New concept for total wrist replacement.

Wrist prostheses have never achieved the sort of clinical outcomes found with those of hips and knees. We have developed a novel uncemented modular wrist prosthesis with screw fixation, metal-on-metal coupling, and ball-and-socket articulation. Eight patients admitted for wrist arthrodesis to treat primary or secondary osteoarthritis (not rheumatoid) were operated on. The prosthesis reduced the amount of bone removed and spared the distal radioulnar joint. After 7 to 9 years we found that the fixed centre of the ball-and-socket articulation provided good stability and mobility, and relief of pain and grip strength were satisfactory. We saw no luxations, metacarpal fractures or cut-outs, or mechanical failures of the implants. Two distal screws loosened (revised with new distal screws), and one early inflammation and one late infection occurred (revised to arthrodesis). We propose modifications to the implant with reduction in the diameter of the screws and the height of the threads, and rounding of the distal tip. The technique should include release of the third carpometacarpal joint, alignment of the capitate and the third metacarpal, and arthrodesis of the joint with bone chips.