Anatomy of the Thumb Metacarpophalangeal Ulnar and Radial Collateral Ligaments

PurposeTo describe the origin and insertion of the ulnar (UCL) and radial collateral ligaments (RCL) of the thumb metacarpophalangeal (MCP) joint.MethodsWe dissected 18 UCLs and 18 RCLs from fresh-frozen human cadaveric thumbs. We removed all soft tissue overlying the MCP joint, isolating the proper collateral ligaments. We detached the collateral ligaments from the bone while marking their origin and insertion points and measured these attachment sites in relation to bony landmarks by digital photo analysis.ResultsThe center of the UCL origin at the metacarpal was 4.2 mm from the dorsal surface and 5.3 mm from the articular surface. The dorsal aspect of the metacarpal origin site was 2.1 mm from the dorsal edge of the metacarpal. The center of the phalangeal insertion was 2.8 mm from the volar surface and 3.4 mm from the articular surface. The volar aspect of the phalangeal insertion site was 0.7 mm from the volar edge of the phalanx. The center of the RCL origin at the metacarpal was 3.5 mm from the dorsal surface and 3.3 mm from the articular surface. The dorsal aspect of the metacarpal origin site was 1.5 mm from the dorsal edge of the metacarpal. The center of the phalangeal insertion was 2.8 mm from the volar surface and 2.6 mm from the articular surface. The volar aspect of the phalangeal insertion site was 0.5 mm from the volar edge of the phalanx.ConclusionsOur study accurately defined the origin and insertion sites of the UCL and RCL of the thumb MCP joint.Clinical relevanceAn accurate definition of the anatomical origin and insertion points of the thumb MCP UCL and RCL may allow for more successful surgical repair and reconstruction.