Abstract
Context: Identifying objective measures that correlate with somatic dysfunction palpatory findings will aid in establishing clinical relevance of the findings and provide outcome measures for future studies.
Objective: To investigate the association of altered segmental lumbar vertebral mechanics (ie, somatic dysfunction) as assessed by palpation with bone mineral density (BMD) T-score variability in participants, some with chronic low back pain (CLBP) and others without low back pain (LBP).
Methods: Individuals with CLBP and individuals without LBP were examined by 2 blinded examiners for the presence or absence of paraspinal tissue texture abnormalities, vertebral rotational asymmetry, anterior motion restriction, and tenderness from L1 to L4. All participants then received a dual-energy x-ray absorptiometry scan of the lumbar spine. Bone mineral density T scores were compared between the CLBP and non-LBP groups.
Results: Sixty-three individuals (16 CLBP, 47 non-LBP) participated in the study. Lumbar segments with perceivable rotational asymmetry had higher mean BMD T scores (95% confidence interval [95% CI]) than lumbar segments with no asymmetry (0.5 [0.4-0.7] vs -0.2 [-0.6 to 0.2], respectively; P=.002). Additionally, lumbar segments with anterior motion restriction had higher mean BMD T scores (95% CI) than lumbar segments with no motion restriction (0.6 [0.4-0.7] vs 0.1 [-0.2 to 0.3], respectively; P=.03). Participants with CLBP demonstrated higher regional mean lumbar BMD T scores (95% CI) than those without CLBP (0.9 [0.6-1.1] vs 0.3 [0.2-0.5], respectively; P<.001). After accounting for sex and body mass index, vertebral segments with rotational asymmetry (in non-LBP participants only) and vertebral segments with motion restriction had higher mean BMD T scores than vertebral segments with no asymmetry or motion restriction.
Conclusion: Participants with CLBP had significantly higher lumbar BMD than participants without LBP. The presence of rotational asymmetry or motion restriction was associated with elevated BMD at the affected vertebrae.
Individual physical examination maneuvers should be sensitive and specific and have a positive predictive value. Ideally, the physical findings should also relate to objective measures whenever possible. The physical findings associated with somatic dysfunction include tenderness, tissue texture abnormalities, positional asymmetry, and/or alterations in the articular range of motion.
1-3 Because these findings are assumed to indicate impaired or altered functioning of the skeletal, arthrodial, or myofascial structures, they should correlate with objective measurable findings consistent with biomechanical dysfunction. Potential objective tests that may correlate with somatic dysfunction physical findings include magnetic resonance imaging and computed tomography. These tests are interesting in that abnormalities are frequently found in asymptomatic patients.
4-11
Dual-energy x-ray absorptiometry (DXA), also known as bone densitometry, is potentially a lower-cost option for establishing an objective measure. Bone mineral density (BMD) changes with altered mechanics, allowing for maximum strength along the lines of gravitational force and, thus, should respond to the altered biomechanics from somatic dysfunction. Pathologic changes occur when altered gravitational or mechanical forces are applied over a long period, resulting in bone being laid down to make the affected structures stronger. Gradually, sclerosis, bony outgrowths (ie, osteophytes), or both appear. These changes are the hallmark of degenerative osteoarthritis and manifest as increased BMD when evaluated by DXA.
12-15 In the lumbar spine, osteoarthritis exhibits local pathologic increases in BMD secondary to the formation of osteophytes and bony sclerosis.
16-21 Though many people with osteoarthritis are asymptomatic,
4,5,22,23 chronic low back pain (CLBP) is associated with degenerative changes, such as endplate abnormalities and facet (ie, zygapophyseal joint) degeneration,
10,24-26 as well as clinically reduced gross range of motion.
27,28
The present pilot study investigated the association between somatic dysfunction, as diagnosed by physical examination, and lumbar BMD T scores in participants with CLBP and participants without low back pain (LBP). Given the initial assumption that vertebral somatic dysfunction represents locally altered vertebral biomechanics, the investigators hypothesized that individual vertebral segments that manifested somatic dysfunction would demonstrate altered BMD in relation to unaffected vertebrae. Additionally, the investigators hypothesized that participants with more somatic dysfunction in the lumbar region, particularly those with CLBP, would demonstrate a change in overall lumbar BMD when compared to participants with less total somatic dysfunction.
Healthy volunteers aged 20 to 40 years were recruited from the local community of Kirksville, Missouri. This age range was chosen because these individuals were less likely than older individuals to have radiologic findings of degenerative joint disease that could affect BMD measures. Participants were recruited regardless of LBP history. Study exclusion criteria were the presence of any condition that would alter the lumbar bony anatomy (eg, lumbar or low thoracic vertebral fractures or surgery; known congenital vertebral abnormalities of the lumbar spine, such as spina bifida). Pregnant or potentially pregnant volunteers and those having had manual treatment of the spine within 8 weeks of the initial musculoskeletal examination were also excluded.
Participants completed a medical history questionnaire. Based on their answers, they were identified as belonging to the CLBP or non-LBP group. Participants in the CLBP group had pain in the lumbar region for a minimum of 5 days a week for at least 3 months. The non-LBP group included participants with no self-reported history of LBP in the last 3 months or only occasional nonpersistent LBP not exceeding twice a week. Participants with low pain levels who did not meet CLBP criteria were excluded.
All aspects of the study protocol were approved by the institutional review board of A.T. Still University in Kirksville, Missouri. Informed signed consent was obtained from each participant prior to examination.
