Background: Many reports have discussed reconstruction of the
lateral ulnar collateral ligament for the treatment of posterolateral rotatory
instability of the elbow, but information regarding the isometric point of the
lateral ligament of the elbow is limited. The purposes of the present study
were to investigate the in vivo and three-dimensional length changes of the
lateral ulnar collateral ligament and the radial collateral ligament during
elbow flexion in order to clarify the role of these ligaments as well as to
identify the isometric point for the reconstructed lateral ulnar collateral
ligament on the humerus where the grafted tendon should be anchored.
Methods: We studied in vivo and three-dimensional kinematics of the
normal elbow joint with use of a markerless bone-registration technique.
Magnetic resonance images of the right elbows of seven healthy volunteers were
acquired in six positions between 0° and 135° of flexion. We created
three-dimensional models of the elbow bones, the lateral ulnar collateral
ligament, and the radial collateral ligament. The ligament models were based
on the shortest calculated paths between each origin and insertion in
three-dimensional space with the bone as obstacles. We calculated two types of
three-dimensional distances for the ligament paths with each flexion position:
(1) between the center of the capitellum and the distal insertions of the
ligaments (to investigate the physiological change in ligament length) and (2)
between eight different humeral origins and the one typical insertion of the
lateral ulnar collateral ligament (to identify the isometric point of the
reconstructed lateral ulnar collateral ligament).
Results: The three-dimensional distancefor the lateral ulnar
collateral ligament was found to increase during elbow flexion, whereas that
for the radial collateral ligament changed little. The path of the lateral
ulnar collateral ligament gradually developed a detour because of the osseous
protrusion of the lateral condyle with flexion. The most isometric point for
the reconstructed lateral ulnar collateral ligament was calculated to be at a
point 2 mm proximal to the center of the capitellum.
Conclusions: The radial collateral ligament is essentially
isometric, but the lateral ulnar collateral ligament is not. The lateral ulnar
collateral ligament is loose in elbow extension and becomes tight with elbow
Clinical Relevance: The present study suggests that the isometric
point for the lateral ulnar collateral ligament graft origin is approximately
2 mm proximal to the center of the capitellum.