Abstract
Hypothesis
Lumbar spinal stenosis (LSS) is diagnosed by a history of claudication, clinical investigation, cross-sectional area (CSA) of the dural sac on MRI or CT, and walking distance on the treadmill test. As radiological findings do not always correlate with clinical symptoms, additional diagnostic signs are needed. In patients without LSS, we observe the sedimentation of lumbar nerve roots to the dorsal part of the dural sac on supine MRI scans. In patients with LSS, this sedimentation is rarely seen. We named this phenomenon ‘sedimentation sign’ and defined the absence of sedimenting nerve roots as positive sedimentation sign for the diagnosis of LSS. We hypothesised that the new sedimentation sign discriminates between non-specific low back pain (LBP) and LSS.
Methods and analysis
This prospective case-control study included 200 patients in an orthopaedic in- and outpatient clinic. Patients in the LBP group (n=100) had low back pain, a cross-sectional area (CSA) of the dural sac >120mm2, and a walking distance >1000m; patients in the LSS group (n=100) showed claudication, a CSA < 80mm2, and a walking distance < 200m.
Results
A positive sedimentation sign was identified in 94 patients in the LSS group but in no patient in the LBP group. There was no difference in the detection of the sign between segmental levels L1 - L5 in the LSS group.
Conclusion
Our findings show that a positive sedimentation sign exclusively and reliably occurs in patients with LSS, suggesting its usefulness in clinical practice. If future accuracy studies confirm the sign's high specificity, a positive sedimentation sign can rule in LSS, and with a high sensitivity, a negative sedimentation sign can rule out LSS. The sedimentation sign is potentially a valuable tool to identify patients who will benefit from spinal surgery.
