Dynamic simulation of hip strategy of diabetic neuropathic individuals during gait

Patients suffering from diabetic neuropathy present disturbed kinetic, kinematic and electromyographic gait patterns. These disturbances have been experimentally related with plantar ulcerations. However, experimental data are limited because it is not possible to record certain muscle groups (e.g, illiopsoas). In this respect, computational simulations complement the experiments. Our aim is to simulate how the neuromusculoskeletal system of diabetic neuropathic individuals deals with a reduced distal muscle function during level gait. It was hypothesized that proximal muscle compensates the reduced distal muscle function. We used a seven segment planar musculoskeletal model of the body with 8 muscles in each leg. Normal gait muscle excitation patterns were used as reference input in forward dynamics simulations. In order to simulate the neuropathic gait condition, those reference excitations were modified according to functional changes found in diabetic gait. The tibialis anterior (3,75%) and gastrocnemius (15%) excitation reduction along with iliopsoas (11,25%) and hamstrings (7,5%) excitation increase during push-off, guaranteed larger pre-swing hip flexion and smaller hip extension during stance. This motion pattern was not observed when hamstrings excitation remained unchanged. Ankle plantar-flexion during push-off and ankle flexion during swing decreased as the gastrocnemius and tibialis were functionally reduced. The musculoskeletal model was able to represent the hip strategy possibly adopted by the diabetic neuropathic patients during gait as an adaptation to loss of function in distal muscles. The increase in hamstrings function is crucial to improve the model dynamic stability opening new approaches to therapeutic handling of these patients.