The association between gonadectomy and timing of gonadectomy, and the risk of canine cranial cruciate ligament disease: A systematic review and meta-analysis.

Objective: To determine if gonadectomy in dogs is associated with the risk of cranial cruciate ligament disease (CrCLD) and to quantify the magnitude of the association.

Study design: Systematic review and meta-analysis.

Sample population: Comparative studies with gonadectomized and entire dogs, with CrCLD as an outcome measure.

Methods: A systematic search of the primary and gray literature was performed. The effect size of the outcome measure was defined as the OR and 95% CI. Subgroup analysis was performed with sex, breed, and age at gonadectomy. A pooled OR (95% CI) was generated from meta-analysis of relevant studies. Certainty in the body of evidence was rated with the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework.

Results: The literature search yielded 1398 results and 24 relevant studies were included for synthesis. Gonadectomized female (pooled OR = 2.293, 95% CI = 1.768-2.945) and male (pooled OR = 2.117, 95% CI = 1.665-2.691) dogs were both at increased odds of developing CrCLD in comparison with entire female and male dogs, respectively. Subgroup analysis showed that gonadectomy at 1 year or less was consistently associated with an increase in odds of developing CrCLD in both sexes. Overall certainty in the evidence was rated as moderate. All included studies were observational and no controlled trials were available.

Conclusion: In data with moderate certainty, gonadectomy is associated with increased odds of developing CrCLD in both sexes, particularly in dogs gonadectomized at 1 year of age or less.

Clinical significance: This study provides an estimate of the true effect size of gonadectomy on the odds of developing CrCLD, which may be useful for clinical decision making surrounding gonadectomy and the timing of gonadectomy.