Plantar soft-tissue thickness predicts high peak plantar pressure in the diabetic foot

The aim of this study was to evaluate whether high plantar foot pressures can be predicted from measurements of plantar soft-tissue thickness in the forefoot of diabetic patients with neuropathy. A total of 157 diabetic patients with neuropathy and at least one palpable foot pulse but without a history of foot ulceration were invited to participate in the study. Plantar tissue thickness was measured bilaterally at each metatarsal head, with patients standing on the same standardized platform. Plantar pressures were measured during barefoot walking using the optical pedobarograph. Receiver operating characteristic analysis was used to determine the plantar tissue thickness predictive of elevated peak plantar pressure. Tissue thickness cutoff values of 11.05, 7.85, 6.65, 6.55, and 5.05 mm for metatarsal heads 1 through 5, respectively, predict plantar pressure at each respective site greater than 700 kPa, with sensitivity between 73% and 97% and specificity between 52% and 84%. When tissue thickness was used to predict pressure greater than 1,000 kPa, similar results were observed, indicating that high pressure at different levels could be predicted from similar tissue thickness cutoff values. The results of the study indicate that high plantar pressure can be predicted from plantar tissue thickness with high sensitivity and specificity.

Plantar tissue thickness is related to peak plantar pressure in the high-risk diabetic foot

OBJECTIVE

To investigate the relationship among plantar foot pressure, plantar subcutaneous tissue thickness, severity of neuropathy (vibration perception threshold [VPT]), callus, and BMI in a large group of neuropathic diabetic patients at risk of foot ulceration.

RESEARCH DESIGN AND METHODS

A total of 157 diabetic neuropathic patients (VPT >25 V) without either peripheral vascular or ulcer history were studied. Plantar foot pressure and plantar tissue thickness were measured at each metatarsal head (MTH) using an optical pedobarograph and an ultrasound scanning platform, respectively.

RESULTS

A significant association was observed between peak plantar pressure and plantar tissue thickness at all MTHs (-0.26 < r < -0.61, P < 0.0001), with the least pronounced association at the first MTH. In addition, the pressure time integral was significantly associated with plantar tissue thickness (-0.24 < r < -0.57, P < 0.0001). BMI was significantly related to plantar tissue thickness (0.18 < r < 0.45, P < 0.05), but not to peak forefoot pressures. Subjects with callus had significantly reduced plantar tissue thickness at all MTHs except the first MTH and increased peak pressures at all MTHs (P < 0.001).

CONCLUSIONS

This study confirms a strong inverse relationship between plantar tissue thickness and dynamic foot pressure measurements. Long-term follow-up of this patient population will confirm whether reduced plantar tissue thickness predicts the development of diabetic foot ulcers.