Transitional lumbosacral vertebrae and extra lumbar bones in Labrador

Abstract

OBJECTIVE: Transitional lumbosacral vertebrae (TLSV) is a hereditary malformation of the spinal column diagnosed in various dog breeds. The aim of this study was to explore whether different lumbosacral phenotypes have an inherited basis. METHODS: Radiographs of all dogs within a breeding colony were performed and assessed. A comparison of the incidence of TLSV, eight lumbar vertebrae (8LV), and fusion of the first caudal vertebrae to the sacrum or near fusion of this area was made between litters of normal parentage and litters where one or both of the parents had an anomaly. RESULTS: Of the 119 puppies included in the study, 69 had normal conformation, 9 had 8LV, 9 had TLSV and 32 had fusion of the first caudal vertebra (Ca1) to the caudal sacral segment or a reduced joint space in this area. Results indicated that all the abnormal types likely had common underlying genetic causes. Compared with the population as a whole, significantly more progeny were observed to have abnormalities of the sacral region when both parents were affected by either fusion of Ca1 to the third sacral vertebra (S3) and/or had 8LV. Significantly more progeny were normal compared with the entire study population when both parents were normal. Strong similarity between parental and progeny phenotypes suggested that the characteristics were heritable and likely influenced by major gene effects. CONCLUSION: When performing screening radiographs for TLSV, assessment for 8LV and fusion of Ca1 to S3 should be included.