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Back pain studies examine racial differences in use of spine x-rays and effectiveness of sacroiliac joint function tests

Low back pain is a leading cause of spine x-rays among outpatients. Although many studies have shown black patients to receive fewer diagnostic procedures than whites, this is not the case with spine x-rays, according to a study supported by the Department of Veterans Affairs and the Agency for Healthcare Research and Quality.

Physical therapists rely on a variety of tests other than x-rays to examine sacroiliac joint (SIJ) dysfunction, a cause of low back pain that is presumed to be due to biomechanical disorders of the joint such as hypomobility and malalignment. A second AHRQ-supported study provides strong evidence to support the use of some tests over others to examine SIJ dysfunction. The studies are summarized here.

Selim, A.J., Fincke, G., Ren, X.S., and others. (2001). "Racial differences in the use of lumbar spine radiographs." (AHRQ grant HS08194). Spine 26(12), pp. 1364-1369.

Differences in patient clinical characteristics are the source of racial differences in the use of lumbar spine x-rays to diagnose patients with low back pain, conclude the authors of this study. They investigated the use of lumbar spine x-rays in 401 patients with low back pain seen at four Veterans Affairs outpatient clinics between 1993 and 1996. They stratified patients into groups of white patients (315 patients) and minority patients (22 black, 4 Hispanic, and 1 other race). Upon study entry and 1 year later, patients completed a health status questionnaire and low back pain questionnaire (including questions about radiating leg pain). They also were asked about coexisting illnesses and were asked to perform a straight leg raising (SLR) test.

Minority patients had lumbar spine x-rays more often than white patients (48 vs. 27 percent). However, minority patients had higher pain intensity scores than white patients (63 vs. 48 percent) and were more likely to have radiating leg pain (76 vs. 55 percent). Minorities also had worse physical functioning, general health perception, social functioning, and role limitations because of emotional problems. At a higher intensity level of low back pain, minority patients received more lumbar spine x-rays than did white patients (74 vs. 50 percent). Also, among patients with radiating leg pain (positive SLR test), minority patients had more lumbar spine x-rays than white patients (23 vs. 11 percent).

However, after adjusting for these multiple clinical characteristics, race was no longer an independent predictor of use of lumbar spine x-rays. This study demonstrates the importance of careful and comprehensive case-mix adjustment when assessing apparent racial differences in the use of medical services, conclude the researchers.

Freburger, J.K., and Riddle, D.L. (2001, May). "Using published evidence to guide the examination of the sacroiliac joint region." (National Research Service Award training grant T32 HS00032). Physical Therapy 81(5), pp. 1135-1143.

Various tests have been used by physical therapists to identify dysfunction of the SIJ region. These investigators reviewed studies from 1966 to 2000 on the diagnostic validity of tests designed to detect dysfunction in the SIJ region. They found that there is some evidence to support the use of pain provocation tests (application of force to the SIJ or related structures to reproduce the patient's pain) and the patient's description of pain location to identify dysfunction in the SIJ region. However, there are few data to support the use of symmetry or movement tests to identify SIJ dysfunction.

In symmetry and movement tests, physical therapists palpate and judge the relative heights of bony landmarks along the iliac spines, while the patient is sitting and then standing, to evaluate SIJ alignment. Reviewed studies showed poor agreement between therapists and poor reliability and validity of data obtained from the tests. The results of x-ray studies suggested that the movements associated with SIJ bony landmarks are too small to accurately assess with palpation or visual assessment. Use of movement and symmetry tests together to identify SIJ dysfunction appeared to yield more reliable data than use of a single test, but more studies are needed.

Although results were mixed, evidence supported the reliability of data obtained with some pain provocation tests for determining the presence of SIJ dysfunction. Studies that have used anesthetic blocks suggest that a combination of positive pain provocation tests and the patient's description of the pain location may be useful for diagnosing SIJ dysfunction. In these studies, patients with SIJ dysfunction reported marked reduction in pain during pain provocation tests after anesthetic blocks of that region. Pain descriptions that appear to have some support include absence of pain in the lumbar region, pain below L5 (fifth lumbar vertebra), pain in the region of the posterior superior iliac spines, and pain in the groin area. In the absence of further research, the investigators suggest that therapists use pain provocation tests and descriptive information on pain location to identify dysfunction of the SIJ region.

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