Use of an ulnar head endoprosthesis for treatment of an unstable distal ulnar resection: review of mechanics, indications, and surgical technique.

Resection of the distal ulna for post-traumatic arthritis can lead to an unstable forearm joint through loss of the normal articular contact through the distal radioulnar joint and loss of soft tissue constraint. The resulting convergence instability can lead to residual pain, weakness, and loss of function. Restabilization of the forearm joint with implantation of an ulnar head endoprosthesis can re-establish the mechanical continuity of the forearm, reducing pain and improving strength and function. The anatomy, mechanics,rationale, and indications for surgical replacement of the distal ulna are presented. Important tenets of proper ulnar head implant insertion are given to provide a guide for use of the implant. Preliminary results after 2 years of clinical experience are encouraging.