Abnormal modified Insall-Salvati index values are associated with increased odds of medial meniscal tears in dogs with cranial cruciate ligament tears.

OBJECTIVE: To evaluate the association between patellar height, as measured by the modified Insall-Salvati (IS) index, and medial meniscal tear in dogs with cranial cruciate ligament tears (CCLTs). METHODS: Medical records from dogs treated for CCLT were reviewed. Preoperative patellar height was measured on mediolateral radiographs with the use of the modified IS index. Craniomedial stifle mini-arthrotomy documented the presence or absence of medial meniscal tears. Statistical analysis, adjusted to control for confounding variables, assessed whether abnormal IS index values were associated with meniscal injury. RESULTS: The study included 229 stifles. Abnormal modified IS index values were found in 12.6% (29 of 229) of stifles, of which 44.8% (13 of 29) had a concurrent medial meniscal tear. Among the dogs with a normal modified IS index (87.4% [200 of 229]), only 24.5% (49 of 200) had a concurrent medial meniscal tear. Dogs with an abnormal IS index had 3 times the odds of a medial meniscal tear (95% CI, 1.2 to 7.3) compared to those with a normal index. There was no statistically significant difference in the distribution between complete and partial CCLT between the normal IS index and abnormal IS index groups. CONCLUSIONS: Abnormal patellar height, as measured by the modified IS index, is significantly associated with increased risk of secondary medial meniscal tear in dogs with CCLT. CLINICAL RELEVANCE: Preoperative measurement of the modified IS index may help identify dogs at increased risk for meniscal tearing, supporting surgical planning and client communication.