Force and pressure recordings from patients with femoral fractures treated by cast-brace application

Five patients with midshaft femoral fractures treated by early cast-brace application and ambulation were studied. With the patients in lying and standing postures, force transmitted through the knee hinges, ground reaction and pressure under the thigh cast were measured each week. When standing on the injured limb, the maximum load tolerated increased as the fractures healed and ranged from 39-61% body weight and 97-100% body weight at weeks two and eight respectively. In this posture in three cases, force transmitted across the knee hinges did not exceed 35% body weight or alter significantly throughout healing, the other two reached maxima of 67 and 60% body weight at week five and values decreased to less than 50% at week ten. By week six, each patient was transmitting significant force across the fracture (31, 12, 7, 36 & 55% body weight). Vertical force on the thigh cast due to rigid soft tissue containment was calculated to be between 3.6 and 10.8 X 9.8 Newtons throughout healing in all cases. Force transmitted through the knee hinges and pressure under the thigh cast, increased linearly as the injured limb was loaded.