IN-DEPTH: ULTRASONOGRAPHY IN LAMENESS DIAGNOSIS


cell death, ischemia, and/or hematoma/exudate. Most physical therapeutic modalities target the removal of edema/hematoma to minimize ongoing ischemia. In doing so, the tissue physiology the- oretically is augmented, resulting in well-aligned type-1 collagen fascicles and decreased cellular metaplasia. With a large core lesion, the SB may be surgically


“split” to allow extrusion of the exudate. With de- bris reduction, further vascular compromise is min- imized. More recently, some surgeons may use phacoemulsification (TenX) for removal of necrotic and inflammatory debris.b For pathology involving the axial aspect of the SB, some surgeons recommend fetlock arthroscopy.6 Generally, though, arthroscopy is reserved for cases that respond to intra-articular fetlock anesthesia and are refractory to conventional therapies.


Extracorporeal Shock Wave Therapy


Shock wave therapy (ESWT) is used widely for the treatment of acute and chronic SB disease. Pro- posed mechanisms of action include analgesia, facil- itation of lesion decompression, and stimulation of paracrine secretion of fibroblasts to stimulate heal- ing. ESWT is widely considered to be a safe and efficacious treatment of SB pathology. The au- thor’s practice routinely uses ESWT, particularly when the sesamoid bone is involved.


Laser Therapy


Laser therapy appears to have multiple effects on soft tissues, including analgesia, enhancing lymphatic and vascular circulation, and enhancing cellular func- tion. Laser therapy has been used extensively for treatment of soft tissue lesions in humans and horses. Recent advances in technology have al- lowed for more energy to be delivered with multiple laser wavelengths and various protocols. High-en- ergy laser therapy is thought to increase fibroblast numbers and fibroblast function. Laser also ap- pears to have an analgesic effect in some patients. A recent study involving 150 sport horses with soft tissue injuries demonstrated reduced lameness scores and improved ultrasonographic appearance following high-energy laser treatment.11


8. Regenerative Therapies


A broad range of regenerative options exist from which the clinician may choose. Unfortunately, there is no Food and Drug Administration-approved product for SB treatment. Additionally, studies that compare safety and efficacy do not currently exist. As a practitioner, one must make choices about regenerative options based largely on per- sonal experiences, small noncontrolled studies, in- terpersonal references, and anecdotal evidence. There continues to be debate as to if/how stem cells actually turn into the desired tissue. More re- cently, the “niche” or environment surrounding im- planted stem cells is thought to affect the function of


14 2018  Vol. 64  AAEP PROCEEDINGS


these cells. Regenerative therapies rely on para- crine molecular signaling to play a central role.10,12 In addition, studies suggest that a high number of mesenchymal stem cells (MSCs) may result in higher risk of adverse events and overall lower effi- cacy at early time points in poorly vascularized im- plantation sites.13 Also, (fresh) cells may be more effective than cultured cells.14–16 Detailed discus- sion of the growing number of signaling molecules and their effects is beyond the scope of this paper.17


Platelet-Rich Plasma


At the time of writing this article, the use of PRPs is used widely and accepted as safe and effective. Recently, platelets have been shown to have power- ful antimicrobial properties. However, isolation of equine platelets is more challenging than isolation of platelets in other species due to variable equine hematocrit levels. Furthermore, there is a high de- gree of variability between PRP-producing sys- tems.18 Red blood cell and white blood cell numbers in PRP will likely impact tissue response. The platelets that are injected are either lysed be- fore injection or they degranulate after injection, releasing numerous signaling agents.19 Care must be taken when injecting platelets intralesionally, as it has been the author’s experience that injecting too high a volume/number into a lesion leads to an ad- verse response. It should be noted that there is no known optimal dosage of platelets. The clinician should not force PRP into the lesion. Also, a com- mon practice among human sports medicine practi- tioners is to avoid the use of nonsteroidal anti- inflammatory drugs (NSAIDS) following regenerative therapies, including PRP. NSAIDS compromise platelet function and are thought to mitigate the tis- sue response following PRP injection.20 In the hu- man patient, some degree of discomfort is expected initially, with benefit of the treatment anticipated in 4–6 weeks. In contrast, many equine practitioners prescribe NSAIDS following PRP injection and ex- pect a shorter time interval before realizing the benefits.


Bone Marrow as a Source of Stem Cells and Other Factors


Equine bone marrow can be harvested from the sternum or the ileum.21,22 Bone marrow contains relatively large numbers of MSCs, platelets, and a broth rich with growth hormones.17 Some clini- cians only use the noncellular fraction to inject into lesions. Others submit bone marrow for cul- turing and expansion before injections.23 Hall24 reports a good prognosis for return to racing fol- lowing treatment with intralesional bone marrow aspirate. Similarly, Herthel25 reports favorable response with whole bone marrow aspirate. It has been the authors’ experience that in a small number of cases, injection of cultured cells can elicit an undesirable proliferative response in the area treated.


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