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Study design: A retrospective evaluation of screw position after double rod anterior spinal fusion in idiopathic scoliosis using computerised tomography (CT).

Objective: To evaluate screw position and complications related to screw position after double rod anterior instrumentation in idiopathic scoliosis.

Summary of Background Data: Anterior instrumentation and fusion in idiopathic scoliosis is gaining widespread use. However, no studies have been published regarding the accuracy of screw placement and screw related complications in double rod and double screw anterior spinal fusion and instrumentation in idiopathic thoracolumbar scoliosis surgery.

Methods: CT examinations were performed after anterior spinal fusion and instrumentation in 17 patients with idiopathic scoliosis. The vertebral rotation at each level was measured. At each instrumented level the position of the screw and the plate relative to the spinal canal, relative to the neural foramen and relative to the aorta was measured. Complications related to screw position were registered.

Results: 189 screws in 17 patients were evaluated. The average age of the patients was 31 years (range 15–53 years). Fourteen patients had a left convex thoracolumbar curve and three patients a right convex thoracolumbar curve. The mean lumbar apical rotation preoperatively was 27°. Malposition occurred in 23% of the total number of screws. Three screws were in the spinal canal (1%). This resulted in pain in the right leg. However, electromyography showed no abnormalities. On three levels there was contact between the instrumentation and the aorta. No vascular complications did occur. 113 screws (ten patients) were placed under fluoroscopic guidance and 76 screws (seven patients) were placed without use of fluoroscopy. No complications related to screw position were observed in the group in which the screws were placed under fluoroscopic guidance.

Conclusions: Adequate placement of two screws in the vertebra in idiopathic scoliosis is a technically demanding procedure, which results in frequent malposition, fortunately with a low risk of neurological and vascular complications.

Correspondence should be addressed to Jeremy C T Fairbank at The Nuffield Orthopaedic Centre, Windmill Road, Headington, Oxford OX7 7LD, UK