Study of length changes in the collateral ligament during movement of the metacarpophalangeal joint

Abstract

Objective To investigate changes in collateral ligament length during flexion and extension of the metacarpophalangeal joint (MCJ) of the four fingers. Methods Spiral CT scans of the MCJ of the index, middle, ring and little fingers were obtained from 6 volunteers. Images from the mid-metacarpal to midproximal phalanx were acquired while the MCJ moved from 0° of flexion to 90° of flexion with 30° inerements.Changes in length of the collateral ligament of MCJ of each individual finger during MCJ movement were analyzed by software processing after three-dimensional image reconstruction of bone structures were obtained. Results During flexion of the MCJ the dorsal bundle of the ulnar and radial collateral ligaments lengthened, while the volar bundle shortened. The length of the middle bundle did not change significantly. Conclusion During MCJ flexion and extension, the collateral ligaments are in a state of tension. However tension in different portions of the ligament varies. There are two main relative movements during MCJ flexion: lengthening of the dorsal bundle of the collateral ligament results in increased tension and shortening of the volar bundle results in decreased tension. The middle bundle always maintains proper tension, restricting and regulating the movement of the joint. Key words: Metacarpophalangeal joint; Collateral ligaments; Movement; Length changes; In vivo study