Issue 2 • 2017
Tracks of My Tears: Corneal Conditions Seen in the Field ANN E. DWYER DVM
Review of the Main Shoulder Conditions in Horses JEAN-MARIE DENOIX DVM, Agrégé, PhD, HDR, Cert. ISELP, Assoc. ECVDI, DACVSMR
Stem Cells: Latest Research and Applications – What/When Does It Work? JOHN F. PERONI DVM, MS, DACVS
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The President's Line Ruth-Anne Richter, BSc (Hon), DVM, MS - FAEP President Dear Fellow Equine Practitioners, As we quickly approach the FAEP event season, we’d like to remind you that early registration for the upcoming 13th Annual Promoting Excellence Symposium ends on September 20th. This exciting event, which takes place from October 19 to 22, 2017, at the luxurious Naples Grande Beach Resort in Naples, Florida, is filled with world-class continuing education and networking opportunities, set against the backdrop of this beautiful, oceanfront venue. From renowned equine speakers to veterinary partners, this year’s PES program is filled with many opportunities to learn, network, and relax among your peers and other industry experts. We are especially happy to welcome back both Dr. Sue Dyson from the United Kingdom, and Dr. Wayne McIlwraith from Colorado State University, to share their expertise in lameness management and therapies. This issue’s center spread provides detailed information about the symposium’s agenda, registration, room reservations and related activities we have planned for your time in Naples. We also invite you to join us for the 55th Annual Ocala Equine Conference on January 19 to 21, 2018, in Ocala, Florida. OEC 2018’s extensive laboratory session agenda offers our very popular ultrasound wet lab, as well as a wide range of in-depth lecture topics including: ophthalmology, lameness and rehabilitation, and reproduction. Both 2017 PES in Naples and OEC in January will offer the required continuing education for licensure in the State of Florida on the laws and rules governing the practice of veterinary medicine, and dispensing of legend drugs. More information about these two conferences also is available on our website at faep.net. Thank you for your continued support of PES and OEC, which provide more than 80 hours in CE opportunities annually. We hope you enjoy this issue of The Practitioner, which explores the latest updates on stem cell research and its applications, and offers in-depth discussions of common corneal and shoulder conditions found in the field. As always, we welcome your questions, comments and suggestions and encourage you to contact our FAEP council members or the FVMA staff.
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Review of the Main Shoulder Conditions in Horses J. M. DENOIX | DVM, Agrégé, PhD, HDR, Cert. ISELP, Assoc. ECVDI, DACVSMR Summary:
Because of the presence of strong muscles, proximal joints such as the shoulder are difficult to examine in the field with portable radiographic machines. Even when adequate radiographic images can be obtained, the use of ultrasonography may provide useful diagnostic information essential for an adequate management of shoulder conditions. The purpose of this paper is to present the main clinical conditions that can be diagnosed with this technique, used alone or in conjunction with other imaging modalities.
Imaging evaluation of the shoulder joint and proximal bicipital apparatus is considered in the following indications: • History of trauma; • Deformation of the point of the shoulder such as swelling or sharpening; • Specific atrophy of the shoulder or brachial muscles; • Pain to mobilization during protraction or retraction of the proximal forelimb; • Negative nerve blocks up to median and ulnar nerve analgesia; • Positive intraarticular scapulohumeral analgesia or intertubercular (bicipital) bursa analgesia; • Uptake in the proximal humerus or distal scapula on nuclear scintigraphic images. Shoulder conditions involve the bicipital apparatus, the periarticular muscles, and the scapulohumeral joint; different conditions being sometimes associated on the same horse.
Fig. 1a: Mediolateral radiographic projection of the shoulder joint of a three-year-old Thoroughbred filly showing an intraarticular fracture with distal displacement of the tuberculum supraglenoidalis (arrow). There is a marked bone lysis between the humeral head and the sulcus intertubercularis (arrowhead).
