Tensile properties of the transverse carpal ligament in-situ

INTRODUCTION. The clinical motivation for this study is Carpal Tunnel Syndrome (CTS) which is regarded as the most common peripheral neuropathy affecting the hand. In the years gone by, hand research studies have grown and continue to gain popularity. These developments have been channeled towards biomechanical related research studies designed to elucidate some of the underlying mechanisms and biomedical aspects associated with the carpal tunnel complex. Recently, a novel method has been developed to determine the tensile properties of the Transverse Carpal Ligament (TCL) in-situ [1]. This study aims to describe the biomedical aspects of the novel TCL tensile testing procedure.

METHODS. Biomechanically, the TCL has been studied to determine its compressive [2] and tensile [3, 4] properties. Although, these methods have involved either excising the TCL or determining the biomechanical properties of the TCL intact / transected, experimentally there is still no widely accepted method designed to specifically evaluate the tensile properties of the TCL and Carpal Tunnel Complex (CTC). Hence, to date, there are no known methods to test the TCL to failure in-situ. The proposed method uses video analysis techniques together with a Maillon Rapide Delta (similar to a Carabiner) to determine the tensile properties of the TCL–CTC. Six embalmed cadaveric specimens amputated at the mid-forearm and aged (Mean (SD)): 82 (6.29) years were tested. Using trigonometry and geometry the elongation and strain of the TCL and carpal arch were calculated. Tensile properties of the TCL– CTC and Load–Displacement data were also obtained. Descriptive statistics, one-way ANOVA together with a Post-hoc analysis (Tukey) and t-tests were incorporated.

RESULTS. The TCL failed either at the mid-substance or at their bony attachments. There were no significant differences between the original TCL width and TCL at peak elongation (p = 0.108). There were significant differences between the original Carpal Arch (CA) width and CA width at peak elongation (p = 0.002). At maximum deformation the peak load and maximum TCL displacements ranged from 285.74N to 1,369.66N and 7.09mm to 18.55mm respectively. The load at tensile strength ranged from 272.09N to 1293.36N and the ultimate tensile strength mean (SD) was 23.99 (10.68) Nmm-2 .

DISCUSSION. A novel method to determine the tensile properties of the TCL–CTC has been developed. The methodology has been validated and is capable of generating highly repeatable data.

References. [1] Ugbolue et al, Br J Sports Med, 48: A69-A70, 2014; [2] Holmes et al J Orthop Res, Nov; 29(11): 1682-7, 2011; [3] Li et al, J Biomech Eng, 131(8): 081011 (6 page) (Abstract), 2009.