title: The accuracy of estimating proximal tibial translation during natural cadence walking: bone vs. skin mounted targets.
abstract: OBJECTIVE
  To assess the efficacy of estimating proximal tibial translation using video-based motion capture and an array of surface-mounted targets ideal for tracking motion of the tibia.
  
  
  METHODS
  Superficial and bone-anchored tracking targets were used to create two independent sets of data locating the proximal tibia in a global coordinate system.
  
  
  BACKGROUND
  Knowledge of the effect that soft tissue movement has on estimates of proximal tibial translation has not been reported to date. This basic information is necessary to establish construct validity for any study proposing to document tibial translation using standard video-based motion capture methods.
  
  
  METHODS
  A six camera motion capture system was used to collect surface-mounted and bone-anchored data for seven healthy adult subjects walking at a self-selected speed. The subjects walked along the positive Y-axis of the global reference system, with the positive Z-axis oriented vertically.
  
  
  RESULTS
  Average peak differences in the location of the proximal tibia calculated from the bone and surface-mounted targets were 7.1, 3.7 and 2.1 mm along the X, Y and Z axes of the global coordinate system respectively. Individual subject peak differences were as large as 14.1, 11.8 and 8.3 mm along the X, Y and Z axes.
  
  
  CONCLUSIONS
  Estimates of tibial translation with a measurement resolution better than 3 mm are not likely using standard motion capture methods and tracking targets attached superficially to the lower leg.
  
  
  CONCLUSIONS
  The results of this study clearly depict the considerable effect that soft tissue motion of the lower leg has on estimates of proximal tibial translation. Without consideration for the difficulties in measuring femoral, or patellar motion, we believe it is not feasible to routinely obtain sufficiently accurate estimates of detailed knee joint translations using superficial tracking target attachment methods.
authors.affiliation: Center for Biomedical Engineering Research, 126 Spencer Laboratories, University of Delaware, Newark, DE 19716, USA. manal@udel.edu
authors.forename: K
authors.initials: K
authors.lastname: Manal
authors.forename: I
authors.initials: I
authors.lastname: McClay Davis
authors.forename: B
authors.initials: B
authors.lastname: Galinat
authors.forename: S
authors.initials: S
authors.lastname: Stanhope
mesh_terms: D000328:Adult; D001842:Bone and Bones / Q000502:physiology; D003238:Connective Tissue / Q000502:physiology*; D019544:Equipment Failure Analysis / Q000379:methods*; D005260:Female; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D009038:Motion; D009068:Movement / Q000502:physiology; D010808:Physical Examination / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012879:Skin Physiological Phenomena; D013977:Tibia / Q000502:physiology*; D014741:Video Recording / Q000295:instrumentation / Q000379:methods*; D016138:Walking / Q000502:physiology*