Case: Carpal (wrist) arthrodeses (joint fusions)
29th December 2013
Fusion of the carpal joints is often indicated when there is irrevocable traumatic damage to the joint often involving ligament damage. Hyperextension of the carpus commonly results when dogs leap down a long drop. Some breeds like Shelties are especially prone to spontaneous collapse of the carpal (or tarsal) joints under normal loading. Carpal arthrodesis can be indicated when the carpal joints are involved with articular fractures, or when degenerative joint disease is present that is not effectively managed by other means.
The carpus is a complex group of joints with multiple levels of motion. There is a high motion joint level between the radius/ulna (the bones of the forearm) and two rows of low motion ones where bones are restricted from moving with respect to each other by a tight arrangement of ligaments. When injury only involves the low motion part(s), then often a partial arthrodesis can sometimes be done and the high motion part is spared which potentially saves the great majority of function. When the high motion joint is affected, then a pancarpal arthrodesis is required that aims to fuse the carpus in its entirety with loss of function of all of the joint levels. Even in the case of pancarpal arthrodesis, the functional result is usually very good.
Fusion of the bones that made up the joint takes at least a few weeks. The metalwork that is used to bridge the joints occasionally needs to be taken out at some point.
A variety of different types of plates can be used. In the carpus some screw into one metacarpal and some screw into two. Some use conventional cortical screws and some use locking screws.