A biomechanical comparison of double-plate and Y-plate fixation for comminuted equine second phalangeal fractures

Objectives-To compare the biomechanical properties, in full limb preparatio ns, of intact second phalanx and a simulated comminuted second phalangeal f racture stabilized with either two bone plates or a custom Y-plate. Study Design-In vitro biomechanical assessment of intact limbs and of paire d limbs with a simulated second phalangeal fracture stabilized by one of tw o fixation methods. Animal Population-Thirteen pairs of equine cadaveric forelimbs. Methods-A comminuted second phalangeal fracture was created in six paired c adaveric limbs. For each limb pair, the fracture was stabilized with two pl ates in one limb, and with a Y-plate in the contralateral limb. These limbs and seven pairs of intact limbs were subjected to axial compression in a s ingle cycle until failure. Mechanical properties were compared with a mixed -model ANOVA and post hoc contrasts. Joint contact pressure, screw insertio n torque, and final screw torque remaining after mechanical testing were al so evaluated for constructs. Results-No significant differences in mechanical testing variables were det ected between construct types. However, the Y-Plate construct had significa ntly greater yield load, yield displacement and yield energy, and failure l oad and stiffness values than those for intact specimens, whereas the doubl e-plate construct only had greater stiffness than intact specimens. There w ere no significant differences in joint contact pressures for both construc ts. The final screw torque for proximal phalangeal screws was significantly greater for the Y-plate constructs than for double-plate constructs. Conclusions-The Y-plate was as effective as the double-plate technique for stabilization of simulated comminuted second phalangeal fractures in monoto nically tested equine cadaveric forelimbs. Clinical Relevance-This investigation supports evaluation of the Y-plate fo r repair of comminuted second phalangeal fractures in equine patients. Its specific design may facilitate repair of second phalangeal fractures, and m ay provide increased stability by allowing the proximal fragments of the se cond phalanx to be fixed with three screws placed through the plate. (C) Co pyright 2000 by The American College of Veterinary Surgeons.