Reliability and Minimal Detectable Change Values for Predictions of Knee Forces during Gait and Stair Ascent Derived from the FreeBody Musculoskeletal Model of the Lower Limb.

Phil D B Price,Conor Gissane,Daniel J Cleather

doi:10.3389/fbioe.2017.00074

Phil D B Price, Conor Gissane + Show 1 more

Open Access

https://doi.org/10.3389/fbioe.2017.00074

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Abstract

FreeBody is a musculoskeletal model of the lower limb used to calculate predictions of muscle and joint contact forces. The validation of FreeBody has been described in a number of publications; however, its reliability has yet to be established. The purpose of this study was, therefore, to establish the test–retest reliability of FreeBody in a population of healthy adults in order to add support to previous and future research using FreeBody that demonstrates differences between cohorts after an intervention. We hypothesized that test–retest estimations of knee contact forces from FreeBody would demonstrate a high intra-class correlation. Kinematic and kinetic data from nine older participants (4 men: mean age = 63 ± 11 years; 5 women: mean age = 49 ± 4 years) performing level walking and stair ascent was collected on consecutive days and then analyzed using FreeBody. There was a good level of intra-session agreement between the waveforms for the individual trials of each activity during testing session 1 (R = 0.79–0.97). Similarly, overall there was a good inter-session agreement within subjects (R = 0.69–0.97) although some subjects showed better agreement than others. There was a high level of agreement between the group mean waveforms of the two sessions for all variables (R = 0.882–0.997). The intra-class correlation coefficients (ICC) were very high for peak tibiofemoral joint contact forces (TFJ) and hamstring forces during gait, for peak patellofemoral joint contact forces and quadriceps forces during stair ascent and for peak lateral TFJ and the proportion of TFJ accounted for by the medial compartment during both tasks (ICC = 0.86–0.96). Minimal detectable change (MDC) of the peak knee forces during gait ranged between 0.43 and 1.53 × body weight (18–170% of the mean peak values). The smallest MDCs were found for medial TFJ share (4.1 and 5.8% for walking and stair ascent, respectively, or 4.8 and 6.7% of the mean peak values). In conclusion, the results of this study support the use of FreeBody to investigate the effect of interventions on muscle and joint contact forces at the cohort level, but care should be taken if using FreeBody at the subject level.

Highlights

Model verification and validation are important issues within the engineering community (Oberkampf et al, 2004; Oberkampf and Barone, 2006)
Verification is the process of determining that a model implementation accurately represents both the conceptual description of the model and the solution to the model, whereas validation is the process of determining the degree to which a model is an accurate representation of the natural system from the perspective of the intended uses of the model
One aspect of the evaluation of musculoskeletal models that is largely absent from the literature is a discussion of the test–retest reliability of such models

Summary

INTRODUCTION

Model verification and validation are important issues within the engineering community (Oberkampf et al, 2004; Oberkampf and Barone, 2006). The aspiration of this field is to create models which can be used at a subject specific level in order to evaluate individual patients and to inform the planning of therapeutic, medical and surgical treatments (Cleather and Bull, 2012) These data could be used to effectively influence clinical decision-making during knee assessment, providing practitioners with sufficient information to create appropriate rehabilitation strategies, leading to more effective treatments for common knee pathologies, reducing pathological symptoms and improving quality of life. The results of musculoskeletal model simulations will be sensitive to measurement error [e.g., instrumental error (Chiari et al, 2005), soft tissue artifact (Leardini et al, 2005), or misplacement of markers (Croce et al, 2005)], despite the best efforts of the researcher to keep this minimal To ensure these outputs can be used to provide an understanding of the musculoskeletal system and have the potential to be used to influence clinical decisions, the level of error must be determined. This information will be useful in understanding the path toward a clinical tool that can be used at the subject-specific level

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