Charlotte B. Pfund, Kirk L. Wendelburg

Background

Periprosthetic femoral fissures and fractures are recognized complications of cementless total hip replacement (THR) in dogs, with reported intraoperative and postoperative incidences up to 1.5% and 3.6–13.1%, respectively. Existing risk factors include age, low canal flare index, intraoperative fissures, and osteopathy, but femoral cortical thickness has never been quantified as a formal risk factor in dogs despite evidence in human orthopedics linking cortical thinning to fracture risk. This study aimed to establish a standardized femoral cortical thickness index (CTI) for dogs undergoing THR, assess its reproducibility, and evaluate the relationship between CTI and perioperative fracture or fissure risk.

Methods

This retrospective study evaluated 224 dogs that underwent cementless THR using BFX lateral bolt femoral stems between 2013 and 2023. Preoperative mediolateral femoral radiographs were used to measure cortical and diaphyseal diameters at three standardized locations: immediately distal to the lesser trochanter, one-quarter down the femur, and halfway down the femur. CTI was calculated as the mean ratio of cortical thickness to diaphyseal diameter at the three sites. Interobserver reproducibility was assessed in a subset of 10 dogs measured by six observers, and pre- vs. postoperative values were compared. Associations between CTI and intraoperative, postoperative, or overall fissure/fracture risk were analyzed using logistic regression.

Results

CTI measurements were highly reproducible, with interobserver ICC of 0.984 and pre- vs. postoperative ICC of 0.96. The mean CTI for all dogs was 0.285. Dogs that developed perioperative fissures or fractures had significantly lower CTI values (mean 0.246) compared with unaffected dogs (mean 0.293). A total of 22 dogs (9.8%) sustained intraoperative fissures or fractures, and 18 dogs (8%) developed postoperative fissures or fractures. CTI was the only significant predictor of intraoperative, postoperative, and overall fracture/fissure risk, with each 0.001 increase in CTI reducing odds of complications by 2–3%. No significant associations were found with breed, age, bodyweight, body condition score, sex/neuter status, hip dysplasia type, or proximal femoral sclerosis.

Limitations

Limitations include the retrospective design and reliance on a single implant system and two surgeons, which may limit generalizability. Some radiographs had variable visualization of anatomic landmarks (e.g., lesser trochanter), potentially affecting measurement precision. The study did not evaluate CTI across other THR systems or correlate CTI directly with bone mineral density. Additionally, the relatively small number of dogs with non-ideal body condition scores may have limited detection of associations with BCS.

Conclusions

CTI is a highly reproducible radiographic measurement and a significant predictor of perioperative femoral fracture and fissure risk in dogs undergoing cementless THR. Lower CTI values correlated strongly with complication risk, suggesting CTI should be incorporated into preoperative planning, particularly in dogs with additional risk factors. These findings parallel human data linking cortical thickness with bone fragility and support future multicenter studies to validate CTI across surgical teams and implant systems.

Disclaimer: The summary generated in this email was created by an AI large language model. Therefore errors may occur. Reading the article is the best way to understand the scholarly work. The figure presented here remains the property of the publisher or author and subject to the applicable copyright agreement. It is reproduced here as an educational work. If you have any questions or concerns about the work presented here, reply to this email.