The Effect of Somatic Dysfunction of the Pelvis, Sacrum and Lower Lumbar Spine on Weight Bearing
Condition: Somatic Dysfunctions of Pelvis; Somatic Dysfunctions of Sacrum; Somatic Dysfunctions of Lower Lumbar Spine; Weight-Bearing
MeSH terms: Body Weight
Study type: Observational

Summary: 
      The study aims to determine if somatic dysfunctions of the pelvis, sacrum and lower lumbar
      spine have an effect on weight bearing. Our subjects are young, healthy subjects without
      recent soft tissue or osseous injury, a less than predetermined leg length discrepancy or
      OMM/chiropractic treatment. Their leg lengths will be measured; weight-bearing will be
      measured using a specialized scale and somatic dysfunctions diagnosed to determine if any
      correlation exists.
    

Detailed description: 
      Most sources claim that in individuals with leg length discrepancies, they tend to place more
      weight through the shorter lower extremity.1,2 Few cases state that the opposite is true.3
      Many health care practitioners diagnose leg length discrepancies. Osteopathic physicians who
      practice with Osteopathic Manipulative Medicine (OMM) will also diagnose leg length
      discrepancies. They use testing to evaluate whether a leg length discrepancy is structural or
      functional. A structural leg length discrepancy is associated with shortening of bony
      structures.4 The structures affected can be due to congenital defects, which result in
      possible structural shortening of the tibia or femur, slipped capital femoral epiphyses
      (SCFE), or congenital dislocation. Other causes of structural leg length discrepancies
      include post total hip replacement, infections, tumors, paralysis, and trauma, including
      fractures where the gross length of a limb is altered.4 A structural leg length discrepancy
      can be most accurately assessed by physically measuring the distance between the anterior
      superior iliac spine (ASIS) and medial malleolus.4 The most reliable method of diagnosing a
      structural short leg is through full body radiographs. 6 A functional leg length discrepancy
      is a result of altered mechanics of the lower extremities. It is thought that a functional
      short leg occurs secondarily to a rotated pelvis caused by joint contractures and/or axial
      misalignments, including scoliosis.4 In osteopathic literature; functional leg length
      discrepancies are also thought to be the result of altered positions of the pelvis and
      sacrum. It is also thought in osteopathic philosophy that the position of the fifth lumbar
      vertebra affects the position of the sacrum. Therefore dysfunction of L5 will change the
      position of the sacrum such that a functional short leg is created.2(p.780-782) A common
      cause of functional leg length discrepancies diagnosed by osteopathic physicians is that of
      sacral base unleveling.5 The way in which a leg length discrepancy causes unleveling of the
      sacrum is through the femoral head of the longer leg driving the pelvis into a posterior
      rotation via forces placed through acetabular contact. Then the pelvis will typically rotate
      forward in attempts to lengthen the shorter leg, causing the sacral base to become unlevel.5
      In addition, the sacral base tilts toward the side of the short leg.6 Standing postural
      x-rays, which outline sacral declination, are often used by chiropractors and osteopathic
      physicians to diagnose functional leg length discrepancies.6 Another way that functional leg
      length discrepancies are confirmed is through the supine to long sitting test, which tests
      for the presence of innominate rotations that may affect leg length as the cause.

      There is no research known to support the presence of somatic dysfunctions, leg length
      discrepancies and altered weight bearing through lower extremities secondary to this.

      It is common practice among osteopathic physicians who utilize OMM to diagnose
      musculoskeletal somatic dysfunctions of the pelvis, sacrum and lumbar spine. All these
      findings can contribute to low back pain. Therefore, it is the common practice of these
      physicians to diagnose leg length discrepancies, as it may ultimately result in low back
      pain.

