A practical solution to reduce soft tissue artifact error at the knee using adaptive kinematic constraints

The effect of joint translation constraint on within-participant variability of kinematics and kinetics during running in cerebral palsy

“…Utilising joint constraint boundaries to allow restricted joint centre translation may explain why the IK6Constrained model resulted in lower variability than both the IK3 model and the IK6 model. This explanation is consistent with the findings of Potvin and colleagues (Potvin et al, 2017), who reported a smaller range of knee rotation using five DoF with bone-pin informed constraint compared to using five DoF without informed joint constraint boundaries in walking in healthy adults. The finding is important because both running gait and cerebral palsy are associated with high intrinsic variability (Estep et al, 2016;Klejman et al, 2010;Steinwender et al, 2000) and it has traditionally been difficult to recruit large numbers to studies in this population due to the heterogeneity of their clinical presentation.…”

“…During swing phase of running the hip is moved rapidly through a large arc of movement (Novacheck, 1998) and thus is subject to high levels of soft tissue artefact (Peters et al, 2010). The application of joint constraints is one potential method to reduce the effect of soft tissue artefact but is dependent on the joint constraints specified (Leardini et al, 2017;Potvin et al, 2017). Our findings suggest that applying joint translation constraints appropriate for children with cerebral palsy can reduce the effect of measurement error on skeletal movement.…”

“…Potvin and colleagues (Potvin et al, 2017) reported a smaller effect of joint model DoF on joint moments compared to joint angles in walking, whereas the present study has found a significant reduction in all joint moment SDs using the IK6Constrained model. This may be because the IK6Constrained model incorporates joint constraint boundaries at all three lower limb joints, whereas Potvin and colleagues only specified joint constraint boundaries at the knee (Potvin et al, 2017). The effect of reducing error by using the IK6Constrained model may also have a magnified effect on force calculations due to the greater forces associated with running compared with walking (Smale et al, 2017).…”

“…The magnitude of specified joint constraint impacts the variability of kinematic and kinetic gait measures (Kainz et al, 2016). For example, Potvin and colleagues (Potvin et al, 2017) reported a smaller standard deviation (SD) for knee rotation angle in the transverse plane during walking when knee joint constraints were informed from published in-vivo data, compared to a knee model with no constraints. A reduction in within-participant variation due to modelling implies a reduction in random error due to measurement, with the assumption that biological variability is maintained (Hopkins, 2000).…”

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

“…Coupled motions, due to the articular STA can be corrected mathematically through the application of optimisation techniques, including the least squares method [32][33][34][35] and the point cluster technique [36,37]. Although these techniques provide encouraging results they can only compensate for the inter-marker movement, which is a minor component of STA [30,38]. Global optimisation techniques have been developed which use underlying knee joint models that include kinematic constraints to limit STA [39,40].…”