Transpedicular instrumentation and short-segment fusion of thoracolumbar fractures: a prospective study using a single instrumentation system.

Eleven patients were prospectively treated with bilateral short-segment transpedicular instrumentation using the Posterior Segment Fixator (Ace Medical Co., Los Angeles, CA, U.S.A.) construct combined with posterolateral fusion using autogenous iliac crest bone graft for the treatment of thoracolumbar vertebral fractures. All patients were evaluated clinically, radiographically, and functionally for a minimum of 2 years (mean 33 months). Four of the 11 patients (36.3%) had breakage or disengagement of the caudad screws during this interval. During the follow-up period, the angle of kyphosis increased an average of 12.9 degrees. The loss of correction was greater in those patients in whom the instrumentation failed (22 degrees) than in those patients in whom it did not (7.7 degrees). Five of the patients (45.5%) had a progressive increase in the angle of kyphosis of 10 degrees or more. At follow-up, the average loss of anterior vertebral body height for all 11 patients was 14% when compared with the body height that had been attained at surgery. Six of these patients (54.5%) had 10% or more loss of anterior body height. Despite the high incidence of failure of the instrumentation, progressive increase in the angle of kyphosis, and progressive loss of anterior vertebral body height, there was no worsening in the patients' Frankel grade postoperatively. The high rate of hardware failure and major postoperative loss of fracture reduction associated with this construct suggest that posterior short-segment pedicle-screw instrumentation with the Posterior Segment Fixator was not adequate to ensure stabilization of thoracolumbar fractures in this small group of patients. Maintenance of postoperative fracture reduction was the most consistent predictor of satisfactory functional outcome.