Narrowing carpal arch width to increase cross-sectional area of carpal tunnel--a cadaveric study

Abstract

Background: Carpal tunnel morphology plays an essential role in the etiology and treatment of carpal tunnel syndrome. The purpose of this study was to observe the morphological changes of the carpal tunnel as a result of carpal arch width narrowing. It was hypothesized that carpal arch width narrowing would result in increased height and area of the carpal arch.

Methods: The carpal arch width of eight cadaveric hands was narrowed by a custom apparatus and cross-sectional ultrasound images were acquired. The carpal arch height and area were quantified as the carpal arch width was narrowed. Correlation and regression analyses were performed for the carpal arch height and area with respect to the carpal arch width.

Findings: The carpal tunnel became more convex as the carpal arch width was narrowed. The initial carpal arch width, height, and area were 25.7 (SD1.9) mm, 4.1 (SD0.6) mm, and 68.5 (SD14.0) mm(2), respectively. The carpal arch height and area negatively correlated with the carpal arch width, with correlation coefficients of -0.974 (SD0.018) and -0.925 (SD0.034), respectively. Linear regression analyses showed a 1mm narrowing of the carpal arch width resulted in proportional increases of 0.40 (SD0.14) mm in the carpal arch height and 4.0 (SD2.2) mm(2) in the carpal arch area.

Interpretation: This study demonstrates that carpal arch width narrowing leads to increased carpal arch height and area, a potential mechanism to reduce the mechanical insult to the median nerve and relieve symptoms associated with carpal tunnel syndrome.

Copyright © 2013 Elsevier Ltd. All rights reserved.

Figures

Figure 1

Experimental setup for carpal arch width narrowing (A) and ultrasound imaging (B)

Figure 2

Ultrasound images of a representative specimen at (a) its initial CAW of 26.7 mm, (b) 1 mm narrowing of the CAW, (c) 2 mm narrowing of the CAW, and (d) 3 mm narrowing of the CAW. The yellow boxes are the regions of interest with their centroids at the most palmar aspect of the hamate and the trapezium.

Figure 3

Representative curves of the transverse carpal ligament at different CAWs. The labels 0, 1, 2 and 3 indicate conditions of CAW narrowing of 0, 1, 2 and 3 mm, respectively.

Figure 4

Carpal arch heights at different carpal arch widths for individual specimens.

Figure 5

Carpal arch areas at different carpal arch widths for individual specimens.