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Could they just be incidental?
Equine Veterinary Journal, 2024
Obi Veterinary Education
October 18, 2025
Sue Dyson, Kathryn Phillips, Shichen Zheng, Monica Aleman
Background
Congenital variants of the ventral laminae of the sixth (C6) and seventh (C7) cervical vertebrae in horses have been debated in terms of their clinical relevance. Some studies suggest associations with neck pain, neurological deficits, and lameness, while others indicate they may be incidental findings. This study aimed to determine the prevalence of these congenital variants and their relationship with other radiological abnormalities in the cervicothoracic region of Warmblood horses.
Methods
A cross-sectional study was conducted on 223 Warmblood horses aged ≥3 years undergoing clinical evaluation at two referral institutions. The sample included 127 control horses and 96 cases presenting with neurological signs, neck pain or stiffness, or neck-related forelimb lameness. Standardized radiographic examinations of the cervical (C5–C7) and cranial thoracic (T1–T2) vertebrae were performed. Radiographs were analyzed by assessors blinded to the horses' clinical status.
Results
Congenital variants of C7 were observed in 24.2% of horses, with a higher prevalence in control horses (29.2%) than in cases (16.7%). No association was found between congenital variants and other radiological abnormalities, including articular process (AP) modelling, spondylolisthesis, intervertebral foramina narrowing, or discospondylosis. However, cases were more likely to exhibit severe AP modelling at C6–C7 and C7–T1, vertebral malalignment, and intervertebral joint abnormalities compared to control horses.
Limitations
Radiographs were assessed independently by one evaluator at each institution, which could introduce interobserver variability. Additionally, the study population was limited to Warmbloods from referral centers, which may not fully represent the general equine population. The study did not include longitudinal follow-up to assess the progression of radiological findings over time.
Conclusions
Congenital variants of the ventral laminae of C7 were not associated with clinical signs or other radiographic abnormalities of the cervicothoracic region. These variants were more common in clinically normal horses. Severe AP modelling, spondylolisthesis, and intervertebral joint disease were more prevalent in horses with clinical signs, suggesting that these factors, rather than congenital vertebral variants, may be more relevant to cervicothoracic pathology in Warmbloods. Radiographic evaluations should extend to the cranial thoracic vertebrae (at least to T2) when assessing horses with suspected cervicothoracic disease.
(A) Lateral–lateral radiographic image of the fifth cervical (C5) to second thoracic vertebrae of a control horse of 5 years of age. Cranial is to the left. There is a normal ventral profile of the vertebral bodies of both the sixth (C6) and seventh (C7) cervical vertebrae. The articular processes of C5–C6, C7–T1 and T1–T2 are normal. There is mild modelling of the articular processes of C6–C7. The intervertebral foramina are all normal in size. The vertebrae are normally aligned. (B) Lateral–lateral radiographic image of the sixth cervical (C6) to first thoracic (T1) vertebrae of a control horse. Cranial is to the left. Both ventral laminae of C6 are transposed to the vertebral body of the seventh cervical (C7) vertebra and extend slightly less than half the length of the vertebral body. There is mild modelling of the dorsocaudal aspect of the vertebral fossa of C7. The C7–T1 articular processes are moderately enlarged, with a narrowing of the intervertebral foramen. (C) (i) Lateral–lateral radiographic image of the sixth cervical (C6) to first thoracic (T1) vertebrae of a case with neck pain/stiffness. Cranial is to the left. Both ventral laminae of C6 are transposed to the vertebral body of the seventh cervical (C7) vertebra; there is an additional lamina which extends further distally (arrowhead). The ventral processes extend more than half the length of the vertebral body. The articular processes of C6–C7 and C7–T1 are asymmetrically moderately enlarged (modelled). There is a narrowing of the intervertebral foramina at C6–C7 and C7–T1. The head of the vertebral body of C7 is slightly displaced ventrally. There is slight modelling of the ventrocaudal aspect of the vertebral fossa of C6 (spondylosis deformans) (white arrow). The head of the vertebral body of T1 is slightly displaced dorsally. There is mild modelling of the dorsocaudal aspect of the vertebral fossa of C7 (black arrow). (C) (ii) Left 45° ventral-right dorsal oblique image of the seventh cervical and first thoracic vertebrae of the same horse as in Ci and Ciii. Cranial is to the left; left is to the top. The left articular processes (at the top of the image) are smaller than the right. Compare with Ciii. (C) (iii) Right 45° ventral-left dorsal oblique image of the seventh cervical and first thoracic vertebrae of the same horse as in Ci and Cii. Cranial is to the left; the right is to the top. The right articular processes are larger than the left (compare with Cii), and there is an osseous spur (arrow) projecting into the intervertebral foramen. (D) Lateral–lateral radiographic image of the fifth cervical (C5) to first thoracic (T1) vertebrae of a control horse. Cranial is to the left. There is a vestigial ventral lamina on the caudoventral aspect of the vertebral body of C7 (arrow). There is moderate enlargement of the articular processes of C6–C7. There is slight ventral displacement of the cranial aspect of the vertebral body of C7 and subtle modelling of the ventrocaudal aspect of the vertebral fossa of C6.
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