Intermetatarsal and Metatarsal-Phalangeal Angles Can Be Corrected by an Isolated Akin Osteotomy in Patients with Hallux Valgus Deformity

Abstract

Introduction/Purpose: Akin osteotomy is a surgical technique commonly used in conjunction with osteotomies of the first metatarsal for correction of hallux valgus (HV) deformity. The main indication for an Akin osteotomy is the presence of hallux valgus interphalangeus (HVIF), defined as a HVIF angle >10º. Given that distal osteotomies can change the tendon vector forces, we hypothesize that in a patient with a mobile medial column, an isolated akin osteotomy could improve proximally some radiologic parameters of HV. The purpose of this study was to evaluate whether the isolated Akin osteotomy is able to correct proximally the intermetatarsal angle (IMA) and hallux valgus angle (HVA) in patients with HV deformity. Methods: Case series of consecutive patients with HV deformity treated with an isolated Akin osteotomy, were included in this study. The indications for this surgery were having a mild HV and overlapping of the hallux with the second toe as the main symptom. Patients with fractures, infections, prior surgeries in the forefoot, and concomitant metatarsal osteotomy or first tarsometatarsal fusion were excluded. Two independent evaluators measured the following parameters pre and post-operatively in anteroposterior(AP) feet x-rays: traditional and modified HVA (the latter defined as angle between the long axis of the 1st metatarsal and a line from the center of the base of the proximal phalanx and the tip of the distal phalanx), IMA, distal metatarsal articular angle (DMAA), and HVIF angle. Paired t-test was performed to compare the radiological parameters pre and post- surgery. The absolute intraclass correlation coefficient (ICC) was used to determine the interobserver agreement. P< 0.05 was considered significant. Results: Twenty AP feet x-rays of 12 females and 1 male with a mean age of 44.0 years (range 15 to 85) were included in the final analysis. The preoperative mean and standard deviation (SD) of traditional HVA, modified HVA, IMA, DMAA, and HVIF were 17.0º(7.5), 23.7º(6.5), 11.3º(1.6), 12.6(9.2), and 13.5º(6.0), respectively. The corresponding postoperative values were 9.8º(7.0), 14.4º(7.0), 9.5º(2.0), 11.2º(7.6), and 9.9º(4.9). There was a significant reduction in the traditional HVA (7.2º, p< 0.001), and modified HVA (9.3º, p< 0.001). Also, there was a significant decrease in the IMA (1.8º, p< 0.001), and HVIF (3.5º, p=0.001). Conversely, the DMAA did not change after the osteotomy. The interobserver agreement was moderate to excellent for all radiologic parameters. Conclusion: In this case series, an isolated Akin osteotomy significantly reduced the HVA and IMA. These results challenge the traditional knowledge that Akin only corrects the interphalangeal angle, and could help for a better biomechanical understanding of this deformity, including the effect in proximal correction of distal procedures. An isolated Akin osteotomy could be a plausible alternative for the correction of HV, especially for mild deformities.