• Aiken, SC

    info@equus-soma.com

     
  • Equus-Soma

    Equine Osteology & Anatomy Learning Center

     
  • Waldoboro, ME

    207-542-6132

  • ECVM - Equine Complex Vertebral Malformation

              ECVM   is the acronym recently assigned to a developmental anamoly affecting the skeletal bones and musculature at the base of the horse's neck, specifically the sixth and seventh cervical vertebrae (C6 & C7), the 1st and 2nd sternal ribs and associated soft tissue structures.  
              The presence of this condition was brought to the attention of the horse world by Australian equine anatomist Sharon May-Davis.  Sharon's peer-reviewed publications, resulting from years of research and hundreds of dissections, established the presence of this condition in a variety of breeds, most notably Thoroughbreds and Thoroughbred derivatives. In the past 6 years, others have published similar findings that support her observations.  Both American and Italian studies found the ECVM in Warmbloods, Quarter Horses and Arabs.  (See Sidebar for links to all references).

           Since the manifestation of ECVM is complicated, the research is ongoing and questions abound, the best source of information is from Sharon herself. Scroll down and click on the link to her Webinar with Wendy from December 2020.

              Awareness and recognition of ECVM in the equine community and especially within veterinary circles has been painfully slow.  Symptoms can mimic other issues of caudal neck pain or neurological problems. Typical radiographic protocols to assess more common cervical issues such as osteoarthritis can show the malformation of C6 but veterinarians are not always tuned in to looking for it.  Sharon May-Davis also published a paper through the Japanese Government Racing department in which she outlines how to radiograph C6 and C7 specifically to determine the presence or absence of the malformation.  Recently, one of Sharon's Doctoral students published a paper with even more detailed instructions (Gee et al. 2020).
             Meanwhile, equine bodyworkers and physiotherapists (present company included) are encountering more horses who present with a perplexing lameness and/or have developed performance and behavioral issues that cannot be positively identified with regular veterinary diagnostics.  We recently brought such a horse to the attention of a local veterinarian who used the radiographic protocol published by Gee et.al. 2020.  The X-rays clearly identified a C6-C7 bilateral malformation.

  •              My introduction to this anomaly dates back to 2016 when I uncovered the partial skeleton of a 3 year-old Thoroughbred mare who had the malformation of C6 and C7.  Since then, we have accumulated bones from approximately 50 horses of different breeds and ages and discovered many variations of ECVM.  Our ECVM collection in the Learning Center is at a dozen horses at the time of this writing and includes several Thoroughbreds, a Friesian, a Warmblood, Draught, a Quarter Horse and 2 Appaloosas plus a few of undetermined breeding.  

                 Below you will find a summary of what textbooks describe as normal cervical morphology.  The description of what constitutes  ECVM along with representative photos of bones from the Learning Center collection can be found here.

  • Cervical Morphology - Overview

             - Horses, like all mammals (with the exception of sloths and manatees) have 7 neck or "cervical" vertebrae.

             - The first cervical, C1 or "atlas", connects to the base of the skull.
             - Both C1 and C2 ("axis") have distinctly different morphologies from each other, as well as from the remaining cervical vertebrae.
             - C3, C4 and C5 are generally similar to one-another in appearance but each gets progressively shorter and broader.
            

  •           
              The ventral side of C6 however, is distinquished from the other cervical vertebrae by the presence of bony "ridges" that extend from the cranial to caudal ends along the left and right sides of the vertebral body (click on image at left).  These "ventral tubercles" or "laminae" are actually branches off of the transverse processes and in the normal C6 are of equal, or near equal, length.

              The last cervical vertebra (C7) is the shortest of all with its ventral surface also differing from that of C6.  The normal C7 does not have the ventral tubercle "ridges" characteristic of C6.  Instead, C7 has two much smaller ventral tubercles that lie along the midline replacing the ventral crest (as illustrated here by the yellow arrows).

              The ventral tubercles of C6 and ventral surface of C7 are attachment points for the Longus colli muscles that control flexion, rotation and stability of the base of the neck (May-Davis, 2015).  These paired, deep perivertebral muscles are highly innervated with proprioceptive characteristics and are considered to be "cybernetic" muscles (Denoix & Pailloux, 2011). The role of cybernetic muscles is to sense motion and orchestrate fine postural movements.   For those interested a detailed description of the anatomy of the musculature surrounding the cervical vertebrae, download this PDF: Rombach et al. (2014).

    Meanwhile, click on the image below to see examples of actual ECVM bones.

  • Sharon May-Davis: Explains ECVM
  • Examples of ECVM bones from the Learning Center collection.

    Show Me More!

    ECVM Bones
    ECVM Bones

    Examples of ECVM bones from the Learning Center collection.

    Show Me More!

  • Pamela & Diane Review ECVM Updates