[Surgery for degenerative spondylolisthesis of the lumbar spine using intra-articular fusion. A prospective study].

PURPOSE OF THE STUDY: The aim of the study is to present our surgical method of treating degenerative spondylolisthesis, which includes radical bilateral laminectomy to relieve compression on the spinal cord, transpedicular fixation of the segment and arthrodesis by bilateral intra-articular fusion.

MATERIAL AND METHODS: This surgery was indicated in patients with grade I or grade II of degenerative sponylolisthesis with a 4-mm or more slippage. Our prospectively studied group consisted of 46 patients (17 men, 29 women; average age, 64.2 years; range, 39-84 years). Before surgery and at 1 year after the procedure, the intensity of axial pain and that of radicular pain were each assessed using the visual Analogue Scale (VAS). Difficulty in performing daily living activities was measured by the Oswestry Disability Index (ODI). The surgical procedure included laminectomy, partial medial facetectomy, foraminotomy to relieve pressure on the spinal nerve roots and transpedicular fixation to provide stability. Using a cutter, cartilage was separated off the cortical bone and, in order to facilitate fusion, bone cavities thus produced were filed with corticospongious grafts harvested from the removed vertebral arch with Kerrison forceps. At 1-year follow-up, dynamic X-ray was used to evaluate spine alignment and, on a CT scan, the degree of intra-articular fusion was assessed. Fusion was achieved when bone density measurement showed more than 350 Hounsfield Units (HU). For the measurements, the authors used their own modified method by means of a Region of Interest (ROI) analysis. The clinical and radiographic results were statistically evaluated.

RESULTS: At 1 year after surgery, lumbar flexion-extension bending X-ray films revealed stability of the treated segments in all patients (100%). CT examination showed bone density higher than 350 HU at both joints, i.e., complete bone fusion, also in all 46 patients. The mean post-operative ODI score was significantly lower than its mean pre-operative value (23.6 vs 55.4), which was improvement by 57.4%. The differences in pre- and post-operative VAS scores were also statistically significant. The mean VAS score for low back pain decreased from 7.61 to 1.74, i.e., improvement by 77.1%, and the mean vAS score for radicular pain dropped from 6.98 to 1.24, i.e., improvement by 82.2%. Assessed by Odom's outcome criteria, the results were excellent in 26 patients and very good in 20 patients, and they were not related to age, gender or the spinal level treated. Any complications associated with the operative procedure or wound healing and requiring repeated surgical treatment were not recorded.

DISCUSSION: The surgical technique described here has advantages over other methods in reliable achieving nerve decompression, joint fusion and spinal stability at low costs and short operative time. In addition, it avoids the necessity of harvesting bone from the iliac crest.

CONCLUSIONS: At 1-year follow-up all patients showed better health conditions, with improvement in average scores for the ODI by 57%, for low back pain by 77% and for radicular and claudication pain by 82%. The technique of intra-articular fusion for treatment of degenerative spondylolisthesis resulted in solid bone fusion and spinal stability in all patients.