamentum flavum are generally lower compared to the ALL and PLL, estimated to be in the range of 50-150 N. Interspinous and supraspinous ligaments connect the spinous processes of adjacent vertebrae, experience tensile forces during flexion and extension. The forces are variable but generally range between 100-200 N.

The mechanical load on the pelvis and its associated ligaments during running is substantial due to the forces transmitted through the lower extremities and the need to stabilize the body. During running, the pelvis experiences both compressive and shear forces due to the impact of foot strikes and the dynamic movement of the lower limbs. The compressive forces can reach up to 3-5 times body weight while the shear forces are generally lower than compressive forces but significant due to lateral and rotational movements.

During weight bearing posture as well as in running the pelvic ligaments help stabilize the pelvis and transfer loads between the spine and lower limbs. Sacroiliac ligaments are crucial for maintaining pelvic stability and can endure substantial tensile loads during dynamic activities like running. Vleeming et al. (1995) highlight the importance of these ligaments in load transfer, though specific numerical values for failure loads are less commonly detailed in literature focused on dynamic activities like running. Iliolumbar ligament similar to the sacroiliac ligaments, stabilizes the connection between the lumbar spine and the pelvis. Tensile forces in the iliolumbar ligament during running are significant, though precise values during running are not often specified. Pubic symphysis absorbs and distributes forces from the legs through the pelvis. It can endure significant compressive and shear forces during activities like running.

If a load is applied to a functional spinal unit or a multi-level spine unit, the unit first displaces from a neutral position to a position where an appreciable resistance is first encountered. The initial lax region of the motion is termed the neutral zone. The presence of a neutral zone allows the spine to undergo relatively large motions with very little muscular effort. 

Enlargement of a neutral zone can indicate an abnormal structural change and be a cause for concern. A region of stiffening next is encountered, termed the elastic zone. The displacement at the largest applied load or at the limit of motion for an activity is termed the range of motion. 

Spine, as a structure, displays viscoelastic characteristics due to the viscoelastic nature of its constituents. The relative kinematic terms of the study of spinal cord kinematics are flexion, extension, lateral bending, and axial rotation. Flexion refers to bending forward above an axis perpendicular to the sagittal plane. 

Extension refers to bending backward about that axis. Together, flexion and extension are referred to as sagittal bending. Lateral bending refers to bending either side and can be either left or right lateral bending. Axial torsion refers to turning to either left or right. The determination of in vivo mechanical loading and motion is perhaps the most challenging aspect of biomechanics, especially for the spine, a structure with complex motion patterns. 

Lumbar Intervertebral Discs

The vertebral bodies are connected and kept separated by the intervertebral disks. The disc is composed of the annulus fibrosus and the nucleus pulposus and is firmly joined with the end plates of vertebral bodies around the outer periphery of the annulus. 

The end plates are composed of hyaline cartilage. Vascular channels within the vertebral bodies have been observed to run directly at the end plates, representing the predominant nutrient source for the adult disc cells. Some blood vessels approach the annulus and the periphery but do not penetrate. The end plates undergo progressive calcification with age, which impedes the nutrient source and contributes to the progressive degeneration of the disc throughout adulthood. 

The nucleus pulposus is located poster-centrally in the disc, where in the lumbar region, it fills 30% to 50% of the cross-sectional area of the disk. The normal nucleus contains almost exclusively type 2 collagen fibres in an aqueous gel rich with proteoglycans. The collagen molecules in the nucleus have also been found to have proteoglycan molecules bound to their ends. 

The water content in the normal nucleus of human lumbar discs decreases from about 90% of its total volume during the first year of life to 70% in the 80th year and beyond. The annulus fibrosus is composed of concentric layers of collagen fibre bundles in a helicoid manner. Observations using scanning electron microscopy have shown the fibres in the inner third of the annulus to interconnect with the cartilaginous end plate. 

The fibres in the outer portion are firmly bound to the epiphyseal ring of the vertebral body. The disc fibres have been found to be almost exclusively composed of type 1 collagen in the outer portion and gradually change to a 40% type 1 and 60% type 2 mixture in the inner portions. The annulus has a laminate structure. The fibre orientations alternate from layer to layer, with the fibres generally orientated at an angle of approximately plus or minus 30 degrees with respect to the horizontal plane. Specifically, the fibre orientations change from about plus or minus 31 degrees in the outer annulus to plus or minus 22 degrees in the inner annulus. 

