BY KATHARINA B. ROS1; ALDO DOVEREN2; CHRISTIE DREESSEN2; RALF PELLMAN3; FRANCESCA BECCATI4; ELISA ZIMMERMANN5; OTTMAR DISTL5
IMAGES AND GRAPHICS: THE AUTHORS
To give this article its full title: Radiological Methods for the Imaging of Congenital Malformations of C6-T1, the First and Second Sternal Ribs and Development of a Classification System, Demonstrated in Warmblood Horses
1. Introduction
In recent years, it has been recognized that malformations in the equine cervicothoracic (C-T) junction are present in many horse breeds and may be associated with a clinical presentation of local pain and restriction of motion, proprioceptive deficits, ataxia, lameness, postural abnormalities and, unusually, even dangerous behaviors. Within the past twenty years, this syndrome has been variously described as equine caudal cervical morphologic variations (ECCMVs) [1], abnormalities of the ventral lamina of the sixth cervical vertebra (AVL-C6) [2,3,4], and equine complex vertebral malformations (ECVMs) [5,6,7]. The latter encompasses the myriad of osseous, ligamentous, vascular, nervous and muscle changes that can affect the C-T junction and the function of the brachial plexus [5,6,7]. Pathology of the cervical spine and the C-T junction can be associated with neck pain, reduced cervical range of motion, proprioceptive deficits, ataxia, forelimb and hind limb lameness, a base-wide forelimb stance, and abnormal behavior [2,5,8]. Advanced diagnostic imaging techniques for diagnosis of disorders of the cervical spine are available [9,10,11,12,13,14,15,16], but radiographic examination remains the first diagnostic imaging technique of choice to investigate the cervical vertebrae and the C-T junction due to practical reasons such as availability, noninvasiveness and standardizable features [17,18]. Radiological interpretation of this difficult area depends on the knowledge of the radiologist or veterinarian and the quality of the images [17,18,19].
Previous reports focused on C6 only to provide retrospective research about the anatomical variations versus malformations of C6 and C7 [3,4,20,21]. A previous study stated that it was difficult to image C7 and especially the first thoracic vertebra (T1) [6]. To the authors’ knowledge, the radiographic methods to image the first (R1) and second (R2) ribs using portable radiological devices in the field has not been described before. The aims of this study were to describe new radiographic methods to separately image the left and right side of the C-T junction, R1 and R2 and to describe the radiographic appearance of the malformations of C6, C7, T1 and the first and second ribs using a new detailed classification system. The authors hypothesized that the presented radiographic methods allowed for the identification of different grades of malformations of C6, C7, T1, R1 and R2.
2. Materials and Methods
2.1. Ethical Statement: This study was approved by the Institutional Review Board of the University of Veterinary Medicine Hannover (Foundation) and the state veterinary office from Lower Saxony, Oldenburg, Germany (Institutional Animal Care and Use Committee, IACUC) (33.19-42502-05-16A023) on 6 January 2017. The handling of the horses followed European Union guidelines for animal care and handling and the Guidelines of Good Veterinary Practices.
2.2. Study Population and History: Radiographs of the C-T junction from C6 to T2 were obtained from 39 warmblood horses from January 2021 to August 2022, due to requests by owners for clinical evaluation. There were 22 females, 14 intact males and 3 geldings, ranging in age from 6 months to 18 years with a median age of 5 years. All were warmblood horses including 14 Westphalian (Westphalian Breeders’ Association, Münster, Germany), 8 KWPN (Royal Warmblood Studbook of the Netherlands, Ermelo, The Netherlands), 6 NRPS (The Netherlands Riding Horse and Pony Studbook, Lunteren, The Netherlands), 4 AES (Anglo European Studbook, Schijndel, The Netherlands), 3 Oldenburg, and 1 Belgian and Hanoverian warmblood, Trakehner and Zangersheide.
2.3. Radiographic Method: Radiographic images of the caudal cervical column including the C-T junction were obtained in the standing horse. All images were acquired using a DEVO-II digital radiographic (DR) system (Fuji, Japan) with generators capable of 90 to 200 kV and 20 to 30 mA and veterinary image management software (Equine Veterinary solutions, vsol 6), with the same operators performing all the procedures...
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