Morphometry of the radiocapitellar joint: is humeral condyle diameter a reliable predictor of the size of the radial head prosthesis?

Background And Hypothesis: Radial head arthroplasty (RHA) is a reliable procedure to manage complex injuries of the elbow, but complications due to inadequate sizing have been observed. Radiocapitellar morphometry has been studied widely, but RHA preoperative planning is not yet well defined. We hypothesized that specific morphologic parameters of the radiocapitellar joint measured with simple clinical software for radiographic analysis could be useful tools for clinical practice to predict RHA size preoperatively.

Methods: Radiologic radiocapitellar joint dimensions (humeral condyle diameter [HCDi], radial head diameter [RHDi], and radial head height) were analyzed on true anteroposterior and lateral radiographs, using commercial picture archiving and communication system software, in 43 patients with non-osseous pathology of the elbow and 24 patients with RHA. Interobserver concordance was studied, and a regression model to relate different parameters was developed.

Results: Interobserver concordance was greater than 0.8 for HCDi and RHDi on the lateral view and RHDi on the anteroposterior view for the general population. The parameter with the best correlation with the radial head arthroplasty diameter (RHADi) size was HCDi on the lateral view. A regression model was calculated and defined as follows: RHADi = 6.99 + 0.733 × HCDi on lateral view. This model allows prediction of RHADi in 67% of cases.

Conclusion: Radiologic radiocapitellar parameters show good interobserver reliability. RHADi can be calculated preoperatively from HCDi on the lateral view in 67% of cases.