The different elements of somatic dysfunction (ie, tissue texture abnormalities, rotational asymmetry, motion restriction, tenderness) were assessed separately for each lumbar vertebra in each participant. Participants received a focused musculoskeletal examination of lumbar vertebrae L1 to L4 by 2 osteopathic physician examiners (K.T.S., B.F.D.). The L5 vertebra was not evaluated due to the high incidence of occult anatomic abnormalities associated with this vertebral segment. The locations of spinous processes of L1 to L4 were marked by drawing a horizontal line in black, water-soluble ink across the vertical midpoint. The spinous process locations were identified using the following anatomic landmarks:
identification of T12 by its smaller spinous process size to verify the location of L1
identification of the twelfth ribs and their attachment site at T12 to identify L1
identification of the iliac crests, approximately at the height of the L4/L5 interspace (ie, Tuffier line)
location of the sacral base and L5 to identify the L4 spinous process
Participants were evaluated in the prone position by the 2 blinded examiners using 4 common osteopathic palpatory assessments (paraspinal tissue texture abnormalities, vertebral rotational asymmetry, anterior springing motion restriction, and spinous process tenderness) to determine the presence of somatic dysfunction.
29 The 2 osteopathic physicians who participated as examiners in the present study established the interobserver reliability of these 4 tests prior to this study. Details of this reliability training were discussed at length in a previous publication.
29
Any inconsistencies in examiner findings were reevaluated by both examiners until consensus was reached regarding the presence or absence of the somatic dysfunction finding. This method of establishing consensus allowed the examiners to continually improve interobserver reliability and is discussed in a previous publication.
30
The 4 assessments of somatic dysfunction were evaluated from L1 to L4 as follows:
Tissue texture abnormalities—The pads of the examiner's fingers contacted the subcutaneous tissue texture overlying the right and left inferior facet joints of each vertebra of the participant. Presence of tissue texture abnormalities was evaluated individually for right and left facet areas based on the presence of localized edema, tissue tension, or fibrotic changes in the subcutaneous tissue.
29 Static rotational asymmetry of the transverse processes—Static positional asymmetry of each vertebra of the participant was assessed by the examiner by palpating for the posterior prominence of the right vs the left transverse process. Both palpatory and visual assessments were used to determine which prominence was more posterior. No motion testing was performed. Posterior prominence of the right transverse process was recorded as right vertebral rotation, and posterior prominence of the left transverse process was recorded as left vertebral rotation.
1,2,31,32 Anterior springing motion restriction—Anterior force was applied with the examiner's thumb or hypothenar eminence on the spinous process of each vertebra of the participant to determine its resistance to springing. This test, which is meant to assess sagittal motion, was performed 1 to 3 times as needed for each participant to assess motion. Resistance to anterior motion was noted in relation to the other vertebrae.
29 Spinous process tenderness—Anterior force was applied directly to the individual spinous processes with the examiner's thumb. A total pressure of 4 kg/cm
2 was used, based on the 1990 American College of Rheumatology criteria for defining a significant tenderpoint in diagnosing fibromyalgia.
33 To mimic the clinical setting, a dolorimeter was not used. Calibration of the applied force was performed prior to each participant examination by repeatedly applying pressure on an 11-lb (5-kg) food scale (model 3870; Taylor Precision Products, Oak Brook, Illinois) with the thumb until intraobserver reliability was obtained for the application of 4 kg/cm
2 of pressure. For both examiners this pressure was enough to blanch the thumb nail but not enough to cause discomfort in the examiner's thumb.
29 Participants verbally indicated when the applied pressure elicited a sensation of pain or tenderness.
The CLBP participants and non-LBP participants were compared on demographic variables using the Fisher exact test (for sex) and Mann-Whitney test (for age and body mass index [BMI]). To test whether the presence or absence of each of the 4 elements of somatic dysfunction (ie, tissue texture abnormalities, rotational asymmetry, motion restriction, tenderness) were associated with BMD T scores for the same vertebral segment, generalized linear mixed models were fit to the data using restricted maximum likelihood estimation. Each participant contributed 4 separate vertebral measurements of somatic dysfunction and BMD to each analysis. The participants were treated as random effects to account for the dependence of the 4 vertebral measurements of somatic dysfunction and BMD for the L1-L4 vertebrae obtained from each participant. Additional generalized linear mixed models included group (CLBP or non-LBP), sex, and BMI to test for the effects of these characteristics on the association of somatic dysfunction with BMD T score. The model assumptions, including normal distribution of errors, were verified. Statistical significance was set at α=.05. Statistical analyses were conducted using SAS 9.2 software (SAS Institute Inc, Cary, North Carolina).
The present study demonstrated several findings that have important implications in clinical practice. Somatic dysfunction findings of positional asymmetry and motion restriction were associated with objective, measurable BMD elevations in affected vertebrae. Though the examiners in the present study underwent stringent interobserver reliability training, the palpatory assessments used in the study are commonly taught at osteopathic medical schools throughout the United States and, thus, are skills available to all osteopathic physicians. Given that the purpose of osteopathic manipulative treatment is to normalize somatic dysfunction, segmental vertebral BMD may be an objective measure for assessing the long-term physiologic effects of osteopathic manipulative treatment.
The present study also found that participants with CLBP had significantly higher mean regional lumbar BMD than participants without LBP. We have discussed possible biomechanical and physiologic mechanisms for the findings of the present study. However, because observed differences in BMD were small, the discussion is inherently speculative without additional research. Further studies are warranted to assess the reproducibility of our findings and to clarify the nature of the observed BMD changes.
Financial Disclosures: The authors have no conflicts of interest to declare. This study was supported by grants from the National Institutes of Health—National Center for Complementary and Alternative Medicine, Grant No. 1R01AT00305, and the American Osteopathic Association, Grant No. 00-04-505.
We thank the following personnel from A.T. Still University: Deborah Goggin, MA, scientific writer, for her editorial assistance, and Patty Lyons, coordinator in osteopathic manipulative medicine, for her role as site coordinator.
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