Screws versus hooks: implant cost and deformity correction in adolescent idiopathic scoliosis

To compare the costs of two spinal implants-hook and hybrid constructs and pedicle screw constructs-in posterior spinal fusion for adolescent idiopathic scoliosis (AIS) as they relate to intraoperative deformity correction.

This retrospective study examined 50 patients with AIS who were treated with posterior spinal fusion using segmental hook-hybrid constructs (23) or pedicle screws (27). Radiographic parameters measured on immediate preoperative and initial standing postoperative scoliosis films were the coronal Cobb angles of the upper thoracic, middle thoracic, lumbar, and instrumented curves; global coronal and sagittal balance; thoracic kyphosis; lumbar lordosis; and type and number of implants used. Current implant cost data were obtained from three major spinal implant manufacturers to determine the total cost of the constructs, cost per degree of correction, cost per level fused, and cost per degree of correction of the major curve.

After surgery, the average percentage of correction for the middle thoracic curve or major curve was 57 % in the hook-hybrid group compared to 73 % in the pedicle screw group (P < 0.001). The average amount of correction of the major curve was 31.1° in the hook-hybrid group compared to 42.7° in the pedicle screw group (P < 0.001). The average number of fused levels was 10.7 in the hook-hybrid group compared to 12.2 in the pedicle screw group (P < 0.001). The average number of implants was 14.8 in the hook-hybrid group compared to 23.3 in the pedicle screw group (P < 0.001). The average total cost of implants was $11,248 in the hook-hybrid group compared to $22,826 in the pedicle screw group (P < 0.001), and the average cost per fused level was $1,058 in the hook-hybrid group compared to $1,878 in the pedicle screw group (P < 0.001). The average cost per degree of correction of the major curve was $415 in the hook-hybrid group compared to $559 in the pedicle screw group (P = 0.0014). The global coronal balance, global sagittal balance, thoracic kyphosis, and lumbar lordosis did not differ significantly between the two groups.

Pedicle screw instrumentation was shown to be more expensive overall, per fused level, and per degree of correction. Also, more implants were used and more levels were fused in the pedicle screw group than in the hook-hybrid group. Pedicle screws showed a statistically significantly greater percentage of correction of the major curve. Physicians must evaluate each patient individually and determine if the increased percentage of correction warrants the increased cost for pedicle screw constructs.