High intraosseous pressure as a cause of lameness in a horse with a degloving injury of the metatarsus.

This research article discusses a case where a horse suffering from a severe skin injury on its right metatarsus developed lameness. Despite various diagnostic procedures, the cause of the lameness remained undetermined until high intraosseous pressure, likely due to edema and inflammation, was considered as the source. Following a procedure to relieve the pressure, the horse’s condition significantly improved.

Case Presentation and Diagnosis

• The study focuses on a 6-year-old Paint mare that developed a non-weight-bearing lameness 19 days after being treated for a degloving injury (a type of severe injury where skin is torn away from the underlying tissue) on its right metatarsus, an area located between the horse’s hock and hoof.
• The horse’s discomfort was localized to the area between the tarsus, a cluster of bones in the hind leg, and the metatarsophalangeal joint, the joint where the metatarsus connects with the phalanges or toe bones.
• Various diagnostic procedures such as radiography, arthrocentesis (joint fluid sampling), and ultrasonography of the flexor tendons and suspensory ligament did not reveal the cause of the lameness.

Intraosseous Pressure Measurement and Findings

• The horse was then anesthetized for intraosseous pressure measurement in both the left and right third metatarsal bones. The procedure used a self-tapping cannulated (hollow) screw attached to a pressure sensor.
• The intraosseous pressure in the affected limb was 46 mm Hg, 3.5 times higher than the pressure in the unaffected limb (13 mm Hg).

Cause of High Intraosseous Pressure and Treatment

• The high intraosseous pressure in the affected limb was believed to be caused by edema (swelling from fluid accumulation), inflammation, partial venous thrombosis (blood clot in a vein), and bone neovascularization (formation of new blood vessels) that impaired venous drainage from the bone marrow cavity.
• Fenestration, a surgical procedure that creates an opening in the bone to release pressure, was performed on the affected bone. The next day, the horse’s signs of lameness improved significantly.

Conclusions

• The research highlights that high intraosseous pressure, secondary to edema, inflammation, and venous thrombosis, can be a cause of lameness in horses, especially when other diagnostic procedures fail to identify the source of pain.
• Fenestration can effectively alleviate pain caused by high intraosseous pressure, resulting in symptom relief and improved mobility in the affected limb.