Lateral Ulnohumeral Joint Space Widening is Not Diagnostic of Radial Head Arthroplasty Overstuffing

PURPOSE: Metallic radial head replacement with a prosthesis that is too thick has been reported to be associated with stiffness, pain, and capitellar wear. Radiographic widening of the lateral ulnohumeral joint after radial head replacement has been used as a criterion to diagnose overstuffing. The purpose of this study was to show that widening of the lateral ulnohumeral joint is a normal anatomic variant and therefore cannot be used conclusively to diagnose joint overstuffing. METHODS: Fifty normal standardized anteroposterior radiographs from 50 patients were reviewed to evaluate variations in the joint space between the medial and lateral ulnohumeral joints. Measurements were taken on 3 occasions by one surgeon and on a single occasion by a second surgeon. At 4-times magnification, 2 lines were drawn perpendicular to the lateral ulnohumeral joint and 2 lines perpendicular to the medial ulnohumeral joint. Measurements were then compared to evaluate joint space width and parallelism. RESULTS: Intraclass correlation coefficients indicated excellent intrarater and interrater reliability. The width of the lateral ulnohumeral joint space was greater than that of the medial ulnohumeral joint space. The medial joint space was parallel, and the lateral joint space was nonparallel. CONCLUSIONS: The lateral ulnohumeral joint space is often wider than the medial ulnohumeral joint space on anteroposteror radiographs of the normal elbow. Although the medial joint space is usually parallel, the lateral joint space may be nonparallel and wider laterally; therefore, lateral joint space widening is not a reliable indicator of radiocapitellar joint overstuffing. A nonparallel medial ulnohumeral joint space may suggest possible overstuffing of a radial head arthroplasty; however, comparing radiographs of the uninjured elbow is likely the best investigation to consider when overstuffing is suspected.