Femoral cortical thickness index in a population of dogs undergoing total hip replacement

To establish a femoral cortical thickness index (CTI) for dogs undergoing total hip replacement (THR), determine the reproducibility of the established CTI measurements, and assess the efficacy of CTI as a preoperative variable in the femoral fracture/fissure occurrence in dogs undergoing THR.

Retrospective study.

A total of 224 dogs with THR.

Medical records for dogs undergoing THR were reviewed retrospectively, analyzing only the first side in dogs with bilateral THR. Three measuring points were defined on preoperative mediolateral radiographs: immediately distal to the lesser trochanter, one-quarter-, and midway down the femur. The CTI was calculated from the mean cortical and femoral diaphyseal diameters at the established locations. A total of 10 dogs with varying CTI scores were selected for interobserver comparisons and pre-/ postoperative analyses. The relationship between CTI and perioperative fissure/fracture risk was then evaluated.

Interobserver and pre-/ postoperative measurement comparisons showed near-perfect correlation. Analysis of 224 dogs revealed a significant association between lower CTI and incidence of perioperative fractures (p < .0001). The mean CTI for all dogs was 0.285, while it was statistically lower at 0.246 for dogs that sustained fissures/fractures. No other statistically significant risk factors were identified.

This study quantitatively assessed femoral cortical thickness in dogs undergoing THR. The findings confirmed that lower CTI is a repeatable and accurate predisposing factor for perioperative fissure/fracture risk in canine THR.

Factoring CTI into the clinical decision making may minimize fracture risk, especially in dogs with other possible risk factors such as abnormal BCS.