The disc is more morphologically structured so as to be predisposed to injury at the sight of high stress. Disc cells are poorly serviced with nutrients—a service that only gets worse with age. Injury or degeneration decreases the functional ability of the disc to transmit body forces through hydrostatic pressure, which, in turn, decreases the ability of the cells to maintain the extracellular matrix. 

Intradiscal pressure (IDP) is a measure of the pressure within the intervertebral discs of the spine, which can vary significantly with different postures and activities. Understanding these pressures, particularly in the L3-L4 disc, is crucial for assessing the biomechanical impact of various movements and for developing guidelines to prevent disc injury. The intradiscal pressures for L3-L4 disc during various movement patterns are as follows; Standing posture is approximately 0.5 MPa, sitting (relaxed posture) is approximately 0.83 MPa, sitting (with forward lean) is approximately 1.1 MPa, lifting (straight back, bent knees) is approximately 1.7 MPa, lifting (bent back, straight legs) is approximately 2.3 MPa, lying down is approximately 0.1 MPa, flexion (forward bending) is approximately 1.2 MPa and extension (backward bending) is approximately 0.6 MPa

Though direct intradiscal pressure measurements during running are difficult to attain and are rare Wilke et al, Rohlmann et al, and Brinckmann et al have documented the following measurements of the lumbar IVDs during daily activities of dynamic loading; 1.5-3.0 MPa, 2.5 MPa, and 2.3 MPa.

Throughout the day, the vertebral column is subjected to compressive stress as well as other types of loading by gravity, changes in position, muscle activity, external forces, and external work. The fluid pressure within the nucleus pulposus is related to the axial compression applied to the disk. When the compressive load exceeds the interstitial osmotic pressure of the tissues of the disc, water is extruded through the disc wall. 

The result is a loss in disc height and, thus, a loss in total body height. The gelatinous nature of the nucleus allows it to imbibe fluid and regain its original size when axial compression is minimized. During the day, when a person is usually under the constant force of gravity and muscular activity, the intervertebral discs lose as much as an inch in height, which is about 2.5 to 3 centimetres. However, at night, while a person is recumbent, that height is restored. 

This shrinkage has been used as a measure of the effect of the load on the spine. Consequently, the observed changes in height can be considered to reflect the magnitude of the vertebral column loading. It has been asserted that greater losses in height occur when dynamic, rather than static, loading is involved and that dynamic loads on the spine result in a faster rate of shrinkage. Running studies using force plate gait analysis have shown a marked increase in the ground reaction force as compared to walking. 

Biomechanics of Running

Running is a matter of bipedal gait, which represents a natural progression from walking. The progression from walk to run occurs as a strategy to conserve energy. Increasing velocity comes at an energetic cost. Running typically commences at a speed of 2.1 to 2.2 meters per second, which is about 4.92 miles per hour or 7.91 kilometres per hour. 

As a hallmark, the running gait replaces the double support phase of walking with a double float phase where there is no contact with the ground. There are a series of single-leg and double-float periods. The running stand phase is limited to 40% or less of the gait cycle. 

Vertebral column height decreases throughout the course of the day. This decrease is the result of a loss of fluid from the integral table discs due to compressive loading. When the load changes during the day as a result of varying physical activities, the rate of disc shrinkage changes in relation to those activities. 

One study shows a correlation between long-distance running and an increase in the loss of vertebral column height. 30 elite male runners, ages 17 to 29, participated in the study. Subjects' vertebral column heights were measured in the morning upon waking, in the afternoon prior to running 9 miles, which is about 14.48 kilometres, and then immediately following the run. The findings revealed that the spinal column height was significantly less following the run. More interestingly there was a significant greater amount of height loss during one hour of running than during 7.5 hours of relatively static activities.

During running, the force generated at the point of heel strike has been shown to be three times that of walking. This means that significant compressive forces are being transmitted to the spine. The intervertebral disc is of great mechanical and functional importance. A fundamental understanding of this structure and biomechanics is necessary in order to hypothesise a relationship between physical activity and intervertebral disc height. The intervertebral discs comprise over one-fourth the length of the vertebral column. 

