Results of Arthroscopic Subtalar Arthrodesis for Adult-Acquired Flatfoot Deformity vs Posttraumatic Arthritis

Background: The goal of this study was to compare results with arthroscopic posterior subtalar arthrodesis between patients treated for adult-acquired flatfoot deformity (AAFD) due to posterior tibial tendon dysfunction and patients with posttraumatic subtalar arthritis. Methods: Retrospective case series of 61 consecutive patients (group 1: posttraumatic arthritis, n = 37; group 2: AAFD, n = 24) averaging 49 years of age (range, 21-72 years) undergoing posterior arthroscopic subtalar arthrodesis via 1 or 2 percutaneous 6.5- to 7.3-mm screws, with a mean follow-up of 57.5 months (range, 24-105 months). Fusion was defined as the appearance of bony trabeculae across the subtalar joint on standard x-rays, along with clinical signs of union. Results: Patients with posttraumatic arthritis (group 1) were more predominantly male and younger than patients treated for AAFD (group 2). Overall, we achieved a 95.1% radiologic union rate after an average of 11.7 weeks. Complications appeared in 14.8% of patients. Union rate and complications did not differ significantly between groups. American Orthopaedic Foot & Ankle Society (AOFAS) scores improved significantly for both patient groups, although patients with AAFD showed significantly larger improvement and higher postoperative AOFAS scores, even after adjusting for age and sex (mean improvement in AOFAS scores: 27.0 9.1 points for the posttraumatic arthritis group vs 34.9 7.4 points for the AAFD group; P < .001). Conclusions: Arthroscopic subtalar arthrodesis was a safe and reliable technique, with consistent improvement in AOFAS scores throughout different patient subgroups, as well as comparable time to union and complication rates. Improvements were larger for patients treated for AAFD, even after adjusting for age and sex. Level of Evidence: Level III, retrospective case series.