The Role of Femoral Head Size and Femoral Head Coverage in Dogs with and without Hip Dysplasia

SIMPLE SUMMARY: Canine hip dysplasia is a nonhealing developmental orthopedic disorder resulting in osteoarthrosis of the hip joints and lameness. Radiography is an important tool to diagnose, grade and assess prognosis in hip dysplasia. The purpose of this study was to investigate radiographically detectable and measurable parameters that could indicate a predisposition to hip dysplasia. Radiographs of 264 dogs presented for canine hip dysplasia screening were evaluated for femoral head size, coverage of the femoral head by the acetabulum and acetabular length in relation to dysplasia status according to the Fédération Cynologique Internationale. No significant relationship between femoral head area and Fédération Cynologique Internationale assessment was detected. Femoral head area was breed-specific and larger in non-dysplastic dogs, males and German wirehaired pointers. Coverage of the femoral head by the acetabulum was significantly affected by presence of dysplasia and breed. All breeds and both sexes showed strong positive correlations between femoral head area and acetabular length. ABSTRACT: The subject of hip dysplasia in dogs is still current and preoccupies both animal owners and veterinarians. Major factors affecting the development of the disorder are hip laxity and incongruent joints. Many studies on etiology, pathogenesis, and early diagnosis have been performed to reduce prevalence and select healthy dogs for breeding. The purpose of the present study was to investigate a possible relationship between dysplasia and femoral head area (FHA), femoral coverage by the acetabulum (CFH) and cranio-caudal distance of the dorsal acetabular rim (CrCdAR). Radiographs of a total of 264 skeletally mature dogs with similar physical characteristics (German wirehaired pointers (GWP), German shepherd dogs (GSD) and Labrador retrievers (LAB)) presented for routine hip dysplasia screening were recruited for the study. FHA, CFH and CrCdAR were measured and related to dysplasia status. Evaluations of FHA (p = 0.011), CFH (p < 0.001) and CrCdAR length (p = 0.003) measurements revealed significant interactions between breed, sex and FCI scores, so they had to be assessed separately. The results revealed that FHA tends to decrease as the hip dysplasia score worsens. There was no significant relationship between FHA and dysplasia assessment. FHA is breed-specific and is larger in normal and near-normal male (p = 0.001, p = 0.020) and female (p = 0.001, p = 0.013) GWP compared to GSD, respectively. FHA is greater in normal male GWP (p = 0.011) and GSD (p = 0.040) compared to females. There was a significant and strong positive correlation between FHA and CrCdAR in all breeds and sexes. Additionally, FCI scoring had a medium (GWP, GSD) to strong (LAB) negative correlation with CFH.