Intervertebral discs are fibrocartilaginous articulations designed for strength, and together with their adjoining vertebral bodies, they function as synthesis joints. They serve as a cushion between vertebral bodies to store energy and distribute loads. Each disc is composed of three distinct parts: the nucleus pulposus, the annulus fibrosus, and cartilaginous end plates. At the centre of the disc is the nucleus pulposus, which is encased above and below by the cartilaginous end plates and encircled by the annulus fibrosus. 

The nucleus pulposus is composed of a loose network of fibres in a mucopolysaccharide gel, which contains from 70% to 90% water. It is essentially avascular and not innervated. Nutrients reach the nucleus by diffusion from the blood vessels that lie around the periphery of the annulus fibrosus and from the vascular cavities in the central portion of the cartilaginous end plates. 

The nucleus pulposus allows for movement in the spine by deforming under compression, tilting and twisting to alter the shape of the disc, and circling the highly organised layers of collagen fibres that comprise the annulus fibrosus. The annulus contains essentially the same material as the nucleus, although its water content is greatly reduced. And its fibre content has greatly increased. 

The fibres are orientated obliquely with each layer, about 60% to 70% vertical, with adjacent layers running in alternating directions. This highly organised arrangement and substantial fibre content are what give the annulus fibrosus its great strength, thus allowing it to function as a load-bearing structure. The annulus and the nucleus work together to distribute forces evenly over the vertebral end plates.

The vertebral column is a strong yet flexible shaft that provides support for the body weight at the bases for locomotion and protection of the spinal cord and its nerve roots. Intervertebral discs are interposed between adjacent services of the vertebral bodies and provide the strongest attachment between the vertebrae. The principal functions of the vertebral discs are to allow movement between vertebral bodies, transmit forces evenly from one vertebral body to the next, and absorb and store energy. 

Running is similar to walking in terms of locomotive activity. However, there are key differences. Having the ability to walk does not mean that the individual has the ability to run. Running requires greater balance, greater muscle strength, and greater joint range of movement.

There is a need for greater balance because the double-sport period present in walking is not present when running. There is also the addition of a double float period during running which both feet are off the ground. The amount of time that the runner spends in a float increases as the runner increases in speed. 

The muscles must produce greater energy to elevate the head, arms, and trunk higher in comparison to normal walking. The muscles and joints must also be able to absorb an increased amount of energy to control the weight of the head, the arms, and the trunk. During the running the ground reaction force at the centre of pressure has been shown to increase to 250% of the body weight. 

The joint motion of the running gait cycle, at the beginning of the stance phase, the hip is in about 50 degrees of flexion at heel strike, continuing to extend during the rest of the stance phase. It reaches 10 degrees of hyperextension after toe off. The hip flexes to 55 degrees of flexion in the late swing phase. Before the end of the swing phase, the hip extends to 50 degrees to prepare for the heel strike. The knee flexes to about 40 degrees as the heel strikes, then flexes to 60 degrees during the loading phase. 

The knee begins to extend after this and reaches 40 degrees of flexion just before the swing phase, and during the initial part of the float period, the knee flexes to reach maximal flexion of 125 degrees during the mid-swing. The knee then prepares for the heel strike by extending to 40 degrees. The ankle is in about 10 degrees of dorsiflexion when the heel strikes and then dorsiflexes rapidly to 25 degrees.  Plantar flexion happens almost immediately, continuing throughout the rest of the standing phase of running and as it enters the swing phase. Plantar flexion reaches a maximum of 25 degrees in the first few seconds of the swing phase. The ankle then dorsiflexes throughout the swing phase to 10 degrees, preparing for the heel to strike. The lower limb medially rotates during the swing phase, continuing to medially rotate at heel strike. The foot pronates at heel strike. Lateral rotation of the lower limb, stance leg begins as the swing leg passes by the stance leg in mid-stance position. 

Lower extremity muscle activity during running: gluteus maximus and gluteus Medius are both active at the beginning of the stance phase and also at the end of the swing phase. Tensor fasciae latae is active from the beginning of stance and also at the end of the swing phase; it is also active between early and mid-swing. 

Adductor magnus is active for about 25% of the cycle, from late stance to the early part of the swing phase. Iliopsoas activity occurs during the swing phase for 35–60% of the cycle. Quadriceps work in an eccentric manner for the initial 10% of the stance phase.  The role of the quadriceps muscle is to control knee flexion as the knee goes through rapid flexion. It stops being active after the first part of the stance phase. There is then no activity until the last 20% of the swing phase. 

