Subtalar Arthroereisis as an Adjunct Procedure Improves Forefoot Abduction in Stage IIb Adult-Acquired Flatfoot Deformity

Background Our aims were (a) to determine whether subtalar arthroereisis (STA) as adjunct procedure improved radiographic correction of stage IIb adult-acquired flexible flatfoot deformity (AAFD); (b) to assess the STA-related complication rate. Methods A retrospective analysis of 22 feet (21 patients) diagnosed with stage IIb AAFD treated by medializing calcaneal osteotomy (MCO), flexor digitorum longus (FDL) transfer, spring ligament (SL) repair with or without Cotton osteotomy and with or without STA in a single institution was carried out. Seven measurements were recorded on pre- and postoperative (minimum 24 weeks) radiographs by 2 observers and repeated twice by 1 observer. Inter- and intraobserver reliabilities were assessed. The association of demographic (gender, side, age, body mass index) and surgical variables (Cotton, STA) with radiographic change was tested with univariate analysis followed by a multivariable regression model. Results Excellent inter- and intraobserver reliabilities were demonstrated for all measurements (intraclass correlation coefficient range, 0.75-0.99). Gender, side, Cotton osteotomy, and STA were included in the multivariable analysis. Regression showed that STA was the only predictor of change in talonavicular coverage angle (TNCA) (R-2 = 0.31; P = .03) and in calcaneo-fifth metatarsal angle (CFMA) (R-2 = 0.40; P = .02) on dorsoplantar view. STA was associated to a greater change in TNCA by 10.1 degrees and in CFMA by 5 degrees. Four patients out of 12 STA complained of sinus tarsi pain after STA, and removal of the implant resolved symptoms in 3 of them. Conclusion In this series, STA as an adjunct procedure to MCO, FDL transfer, SL repair in the treatment of stage IIb AAFD led to improvement in correction of forefoot abduction. STA-related complication and removal rates were 33%.