Osteosintesi poliassiale bloccata: impiego clinico e test meccanici

Abstract

Over the years, osteosynthesis has evolved with a change of emphasis from a mechanical approach to fractures with the objective of mechanical and anatomical reconstruction of the bone to a biological one, in which the approach to the fracture site is mostly useless as the primary objective is represented by skeletal segment alignment. The biological fixation conceived in this way includes the use of plates with angular stability. The mechanical node that is created between the plate and the locking-head screws generates a real internal fixator that does not require, for the stability of the system, a friction between the plate and the bone. In this type of implants the plate acts as a bridging system and the transfer of loads between the fracture fragments is ensured by angular stability.

Stainless steel remains the most commonly used material in veterinary orthopedics. Recently, titanium alloy systems have been introduced for the greater biocompatibility and the lower rate of infection correlated with its use. Several fixed-angle titanium made systems are now available for veterinary use. Each implant is characterized by a different locking system and design that affect its mechanical properties.

In literature, few biomechanical information are available on the new locking implants in general and particularly on the PAX-S plates. To our knowledge no information regarding PAX-R and VetLOX plates’ properties has been published yet. The aim of our study was to evaluate and compare the biomechanical properties of three listed above implants to a single cycle to failure in bending and to report outcomes and complications of dog and cat fractures treated with the PAX system. Qualitative comparison of our results with previously published data suggests that the PAX-S plate seems to have a higher bending stiffness while the bending strength data showed similar trends to the findings of other studies. Our retrospective study included 85 animals. Overall complications occurred in 23 cases and plate failure occurred in 9 cases. Statistically significant factors that affected healing time were age and fracture type. Those associated with complications were implant type and screw number.