Radiographic Changes and Recorded Complications After Nonabsorbable Endosinotarsal Screw Arthroereisis for Symptomatic Pediatric Flexible Flatfoot: A Retrospective Cohort Study

Background: Subtalar arthroereisis is used for selected children with symptomatic flexible flatfoot that persists despite nonoperative management, but published evidence is limited by heterogeneous indications and frequent failure to account for bilateral observations. This study evaluated radiographic change and the complications recorded after nonabsorbable endosinotarsal screw arthroereisis. Methods: We retrospectively reviewed consecutive patients aged 8–15 years treated at a tertiary pediatric orthopedic center between 2018 and 2024. Eligible patients had symptomatic flexible planovalgus deformity, failure of at least 6 months of conservative treatment, isolated screw arthroereisis, and complete weight-bearing radiographs obtained preoperatively and at 12 months postoperatively. Meary’s angle, the Costa–Bertani angle, Kite’s angle, and calcaneal pitch were analyzed using linear mixed-effects models with repeated observations at the foot level nested within patients. Results: Seventy-four patients (141 feet) were included in the outcome analysis; 67 patients (90.5%) underwent bilateral procedures. Mean age was 11.5 ± 1.6 years, and radiographic outcomes were assessed at 12 months in all patients; mean clinical follow-up was 18.3 ± 3.7 months. Interobserver reliability was good to excellent. Meary’s angle decreased from 19.0° ± 8.5° to 7.7° ± 5.6° (p < 0.001). The Costa–Bertani angle decreased by 9.0° (p < 0.001), Kite’s angle by 5.5° (p < 0.001), and calcaneal pitch increased by 1.7° (95% CI, 1.0 to 2.4; Holm-adjusted p = 0.001). Sinus tarsi pain occurred in 13 patients (17.6%) and resolved conservatively in 11. Implant removal was required in two patients (2.7%), and one patient underwent reoperation for loss of correction (1.4%). No deep infection or neurovascular injury was recorded. Conclusions: Nonabsorbable endosinotarsal screw arthroereisis was associated with radiographic improvement at the standardized 12-month assessment. Major recorded adverse events and reoperations were uncommon among the patients with available follow-up, whereas residual sinus tarsi pain was recorded in approximately one in six patients, and the implant was not removed in 97.3% of patients. The postoperative mean values indicate partial correction rather than uniform radiographic normalization. Because patient-reported and functional outcomes were unavailable, clinical benefit cannot be inferred from angular changes alone.