The Effect of Lumbosacral Posture on a Modification of the Straight Leg Raise Test

A systematic review of the passive straight leg raising test as a diagnostic aid for low back pain (1989 to 2000)

STUDY DESIGN

A systematic review.

OBJECTIVES

This systematic review sought papers (January 1989-January 2000) on the passive straight leg raising test (PSLR) as a diagnostic component for low back pain (LBP) to identify, summarize, and assess developments in the test procedure, the factors influencing PSLR outcome, and the clinical significance of that outcome.

SUMMARY OF BACKGROUND DATA

Previous studies suggested that the PSLR tractioned the sciatic nerve and that diminished leg elevation with reproduced pain indicated low lumbar intervertebral disc pathology.

METHODS

Searches on six computerized bibliographic databases identified publications written about the PSLR. Papers were excluded if they were published before January 1989, were non-English language papers, or employed either an active SLR or a PSLR for purposes other than LBP diagnosis. The references of qualifying papers (and the references of references) were searched. Contact with primary authors, and others known to be active in this field, was attempted.

RESULTS

The PSLR procedure remains unchanged. The influence of hip rotation during the PSLR was discussed without consensus. Biomechanical devices improved intra- and interobserver reliability and so increased test reproducibility. Hamstrings were found to have a defensive role in protecting nerve roots by limiting PSLR range in cases of nerve root inflammation. A small diurnal variation in the PSLR may imply a poorer prognosis. A positive PSLR at 4 months after lumbar intervertebral disc surgery predicted poor reoperative outcome, and a negative 4-month PSLR predicted excellent outcome. The influence of psychosocial factors was not discussed, neither was the diagnostic significance of a negative PSLR outcome.

CONCLUSIONS

There remains no standard PSLR procedure, no consensus on interpretation of results, and little recognition that a negative PSLR test outcome may be of greater diagnostic value than a positive one. The causal link between LBP pathology and hamstring action remains unclear. There is a need for research into the clinical use of the PSLR; its intra- and interobserver reliability; the influences of age, gender, diurnal variation, and psychosocial factors; and its predictive value in lumbar intervertebral disc surgery.

Differential Diagnosis and Management of Spinal Nerve Root-related Pain

Pain originating from spinal nerve roots demonstrates multiple pathogeneses. Distinctions in the patho-anatomy, biomechanics, and pathophysiology of spinal nerve roots contribute to pathology, diagnosis, and management of root-related pain. Root-related pain can emerge from the tension events in the dura mater and nerve tissue associated with primary disc related disorders. Conversely, secondary disc-related degeneration can produce compression on the nerve roots. This compression can result in chemical and mechanical consequences imposed on the nervous tissue within the spinal canal, lateral recess, intervertebral foramina, and extraforminal regions. Differences in root-related pathology can be observed between lumbar, thoracic, and cervical spinal levels, meriting the implementation of different diagnostic tools and management strategies.

Mechanical behaviour of hamstring muscles in low-back pain patients and control subjects

The purpose of this study was to measure and compare the passive elastic moment, the stiffness and the damping coefficient of the hip joint, as functions of the hip and knee joint angles in men with and without low-back pain. Two conventional tests, the straight-leg-raising test and the trunk forward flexion, were also performed and compared between these subjects. The passive elastic moment was measured using an isokinetic device in the passive mode. This device raised the lower limb from the horizontal position to the straight-leg-raising angle at a slow and constant angular velocity. A custom-made splint connected with the lever arm of the isokinetic device maintained the knee in extension and the ankle in the neutral position. The damping coefficient of the hip joint was measured for 0, 15, 45, 60, 75 and 90% of straight leg raising angle of each subject, using the suspension method based on small oscillation theory. To ensure that muscles were inactive during the passive hip moment tests, muscle activity was monitored with surface EMG. The stiffness was computed as the ratio of the change in passive elastic moment to the change in the hip angle. The passive elastic moment, the stiffness and the normalized trunk flexion were significantly different between the two groups respectively. There was, however, no difference between the two groups in the results of straight-leg-raise and damping coefficient of the hip. The passive elastic moment was a nonlinear function of the hip flexion angle and showed large intersubject differences, especially as the joint limit was approached. The damping coefficient was a polynomial function of the hip flexion angle. The measured variables were analysed using a discriminant function and it was shown that the two groups were clearly discriminable in a meaningful manner.