TIBIOFEMORAL AND TIBIOCALCANEAL MOTION DURING WALKING - EXTERNAL VS. SKELETAL MARKERS

The purpose of this study was to determine the errors in knee (tibiofe moral) and ankle joint complex (AJC; tibiocalcaneal) rotations caused by the skin movement artefact. Intracortical bone pins were inserted i nto the femur, tibia, and calcaneus of five subjects. Marker triads we re attached to these pins, and additionally, six skin markers to the t high, six to the shank, and three to the shoe. For each subject three walking trials were filmed with three synchronized LOCAM cameras (50 H z). Flexion/extension, ab/adduction, and longitudinal rotation at the tibiofemoral joint as well as plantar-/dorsiflexion, ab/adduction, and in/eversion at the AJC were calculated from both skin and bone marker s during the stance phase of walking. The results showed that the erro rs in knee rotations were mainly caused by the thigh markers. Knee fle xion/extension was generally well reflected with the use of skin marke rs (mean difference: 2.1 degrees). The agreement between skin and bone marker based kinematics for ab/adduction and internal/external knee r otation ranged from good to virtually no agreement, and in some subjec ts, the errors exceeded the actual motion. The errors in AJC rotations were mainly caused by the markers on the shoe/foot segment. The tibio calcaneal rotations were generally well reflected with external marker s. However, tibiocalcaneal rotations derived from external markers typ ically exceeded the true bone motions. The results suggest that (a) kn ee rotations other than flexion/extension may be affected with substan tial errors when using external markers, and (b) tibiocalcaneal rotati ons are generally well reflected with external markers, but amplitudes are overestimated. (C) 1997 Elsevier Science B.V.