Skeletal morphology and morphometry of the lumbosacral junction in German shepherd dogs and an evaluation of the possible genetic basis for radiographic findings.

The aim of this study was to identify skeletal variations in the lumbosacral junction (LSJ) of the German shepherd dog (GSD) compared with other large breeds. The radiographic traits of the LSJ were investigated in a group of 733 GSDs and a control group of 334 dogs of other breeds that were matched in terms of size. Nine morphological and 17 morphometric traits were recorded and analysed. Furthermore, the possibility of a genetic basis for these radiographic features was evaluated by calculation of genetic variance components. Five of the morphological and 14 of the morphometric traits varied significantly between the GSD group and the control group (P<0.05). Osteochondrosis of the sacral endplate (SOC) had a higher prevalence in the GSDs (10.1%) compared with controls (5.7%). The majority of LSJ degenerative changes recorded from the radiographs occurred in the GSDs. The extent and relative proportion of lumbosacral step formations were greater in the GSD group compared with controls (P<0.001). The lumbosacral vertebral canal height was reduced in the GSD compared with the control dogs (P<0.001) suggesting a primary stenosis. This was accentuated by an abrupt tapering of the vertebral canal at the level of the LSJ indicated by a lumbosacral ratio of 1.51 in the GSD. The skeletal morphology and morphometry of the LSJ in the GSD seem to be different from that found in other large dogs. For multiple traits frequently observed in GSD such as SOC, step formations, and LSJ stenosis, moderate to high non-zero heritabilities were noted. As these features are also assumed to promote lumbosacral disease, selection against these traits is suggested.