Interspinous process device versus conventional decompression for lumbar spinal stenosis: 5-year results of a randomized controlled trial.

OBJECTIVE: Interspinous process distraction devices (IPDs) can be implanted to treat patients with intermittent neurogenic claudication (INC) due to lumbar spinal stenosis. Short-term results provided evidence that the outcomes of IPD implantation were comparable to those of decompressive surgery, although the reoperation rate was higher in patients who received an IPD. This study focuses on the long-term results. METHODS: Patients with INC and spinal stenosis at 1 or 2 levels randomly underwent either decompression or IPD implantation. Patients were blinded to the allocated treatment. The primary outcome was the Zurich Claudication Questionnaire (ZCQ) score at 5-year follow-up. Repeated measurement analysis was applied to compare outcomes over time. RESULTS: In total, 159 patients were included and randomly underwent treatment: 80 patients were randomly assigned to undergo IPD implantation, and 79 underwent spinal bony decompression. At 5 years, the success rates in terms of ZCQ score were similar (68% of patients who underwent IPD implantation had a successful recovery vs 56% of those who underwent bony decompression, p = 0.422). The reoperation rate at 2 years after surgery was substantial in the IPD group (29%), but no reoperations were performed thereafter. Long-term visual analog scale score for back pain was lower in the IPD group than the bony decompression group (p = 0.02). CONCLUSIONS: IPD implantation is a more expensive alternative to decompressive surgery for INC but has comparable functional outcome during follow-up. The risk of reoperation due to absence of recovery is substantial in the first 2 years after IPD implantation, but if surgery is successful this positive effect remains throughout long-term follow-up. The IPD group had less back pain during long-term follow-up, but the clinical relevance of this finding is debatable.

Preoperative MRI in Patients With Intermittent Neurogenic Claudication: Relevance for Diagnosis and Prognosis.

STUDY DESIGN: We studied baseline magnetic resonance images of 155 patients with intermittent neurogenic claudication and lumbar spinal stenosis (LSS). Magnetic resonance imaging (MRI) and patient data were gathered from participants of a randomized trial. OBJECTIVE: It is believed that the narrowness of the lumbar spinal canal correlates to the severity of complaints and that it may be a good predictor of clinical outcome if treated. However, this hypothesis has never been (prospectively) tested. SUMMARY OF BACKGROUND DATA: MRI is an important tool to confirm the diagnosis of LSS as a cause for intermittent neurogenic claudication. METHODS: Three raters were asked to evaluate the magnetic resonance images (Schizas scale). Symptom severities at baseline and 1-year follow-up were quantified. The radiological scores were correlated with clinical baseline and outcome scores to assess diagnostic and prognostic value of MRI findings at baseline. RESULTS: There was good agreement on the clinically relevant level of LSS (kappa range 0.57-0.64). MRI assessment of grading of compression (kappa 0.33-0.46) did not correlate with baseline MRDQ nor with outcome based on postoperative change in MRDQ (P = 0.61). However, both absence of epidural fat and presence of tortuous caudal nerves on magnetic resonance images (kappa 0.53-0.72 and 0.67-0.70) in patients with LSS were relatively good predictors for satisfactory recovery after surgery (P = 0.03 and P < 0.01). CONCLUSION: The grading of compression on the preoperative MRI is neither ambiguous nor correlating to severity of clinical condition. It does, furthermore, not have the ability to predict the outcome after 1 year if surgically treated. LEVEL OF EVIDENCE: 2.

Lumbar spinal canal dimensions measured intraoperatively after decompression are not properly rendered on early postoperative MRI.

BACKGROUND: In cases of lumbar spinal stenosis (LSS) treated with surgical decompression, a postoperative magnetic resonance imaging (MRI) is sometimes required. In the experience of the investigators of this study, the obtained decompression observed on early postoperative MRI tends to be disappointing compared to the decompression achieved intraoperatively. This raises the question of whether the early postoperative MRI, performed after lumbar decompression, is a fair representation of the 'real' decompression. This study investigated the correlation between intraoperative and postoperative measurements of the lumbar spinal canal. METHOD: Twenty patients with LSS underwent surgical decompression on a single level. The orthopaedic surgeon performed direct intraoperative measurements of width, length and height of the spinal canal. Preoperative supine MR images and postoperative prone and supine MR images were acquired. Two radiologists (R.B. and M.G.) measured width, length and height of the spinal canal on the preoperative and postoperative MRIs. Intraoperative measurements were compared to measurements on postoperative MRI in prone position (thus reproducing the intraoperative situation) to avoid positioning bias. Preoperative and postoperative measurements on MR images were also compared. In addition to this, postoperative measurements on supine and prone MR images were also compared. RESULTS: Interobserver reliability for MRI measurements by both radiologists was generally excellent (intraclass correlation coefficients ≥0.71). The postoperative spinal canal dimensions improved on both prone and supine MRI compared to the preoperative imaging (P < 0.05). Intraoperatively measured dimensions demonstrated a significantly greater height (difference 2.8 ± 3.3 [R.B.] and 1.9 ± 3.7 [M.G.]) and greater width (difference 2.1 ± 3.2 [R.B.] and 2.5 ± 2.7 [M.G.]) compared to postoperative MRI in the prone position (P < 0.05). Postoperative dural sac height was greater on the supine MRI compared to the prone MRI (P < 0.05). CONCLUSIONS: Surgical decompression of the spinal canal effectively decreases the compression of the dural sac. However, early postoperative MRI after lumbar decompression does not adequately represent the decompression achieved intraoperatively.