Objective: We analyzed radiological results of Swanson implant surgery for rheumatoid arthritis affecting the forefoot. Special attention was paid to the incidence of recurrent hallux valgus deformity. Factors affecting such recurrences were analyzed.
Methods: Postoperative radiological results with a minimum follow-up period of 12 months after surgery were analyzed in 54 cases (87 joints). The mean age at the time of surgery was 67.7 years (range, 53-84 years). The mean duration after surgery was 40.8 months (range, 12-93 months). Hallux valgus angle (HVA) and intermetatarsal M1-M2 angle (M1M2) were analyzed preoperatively, in the immediate postoperative period, at six months postoperatively, and at the final follow-up. The change of HVA from the immediate postoperative period to the final follow-up was calculated as the change of HVA (ΔHVA). The toe lengths of the hallux including soft tissue shadow were divided into three groups as follows: Type E (hallux length 3 mm longer than the second toe), Type G (hallux length 3 mm shorter than the second toe), and Type S (hallux length within 3 mm of the second toe). The relationship between toe length type and radiological findings were then analyzed.
Results: The average preoperative HVA was 38.4 ± 16.5°, and the average HVA in the immediate postoperative period was 21.1 ± 10.1°, which was statistically maintained during the follow-up period. The average M1M2 showed no changes during the follow-up period. Cases whose ΔHVA were over 15° were observed in early cases in the surgical series. There was no statistical correlation between the changes of HVA and the follow-up period, preoperative HVA, or HVA in the immediate postoperative period. Type G showed significantly less changes of HVA when compared to Type E. Also, with the shortening of the length of hallux by toe length type, the HVA at the final follow-up was significantly decreased.
Conclusion: Surgical skills are needed for Swanson implant surgery for rheumatoid arthritis of the forefoot, because cases of recurrent hallux valgus have been frequently observed in early surgical series. Finally, the shortening of the length of the hallux is important for preventing recurrent hallux valgus deformity.
