A Biomechanical Comparison of Locking and Nonlocking Plates for the Fixation of Calcaneal Fractures

Abstract

Locking plate systems have been developed in an attempt to increase the strength of fracture fixation and, in so doing, allow earlier mobilization and rehabilitation. The purpose of our study was to compare the mechanical integrity of the locking plate and traditional nonlocking plate fixation for calcaneal fractures in a cadaver model. Our hypothesis was that the locking plate construct provides stronger fixation than the nonlocking plate construct. We created a Sanders type-IIB fracture in 10 pairs of fresh-frozen cadaver feet (bone mineral density, 0.50 +/- 0.14 g/cm2 age, 69 +/- 16 years). One foot of each pair was fixed with a nonlocking calcaneal plate (Synthes, Paoli, PA), and the contralateral foot was fixed with the Locking Calcaneal Plate (Synthes, Paoli, PA). The specimens then were cyclically loaded through the tibia from 0 to 700 N at 1 Hz on a materials testing machine to simulate weightbearing. Fragment displacement was measured with a three-dimensional kinematic analysis system. Significance was set at p < 0.05. There was no significant difference between the two plating systems with respect to the mean (+/- SD) number of cycles to failure (locking plate, 3261 +/- 2355; nonlocking plate, 2271 +/- 2465). In a cadaver model of type-IIB calcaneal fractures, locking plate fixation did not provide a biomechanical advantage over traditional nonlocking plate fixation.