# Identifying by Radiograph Grade 4 Aplasia of the Caudal Lamina Ventralis in the Equine Sixth Cervical Vertebra and Three Coinciding Morphological Variations

## TL;DR

This study identifies a specific bone abnormality in horses' cervical vertebrae using radiographs and finds three related anatomical variations that may help diagnose neck pain.

## Contribution

The study introduces a radiographic method to identify grade 4 aplasia of the caudal lamina ventralis in equine C6 vertebrae and reports three coinciding anatomical variations.

## Key findings

- Radiographic identification of C6 aCLV4 is possible using the caudal border of the transverse process as a reference.
- Twenty horses with C6 aCLV4 were confirmed by gross morphology and showed three anatomical variations.
- The findings may assist veterinarians in diagnosing neck pain and determining the need for further imaging.

## Abstract

This study aimed to identify the relevant bony landmarks in C6 radiographic images of a complete caudal absence of the lamina ventralis in affected horses. One cadaveric study identified this specific malformation as a grade 4, where the findings revealed a strong dependency in transposing the absent caudal lamina ventralis from C6 to C7’s ventral surface. In these horses, reports of neck pain were more common. Hence, the objective of this study was to radiographically determine a C6 grade 4 absent caudal lamina ventralis in a live horse only when the clinical symptoms warrant further investigation. The study revealed that the first point of reference was the connection between the caudal border of the transverse process and the vertebral body. This junction provided a guide to the cranial aspect of the caudal lamina ventralis, where its morphology could be evaluated. From here a grade could be calculated in the affected horses. The radiographic findings identified 20 cases that were confirmed by the corresponding gross morphology, during which three coinciding anomalous variations were noted—in the longus colli muscle, C7 foramen transversarium, and vertebral artery. Therefore, the results reported here might assist veterinarians in the diagnosis of neck pain and/or indicate the need for further diagnostic imaging.

To date, radiographically identifying the bony landmarks relevant to diagnosing the complete C6 aplasia of the caudal lamina ventralis (C6 aCLV4) has not been described. Furthermore, a gross study has identified C6 aCLV4 as the main correlation between transposition of the CLV from C6 to C7, where coinciding neck pain was commonly reported. This study aimed to identify C6 aCLV4 in radiographs, where the outcome might benefit equine practitioners in isolating neck pain. Initially, the relevant bony landmarks were radiographically determined from a normal C6 by applying a lateral 30° dorsal–ventral oblique view. From here, the caudal border of the transverse process (TP) projecting from the vertebral body became the defining point of reference due to the image clearly demarcating the adjacent CLV. In C6 aCLV4 cases, the CLV is completely aplastic caudal to the TP. Twenty mixed-breed horses (13 males/7 females) aged 3–22 years radiographically demonstrated a C6 aCLV4, which was confirmed by their corresponding gross morphology. During this process three anomalous variations became apparent—in the longus colli muscle, C7 foramen transversarium, and vertebral artery. Therefore, this study demonstrates effective techniques for identifying C6 aCLV4 in horses, where the results might assist veterinarians in diagnosing neck pain while providing anatomical clarity.