An equine cadaver study investigating the relationship between cervical flexion, nuchal ligament elongation and pressure at the first and second cervical vertebra.

This study examines the association between the hyperflexion of the horse’s neck, activation of the nuchal ligament, and pressure at the first two vertebrae in the neck. It suggests that the excessive pressure generated by such flexing could play a role in developing abnormalities like a nuchal bursa, a condition common in horses.

Methods of the Research

• The study used ten equine specimen heads and necks, exculpating one side of the soft tissue over the cervical spinal column.
• The specimens were positioned laterally on a table in neutral, slightly flexed, and extremely flexed head and neck stances.
• Markers were utilized to measure the bending of the neck. They were placed on the nuchal ligament and drilled into the skull, vertebrae, and withers (the ridge between the shoulder blades).
• In six out of the ten specimens, an inflatable air pouch was used to calculate the pressure between the nuchal ligament and the first and second cervical vertebrae (the atlas and the axis).

Findings of the Study

• The maximum length of the nuchal ligament and the highest pressure values at the nuchal bursa over the atlas and the axis were associated with extreme flexion.
• The pressure over the atlas and the axis was four times and twice the neutral position’s pressure, respectively.
• Over the three separate head and neck positions, neck flexion angles had significant correlations with pressure values and with nuchal ligament length.

Implications of the Research

• This study provided evidence that head and neck hyperextension in horses could result in a significant increase in pressure at the atlas and axis levels.
• Such pressure may lead to pathogenesis of nuchal bursitis, a disease characterized by inflammation of the bursae located in the nuchal ligament.
• Knowing this, horse trainers need to be aware of the risks of extreme flexion, especially for horses already diagnosed with nuchal bursitis or at risk of developing it.