In vivo metacarpophalanageal joint collateral ligament length changes during flexion

We investigated the in vivo length changes of the collateral ligaments of metacarpophalangeal joint during flexion. We obtained computed tomography scans of index, middle, ring and little fingers at 0 degrees, 30 degrees, 60 degrees and 90 degrees of joint flexion from six hands of six healthy adult volunteers. Three of them had their dominant right hand studied, and the other three had their non-dominant left hand studied. We measured and analysed the radial and ulnar collateral ligaments of each metacarpophalangeal joint from the reconstructed images. We found that the dorsal and middle portions of the both radial and ulnar collateral ligament lengthened progressively during digital flexion and reached the maximum at 90 degrees flexion. The length of the volar portion increased from 0 degrees to 30 degrees flexion and then decreased from 30 degrees to 60 degrees flexion, reaching the minimum at 90 degrees. In conclusion, three portions of collateral ligaments on both sides of the metacarpophalangeal joint have variable length changes during flexion, which act to stabilize the joint through its flexion arc.