Comparative Study of Radiologic Changes in Ulnar Variance and Ulnolunate Distance After Distal Radius Fracture Surgery: Patients with vs. Without Lunate Ulnar Corner Cysts

Background: Subchondral cysts at the ulnar corner of the lunate are frequently encountered in patients with distal radius fractures. We hypothesized that the presence of these lunate subchondral cysts may be associatedwith decreased cortical bone density due to limited load translation. Consequently, this could lead to lunate fossa collapse and increased ulnar variance following fracture fixation. Methods: A retrospective analysis was performed on 176 patients who underwent open reduction and internal fixation using the Double-tiered Subchondral Support (DSS) procedure between May 2014 and June 2017. Twenty-eight patients identified with lunate subchondral cysts on preoperative CT scans were selected as the study group. A control group of 28 patients without cysts was selected using matched-pair analysis, controlling for gender, age, fracture classification, and follow-up period. Results: The mean change (delta) in ulnar variance was 0.191 mm in the cyst group, which was less than the 0.233 mm observed in the control group; however, this difference was not statistically significant (p = 0.557). Regarding ulnolunate distance, the cyst group showed a mean change (delta) of 0.991 mm, while the control group showed a change of 1.123 mm. This difference was also not statistically significant (p = 0.681). Conclusions: Although it was hypothesized that lunate subchondral cysts might limit load translation to the radius and compromise cortical bone density—potentially affecting fracture healing and the maintenance of reduction—our statistical analysis did not support this hypothesis. The presence of lunate subchondral cysts did not significantly increase the risk of lunate fossa collapse or ulnar variance progression compared to the control group.