Variations and Implications of the Gross Anatomy in the Equine Nuchal Ligament Lamellae

• Conventional equine anatomy knowledge has been based on outdated findings.
• Modern equine displays anatomic variations that are unreported.
• The equine nuchal ligament lamellae attaches from C2 to C5 and not from C2 to C7 in 35 horses.
• Variations to equine anatomy should be reported so to better understand function.
• As structure governs function, variations in structural integrity reflect in function.

Early literature depicting equine anatomy began with stylized illustrations portraying anatomic structures in a congenial format. This study shows that modern day literature often reflects those early portrayals and, in particular, the description and depiction of the nuchal ligament lamellae (NLL) and its attachments from the second to seventh cervical vertebrae. In the dissection of 35 horses of no specific breed, which were unrelated and of mixed gender and age, it was noted that the NLL was not attached to the sixth and seventh cervical vertebrae. Furthermore, the attachment of the NLL on the fifth cervical vertebrae was quite thin and feeble in nine of those horses and that incomplete fibers were noted in the caudal attachments of the NLL in 15 horses. These variations do not correlate to those early depictions or to most of the existing equine anatomic text. This new information on the equine NLL has functional and clinical implications, with particular reference in the way we currently understand the postural and locomotive properties of the equine neck and cervicothoracic junction.