Evaluation of the Proximal Radio-Ulnar Joint Anatomy as a Marker for Radial Head Arthroplasty

Objectives Implant sizing is a challenging step in radial head arthroplasty. Improper selection can “overstuff” the elbow joint and lead to degenerative changes. Prior investigation with computed tomography demonstrated a consistent relationship between the radial head and coronoid, which can guide implant sizing. We hypothesize that conventional radiography can similarly define the radioulnar variance at the proximal radioulnar joint (PRUJ) and serve as a landmark for radial head replacement. Methods Patients with elbow radiographs were eligible for the study. Patients who had trauma from the humeral shaft to the distal radius were excluded. Anteroposterior projections were performed in full extension and supination. One orthopaedic hand specialist, one senior resident, and one junior resident assessed the radiographs for coronoid to radial head height, defined as the distance from the equator of the radial head projection to the top of the coronoid projection. Results Fifty elbow radiographs were consecutively selected for radiographic study. There were 37 (74%) males and 13 (26%) females, with a mean age of 40. The average coronoid-radial head distance was 2.2mm (SD 1.5mm), ranging from -2.6 to 5.2mm. Interobserver reliability was 0.95. Conclusions Our data shows that the radiographic anatomy of the PRUJ shows a consistent relationship between the coronoid and radial head. This measurement is reliably reproducible and may be used as a marker of radial head placement and sizing in radial head arthroplasty, reducing cost and radiation exposure. This study presents an alternative reference point to measure radial head variance to assess for overstuffing during radial head arthroplasty.