Intra-osseous pressure of the equine third metatarsal bone.

This research article explores the intra-osseous pressure, or pressure within the bone, of the equine third metatarsal bone. The research was conducted on pony foals at various ages and considered various factors influencing the intra-osseous pressure, finding no significant changes with increasing age or location within the bone but significant influence from venous and arterial pressures and physical manipulation of the joint or bone.

Study Design and Participants

• The study was conducted on 8 pony foals aged between 1 and 26 weeks, with an additional one-off examination conducted on 5 ponies aged 1-5 years.
• Measurements were taken while the animals were under general anesthesia and lying on their side (lateral recumbency).
• The researchers measured the intra-osseous pressure at two points in the metatarsal bone: the epiphysis and the diaphysis.

Monitored Variables

• Alongside the intra-osseous pressure, the researchers also monitored the saphenous venous pressure and the lateral superficial plantar metatarsal arterial pressure.
• These two added measurements help understand how venous and arterial pressures might influence the intra-osseous pressure.

Key Findings

• The results showed no significant changes in intra-osseous pressure with the increasing age of the foals or between the two tested locations within the bone (epiphysis and diaphysis).
• Where individual readings were concerned, the diaphyseal pressure exceeded the epiphyseal pressure in 32 of the 36 measurements.
• Tests involving saphenous vein occlusion and intravenous adrenalin revealed that both venous and arterial pressures influence the intra-osseous pressure.

Testing and Results

• Test with intra-osseous injection of heparinized saline resulted in a significant increase in intra-osseous pressure on the injected side of the growth plate while, generally, the non-injected side didn’t exhibit a similar rise.
• Simulated joint effusion (swelling) showed an increase in intra-osseous pressure in the adjacent meta-tarsal epiphysis, while flexion (bending) of the joint resulted in increased pressure in both epiphyseal and metaphyseal areas.