Diagnostic Modeling for Pedal Fat Pad Atrophy

Human feet must bear the entire weight of the body. Feet have fat pads on their plantar surface that act as shock absorbers between the skin and bone. However, repetitive mechanical stress throughout a person's lifetime leads to gradual atrophy of these fat pads. In addition to this age-related degeneration, fat pad atrophy can be caused by other mechanisms such as abnormal foot mechanics, steroid use, and collagen vascular disease. Regardless of the cause, many patients with plantar fat pad atrophy experience considerable pain and loss of function.

Previous studies have negatively correlated plantar soft tissue thickness with plantar pressure, with the loss of plantar fat being a fundamental mechanism associated with pressure-related foot disorders. Increased pressure from fat pad atrophy is commonly managed with padded socks, insoles, and shoe modification. However, these extrinsic strategies are totally dependent on patient compliance, and devices must be replaced as soon as they begin to break down. Another treatment option includes silicone injections into the plantar aspect of the foot. In one study, patients receiving silicone treatment experienced increased plantar tissue thickness and decreased plantar pressure, but these cushioning properties decreased over time and the need for additional booster injections was ultimately suggested. Furthermore, silicone has been known to migrate away from the injection site and has been found in the inguinal lymph nodes of patients.

A different strategy that is gaining momentum is autologous fat grafting to the foot. Taking a patient's own tissue, often from the abdomen or thigh, and transplanting it to areas of plantar fat pad atrophy may reduce pressure in a more natural and permanent manner. Only one study to date has been published on autologous fat grafting to the foot, but the patients were receiving concurrent surgical procedures with their fat grafting and the results were reported subjectively by the patients.

In this study, the investigators hypothesize that there is a difference in plantar tissue thickness, plantar pressure, and pain score in patients diagnosed with plantar fat pad atrophy compared to healthy, foot-type matched controls. Results will be measured objectively using ultrasound for tissue thickness, optical pedobarograph for plantar pressure, and Manchester foot pain and disability index (MFPDI) for pain score. Furthermore, the investigators predict that these results will help establish criteria for fad pad atrophy diagnosis in the clinic as well as determine which patients would receive greatest benefit from fat grafting to the foot.