IN-DEPTH: RACING-RELATED LAMENESS 7. Underwater Treadmilling


Aquatic therapy has become increasingly popular in its use for rehabilitation of equine musculoskeletal injuries. The mechanism of action of aquatic ther- apy and its potential use in the clinical management of equine OA has been recently reviewed.8 Recent human research has increased our understanding of neuromuscular responses to joint pain.9 Joint mechanoreceptors are characterized as sensory re- ceptors within periarticular tissues that respond to changes in joint position and motion and are also important in regulating neuromuscular control as- sociated with joint stability.10 Pain, inflammation, and joint effusion alter the normal sensory input from articular mechanoreceptors, which may cause motor neuron excitability and reduced muscle acti- vation.11 Experimentally induced knee effusion produced significant quadriceps muscle inhibi- tion.12–14 Joint instability alters the distribution of weight-bearing forces across articular surfaces and induces an increase in the recruitment of adjacent muscles to help aid in joint stability.15 The result- ing functional imbalance and paired agonist-antag- onist muscle groups contributed to increased joint instability and altered limb biomechanics, which leads to further progression of OA and chronic mal- adaptive compensatory mechanisms.16 There is an increasing perception among veterinarians that joint injuries may recur or be exacerbated as the result of muscle weakness, reduced joint range of motion, and poor proprioception, as exemplified by immobilization of the equine metacarpophalangeal joint. The entire musculoskeletal system must be rehabilitated to return the horse to optimal perfor- mance.8 Recently, the use of underwater tread- milling has been assessed in the equine OA model, and both decrease in osteoarthritis as well as im- proved proprioception were demonstrated.h This is a clear demonstration that underwater treadmilling can be used as an adjunctive device for the treatment of traumatic joint inflammation, and there is no indication that it could not be used with a racehorse in full training.


8. Autologous Conditioned Serum (IRAP or IRAP II)


Autologous conditioned serum (ACS) was initially developed for the treatment of human OA as a prod- uct called Orthokinei and was initially tested in horses in Europe and shown to be particularly ben- eficial in OA (of the distal interphalangeal joint) not responding to triamcinolone and HA.j Orthokine was subsequently distributed in the United States as IRAPk and in an experimental study17 was shown to provide benefit in osteochondral fragment–in- duced equine OA. Horses received 6 mL of ACS at 14, 21, 28, and 38 days after treatment (control horses received 6 mL of saline intra-articularly at the same time). Horses treated with ACS were ob- served to have significantly reduced lameness in the OA limbs even 5 weeks after the last treatment compared with placebo-treated horses. There was


also a significant reduction in synovial membrane hyperplasia in treated compared with placebo OA joints at day 70 and a trend for improvement (P  0.10) in cartilage gross score and cartilage histo- chemistry noted in ACS-treated OA joints compared with placebo-treated OA joints. The hypothesis that the main effect of this new therapy was signif- icant increases in interleukin (IL)-1 receptor antag- onist protein (IL-1ra) was confirmed, with increases seen at days 35 and 71. A newer product, IRAP II,l with a modified tech-


nique including a newly designed device with dual ports, has since been produced, and a comparative study was performed on the cytokine profiles of IRAP and IRAP II with the use of equine blood.18 Specifically, the level of IL-1ra in IRAP II was significantly increased compared with IRAP, and the ratio of IL-1ra to IL-1 also significantly in- creased in IRAP II compared with IRAP. On the other hand, there was a significantly increased level of tumor necrosis factor- in IRAP compared with IRAP II but no significant difference in IL-1levels. Production of insulin-like growth factor (IGF)-1 and transforming growth factor-was both significantly increased over serum alone, and no significant dif- ference between the two products was seen. On the basis of the extrapolation of doses used in this study, the recommendation for IRAP after arthroscopic surgery is 6 mL in knees, fetlocks, distal interpha- langeal joints, and tendon sheaths but 10 to 12 mL in femoropatellar or femorotibial joints. Treatment in the latter joints would therefore require two prep- arations (two preparations of IRAP or IRAP II to give three injections at this dose rate). The use of the IRAP products has considerably increased in racing jurisdictions outside the United States. They represent a specific biological therapy without negative side effects and have been well accepted by racing jurisdictions other than in Scan- dinavia, where there have been attempts to ban their use. There is no scientific validity to exclud- ing such products from use in the competing athlete. In the 2009 joint therapy usage survey, sport horse practitioners were significantly more likely than racehorse or show horse veterinarians to use IRAP products (P  0.0035 and P  0.04, respectively), but this was in the United States. The author sug- gests that the use of IRAP in racehorses is used more often by racetrack practitioners outside of the United States.


9. Platelet-Rich Plasma


Platelet-rich plasma (PRP) has been advocated as a way to introduce increased concentrations of growth factors and other bioactive molecules to injured tis- sues in an attempt to optimize the local environ- ment. There are various definitions of PRP, but the consensus now is that the product should have an increase in platelet content over the level in blood. The initial enthusiasm for PRP was based on growth factors within the -granules including transform-


AAEP PROCEEDINGS  Vol. 59  2013 439


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