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Sensitivity of a juvenile subject-specific musculoskeletal model of the ankle joint to the variability of operator-dependent input.

ABSTRACT: Subject-specific musculoskeletal modelling is especially useful in the study of juvenile and pathological subjects. However, such methodologies typically require a human operator to identify key landmarks from medical imaging data and are thus affected by unavoidable variability in the parameters defined and subsequent model predictions. The aim of this study was to thus quantify the inter- and intra-operator repeatability of a subject-specific modelling methodology developed for the analysis of subjects with juvenile idiopathic arthritis. Three operators each created subject-specific musculoskeletal foot and ankle models via palpation of bony landmarks, adjustment of geometrical muscle points and definition of joint coordinate systems. These models were then fused to a generic Arnold lower limb model for each of three modelled patients. The repeatability of each modelling operation was found to be comparable to those previously reported for the modelling of healthy, adult subjects. However, the inter-operator repeatability of muscle point definition was significantly greater than intra-operator repeatability ( p?

SUBMITTER: Hannah I

PROVIDER: S-EPMC5407509 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

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Sensitivity of a juvenile subject-specific musculoskeletal model of the ankle joint to the variability of operator-dependent input.

Hannah Iain I Montefiori Erica E Modenese Luca L Prinold Joe J Viceconti Marco M Mazzà Claudia C

Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine 20170501 5

Subject-specific musculoskeletal modelling is especially useful in the study of juvenile and pathological subjects. However, such methodologies typically require a human operator to identify key landmarks from medical imaging data and are thus affected by unavoidable variability in the parameters defined and subsequent model predictions. The aim of this study was to thus quantify the inter- and intra-operator repeatability of a subject-specific modelling methodology developed for the analysis of ...[more]

PMID: 28427313

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Project description:BackgroundRestoring the joint line is an important principle in total knee arthroplasty. However, the effect of joint line level on patient outcomes after total ankle arthroplasty (TAA) remains unclear, as there is no established method for measuring ankle joint level in TAA. The objective of this study was to develop a reliable radiographic ankle joint line measurement method and to compare ankle joint line level measured pre-TAA, post-TAA, and in nonarthritic ankles.MethodsA total of 112 radiographic sets were analyzed. Each set included weightbearing anteroposterior radiographs of the operative ankle taken preoperatively, 1-year postoperatively, and of the contralateral ankle. Measurements of vertical intermalleolar distance (VIMD) and vertical joint line distance (VJLD) at pre-TAA, post-TAA, and of the contralateral ankle were recorded by 2 authors on 2 separate occasions. The ratio of VJLD to VIMD was defined as the joint line height ratio (JLHR). Reliability of measurements and correlation between VIMD and VJLD were assessed. Pre-TAA, nonarthritic contralateral ankle, and post-TAA JLHR were compared and considered significantly different if P <.05.ResultsThe inter- and intrarater reliability of radiographic measurements was excellent (r > 0.9). There were strong positive correlations of VIMD and VJLD, r = 0.809 (pre-TAA)/0.756 (post-TAA), P < .001. Mean (SD) pre-TAA, nonarthritic contralateral ankle, and post-TAA JLHRs were 1.54 (0.31), 1.39 (0.26), and 1.62 (0.49), respectively. Pre- and post-TAA JLHRs were significantly higher compared to the nonarthritic contralateral ankle (P < .05). JHLR was not significantly different between pre- and post-TAA (P = .15).ConclusionThe JLHR was reliable and could be a clinically applicable method for assessing ankle joint line level in patients undergoing TAA. End-stage ankle arthritis demonstrated elevated joint line level compared with nonarthritic ankles, and the joint line level post-TAA remained elevated compared with nonarthritic ankles. Further studies are needed to understand the effect of joint line elevation on clinical outcomes after TAA.Level of evidenceLevel III, retrospective comparative study.

