Late Implant Removal After Posterior Correction of AIS With Pedicle Screw Instrumentation-A Matched Case Control Study With 10-Year Follow-up

Study Design: Matched case-control study.

Objective: To find the amount of progression of deformity and its clinical consequences in the long term after implant removal (IR) as a result of late infection in adolescent idiopathic scoliosis (AIS).

Background Summary: Late IR is occasionally necessary after instrumented posterior correction of AIS because of late implant infection or implant-associated pain. The long-term outcome is not yet known because of the lack of studies with a comparable control group.

Methods: We observed 50 patients with AIS, who had pedicle screw instrumentation for posterior correction, for at least 10 years. Seven of these patients needed IR after 3.4 years (range, 1.1-7.9 years) years because of late implant-associated infection. We matched these patients with another 7 who had no complications (control), by curve type, Risser stage, age, and gender. We performed radiological measurements preoperatively, at 6 weeks, and 2, 5, and 10 years postoperatively. All patients completed the SRS-24 questionnaire at 2- and 10-year follow-up.

Results: Although the curve magnitude of the main thoracic curve was similar preoperatively (Cobb angle: IR, 57°±6°; control, 57°±10°) and corrected equally (IR, 18°±4°; control, 20°±7°) at 6 weeks, the deformity progressed in the IR group at 2 years (IR, 25°±11°; control, 17°±6°) and became statistically different at 10 years (IR, 31°±10°; control, 19°±6°; p<.05). There was no significant difference in total Scoliosis Research Society score between groups (IR, 99±13; control, 90±17; p>.05) at 10 years.

Conclusions: Late implant removal after posterior correction of thoracic AIS with pedicle screw instrumentation results in a loss of Cobb angle correction of about one third in coronal plane at 10-year follow-up, but without clinical relevance, as measured by the Scoliosis Research Society-24 questionnaire.