[Optoelectronic gait analysis after metatarsophalangeal arthrodesis of the hallux: fifteen cases]. / Analyse opto-électronique de la marche après arthrodèse métatarso-phalangienne de l'hallux: à propos de 15 cas.

ABSTRACT

PURPOSE OF THE STUDY Degeneration of the metatarsophalangeal joint of the hallux is a frequent secondary lesion of the first ray subsequent to hallux valgus. Different surgical techniques have been proposed for cure, including metatarsophalangeal arthrodesis. Joint fusion relieves pain but sacrifices joint motion. The purpose of this work was to assess changes observed in gait after metatarsophalangeal arthrodesis of the hallux using a three-dimensional optoelectronic system. MATERIAL AND METHODS: Gait analysis was performed with a Vicon 3D system with five cameras and two AMTI force platforms in twelve patients who had undergone metatarsophalangeal arthrodesis more than six months earlier. The kinetic and kinematic curves and ground reaction forces were analyzed. Changes in the gait cycle and any compensations observed in the talocrural and interphalangeal joints were noted in the three dimensions. Wilcoxon test for paired series was applied for the statistical analysis. RESULTS: The general gait parameters and kinetic and kinematic values were not modified (excepting a non-significant decline in maximal dorsiflexion of the ankle joint). There was a significant decrease in propulsion force in the anteroposterior and vertical planes, with significantly later heal lift-off and systematic displacement of ground reaction forces anterior to the metatarsophalangeal joint on the arthrodesis side. Reflectors positioned on the distal extremity of the hallux demonstrated that the essential part of compensation occurred at the level of the interphalangeal joint. DISCUSSION: Gait analysis after tibiotalar arthrodesis has been widely reported in the literature. The consequence of joint fusion on the rear foot and/or the torsion couple have also been studied. However, to our knowledge, there has been only one report using a different methodology devoted to metatarsophalaneal arthrodesis of the hallux. In this study, only step length and interphalangeal moment as well as ankle force were found to be decreased. Function of the interphalangeal joint was not assessed. The Vicon system enabled an adapted study of gait after metatarsophalangeal arthrodesis. This method offers several perspectives study of the effect of the position of the arthrodesis in the sagittal plane on gait, changes over time in interphalangeal joint motion, or consequences of fusion on walking up and down stairs. CONCLUSION: Metatarsophalangeal arthrodesis of the hallux does not modify general gait parameters nor the kinetic and kinematic values. Compensation is achieved via the interphalangeal joint.