title: Decoupling the Wrist: A Cadaveric Experiment Examining Wrist Kinematics Following Midcarpal Fusion and Scaphoid Excision.
abstract: At the wrist, kinematic coupling (the relationship between flexion-extension and radial-ulnar deviation) facilitates function. Although the midcarpal joint is critical for kinematic coupling, many surgeries, such as 4-corner fusion (4CF) and scaphoidexcision 4-corner fusion (SE4CF), modify the midcarpal joint. This study examines how 4CF and SE4CF influence kinematic coupling by quantifying wrist axes of rotation. Wrist axes of rotation were quantified in 8 cadaveric specimens using an optimization algorithm, which fit a 2-revolute joint model to experimental data. In each specimen, data measuring the motion of the third metacarpal relative to the radius was collected for 3 conditions (nonimpaired, 4CF, SE4CF). The calculated axes of rotation were compared using spherical statistics. The angle between the axes of rotation was used to assess coupling, as the nonimpaired wrist has skew axes (ie, angle between axes approximately 60°). Following 4CF and SE4CF, the axes are closer to orthogonal than those of the nonimpaired wrist. The mean angle (±95% confidence interval) between the axes was 92.6° ± 25.2° and 99.8° ± 22.0° for 4CF and SE4CF, respectively. The axes of rotation defined in this study can be used to define joint models, which will facilitate more accurate computational and experimental studies of these procedures.
authors.affiliation: 1 Northwestern University.|3 Rehabilitation Institute of Chicago.|4 Edward Hines, Jr. VA Hospital.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Nichols
authors.affiliation: 4 Edward Hines, Jr. VA Hospital.|5 Loyola University-Chicago.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Bednar
authors.affiliation: 4 Edward Hines, Jr. VA Hospital.|5 Loyola University-Chicago.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Havey
authors.affiliation: 1 Northwestern University.|2 Northwestern University Feinberg School of Medicine.|3 Rehabilitation Institute of Chicago.|4 Edward Hines, Jr. VA Hospital.
authors.forename: Wendy M
authors.initials: WM
authors.lastname: Murray
mesh_terms: D002102:Cadaver; D002348:Carpal Bones / Q000502:physiology / Q000601:surgery*; D050824:Carpal Joints / Q000502:physiology* / Q000601:surgery; D003198:Computer Simulation; D006801:Humans; D007103:Immobilization / Q000379:methods; D008954:Models, Biological; D016059:Range of Motion, Articular / Q000502:physiology*; D012399:Rotation; D021361:Scaphoid Bone / Q000502:physiology / Q000601:surgery*; D014955:Wrist Joint / Q000502:physiology* / Q000601:surgery
keywords: axes of rotation; kinematics; motion analysis; scaphoid-excision four-corner fusion; wrist