A wide posterior release is associated with better kyphosis restoration in the surgical treatment of adolescent idiopathic scoliosis

PURPOSE: To examine whether the use of a wide posterior osseo-ligamentous release in adolescent idiopathic scoliosis (AIS) improves restoration of thoracic kyphosis.

METHODS: We retrospectively included a consecutive cohort of AIS patients undergoing surgical treatment involving the thoracic spine (Lenke 5 excluded) over two consecutive time periods. The first time period served as control group. In the second time period, standard surgical technique was supplemented with a wide posterior release of the lamina, spinous process and supraspinous ligaments (no removal of the inferior facet) at 4-5 levels corresponding to the apex of the thoracic curve. Patients were categorized as preoperatively hypo- or normokyphotic and intraoperative data, and 2-year postoperative radiographic data were recorded.

RESULTS: We included 191 patients. Mean age was 15.8 ± 2.3 years, and mean Cobb angle was 60 ± 12°. Sixty-two (32%) patients were classified as hypokyphotic (global kyphosis ≤ 30°) preoperatively. Baseline coronal and sagittal parameters were similar between the posterior release and control group. In the hypokyphotic group, the use of posterior release resulted in an increase in kyphosis from 19 ± 7° to 38 ± 11° vs. 22 ± 8° to 32 ± 7° in the control group (p = 0.018). 15% vs. 49% was hypokyphotic at 2-year follow-up (p = 0.020). In the preoperatively normokyphotic group, the change in kyphosis was 6 ± 9° vs - 1 ± 10° (p < 0.001) in the posterior release and control group, respectively, but with no difference in the final 2-year kyphosis (47 ± 8° vs. 46 ± 10°). Two-year major coronal Cobb angle was 28 ± 9° vs. 26 ± 9° in the posterior release and control group, respectively (p = 0.206). Median intraoperative blood loss was 500 (IQR: 412-743) ml vs. 600 (IQR: 500-900). There was one case of neurological injury in the control group and none in the posterior release group.

CONCLUSION: The use of a posterior osseo-ligamentous release results in an increased thoracic kyphosis restoration in preoperatively hypokyphotic patients without increasing blood loss or the risk of neurological injury.