Surgical treatment of scoliosis in osteogenesis imperfecta with cement-augmented pedicle screw instrumentation.

ABSTRACT

STUDY DESIGN: A retrospective study. OBJECTIVE: To report the early postoperative results of scoliosis surgery in osteogenesis imperfecta (OI) patients utilizing all pedicle screw constructs and present a novel cementing technique to increase pedicle screw purchase in the osteoporotic OI spine. SUMMARY OF BACKGROUND DATA Scoliosis surgery utilizing hooks and wire systems have high complication rates in OI. Pedicle screw fixation systems have the biomechanical advantage of 3-column fixation, and cement augmentation of pedicle screws provides additional pull-out strength in the osteoporotic OI spine. METHODS: The clinical and radiologic results of 10 consecutive OI patients treated with all pedicle screw instrumentation and fusion were retrospectively reviewed. The radiologic data included preoperative and postoperative major curve measurements major curve Cobb angle, global coronal balance (GCB), apical vertebral translation (AVT), and the lowest instrumented vertebral (LIV) tilt. Operative findings included blood loss, surgery time, and additional procedures. All patients received intravenous pamidronate therapy preoperatively to increase bone mineral density. RESULTS: Ten patients with OI were operated on between 2005 and 2009. Seven had cement-augmented pedicle screw insertion at the proximal and distal foundations. The mean hospital stay was 10±7.5 days (range, 4-27 d) and the average follow-up period was 25.7±13.1 months (range, 14-50 mo). Mean preoperative and postoperative major Cobb angles were 83.7±23.8 and 40.3±14.6 degrees, respectively (48% correction; P<0.05). Mean preoperative and postoperative GCB deviations were 26.7±18.6 and 14.1±13.3 mm, respectively (P=0.097). Mean preoperative and postoperative AVTs were 69.3±29.1 and 29±12.2 mm, respectively (P<0.05). Preoperative and postoperative LIV tilts were 18.5±8.9 and 5.2±3.9 degrees, respectively (P<0.05). At the latest follow-up, the mean major curve Cobb angle was 37.7±13.1 degrees, the GCB deviation was 13.8±5.1 mm, the AVT was 31.7±13.3 mm, and the LIV tilt was 11.3±8.8 degrees. There was no difference between the early postoperative and the latest follow-up major curve Cobb angle, GCB deviation, AVT, or LIV tilt, indicating maintenance of correction. The mean blood loss was 23,75 mL (range, 800-45,00 mL). The mean operative time was 375.4 minutes (range, 262-491 min). The mean postoperative Scoliosis Research Society-22 patient-based outcome scores were 4.6±0.7 (out of 5). There were no instrumentation failures or permanent neurological deficits in this series. CONCLUSIONS: Pedicle screw instrumentation in OI scoliosis is safe and effective. Cement augmentation in these patients may help to increase the pedicle pull-out strength and decrease the screw failure rates, especially at the proximal and the distal ends of instrumentation.