At this point, it becomes concentric in behaviour, so it can extend the knee to prepare for a heel strike. Medial hamstrings become active at the beginning of the stance phase, which is 18 to 28%. They are also active throughout much of the swing phase, which is 40% to 60% of the initial swing. Then, in the last 20% of the swing, they act to extend the hip and control the knee through concentric contraction. In late swing, the hamstrings act eccentrically to control knee extension and take the hip into extension again. 

Gastrocnemius muscle activity starts just after loading at heel strike, remaining active up until 15% of the gait cycle. It then restarts its activity in the last 15% of the swing phase to balance interior muscle activity through both stance and swing phases in running. It is active for about 73% of the cycle. Its activity is mainly concentric or isometric, enabling the foot to clear the sport phase during the swing phase of the running gait. 

Elastic sport strategy is described as a mechanism for transferring force from the lower control zone to the upper control zone and back again. In runners, the diagonal elastic mechanism is utilized. This is produced by a constant diagonal stretch and release that is enabled by the body's counterrotation. 

The force continually flows up and down these force pathways. The pattern of force distribution prevents force from being concentrated in one area but allows a wide distribution of force throughout the body. At this point, it is only logical to say that it is crucial to have a well-functioning central core area to allow this pattern of force distribution to take place efficiently.  The kinetic chain can be described as a series of movements that make up a larger movement. Running involves a complex sequence of coordinated movements primarily utilizing the lower body, core, and to some extent, the upper body for balance and propulsion. Here are the main types of movements and muscle actions involved in running:

Lower Body Movements

1. Hip Flexion and Extension:
• Flexion: Bringing the thigh forward, primarily using the hip flexors such as the iliopsoas and rectus femoris.
• Extension: Driving the thigh backward, primarily using the gluteus maximus and hamstrings.
2. Knee Flexion and Extension:
• Flexion: Bending the knee during the swing phase, involving the hamstrings.
• Extension: Straightening the knee during the stance phase, involving the quadriceps.
3. Ankle Dorsiflexion and Plantarflexion:
• Dorsiflexion: Lifting the toes up towards the shin, involving the tibialis anterior.
• Plantarflexion: Pushing the foot down (toe-off), involving the gastrocnemius and soleus.
4. Foot Pronation and Supination:
• Pronation: Rolling the foot inward to absorb shock.
• Supination: Rolling the foot outward to stabilize and push off.

Core Movements

1. Trunk Rotation:
• Rotation of the torso, aiding in balance and transferring momentum. This involves the oblique muscles and the transverse abdominis.
2. Lateral Flexion:
• Side-to-side movement to maintain balance, involving the oblique muscles and quadratus lumborum.
3. Stabilization:
• Core muscles, including the rectus abdominis, obliques, and erector spinae, work to stabilize the spine and pelvis.

Upper Body Movements

1. Arm Swing:
• Forward and backward motion of the arms, which helps with balance and propulsion. This involves the deltoids, biceps, and triceps.

Phases of Running Gait Cycle

1. Stance Phase:
• Initial Contact: Heel (or midfoot/forefoot) strikes the ground.
• Midstance: The body weight moves over the support leg.
• Toe-Off: The foot pushes off the ground.
2. Swing Phase:
• Initial Swing: The leg lifts off the ground, moving forward.
• Mid swing: The leg moves directly under the body.
• Terminal Swing: The leg prepares for initial contact again.

 

Key Muscles Involved

• Gluteus Maximus: Hip extension
• Hamstrings: Knee flexion and hip extension
• Quadriceps: Knee extension
• Calf Muscles (Gastrocnemius and Soleus): Plantarflexion
• Hip Flexors (Iliopsoas and Rectus Femoris): Hip flexion
• Tibialis Anterior: Dorsiflexion
• Core Muscles (Rectus Abdominis, Obliques, Transverse Abdominis, Erector Spinae): Stabilization and rotation
• Upper Body Muscles (Deltoids, Biceps, Triceps): Arm swing

Coordination and Efficiency

Efficient running involves the coordinated action of these muscle groups and unrestricted movements of the related skeletal articulations to minimize energy expenditure and reduce the risk of injury. Proper form and technique are crucial for optimizing performance and maintaining the health of joints and muscles involved in running. Understanding these movements can help in designing effective training and rehabilitation programs, as well as improving running form to enhance performance and prevent injuries. The rotation is produced at the spine and is often referred to as the spinal engine. This is also linked to the running economy. The rotation enables the spinal forces to be dissipated as the foot hits the ground. Runners may complain of a feeling of restriction in their hamstrings or even their shoulders. However, when examined, it may be found that there is actually a limitation in the rotation of the pelvis causing the problem. 

