Small volar fragment in the lunate fossa leads to volar tilt loss after volar plate fixation for AO/OTA type-C distal radius fracture

The relationship between volar fragment size and postoperative volar tilt loss in complete articular distal radius fracture is not well known. In this study, we measured precise radiological parameters to help identify other factors that might contribute to volar tilt loss.We retrospectively reviewed the radiological examinations and charts of 256 patients with distal radial fracture who underwent volar locking plate fixation between March 2014 and July 2022. Radiological parameters were measured based on preoperative CT and immediate postoperative radiographs. Univariate and multivariate linear regression analysis was performed to identify relevant factors associated with volar tilt loss following volar locking plate fixation. The receiver operating characteristic curve was used to identify the cutoff value of the independent parameters.On univariate analysis, 2 radiologic parameters on preoperative CT (volar fragment length at the lunate fossa, and teardrop angle) and 4 on immediate postoperative X-ray (radial inclination, radial length, capitate shift, and volar tilt) were significantly associated with postoperative volar tilt loss. On multivariate linear regression analysis, the risk of volar tilt loss increased as the capitate moved toward the back of the radial shaft. The cut-off for anteroposterior length in the lunate fossa was 6.5 mm.AO/OTA type-C distal radius fractures with <6.5 mm anteroposterior length in the lunate fossa had significantly higher rates of malunion with dorsal deformity. In addition, preoperative teardrop angle <37.2 ° and immediate postoperative volar tilt <3.7º are also predictors of postoperative volar tilt loss.