Ulcer occurrence on adjacent toes and hallux valgus deformity after amputation of the second toe in diabetic patients

BACKGROUND: Amputation of the second toe is associated with destabilization of the first toe. Possible consequences are hallux valgus deformity and subsequent pressure ulcers on the lateral side of the first or on the medial side of the third toe. The aim of this study was to investigate the incidence and possible influencing factors of interdigital ulcer development and hallux valgus deformity after second toe amputation. METHODS: Twenty-four cases of amputation of the second toe between 2004 and 2020 (mean age 68 ± 12 years; 79% males) were included with a mean follow-up of 36 ± 15 months. Ulcer development on the first, third, or fourth toe after amputation, the body mass index (BMI) and the amputation level (toe exarticulation versus transmetatarsal amputation) were recorded. Pre- and postoperative foot radiographs were evaluated for the shape of the first metatarsal head (round, flat, chevron-type), the hallux valgus angle, the first–second intermetatarsal angle, the distal metatarsal articular angle and the hallux valgus interphalangeal angle by two orthopedic surgeons for interobserver reliability. RESULTS: After amputation of the second toe, the interdigital ulcer rate on the adjacent toes was 50% and the postoperative hallux valgus rate was 71%. Neither the presence of hallux valgus deformity itself (r = .19, p = .37), nor the BMI (r = .09, p = .68), the shape of the first metatarsal head (r = − .09, p = .67), or the amputation level (r = .09, p = .69) was significantly correlated with ulcer development. The interobserver reliability of radiographic measurements was high, oscillating between 0.978 (p = .01) and 0.999 (p = .01). CONCLUSIONS: The interdigital ulcer rate on the first or third toe after second toe amputation was 50% and hallux valgus development was high. To date, evidence on influencing factors is lacking and this study could not identify parameters such as the BMI, the shape of the first metatarsal head or the amputation level as risk factors for the development of either hallux valgus deformity or ulcer occurrence after second toe amputation. Trial Registration: BASEC-Nr. 2019-01791