The EWAS Classification of Scapholunate Tears: An Anatomical Arthroscopic Study

Scapholunate interosseous ligament (SLIOL) tears, according to the studies of Mayfield, develop in a predictable pattern after a trauma in extension, ulnar deviation, or intercarpal supination. The volar part of the scapholunate ligament is involved first, then the whole SLIOL, then the extrinsic ligaments such as the radioscaphocapitate (RSC) ligament and the radiotriquetral (RT) ligament with a variable degree of ligament damage.1 They occur mainly in young patients of working age, who may develop wrist instability, which can eventually lead to degenerative arthritis and a scapholunate advanced collapse (SLAC) wrist.2,3 Once arthritis has developed, the treatment of these lesions is not simple and generally requires salvage procedures with a significant loss of wrist function. Treatment of a chronic scapholunate ligament tear is still a challenge for the surgeon, even before wrist arthritis has developed, since it is not always possible to regain complete wrist strength, motion, and stability.4,5 Early identification and treatment of scapholunate tears is thus advisable as well as useful in understanding their anatomopathological development. The development of wrist arthroscopy has greatly helped in the identification of intracarpal ligament lesions and allowed for their early identification.6,7,8 In 1993, Dautel described a method for identifying occult scapholunate ligament injuries, not visible radiographically, by probing the scapholunate joint arthroscopically through the midcarpal joint. Geissler, in 1995, published a four-stage arthroscopic classification system of scapholunate ligament instability in patients with a distal radius fracture; this is widely used today.6 Dreant published a similar classification based on a mid-carpal instability test.9 Lindau described measuring the scapholunate gap arthroscopically using the arthroscopic probe.10 The existing classifications, however, describe the dynamic instability of the scapholunate joint but do not distinguish the site of ligament attenuation or tear per se, particularly in its volar portion. Some authors have identified isolated tears of the volar SLIOL and tears of the extrinisic lesions which have led to the development of open and arthroscopic repair methods.11,12,13,14,15 Moreover, many anatomical studies on cadaver specimens to establish the SLIOL's and extrinsic ligament's role in wrist stability have been performed by open approach,16,17,18,19,20,21,22 but only one has been done by arthroscopy.23 This prompted us to develop for the European Wrist Arthroscopy Society (EWAS) a more comprehensive classification that includes the site of the scapholunate ligament attenuation or tear.24,25 The purpose of this study was to selectively section the different portions of the SLIOL, followed by the volar and dorsal extrinsic ligaments, and then describe the subsequent arthroscopic findings.24,25