the stride for recent injury, improvement within few weeks with rest. In old injuries, the point of the shoulder remains enlarged and variable degrees of muscle atrophy and foot atrophy can be seen. - Diagnostic imaging: The diagnosis can easily be done on a mediolateral radiographic projection of the scapulohumeral joint (Fig. 1a). This procedure is not always easy on strong Bicipital apparatus: Two main conditions will be discussed: fractures of the horses with a portable machine. In all cases, the diagnosis tuberculum supraglenoidalis and dysplasia of the sulcus in- can be done with ultrasonography. On ultrasound images, a tertubercularis with medial luxation of the proximal tendon fracture of the tuberculum supraglenoidalis is characterized by an irregular gap in the hyperechogenic bone surface of of the biceps brachii. the neck of the scapula and a distal displacement of the bony fragment with collapsus of the dorsal scapulohumeral space 1- Fracture of the tuberculum supraglenoidalis - Cause: Traumatic injury: direct trauma (e.g. kicked by can be noted (Fig. 1b). In our cases, the fracture plane always another horse) or fall with hyperflexion of the shoulder and goes to the articular surface (glenoid cavity) of the scapula, usually passing through the glenoid incisura. Synovial fluid hyperextension of the elbow. - Clinical manifestation: Swelling of the point of the shoulder distension of the scapulohumeral joint and bicipital bursitis at physical examination and rapid development of shoulder is often associated with bony lesions. In chronic cases, a typimuscle atrophy; pain, reduction of extension of the proximal cal periarticular synovial lysis will develop cranially to the forelimb and weakness at retraction during mobilization; humeral head. Relaxation induced by the distal displacement acute lameness with typical reduction of the cranial part of of the proximal insertion of the biceps muscle induces hy6 The Practitioner Issue 2 • 2017
Fig. 1b: Sagittal ultrasound scan of the dorsal margin of the scapula and dorsal aspect of the scapulohumeral joint showing a fracture plane (arrow), distal displacement of the tuberculum supraglenoidalis and collapsus of the dorsal scapulohumeral space (arrowhead). Same filly as Fig.1a. 1- Distal scapula, 1a- neck of the scapula, 1b- tuberculum supraglenoidalis; 2- Sulcus intertubercularis of the humerus; 3- Proximal tendon of the biceps brachii (enlarged); 4- Supraspinatus muscle; 5- Omotransversarius muscle; 6- Skin.
2- Dysplasia of the sulcus intertubercularis with medial luxation of the proximal tendon of the biceps brachii This condition has been recently described in the literature (Coudry et al., 2005, Denoix et al., 2014). poechogenic areas and enlargement of the proximal tendon - Cause: Congenital abnormality. of this muscle. - Clinical manifestation: Typical sharpening of the point of - Prognosis: Fair to poor. In our cases, no horse was able to the shoulder with muscle atrophy of the cranial brachium. compete at a good level, regardless of treatment. All of them Weakness at retraction of the affected proximal forelimb. presented a residual lameness, with reduction of the cranial Reduction of the cranial phase of the stride at the walk and part of the stride sometimes compatible with pleasure riding trot. Grade 1 to 2 lameness in every situation (hard, soft, straight line, circles). or low-level show jumping. - Diagnostic imaging: A transverse ultrasound scan of the - Management and evolution: Different surgical techniques point on the shoulder shows an abnormal sulcus intertuberhave been suggested, including different types of fixation or cularis (SIT) presenting a narrow lateral groove, an irregular resection of the fragment. Conservative management leads tuberculum intermedium, and the absence of the medial to some degree of ankylosis of the scapulohumeral joint as groove because of the lack of minor tuberculum (Fig. 2a). the extension capacity of the joint is limited by the collapsus The proximal tendon of the biceps brachii (PTBB) is lacking at its dorsal aspect. Whatever the type of treatment, most of in the narrow lateral groove and is completely luxated at the the cases will show dystrophic mineralisation of the proximal medial aspect of the proximal humerus. On mediolateral tendon of the biceps brachii (PTBB) within a few months. radiographic projections, the SIT presents a single sulcus, and enthesophytes may be seen on the tuberculum supragleLong-standing cases may show ossification of this tendon. noidalis (Fig. 2b). A proximodistal skyline view of the point of the shoulder confirms the abnormal shape of the SIT. On nine horses diagnosed with this condition, three of them
Fig. 2a: Transverse ultrasonographic sections of the point of the shoulder in a dressage horse presenting dysplasia of the sulcus intertubercularis (SIT) with medial luxation of the proximal tendon of the biceps brachii (PTBB). The PTBB is luxated medially and presents an abnormal oval shape. There is a flattening and modelling of the minor tuberculum, modelling of the intermediate tuberculum, and narrowing of the lateral groove of the SIT. (Reproduced from Equine Veterinary Education, 2014, with permission.) 1- Minor tuberculum; 2- Intermediate tuberculum; 3- Major tuberculum; 4- Medial groove of the SIT (opened); 5- Lateral groove of the SIT; 6- Biceps brachii; 7- Brachiocephalicus muscle.
