The superficial transverse metacarpal ligament and the interdigital web. A proof-of-concept study based on palpation,...

This study, based on palpation, ultrasonography, casts, and dissection, aimed to identify the superficial transverse metacarpal ligament and further characterize the interdigital web, including skin gliding, slope's angle and length, histology, and dynamic changes during finger abduction.

The preferred hand of 10 healthy participants was studied by palpation and ultrasonography. Alginate casts of the webspace were obtained from seven healthy volunteers. Five cadaver hands were dissected for illustration and to histologically evaluate the dorsal and palmar web. Descriptive and non-parametric statistics were used.

The superficial transverse metacarpal ligament was detected through palpation in finger abduction at the webs, with an estimated width of about 7.1 mm. Ultrasonography was used to trace this ligament throughout its course and measure its thickness, with a median value of approximately 0.46 mm. Both palpation and ultrasonography revealed its proximal transverse and distal arciform fibres. The latter extended along the proximal phalanges. At the fleshy web, skin gliding was assessed by palpation. Both ultrasonography and dissection allowed for measuring the skin, which was thicker on the palmar side. Elastic fibres predominated on the dorsal side, and dense collagen on the palmar side. The alginate casts revealed that during finger abduction, the dorsal web opened as a curved triangle with the web's edge, digital extensions, and dorsal skin as a checkrein.

Palpation, ultrasonography, and dissection detected complementary features of the natatory ligament and the interdigital space. The alginate casts revealed that the dorsal web opened as a curved triangle. Dissection provided detailed information about the involved structures.