UNSTABLE THORACOLUMBAR AND LUMBAR BURST FRACTURES TREATED WITH THE AO FIXATEUR INTERNE

Twenty-five consecutive patients with unstable thoracolumbar and lumbar burst fractures were surgically treated with the AO Fixateur Interne (Synthes USA. 1690 Russell Rd., Paoli, PA). Indications for surgery included a progressive neurologic deficit. spinal canal compromise > 50%. vertebral body collapse > 50%, or sagittal angulation > 20-degrees. Twenty males and five females ranging in age from 16 to 60 years (average 31 ) were treated surgically and prospectively followed. Twenty-one fractures occurred at the thoracolumbar junction (T10-L2) and 4 in the lumbar spine (L3-5). Twenty-four patients were followed for a minimum of 12 months, ranging from 12 to 38 months (average 22); one patient was lost to follow-up after 1 month postoperatively. Preoperatively, 12 patients had partial neurologic deficits; postoperatively, 11 improved at least 1 Frankel grade. Preoperatively. the 12 patients with partial neurologic deficits averaged 45 points (range 24-49) on the lower extremity motor index scale. After surgery, these patients improved an average of five points (range 1-23) on the motor index scale. Both patients with complete spinal cord injuries remained unchanged neurologically postoperatively; no patients deteriorated neurologically after surgery. The average preoperative sagittal kyphosis at the fracture site was +16-degrees (range +10-degrees to +31-degrees); the immediate postoperative sagittal angular correction averaged -4-degrees (lordosis) and ranged from +12-degrees (kyphosis) to -26-degrees (lordosis). At last follow-up. the sagittal angular correction remained unchanged in three patients and decreased in 21 patients to an average of +5-degrees (range +37-degrees to -14-degrees). Fifteen patients underwent both preoperative and postoperative computed axial tomographic (CAT) scanning. Preoperatively, the average canal compromise was 42% (range 19-68%); postoperatively, the canal compromise was reduced to an average of 28% (range 2-68%). CAT scans were not performed after implant removal. Complications occurred in seven patients. a single pedicle screw broke in five patients. two patients had late deep infections, and one patient had loss of fixation. No pseudarthroses occurred. The AO fixateur interne is a safe and effective pedicular fixation device that allows for correction of the kyphosis and spinal canal compromise resulting from unstable burst fractures in the thoracolumbar and lumbar spine. The initial correction of the traumatic sagittal plane deformity was not maintained and deteriorated over time despite a solid posterior arthrodesis. However, this radiographic finding did not affect the long-term clinical and neurologic outcomes.