Research Review by Dr. Shawn Thistle©

Date:

September 2007

Study Title:

The sensitivity of the seated straight-leg raise test compared with the supine straight-leg raise test in patients presenting with magnetic resonance imaging evidence of lumbar nerve root compression

Authors:

Rabin A et al.

Publication Information:

Archives of Physical Medicine and Rehabilitation 2007; 88: 840-843.

Summary:

Lumbar radiculopathy is defined as a disease of a lumbar nerve root, featuring classic signs such as diminished reflexes, pain, paresthesia/sensory loss, and motor weakness. Magnetic Resonance Imaging (MRI) is the most common imaging technique used to assess this condition, as it can readily identify the most common cause – intervertebral disc pathology – including bulges, protrusions, or overt herniation of nuclear material. Previous literature has indicated that MRI has high sensitivity and specificity for detecting disc lesions and nerve root compression – roughly 83% and 78% respectively (numbers vary by study).

Despite these impressive statistics, it has also been well documented that findings on advanced imaging such as MRI do not always correlate with clinical symptoms. Even completely herniated discs appearing on MRI can be clinically silent. For this reason, correlating imaging results with historical and physical examination findings is paramount.

One of the most commonly used clinical tests to evaluate nerve root compromise in the lumbar spine is the straight-leg raise test (SLR). A recent systematic review (reference below) indicated that the SLR has high sensitivity (~ 90%) but relatively low specificity (below ~ 30%). A high sensitivity rate suggests that given a negative SLR, the diagnosis of acute lumbar radiculopathy can be ruled against with relative confidence.

Traditionally, the SLR has been performed with the patient supine. The examiner moves the tested leg into hip flexion with the knee straight while noting if, and at what angle of hip flexion, pain occurs below the knee or in the low back. In theory, this maneuver causes a gliding of the nerve root at the spinal cord/neural foramen level, which in the presence of chemical inflammation or mechanical irritation will reproduce symptoms.

The classification for a positive result on this test varies slightly in the literature, but is generally accepted to be clear reproduction of the patient’s symptoms distal to the knee with abolishment of symptoms with knee flexion (this is the definition utilized in this study).

Further, LBP or thigh pain alone does not constitute a positive test.

Recently, there has been a growing trend to replace the supine SLR with a seated version. This likely emerged form the work of Waddell and colleagues, who used this test in an effort to screen for non-organic pain behaviour in LBP patients. Some clinicians have now taken to using the seated version of this test, despite little evidence suggesting it as an adequate replacement for the supine method.

This study aimed to compare the sensitivity of these two methods of performing the SLR in patients with signs and symptoms consistent with lumbar radiculopathy. Seventy-one consecutive patients with signs and symptoms of lumbar radiculopathy were included in this cohort study. Patients had to be at least eighteen years old, and have LBP with pain or paresthesia radiating into either or both lower extremities below the knee for at least four weeks.

Exclusion criteria included having spinal surgery within 6 months of study inception, far lateral disc rupture, lumbar instability requiring surgery, lumbar infection, severe disease or malignancy, and vascular disease. All patients underwent MRI and a standard clinical evaluation consisting of routine procedures (ROM, neurological examination, etc.).

SLR tests were also performed in both supine and seated position on both legs in all patients (asymptomatic side first), in addition to a group of 20 control subjects with no LBP. Statistical analysis was performed to compare the sensitivity of the two tests compared to clinical and imaging findings.

Pertinent Results:

  • 58/71 subjects had MRI findings indicating nerve root compression that correlated with clinical symptoms (the 13 without MRI findings were excluded from further analysis)
  • all 58 patients with positive MRI findings had at least one clinical finding suggestive of nerve root compression
  • sensitivity of the supine SLR was 0.67
  • sensitivity of the seated SLR was 0.41 (this difference compared to the supine SLR was significant)
  • interrater reliability for the supine SLR was 0.69 and for the seated SLR was 0.60 (substantial and moderate agreement, respectively)

Conclusions & Practical Application:

Utilizing the seated SLR may save time in assessing the patient, but this study suggests that this method may not be as effective as the traditional supine SLR. The supine SLR had a significantly higher sensitivity than the seated SLR in this study.

Further, these results suggest that previously reported sensitivity rates for the supine SLR may be overestimated. This emphasizes the importance of integrating clinical, historical, and imaging findings when making a diagnosis and determining a plan of management.

This study had a couple of weaknesses that should be considered:
  1. small sample size
  2. use of MRI as criterion standard for nerve compression (however, this was combined with at least one clinical finding in this study)
Future studies on this topic should include larger patient samples including patients with and without MRI findings. This would allow determination of specificity for the SLR in addition to sensitivity.

For now, it appears the traditional method of performing the SLR may be preferable to the seated method when assessing lumbar radiculopathy.

Additional Reference:

Deville WL et al. The Test of Lasegue: systematic review of the accuracy in diagnosing herniated discs. Spine 2000; 25(9): 1140-1147.