Fig. 2b: Radiographic findings of the shoulder in the same horse as Fig. 2a. Left shoulder, mediolateral projection. There is only one groove of the SIT and the abnormal distal margin of the minor tuberculum is superimposed with the proximal humerus; the soft tissues at the cranial aspect of the SIT look thinner than normal (arrowhead). Reproduced from Equine Veterinary Education, 2014, with permission. 1- Scapula; 1a- Tuberculum supraglenoidalis; 2- Humeral head; 3- Major tuberculum; 4- Intermediate tuberculum; 5- Minor tuberculum; 6- Lateral groove of the sulcus intertubercularis.
FLORIDA-ASSOCIATION -OF-EQUINE-PRACTITIONERS | The Practitionerâ€‚ 7
Fig. 3: Biomechanical deficits of the luxated proximal tendon of the biceps brachii muscle (PTBB) on the sagittal movements of the shoulder and elbow joints. Fig. 3A: Normal anatomical relationships of the flexed joints and biceps brachii muscle; Fig. 3B: Medial luxation of the PTBB resulting in a reduction of the capacity of the biceps brachii muscle to extend the scapulohumeral joint and to flex the humeroantebrachial joint. (Reproduced from Equine Veterinary Education, 2014, with permission.) 1- Tuberculum supraglenoidalis of the scapula; 2- Sulcus intertubercularis of the humerus; 3- Radius; 4- Biceps brachii.
were affected bilaterally (Denoix et al., 2014). - Prognosis: Fair; four horses were able to compete before the diagnosis, one continued at St-George level in dressage. - Management: There is no treatment for this condition. Conservative management include light shoes, shock waves at the medial aspect of the point of the shoulder, and building muscle compensation for improving forelimb protraction (Fig. 3).
When muscle atrophy of the infraspinatus and supraspinatus muscles develops, the muscle bodies become more echogenic than normal on ultrasonographic images; therefore the intramuscular tendons are less visible. Intramuscular tendonitis can be observed when muscle body atrophy is severe. With ultrasonography, monitoring of the recovery of the muscle fibers can be accurately documented.
3- Other conditions • Subchondral bone cyst-like lesion of the grooves of the sulcus intertubercularis (SIT) are responsible for lameness with a typical reduction of the cranial phase of the stride. Management includes medication of the intertubercular (bicipital) bursa, shock waves, and light shoes. In our cases, the prognosis has been fair-to-good for continuing an athletic career. • Traumatic injuries may be responsible for proximal bicipital tendinopathy. The PTBB is enlarged and present hypoechogenic lesions. A peritendinous swelling and a bicipital bursitis are also frequently observed. • Intertubercular (bicipital) bursitis can be found alone or secondary to bone lesions or tendonitis of the PTBB. When mild, the distension is localised laterally and distally to the major tuberculum. When the distension is severe, fluid makes protrusion cranially, between the PTBB and the brachiocephalicus muscle, and the mesotendon becomes visible in the sagittal plane (Fig. 4). When induced by a progressive lesion of the PTBB or SIT, the synovial fluid is usually anechogenic. Traumatic injuries such as fracture of the TSG are usually associated with marked distension of the intertubercular bursa containing fibrin clots. When the fluid is echogenic and accompanied with fibrin material without any anamnesis of trauma, a septic haematogenous bursitis must be considered. • Lesions involving the distal part of the bicipital apparatus (distal enthesopathy on the radius tuberosity) and desmopathy of the lacertus fibrosus have been observed at the dorsal aspect of the elbow in race and sport horses.
2- Infraspinatus tendinopathies/enthesopathies Traumatic fracture of the major tuberculum with tenosynovitis of the infraspinatus bursa was diagnosed after trauma at the lateral aspect of the shoulder. Intramuscular tendonitis of the infraspinatus muscle has been observed in horses affected with fracture of the tuberculum supraglenoidalis or suprascapular nerve paralysis with muscle body atrophy of the infraspinatus muscle body.
