[Reconstruction of the distal radioulnar joint using the Herbert ulnar head prosthesis].

Objective: To provide painfree forearm rotation in patients with degenerative changes of the distal radioulnar joint (DRUJ). The primary goal is to stabilize the DRUJ in patients with an unstable stump of the distal ulna following resection arthroplasty with the secondary effect of restoring painfree forearm rotation.

Indications: Instability of the distal ulna following various types of resection arthroplasties. Primary or secondary osteoarthritis of the DRUJ. Replacement of an ulnar head destroyed by tumor or trauma.

Contraindications: Longitudinal instability of the forearm (e.g., following an Essex-Lopresti-type of injury, resection of the radial head). Inadequate soft tissue with severe ulnocarpal ligamentous insufficiency. Radial deformity (must be corrected before replacement of the ulnar head).

Surgical Technique: In cases of osteoarthritis of the DRUJ, dorsal exposure of the distal radioulnar joint to the depth of the 5th extensor compartment. Raising of an ulnar-based capsuloretinacular flap by sharp dissection off the ulnar neck proximally and off the dorsal part of the triangular fibrocartilage complex (TFCC) distally. Osteotomy of the distal ulna corresponding to the preoperatively planned size of the prosthesis and removal of the ulnar head, while preserving the attachment of the TFCC within the capsuloretinacular flap. Reaming of the ulnar medullary canal. Insertion of a trial prosthesis. The trial prosthesis has to fit accurately into the shaft with a fluoroscopically documented ulna minus situation of minus 1-2 mm at the wrist joint level. After implanting the definite stem and ulnar head of the Herbert ulnar head prothesis (Martin Medizintechnik®, Tuttlingen, Germany), the capsuloretinacular flap is reattached to the dorsal rim of the sigmoid notch through drilling holes and under advanced tension. In patients with an unstable distal ulnar stump, the operative procedure is technically more demanding as it is more difficult to raise a sufficient capsuloretinacular flap and due to the loss of the ulnar head as an anatomic landmark.

Postoperative Management: Long arm cast with 70° elbow flexion, 40° forearm supination, and 20° wrist extension for 2 weeks. Subsequently forearm rotation is limited at 40° in a removable ulnar gutter splint. Six weeks postoperatively unlimited active range of motion is allowed and normal activities are gradually commenced. Return to maximum stress 12 weeks postoperatively.

Results: Patient satisfaction is high due to an increased forearm rotation, stronger grip force, and remarkable pain relief. In most patients with an unstable distal ulnar stump following resection arthroplasty of the DRUJ, stability can be restored.