Early Radiographic Changes Predict Radiographic Stability in Distal Radius Fractures: Development and Validation of an Explainable Predictive Model.

Purpose: To determine whether early radiographic trajectory data can predict the timing of stability in conservatively managed distal radius fractures (DRFs) and to identify which clinical and radiographic features most influence stabilization timing. Methods: This retrospective cohort study analyzed data from 1,585 adult patients with conservatively managed DRFs collected from a single-institution fracture registry (2020-2024). Radiographic stability was classified according to predefined parameters of radial height, volar tilt, radial inclination, and ulnar variance at weekly follow-ups. An explainable machine learning model incorporating demographics, fracture characteristics, comorbidities, and early radiographic changes was developed to predict stability at various weeks. Predictive performance was evaluated using area under the receiver operating characteristic curve, calibration plots, Brier scores, decision curve analysis, and SHapley Additive exPlanations. Results: Among 1,585 patients, 40% of fractures achieved radiographic stability by week 3. Baseline radiographic measurements did not differ across stability groups, but first-week displacement differed significantly across all parameters. A combined model incorporating early radiographic changes substantially outperformed a baseline-only model. Decision curve analysis demonstrated a superior net benefit compared with routine imaging strategies. SHapley Additive exPlanations analysis identified early changes in volar tilt as the single most influential predictor, followed by changes in radial inclination, patient age, and dorsal comminution. Conclusions: Early radiographic trajectory, particularly first-week changes in volar tilt, predicts the timing of stability far more accurately than baseline features alone. A substantial proportion of conservatively managed DRFs stabilize earlier than conventional protocols assume, suggesting that a trajectory-guided approach could safely reduce late follow-up imaging and immobilization duration in selected patients. Prospective validation is needed before clinical implementation. Clinical relevance: First-week radiographic displacement, particularly changes in volar tilt, may be more informative than traditional baseline instability criteria for guiding follow-up frequency and immobilization duration in conservatively managed DRFs. Level of evidence: Prognostic/III.