Articular Surface Area of the Coronoid Process and Radial Head in Elbow Extension: Surface Ratio in Cadavers and a Computed Tomography Study In Vivo

Purpose: To quantify the articular surface area ratio of the radial head to the coronoid process to gain a better understanding of the stress distribution across these articulations and possibly to explain the patterns of osteoarthritis that are commonly seen in the elbow. Methods: Thirty cadaveric elbows were harvested and dissected to allow measurement of the radial head and coronoid process articular surfaces. The articular surface areas were measured using the Image J program (National Institutes of Health, Chicago, IL). Twelve men were recruited for this study, and all received a computed tomography (CT) scan of the elbow. A 3-dimensional image of the proximal radioulnar articular surface was created using volume rendering. All specimens were measured 3 times by 2 observers. Results: In the cadaveric measurements, the mean area of the radial head articular fossa was 247.3 ± 52.6 mm 2 (mean ± SD). The mean area of the medial facet of the coronoid process was 232.29 ± 36.5 mm 2, and the mean area of the lateral facet was 141.9 ± 33.3 mm 2. The articular surface area ratio of radial head to coronoid process was 1:1.5. In the CT measurement, the mean area of the radial head articular fossa was 258.9 ± 26.3 mm 2. The mean area of the coronoid process articular surface was 376.9 ± 37.0 mm 2. The articular surface area ratio of radial head to coronoid process was 1:1.46. Conclusions: The ratio of articular surface area of radial head to coronoid process is 1:1.51 in cadavers and 1:1.46 using a CT in vivo, which is the reverse of the reported force transmission ratio across the elbow joint. © 2010.