Monday, September 28, 2015

Athletes and Pathokinematics - Part V - Lumbar Spine

Pathokinematics can have as profound an impact at the sacral and lumbar spine as they do at the hip, knee, foot and ankle.  As described previously, we typically see pathokinematics result in one or a combination of the following movements at the pelvis/lower lumbar spine

1.     Trendelenburg (dropping of the pelvis on the contralateral side during weight bearing on the ipsilateral side)

2.     Lumbar sidebending

As you can see on the diagram, the pelvis, sacrum and lumbar spine are intimately involved with one another.  Motion in one will result in motion of the structure superior and inferior to that structure.  Therefore, if the pathokinematics listed above occur in high loading situations or during high impact sports, it can alter the angles of the articulating surfaces which, in turn, can drastically alter the length tension relationships of the musculature supporting the sacral and lumbar spine.  Also, this can result in abnormal force attenuation on the bones, tissues and ligaments of the sacral and lumbar spine, all of which can lead to several problems including:

1.     Sacroiliac (SI) joint pain – the sacroiliac joint, is the joint between the sacrum and the ilium of the pelvis.  By its architecture, it is designed to withstand compression and some components of shear force.  However, it does not do as well with larger magnitude shearing stresses, especially when they are repetitive in nature or when they are combined with high impact sports.  This joint has a very small amount of movement and the exact degree is still debated in the literature at this time.[i]   Some authors report this movement to be as little as 2 degrees and some claim it is as high as 18 degrees.  Whatever the actual degree of movement is, excessive movement of this joint can result in pain and dysfunction.  With a trendelenburg movement pattern, shear stresses to the SI joint (in particular the articulating surfaces) are increased and this in turn increases shearing loads to the supporting ligamentous structures (anterior and posterior sacroiliac ligaments).  Ultimately, this can result in pain as well as increased laxity in the joint.  This increased joint laxity can result in an increased likelihood of movement in the joint when sustaining greater loads and single leg activities. 

2.     Facet syndrome – on the posterior aspect of the lumbar spine are the facet joints, with one on   Each vertebral body has both a superior and inferior articulating process.  In the diagram to the right, the inferior articulating process of L4 articulates with the superior articulating process of L5.  These joints are compressed together during extension of the lumbar spine and gapped during flexion of the lumbar spine.  The facets on the right are compressed with right side bending and gapped with left side bending and vice versa.  When a trendelenburg is present in high loading situations, this results in gapping of the facets on the side on which the hip is falling and compression of the facets on the side on which the hip is elevated.  This excessive movement can result in:
the right of the spinous process and one on the left of the spinous process.

a.     Osteophyte formation –  this is a bony formation along the facet joint that can result in narrowing of the neural foramen.  This can result in pain in the joint as well as impingement of the nerve root.

b.     Inflammation of the joint – this inflammation can result in pain with extension or side bending activities as well as inhibition of related musculature (specifically the multifidus).

c.     Early Degenerative Joint Disease – both osteophyte formation and inflammation can result in early deterioration of the joint resulting in decreased mobility of the lower lumbar spine and pain.

3.     Disc pathology – the intervertebral disc is composed of the annulus fibrosus (outer layer) and the  It is located between the vertebral bodies from the cervical spine to the lumbar spine.  Its function is to resist compressive forces imparted to the spine and it is the shock absorber of the spine.  Shearing forces imparted to this structure (via trendelenburg and sidebending of the lumbar spine) can result in degenerative changes within the disc.  Over time, this can result in:
nucleus pulposus (the inner layer).

a.     Disc bulge – a disc bulge results when the nucleus migrates to one side (right or left) and results in annulus fibers bulging out on one side.  This bulging will often result on the side in which the more frequent side bending occurs or on which the magnitude of the force is higher.  This can result in pain or impingement of the nerve root.

b.     Disc herniation – a disc herniation is a progression of the disc bulge.  A herniation occurs when the nucleus actually migrates out of the annulus.  Mechanisms of injury are similar to those above however this is a much more involved injury.  With herniation, there is a significant inflammatory response and pain, and it is often associated with radicular symptoms (pain, numbness or weakness down the leg).  Depending on the severity, this can require surgery to repair.

c.     Disc narrowing – with repetitive wearing of the tissue and its resulting breakdown, we can see a narrowing of the intervertebral space.  Over time, this can result in early fusion of some of the lower lumbar segments (most commonly L5/S1), and a resulting decrease in mobility of the lower lumbar spine and/or pain. 

