Biomechanics of the transverse carpal arch under carpal bone loading

Abstract

Background Carpal tunnel release and conservative interventions are widely used in clinical therapies of carpal tunnel syndrome. The efficacy of these treatment and interventions mainly lies in the exploitation of the mechanical properties of carpal tunnel. This study investigated the structural mechanics of the transverse carpal arch using cadaveric hands. Methods Paired force was applied to the insertion sites of the transverse carpal ligament at both the distal (hamate -trapezium) and proximal (pisiform - scaphoid) level of the carpal tunnel. The two pairs of forces were simultaneously applied in an inward or outward direction when the transverse carpal ligament was intact and transected. Transverse carpal arch and carpal tunnel compliance in response to the forces were analyzed. Three-way repeated measures ANOVA were used to examine the effect of the transverse carpal ligament status (intact/transected), the level of the carpal tunnel (distal/proximal) and the force application direction (inward/outward) on the biomechanics of the transverse carpal arch. Findings Transverse carpal ligament plays a stabilizing role in resisting outward deformation of the carpal tunnel. The carpal tunnel at the proximal level is more flexible than the carpal tunnel at the distal level. The carpal tunnel is more compliant under the inward force application than under the outward force application. Interpretation The understanding of carpal tunnel mechanics potentially helps to improve the existing strategies and to develop alternatives for the treatment of carpal tunnel syndrome.

Tensile properties of the transverse carpal ligament and carpal tunnel complex

“…This has all along been challenging to researchers investigating the biomechanical properties and role of the TCL from a computational (Guo et al, 2009;Li et al, 2009;Main et al, 2012) and experimental (Garcia-Elias et al, 1989;Tengrootenhuysen et al, 2009;Xiu et al, 2010) perspective. This paper describes the first approach taken towards determining tensile properties of the TCL using a commercial Maillon Rapide Delta.…”

“…Sucher and colleagues demonstrated a maximal TCL elongation of 3.7 mm of the carpal arch in female cadavers using a 10 N static load compared to a carpal arch width of 1.83 mm in our study which used a combination of both genders. Xiu et al (2010) showed that an intact carpal arch width increased by about 1 mm when the TCL was subjected to an applied force of 10 N in the outward direction. Aside from load bearing and manipulation techniques, bone-ligament-bone tensile testing methods have also been adopted (Garcia-Elias et al, 1989).…”

“…TCL tensile testing has predominantly been performed in the radial/ulnar direction with very little testing done until recently in the volar/dorsal direction (Main et al, 2012). Previous studies have investigated TCL tensile testing using manipulation and load bearing techniques (Sucher and Hinrichs, 1998;Xiu et al, 2010). Sucher and colleagues demonstrated a maximal TCL elongation of 3.7 mm of the carpal arch in female cadavers using a 10 N static load compared to a carpal arch width of 1.83 mm in our study which used a combination of both genders.…”

“…In terms of biomechanical studies associated with TCL palmar-dorsal loading, the indentation method has been used by various scientific investigators (Chaise et al, 2003;Holmes et al, 2011;Ugbolue, 2012;Ugbolue et al, 2011). Also previous studies have investigated the biomechanical properties of the TCL extracted under biaxial strain (Holmes et al, 2012) and with the TCL intact using manipulation and load bearing techniques Sucher and Hinrichs, 1998;Xiu et al, 2010). While these methods have involved either excising the TCL or determining the biomechanical properties of the carpal tunnel with the TCL intact/ transected, more research designs and testing procedures are necessary to evaluate the TCL and carpal tunnel complex as a whole.…”

Three-dimensional stiffness of the carpal arch

“…Experimental studies have investigated the uniaxial stiffness characteristics of the wrist in the medial-lateral (Fuss and Wagner, 1996; Xiu et al, 2010) and dorsal-palmar directions (Garcia-Elias et al, 1989a). The two-dimensional mechanics of the wrist have also been investigated with respect to the compliance of the carpal tunnel (Tung et al, 2010), force transmission across wrist (Garcia-Elias et al, 1989b; Schuind et al, 1995), and manipulation of the carpal tunnel's cross-sectional area (Li et al, 2013; Li et al, 2011; Li et al, 2009).…”