The motion will be altered, and a compensational pattern will develop should there be a dysfunctional unit within the kinetic chain. The alteration and the compensation may result in a loss of energy and a reduction in performance, and that would potentially be a cause of developing an injury. Spinal engine theory, or the perspective of human locomotion, was developed by Dr. Serge Gracovetsky, a professor who prioritises the observation and analysis of thoracolumbar pelvic biomechanics. 

This theory holds that the human body design is a fundamental biomechanical couple motion mechanism that serves as the drive for human ambulation. The spinal engine theory also assigns a supportive functional role to the lower extremities, in keeping with the theory of human evolution. Dr. Serge considered the legs as instruments of expression and extensions of the spinal engine. 

Coupled motion is a second plane of motion that occurs within a joint system, part and parcel of the primary motion. Two or more motions are considered coupled when it is not possible to produce one motion without inducing the second motion. Spinal coupling is due to the morphological shape of the facet joint surfaces, which connect the ligaments and spinal curvatures. For example, in the cervical and thoracic spines, left vertebral rotation in the transverse plane is coupled with left vertebral lateral flexion in the frontal plate.  Lumbar lateral flexion in the frontal plane is coupled with contra-directional vertebral rotation. Right-lumbar lateral flexion is coupled with left-lumbar rotation. Though the cervical spine coupled motion studies show consistency and agreed upon the thoracic and the lumbar spine coupled motions do not.

The contra-directional coupled motion patterns of the various regions of the spine evolved for a reason to form their function. The opposing directions of the coupled motion are synergistic. It is the lumbar lateral flexion-rotation coupling that serves as the spinal engine. 

The drive train—right lateral lumbar flexion—will drive the rotation of the lumbar spine and the pelvis, and vice versa. In this specific mechanism, during right-legged weight bearing, the lumbar spine is pulled into the right side bending by the multifidus, longissimus, iliocostalis, and thoracolumbar fascia. This action counter-rotates the pelvis as the sacrum is forced into left-side bending and right rotation and vice versa, respectively, to the other side. The induced lumbar rotation effectively stores elastic energy in the spinal ligaments and annulus fibrosus of the intervertebral discs. 

It is the return of that energy that drives the gate. In order to return the energy, the spine must be stabilised from above; this is accomplished via contralateral arm swing and torso rotation obtained from the contralateral gluteus maximus and latissimus involvement. The coupling patterns of the spine have evolved to facilitate the return of this force.  The counter rotation is obtained from the spine and not from the legs. The legs do not apply counter torque to the ground. The counter torque must be provided by the structures above the pelvis. Now consider the biomechanical effect of inadequate arm swing, poor spinal mobility, poor hip mobility, degenerative disc disease, or ligamentous injury on a person's walking or running performance.

The most common running injuries: There are seven injury hotspots that most frequently plague runners. The first one on the list is runner's knee, or patellofemoral pain syndrome. It's an irritation of the cartilage on the underside of the patella. About 40% of running injuries are knee injuries. According to a poll of 4,500 runners done by the Runner's World, 13% of the runners suffered from a runner's knee.  The second one on the list is Achilles tendinitis. Under increased amounts of physical stress, the tendon tightens and becomes irritated. It makes up 11% of all running injuries. The third one on the list is hamstring issues. Hamstrings drive us up on the hills, and power finishes line kicks. So, when our hamstrings are too tight or too weak, or they don't perform well, we definitely notice it in our performance. The fourth one down the line is plantar fasciitis. It is not shocking that about 15% of all running injuries strike the foot. With each step, our feet absorb a force several times our body weight. 

Plantar fasciitis—small tears or inflammation of the tendons and ligaments that run from your heel to your toes—is usually the top foot complaint among runners. The pain, which typically feels like a dull ache or bruise along your arch or on the bottom of your heel, is usually worse first thing in the morning. 

