Comparative analysis of pedicle screw versus hook instrumentation in posterior spinal fusion of adolescent idiopathic scoliosis

Yongjung J Kim, Lawrence G Lenke, Samuel K Cho, Keith H Bridwell, Brenda Sides, Kathy Blanke
Spine 2004 September 15, 29 (18): 2040-8

STUDY DESIGN: A retrospective matched cohort study.

OBJECTIVE: To comprehensively compare the 2-year postoperative results of posterior correction and fusion with segmental pedicle screw instrumentation versus those with hook constructs in adolescent idiopathic scoliosis (AIS) treated at a single institution.

SUMMARY OF BACKGROUND DATA: Despite the reports of satisfactory correction and maintenance of scoliotic curves by pedicle screw instrumentation compared to hook constructs, few reports on the comprehensive comparison of segmental pedicle screw instrumentation versus hook instrumentation exist.

MATERIALS AND METHODS: A total of 52 patients with AIS at a single institution who underwent a posterior spinal fusion with segmental pedicle screw (26) or hook (26) instrumentation were sorted and matched according to four criteria: similar age at surgery (14.8 years in pedicle screw group and 14.2 years in hook group), identical Lenke curve types, same number of fused vertebrae (11.7 in each group), and identical operative methods (18 posterior spinal fusions with thoracoplasty, 4 posterior spinal fusions with iliac crest bone graft, and 4 anterior and posterior spinal fusions in each group). Patients were evaluated before surgery, immediate after surgery, and at the 2-year follow-up according to radiographic changes in curve correction, pulmonary function tests, operative time, intraoperative blood loss, implant costs, and SRS-24 scores.

RESULTS: After surgery, the average major curve correction was 76% in the screw group and 50% in the hook group (P < 0.001). At the 2-year follow-up, loss of the major curve correction was less in the screw group (5.4%) compared with the hook group (8.0%) (P = 0.35). Postoperative global coronal and sagittal balance was similar in both groups. An average of 0.8 levels from the distal end vertebra was saved using pedicle screws compared with hook constructs (P = 0.002). Postoperative 2-year proximal junctional change in the sagittal plane (angle between uppermost instrumented vertebra and two vertebral bodies above the uppermost-instrumented vertebra) was 9 degrees in the screw group and 6 degrees in the hook group (P = 0.19). Postoperative 2-year distal junctional change in the sagittal plane was similar in both groups. Operative time averaged 341 minutes in the screw group and 338 minutes in the hook group (P = 0.86), and intraoperative blood loss was similar in both groups (879 mL in screw group vs. 896 mL in hook group) (P = 0.12). Average implant cost in the hook group (11.8 fixation points; 5,816 U.S. dollars) was significantly lower than that of the screw group (17.1 fixation points; 11,508 U.S. dollars) (P < 0.001). Two years following surgery, the screw group demonstrated improved percent predicted pulmonary function values compared with that of the hook group (FVC, 80%--> 79% in screw group vs. 82%--> 74% in hook group, P = 0.0056; FEV-1, 73%--> 76% in screw group vs. 80%--> 79% in hook group, P = 0.017). Postoperative 2-year SRS-24 scores were similar in both groups (screw group [97] vs. hook group [101]) (P = 0.15). There were no neurologic or visceral complications related to hook or pedicle screw instrumentation.

CONCLUSION: Pedicle screw instrumentation, although more expensive, offers a significantly better major and minor curve correction without neurologic problems and improved pulmonary function values in the operative treatment of AIS and enables a slightly shorter fusion length than segmental hook instrumentation.

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