To evaluate the clinical features and assess the MRI measurements of the stenosis quantitatively in patients undergoing surgery for level one lumbar stenosis. The goal of this study was to correlate MRI measurements with clinical features and define whether the measurements have prognostic value.

From October 1994 to October 1996, 31 patients with level one lumbar spinal stenosis underwent posterior decompression and posterolateral fusion with instrumentation. Average age of the patients at the time of surgery was 56 years (range, 34-77 years). There were 11 men and 20 women. Most commonly involved level was L4-L5 (29 patients). All patients were evaluated before surgery and at defined intervals of 6 weeks, 3 months, 6 months, 1 year after surgery and at last follow up. The average follow up period was 29 months (range, 19-43 months). Clinical features of the patients were back pain, radiating pain, intermittent neurogenic claudication and gross pain score. MRI measurements of the patients were measured by anteroposterior diameter of spinal canal, canal area, foraminal area and depth of lateral recess. A statistical analysis was performed with the Chi-square test and Mann Whitney test.

Patients with smaller spinal canal area (area < or = 80 mm2) showed more improvement in radiating pain than patients with large area (area>80 mm2) (P<0.05) and tendency toward improving claudication and pain score (P>0.05). Other MRI measurements did not correlate with the preoperative and postoperative clinical features.

In conclusion, spinal canal area measured on the MR image seems to have some prognostic value in patients undergoing surgery for level one lumbar stenosis.