Computer-Assisted Radiographic Calculation of Spinal Curvature in Brachycephalic “Screw-Tailed” Dog Breeds with Congenital Thoracic Vertebral Malformations: Reliability and Clinical Evaluation

et al. (2014) Computer-Assisted Radiographic Calculation of Spinal Curvature in Brachycephalic ''Screw-Tailed'' Dog Breeds with Congenital Thoracic Vertebral Malformations: Reliability and Clinical Evaluation. PLoS ONE 9(9): e106957. doi:10.1371/journal. pone.0106957 Computer-Assisted Radiographic Calculation of Spinal Curvature in Brachycephalic ''Screw-Tailed'' Dog Breeds with Congenital Thoracic Vertebral Malformations: Reliability and Clinical Evaluation Julien Guevar 0 Jacques Penderis 0 Kiterie Faller 0 Carmen Yeamans 0 Catherine Stalin 0 Rodrigo Gutierrez- 0 Claire Wade, University of Sydney, Australia 0 School of Veterinary Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow , Glasgow , United Kingdom The objectives of this study were: To investigate computer-assisted digital radiographic measurement of Cobb angles in dogs with congenital thoracic vertebral malformations, to determine its intra- and inter-observer reliability and its association with the presence of neurological deficits. Medical records were reviewed (2009-2013) to identify brachycephalic screw-tailed dog breeds with radiographic studies of the thoracic vertebral column and with at least one vertebral malformation present. Twenty-eight dogs were included in the study. The end vertebrae were defined as the cranial end plate of the vertebra cranial to the malformed vertebra and the caudal end plate of the vertebra caudal to the malformed vertebra. Three observers performed the measurements twice. Intraclass correlation coefficients were used to calculate the intra- and inter-observer reliabilities. The intraclass correlation coefficient was excellent for all intra- and interobserver measurements using this method. There was a significant difference in the kyphotic Cobb angle between dogs with and without associated neurological deficits. The majority of dogs with neurological deficits had a kyphotic Cobb angle higher than 35u. No significant difference in the scoliotic Cobb angle was observed. We concluded that the computer assisted digital radiographic measurement of the Cobb angle for kyphosis and scoliosis is a valid, reproducible and reliable method to quantify the degree of spinal curvature in brachycephalic screw-tailed dog breeds with congenital thoracic vertebral malformations. - Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the paper and its Supporting Information files. Funding: The authors have no support or funding to report. Competing Interests: The authors have declared that no competing interests exist. Congenital vertebral malformations causing secondary kyphosis (dorsal curvature of the vertebral column) and scoliosis (lateral curvature of the vertebral column) are relatively common in dogs, especially in the brachycephalic screw-tailed breeds such as the English bulldog, French bulldog, Boston terrier and Pug [13]. Patients with congenital vertebral malformations are often asymptomatic with malformations representing incidental findings identified during unrelated radiographic studies. Clinical signs observed in the affected population are usually those of a progressive myelopathy secondary to vertebral canal stenosis, but also to vertebral instability related to the degree of spinal curvature [1,2,4,5]. The prevalence of clinically affected brachycephalic screw-tailed dogs with congenital vertebral malformations is unknown, but could represent an important spontaneous model of spinal deformity. An important factor evaluated in human patients with congenital vertebral malformations causing kyphosis and scoliosis is the degree of spinal curvature. The angular magnitude of a spinal deformity is usually quantified using the Cobb angle [6]. This method is used to guide decisions regarding progression, physiotherapy, orthotic options and surgical interventions [79]. Various techniques have been used to determine the Cobb angle in humans, including manual, digital computer-assisted (semiautomatic), automatic and even smartphone procedures [913]. To the authors knowledge there are just three previous studies that attempted to quantify the degree of spinal curvature in dogs, and none of them used a computer-assisted method [2,4,5]. In the setting of congenital vertebral malformations in dogs, validating a reliable method is an essential first step towards assessment of disease severity, progression, prognostic significance and it may be used to guide treatment. As a first step in understanding the effect of vertebral malformations in dogs, assessing the reliability of a computer-assisted Cobb angle measurement is therefore important. The aims of the present study were to investigate the use of Cobb angle measurements in dogs with congenital thoracic vertebral malformations in order to objectively quantify the degree of spinal curvature (kyphosis and scoliosis) using a open-access, computer assisted, digital radiographic measurement system and also to determine if the degree of spinal curvature was associated with the presence of neurological deficits in dogs with thoracic vertebral malformations. We hypothesized that the method would be reproducible and reliable and that neurological deficits would be more likely in dogs with more severe kyphosis. Materials and Methods Ethics statement This study was considered as sub-threshold for specific ethical approval by the convenor of the school of veterinary medicine ethics committee, as the work involved only analysis of data routinely recorded from normal and necessary clinical procedures. Cases The medical records of the University of Glasgow Small Animal Hospital were retrospectively reviewed from September 2009 to April 2013 to identify French bulldogs, English bulldogs, Boston terriers and Pugs with or without neurological deficits that had lateral and ventro-dorsal digital radiographs of the thoracic spine with at least a single vertebral congenital malformation present. The breed, age and sex were recorded. If there were any neurological deficits associated with the vertebral malformation identified, then the neurological grade at presentation was recorded, using the standard grading system (Table 1) [14]. Patients were then divided into two groups, one where the vertebral malformation was associated with neurological deficits (Group 1) and one without associated neurological deficits (Group 2). The cases used in the present study were also included in a previous study on classification of congenital vertebral malformations [15]. All dogs in group1 had magnetic resonance imaging which confirmed the compressive myelopathy to be secondary to the vertebral malformation on sagittal and transverse T2 weighted images. Radiographic assessment Radiographs of the thoracic spine (lateral and ventro-dorsal views) were performed using a digital radiography system (Siemens, Camberley, United Kingd (...truncated)