The nonarticulating portion of the radial head: anatomic and clinical correlations for internal fixation.

The proximal radioulnar joint was dissected in 24 cadaveric elbows to localize the area of the radial head that did not articulate with the lesser sigmoid notch of the ulna. The nonarticulating portion of the radial head was posterolateral in the anatomic position of full supination. Gross observations of the nonarticulating portion of the radial head revealed a thinner band of yellowish cartilage relative to a wider, white, glistening cartilage of the articular portion of the radial head. The nonarticular portion of the radial head did not contain the angled peak, which is most prominent in the middle of the articular portion. The average arc of the nonarticulating radial head was 113 degrees (range, 106 degrees to 120 degrees; standard deviation, 4 degrees). This nonarticulating portion of the radial head (or safe zone for prominent fixation) consistently encompassed a 90 degrees angle localized by palpation of the radial styloid and Lister's tubercle. Using these palpable distal landmarks to localize the safe zone of the radial head, 24 different cadaveric elbows were internally fixed with a plate and screws through 3 different approaches (anterior, lateral, and posterolateral). Regardless of approach, the internal fixation allowed full forearm rotation in all the specimens. Utilization of this method and anatomic landmarks to localize the nonarticular portion of the radial head may assist the surgeon in open reduction and internal fixation of fractures of the radial head and neck.