Objective: The lateral ulnar collateral ligament (LUCL) is considered to be the main factor against posterolateral rotatory instability (PLRI). The aim of this study was to clarify the morphological features of the LUCL and the related osseous landmarks on 3-dimensional (3D) images. We hypothesized that the characteristic features of the LUCL and related structures can be identified, which may assist surgeons in performing LUCL reconstruction with a more anatomic perspective. Materials and Methods: Thirty-five nonpaired, formalin-fixed human cadaveric elbows were evaluated in this study. After the identification of the LUCL, the outlines of the ligament were marked by using soft stainless wires. 3D images were created, and the insertions and running route of the LUCL and related osseous landmarks were analyzed. Results: The LUCL originated from the anterior edge of the prominence at the lateral epicondyle and inserted from the lesser sigmoid notch to the supinator crest with increasing width. In the 3D images, the LUCL formed an anterior curved shape and covered the radial head like a hammock. The insertion of the LUCL at the humerus was nearly at the center of the capitellum, with a width of 2.61 ± 1.02 mm. The insertion of the LUCL at the ulna was located from the lesser sigmoid notch to the supinator crest, with a width of 9.0 ± 2.8 mm. The proximal end of the LUCL insertion at the ulna was 7.0 ± 3.0 mm distal to the articular surface of the radial head. On the horizontal plane, the LUCL was located on the radial head at 99.5° ± 10.3° to 126.1° ± 12.4°. Conclusions: The LUCL insertion at the humerus was nearly at the center of the capitellum, and the LUCL insertion at the ulna was located from the lesser sigmoid notch to the supinator crest. This study showed that both the supinator crest and lesser sigmoid notch could be useful as osseous landmarks. The LUCL was attached to the annular ligament at 8 to 9 o’clock position in the radial head, which stabilizes the radial head. On the basis of these morphological features, the LUCL might act a posterior buttress for the radial head and the ulna to prevent its subluxation, and therefore it is considered to be the principal constraint of the elbow joint against PLRI. The results of this study may assist surgeons in performing LUCL reconstruction with a more anatomic perspective.
