Morphological analysis of the transverse carpal ligament

Abstract

Transection of the transverse carpal ligament (TCL) for carpal tunnel syndrome is commonly performed, yet actual knowledge of TCL morphology is rudimentary and the anatomical terminology is inconsistently used. The purpose of this study was to perform a morphological analysis of the TCL, to redefine the anatomical terminology concerning the TCL and surrounding structures, and to evaluate any correlation between external, measurable hand dimensions, and TCL dimensions. A silicone casting technique and digitization were employed to measure the morphology of the TCL in cadaveric specimens and to construct a three-dimensional TCL model. The TCL was the thickest distally at the midline and ulnar segments and the thickest proximally at the radial segment. External hand dimensions did not significantly correlate with TCL dimensions. The TCL thickness distribution is variable along the radioulnar axis. The thickness of the TCL was 2.1 ± 0.8 mm, ranging from 1.3 to 3.0 mm.

Figure 1

Proper positioning of the dissected specimen in the apparatus ready for pouring of the silicone cast is shown, with the aluminum plate in place and the boom tightened, the specimen securely attached to the splint and apparatus with a threaded pin, and the proximal extent of the antebrachial fascial occluded with gauze.

Figure 2

The definition of the TCL. a The TCL is highlighted on one of the cadaveric specimens. b An enlarged outline of the TCL is shown with the grid system developed to quantify thicknesses throughout the TCL. The small open circles represent the midlines between the scaphoid/trapezium and the pisiform/hamate (bones indicated by large open circles). The small closed circles represent the thickness points that were calculated.

Figure 3

A reconstructed three-dimensional computer model of the TCL from a left hand is depicted. The legend coordinate system is shown in the lower left-hand corner. Solid arrows imply structures projecting out from the page toward the reader; dotted arrows imply structures projecting behind the page away from the reader.

Figure 4

TCL thickness from proximal to distal along the radial, midline, and ulnar portions of the TCL.