Repair and function of synovium after arthroscopic synovectomy of the dorsal compartment of the equine antebrachiocarpal joint.

This study explores how the tissue that lines the joints in horses (synovium) repairs and functions following an arthroscopic synovectomy in the dorsal compartment of the equine antebrachiocarpal joint. The researchers used a variety of techniques and comparisons to examine this, and found evidence to suggest that the synovium was able to restore and display increased metabolic potential following the procedure and over time, and that exercise didn’t accelerate this repair process.

Methods Used in the Study

• The study used a variety of observational methods to explore the synovium’s reparative ability, including gross, histological, and ultrastructural examination.
• The scientists used transmission electron microscopy to estimate the functional potential of the cells within the synovium by observing their organelles (the internal components of cells).
• The study compared the findings from horses that were rested and those that were exercised to see if exertion could affect the healing process of the synovium. The effects of exercise were gauged through lameness examinations and through observations of the articular cartilage (the smooth, white tissue that covers the ends of the bones where they come together to form joints).

Experimental Treatment and Observations

• A 7mm diameter motorized synovial resector was used to perform a subtotal synovectomy (partial removal of the synovium) in one antebrachiocarpal joint (upper front limb joint) of each of the eight horses involved in the study. The other joint served as a control.
• After two months of rest, half of the horses were subjected to rigorous exercise for the remainder of the study while the other half were kept at paddock rest.
• The horses underwent lameness examinations and synovial fluid analysis at regular intervals: 0, 2, 30, 60, and 120 days.
• Synovium and articular cartilage from all the horses were examined at necropsy (animal autopsy) at 120 days.

Findings of the Study

• None of the horses showed signs of lameness during the study, and the joints that underwent the subtotal synovectomy displayed signs of transient synovitis (short-term inflammation of the synovium).
• While the concentration of hyaluronan (a substance that helps lubricate and cushion joints) in the treated joints decreased at 2 days, it returned to normal by 60 days.
• The composition of the synovial fluid, including its concentration of hyaluronan, was not altered by exercise.
• There was no significant damage observed to the cartilage in any of the joints.
• By 120 days after the synovectomy, the healing synovium lacked villi (small, finger-like projections) and had a fibrotic subintima (a layer of tissue beneath the surface became fibrous), but an intimal layer (internal surface layer) was present within the repair tissue.
• The cells within the repair tissue appeared actively engaged in both synthesis (build-up of cellular products) and phagocytosis (the ingestion of bacteria or other material).
• Exercise did not influence any of these findings.

Implications of the Study

• The study suggests that 120 days after a subtotal synovectomy, the resected synovium can restore and display increased metabolic potential. This indicates that the joint environment was maintained despite partial removal of the synovium.
• Despite the imposition of rigorous exercise, the synovectomized joints were able to withstand the added stress and the rate of synovial repair was not sped up by exercise.