Role of the juncturae tendinum in preventing radial subluxation of the extensor communis tendons after ulnar sagittal band rupture: a cadaveric study.

N Greville Farrar,Amrit Kundra

doi:10.5402/2012/597681

Abstract

Background. Radial subluxation of the extensor communis tendons at the metacarpophalangeal (MCP) joints is a rarely reportedvinjury. These injuries have proved difficult to reproduce in cadaveric studies and have a low biomechanical likelihood of occurrence due to the ulnar direction of pull of the extensor communis tendons. It has been suggested that the juncturae tendinum may have a stabilising role, preventing radial subluxation after ulnar sagittal band rupture; however this has not been established. Methods. 40 cadaveric digits were dissected to reveal the extensor mechanism around the MCP joints. The ulnar sagittal bands were released and then the juncturae tendinum divided, in stages, before observing for radial subluxation or dislocation during finger flexion. Results. Radial subluxation of the extensor tendon was observed in only one digit after complete ulnar sagisttal band release. When all the fingers were flexed, after the juncturae tendinorum were divided, four additional tendons subluxed radially and a fifth tendon dislocated in this direction. When the digits were then flexed individually, there were eight unstable tendons in total. Conclusions. The juncturae tendinum appear to have a role in stabilising the extensor communis tendons at the MCP joints and preventing radial subluxation after ulnar sagittal band rupture.

Highlights

Radial subluxation of the extensor communis tendons at the metacarpophalangeal (MCP) joints is a rarely reportedvinjury
It has been suggested that the juncturae tendinum may have a stabilising role, inhibiting radial subluxation after ulnar sagittal band rupture; this was not tested [6]
Without the availability of X-ray in the anatomy department we could not comment on subtle arthritic changes which could interfere with the MCP joint motion, but there were no gross arthritic changes noted in the specimens used

Summary

Background

Ulnar subluxation of the extensor communis tendons at the metacarpophalangeal (MCP) joints occurs chronically in the rheumatoid hand, for which surgical repair is a well-established technique [1]. The ulnar direction of pull of the extensor communis tendon, from its origin at the lateral epicondyle of the humerus, is at its greatest at the index finger MCP joint and least at the small finger MCP joint These biomechanical principles were mirrored in the results of a cadaveric study, with ulnar instability proving to be most pronounced at the index finger and least at the small finger [7]. It has been suggested that the juncturae tendinum (intertendinous connections) may have a stabilising role, inhibiting radial subluxation after ulnar sagittal band rupture; this was not tested [6] This cadaveric study aimed to investigate the occurrence and mechanism of radial subluxation of the extensor tendons at the MCP joints, including the potential stabilising role of the juncturae tendinum

Methods

Results

Conflict of Interests