The Association Between Distal Screw and Articular Subsidence in the Open Treatment of Intra-articular Distal Radius Fractures.

Purpose: This study investigated the association between volar plate screw position and postoperative radiographic outcomes in the open treatment of comminuted intra-articular distal radius fractures (DRFs). We hypothesized that increased distance from distal screws to subchondral bone is associated with early loss of reduction and articular subsidence.

Methods: We performed a two-center retrospective review over 10 years (2013-2023) for Arbeitsgemeinschaft für Osteosynthesefragen (AO) type C3 DRF treated with open reduction and volar locking plate fixation. We measured the distance from the distal screw to the subchondral bone (STSB), ulnar variance (UV), and volar tilt (VT) on initial postfixation and 6-week postoperative nonstandardized wrist radiographs, as well as second metacarpal cortical percentage (2MCP) on initial radiographs. Plate positioning was categorized using the Soong classification, and instability was graded using the Lafontaine criteria. Immediate after surgery and 6-week follow-up radiographic measurements were compared. Multivariable logistic regression models were used to evaluate factors associated with loss of UV and VT.

Results: Initially, 540 patients were identified, with 178 remaining after exclusion. We found a statistically significant difference in median STSB distance between the immediate postoperative period (2.8 mm) and the 6-week follow-up (2.0 mm). A significant difference between immediate and 6-week postoperative UV was also present. After adjusting for appropriate covariates (age, initial 2MCP, and Lafontaine's criteria for instability), patients with initial STSB >3 mm had increased odds of an increase in UV >2 mm compared to patients with <3 mm STSB. Bone density (2MCP), perioperative Soong classification, and instability were not associated with UV change.

Conclusions: In this two-center retrospective cohort of comminuted intra-articular DRFs, we found that placing the distal row of screws greater than 3mm from subchondral bone was associated with increased odds of worsening UV.

Type of study/level of evidence: Prognostic IV.