title: A principal component analysis approach to correcting the knee flexion axis during gait.
abstract: Accurate and precise knee flexion axis identification is critical for prescribing and assessing tibial and femoral derotation osteotomies, but is highly prone to marker misplacement-induced error. The purpose of this study was to develop an efficient algorithm for post-hoc correction of the knee flexion axis and test its efficacy relative to other established algorithms. Gait data were collected on twelve healthy subjects using standard marker placement as well as intentionally misplaced lateral knee markers. The efficacy of the algorithm was assessed by quantifying the reduction in knee angle errors. Crosstalk error was quantified from the coefficient of determination (r(2)) between knee flexion and adduction angles. Mean rotation offset error (αo) was quantified from the knee and hip rotation kinematics across the gait cycle. The principal component analysis (PCA)-based algorithm significantly reduced r(2) (p<0.001) and caused αo,knee to converge toward 11.9±8.0° of external rotation, demonstrating improved certainty of the knee kinematics. The within-subject standard deviation of αo,hip between marker placements was reduced from 13.5±1.5° to 0.7±0.2° (p<0.001), demonstrating improved precision of the knee kinematics. The PCA-based algorithm performed at levels comparable to a knee abduction-adduction minimization algorithm (Baker et al., 1999) and better than a null space algorithm (Schwartz and Rozumalski, 2005) for this healthy subject population.
authors.affiliation: Mayo Graduate School, Biomedical Engineering and Physiology Track, Mayo Clinic, Rochester, MN 55905, USA; Motion Analysis Laboratory, Division of Orthopedic Research, Mayo Clinic, Charlton North L-110L, Rochester, MN 55905, USA.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Jensen
authors.affiliation: Mayo Graduate School, Biomedical Engineering and Physiology Track, Mayo Clinic, Rochester, MN 55905, USA; Whitaker International Program, Chiang Mai University, Department of Physical Therapy, Chiang Mai 50200, Thailand.
authors.forename: Vipul
authors.initials: V
authors.lastname: Lugade
authors.affiliation: Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE 19713, USA.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Crenshaw
authors.affiliation: Motion Analysis Laboratory, Division of Orthopedic Research, Mayo Clinic, Charlton North L-110L, Rochester, MN 55905, USA.
authors.forename: Emily
authors.initials: E
authors.lastname: Miller
authors.affiliation: Motion Analysis Laboratory, Division of Orthopedic Research, Mayo Clinic, Charlton North L-110L, Rochester, MN 55905, USA. Electronic address: kaufman.kenton@mayo.edu.
authors.forename: Kenton
authors.initials: K
authors.lastname: Kaufman
mesh_terms: D000328:Adult; D000465:Algorithms; D001696:Biomechanical Phenomena; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D025341:Principal Component Analysis; D012399:Rotation; D055815:Young Adult
keywords: Axis of rotation; Correction algorithm; Gait analysis; Kinematics; Marker placement