Lunate Implant Arthroplasty: Evaluation of 19 Patients

Abstract

The results of lunate implant arthroplasty are unpredictable and many untoward postoperative problems are encountered. A retrospective review of 19 patients operated on for lunatomalacia (Kienbock's disease) by Silastic (HP) implant arthroplasty suggests that prevention of postoperative scapholunate dissociation seems to be the key to successful results. Knowledge of the predominant role played by the palmar ulnolunate and radiolunate ligaments is important to the understanding of this mechanism. The intrinsic stability accomplished by the geometry of the carpal bones requires adequate ligamentous support. This restraint, however, may be weakened by pre-existing absence of certain palmar fibres, by the disease process or by the surgery. In the present study three operative methods have been assessed: dorsal approach and implant stem fixation; dorsal approach, removal of implant stem and Kirschner-wire fixation; volar approach, removal of implant stem, no internal fixation but palmar capsuloligamentous reinforcement. Consistently good results have been obtained using the latter technique. It seems as if most of the usual postoperative problems of lunate implant arthroplasty can be avoided by this method which warrants continued trial.

Although in the past many methods of handling lunatomalacia (Kienbock's disease) have been recommended, there is still no general agreement upon the optimum treatment of this disorder. In 1980 we reviewed our experiences with radial shortening and found that the best results were obtained when the operation was performed early before significant degeneration of the lunate and surrounding carpus had occurred. (Eiken & Niechajev). In a simultaneous series, 14 patients underwent denervation of the wrist for pain from Kienbock's disease, applying the technique described by Wilhelm (1966). A satisfactory long-term pain relief was obtained, but radiographic assessment revealed progression of the disease and rapid deterioration of the lunate (Ekerot, Holmberg & Eiken, 1983).

Since 1978 additional 19 patients have been operat-ed upon, replacing the diseased lunate by the new high-performance Silastic implant manufactured by Dow Corning. The operative technique was initially as described by Swanson (1970). However, several problems occurred, which by degrees necessitated technical modifications. The aim of this study is therefore to correlate the different postoperative problems with the operative method used.