Muscle Weakness and Foot Deformities in Diabetes

Abstract

OBJECTIVE—To examine the relationships among muscle weakness, foot deformities, and peroneal and tibial nerve conduction velocity in diabetic and nondiabetic men. RESEARCH DESIGN AND METHODS—A neuropathic and foot evaluation was undertaken in 10 nondiabetic control subjects (group C) and in 36 consecutive diabetic patients attending Diabetes Centre clinics, including 10 diabetic control subjects (group D), 15 diabetic neuropathic patients (group DN), and 11 diabetic patients with a history of ulceration (group DU). Neuropathy was defined as a peroneal motor nerve conduction <40 m/s. Muscle weakness was assessed in seven intrinsic and seven extrinsic muscles of the foot using a semiquantitative score (max score per muscle = 3). Foot deformities were assessed using a foot deformity score (max score = 3). A higher score indicated increased muscle weakness or more severe foot deformities. Muscle weakness and foot deformities were assessed without prior knowledge of patient and neuropathy status. RESULTS—Peroneal and tibial nerve conduction velocity were associated with weakness in muscles innervated by, respectively, the peroneal and tibial nerve (r = −0.70 and r = −0.51, P < 0.01) and foot deformities (r = −0.60 and r = −0.59, P < 0.001). The DN and DU groups had more weakness in intrinsic and extrinsic muscles compared with the C and D groups. Muscles innervated by the tibial nerve had a greater proportional muscle weakness than those innervated by the peroneal nerve in the DN and DU groups. The DN and DU patients had more foot deformities (median food deformity score [interquartile range]) (3 [2–3] and 2 [2–3]) compared with D and C patients (0 [0–0.75] and 0 [0–0]). CONCLUSIONS—Important relationships have been shown between motor nerve conduction deficit and muscle weakness; however, it is still not clear whether abnormal nerve function, leading to a decrease in muscle strength, could be responsible for the development of foot deformities.