Long-term results of thoracolumbar and lumbar burst fractures after short-segment pedicle instrumentation, with special reference to implant failure and correction loss.

Objective: To assess the long-term results of short-segment pedicle instrumentation for thoracolumbar and lumbar burst fractures.

Methods:  From February 1987 to June 1995, 89 patients with thoracolumbar or lumbar burst fracture were treated with short-segment pedicle instrumentation, and 68 (76.4%) of them were followed up for an average of 8.0 years (range, 5-13 years). Radiographs were taken pre- and post- operatively, before implant removal and at final follow-up. Computerized tomography (CT) scans of the fractured vertebrae were done on 18 patients, with their consent, at final follow-up.

Results: At final follow-up, neurological status had improved at least one grade in the Frankel Grading system in 90.8% patients who had presented incomplete paralysis preoperatively, and low back pain was evaluated as Denis' P(1) in 60.3%, P(2) in 35.3% and P(3) in 4.4% of patients. An average of 2.5 mm (range, 0-6.5 mm) of implant deformation was recorded before implant removal, and implant failure was noted in 11 (16.2%) patients. At final follow-up, loss of correction of the anterior vertebral body height and Cobb angle averaged 1.9% and 12.1°, leaving residual correction rates of 30.5% and 5.8°, respectively. The loss of correction occurred mainly at adjacent disc spaces, and collapse of the vertebral body was more severe at its center. CT scan revealed an obvious gap, which communicated with the adjacent disc space, in the vertebral body of 16 of the 18 patients scanned. Local kyphosis of more than 20° existed in five patients and three of them had low back pain.

Conclusion: Short-segment pedicle instrumentation provides satisfactory reduction for thoracolumbar and lumbar burst fractures. The relatively high incidence of implant failure and the loss of correction may be caused by various factors, and more adequate fusion is recommended.