Markerless motion capture to assess upper extremity movements in individuals with dyskinetic cerebral palsy: an accuracy and validity study

Aim To evaluate clinical utility of markerless motion capture (MMC) during an reaching-sideways-task in individuals with dyskinetic cerebral palsy (DCP) by determining (1) accuracy of key points tracking in individuals with DCP and typically developing (TD) peers, (2) concurrent validity by correlating MMC towards 3D-motion analysis (3DMA) and (3) construct validity by assessing differences in MMC features between a DCP and TD group. Method MMC key points were tracked from frontal videos and accuracy was assessed towards human labelling. Shoulder, elbow and wrist angles were calculated from MMC and 3DMA (as gold standard) and correlated. Additionally, execution time and variability features were calculated from key points. MMC features were compared between groups. Results Fifty-one individuals (30 DCP;21 TD; age:5-24 years) participated. An accuracy of approximately 1.5 cm was reached for key point tracking. While significant correlations were found for wrist (ρ=0.810;p<0.001) and elbow angles (ρ=0.483;p<0.001), MMC shoulder angles were not correlated (ρ=0.247;p=0.102) to 3DMA. Wrist and elbow angles, execution time and variability features all differed between groups (Effect sizes 0.35-0.81;p<0.05). Interpretation Videos of a reaching-sideways-task processed by MMC to assess upper extremity movements in DCP showed promising accuracy and validity. The method is especially valuable to assess movement variability within DCP without expensive equipment. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement Inti Vanmechelen and Helga Haberfehlner are both funded by the Research Foundation Flanders (FWO) (I.V: PhD fellowship\_11C0220N; H.H: SoE fellowship\_12ZZW22N). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Medical Ethics Committees of the University Hospitals Leuven/KU Leuven and Vrije Universiteit Medical Center, Amsterdam gave ethical approval for this work. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes