[Radioulnar impingement after distal ulnar resection and ulnar head hemiresection interposition arthroplasty (Bowers procedure). An experimental biomechanical study].

Resection of the distal ulna (Darrach operation) and the ulnar head hemiresection interposition arthroplasty (Bowers procedure) are common methods of treating the arthrotic distal radioulnar joint (DRUJ). The purpose of this study was to evaluate the dynamic effects of both the Bowers operation and the resection of the distal ulna on radioulnar impingement and dorsal-palmar displacement and to compare their biomechanical performances. With a dynamic forearm simulator forearm rotation was performed with simultaneous loading of relevant muscles. Torque along the forearm axis was generated by simulated muscle action with loading of the relevant tendons while the wrist was constrained to prescribed ranges of motion. The instability of the radius relative to the ulna was evaluated using displacement data of digitized landmarks in an ulnar coordinate system. Seven fresh-frozen cadaver upper extremities were used. Resection of the distal ulna created a significant instability of the forearm with movement of the radius ulnarly. Anteroposterior translations in each loading condition could be detected as well but the magnitude of displacement was little and less predictable. The results of the Bowers operation demonstrated significantly less instability compared with the Darrach results. Our data demonstrates that the dynamic behavior of the Bowers procedure is superior to the mechanical performance of complete resection of the distal ulna.