RETROSPECTIVE ANALYSIS OF SCREW MALPOSITION FOLLOWING INSTRUMENTED CORRECTION OF THORACIC AND LUMBAR SPINE DEFORMITIES

Abstract

Objective. To analyze cases of screw malposition following instrumented correction of deformity of the thoracic and lumbar spine. Material and Methods . Retrospective analysis of 73 patients aged 3 to 58 years with thoracic and lumbar spine deformities was performed. Deformity magnitude measured 20° to 134° by Cobb angle (mean value was 61° ± 4°). A total of 1065 screws were inserted using free-hand method for the spine deformity correction. Malposition cases were detected by postoperative CT control of screw placement. Screw malposition was graded according to the following system: A - no malposition, B - malposition less than 2 mm, C - malposition between 2 and 4 mm, and D - malposition more than 4 mm. Results . Insertion of 628 (59.0 %) transpedicular screws was performed correctly, and trajectories of 437 (41.0 %) screws were displaced. Malposition of 263 screws (24.0 %) was less than 2 mm, in 112 screws (10.5 %) it reached a safety limit of 4 mm, and in 62 screws (5.8 %) it exceeded 4 mm and was considered as dangerous with the potential for primary or delayed injury of neural structures and vessels. Conclusion . Transpedicular fixation is a method of choice for surgical correction of spine deformity. Its application is associated with a risk of neurovascular complications. The most common and available free-hand screw insertion technique is safe enough, though requires appropriate surgical skill.