RESUMO
PURPOSE: The expression "learning curve" indicates the relation between the time needed to learn a new technique and the technique-related outcome. Percutaneous surgery (also called "minimally invasive surgery") has experienced sustained and respectable growth, especially in forefoot deformities. The main purpose was to assess the number of feet necessary to become skilled in a specific minimally invasive surgery (MIS) procedure. METHODS: From January 2015 to June 2018, 46 consecutive patients were evaluated and included in the study. Patients were divided into 2 groups according to the surgery period: first 30 feet (Group 1), and subsequent 30 feet (Group 2) from the whole population evaluated. Age, body mass index, and operative time were evaluated. Hallux valgus angle and the 1 to 2 intermetatarsal angle were also measured. Patients were assessed according to the American Orthopedic Foot and Ankle Society (AOFAS) forefoot scale, the Foot and Ankle Ability Measure activities of daily living (FAAM ADL) subscale and the visual analog scale (VAS). RESULTS: The comparison of the 2 groups showed statistically significant differences in hallux valgus angle (HVA) but not in intermetatarsal angle (IMA). The mean improvement between pre- and postoperative FAAM ADL, VAS, and AOFAS score in Group 1 were 12.83, 3.93, and 24.77 points, respectively. In Group 2, the mean improvement between pre- and postoperative FAAM ADL, VAS, and AOFAS scores were 15.19, 4.3, and 24.5 points, respectively. The differences between groups in FAAM ADL score was statistically significant (P = 0.0364). Group 1 showed a global complication rate of 16.67% (n = 5) while group 2 showed 3,3% (n = 1). CONCLUSION: After the first 30 cases, radiographic, clinical, and functional outcomes substantially improved, and the level of the perioperative complications decreased. The results suggest that the learning curve plateau for performing a percutaneous subcapital osteotomy can be reached after 30 surgeries. LEVELS OF EVIDENCE: Level III.