Study of cartilage and bone layers of the bearing surface of the equine metacarpophalangeal joint relative to different timescales of maturation.

The research discusses the maturation process of different tissues in the bearing surface of a joint in horses, focusing particularly on juvenile horses. The researchers found that while the collagen network reaches maturity by age 4, the mineral composition of the underlying bone continues to develop past this point. This information could be vital in understanding how to manage the training and racing of young horses.

Research Objectives

• The main goal of this study was to gain more insight into the maturation process of the different tissues that form the functional units of the locomotor system in horses, particularly those in the joints.
• The researchers aimed at comparing the biochemical changes in the tissues of young horses and mature horses. The tissues under scrutiny were in two differently loaded sites of the metacarpophalangeal joint.
• Another objective was to understand the differences in the timescale of development across the different structures of a joint i.e., cartilage, subchondral bone and trabecular bone.

Methodology

• The researchers examined the age-related changes in the biochemical characteristics of the collagen, which forms a part of the extracellular matrix. They did this particularly on hydroxylysine, hydroxyproline, and hydroxypyridinum crosslinks in the articular cartilage, and the underlying subchondral and trabecular bone.
• The study was conducted on two groups of horses; a group of juvenile horses aged between 6 months and 4 years, and a group of mature horses, aged above 4 years. The two groups comprised 13 and 30 horses respectively.
• In the subchondral and trabecular bone layers, the researchers determined the bone mineral density, ash content, and levels of individual minerals.

Results

• The researchers discovered that in juvenile horses, virtually all collagen parameters had already achieved a level similar to that of mature horses. In other words, the collagen network in the joint layers was already mature, regardless of the age of the horse.
• However, the mineral composition in both bony layers was found to be continuing to increase in the juvenile group, unlike in the mature group where it was stable. Specifically, the mineral that decreased in the young horses but remained stable in the mature ones was magnesium.
• The study concluded that in horses aged between 6 months and 4 years, the collagen network of all the layers within the joint has a mature biochemical composition. However, the mineral composition of the subchondral and trabecular bone continues to develop until approximately age 4 years.
• Therefore, there is a disparity in the maturation of the extracellular matrix components of a joint. The disparity could have effects on the capacity of a joint to sustain load, and therefore, should be taken into account when training or racing young animals.