Effect of simulated leg length discrepancy on plantar pressure distribution in diabetic patients with neuropathic foot ulceration

Objective: To study the effect of a minor degree of artificially induced leg length discrepancy (LLD) on plantar pressure distribution in diabetic patients with neuropathic foot ulceration. Method: In-shoe plantar pressure distributions were measured on the ulcerated foot during walking using F-scan (Tekscan Inc.). To simulate minor LLD, the contralateral leg length was changed by asking patients to walk under three different conditions: wearing shoe of the same sole thickness (NLLD), walking with a bare foot (20mm long leg) and wearing a 40mm-high platform-sole shoe (20mm short leg). These three different walking conditions were compared in a randomised, single-blinded crossover design. Results: The study included 28 diabetic patients with neuropathic foot ulcers (53.7 +/- 6.8 years; 16 males, 12 female). Notably, the peak pressure and pressure time integral (PTI) were the most affected parameters. PTI significantly increased beneath total foot, mid-foot, 2nd, 3rd, 4th and 5th metatarsal heads (MTHs), and 3rd toe, when the 20mm short leg was simulated (79.4 +/- 21.1; 61.5 +/- 32.3; 59.9 +/- 36.5; 69 +/- 42.1; 70.6 +/- 42.3; 63.9 +/- 33.7; 40.7 +/- 33.2kPa.s, respectively), compared with NLLD (73.7 +/- 19.9; 55.5 +/- 24; 51.8 +/- 30.1; 58.4 +/- 37.6; 60.3 +/- 39.5; 57.2 +/- 32.3; 36.9 +/- 33.3kPa.s, respectively). Conclusion: The short leg of diabetic patients with neuropathic foot ulcers will be subjected to greater pressure load, primarily beneath the total foot, mid-foot and 2nd, 3rd,4th and 5th metatarsal heads. As such, care should be taken to avoid minor LLD, as it could inadvertently develop on using offloading devices.