Shin splints refer to the medial tibial stress syndrome, an achy pain that results when small tears occur in the muscles around the tibia. This makes up about 15% of all running injuries.  Iliotibial band syndrome is when the knee flexion and extension cause the iliotibial band to rub on the side of the femur. This can cause irritation if you take up your mileage too quickly, especially if you're doing a lot of track work or downhill running. It takes up about 12% of all running injuries.  And the seventh one on our list is the stress fracture. Unlike an acute fracture that happens as a result of a slip or a fall, stress fractures develop as a result of cumulative strain on the bone. Runners most often have stress fractures in their tibias, metatarsals, or calcaneus.

References

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3. Duma, S. M., Kemper, A. R., McNally, C., & Brolinson, P. G. (2006). Biomechanical response of the lumbar spine in dynamic compression. Journal of Biomechanics, 39(15), 2934-2940. https://doi.org/10.1016/j.jbiomech.2005.10.018
4. Galbusera, F., & Wilke, H.-J. (Eds.). (2018). Biomechanics of the Spine: Clinical and Surgical Perspective. Academic Press.
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6. Miyasaka, K., Kaneda, K., & Sato, S. (1989). Biomechanical evaluation of the retrolisthesis following decompression surgery in cadaver lumbar spine. Spine, 14(10), 1135-1142. https://doi.org/10.1097/00007632-198910000-00001
7. McGill, S. M., & Norman, R. W. (1986). Lumbar spine loads during full body lifting tasks. Journal of Biomechanics, 19(11), 877-884. https://doi.org/10.1016/0021-9290(86)90136-2
8. Nachemson, A. (1981). Disc pressure measurements. Spine, 6(1), 93-97. https://doi.org/10.1097/00007632-198101000-00022
9. Nordin, M., & Frankel, V. H. (2012). Basic Biomechanics of the Musculoskeletal System (4th ed.). Lippincott Williams & Wilkins.
10. Oxland, T. R., Panjabi, M. M., Southern, E. P., & Duranceau, J. (1991). An anatomic basis for spinal instability: a porcine trauma model. Journal of Orthopaedic Research, 9(3), 452-462. https://doi.org/10.1002/jor.1100090314
11. Panjabi, M. M., Oxland, T. R., Yamamoto, I., & Crisco, J. J. (1994). Mechanical behavior of the human lumbar and lumbosacral spine as shown by three-dimensional load-displacement curves. Journal of Bone and Joint Surgery, 76(3), 413-424. https://doi.org/10.2106/00004623-199403000-00018
12. Pintar, F. A., Yoganandan, N., & Myers, T. J. (1989). Tensile strengths of the human anterior longitudinal ligament. Journal of Biomechanics, 22(7), 667-674. https://doi.org/10.1016/0021-9290(89)90051-7
13. Rohlmann, A., Zander, T., Bergmann, G., & Graichen, F. (2006). Lifting and carrying loads: comparison of spinal load data from an instrumented disc and an instrumented vertebral body. Spine, 31(2), E107-E112. https://doi.org/10.1097/01.brs.0000194770.38474.5b
14. Sato, K., Kikuchi, S., & Yonezawa, T. (1999). In vivo intradiscal pressure measurement in healthy individuals and in patients with ongoing back problems. Spine, 24(23), 2468-2474. https://doi.org/10.1097/00007632-199912010-00007
15. Schache, A. G., Blanch, P. D., Rath, D. A., Wrigley, T. V., Starr, R., & Bennell, K. L. (1999). Intra-subject repeatability of the three-dimensional angular kinematics within the lumbar spine and pelvis during running. Gait & Posture, 10(3), 174-183. https://doi.org/10.1016/S0966-6362(99)00035-3
16. Vleeming, A., Pool-Goudzwaard, A. L., Stoeckart, R., Van Wingerden, J. P., & Snijders, C. J. (1995). The posterior layer of the thoracolumbar fascia. Its function in load transfer from spine to legs. Spine, 20(7), 753-758. https://doi.org/10.1097/00007632-199504000-00001
17. Wilke, H. J., Neef, P., Caimi, M., Hoogland, T., & Claes, L. E. (1999). New in vivo measurements of pressures in the intervertebral disc in daily life. Spine, 24(8), 755-762. https://doi.org/10.1097/00007632-199904150-00005
18. Wilke, H. J., Neef, P., Hinz, B., Seidel, H., & Claes, L. (2001). Intradiscal pressure together with anthropometric data – a data set for the validation of models. Clinical Biomechanics, 16(S1), S111-S126. https://doi.org/10.1016/S0268-0033(01)00006-6
19. Yoganandan, N., Kumaresan, S., & Pintar, F. A. (2000). Biomechanics of the cervical spine Part 2. Cervical spine soft tissue responses and biomechanical modeling. Clinical Biomechanics, 15(6), 398-406. https://doi.org/10.1016/S0268-0033(00)00003-6 Adams, M. A., Hutton, W. C., & Stott, J. R. (1980). The resistance to flexion of the lumbar intervertebral joint. Spine, 5(3), 245-253. https://doi.org/10.1097/00007632-198005000-00008

