Measurement of Femoral and Tibial Joint Reference Angles and Pelvic Limb Alignment in Cats

Objective To report pelvic limb joint reference angles, limb alignment, and mechanical axis deviation for the feline pelvic limb. Study Design Cadaveric radiographic anatomic study. Animals Skeletally mature, mixed breed cats (n = 50). Methods Extended pelvic limb radiography was performed and images analyzed to determine femoral anatomic joint reference angles, femoral and tibial mechanical joint reference angles, tibiofemoral angle, metatarsotibial angle, mechanical axis-femur and mechanical axis-metatarsus angles, and mechanical axis deviation of the stifle and tarsus. Mean +/- SD and 95% confidence intervals (95% CI) were calculated. Results Mean +/- SD angles and 95% CI were: anatomic lateral proximal femoral (103.9 degrees +/- 3.8 degrees; 103.1 degrees - 104.6 degrees), anatomic lateral distal femoral (93.8 degrees +/- 2.5 degrees; 93.3 degrees - 94.3 degrees), mechanical lateral proximal femoral (100.5 degrees +/- 3.7 degrees; 99.8 degrees - 101.2 degrees), mechanical lateral distal femoral (97.2 degrees +/- 2.2 degrees; 96.7 degrees - 97.6 degrees), mechanical medial proximal tibial (88.0 degrees +/- 3.2 degrees; 87.3 degrees - 88.6 degrees), mechanical medial distal tibial (107.6 degrees +/- 4.8 degrees; 106.6 degrees - 108.5 degrees), mechanical tibiofemoral (7.4 degrees varus +/- 2.5 degrees; 6.9 degrees - 7.9 degrees), mechanical metatarsotibial (6.0 degrees valgus +/- 3.5 degrees; 5.3 degrees - 6.7 degrees); mechanical axis-femur (3.2 degrees +/- 1.4 degrees; 2.9 degrees - 3.5 degrees) and mechanical axis-metatarsus (2.4 degrees +/- 2.0 degrees; 1.7 degrees - 2.1 degrees). Mechanical axis deviation of the stifle and of the tarsus were 2.0% +/- 0.9% (95% CI: 1.92.2) and 0.8% +/- 1.0% (95% CI: 0.71.0), respectively. Conclusions Mean pelvic limb joint reference and limb alignment angles can be used for diagnosing angular limb deformities of the feline pelvic limb and for planning corrective osteotomies in affected cats.