Loading pattern of postoperative hallux valgus feet with and without transfer metatarsalgia: a case control study

Abstract

BackgroundPostoperative transfer metatarsalgia is a common complication after hallux valgus surgeries. Shortening of the first metatarsal is traditionally thought to be the primary cause of it. However, we speculate the abnormal loading pattern during gait is the real reason. This study is to determine specific differences in the loading patterns between reconstructive hallux valgus (HV) feet with and without postoperative transfer metatarsalgia, so as to find risky loading characteristics of this complication.MethodsThirty feet with postoperative transfer metatarsalgia were recruited as pain group, while another 30 postoperative feet without pain as controls. All participants were asked to walk barefoot at self-selected speed through a plantar force measuring plate (Rs-Scan Inc.) for three times. Certain plantar load variables were recorded or calculated, and their differences between two groups were compared.ResultsFor pain group, the maximum plantar force and force time integral of the first metatarsal decrease significantly; the force time integral of the central rays (second plus third metatarsal) does not significantly differ with that in the controls, but their cumulative load percentage to the whole foot is higher. In pain group, the time point when central rays reached their peak force during the push-off is significantly later than that in controls. And the regional instant load percentage at this moment presented significantly higher for central rays, while significantly lower for the first metatarsal and the hallux compared to the controls.ConclusionsFor hallux valgus feet with postoperative metatarsalgia, the load function of the first metatarsal is obviously impaired. But for central rays, indicative difference is not reflected in either peak or cumulative load during the gait cycle, but in the instant load distribution when central rays reach their peak load. So we can conclude that whether the remaining regions can adequately share certain load during walking, especially around the time metatarsalgia often occurs, plays an unnegligible role. So surgeons should pay more attention to reconstruct a foot where load can be evenly distributed.

Impact of First Metatarsal Shortening on Forefoot Loading Pattern: A Finite Element Model Study

“…The loading ratio of the central rays increased up to 54.8% when the first metatarsal was shortened by 6 mm. This is close to the 55% that is thought to be a risky threshold based on previous studies (8).…”

“…following the osteotomy procedure. In addition, the risk of metatarsalgia raises substantially when the central ray plantar loading ratio reaches 55% (8). Thus, when first metatarsal shortening reaches a certain extent (the central ray plantar loading ratio exceeds 55%), the distal end of the first metatarsal will be compensatively pushed down by 3 mm before being surgically fixed to the proximal part.…”

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

“…The basic biomechanical abnormality for transfer metatarsalgia is manifested as an alteration of forefoot loading pattern. A previous study by Geng et al [8] on post-osteotomy patients showed that the risk of metatarsalgia increased substantially when the plantar loading ratio of the central rays reached 55% in the push-off phase during gait. Therefore, this study focuses on the effect of magnitudes of the first metatarsal shortening on the plantar pressure distribution during push-off.…”

“…In order to validate its effectiveness, we also simulated the “pushing down motion” following the osteotomy procedure. In addition, the risk of metatarsalgia raises substantially when the central ray plantar loading ratio reaches 55% [8]. Thus, when first metatarsal shortening reaches a certain extent (the central ray plantar loading ratio exceeds 55%), the distal end of the first metatarsal will be compensatively pushed down by 3 mm before being surgically fixed to the proximal part.…”

“…More recently, Geng et al [8] found that abnormal loading patterns on the forefoot were the direct reason for transfer metatarsalgia. Using the plantar pressure data, they defined a loading ratio of the central rays to the whole forefoot: The foot was considered to be at high risk for transfer metatarsalgia whenever this ratio exceeds 55% during the push-off phase.…”