Journal Article

Impact of first metatarsal shortening on forefoot loading pattern: a finite element model study

Geng, Xiang, Chen, Wenming, Wang, Xu, Ma, Xin, Zhang, Chao, Shi, Jiaqi, Chen, Li

2019

Overview

Backgrounds There has long been a consensus that shortening of the first metatarsal during hallux valgus reconstruction could lead to postoperative transfer metatarsalgia. However, appropriate shortening is sometimes beneficial for correcting severe deformities or relieving stiff joints. This study is to investigate, from the biomechanical perspective, whether and how much shortening of the first metatarsal could be allowed. Methods A finite element model of the human foot simulating the push-off phase of the gait was established. Progressive shortening of the first metatarsal from 2 to 8 mm at an increment of 2 mm were sequentially applied to the model, and the corresponding changes in forefoot loading pattern during push-off phase, especially the loading ratio at the central rays, was calculated. The effect of depressing the first metatarsal head was also investigated. Results With increasing shortening level of the first metatarsal, the plantar pressure of the first ray decreased, while that of the lateral rays continued to rise. When the shortening reaches 6 mm, the load ratio of the central rays exceeds a critical threshold of 55%, which was considered risky; but it could still be manipulated to normal if the distal end of the first metatarsal displaced to the plantar side by 3 mm. Conclusions During the first metatarsal osteotomy, a maximum of 6 mm shortening length is considered to be within the safe range. Whenever a higher level of shortening is necessary, pushing down the distal metatarsal segment could be a compensatory procedure to maintain normal plantar force distributions.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Analysis / Ankle / Biomechanical Phenomena - physiology / Biomechanics / Bones / Computer Simulation / Epidemiology / Finite Element Analysis / Finite element method / First metatarsal shortening / Forefoot, Human - anatomy & histology / Forefoot, Human - diagnostic imaging / Forefoot, Human - physiology / Gait / Gait - physiology / Hallux valgus / Hallux Valgus - surgery / Humans / Internal Medicine / Ligaments / Medical imaging / Medicine / Medicine & Public Health / Metatarsal Bones - anatomy & histology / Metatarsal Bones - physiology / Metatarsal Bones - surgery / Metatarsalgia - etiology / Metatarsalgia - prevention & control / Metatarsus / Musculoskeletal diseases / Orthopedic surgery / Orthopedics / Orthopedics and biomechanics / Osteotomy / Osteotomy - adverse effects / Osteotomy - methods / Plantar pressure / Postoperative Complications - etiology / Postoperative Complications - prevention & control / Postoperative Period / Pressure distribution / Rehabilitation / Research Article / Rheumatology / Sports Medicine / Studies / Surgeons / Tomography, X-Ray Computed / Transfer metatarsalgia / Weight-Bearing