Salvage of Painful Porous Coated Stem Ulnar Head Prosthesis With Semiconstrained Distal Radioulnar Joint Arthroplasty

Purpose: To determine the functional outcome and complications after conversion from a painful and unstable ulnar head prosthesis to a semiconstrained distal radioulnar joint arthroplasty. Methods: We conducted a retrospective review of 11 ulnar head prostheses in 10 patients with porous coated stems that were revised to semiconstrained prostheses. The median age of the patients was 47 years. The median number of wrist surgeries prior to conversion was 4 (range, 1–9). The median time from the ulnar head implant to the revision surgery was 47 months. Pre- and postoperative pain levels were recorded. Mayo Wrist Scores were calculated. Grip strength, range of motion, and complications and reoperations were recorded. Results: All patients reported moderate or severe pain before surgery, whereas 3 patients reported moderate pain after surgery. The Mayo Wrist Score improved considerably from a median of 50 before surgery to 65 after surgery. The grip strength and forearm pronation-supination showed no change following surgery. The median wrist flexion-extension range improved considerably. Follow-up was a median of 64 (range, 15–132) months after revision surgery. Removal of the ulnar head implant was described as difficult by the surgeons, except in 1 case where the implant was loose. Resection of bone from the distal ulna was often necessary. One patient needed a reoperation requiring prosthesis removal for aseptic loosening of the stem 5 years after revision. There were 2 nondisplaced periprosthetic fractures successfully treated with cast immobilization and 2 additional minor complications, 1 postoperative stitch abscess, and 1 extensor carpi ulnaris tendinitis. Conclusions: Conversion from an ulnar head implant to a semiconstrained prosthesis provided improved pain scores and function with a low reoperation rate in this patient series. Removal of an ulnar head prosthesis can be technically challenging, but it can be performed leaving enough bone stock for immediate implantation of a semiconstrained implant. Type of study/level of evidence: Therapeutic V.