ESB clinical biomechanics award 2008: Complete data of total knee replacement loading for level walking and stair climbing measured in vivo with a follow-up of 6–10 months

Abstract

Background Detailed information about the loading of the knee joint is required for various investigations in total knee replacement. Up to now, gait analysis plus analytical musculo-skeletal models were used to calculate the forces and moments acting in the knee joint. Currently, all experimental and numerical pre-clinical tests rely on these indirect measurements which have limitations. The validation of these methods requires in vivo data; therefore, the purpose of this study was to provide in vivo loading data of the knee joint. Methods A custom-made telemetric tibial tray was used to measure the three forces and three moments acting in the implant. This prosthesis was implanted into two subjects and measurements were obtained for a follow-up of 6 and 10 months, respectively. Subjects performed level walking and going up and down stairs using a self-selected comfortable speed. The subjects’ activities were captured simultaneously with the load data on a digital video tape. Customized software enabled the display of all information in one video sequence. Findings The highest mean values of the peak load components from the two subjects were as follows: during level walking the forces were 276 %BW (percent body weight) in axial direction, 21 %BW (medio-lateral), and 29 %BW (antero-posterior). The moments were 1.8 %BW*m in the sagittal plane, 4.3 %BW*m (frontal plane) and 1.0 %BW*m (transversal plane). During stair climbing the axial force increased to 306 %BW, while the shear forces changed only slightly. The sagittal plane moment increased to 2.4 %BW*m, while the frontal and transversal plane moments decreased slightly. Stair descending produced the highest forces of 352 %BW (axial), 35 %BW (medio-lateral), and 36 %BW (antero-posterior). The sagittal and frontal plane moments increased to 2.8 %BW*m and 4.6 %BW*m, respectively, while the transversal plane moment changed only slightly. Interpretation Using the data obtained, mechanical simulators can be programmed according to realistic load profiles. Furthermore, musculo-skeletal models can be validated, which until now often lacked the ability to predict properly the non-sagittal load values, e.g. varus–valgus and internal–external moments.