In vitro mechanical properties and failure mode of the equine (pony) cranial cruciate ligament.

This study investigates the mechanical properties and failure behaviour of the cranial cruciate ligament in pony’s joint under laboratory conditions. It is a comparative examination that studied how the ligament reacts to tension before failure and how age affects these properties.

Methodology

• The researchers tested a total of 15 stifle joints isolated from 10 ponies. The age of these ponies ranged from 3 to 25 years, and their weight was between 122 and 208 kg.
• All femur-CCL-tibia specimens were subjected to a specific testing procedure that included mounting them at 48 degrees flexion before applying a tensile preload of 500 grams. These specimens were further subjected to tensile loading until failure.

Findings

• The study showed three distinct modes of sample failure: complete midsubstance CCL rupture, combined tibial insertion avulsion fracture with midsubstance CCL rupture, and combined femoral origin avulsion fracture with midsubstance CCL rupture.
• There were no statistically significant correlations found between the mechanical properties and failure mode of the CCL or the body weight.
• The maximum tensile load that the femur-CCL-tibia samples could withstand varied from 1,945 to 4,326 N, with an average of approximately 2,914 N.
• When considering the pony’s body weight, the mean maximum tensile load measured around 17.98 N/kg.

Comparison to Other Species

• Findings suggested that the pony’s cranial cruciate ligaments are notably stiffer and have a higher elastic modulus when compared to those in other species.

Effects of Age

• The study also analysed the impact of age on the mechanical properties and failure modes of the ligament. It was observed that samples from older ponies (20-25 years old) showed significant decreases in linear tensile load and maximum tensile load, and increases in strain to maximum load compared with those from younger ponies (3-10 years old).