Curve Behavior of Distal Segments After Posterior-Only Hemivertebra Resection for Congenital Cervicothoracic Scoliosis.

Study design: A retrospective and consecutive study.

Objective: To demonstrate the curve evolution of distal non-structural compensatory curves in patients with congenital cervicothoracic hemivertebra (CTH) scoliosis undergoing posterior-only hemivertebra resection and to propose the possible mechanisms of this specific phenomenon.

Summary of background data: Though the spinal alignment could be well corrected via posterior hemivertebra resection in CTH patients, the high prevalence of distal curve progression was remarkable. However, the curve behavior of distal non-structural compensatory curves and its possible mechanisms were unclear.

Methods: This study retrospectively reviewed a consecutive series of CTH patients undergoing posterior-only hemivertebra resection with a minimum 24 months follow-up. The parameters measured in coronal plane included local scoliosis, clavicle angle, head shift, and the Cobb angle of distal unfused segments. The distal curve was considered as an emerging scoliosis (ES) if with more than 20° progression and the apex of distal curve no less than 2 levels away from the lower instrumented vertebra.

Results: A total of 51 CTH patients with a mean age of 8.5 ± 3.8 years at surgery and a mean 38.0 ± 5.3 months follow-up were recruited. The correction of local scoliosis and clavicle angle was statistically significant (p < 0.05 for all). The distal compensatory curve was 11.8 ± 5.3° before surgery and 6.5° ± 4.1° after surgery (p < 0.001), which was slightly increased to 11.6° ± 10.9° (p = 0.002) at the latest follow-up. During follow-up, the increase of distal compensatory curve was significantly correlated with the change in clavicle angle (r = 0.49, p = 0.038). The ES was observed in 10 patients (19.6%) with an average value of 28.0 ± 2.1° at diagnosis, including 7 patients within 6 months and 3 patients after 5 years postoperatively. The mean value of ES was 31.9° ± 3.1° at the latest follow-up, while no patients required revision surgery. The ES was classified into compensatory and idiopathic types according to the typical curve behaviors. The compensatory ES usually presented within 6 months after operation and was responsible for further reconstruction of head and shoulder balance. While the idiopathic ES occurred at adolescent which may be related to the rapid body growth.

Conclusions: Distal compensatory curve had a tendency toward slight progression during follow-up in CTH patients with posterior hemivertebra resection surgery. The prevalence of emerging scoliosis was 19.6% and the typical compensatory and idiopathic curve behavior were firstly proposed. Close and longitudinal follow-up was thus highly recommended for CTH patients with posterior HV resection surgery.