HOW TO CHOOSE REGENERATIVE MEDICINE AND THERAPIES


loss of fiber. Majewski, et al observed that ACS treatment might shorten recovery time because ACS-aided tendon repair is characterized by repair with well-organized, strong collagen fibers, suggest- ing that the healed tendon should contain fewer imperfections than in repair tissue formed after spontaneous healing. They believed such tissue would be less prone to re-injury, and they acknowl- edged that the biologically active component(s) in ACS that were responsible for the accelerated heal- ing of the injured Achilles tendons remain to be identified.18 The authors believe the horses selected to treat


with ACS for PSD suffered from acute or chronic SL strains rather than major tearing of the SL. Strain is damage to elastic fibers from stretching of the fibers beyond their elastic limit without visual dis- ruption of fibers. This results in pain, swelling, and inflammation within the strained structure as well as potentially causing compressive damage to adjacent nerves.21 To


´th, et al21 clearly showed that


horses with PSD of the hind limbs could also have pathologic changes of the deep branch of the lateral plantar nerve caused by compression from swelling of the PSL. They theorized that this nerve damage could be one potential reason for the poor long-term prognosis of PSD in the hind limbs of horses.21 While ACS could have an indirect effect on nerve pathology by reducing compression on the nerve by reducing inflammation and thus swelling of the PSL, there is evidence that ACS can have a direct effect on pain from compressed nerves. Becker, et al demonstrated that epidural injections of ACS to treat lumbar radicular compression in humans were associated with clinically remarkable positive out- comes, potentially superior to the same treatment method using triamcinolone.20 The authors believe the acutely lame horses in


this study were ideal candidates for treatment with ACS because the ligaments of these horses had no ultrasonographically discernible major disruption of fibers. Lameness of some horses may go undiag- nosed causing it to become chronic if lameness of a fore limb is mild, if the lameness involves both fore limbs, or if the lameness affects one or both hind limbs. The authors believe that as long as major disruption of fibers is not ultrasonographically evi- dent, even horses chronically lame because of PSD are good candidates for treatment with ACS, as it may be possible to return the tissue to normal size and function and heal or treat pain from potential neuropathies. Periligamentous injection, as de- scribed in this report, rather than intralesional in- jection, is indicated for horses without a core lesion. Forcing ACS into ligamentous or tendinous tissue in which there is no tissue void forces fibers apart, disrupting important cross-linking, this may worsen lameness and lengthen time of healing. Short-comings of this study are the short fol-


low-up time and lack of control groups. However, it has been the experience of one of the authorse,in


many cases of PSD in the young Western perfor- mance horse, that if we can get a horse to train a month without immediately getting lame, we have a chance of successfully keeping that horse in training long-term. With that stated, however, many of the horses will get lame again at some point from the same cause albeit usually less severely. When this occurs, we reevaluate sonographically, and unless we have tissue disruption of some sort (core lesion, etc.), we have been able to re-inject most of those and only give them short lay-offs of 5 to 7 days and resume training. Many do this several times in their careers and get into a routine with a fairly consistent interval. As these young Western per- formance horses mature, however, the intervals be- tween flare-up usually widens until they reach 6 years of age in which many seem to mature out of the syndrome. We hypothesize that this is partly due to a reduced training schedule and amount of work needed to stay in top form (i.e., the horse knows its job) but also because the horse begins adaptive remodeling, which becomes complete by the time it is 5 to 6 years old. Occasionally, it was observed that the ligament begins to fail requiring that the horse be removed from training and sub- jected to a different treatment type or prolonged rest period. An important consideration when using regener-


ative products, such as ACS, is that differences may occur between commercially available products. The concentration of IL-1 receptor antagonist pro- tein and IL-1 itself, as well as anabolic growth factor concentrations, may vary among manufacturers. The concentrations may also vary both between and within patients. Hraha, et al6 tested 2 different commercially available veterinary systems, irapc,d and Arthrex IRAP IId, using whole blood in a clot tube as a control. They compared each system us- ing the blood of 5 horses and found that IL-1ra was up-regulated by both systemsc,d and within the con- trol, clot tube, but that the IL-1 to IL-1ra ratio was only increased compared to serum in Arthrex IRAP II,d thus illustrating differences. The authors used one of the systemsc and did not measure IL-1ra or other factors of interest. The authors believe cau- tion should be used when extrapolating this data to other systems used to produce ACS. The authors believe that the large number of


horses with PSD treated with ACS demonstrates the safety and effectiveness of this treatment when horses are selected appropriately. There were no control groups of horses with PSD that received other therapies to which can be compared to the effects of treatment with ACS, but this experience with other treatments of horses for PSD as well as the published results of other clinicians1 indicates that horses treated with ACS are able to be returned successfully to training much sooner than horses receiving other treatment. Treatment with ACS has allowed many young Western performance horses to resume training in time to complete their


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