Re: Sun et al. Association of scapholunate dissociation and two-part articular fractures of the distal radius. J Hand Surg Eur. 2019, 44: 468–74

We read this article with great interest. Awareness in terms of which distal radial fractures that could be associated with concomitant scapholunate (SL) ligament injury is an important issue. Mudgal and Hastings (1993) have described that concomitant SL injury is very common in Chauffeuŕs fractures and Scheer and Adolfsson (2011) have proposed that injury to the triangular fibrocartilage complex (TFCC) can be expected when the dorsal angulation exceeds 32 . Otherwise, we have had no valid guidelines in terms of awareness of concomitant wrist ligament injuries in distal radius fractures, in spite of highenergy trauma and comminuted intra-articular fractures. Therefore, this article provides guidelines to clinical decision making, namely in which patients we should use arthroscopy-assisted surgery, when operating on the fractures. This is valuable, as the health care resources are not sufficient to cover arthroscopy-assisted surgery in all displaced distal radial fractures. Sun et al. have used axial computed tomography (CT) scans of acute two-part intra-articular radial fractures and have compared CT with normal radiographs. The authors showed significant increment in the SL distance in the following distal radial fracture subtypes: radial styloid oblique, dorsal ulnar column, sagittal ulnar column and volar coronal. CT is a static examination, and we are all aware that it often takes 3–12 months before a dynamic SL dissociation develops into a static deformity. Dynamic SL instability prior to the current trauma was not evaluated in the study by Sun et al., nor is the history of the patients in terms of possible prior wrist trauma clearly explained. We also miss a description of possible concomitant dorsal intercalated segment instability (DISI) on the CT scans, which could assume prior SL injury. The SL ligament varies from 2 to 5 mm in length and has some elasticity. Therefore, we think that a minor widening of the SL gap could be due to tension in the ligament according to displacement of the specific distal radial fracture fragments units, in some of the patients. It is also surprising that the authors did not find any bony avulsions in their cohort. Andersson and Garcia-Elias (2013) found 13% SL avulsion injuries with bony fragments in their surgical cohort of 45 patients. We believe that Sun et al. have significantly contributed to the pathomechanic understanding of distal radial fractures with concomitant SL injuries. They have provided a relevant guideline for higher threshold and awareness in which patients surgeons should aim for arthroscopy-assisted surgery at the same time as the distal radial fracture is operated on. But still, arthroscopy is the gold standard in terms of diagnostics of wrist ligament injuries and magnetic resonance imaging (MRI) or CT are unable to rule out the possibility of a clinically relevant injury to the wrist ligaments, including the SL ligament (Andersson et al., 2015).