Induration of the diabetic foot pad: another risk factor for recurrent neuropathic plantar ulcers

Ten diabetic feet with polyneuropathy and a history of recurrent plantar ulcers were assessed for soft tissue abnormalities of the plantar pad, in comparison with non-diabetic control feet. Plantar pad thickness and hardness were measured at the metatarsal heads. In addition, joint mobility was assessed by measuring the passive dorsal flexion of the metatarsophalangeal joints, and peak plantar pressures were studied during walking. The results showed slightly less joint mobility and thinner plantar pads in the diabetics as compared with control subjects; however, the differences failed to reach statistical significance. Soft tissue hardness at the heel was also comparable in patients and controls. At the sites of previous plantar ulcers over the metatarsal joints, soft tissue was significantly harder than at other sites in the same feet or in the control feet; peak plantar pressure at two metatarsal heads was higher in the diabetic feet than in the control feet (p < 0.05). Induration of the periarticular soft tissue may predispose to recurrent foot ulcers in diabetics by decreasing the shock-absorption capacity of the plantar pad.