Congenital malformations of the thoracic vertebral column in a mature competition pony.

Overview

• This study reports a rare case of congenital malformations in the thoracic vertebral column of a 14-year-old competition Welsh pony.
• The pony exhibited chronic spinal pain and movement stiffness linked to structural abnormalities in the thoracic spine, despite no neurological deficits.

Detailed Explanation

Background

• Thoracolumbar congenital abnormalities refer to birth defects affecting the middle and lower segments of the horse’s vertebral column (spine).
• Such abnormalities are uncommon in mature, performance-level horses.
• Understanding these congenital issues is important because they can cause pain and impact performance even without obvious neurological problems.

Case Description

• A 14-year-old mature Welsh pony used for competition was presented with:
  • Marked atrophy of epaxial muscles (muscles running along the spine).
  • Spinal pain localized to the mid-thoracic region (around the middle back).
  • Stiffness especially during cantering, indicating potential discomfort or limited mobility.
  • Physical examination showed scoliosis (lateral spine curvature) centered at vertebrae T9-T10.
  • Kyphosis (forward rounding of the thoracic spine) was also present.

Diagnostic Imaging Findings

• Radiographic and postmortem computed tomography (CT) imaging revealed complex congenital malformations including:
  • Abnormal shapes of thoracic vertebrae T10 to T12.
  • Partial vertebral fusion, where two or more vertebrae are abnormally joined.
  • A malformed spinous process (the bony projection off each vertebra).
  • A malformed rib associated with abnormal costovertebral and costotransverse joints (joints where ribs meet the vertebrae).
  • Degenerative changes (wear and tear) in multiple costovertebral and costotransverse joints, likely secondary to abnormal structure and mechanics.

Clinical Significance and Outcome

• The pony’s clinical signs likely originated from the congenital vertebral abnormalities causing chronic thoracolumbar pain and stiffness.
• No neurological deficits (such as nerve damage or weakness) were observed despite the significant spinal malformations.
• Persistent undesirable behavior during riding, concerns for rider safety (notably a young rider), and financial considerations ultimately led the owner to elect euthanasia.

Implications of the Study

• This report emphasizes the need to consider congenital spinal anomalies as an underlying cause of chronic thoracolumbar pain in adult horses, especially when typical neurological signs are absent.
• It suggests that complex vertebral malformations can remain undetected until mature age and manifest as pain or performance issues rather than neurological deficits.
• Veterinarians and equine clinicians should be aware of such anomalies when evaluating cases of chronic back pain or stiffness in horses, even in the absence of overt neurological symptoms.