Risk factors for construct/implant related complications following primary posterior hemivertebra resection: Study on 116 cases with more than 2 years' follow-up in one medical center.

BACKGROUND: Posterior hemivertebra resection has become a safe and effective procedure for congenital scoliosis due to hemivertebra. However, there are still complications following primary posterior hemivertebra resection in recent reports. No risk factors associated with construct/implant related complications were identified so far. The purpose of this study is to analyze complications following primary posterior hemivertebra resection and to investigate the possible risk factors associated with construct/implant related complications in congenital scoliosis cases due to hemivertebra.

METHODS: One hundred and sixteen congenital scoliosis cases with hemivertebra (male: female = 62:54), who underwent primary posterior hemivertebra resection from January 2003 to January 2012 in our medical center, were retrospectively evaluated in this study. Medical records were reviewed and long cassette standing spinal radiographs were measured before surgery, after surgery and at the final follow-up. Complications, including construct/implant related complications and non-construct/implant related ones, were recorded by chart review. Potential risk factors, including sex, age, segmental and main scoliosis and their correction rates, usage of cage (yes or not), fusion levels (bisegmental fusion or not), location of hemivertebra and contralateral bar/rib synostosis (with or without), were also collected.

RESULTS: The mean age of initial surgery was 9.8 years old (range, 2-19 years), and the average follow-up was 67 months (range, 24-133 months). The segmental scoliosis was corrected from 34.7° ± 11.9° to 7.1° ± 5.6° post-operatively, and 9.5° ± 7.0° at the latest follow-up, with a correction rate of 79.5 %. The total main scoliosis was corrected from 43.0° ±15.6° to post-operative 11.4° ± 6.8°, and 13.9° ± 7.5° at the latest follow-up, with a mean correction rate of 73.5 %. Complications occurred in 11 out of 116 cases (9.5 %), including 7 (63.6 %) construct/implant related complications (two pedicle misplacement, one rod breakage and four implant removals due to screw dislodgement with the growth) and 4 (36.4 %) non-construct/implant related ones (one proximal adjacent kyphosis, one progressive kyphosis, and two wound non-union). Younger age (≤5 years old), lumbar hemivertebra resection, or bisegmental fusion may contribute to a higher prevalence of construct/implant related complications than other cases, although the number of cases was too small to perform statistical analysis.

CONCLUSIONS: The occurrence of construct/implant related complications in patients with hemivertebra resection is most likely multifactorial. Cases with younger age, bisegmental fusion, or lumbar hemivertebra may increase the risk of construct/implant related complications. Measures, such as careful preoperative evaluation and surgical plan with CT scan, sophisticated operation during surgery, usage of cage or cross-links to improve postoperative instant stability, protection in brace and regular follow-up postoperatively, should be taken to reduce construct/implant related complication rate.