Forces and moments telemetered from two distal femoral replacements during various activities

Two distal femoral replacements were instrumented to measure axial force, torque and bending moments in the prosthesis shaft. Data are reported up to 2.5 years for the following activities: uni- and bi-lateral standing, walking, stair climbing and descending, treadmill walking, jogging and jumping. In the first subject the greatest averaged peak shaft forces found were: jogging 3.6 Bodyweight (BW), stair descending 3.1 BW, walking 2.8 BW, treadmill walking 2.75 BW, and stair ascending 2.8 BW. Bending moments about the antero-posterior axis (varus–valgus) and medio-lateral axis (flexion–extension) peaked in the range 8.5–9.8 and 4.7–7.6 BW cm respectively, over the follow-up period. Axial torques peaked in the range 0.2–1.3 BW cm, outwardly directed. At most follow-up sessions, forces and moments during jogging were generally greater than those for other gait activities. In the second subject forces and moments were generally only 45–70% of those in the first subject, due to inadequate musculature around the knee. The data can be applied to the design and testing of distal femoral replacements and even to total knee replacements, and contributes to the knowledge of forces acting in the distal femur during activity.