Abstract
Background:
Tendon and ligament injuries in equine athletes pose significant challenges, often leading to prolonged recovery, reduced performance, and an increased risk of reinjury. Current treatment strategies, including conservative and surgical approaches, have shown limited success in fully restoring tendon integrity. Autologous blood derivatives, such as Autologous Conditioned Serum (ACS), have emerged as potential regenerative therapies. However, the clinical efficacy of ACS in treating equine tendinopathies remains under investigation.

Aim:
This study aimed to compare the clinical outcomes of intralesional ACS injections with conservative treatment in horses diagnosed with superficial digital flexor tendon (SDFT), deep digital flexor tendon (DDFT), and suspensory ligament (SL) injuries.

Methods:
A retrospective observational case-control study was conducted using clinical data from 100 horses evaluated for lameness between 2017 and 2022. Horses were categorized into two groups: the IRAP group (n=48), receiving three intralesional ACS injections at one-week intervals, and the NO-IRAP group (n=52), treated conservatively with NSAIDs and a structured rehabilitation program. Lameness assessments and ultrasonographic evaluations were performed at initial presentation and follow-ups at 4, 8, and 12 weeks. Statistical analyses compared changes in lameness scores between the two groups.

Results:
At 4 weeks, improvement in lameness was observed in 51.5% of the IRAP group and 55.6% of the NO-IRAP group. At 8 weeks, improvement rates were 47% and 42.2%, respectively. By 12 weeks, 60.7% of the IRAP group and 55% of the NO-IRAP group showed improvement. However, a subset of horses in the IRAP group experienced transient worsening of lameness (8.5% to 17.7%). Stratification by lesion type revealed better outcomes in the IRAP group for SDFT (58.3% vs. 48%) and SL (51.2% vs. 36%) injuries, whereas the NO-IRAP group had superior results for DDFT injuries (60.9% vs. 46.2%).

Conclusion:
The study suggests that ACS treatment may enhance tendon and ligament healing, particularly for SDFT and SL injuries. However, the transient worsening of lameness observed in some horses receiving ACS warrants further investigation. While findings support the potential benefits of ACS, controlled randomized clinical trials are needed to validate its efficacy and optimize treatment protocols for equine tendon and ligament pathologies.

Key words: IRAP, Autologous conditioned serum, Horse, Tendon, Ligament, lameness