On biomechanical properties of the sacroiliac joint in purebred dogs

Relative to the Yorkshire Terriers and Maltese dogs the mean expected sacroiliac joint load was calculated to be 1.4-1.6 times higher in other small breeds and 1.7-2.7 times higher in large breeds. The statistically significantly different (p < 0.01, p < 0.001) and mechanically less efficient inclination angles of the wings of the sacrum in adult large breeds (especially German Shepherd Dogs) suggest even higher forces acting on their sacroiliac ligaments. Unlike the case in small breeds, the sacral auricular surface was concave in large dogs to improve interlocking between sacrum and ilium and to reduce craniocaudal translation. An additional ossification center forming the ventral aspect of the transverse process of the second sacral vertebra was present in large breeds, occasionally in midsized and small, but never in toy breeds. This and the relationship between age and inclination angles of the wings of the sacrum in juvenile specimens indicate an affection of the three-dimensional modeling of the wings of the sacrum by formative stimuli such as body weight and locomotion.