4.     Muscle strains – There is a tremendous amount of musculature (superficial and deep) of the   Imbalances in this system can lead to decreased motion of the spine, abnormal motion of the spine and pain.  With pathokinematics, a lot of musculature of the lower lumbar spine is compromised.  This is due to several factors:
lumbar spine.

a.     Change in length tension relationships – with so many of the muscles of the lumbar spine having attachments to the pelvis and spine, side bending or a trendelenburg significantly changes the length tension relationships of these muscles and thereby dramatically alters their maximal force they are able to produce.  This also results in altered force production between the right and left sides of the lumbar spine.  These in isolation or combined can result in muscles being weakened and therefore unable to resist the load imparted to them, resulting in muscle strains. 

b.     Change in recruitment patterns – with a change in length tension relationships and the associated compensatory strategies, altered recruitment patterns can result over time.  Just like the pitcher who has developed bad throwing habits, if these are never retrained, then they can persist and ultimately add to muscle pain and/or contribute to or directly cause muscle strains.

c.     Weakness due to pain –pain occuring as a result of the movement patterns described above, can lead to weakness and atrophy of some of the supporting musculature of the lumbar spine.  In one study the authors found that the multifidus had a 25% decrease in cross sectional area with pain. They also found that the muscle must be retrained in order to regain its base level of strength and cross sectional area once the pain is resolved. [ii]   If the muscle is not retrained and the weakness remains, the area will be more susceptible to overuse and injury. 

In the following example we see an athlete who has been complaining of lower back pain as well as knee pain.  When assessing his functional movement with a squat, we see a significant lateral shift to the right.  With this degree of lateral shift, there is a significant increase in loading to the right knee and hip and also to the right lower lumbar spine. 

When evaluating this individual using other functional testing positions (such as the single leg squat) he continues to demonstrate these same pathokinematics with a loss of control at the hip.  This results in a significant amount of rotation at the hip and sidebending in the lumbar spine.  So again, we see increased loading to the lumbar spine resulting in increased stress to the facet joints and intervertebral discs.  Over time, this can result in disc bulges/herniations, spondylolysis (stress fracture) or spondylolisthesis (slippage), as well as low back strains and sprains. 

In this particular example, based on these and other tests performed in the physical therapy clinic, the athlete is, in fact, likely to be at risk for disc herniations and bulges, common athletic related spinal fractures and low back pain, as mentioned above.  Additionally, his performance will be drastically reduced due to weakness in the left leg which occurs over time due to the high degree of lateral shift to the right that he demonstrates.  Instead of having equal power output from the core down through the lower extremity in each leg, he will have less power output on the left.  In addition, the right side will have less power output than would be possible, due to a change in length tension relationships on the right, which is addressed in more detail in the next chapter.

In conclusion, whether they are seen at the foot or the spine, pathokinematics have a dramatic impact on the entire system.  Whether it is due to abnormal force attenuation, altered recruitment patterns or altered length tension relationships, pathokinematics can dramatically impact the kinetic chain causing pain and ultimately injury over time.  After reviewing the entire lower extremity, we can easily see why it makes sense that there would be an increased likelihood and a potentially increased magnitude of injury when pathokinematic movement patterns are combined with higher impact sports and those involving increased loads.

In addition, the research shows that the magnitude of the force that the body has to withstand with athletic activity ranges anywhere from 3 to 8 times body weight, depending on the type of surface and the sport.  Considering the amplitude of forces that the body must withstand with athletic activity, improving the efficiency of movement and the amount of force the muscles have to and are able to absorb, transfer, and manage is essential to reducing the potential for injury, as well as for maximizing power and endurance. 

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Dr. Nessler is a practicing physical therapist with over 17 years sports medicine clinical experience and a nationally recognized expert in the area of athletic movement assessment.  He is the developer of an athletic biomechanical analysis and author of a college textbook on this subject.  He serves as the National Director of Sports Medicine for Physiotherapy Associates, is a Safety Council Member for USA Cheer National Safety Council and associate editor of the International Journal of Athletic Therapy and Training. 

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