Reduction and Association of the Scaphoid and Lunate (RASL) Reconstruction for Chronic Static Scapholunate Instability

Scapholunate injury is a frequent result from a fall on the extended wrist. It is a continuum of presentations from a mild sprain to a complete disruption of the scapholunate ligament. The clinical finding may be mild discomfort over the dorsum of the wrist at first which can then progress to significant limitation of wrist function due to pain and instability. Radiographic findings vary from normal X-rays to a complete malalignment of the proximal carpal row with the development of the dorsal intercalated segmental instability pattern, DISI. Chronic scapholunate instability leads to progressive arthritis in the scapholunate advanced collapse pattern, SLAC. Unfortunately, many patients initially present with SLAC 1 arthritic changes with a flexed scaphoid abutting the radial styloid. This condition is associated with pain and resultant weakness precluding activities which require loading the wrist in extension. Many soft tissue linkage procedures have been tried and most have failed to maintain carpal alignment and correct diastasis of the scapholunate joint. The reduction and association of the scaphoid and lunate (RASL) procedure has been performed with a high measure of reliability for over 30 years but like all surgical procedures requires attention to detail to obtain a durable and satisfactory outcome. One must ensure via diagnostic arthroscopy that there is no unrecognized progression to advanced SLAC into the midcarpal joint. A small radial styloidectomy which does not detach any radiocarpal ligaments must be performed to obtain access to the correct starting portal on the dorsal radial ridge of the scaphoid. This will allow proper targeting in the mid sagittal axis of the reduced lunate and placement of the transosseous dumbbell-shaped headless bone screw. A reduction of the DISI deformity is obligatory prior to placing the guide wire for the screw. This can be achieved using a joystick “walk up” derotation technique which is possible even in chronic static SL instability cases. The interface between the scaphoid and lunate must be de-chondrified exposing cancellous bone to allow for fibrovascular ingrowth and the creation of a neo-ligament. Motion is allowed at 2 weeks post surgery, but power activities are restricted for 3 months to allow for maturation of the repair tissue. Patients have been followed for an average of 12 years with excellent motion and function. Revisions are few and related to deviations of technique or indication.