Conditions involving periarticular muscles
1- Suprascapular nerve paralysis This condition is not uncommon in young and adult horses.
Fig. 4: Transverse ultrasonographic section of the proximal tendon of the biceps brachii and sulcus intertubercularis in the same horse as Fig. 1. There is a severe distension of the intertubercular (bicipital) bursa with echogenic fluid containing fibrin clots (arrowheads). 1- Sulcus intertubercularis (intermediate tuberculum); 2- Proximal tendon of the biceps brachii; 3- Intertubercular (bicipital) bursa (distended); 4- Brachiocephalicus muscle.
8 The Practitioner Issue 2 • 2017
comparison with the opposite limb should always be done. Ultrasonographic findings include: synovial fluid distension at all aspects of the joint, chronic thickening of the synovial membrane, presence of free osteochondral fragments in the synovial cavity, cartilaginous defects as well as subchondral bone irregularities, and echogenic areas indicative of defects of ossification of the caudolateral aspect of the humeral head. Periarticular osteophytes of the glenoid cavity of the scapula may be seen. - Prognosis: Usually fair to poor. Some foals may improve surprisingly, to be able to achieve a sport career. Osteochondrodysplasia has been found in horses competing at medium level in show jumping. - Management: Arthroscopic removal of free osteochonFig. 5: Osteochondrodysplasia of the scapulohumeral joint in a six-yeardral fragments is indicated. In our opinion, curettage of the old Selle Français gelding used as a low-level show jumper; mediolateral radiographic projection. The humeral head is enlarged, less convex than non-ossified subchondral bone is contraindicated. As the normal, and presents an irregular profile with a caudal defect (arrow). shape of the articular surfaces is abnormal, most of our cases Its subchondral bone density is reduced and irregular (arrowhead). The without evidence of free osteochondral fragments were manglenoid cavity of the scapula is less concave than normal, enlarged, and aged conservatively. Affected adult horses will remain with presents cranial and caudal modelling (open arrowheads). shoulder and brachial muscles atrophy and a reduction of mobilization of the scapulohumeral joint at gaits. Adequate Conditions of the shoulder joint exercises to improve strength and proprioception of the Shoulder joint conditions are well described in the litera- shoulder muscles include combination of swimming, side ture. They include osteochondrosis (osteochondritis disse- gaits (such as shoulder in, half pass…), and trotting over cans and subchondral bone cysts of the humeral head and bars on the ground, trotting and cantering in deep surfaces. glenoid cavity of the scapula), scapulohumeral luxation, and osteoarthrosis. In this discussion, specific consideration will be given to osteochondrodysplasia of the shoulder joint and subchondral bone comminuted trauma of the glenoid cavity of the scapula. 1- Osteochondrodysplasia of the scapulohumeral joint Most of our cases affected with osteochondrosis of the scapulohumeral joint present moderate to severe change in the shape (dysplasia) of the humeral head and glenoid cavity of the scapula. - Cause: Developmental disease belonging to the juvenile osteochondral conditions (Denoix et al., 2013). - Clinical manifestation: Shoulder and brachial muscle atrophy; narrower foot on the affected side; more often unilateral disease in our cases. Pain and weakness at mobilization of the proximal forelimb. Mild to severe lameness depending on the extension and situation of the lesions affecting the subchondral bone. - Diagnostic imaging: Radiographic findings include: flattening of the humeral head with irregular profile of its articular surface, flattening and widening of the glenoid cavity with extensive modelling of its caudal margin, irregular thickness of the articular cartilage space, irregular subchondral bone density of the humeral head and/or glenoid cavity of the scapula, bone lysis induced by chronic synovitis between the humeral head, and sulcus intertubercularis (Fig. 5). As these changes are often asymmetrical or unilateral, WWW.FAEP.NET |
Fig. 6a: Mediolateral radiographic projection of the shoulder joint in a three-year-old racing Thoroughbred gelding showing a severe subchondral bone comminuted trauma of the glenoid cavity of the scapula. Periosteal bone proliferation can be seen on the caudal margin of the distal angle of the scapula (arrowheads). The subchondral bone of the glenoid cavity of the scapula presents several areas of decreased density (open arrowheads).
