Biomechanics of Midfoot Charcot Neuroarthropathy in People with Diabetes

Introduction: Charcot neuroarthropathy (CN) is a rare complication of diabetic foot disease which provides many challenges for clinicians. Progressive destruction of bone and soft tissue occurs at the site of weight bearing joints resulting in significant disruption of the bony architecture. There is very little reported biomechanical data for this patient group therefore the primary aim of this study was to describe biomechanical changes in the foot and ankle which occur as a result of midfoot CN in people with diabetes. Methods: A biomechanical study investigating kinematics, kinetics, electromyography (EMG) and plantar pressure was conducted to evaluate alterations to the foot and ankle occurring as a result of midfoot CN. Kinematics, kinetics and EMG were analysed through a 6-segment musculoskeletal model of the lower limb with segments for the pelvis, thigh, shank, rearfoot, midfoot and forefoot constructed in Visual3D. Results: Kinematics were altered in the CN group for all joint segments investigated and across all planes of motion. Kinematic changes were variable between participants. Plantarflexion was reduced in the CN group with no plantarflexion recorded at 100% stance for multiple joint segments indicating a lack of toe-off motion. In the frontal plane, the biggest difference between the CN and healthy control groups was observed during midstance however the degree of inversion and eversion varied between participants. Ankle moment, angular velocity and joint power were markedly reduced in the CN group. All muscles investigated had decreased peak activity except for tibialis anterior which had an increased peak activity. All muscles reached peak activity at initial contact of stance phase except for medial gastrocnemius which peaked later at 70% stance phase. Peak pressure was increased substantially in the midfoot region. Conclusions: Primary disease mechanisms associated with CN result in patient-specific alteration to foot structure and function. This was characterised by highly variable and patient-specific altered joint kinematics and kinetics, EMG-derived muscle function and plantar pressure distribution as well as global changes in gait pattern. This study helps in working towards an individualised approach to improve the understanding of the structure and function of the Charcot foot and can help to guide future treatments.