Fracture mapping of coronal shear fractures of the distal humerus: morphological analysis and fixation efficacy.

backgroundCoronal shear fractures of the distal humerus exhibit complex morphology, presenting substantial challenges in clinical management. Fracture mapping technology provides a visual tool for elucidating fracture patterns. This study aimed to: (1) generate three-dimensional (3D) fracture line maps and heatmaps to identify fracture-prone regions and characterize morphological features; and (2) assess the suitability of pre-contoured locking plating systems for screw placement.

methodsA retrospective analysis was conducted on 135 coronal shear fractures of the distal humerus treated at two Level I trauma centers between May 2013 and January 2025. Two types of computed tomography (CT) datasets were used: preoperative post-injury CT (for fracture mapping) and postoperative CT (for plate suitability analysis). CT data were processed using Mimics 21.0 and 3-Matic 13.0 software to reconstruct 3D models. Fracture lines were superimposed onto a standardized 3D distal humerus template to create fracture line maps and heatmaps. Fractures were classified according to the modified Dubberley classification system (MDCS), AO/OTA classification, Bryan and Morrey classification, and Ring classification. Pre-contoured locking plates (posterolateral and medial) were digitally reconstructed in 3D and virtually applied to the fracture models. The angle of interest was defined as the angle between the longitudinal central axis of each distal locking screw and the primary fracture plane; suitability was defined as an angle within 90° ± 22° (68°–112°). Two associate chief surgeons independently performed fracture reduction, fracture-line tracing, and angle measurements. Each assessment was repeated after a 2-week interval. Inter- and intra-observer reliability were evaluated using the intraclass correlation coefficient (ICC).

resultsFracture lines clustered primarily at three anatomical regions: the distal capitellum, the posterolateral column, and the posterior trochlea. Combined application of the MDCS, AO/OTA, and Ring classification systems provided complementary fracture characterization. Acceptable screw orientation (all distal screws within 90°±22° of the fracture plane) was achieved in 50.0% of posterolateral constructs (12/24) and 66.7% of medial constructs (4/6). At the individual screw level, 56.7% of posterolateral screws (68/120) and 66.7% of medial screws (12/18) met this criterion. Mean screw trajectories were comparable between fixation strategies (77.8°±4.2° vs. 79.1°±3.9°), with no significant between-group difference (P = 0.28). Sensitivity analyses across alternative angular windows (90°±15° and 90°±25°) demonstrated stable suitability rates without reversal of overall trends. Inter- and intra-observer agreement was excellent for fracture-line tracing, virtual reduction, and screw angle measurement (all ICCs > 0.90).

conclusions3D fracture mapping facilitates preoperative planning by visualizing complex fracture morphology. Existing classification systems are complementary but require combination for comprehensive description. Pre-contoured locking plates may have geometric limitations in specific complex morphologies (posterior comminution, small osteochondral fragments), supporting individualized hybrid fixation strategies. The findings provide practical guidance for implant selection and surgical planning in clinical practice.