The effect of intra-articular methylprednisolone acetate and exercise on equine carpal subchondral and cancellous bone microhardness.
Authors: Murray R C, Znaor N, Tanner K E, DeBowes R M, Gaughan E M, Goodship A E
Journal: Equine veterinary journal
Summary
# Editorial Summary Dorsal carpal osteochondral injury remains a significant source of lameness in young racehorses and performance animals in training, yet the safety profile of intra-articular corticosteroids—routinely used to manage exercise-associated joint pain—remains contentious among practitioners. Murray and colleagues investigated whether methylprednisolone acetate (MPA) altered the mechanical integrity of carpal bone by comparing microhardness properties in treated versus untreated joints of eight 2-year-old fillies receiving four intra-articular injections at fortnightly intervals whilst undertaking a standardised treadmill exercise programme over 10 weeks. Contrary to the hypothesis that corticosteroids would compromise bone quality, no significant difference in subchondral or cancellous bone microhardness was detected between MPA-treated and diluent-treated joints, regardless of anatomical site; however, the study identified that cancellous bone trabecular struts consistently demonstrated 18–19% greater microhardness than overlying subchondral bone across all samples. These findings suggest that a standard corticosteroid injection protocol does not impair bone mechanical adaptation to short-term training load, potentially allaying concerns about accelerated degenerative change, though the authors appropriately caution that investigation into calcified cartilage, alternative corticosteroid formulations, and drug diffusion patterns would strengthen confidence in these conclusions for clinical application.
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Practical Takeaways
- •Intra-articular corticosteroid injections at standard doses do not mechanically weaken carpal subchondral or cancellous bone in young horses during short-term training, addressing a significant concern about their safety in athletic horses
- •The lack of negative effect on bone mechanical properties suggests MPA can be used for pain management without sacrificing bone integrity, though further research on other corticosteroid preparations and longer-term effects is needed
- •Mechanical differences between cancellous and subchondral bone (18-19% variance in hardness) may be relevant to understanding injury patterns in carpal osteochondral disease
Key Findings
- •Intra-articular methylprednisolone acetate (MPA) at the tested dose produced no significant effect on subchondral or cancellous bone microhardness in middle carpal joints
- •Cancellous bone trabecular struts demonstrated 18-19% higher microhardness values than overlying subchondral bone at all test sites
- •MPA administration did not alter subchondral or cancellous bone mechanical adaptation to short-term treadmill exercise over 70 days
- •Findings suggest intra-articular MPA at this dose does not increase propensity for carpal bone injury in horses undergoing exercise