A biomechanical comparison of unilateral and bilateral String-of-Pearls™ locking plates in a canine distal humeral metaphyseal gap model.
OBJECTIVE
To compare the in vitro biomechanical performance of two String-of-Pearls (SOP) plate constructs in a canine distal humeral metaphyseal gap model.


METHODS
Seven pairs of canine cadaveric humeri, including the elbow joints, were prepared. One group consisted of a unilateral medially placed SOP plate with bicortical screws (UNI). The second group consisted of bilateral caudo-medial and caudo-lateral SOP plates applied with monocortical screws (BI). A 2 cm ostectomy was performed immediately proximal to the supratrochlear foramen. Constructs were tested in torsion and axial compression.


RESULTS
The UNI constructs had significantly lower stiffness in torsion and axial compression than the BI group. However, UNI constructs had a significantly higher ultimate strength than BI constructs. All UNI constructs failed by bending of the transcondylar screw and SOP plate. All BI constructs failed by axial pullout of the distal most screws.


CONCLUSIONS
In stabilizing canine supracondylar humeral fractures as modeled here, both the UNI model and the BI model demonstrated biomechanical advantages. The incorporation of a transcondylar screw through the medial plate appears to be beneficial to construct strength.
Richard J. Hurt, Mississippi State University, College of Veterinary Medicine, Department of Clinical Sciences, 240 Wise Center Dr., Mississippi State, MS, 39762, United States, Phone: +1 662 325 3432, Fax: +1 662 325 4011, E-mail: rhurt@cvm.msstate.edu.
R J
RJ
Hurt
J A
JA
Syrcle
S
S
Elder
R
R
McLaughlin
D000818:Animals; D001696:Biomechanical Phenomena; D001860:Bone Plates / Q000662:veterinary*; D002102:Cadaver; D004285:Dogs; D005552:Forelimb; D008422:Materials Testing / Q000662:veterinary*
SOP; String-of-Pearls plate; Supracondylar humeral fracture; humerus; mechanical testing