Three-dimensional computed tomography analysis to assess the need for segmental femoral osteotomy in small-breed dogs with medial patellar luxation.

Objective: To evaluate the quadriceps muscle length-to-femoral length ratio (QML:FL) as a predictor of segmental femoral osteotomy (SFO) necessity in small-breed dogs with medial patellar luxation.

Methods: This retrospective study included 53 small-breed dogs (78 limbs) with medial patellar luxation. Medical records from 2008 to 2021 of dogs undergoing patellofemoral joint reconstruction were reviewed. Signalment, surgical records, and CT data were retrospectively analyzed. Patients were classified into 2 groups based on SFO performance: the group requiring SFO (SFO group) and the group where SFO was unnecessary (NSFO group). Regression analysis compared signalment and CT parameters between groups; statistically significant variables were incorporated into a multiple logistic regression analysis to assess factors correlated with SFO. Receiver operating characteristic curves were generated to determine QML:FL cutoff values for predicting SFO.

Results: The SFO group included 26 limbs, while the NSFO group included 52 limbs. Compared to the NSFO group, the SFO group had significantly younger age, lower body weight, higher anatomical distal lateral femoral angle, and lower QML:FL. The QML:FL ratio was the only variable significantly associated with SFO (OR, 0.595; 95% CI, 0.445 to 0.797). The receiver operating characteristic curve identified 0.84 as the optimal cutoff value (sensitivity, 0.83; specificity, 0.96), with an area under the curve of 0.9571.

Conclusions: QML:FL was a reliable preoperative indicator for SFO necessity in medial patellar luxation-affected small-breed dogs. This noninvasive measure enhanced surgical planning.

Clinical relevance: QML:FL allowed objective assessment of SFO necessity, improving individualized treatment strategies for femoral patellar joint reconstruction.