Critical review Rationale of salvage procedures for failed resection arthroplasties of the distal radio-ulnar joint

Introduction When a distal radio-ulnar joint (DRUJ) causes refractory pain and there is extensive damage to the joint cartilage, the only available surgical option is to sacrifice the joint by complete resection of the distal ulna (popularized by Darrach), by partial resection with or without interposition (e.g. Bowers’ hemiresection or Watson’s ‘matched ulna’) or by fusion of the radius and distal ulna with proximal pseudoarthrosis [Sauvé-Kapandji (S-K) procedure]. These options, especially Darrach’s resection, have been widely used, and the satisfactory pain and mobility outcomes achieved (>80%) have long been documented1. However, it is increasingly acknowledged that these arthroplasties can fail, with patients reporting pain and weakness in grip and object lifting, and even clunking with pronosupination due to instability of the distal forearm2,3. This instability takes place in the anteroposterior plane, with X-rays showing radioulnar convergence and wear in the medial cortex of the radius at the ulnar stump end4 (Figure 1). This complication is reported as radioulnar impingement syndrome2 or convergent instability of the distal ulnar stump5, and various dynamic radiographic studies have used different methods to determine its frequency and the influence of distinct procedures or techniques on this loss of stability. Since the introduction of a novel radiographic view by Lees and Scheker in 19976, radiographic radio-ulnar convergence has been observed in 100% of cases and affects patients equally after Darrach’s resection, S-K procedure, or partial resection (Figure 2). One explanation that has received little attention is that DRUJ is a load joint and critical for lifting objects. When a weight is held in the hand with the elbow flexed and forearm in neutral rotation, the radius is centred on the ulnar head, producing a transverse load and exerting a compressive force7. Moreover, the contraction of the muscles connecting the ulna and radius favours convergence once these bones are free of contact with the ulnar head. García-Elias demonstrated the role of the anterior brachial muscle, pronator quadratus and long abductor muscle of the thumb in this phenomenon8 (Figure 3), whereas other authors highlighted the role of the short thumb extensor and the flexor digitorum profundus of the second and third fingers. The percentage of distal ulna resections with symptoms of radioulnar impingement ranges between 8% and 50%, depending on the series. Although no association has been established with any specific radiographic parameter, an excessively high ulnar osteotomy appears to have a negative effect9. It has been claimed that the ulnar stump meets an area of the radius that is unfavourable for contact8, but we believe that there may be more important biomechanical causes of this complication. In DRUJ surgery, the instability of the distal ulna can be reduced by preserving soft tissue stabilizers such as the triangular fibrocartilage complex (TFCC) and radio-ulnar ligaments, posterior ulnar tendon sheath, interosseous membrane and * Corresponding author Email: [email protected]