Metaphyeal and Diaphyseal Dysplasia of the Third Cervical Vertebra Secondary to Physeal Necrosis in a Quarter Horse Foal.

This research paper focuses on a unique case of a Quarter horse foal suffering from an abnormal condition of the third cervical vertebra (C3), likely caused by a lack of adequate blood supply injuring the region where its bone growth occurs. The study proposes that such blood flow decrease can lead to bone deformities in horses.

Horse Case Background

• The subject of this research was a 1-month-old Quarter horse foal that underwent a necropsy examination after showing signs of sudden onset of uncoordinated movements followed by a month of deteriorating health.
• The foal had notable deformities in the C3 vertebra, specifically the metaphysis and diaphysis (the ends and the middle of the bone respectively), which were considerably shortened and of an unusual white-tan color.
• There was no evidence of a fracture or inflammation indicating trauma or infection.

Diagnostic Findings

• The examination revealed physical narrowing of the spinal canal caused by pressure from the front portion of C3 rotating towards it.
• Under microscopic analysis, the dorsal compact bone of C3 was found absent, and around 80% of the physis (the growing part of the bone) parallel to the spinal canal was replaced with fibrous tissue and thickened healthy trabecular bone.
• Both front and rear growth plates of C3 displayed widespread areas of coagulative necrosis, a condition where cells die due to lack of blood supply, in the hypertrophic and calcification zones that are crucial for bone growth and health.
• Marked decreases in the production of bone marrow with some fibrosis or scarring were noted in the metaphyses and diaphysis of C3.
• The epiphyses, or the ends of the bone, appeared normal under microscopic examination.

Proposed Pathogenesis and Clinical Relevance

• The authors hypothesized that the abnormal bone growth and necrosis in the physes were a result of a temporary, incomplete, and possibly multiphasic lack of blood supply involving the nutrient artery responsible for its nourishment.
• Such findings underscore the potential importance of ischemic or blood-deficient injury to the physis in the development of spot-specific (focal) bone dysplasia, or abnormal growth, in horses.