Comparative analysis of hook, hybrid, and pedicle screw instrumentation in the posterior treatment of adolescent idiopathic scoliosis.

BACKGROUND: Spinal instrumentation in adolescent idiopathic scoliosis (AIS) aims to correct spinal deformity and maintain long-term spinal stability until bony healing is ensured. The purpose of this study was to compare the minimum 2-year postoperative radiographic and clinical results of posterior spine correction and fusion with all-hook instrumentation versus hybrid segmental instrumentation versus pedicle screw instrumentation for AIS from a single institution.
METHODS: A total of 105 patients with AIS who underwent a posterior spinal fusion with segmental pedicle screw (35), hook (35), or hybrid (35) instrumentation were sorted and matched according to the following criteria: similar age at surgery, identical Lenke curve types, curve magnitude, and Risser grade. Patients were evaluated before, immediately after, and at 2 years after surgery for radiographic parameters, complications, and outcome, as well as on the basis of the Scoliosis Research Society (SRS) questionnaire.
RESULTS: The age and Risser grade, major curve Cobb angle, apical vertebral rotation (AVR), apical vertebral translation (AVT), lowest instrumented vertebral tilt, global coronal and sagittal balance, lumbar lordosis, and thoracic kyphosis were determined as part of preoperative evaluation. All 3 groups showed significant differences between the preoperative and postoperative major curve Cobb angle, lowest instrumented vertebral tilt, AVT, and AVR. At the latest follow-up, lumbar lordosis, thoracic kyphosis, and global coronal and sagittal balance remained similar among the 3 groups. Major curve Cobb angle, AVT, and AVR were significantly different--the hook group's measurements were significantly higher than the other groups, but there was no difference between the pedicle screw and hybrid groups. Major curve correction rate was significantly different among all groups (screw=71.9%±13.8%, hybrid=61.4%±16.6%, hook=48.1%±19.7%) (P<0.001). The pedicle screw group had the least amount of correction loss but there was no statistically significant difference between groups (screw=2.6±6.7 degrees, hybrid=4.5±7.4 degrees, hook=4.4±6.2 degrees) (P=0.35). The hook group had the least amount of AVT correction, but the screw group and the hybrid groups were similar (pedicle=67.3%±15.5%, hybrid=57.5%±22.4%, hook=39.9%±32.5%) (P<0.001). Surgery time and blood loss were higher in the screw group. No differences in global SRS-22 scores were demonstrated between the patients treated with pedicle screw, hybrid, and hook constructs; however, the satisfaction domain was higher in the screw group at the latest follow-up.
CONCLUSIONS: Pedicle screw and hybrid instrumentations offer significantly better spinal deformity correction than hook constructs in major curve coronal correction, AVT, and AVR. Patients with pedicle screw instrumentation had the greatest curve correction percentage, maintenance of this correction in the coronal and sagittal planes, and higher patient satisfaction by the SRS outcome scores. Global SRS-22 scores were similar at 2-year follow-up in all groups. LEVEL OF EVIDENCE: Therapeutic level III retrospective comparative study.