FLORIDA-ASSOCIATION -OF-EQUINE-PRACTITIONERS | The Practitioner 9
and Hippolia Foundation to the equine industry. Many thanks to the practitioners who contribute to improving knowledge of our profession; thanks to them for referring cases. Selected references
Fig. 6b: Sagittofrontal ultrasound scan of the scapulohumeral joint using a caudolateral approach. Same horse as Fig.6a. There is a marked periosteal bone proliferation over the neck and the distal angle of the scapula (arrowheads). There is also synovial fluid distension (arrow) and thickening of the capsule of the scapulohumeral joint. 1- Neck of the scapula; 2- Distal angle of the scapula; 3- Head of the humerus; 4- Synovial fluid of the scapulohumeral joint; 5- Articular capsule; 6- Triceps brachii muscle.
2- Subchondral bone comminuted trauma of the glenoid cavity of the scapula. This is one of the most severe conditions of the scapulohumeral joint. - Cause: Traumatic injury induced by a fall on the front end, seen mainly in sport and race horse in full activity. - Clinical manifestations: Mild to moderate enlargement of the point of the shoulder; severe pain at mobilization; acute and progressive pain while standing, and at the walk within several weeks; little and slow improvement within months. - Diagnostic imaging: The early diagnosis of this condition needs good-positioned and well-exposed radiographs. In the very acute stage, the first radiographs may be unremarkable. Within a few days and weeks, periosteal proliferation develops over the distal angle and neck of the scapula and subchondral bone lucencies show up in the glenoid cavity of the scapula (Fig. 6a). As ultrasonography is very sensitive to any alteration of the bone surface, an early diagnosis of periosteal reaction of the distal angle and neck of the scapula can be done with this technique (Fig. 6b). - Prognosis: Poor to continue a sport or racing career; fair to good for survival. - Management: Box rest; bisphosphonates to try reducing bone lysis. Acknowledgements Research on biomechanics and pathology of the equine locomotor system is supported by the Conseil Régional de Basse-Normandie and the European funds FEDER, and by the contributions of the Pôle de Compétitivité Filière Équine
Coudry V, Allen K, Denoix J-M: Congenital abnormalities of the bicipital apparatus in four adult horses. Equine Vet J 2005;35(3):272-275. Denoix J-M: Ultrasonographic examination in the diagnosis of joint disease. In: Joint Disease in the Horse, eds McIlwraith WC and Trotter GW, WB Saunders Co, Philadelphia, 1996;165-202. Denoix J-M, Audigié F: Imaging of the musculoskeletal system in horses. In: Equine Sport Medicine and Surgery, eds Hinchcliff KW, Kaneps AJ, Geor RJ, WB Saunders Co, Philadelphia, 2004;161-187. Denoix J.-M., Jeffcott L.-B., MacIlwraith C.-W. and Van Weeren P.-R. (2013) A review of terminology for equine juvenile osteochondral conditions (JOCC) based on anatomical and functional considerations. Veterinary Journal. DOI: 10.1016/j.tvjl.2013.03.038 Denoix J.-M. (2014) Dysplasia of the sulcus intertubercularis with medial luxation of the proximal tendon of the biceps brachii. Equine Vet Education, 26, 9, 473-476.
Jean-Marie Denoix, DVM, Agrégé, PhD, Cert. ISELP, Assoc. ECVDI, DACVSMR Founder and President of ISELP Founder and President of ISELP, France Dr. Jean-Marie Denoix of the CIRALE (Center of Imaging and Research on Equine Locomotor Affections) in Normandy, France, is considered the world’s foremost equine musculoskeletal system anatomist as well as a leading equine diagnostic ultrasonographer. Dr. Denoix is a founder and current president of ISELP and was also the 2006 recipient of the Schering Plough Equine Research Award from the World Equine Veterinary Association for outstanding applied research work in Equine Diagnostic Imaging. Jean-Marie has been the invited speaker at many international meetings in more than 30 countries around the world on topics related to clinical examination and imaging of equine locomotor problems.
