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Thenar and hypothenar muscle origins on the transverse carpal ligament
David B Jordan1, Hui Zhang1, Mary N Henderson1
1Hand Research Laboratory, Department of Orthopaedic Surgery, University of Arizona College of Medicine, Tucson, Arizona, USA.
Abstract:
The thenar and hypothenar muscles of the hand have origins on the transverse carpal ligament (TCL). Understanding the morphological distribution of this muscle-ligament interaction has clinical and biomechanical benefits. Robot-assisted ultrasonography was used to reconstruct the three-dimensional TCL volar surface and TCL-muscle interface in ten cadaveric specimens. The interface areas and radial-ulnar length at discretized proximal-distal tunnel levels were calculated. The total area of the TCL volar surface was 457.4 ± 62.2 mm2. The TCL-thenar and TCL-hypothenar interface areas were 142.3 ± 38.0 mm2 (30.8 ± 6.6%) and 32.3 ± 22.4 mm2 (7.0 ± 4.7%), respectively. The TCL area not interfaced by the thenar or hypothenar muscles was 282.72 ± 40.8 mm2 (62.1 ± 7.4%). The relative radial-ulnar TCL-muscle interface length was significantly dependent upon muscle group (p < 0.001) and proximal-distal carpal tunnel level (p < 0.001). The maximum percentage of the radial-ulnar length of the TCL volar surface occupied by the TCL-thenar and TCL-hypothenar interface was 57.0 ± 9.9% and 15.5 ± 9.6%, respectively. Quantification of the three-dimensional muscle coverage distribution on the TCL can help to advance anatomical understanding, inform biomechanical mechanisms for utilizing the muscle-ligament interaction, and minimize potential functional disruption of carpal tunnel release.
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