 

 

 

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Download English Transcript: Thoracic Spine Injuries in Sport

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I am Alex, and we are talking about sports-related injuries of the thoracic spine. This presentation will be a summary of the PowerPoint that you will all have available.

When we talk about thoracic spine injuries, in general, they are rather uncommon due to the anterior biomechanical support of the rib cage. In fact, if the rib cage is intact and so is the sternum, it will increase the stability of the thoracic spine in flexion extension, and lateral bending, and axial rotation by up to 40%.

The area that is most commonly affected by injuries is the T/L junction, so the area between T9 and about L3. This is due to the fact that the thoracic spine is rather rigid and the lumbar spine rather mobile, so this transition from rigid to mobile just makes it more prone to injury. And in addition, when you stand upright, the sagittal alignment of the spine between about T10, 11 and L2 is relatively straight, so the ideal center of mass is anterior to 10, 11. And that results in a flexion moment at the T/L junction, which then, again, creates greater risk of injury in this transitional region.

It is easy to think of many scenarios where we may encounter a patient with a thoracic spine injury. And it is really important to remember that, particularly if that patient was subjected to acute high-energy trauma, or if we encounter an unconscious patient, any such patient really has to be approached as having a coexisting catastrophic spinal injury. This means no unnecessary removal of athletes' equipment during the initial assessment.

It also needs to be remembered that, particularly if you have a T/L junction fracture, those patients are particularly vulnerable to any rotational movement, so log rolling should be performed with extreme care. When transporting the athlete from the field, spinal precautions should be implemented, so use a rigid backboard and cervical immobilization. In addition, any injuries of the thoracic spine may be accompanied by presentations such as pneumothorax, or diaphragmatic ruptures, or rib fractures, which may affect ventilation. And if that's the case, these things, of course, must be addressed with priority.

When it comes to the diagnostic work up, in elite sports in particular, the threshold for imaging should be very low. In fact, the teams I work with we literally MRI everything. Because if a bony injury is suspected, initial X-rays may fail to show the pathology, so follow-up by CT or MRI may be indicated in that case.

If you have a suspected muscular injury, there's an ideal imaging window of about 2 to 48 hours. That's the time frame in which the hematoma that has formed is usually located to the actual injury site. After that, it may extend outside the involved muscle, which then renders the diagnosis a little bit more problematic. MRI is usually the modality of choice. However, in recent years, sonography is really on the march. And it is used more and more, particularly for initial on- site evaluation of the injury.

We begin talking about injuries with musculo-ligamentous injuries. These may occur either acutely due to high energy mechanisms, or chronically due to overuse and high-repetition mechanisms, such as rowing. Acutely, these injuries are usually caused by violent rotational or bending forces in a fashion not unlike those encountered in whiplash injuries of the cervical spine.

The onset of symptoms is usually delayed about 12 to 24 hours due to the inflammatory cascade and may be accompanied by paravertebral muscle spasm. I see that a lot. Pain and tenderness are the most common symptoms. Injuries in the throwing athlete tend to involve excessive rotational, torsional stress. What is interesting in this case is that the contralateral side is frequently found to be symptomatic and not the dominant throwing arm.

In addition to these acute presentations, chronic overuse injuries may also occur. Rowing, for instance, has high incidence, about 22% of back injuries, 9% of rib cage injuries, just from the continuous repetitive motion of the actual rowing. These athletes are also prone to stress fractures involving the posterior ribs. And that is because in that area, there is a particular pull of the serratus anterior, the pull from the rhomboids, and the latissimus dorsi, and the erector spinae at about T4 to T7. And that juncture area renders this area particularly susceptible also to strains and stress fractures.