Project description:Individuals with lower-limb amputation often have difficulty walking on slopes, in part due to limitations of conventional prosthetic feet. Conventional prostheses have fixed ankle set-point angles and cannot fully replicate able-bodied ankle dynamics. Microprocessor-controlled ankles have been developed to help overcome these limitations. The objective of this study was to characterize how the slope adaptation feature of a microprocessor-controlled ankle affected individual prosthesis user gait biomechanics during sloped walking. Previous studies on similar microprocessor-controlled ankles have focused on group-level results (inter-subject mean), but did not report individual subject results. Our study builds upon prior work and provides new insight by presenting subject-specific results and investigating to what extent individual responses agree with the group-level results. We performed gait analysis on seven individuals with unilateral transtibial amputation while they walked on a 7.5° incline with a recently redesigned microprocessor-controlled ankle that adjusts ankle set-point angle to the slope. We computed gait kinematics and kinetics, and compared how users walked with vs. without this set-point adjustment. The microprocessor-controlled ankle increased minimum toe clearance for all subjects. Despite the microprocessor-controlled ankle behaving similarly for each user, we observed marked differences in individual responses. For instance, two users switched from a forefoot landing pattern with the microprocessor-controlled ankle locked at neutral angle to rearfoot landing when the microprocessor-controlled ankle adapted to the slope, while two maintained a forefoot and three maintained a rearfoot landing pattern across conditions. Changes in knee angle and moment were also subject-specific. Individual user responses were often not well represented by inter-subject mean. Although the prevailing experimental paradigm in prosthetic gait analysis studies is to focus on group-level analysis, our findings call attention to the high inter-subject variability which may necessitate alternative experimental approaches to assess prosthetic interventions.

Project description:The stop signal task has been used to quantify the human inhibitory control. The inter-subject and intra-subject variability was investigated under the inhibition of human response with a realistic environmental scenario. In present study, we used a battleground scenario where a sniper-scope picture was the background, a target picture was a go signal, and a nontarget picture was a stop signal. The task instructions were to respond on the target image and inhibit the response if a nontarget image appeared. This scenario produced a threatening situation and endorsed the evaluation of how subject's response inhibition manifests in a real situation. In this study, 32 channels of electroencephalography (EEG) signals were collected from 20 participants during successful stop (response inhibition) and failed stop (response) trials. These EEG signals were used to predict two possible outcomes: successful stop or failed stop. The inter-subject variability (between-subjects) and intra-subject variability (within-subjects) affect the performance of participants in the classification system. The EEG signals of successful stop versus failed stop trials were classified using quadratic discriminant analysis (QDA) and linear discriminant analysis (LDA) (i.e., parametric) and K-nearest neighbor classifier (KNNC) and Parzen density-based (PARZEN) (i.e., nonparametric) under inter- and intra-subject variability. The EEG activities were found to increase during response inhibition in the frontal cortex (F3 and F4), presupplementary motor area (C3 and C4), parietal lobe (P3 and P4), and occipital (O1 and O2) lobe. Therefore, power spectral density (PSD) of EEG signals (1-50Hz) in F3, F4, C3, C4, P3, P4, O1, and O2 electrodes were measured in successful stop and failed stop trials. The PSD of the EEG signals was used as the feature input for the classifiers. Our proposed method shows an intra-subject classification accuracy of 97.61% for subject 15 with QDA classifier in C3 (left motor cortex) and an overall inter-subject classification accuracy of 71.66% ± 9.81% with the KNNC classifier in F3 (left frontal lobe). These results display how inter-subject and intra-subject variability affects the performance of the classification system. These findings can be used effectively to improve the psychopathology of attention deficit hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), schizophrenia, and suicidality.

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Sensitivity of a juvenile subject-specific musculoskeletal model of the ankle joint to the variability of operator-dependent input.

Publications

Sensitivity of a juvenile subject-specific musculoskeletal model of the ankle joint to the variability of operator-dependent input.

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