Articular varus angles of the elbow are not associated with coronoid fracture type

The articular surface angle of the elbow (ie, valgus/varus alignment) could affect how traumatic forces are distributed through the ulnohumeral joint, potentially influencing coronoid fracture types. This study hypothesizes that an angle toward varus would be associated with coronoid fractures involving the anteromedial facet (O'Driscoll type 2), rather than fractures limited to the anterolateral tip (O'Driscoll type 1). This study aims to explore the potential association between radiologic elbow varus angles and O'Driscoll coronoid fracture types.

This retrospective study was conducted at an urban Level 1 trauma center. Adult patients with anterolateral tip or anteromedial coronoid fractures and an elbow computed tomography (CT) scan within four weeks of injury were identified from February 2014 to July 2023, resulting in 142 patients. The mean age was 48 ± 18 years, and 52% of patients were male (74 of 142). Each coronoid fracture was classified independently according to the O'Driscoll classification by 2 trained observers using radiographs, two-dimensional and three-dimensional CT scans with humeral subtractions, and intraoperative findings. Of the patients, 48% (68 of 142) presented with type 1 anterolateral tip fractures, and 52% (74 of 142) with type 2 anteromedial fractures. Interrater reliability of fracture classification was excellent (kappa = 0.90, 95% confidence interval [CI]: 0.83-0.97). Three elbow varus angles were assessed in this study: Trochlear Articular Surface Angle (TASA), Proximal Ulna Articular Surface Angle (PUASA), and Proximal Ulnar Varus Angle (PUVA). Each angle was measured independently by 2 observers using coronal CT scans. Inter-rater reliability was excellent for TASA (intraclass correlation coefficient [ICC] = 0.95, 95% CI: 0.91-0.97), good for PUASA (ICC = 0.89, 95% CI: 0.79-0.91), and moderate for PUVA (ICC = 0.69, 95% CI: 0.56-0.79). Multivariate logistic regression was performed to evaluate the independent association between each varus angle and fracture type, controlling for age, body mass index, gender, hand dominance, and radial head involvement.

The multivariate logistic regression analysis showed no association between the O'Driscoll coronoid fracture types and the TASA (odds ratio [OR]: 0.99; P = .79)', PUASA (OR: 0.99; P = .75), or PUVA (OR: 0.99; P = .86).

Occurrence of anteromedial facet fractures is not found to be associated with varus alignment of the elbow in this study. Factors besides the injury mechanism causing translational fractures in the coronoid fracture spectrum should be further explored in future studies to increase our understanding of the etiopathogenesis of the various coronoid fracture types.