ABSTRACT
Kinematic analysis of the digits using optical motion capture systems relies on defining accurate coordinate systems for the individual segments. Limitations of previous digit kinematic protocols include marker placement errors, marker occlusion and superimposition, and skin movement artifact. The purpose of this study was to develop a protocol utilizing a digit alignment device (DAD) and nail marker clusters to overcome these limitations. Ten subjects underwent 10 static calibration trials for validation. The orientation of the thumb distal phalange relative to the index finger distal phalange was described using Euler angles of pitch(x), yaw(y'), and roll(z''). The digit calibration protocol demonstrated high accuracy (0.5°, 1.9° and 2.2° for x, y', z'') and precision (1.4°, 2.3° and 3.1° for x, y', z''). The developed protocol provided convenient identification of transformations that determine anatomically relevant coordinate systems for the distal phalanges of the digits. The potential of utilizing this protocol as a standardized tool for digit kinematics was demonstrated using a dynamic task of precision pinching.
Subject(s)
Body Weights and Measures/instrumentation , Hand Strength/physiology , Range of Motion, Articular/physiology , Thumb/physiology , Adult , Biomechanical Phenomena , Equipment Design , Equipment Safety , Female , Finger Joint/physiology , Fingers/physiology , Humans , Male , Reference Values , Sampling Studies , Young AdultABSTRACT
Osteoarthritis of the trapeziometacarpal (TMC) joint can be treated by arthrodesis and arthroplasty, which potentially decreases or increases the degrees of freedom (DoF) of the joint, respectively. The aim of our study was to bring novel biomechanical insights into these joint surgery procedures by investigating the influence of DoF at the TMC joint on muscle and joint forces in the thumb. A musculoskeletal model of the thumb was developed to equilibrate a 1 N external force in various directions while the thumb assumed key and pulp pinch postures. Muscle and joint forces were computed with an optimization method. In comparison to that of the 2-DoF (intact joint) condition, muscle forces slightly decreased in the 0-DoF (arthrodesis) condition, but drastically increased in the 3-DoF (arthroplasty) condition. TMC joint forces in the 3-DoF condition were 12 times larger than the 2-DoF joint. This study contributes to a further understanding of the biomechanics of the intact and surgically repaired TMC joint and addresses the biomechanical consequences of changing a joint's DoF by surgery.
