Hybrid constructs versus all pedicle screw instrumentation for treatment of thoracic scoliosis secondary to Chiari malformation in adolescents

Objective To compare the clinical and radiological outcomes between hybrid and total pedicle screw instrumentation in adolescents undergone posterior spinal fusion (PSF) for thoracic scoliosis secondary to Chiari malformation..Methods A total of 75 patients undergone PSF were included and divided into two groups:the all pedicle screw group (Group A,n=44) and the hybrid group (Group B,n=31).Patients were evaluated before surgery,immediately after surgery,and at the 2-year follow-up in radiographic changes in curve magnitude,apical vertebral translation (AVT),apical vertebral rotation (AVR),trunk shift,thoracic kyphosis (TK),lumbar lordosis (LL),and sagittal vertical axis (SVA).These parameters were further analyzed with respect to preoperative TK in both groups.Results After surgery,the average correction of the thoracic curve was 60.2％ and 51.3％ in Group A and B,respectively (t=2.372,P=0.023).The average lumbar curve correction was 61.7％ in Group A,representing a significant increase compared to Group B (51.1％,t=2.431,P=0.020).At the final follow-up,loss of the thoracic curve correction was less in Group A (0.3％) than in Group B (1.7％),however,there was no statistical significance (t=-0.468,P＞0.05).AVT of the thoracic curve improved in Group A from 25.0 mm to 6.9 mm,while in Group B it changed from 24.1 mm to 7.4 mm.For patients with a preoperative TK greater than 40°,the proximal junctional angle was found to be significantly larger in Group A (10.0 degrees versus 4.5 degrees,t=-2.031,P=0.052) by the final follow-up,along with a significantly increased incidence of proximal junctional kyphosis (20％ versus 9％).Conclusion Total pedicle screw instrumentation provided a significantly better correction of the major and minor curves than hybrid constructs for the operative treatment of thoracic scoliosis secondary to Chiari malformation.However,for patients with thoracic hyperkyphosis,all-screw instrumentation had a higher risk of adjacent level proximal kyphosis. Key words: Arnold-Chiari malformation;  Thoracic vertebrae;  Scoliosis;  Spinal Fusion;  Internal Fixators