Patterns of subchondral bone mineralization in the wrist after midcarpal fusion

Midcarpal fusion represents a salvage procedure in cases of advanced carpal collapse, which unloads the scaphoid compartment and redirects the load to the intact lunate compartment of the radiocarpal joint. The aim of this study was to obtain further information about the loading conditions in the living subject by evaluating the pattern of subchondral bone mineralization in patients who have undergone midcarpal fusion of the wrist. Between 4 and 42 months after the surgery, 9 male patients were examined by means of computed tomographic osteoabsorptiometry. All of them showed peak mineralization in the lunate fossa of the radius. Six patients had only one large density maximum in this fossa and no corresponding maximum in the scaphoid fossa. In accordance with our expectations, loading after midcarpal fusion was found to be transmitted mainly through the lunate compartment, a result that was observed even after as little as 4 months, and that thus confirmed subchondral bone mineralization as a valuable parameter for assessment of long-term stress distribution.