Regional load bearing of the feline acetabulum

Objective: To test if the caudal acetabulum of the cat is unloaded at mid-stance as has been asserted. Materials and methods: A kinematic study of five healthy cats was performed to ascertain the mid-stance angle of the hip joint, and the orientation of the pelvis and femur. Femora and pelves from 10 feline cadavers were loaded at physiological load at the mid-stance angle. Impression material placed within the acetabulum was extruded from areas of load bearing. Digital images before and after loading were used to assess whether three areas of the acetabulum, cranial, central and caudal, were fully, partially or non-load bearing. Results: There was a significant difference in load bearing in the three regions (p<0.001, Kruskal-Wallis test), with a significant difference in load bearing between the cranial and central thirds (p<0.001) and the cranial and caudal thirds (p<0.001) but no difference between the central and caudal thirds of the acetabulum (Mann-Whitney-U test). Conclusions: The load bearing areas of the feline acetabula are the caudal and central thirds. Clinical relevance: The caudal acetabulum of the cat is loaded, therefore the recommendations for simple fractures being treated conservatively needs to be reconsidered.