Variable angle locking intercarpal fusion system for four-corner arthrodesis: indications and surgical technique.

Four-corner fusion (4CF) is an accepted and regularly performed procedure when managing posttraumatic degenerative disorders in the wrist. This procedure consists of excision of the entire scaphoid in association with midcarpal fusion of the remaining four ulnar carpal bones (hamate, capitate, lunate, and triquetrum). In the majority of cases, the long-term outcome is a functional painless wrist. However, the exact procedure to best achieve a rapid solid bone union of the fusion mass without hardware complications remains controversial. The authors have developed a precise system to ensure precise positioning, firm fixation, and fusion at the midcarpal joint together with an early postoperative recovery, avoiding some of the issues reported with other implants used for 4CF. The described implant is a circular plate accommodating variable angle locking screws as well as compression screws that can firmly fix the plate to the carpal bones. The locking technology produces a very solid construct. A special reaming-distraction-compression guide has also been developed to both countersink the plate on the underlying carpal bone mass and allow distraction of the midcarpal joint for debridement and cancellous bone graft interposition. The features of the implant, its surgical technique, and a relevant case are described.