10 The Practitioner Issue 2 • 2017
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Stem Cells: Latest Research and Applications – What/When Does It Work? JOHN F PERONI | DVM, MS, DACVS The use of Biological Therapies (BT) in equine practice has become commonplace for a number of reasons. Evidence would suggest that the addition of BT to the treatment protocol improves outcomes of soft tissue injuries such as tendonitis and desmitis. This field of research and clinical practice has rapidly gained momentum, in part, because equine veterinarians dealing with performance horses are regularly confronted with clients enquiring about using BT when dealing with a musculoskeletal injury. In fact, our clients have become acutely aware of these options, in part, because of intense media dissemination and industry pressure. As a result, equine practitioners should educate themselves and be aware of the details of employing BT, in order to effectively counsel their clients. A sharp contrast should be drawn between the concept of using biological material as a therapeutic and the commonly-used term of regenerative medicine. By definition, regenerative medicine is a branch of translational research in tissue engineering and molecular biology, which deals with the "process of replacing, engineering or regenerating human (animal) cells, tissues or organs to restore or establish normal function." Good examples of this are organ transplantation strategies and bone marrow replacement therapy in leukemia. In contrast, the products commonly available in veterinary practice are not expected to “regenerate” tissue de novo. Rather, they should be classified within a subset of regenerative medicine which include BT, aimed to modulate the healing response. This may be viewed as a matter of semantics; however, it has important implications when veterinarians confront the often
misguided expectation of their clients who expect the injured tendon to be “regenerated” and restored to function. In contrast to the relative abundance of therapeutic options, regenerative veterinary medicine is still lacking thorough scientific awareness and practical applicability. Although steps have been made in the understanding of the biology behind these approaches in equine practice, there are still many areas that deserve in-depth investigation. For example, no precise recommendations can be made regarding the selection of a specific biological approach regime for a given lesion. Prospective clinical trials are lacking that would help determine the appropriate timing of the treatment and the outcomes that the veterinarian should expect following the application of these modalities. Finally, regulatory bodies that would ensure that appropriate standards of care are followed when using BT, are still in their infancy in veterinary medicine and are only very recently beginning to set appropriate regulatory standards of manufacturing and administration to patients. These and many other issues remain unresolved in defining the role of BT in healing equine injuries. Nonetheless, ignoring the mounting and exciting evidence that BT may assist and improve the healing of common equine injuries would be a mistake. One of the first issues to confront when selecting BT is that of product selection. Faced with the many available options, the practitioner may be confused regarding what product to use and how to select the best regime or protocol for a given lesion or injury. BT can be distinguished by tissue of origin and mode of preparation.
Phases of injury healing
Continued on Page 21 12 The Practitioner Issue 2 • 2017
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Common and Uncommon Pathologies of the Digital Tendon Sheath and Fetlock Region
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Whole Horse Biomechanics and Kinesiology with an Emphasis on Equine Injury Prevention and Rehabilitation
Range of Motion of the Thoracolumbosacral Vertebral Column and Body Lean in Lame and Non-Lame Horses Dr. Dyson
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Exercise Physiology: The Importance of Warm-Up and Its Role in Injury Reduction Dr. McKenzie Current Topics in Human Physical Therapy and Rehabilitation and the Factors That Contribute to Injury Prevention and Decisions to Return to Sport After Injury Dr. Skeesik
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Soft Tissue Injuries of the Hock Dr. Dyson How Useful Is Nuclear Scintigraphy in the Diagnosis of Lameness or Poor Performance in Sports Horses? Dr. Dyson
The Development of Training Programs to Reduce Injury and of Specific Rehabilitation Protocols When Injury Occurs Dr. Schils
In part by Florida Laws & Rules Governing the Practice of Veterinary Medicine Mr. Bayó (Satisfies Florida’s 2-hour CE requirement for Florida Laws & Rules Governing the Practice of Veterinary Medicine)
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Current Status of Conventional Treatments for Traumatic Joint Disease Dr. McIlwraith
Dr. Schils, Dr. Butcher, Dr. McKenzie, Dr. Skeesick
