Anatomic Investigation of Commonly Used Landmarks for Evaluating Rotation During Forearm Fracture Reduction.

BACKGROUND: Evaluating rotation during open reduction and internal fixation of a forearm fracture is of paramount importance. In challenging cases, surgeons may utilize radiographic relationships between proximal and distal radial and ulnar landmarks to assess rotational position. However, to our knowledge, limited anatomic data are available to confirm these relationships. METHODS: Six hundred cadaveric radii and ulnae were obtained. Digital representations of the bicipital tuberosity, the radial styloid, the coronoid process, and the ulnar styloid were acquired, and the rotational profiles between respective landmarks were calculated. In order to validate the results and investigate the ability to differentiate rotated osseous positions, each bone was imaged in increments of 10° of rotation and the profile of each landmark was measured. RESULTS: The radial styloid was at a mean of 158° ± 14° of supination relative to the bicipital tuberosity. The ulnar styloid was at a mean of 185° ± 14° of supination relative to the coronoid process. Imaging of the bones in increments of 10° of rotation supported the relationships above. It was also found that a 1-mm difference in profile size corresponded to up to 60° of rotation for the average ulna, compared with 10° for the average radius. CONCLUSIONS: Our findings suggest that using the bicipital tuberosity and the radial styloid to assess intraoperative rotation of the radius on anteroposterior radiographs may be of limited value; the landmarks were not generally 180° apart. Although the rotational positions of the coronoid process and the ulnar styloid were, on average, closer to 180°, surgeons should be aware of the wide range of normal anatomy as well as the inability to judge rotation by as much as 60°, even for an "ideal" ulna. CLINICAL RELEVANCE: This study, to our knowledge, represents the first anatomic investigation of the rotational profiles between the osseous landmarks used to assess forearm rotation after fracture. We recommend that surgeons first image the bicipital tuberosity at its largest profile, supinate the arm 20°, and confirm that the radial styloid is at its largest profile. The ulna can then be assessed to support the lack of rotational deformity in the forearm.