LUMBAR AND THORACIC SCREWS FOR SCOLIOSIS INSTRUMENTATION: RESULTS WITH 50 CASES OF SCOLIOSIS

Abstract

Purpose: We present our experience with thoracic and lumbar pedicular screws for surgical correction of thoracic scoliosis.

Material and methods: Fifty patients with idiopathic scoliosis (mean age 20 years), underwent instrumentation with Moss Miami long-arm polyaxial pedicular screws. The point of entry into the pedicule was identified by progressive probing. Results were analysed at a mean follow-up of 3.5 years.

Results: Mean angle of the main instrumented curvature was 54° preoperatively and 14° postoperatively (75% initial reduction, 53% bending), and 15° at last-follow-up (74% correction). The non-instrumented lumbar curvature improved from 34° to 10°, giving a spontaneous correction of 72° (49° bending) at last follow-up. Inclination of of the first non-instrumented vertebra was 11° preoperatively and 6° at last follow-up. Kyphosis was improved in all cases with a mean gain of 10° for kyphotic spines.

Discussion: Morphological correction of scoliosis deformation and the long-term outcome depend on the quality of the initial reduction. Monitoring the spinal cord during the procedure enables best quality reduction.

In the frontal plane, corrections with hooks have varied from 38% to 55% depending on the series. This percentage improves to 60% when the lumbar curvature is instrumented with screws. Like Suk and Harms, we have found greater than 70% correction when the entire curvature is screwed using lumbar and thoracic pedicular screws. In the sagittal plane, results of hook instrumentations have been less than satisfactory for many authors (Betz, Rhee...). The improvement obtained with pedicular screws results from two effects: the stability of the construct which remains stable during reduction manœuvres allowing application of strong force, and the polyaxis arrangement allowing inserting the rods in all the screws simultaneously and thus distributing the reduction forces. The long-arm screws are brought into contact with the rod progressively by tightening the nuts bringing the vertebrae into line with the rod. We have not had any complication after insertion of 550 screws. We have not used distraction which we consider dangerous for the neurological structures nor contraction at the thoracic stage which induces lordosis.

Conclusion: The stability of the pedicular screw instrumentation for scoliosis allows clear improvement in the quality of the reduction.