In vitro biomechanical analysis of internal fixation with two or three cannulated screws in femoral neck fractures in dogs
Caldeira FMC1, Rahal SC1, Cassanego GR1, Silva JP1, Ribeiro CR2, Serrato SAA3, Melen CE4
1Department of Veterinary Surgery and Animal Reproduction, School of Veterinary Medicine and Animal Science, São Paulo State University (UNESP), Botucatu, Brazil,, Botucatu, Brazil, 2Mechanical and Metallography Testing Laboratory – LEMM, Brazil, Jaú, Brazil, 3University of Tolima, Ibagué, Colombia, 4University of Buenos Aires, Buenos Aires, Argentina.
Objectives:
Cannulated screws are one of the fixation types available for fracture fixation at the femoral neck in human patients, but there is no consensus on the number and optimal configuration of the screws. In dogs, there is a lack of comprehensive studies to assess the relevance of these screws in femoral neck fractures. Therefore, this study aimed to evaluate the in vitro mechanical properties of basilar fractures of the femoral neck stabilized with two or three titanium cannulated screws.
Methods:
Twenty-one femurs from adult crossbred dogs were harvested. The bones were divided into three equal groups: Group 1 – control (no osteotomy), Group 2 – osteotomy and stabilization with two cannulated screws, Group 3 – osteotomy and stabilization with three cannulated screws. All groups were tested with destructive axial compression with load applied to the femoral head. The load to failure, deflection, and stiffness were evaluated.
Results:
The placement of the three cannulated screws was technically more demanding than two cannulated screws because of the risk of cortical perforation, especially in the area of the trochanteric fossa. The smaller the width of the femoral neck, the higher the risk of cortical bone wall perforation. There was a statistically significant difference for load to failure and stiffness among the groups (G1>G3>G2) (p<0.05). The deflection did not show differences among groups.
Conclusions:
In conclusion, in vitro canine femoral neck fractures repaired with three cannulated screws were significantly stronger than two cannulated screws, but the clinical efficacy must be evaluated.