Three-dimensional stiffness of the carpal arch

Abstract

The carpal arch of the wrist is formed by irregularly shaped carpal bones interconnected by numerous ligaments, resulting in complex structural mechanics. The purpose of this study was to determine the three-dimensional stiffness characteristics of the carpal arch using displacement perturbations. It was hypothesized that the carpal arch would exhibit an anisotropic stiffness behavior with principal directions that are oblique to the conventional anatomical axes. Eight (n = 8) cadavers were used in this study. For each specimen, the hamate was fixed to a custom stationary apparatus. An instrumented robot arm applied three-dimensional displacement perturbations to the ridge of trapezium and corresponding reaction forces were collected. The displacement-force data were used to determine a three-dimensional stiffness matrix using least squares fitting. Eigendecomposition of the stiffness matrix was used to identify the magnitudes and directions of the principal stiffness components. The carpal arch structure exhibited anisotropic stiffness behaviors with a maximum principal stiffness of 16.4 ± 4.6 N/mm that was significantly larger than the other principal components of 3.1 ± 0.9 and 2.6 ± 0.5 N/mm (p < 0.001). The principal direction of the maximum stiffness was pronated within the cross section of the carpal tunnel which is accounted for by the stiff transverse ligaments that tightly bind distal carpal arch. The minimal principal stiffness is attributed to the less constraining articulation between the trapezium and scaphoid. This study provides advanced characterization of the wrist's three-dimensional structural stiffness for improved insight into wrist biomechanics, stability, and function.

Finite element analysis for transverse carpal ligament tensile strain and carpal arch area

“…intercarpal ligament and cartilage) were not included in the model. Instead, stiffness of hamate-to-trapezium was set 11.8 N/mm transversely and 2.9 N/mm in volar-dorsal direction (Gabra and Li, 2016) using linear springs to simulate overall effects of soft tissues around and between carpal bones. By applying the “tie” constraint in ABAQUS, “no-slip” contact condition was assumed at the interface between TCL and skin-fat, TCL and thenar muscles, thenar muscles and skin-fat, TCL and hamate, TCL and trapezium, skin-fat and hamate, thenar muscle and trapezium.…”

Geometric and Mechanical Characterization of Human Carpal Bones – a Preliminary Study

“…Few literary sources were available; we could not compare the results. They show modeling rather than practical utility [15,[17][18][19].…”

Subject-specific finite element analysis of the carpal tunnel cross-sectional to examine tunnel area changes in response to carpal arch loading

“…Widening the CAW can be limited due to the mechanical constraint imposed by the thick band of the transverse carpal ligament. Narrowing of the CAW has been examined by applying forces to the carpal bones in cadaveric hands (Gabra and Li, 2016) and to the radio-ulnar aspects of the wrist in human subjects (Marquardt et al, 2016; Marquardt et al, 2015). Decreasing the CAW at the distal row was demonstrated to increase the volar arch area of the carpal tunnel (Fig.…”