Background: The lateral ulnar collateral ligament,
the entire lateral collateral ligament complex, and the overlying
extensor muscles have all been suggested as key stabilizers against
posterolateral rotatory instability of the elbow. The purpose of
this investigation was to determine whether either an intact radial
collateral ligament alone or an intact lateral ulnar collateral
ligament alone is sufficient to prevent posterolateral rotatory
instability when the annular ligament is intact.
Methods: Sequential sectioning of the radial collateral
and lateral ulnar collateral ligaments was performed in twelve fresh-frozen
cadaveric upper extremities. At each stage of the sectioning protocol,
a pivot shift test was performed with the arm in a vertical position.
Passive elbow flexion was performed with the forearm maintained
in either pronation or supination and the arm in the varus and valgus
gravity-loaded orientations. An electromagnetic tracking device
was used to quantify the internal-external rotation and varus-valgus
angulation of the ulna with respect to the humerus.
Results: Compared with the intact elbow, no differences
in the magnitude of internal-external rotation or maximum varus-valgus
laxity of the ulna were detected with only the radial collateral
or lateral ulnar collateral ligament intact (p > 0.05).
However, once the entire lateral collateral ligament was transected,
significant increases in internal-external rotation (p = 0.0007)
and maximum varus-valgus laxity (p < 0.0001) were measured.
None of the pivot shift tests had a clinically positive result until
the entire lateral collateral ligament was sectioned.
Conclusions: This study suggests that, when the annular ligament
is intact, either the radial collateral ligament or the lateral
ulnar collateral ligament can be transected without inducing posterolateral
rotatory instability of the elbow.
Clinical Relevance: Surgical approaches to the lateral
side of the elbow that violate only the anterior or posterior half
of the lateral collateral ligament should not result in posterolateral rotatory
instability of the elbow. This is important information for surgeons
planning various procedures on the lateral aspect of the elbow,
such as reconstruction of a fractured radial head, radial head replacement,
or total elbow arthroplasty.