Carpal Instability Nondissociative Following Acute Wrist Fractures.

PURPOSE: Carpal malalignment following intra-articular fractures has been reported in the literature, with no clear description of possible ligamentous injury leading to the radiological appearance. This study presents a series of patients that developed carpal instability nondissociative (CIND) following acute wrist fractures. The mechanism of injury is postulated by using a cadaveric laboratory investigation.

METHOD: Twelve patients with average age of 32 years were identified with CIND, between 2013 and 2018. Ten patients with a normal carpal alignment in the initial postoperative radiographs exhibited CIND-palmar radiographically at different postoperative periods, and 2 patients showed CIND-dorsal in the initial postoperative x-rays. Four cadaveric specimens were used to validate this injury pattern.

RESULTS: In cadaveric dissections, CIND-palmar could be reproduced by applying an axial loading and dorsal shearing force on a wrist with sequential sectioning of dorsal and palmar extrinsic wrist ligaments. For the intra-articular fractures with CIND-dorsal, the cause is likely a result of volar radiocarpal extrinsic ligament injury combined with intra-articular incongruity of the scaphoid fossa. Eight out of the 12 patients had severe wrist pain and underwent additional surgery. Three patients with reducible CIND-palmar had open capsular repair, and 5 patients with fixed nonreducible malalignment were treated with radioscapholunate arthrodesis. At an average follow-up of 2.3 years, pain relief was noted, together with an improvement in grip strength and range of movement. Radiographically, the wrist alignment was corrected and maintained.

CONCLUSIONS: This article highlights the existence of possible concomitant radiocarpal ligament lesions and residual articular incongruity, associated with acute intra-articular fractures and radiocarpal fracture-dislocations, that destabilize the proximal carpal row into a pattern of nondissociative carpal instability. Early detection of this condition may preserve wrist function by capsular repair, whereas cases with fixed deformity and residual joint incongruity may be best managed with a limited radiocarpal arthrodesis.

TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic IV.