Unifying model of carpal mechanics based on computationally derived isometric constraints and rules-based motion – the stable central column theory

Abstract

This study was part of a larger project to develop a (kinetic) theory of carpal motion based on computationally derived isometric constraints. Three-dimensional models were created from computed tomography scans of the wrists of ten normal subjects and carpal spatial relationships at physiological motion extremes were assessed. Specific points on the surface of the various carpal bones and the radius that remained isometric through range of movement were identified. Analysis of the isometric constraints and intercarpal motion suggests that the carpus functions as a stable central column (lunate-capitate-hamate-trapezoid-trapezium) with a supporting lateral column (scaphoid), which behaves as a 'two gear four bar linkage'. The triquetrum functions as an ulnar translation restraint, as well as controlling lunate flexion. The 'trapezoid'-shaped trapezoid places the trapezium anterior to the transverse plane of the radius and ulna, and thus rotates the principal axis of the central column to correspond to that used in the 'dart thrower's motion'. This study presents a forward kinematic analysis of the carpus that provides the basis for the development of a unifying kinetic theory of wrist motion based on isometric constraints and rules-based motion.

Predicting Carpal Bone Kinematics Using an Expanded Digital Database of Wrist Carpal Bone Anatomy and Kinematics

“…The row theory described the kinematics of the wrist with two rows organized proximally (lunate and triquetrum) and distally (hamate, capitate, trapezoid, and trapezium), having the scaphoid as a bridge or connection between these two rows. Our mathematical model confirmed that the hamate‐capitate‐trapezoid‐trapezium complex moves relatively rigidly (within 3°), similar to the row theory and previous studies; however, our model demonstrated more variability of motion among the bones of the proximal row. Thus, to consider the bones of the proximal row as part of a rigid element would not be an accurate interpretation of this dataset.…”

“…Due to the variations in motion patterns of the carpal bone articulations among wrists and lack of large sample sizes, none of these models have been rigorously evaluated for predictive ability. Recently, a stable central column theory of carpal bones was proposed by modeling the isometry of ligament lengths on an in vivo dataset, however, the study was limited to a single specific task (in RU direction) with a small sample size (10 wrists). Computational modeling and finite element analysis are powerful tools for evaluating wrist contact forces in mostly static postures, however, to date, they have not been used for kinematic analysis and prediction.…”

Midcarpal Instability

“…Computer-assisted modeling techniques, specifically, finite element analyses of carpal joint interrelationships, 21 is a promising area of research that can provide a more sophisticated picture of these complex relationships. These techniques can also be used to test the kinematic effects of creating both subtle and gross alterations of normal ligamentous anatomy.…”

Four-Dimensional (4D) Printing: A New Evolution in Computed Tomography-Guided Stereolithographic Modeling. Principles and Application

“…Moreover, we calculated the distance between the tubercle of trapezium and pisiform to quantify the movement of trapezium, selected since previous reports showed that trapezium moves as a single entity with trapezoid, capitate, and hamate. 13,14 Although it was more obvious to the naked eye, there was only a small reduction in the distance measured (28-27 mm). This may Fig.…”