An in vitro biomechanical comparison of dynamic condylar screw plate combined with a dorsal plate and double plate fixation of distal diaphyseal radial osteotomies in adult horses.

OBJECTIVE

To compare stiffness and strength of a dynamic condylar screw plate combined with dorsal broad dynamic compression plate (DCS-bDCP) fixation with double broad dynamic compression plate (dbDCP) fixation used to repair oblique distal fractures of adult equine radii.

STUDY

DESIGN

Experimental.

SAMPLE POPULATION: Adult equine radii (n=10 pair).

METHODS

An unconstrained three-dimensional loading-measurement system was used to determine stiffness of a 50 mm long intact, and then DCS-bDCP or dbDCP-plated osteotomized/ostectomized segment of radii when subjected to a nondestructive sequence of compression, torsion, and lateral-to-medial (LM), medial-to-lateral (ML), cranial-to-caudal (CrCa), and caudal-to-cranial (CaCr) bending. Uniform load over the entire length of construct identified its weakest characteristics during torsion and LM and CrCa bending to failure.

RESULTS

No difference was observed between osteotomized/ostectomized DCS-bDCP and dbDCP construct stiffness for all 6 loading modes, and strength for all 3 failure loads. Ostectomized DCS-bDCP and dbDCP construct stiffness was significantly lower than osteotomized radii, the latter approaching intact for axial, LM, and CrCa bending. Most frequent failure was bone fracture through exit site of a screw located adjacent to osteotomy/ostectomy.

CONCLUSIONS

DCS-DCP and dbDCP constructs had comparable strength and stiffness when repairing osteotomies/ostectomies in equine adult radius bone. Fracture reduction increased stiffness that approached intact bone for loads that placed the unplated side in compression.

CLINICAL RELEVANCE: DCS-bDCP and dbDCP constructs are comparable in stiffness and strength when applied to oblique distal diaphyseal osteotomies/ostectomies in equine radius bone. However, the DCS's localized effect on distal epiphyseal structure because of additional bone removal remains to be investigated under in vivo articular loading conditions.