Imaging diagnosis–Medullary tibial infarction in a horse.

The study presents a case where a lame Andalusian Stallion was diagnosed with a radiolucent lesion in the lower part of its tibia bone, later identified as a medullary infarction following Magnetic Resonance Imaging (MRI) and histological examinations.

Case Presentation and Diagnosis

• The study focuses on an Andalusian Stallion with a lameness in its left hind limb. The horse had a radiolucent, or x-ray transparent, lesion in its tibia, specifically in the metaphysis area or the end of the bone towards the joint. This irregularity was discovered during a radiographic examination aimed at establishing the cause of the lameness.
• Given the severity of another disease from which the horse was suffering, euthanasia was performed. Subsequently, the tibia was subject to further examination using Magnetic Resonance Imaging (MRI).

MRI Examination and Results

• The MRI sequences showed a double line sign, often indicative of osteonecrosis or bone tissue death. However, the signs indicated varying lesion area intensities, making interpretations complex.
• Despite these differences, the MRI results demonstrated a considerable likelihood of a medullary infarction. This condition typically occurs when blood supply to a part of the bone, in this case, the interior medullary section of the tibia, is interrupted leading to the death of bone tissue.

Histological Examination and Findings

• The detected lesion was subject to histological, or microscopic, examination for definitive characterization of the tissue.
• Results from this study indicated that the lesion was characterized by normal spongy bone, areas containing ample fibrous tissue, and a large quantity of necrotic (dead or dying) adipocytes or fat cells in various stages of decomposition, thus confirming the medullary infarction diagnosis.
• The characteristic aspects noted in the histological study correspond well with those expected in cases of medullary infarction, thus affirming the initial diagnosis based on the MRI study.

Conclusion

• This case shows the potential of MRI in detecting, and assisting in the confirmation of, a diagnosis of medullary infarction, even when encountered in a less-common host such as a horse.
• Designed as a comprehensive approach, the study successfully implemented radiographic evaluation, MRI, and histology to uncover the cause of the horse’s lameness, and it was identified as a medullary tibial infarction due to the lack of blood supply in the bone.