Apical Sublaminar Wires versus Pedicle Screws - Which Provides Better Results for Surgical Correction of Adolescent Idiopathic Scoliosis?

• a, d, e - Medtronic Sofamor Danek

Introduction: Despite the reports of satisfactory correction of scoliotic curves by both apical sublaminar wire instrumentation and apical pedicle screw instrumentation, no reports on the comprehensive comparison of hybrid (hook/sublaminar wire/pedicle screw) instrumentation versus segmental pedicle screw instrumentation exist.

Objective: To comprehensively compare the 2-year minimum postoperative results of posterior correction and spinal fusion (PSF) using translational correction through either hybrid hook/apical sublaminar wire/pedicle screw constructs (SLW) versus in-situ rod-contouring correction with pedicle screw constructs (PS) in the treatment of adolescent idiopathic scoliosis (AIS) at two institutions.

Materials and Methods: 50 AIS patients at two institutions who underwent a posterior spinal fusion with SLW (25) or PS (25) constructs were sorted and matched according to four criteria; similar age at surgery (14.2 years - SLW and 14.4 years - PS, p=0.72), similar number of fused vertebrae (11.4 - SLW and 11.8 - PS, p=0.24), similar operative methods (PSF alone, n=22; PSF with thoracoplasty, n=18; and combined anterior and PSF, n=10), identical Lenke curve types, and similar preop major curve measurements (63.5º- SLW, 59.5º - PS, p=0.42). Patients were evaluated preop, immediate postop, and at 2 year follow-up according to radiographic changes in curve correction, operative time, intraoperative blood loss, implant costs, and SRS-24 scores.

Results (See table): Postoperatively, the average major curve correction was 67.4% in the SLW group and 68.1% in the PS group (p=0.50). At 2-year follow-up, loss of major curve correction was 4.6% in the SLW group compared to 5.1% in the PS group (p=0.79). Postoperative global coronal and sagittal balance were similar in both groups. No significant difference was found in the average number of levels fused from the distal end vertebra (1.48 - SLW and 0.64 - PS, p=0.21). Postoperative 2-year proximal junctional change in the sagittal plane (angle between uppermost instrumented vertebra and two vertebral bodies above the UIV) was 9.5º in the SLW group and 12.2º in the PS group (p=0.11). Postoperative 2-year distal junctional change in the sagittal plane was similar in both groups. Operative time averaged 350 minutes in the SLW group and 357 minutes in the PS group (p=0.86). Intraoperative blood loss was significantly different in both groups (1791±816 mL in SLW group and 824±440 mL in PS group) (p=0.0003). Average implant cost in the SLW group (16.0 fixation points; 8341 USD) was significantly lower than that of the PS group (17.1 fixation points; 13,462 USD) (p<0 .0001). Postoperative 2-year SRS 24 scores were similar in both groups (SLW group="103.5," PS p="0.19)." There no neurologic or visceral complications related to SLW instrumentation and re-operations at a minimum follow-up.

Conclusion: Apical SLW and PS instrumentation both offer similar major curve correction with similar fusion lengths without neurologic problems in the operative treatment of adolescent idiopathic scoliosis. Although more expensive, PS constructs had significantly less blood loss than the SLW constructs.

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