The effect of silicone injections in the diabetic foot on peak plantar pressure and plantar tissue thickness: a 2-year follow-up

OBJECTIVE: To report the efficacy of injected liquid silicone (ILS) in the foot at 2 years after administration. DESIGN: Randomized controlled trial. SETTING: Diabetic foot clinic in the United Kingdom. PARTICIPANTS: Twenty-eight diabetic neuropathic patients, randomized into an active treatment group (n=14) and a placebo group (n=14). INTERVENTION: Participants were given either 6 injections of 0.2mL of liquid silicone (silicone group) or equal volumes of saline (placebo group) under metatarsal head sites with callus. MAIN OUTCOME MEASURES: Plantar tissue thickness and plantar pressures were measured at 3, 6, 12, and 24 months postinjection. RESULTS: At 12 months, the plantar tissue thickness in the silicone group had increased by a mean 1.6+/-0.9mm (P=.001), and remained increased at 24 months (1.1+/-0.7mm, P=.003). Peak plantar pressure in the silicone group was reduced at 12 months (-165.0+/-253.5kPa, P=.03), but not at 24 months. There was no change in tissue thickness or peak plantar pressure in the placebo group at 12 and 24 months. The reduction in the pressure time integral (PTI) in the silicone group did not reach significance at 12 months (-.71+/-1.17kPa/s, P=.055). Although PTI returned to baseline at 24 months for the silicone group, it was significantly increased in the placebo group (.64+/-.37kPa/s, P=.043), suggesting that silicone may still exhibit some pressure-reducing properties after 24 months. CONCLUSIONS: The results indicate that at 24 months postinjection the cushioning properties of ILS have reduced, suggesting that booster injections may be required in certain patients.