Objectives: To report a method for radiographic determination of the mechanical axis of the canine pelvic limb and its relationship to the joints and bone axes. To report reference ranges for the relationships between the axes of the pelvic limb and for joint position relative to the pelvic limb axis.
Study design: Cadaveric radiographic anatomic study.
Animals: Pelvic limbs (n=101) from normal midsized to large breed dogs; tibiae (n=105) from dogs with cranial cruciate ligament disease (previous study).
Methods: Extended full-limb radiography was performed and images analyzed to determine: mechanical joint reference angles (femur, tibia), pelvic limb axis, tibiofemoral and metatarsotibial angle, mechanical axis-femur/metatarsus angle, and mechanical axis deviation (MAD) of the stifle/tarsus.
Results: Mean mechanical angles were: lateral proximal femoral (103.7 degrees +/-5.4 degrees ), lateral distal femoral (98.6 degrees +/-2.5 degrees ), medial proximal tibial (92.2 degrees +/-1.8 degrees ), medial distal tibial (95.9 degrees +/-2.2 degrees ), tibiofemoral (9.1 degrees varus +/-2.8 degrees ), metatarsotibial (0.6 degrees valgus +/-2.1 degrees ). Mean mechanical axis-femur and-metatarsus angles were 5.6 degrees (+/-1.7 degrees ) and 2.9 degrees (+/-1.5 degrees ), respectively. Mean MAD of the stifle and tarsus were 3.6% (+/-1.1%) and 1.2% (+/-0.6%), respectively. Tibial angles were not different between dogs with and without cranial cruciate ligament disease.
Conclusions: Mechanical axes of the canine pelvic limb and their relationship to the joints can be determined by full-limb radiography.
Clinical relevance: Techniques and reference ranges may be useful for diagnosis, surgical planning, and postoperative assessment of pelvic limb deformities.