Lateral radial head offset can be associated with chronic epicondylopathia humeri radialis: A new radiological parameter

This study aimed to compare anatomical parameters on magnetic resonance imaging (MRI) scans between patients with symptomatic isolated chronic epicondylopathia humeri radialis (cER) and healthy controls. It was hypothesized that the radial head would show an increased lateral offset in patients with cER. This retrospective radiological case-control study included patients with cER (symptomatic&#x2009;>&#x2009;6 months) from November 2020 to July 2023. The MRIs of all included patients were compared to those of healthy controls. Radiological measurements were performed in millimetres (mm): lateral humeral epicondyle prominence, radial head diameter, lateral radial head offset, lateral radial head offset ratio (lateral radial head offset/radial head diameter; %) and posterior radial head translation. Retrospective radiological case-control study. Seventy-seven elbows (37 cER/40 healthy controls) from 57 patients (37 male; age: 39.3&#x2009;&#xb1;&#x2009;11.2 years; body mass index: 23.0&#x2009;&#xb1;&#x2009;7.6) were included. There was no significant difference between groups in lateral humeral epicondyle prominence (11.7&#x2009;&#xb1;&#x2009;8.8&#x2009;mm vs. 11.0&#x2009;&#xb1;&#x2009;1.6&#x2009;mm, p&#x2009;=&#x2009;0.051) or radial head diameter (22.2&#x2009;&#xb1;&#x2009;4.1&#x2009;mm vs. 22.2&#x2009;&#xb1;&#x2009;3.7&#x2009;mm, p&#x2009;=&#x2009;0.779). Lateral radial head offset was significantly greater in the cER group compared with healthy controls (mean difference: 1.84&#x2009;mm, 95% confidence interval [CI]&#x2009;=&#x2009;1.07-2.60; p&#x2009;<&#x2009;0.001), while the lateral radial head offset ratio did not differ significantly (21.1% vs. 9.1%, p&#x2009;=&#x2009;0.691). Posterior radial head translation was also significantly increased in the cER group (mean difference: 4.35&#x2009;mm, 95% CI&#x2009;=&#x2009;3.72-4.98; p&#x2009;<&#x2009;0.001). There was no significant difference in ulnohumeral incongruence between groups (2.2&#x2009;&#xb1;&#x2009;0.6&#x2009;mm vs. 2.4&#x2009;&#xb1;&#x2009;0.6&#x2009;mm, p&#x2009;=&#x2009;0.238). Patients with cER showed significantly higher lateral radial head offset and posterior radial head translation on MRI compared to healthy controls. This may suggest that the dynamic stabilizers are weakened in cER patients, resulting in a relative shift of the radial head towards the lateral and posterior position. Level III.