In vivo and 3-dimensional functional anatomy of the anterior bundle of the medial collateral ligament of the elbow.
BACKGROUND
Although the anterior bundle of the medial collateral ligament (AMCL) is a critical stabilizer of the elbow joint, little information exists on in vivo and 3-dimensional functional anatomy of the AMCL. The purposes of this study were to investigate in vivo changes in the length of the AMCL during elbow flexion and to clarify the 3-dimensional functional anatomy of the AMCL.


METHODS
We created 3-dimensional models of the AMCL and bones from computed tomography data of 4 healthy elbows in 5 different elbow positions. The AMCL was subdivided into 9 ligaments. We calculated changes in lengths of ligaments during flexion and related ligament origins to the axis of rotation of the elbow joint.


RESULTS
There were 4 uniquely configured isometric ligaments, where their origins aligned broadly along the course of the axis of rotation in the coronal plane. The medially originating ligaments inserted on the posterior portion of the tubercle of the coronoid process, whereas the laterally originating ligaments inserted on its anterior portion. There were 5 non-isometric ligaments, 3 of which had origins proximal to the axis and became taut only in extension and the other 2 having origins distal to the axis and becoming taut only in flexion.


CONCLUSIONS
Isometric ligaments within the AMCL do not originate from a narrow area; rather, they originate from a broader area that extends more medially in the coronal plane than previously thought, which explains how the AMCL reconciles isometricity and robustness. The proximal and distal ligaments act as checkreins that work only at the limits of elbow motion.
Department of Orthopedic Surgery, Osaka University Graduate School of Medicine, Osaka, Japan.
Junichi
J
Miyake
Hisao
H
Moritomo
Takashi
T
Masatomi
Toshiyuki
T
Kataoka
Tsuyoshi
T
Murase
Hideki
H
Yoshikawa
Kazuomi
K
Sugamoto
D001696:Biomechanical Phenomena; D017885:Collateral Ligaments / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D003198:Computer Simulation; D004551:Elbow Joint / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D006801:Humans; D021621:Imaging, Three-Dimensional; D008023:Ligaments, Articular / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D008953:Models, Anatomic; D011859:Radiography; D016059:Range of Motion, Articular / Q000502:physiology*; D012680:Sensitivity and Specificity