Assessment of CORA-based levelling osteotomy in the feline stifle: an ex vivo limb press study

Cranial cruciate ligament (CCL) rupture is uncommon in cats but may cause persistent stifle instability. Previous ex vivo assessments of tibial plateau levelling osteotomy and tibial tuberosity advancement have failed to restore stability in the feline stifle. This study evaluated whether centre-of-rotation-of-angulation-based levelling osteotomy (CBLO) improves ex vivo stability in a refined feline limb-press model that preserves hip flexion-extension. Ten feline hindlimbs were tested intact, after CCL transection, and after CBLO under 30% bodyweight axial loading. Radiographic measurements included proxy CCL distance, joint angles, tibial plateau angle (TPA), anatomical-mechanical axis (AMA) angle, and gastrocnemius lever-arm characteristics. Muscle forces were recorded using calibrated load cells. CBLO reduced mean TPA from 23.8° (SD 2.2°) to 9.4° (SD 2.5°). AMA angle after CBLO (0.5°, SD 0.9°) did not differ significantly from zero (95% CI -0.1° to 1.1°, P = 0.1). Joint condition significantly affected proxy CCL distance (P < 0.001). Compared to intact limbs, distances increased by 7.1 mm (95% CI 6.0 to 8.2, P < 0.001) after CCL transection and by 6.1 mm (95% CI 4.9 to 7.3, P < 0.001) after CBLO, with no significant difference between CCL-deficient and CBLO limbs (-1.0 mm; 95% CI -2.6 to 0.5, P = 0.3). Joint angles and simulated muscle forces were unaffected by joint condition. Gastrocnemius lever-arm length using the calcaneal tunnel was 86% (SD 2.0%) of the anatomical length. CBLO, as performed in this model, corrected tibial slope but did not restore ex vivo stability of the feline stifle following CCL transection.