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Early postoperative MRI after spinal surgery is difficult to interpret because of confounding postoperative mass effects and frequent occurrence of epidural hematomas. Purpose of this prospective study is to evaluate prevalence, extent and significance of hematoma in the first postoperative week in asymptomatic patients after decompression for lumbar stenosis and to determine the degree of clinically significant dura compression by comparing with the patients with postoperative symptoms. MRI was performed in 30 asymptomatic patients (47 levels) in the first week after lumbar spine decompression for degenerative stenosis. Eleven patients requiring surgical revision (16 levels) for symptomatic early postoperative hematoma were used for comparison. In both groups the cross-sectional area of the maximum dural compression (bony stenosis and dural sac expansion) was measured preoperatively and postoperatively by an experienced radiologist. Epidural hematoma was seen in 42.5% in asymptomatic patients (20/47 levels). The median area of postoperative hematoma at the operated level was 176 mm(2) in asymptomatic patients and 365 mm(2) in symptomatic patients. The median cross-sectional area of the dural sac at the operated level was 128.5 and 0 mm(2) in asymptomatic and symptomatic patients, respectively, at the site of maximal compression. In the symptomatic group 75% of the patients had a maximal postoperative dural sac area of 58.5 mm(2) or less, whereas in the asymptomatic group 75% of patients with epidural hematoma had an area of 75 mm(2) or more. The size of hematoma and the degree of dural sac compression were significantly larger in patients with symptoms needing surgical revision. Dural sac area of less than 75 mm(2) in early postoperative MRI was found to be the threshold for clinical significance.

Retrospective analysis of 11 consecutive patients with ankylosing spondylitis who underwent lumbar spinal osteotomy for severe kyphosis, with a mean follow up of 4 (2 to 8.5) years. The chin brow vertical angle, thigh flexion angle, and the whole body kyphosis angle (WBKA) were measured on the clinical photographs of the patient in standing. The lumbar lordosis, thoracic kyphosis, total kyphosis, sacral slope, and sagittal balance were measured on the standing radiographs. A closing wedge osteotomy at L3 was done in all patients. Intraoperative neuromonitor with sensory evoked potentials and motor evoked potentials was used routinely. Stable fixation of spine allowed early walking. There were no permanent neurologic complications. The average preoperative WBKA was 41 degrees (20 to 70 degrees). The average correction of lumbar lordosis was 40 degrees, from 21.4 degrees (-10 to 65 degrees) to 61.4 degrees (35 to 85 degrees). The thigh flexion angle improved from 9.7 degrees (4 to 20 degrees) to 0.4 degrees (-4 to 5 degrees), the sacral slope from 11.8 degrees (-5 to 35 degrees) to 31.8 degrees (20 to 45 degrees), and the chin brow vertical angle from 28.2 degrees (10 to 45 degrees) to 2.4 degrees (-5 to 18 degrees). Loss of correction of 5 and 10 degrees was seen in 2 patients. The ability to stand upright and look straight was restored in all patients. The WBKA correlated closely with the amount of lordosis correction in lumbar spine. The intraobserver and interobserver reproducibility of the WBKA was verified by statistical analysis. In our opinion the measurement of the WBKA on the preoperative photograph is helpful in planning the lumbar osteotomy.