Huijbregts PA. HSC 11.2.3. Lumbopelvic Region: Anatomy and Biomechanics. In: Wadsworth C. HSC 11.2. Current Concepts of Orthopaedic Physical Therapy. LaCrosse, WI: Orthopaedic Section APTA, 2001

Learning Objectives

After completion of this monograph the course participant will be able to describe:

  1. The osseous anatomy of the lumbopelvic region.
  2. The joint anatomy of the lumbopelvic region.
  3. The musculoligamentous anatomy of the lumbopelvic region.
  4. The neurovascular anatomy of the lumbopelvic region.
  5. The biomechanics of the lumbopelvic joints.
  6. The biomechanics of the lumbopelvic musculoligamentous structures.
  7. The biomechanics of the lumbopelvic neurovascular structures.
  8. The biomechanics of lumbar spine cardinal plane and coupled motions.
  9. The concept of form and force closure in the sacroiliac joint.
  10. The biomechanical influences of the lower limb on the lumbopelvic region.

Low back pain and its related disability are major societal problems. Eighty percent of all people experience low back pain (LBP) at some point in their lives.1 Back symptoms are the most frequent reason to seek consultation with orthopaedic surgeons or neurosurgeons; they are the second leading reason for physician visits.2 In the United Kingdom, each year 7% of the adult population will consult with their general practitioner for LBP.3 In their systematic literature review on the prevalence of LBP in adults, Loney and Stratford4 found that 19.2+/-9.6 % of people questioned had LBP at the time of survey. The percentage of people with LBP in the year prior to the survey was 32.37+/-23.6%. Based on one US and one Canadian study they estimated mean point prevalence for LBP in North American adults at 5.6%. In other words, 10 of every 178 million North American adults experience LBP in any given day.4 In the US, the total yearly costs associated with LBP, including both direct health care costs, and indirect costs of work loss and disability payments have been estimated to exceed 50 billion dollars.2 Three-fourths of patients taken off work due to LBP have sufficiently recovered to return to work within 6 to 8 weeks, but 2 to 3% of patients develop chronic disabling LBP lasting more than one year.5 Of all worker’s compensation claimants, a relatively small percentage of 10 to 25% accounts for the majority (70 to 87%) of medical and disability benefit costs.5

Despite this high prevalence of LBP and the astronomical costs associated with this problem a number of myths continues to circulate about LBP. Fritz6 mentioned 3 common misconceptions. Her LBP myth #1 is that “most people get better no matter what we do.” Practitioners have generally assumed that the natural history of LBP is relatively benign: 80 to 90% of patients with LBP are expected to recover in about 6 weeks, irrespective of the administration or type of treatment.1 In a prospective trial Skargren et al7 randomly allocated 323 patients between 18 and 60 years of age to either chiropractic or physical therapy (PT) for treatment of LBP or neck pain. Among other variables, they researched recurrence and seeking of additional health care. Only 19% in the chiropractic group and 18% of patients in the PT group reported no recurrence at a 12 month follow-up; nearly 60% of patients reported 2 or more recurrences. Fifty-nine percent of chiropractic patients and 41% of PT patients sought additional care, but only 36% and 29%, respectively, returned to their initial provider. Croft et al3 studied 463 adults aged 18 to 75, who consulted with their general practitioner for mechanical LBP. Of these patients, 59% did not consult again with their general practitioner, 32% consulted again within 3 months after the initial visit, and 8% consulted again after the 3 month period. The authors conducted follow-up interviews with 218 patients. Of those interviewed within 1 to 2 weeks after the initial visit, 2% reported having no pain or disability. At 3 months this number increased to 21%. At 12 months only 25% of those interviewed reported no complaints. These studies indicate that LBP may not be as benign and self-limiting as has been assumed, possibly because a large percentage of patients is lost to follow-up as they do not return to their original provider despite continued or recurrent complaints. This is extremely well illustrated by the Croft et al3 study in which the physician might erroneously assume that after 3 months 92% of patients no longer has LBP, even though follow-up showed continued complaints in 75% of (the admittedly smaller sample of) those interviewed.

LBP myth #2 is that “the situation is improving.Taylor et al reviewed the National Hospital Discharge Survey data for the 1979 to 1990 period to investigate variations in inpatient management of mechanical LBP in patients 20 years or older. They found an increase in low back surgery from 147,500 in 1979 to 279,000 in 1990. Adjusted for population growth this meant an increase from 102 to 158 low back surgeries per 100,000 adults. Non-fusion surgery increased by 47%; surgeries involving fusion increased with 100%. Not only have back surgery rates risen sharply, Fritz6 noted that chronic LBP disability has also risen dramatically in the past 25 years.

LBP myth #3 is that “the medical community knows how to approach the problem.”6 Controversy clearly exists regarding the most appropriate treatment for LBP. Taylor et al2 found that in the 1988 to 1990 period annual LBP surgery rates varied widely between the different geographical locations in the US: 113 per 100,000 adults in the western US, 131 in the Northeast, 157 in the Midwest, and 171 in the South. Reported LBP prevalence in these 4 areas was nearly identical. This wide geographical variation despite similar prevalence indicates that the choice for surgical management of LBP is far from uniform.

The extensive personal and societal impact of LBP is obvious. The natural history of LBP may not be as benign as previously assumed. Research appears consistent with the interpretation that 90% of patients will have stopped consulting with their initial or any provider and are thus lost to follow-up rather than having no more pain or disability. A small percentage of patients develop chronic disabling pain and these patients become responsible for the majority of costs. Early identification and appropriate intervention could have a major impact on costs. The medical profession does not appear to have a uniform answer to LBP: increasing surgery rates and wide geographic variation in management strategies need not necessarily be interpreted as a sign of increased treatment success. Mielenz et al8 investigated 1580 patients with acute LBP initially seen by 208 randomly selected health care providers (orthopaedic surgeons, primary care providers, chiropractors) in North Carolina. A PT saw 199 (12.8%) of the patients, by referral or direct access. The PT patients had higher baseline scores on the Roland-Morris Questionnaire. This instrument describes the impact of LBP on various functional activities; higher scores indicate higher levels of disability. Location of pain also played a role in referral: patients with LBP and pain below the knee in one or both legs were more likely to be referred to PT. This study seems to indicate that the referral of choice for patients with more severe acute LBP is PT rather than medical, surgical, or chiropractic treatment. A natural history less benign than previously assumed, an increase in chronic LBP-related disability, seemingly inadequate surgical treatment options, and PT as the referral of choice for more involved LBP patients makes in-depth knowledge of all aspects of LBP a necessity for every PT involved in treating these patients. In this monograph we will review the anatomy and biomechanics of the lumbopelvic region. Monograph 11.2.4. will deal with changes as a result of aging, pathology affecting the lumbopelvic region, diagnosis, and PT treatment. It will also contain the case studies that will illustrate application of this information to patient management.

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