Background: The purpose of this study was to
evaluate the stabilizing effect of radial head replacement in cadaver
elbows with a deficient medial collateral ligament.
Methods: Passive elbow flexion with the forearm
in neutral rotation and in 80Â° of pronation and supination was performed
under valgus and varus loads (1) in intact elbows, (2) after a surgical
approach (lateral epicondylar osteotomy of the distal part of the
humerus), (3) after release of the anterior bundle of the medial
collateral ligament, (4) after release of the anterior bundle of
the medial collateral ligament and resection of the radial head,
and (5) after subsequent replacement of the radial head with each
of three different types of radial head prostheses (a Wright monoblock
titanium implant, a KPS bipolar Vitallium [cobalt-chromium]-polyethylene implant,
and a Judet bipolar Vitallium-polyethylene-Vitallium implant) in
the same cadaver elbow. Total valgus elbow laxity was quantified
with use of an electromagnetic tracking device.
Results: The mean valgus laxity changed significantly
(p < 0.001) as a factor of constraint alteration. The greatest laxity
was observed after release of the medial collateral ligament together
with resection of the radial head (11.1Â° ± 5.6Â°).
Less laxity was seen following release of the medial collateral
ligament alone (6.8Â° ± 3.4Â°), and the least laxity
was seen in the intact state (3.4Â° ± 1.6Â°). Forearm
rotation had a significant effect (p = 0.003) on valgus
laxity throughout the range of flexion. The laxity was always greater in
pronation than it was in neutral rotation or in supination. The
mean valgus laxity values for the elbows with a deficient medial
collateral ligament and an implant were significantly greater than
those for the medial collateral ligament-deficient elbows before
radial head resection (p < 0.05). The implants all performed
similarly except in neutral forearm rotation, in which the elbow
laxity associated with the Judet implant was significantly greater
than that associated with the other two implants.
Conclusions and Clinical Relevance: This study showed
that a bipolar radial head prosthesis can be as effective as a solid
monoblock prosthesis in restoring valgus stability in a medial collateral
ligament-deficient elbow. However, none of the prostheses functioned
as well as the native radial head, suggesting that open reduction
and internal fixation to restore radial head anatomy is preferable
to replacement when possible.