A Femoral Clamp to Reduce Soft Tissue Artifact: Accuracy and Reliability in Measuring Three-Dimensional Knee Kinematics During Gait

The accurate measurement of full six degrees-of-freedom (6DOFs) knee joint kinematics is prohibited by soft tissue artifact (STA), which remains the greatest source of error. The purpose of this study was to present and assess a new femoral clamp to reduce STA at the thigh. It was hypothesized that the device can preserve the natural knee joint kinematics pattern and outperform a conventional marker mounted rigid cluster during gait. Six healthy subjects were asked to walk barefoot on level ground with a cluster marker set (cluster gait) followed by a cluster-clamp-merged marker set (clamp gait) and their kinematics was measured using the cluster method in cluster gait and the cluster and clamp methods simultaneously in clamp gait. Two operators performed the gait measurement. A 6DOFs knee joint model was developed to enable comparison with the gold standard knee joint kinematics measured using a dual fluoroscopic imaging technique. One-dimensional (1D) paired t-tests were used to compare the knee joint kinematics waveforms between cluster gait and clamp gait. The accuracy was assessed in terms of the root-mean-square error (RMSE), coefficient of determination, and Bland-Altman plots. Interoperator reliability was assessed using the intraclass correlation coefficient (ICC). The result showed that the femoral clamp did not change the walking speed and knee joint kinematics waveforms. Additionally, clamp gait reduced the rotation and translation errors in the transverse plane and improved the interoperator reliability when compared to the rigid cluster method, suggesting a more accurate and reliable measurement of knee joint kinematics.

A musculoskeletal modelling approach to explain sit-to-stand difficulties in older people due to changes in muscle recruitment and movement strategies

By 2050 the proportion of over 65s is predicted to be 20% of the population. The consequences of an age-related reduction in muscle mass have not been fully investigated and, therefore, the aim of the present study was to quantify the muscle and joint contact forces using musculoskeletal modelling, during a sit-to-stand activity, to better explain difficulties in performing everyday activities for older people. A sit-to-stand activity with and without the use of arm rests was observed in ninety-five male participants, placed into groups of young (aged 18-35 years), middle-aged (aged 40-60 years) or older adults (aged 65 years and over). Older participants demonstrated significantly lower knee extensor and joint forces than the young when not using arm rests, compensating through elevated hip extensor and ankle plantarflexor muscle activity. The older group were also found to have higher shoulder joint contact forces whilst using arm rests. This tendency to reorganise muscle recruitment to include neighbouring groups or other parts of the body could make everyday activities more susceptible to age-related functional decline. Reductions in leg strength, via age- or atrophy- related means, creates increased reliance on the upper body and may result in further lower limb atrophy through disuse. The eventual decline of upper body function reduces strength reserves, leading to increased vulnerability, dependence on others and risk of institutionalisation.