As with any other region, disc herniations may also occur in thoracic spine due to axial loading and rotation on a flexed spine. And then you have the traumatic herniation of the nucleus pulposus through the annular defect. However, these injuries are very rare in the thoracic spine. There's not a lot of data on it. One study from the NFL suggested that only about 2% of all disc herniations actually occur in the thoracic spine, 75% percent of those below the level of T8, most likely due to the biomechanical properties in that area that we just discussed.

When it comes to symptoms, these often include some form of axial pain, radiculopathy, and/or myelopathy. Axial pain is the most common symptom, and it's usually localized to the mid or lower thoracic region near to the actual level of injury. When it comes to radicular pain-- radicular pain referring to this band-like discomfort radiating anterior in a dermatomal distribution-- usually the level of T10 is affected regardless of the actual disc level involved.

What we really must not miss is myelopathic signs, such as muscle spasm, weakness in the lower extremities; long track signs, such as wide-based gait, spasticity, or positive Babinski. Also, as with the other regions, thoracic spine lumbar pathologies are usually treated non-surgically, and symptoms will remit over the course of several weeks to months, depending on the severity.

Thoracic spine fractures may be classified into four broad categories. You have the anterior wedge compression injury, the burst injuries, Chance fractures, and fracture-dislocations. Axial loading with flexion produces the anterior wedge compression injury, whereby the amount of wedging is usually quite small, and the anterior portion of the vertebral body is rarely more than 25% shorter than the posterior body. And because of the rigidity of the rib cage, these types of fractures are usually stable.

Burst injuries are caused by vertical axial compression. Chance fractures are these fractures where you have a transverse fracture through the entirety of the vertebral body. These are caused by flexion about an axis anterior to the vertebral column and are also associated with retroperitoneal and abdominal visceral injuries. So that's also something to keep in mind.

Fracture-dislocations are relatively uncommon in the thoracic spine because of the orientation of the facet joints, and these injuries almost always are due to extreme flexion or blunt trauma-- which has to be severe-- to the spine. And that then causes disruption of the posterior elements, such as the pedicles, and the facets, and the lamina of the vertebra. Also, because the thoracic canal is pretty narrow in relation to the spinal cord, any fracture-subluxation in the thoracic spine commonly results in complete neurological deficits.

Simple compression fractures are usually stable and can be treated with a rigid brace. Burst fractures, Chance fractures, and fracture-dislocations, on the other hand, are extremely unstable and almost always require internal fixation.

Sternal fractures and dislocations are pretty rare due to the elastic recoil of the ribs, which suspend the sternum. And they usually are associated with contact sports, such as hockey, or football, or rugby. The problem is not necessarily the sternal fracture itself, but the potentially associated injuries, such as spinal injuries, injury to the central nervous system, cardiac contusion, dysrhythmias Diagnosis is pretty easily done by a chest X-ray. Ultrasound or CT may also play a role. And cardiac monitoring is important in this case.

We distinguish two different types. The type I, which is the posterior dislocation of the body due to the direct force, such as a kick. Type II is posterior dislocation of the manubrium due to direct force to the manubrium itself. Cervical hyperflexion is the mechanism here, for example, during a tackle in rugby or football.

Rib fractures are also most commonly resulting from trauma, but as we said, we can also have fatigue fractures. They usually heal very quickly and without any complications, but there's also the likelihood that there may be accompanying features. If you have a rib fracture, be aware of hemothorax, lacerations of the lung parenchyma and the intercostal artery. If you have a fracture of the ribs 1 to 3, always consider vascular or neurological injury. If you have a fracture of ribs 9 to 12, you want to consider liver, spleen, or renal injuries.

In conclusion, the anatomical and biomechanical characteristics of the thoracic spine and the rib cage are very important in understanding and recognizing injury patterns. And although the incidence of thoracic spine injuries in sports is low compared to the cervical and the lumbar spine, it really is still a region that is vulnerable to injury. I work in ice hockey, and I see a lot of injuries in that area, some of them really nasty. So a thorough knowledge of the biomechanics, and the anatomy, and the mechanism of injury really will help you to get the most successful medical care to the athlete.

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