      Somatic dysfunction in osteopathic nomenclature is defined as 'impaired or altered function
      of related components of the somatic (body framework) system: Skeletal, arthrodial and
      Myofascial structures, and related vascular, lymphatic and neural elements'.2

      There are specific somatic dysfunctions that lead to leg length differences. These effects
      include the sacral base tilting toward the side of the short leg, a low iliac crest on the
      short leg side, a forward rotation of the innominate on the shorter side and/or a posterior
      rotation of the innominate on the side of the longer leg as a compensatory measure. The
      lumbar spine will develop a convexity toward the side of the short leg.6 Their definitions
      are as follows:

      Anteriorly rotated innominate: Entire innominate appears to be rotated anterior in relation
      to the opposite innominate. The ASIS will be more inferior or caudad and PSIS will be more
      superior or cephalad.2(776-778), 6 Posteriorly rotated innominate: Entire innominate appears
      to be rotated posterior in relation to the opposite hip bone. The ASIS will be more superior
      or cephalad and the PSIS more inferior or caudad.2(776-778), 6 Superior shear of the
      innominate: ASIS, PSIS and pubic ramus is more superior or cephalad than the opposite
      side.2(776-778), 6 Inferior shear of the innominate: ASIS, PSIS and pubic ramus is more
      inferior or caudad than the opposite side.2(776-778), 6

      The way that osteopathic physicians determine the side of the somatic dysfunction is through
      the ASIS compression test. This is defined as follows:

      ASIS compression test: Test for lateralization of somatic dysfunction of the sacrum,
      innominate or pubic symphysis. A posterior compression normally produces a palpatory sense of
      'give' or 'resilience' as the innominate glides slightly posterior at the sacroiliac joint on
      that side. Somatic dysfunction of the pelvis on the side of compression produces resistance
      to the test determining the side of lateralization which is analogous to the determining the
      dysfunctional side. This is interpreted as a positive ASIS compression test.2(777)
      Individuals who have suffered from any type of osseous or soft tissue traumatic injuries in
      the last three months do not make suitable subjects for an evaluation of somatic
      dysfunctions' effects on weight bearing. Neither do individuals who have suffered from any
      type of osseous or soft tissue injuries in the lower extremity joints (knee, ankle, hip) in
      the last twelve months. As stated earlier, leg length discrepancies may be a result of
      trauma. Individuals who have suffered traumatic injuries within the last three months may
      exhibit antalgic or compensatory postures which may displace weight bearing more through one
      lower extremity than the other.7 This will ensure that the treatment population will be as
      homogenous as possible and will improve reliability of the study.

      Individuals who have suffered lower extremity injuries in the last twelve months may also
      exhibit altered weight bearing distribution through the lower extremities. This may be
      something, depending on the chronicity of the problem, which alters weight bearing for an
      extended period of time which may vary depending on the person.7 Therefore, excluding
      individuals who have suffered lower extremity trauma in the last twelve months will also be
      excluded from the study to allow for more homogenous characteristics of our sample
      population. The time constraints of three and twelve months respectively were deemed as the
      exclusion times purely from anecdotal and clinical experience with lower extremity injury
      from the principal investigator and his colleagues.

        1. White, S.C., Gilchrist, L.A., Wilk, B.E. Asymmetric limb loading with true or simulated
           leg-length differences. Clinical Orthopedics and Related Research, 2004,421,287-292

        2. Ward, R. Foundations for Osteopathic Medicine 2nd Edition. 2003, p. 614-618, 780

        3. McCaw, S.T., Bates, B.T. Biomechanical implications of mild leg length inequality.
           British Journal of Sports Medicine, 1991, 25,10-13

        4. Gurney, B. Review: Leg length discrepancy. Gait and Posture. 2002, 15,195-206

        5. Dott, G.A., Hart, C.L., McKay, C. Predictability of sacral base levelness based on iliac
           crest measurements. JAOA, 1994,4, 383-390.

        6. DiGiovanna, EL. Schiowitz S. An Osteopathic Approach to Diagnosis and Treatment.
           Philadelphia: Lippincott-Raven, 301.

        7. Riegger-Krugh, C & Keysor, J.J. Skeletal malalignments of the lower quarter: Correlated
           and compensatory motions and postures. J. Orthop Sports Phys Ther. 1996;23(2):164-170.
    

Observational model: Cohort
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        Medical students of Nova Southeastern University College of Osteopathic Medicine (NSUCOM)
        ages 18-40.
      
Keywords: Effect of Somatic Dysfunctions of Pelvis; Effect of Somatic Dysfunctions of Sacrum; Effect of Somatic Dysfunctions of Lower Lumbar Spine; Weight-Bearing