Effects of osteochondral fragmentation and intra‐articular triamcinolone acetonide treatment on subchondral bone in the equine carpus

Abstract

Summary To determine the effects of osteochondral fragmentation and intra‐articular corticosteroid treatment on dynamics of bone remodelling and fragility, 12 horses each had a unilateral, 8 mm osteochondral fragment created in the distal aspect of one radiocarpal bone. Six of the horses were treated in the fragmented joint, and the other 6 were treated in the nonfragmented joint with 12 mg of triamcinolone acetonide (TA) 14 and 28 days after surgery. All horses were exercised on a high‐speed treadmill starting 15 days, and ending 72 days after surgery. Horses treated with TA in the fragmented joints were significantly less lame than those treated in the nonfragmented joints. Third carpal bones from joints with fragments showed significantly more vascularity, single labelled surface, total labelled surface and mineralising surface in subchondral and subjacent trabecular bone. Trends were also seen towards higher vascular canal volume and osteochondral junction remodelling sites in third carpal bones from fragmented joints. No significant differences were seen in microdamage density or size between fragmented and nonfragmented joints. No significant influence of TA treatment was seen on any parameter measured. The results from this study show that osteochondral fragmentation induces significant changes in remodelling of opposing bones, and that the administration of corticosteroids into joints with fragmentation does not significantly alter bone remodelling or fragility.

Corticosteroids alter the differentiated phenotype of articular chondrocytes

“…Studies have shown that low-to-moderate doses of intraarticular or systemic corticosteroids ameliorate cartilage degeneration following adjuvant-induced polyarthritis in the rat [26] and experimental transection of the cranial cruciate ligament in the dog [43], and have no gross or microscopic adverse effects when used in moderate doses on horses with small osteochondral defects [ 17, 20,28]. Other important variables, both clinically and experimentally, appear to be the local joint environment and experimental procedures [38,51].…”

“…Effects on articular cartilage appear to be influenced by the choice and dose of corticosteroids used [ 17,20,28,53]. Studies have shown that low-to-moderate doses of intraarticular or systemic corticosteroids ameliorate cartilage degeneration following adjuvant-induced polyarthritis in the rat [26] and experimental transection of the cranial cruciate ligament in the dog [43], and have no gross or microscopic adverse effects when used in moderate doses on horses with small osteochondral defects [ 17, 20,28].…”

Musculoskeletal Pathology

“…39 Repetitive cyclic overloading of bone results in focal microdamage, such as trabecular microfractures and focal breaks in the calcified cartilage layer identified in the metacarpal condyle of racehorses. 40 When cellular remodeling is activated to repair areas of weakened bone, osteoclasts exert their effect more rapidly than osteoblasts, resulting in a transient decrease in bone density. The potential exists for fracture propagation within the area of weakened bone if high cyclic loading continues.…”

Influence of Exercise and Intra-articular Site on Canals in Articular Calcified Cartilage of Equine Third Carpal Bones

“…29 The findings appear disparate, and the number, size, stimulus, and mechanism for the appearance of canals penetrating the ACC require further study. 1 These circular openings in the ACC surface, or linear interruptions perpendicular to the osseous-chondral junction, have variably been termed vascular channels, 16,38 vascular canals, 14 cartilage canals, 3 protrusion pores, 20 vascular abutting vessels, 29 cavities, 40 and focal contacts. 25 Elucidation of contents of canals of varying morphological appearances require definition to allow a common terminology to be developed.…”