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Continued from Page 12 BT can be obtained as autologous non-expanded material such as conditioned serum, platelet -rich plasma (PRP), bone marrow concentrate, and adipose-derived progenitor cells (stromal vascular fraction or SVF). The advantages of these products include rapid turn-around times, lack of immunogenic concerns and absence or minimal federal regulatory control. Alternatively, veterinarians have the option of obtaining autologous or allogeneic products that have been expanded in a laboratory setting. These include mesenchymal stem cells (MSCs) derived from adipose tissue, bone marrow, or neonatal tissues such as cord blood and cord tissue. Notably, these cell-rich products cannot be used as point of care treatments because they may take several weeks to expand. It is possible, however, to preserve these expanded products for multiple future allogeneic or autologous uses, if prepared applying rigorous laboratory protocols, which now require more stringent regulation as cellular preparations for medical use. The decision to select an autologous or allogeneic product depends on many factors including type of injury, age of donor and recipient, availability of a suitable donor, ability to collect tissue from the donor and the stage and status of the injury. Autologous treatments involve the horseâ€™s own biological derivative usually as a point of care treatment or after very minimal (less than 24h) laboratory manipulation. An exception to this would be the use of autologous MSCs, which are obtained from a tissue source of the injured horse and then processed by a laboratory over a period of several weeks and then re-infused to that same horse. This is the most common current scenario for MSC treatment in equine practice. Allogeneic treatments involve obtaining tissue from a donor horse and introducing the derived cell product into the injured recipient after a period of laboratory expansion. This is a relatively uncommon process in clinical practice, although there is an abundance of research to suggest that banking cells for transplantation is efficient by shortening the time required
to obtain a cellular product. Allogeneic stem cell transplantation needs to take into account the possibility of rejection and immune-recognition of the donor cells. The knowledge base regarding donor matching strategies in horses, as done in people with hemopoietic cell transplantation, have only minimally been explored in equine medicine.
Stromal Vascular Fraction
Proof that adult stem cells could be obtained from adipose tissue was initially demonstrated in 2001, when it was discovered that a typical adipose tissue aspirate contains large numbers of mesenchymal stem -like cells that could be induced to differentiate into adipogenic, chondrogenic, myogenic, and osteogenic lineages. Since then, many horses with soft tissue injuries and joint disease have been treated with a non-expanded adipose derived autologous preparation called stromal vascular fraction (SVF) This fat -derived mononuclear cell fraction contains MSCs, T regulatory cells (Treg), endothelial precursor cells, pre-adipocytes, and macrophages. When compared to bone marrow, adipose tissue is easier to obtain and has a proport ionally higher content of MSCs. Primary adipose tissue-derived cells such as those found in the SVF preparation are an attractive option because they require neither the two to three weeks necessary to expand MSCs nor the laboratory costs and expertise needed to avoid contamination during ex vivo expansion. Additionally, because SVF is considered a minimally manipulated autologous preparation, it is not subjected to FDA scrutiny or approval. Unfortunately, there are few studies that have critically addressed the clinical merit of SVF in veterinary medicine. Nonetheless, the abundant use of these products has supported the anecdotal notion that SVF may have a beneficial effect on the healing of tendon and ligament injuries without any ill effects seen at the site of injection or systemically. In a blinded placebo-controlled study, SVF was used to treat collagenase-induced tendonitis in horses. The results of that study showed an improvement in inflammatory cell infiltrate, collagen fiber uniformity, polarized collagen fiber crimping, overall tendon healing score, and collagen oligomeric matrix protein scores. Using a well- established model of osteoarthritis of the equine middle carpal joint, the efficacy of intra -articularly administered SVF and bone marrow derived MSCs was compared. Although no adverse effects were noted, that study was unable to demonstrate significant differences in clinical, biochemical, and histologic parameters between horses receiving placebo or treatment. The one exception in that study was that synovial fluid obtained from joints treated with bone marrow-derived MSCs had decreased production of the inflammatory cytokine PGE2 when compared to placebo treated joints.
Mesenchymal Stem Cells (MSCs)
Stem cells are progenitor cells classified into two main cell categories: embryonic and non-embryonic stem cells. Embryonic stem cells are derived from the inner cell mass of 5-6 day old blastocysts. The inner cell mass of the embryo develops into the epiblast and hypoblast (yolk sac). The epiblast will further develop into the three germ layers: endoderm, ectoderm, and mesoderm. Non embryonic stem cells have been derived from a variety of tissues including the most commonly employed tissues in clinical practice: Adipose, bone marrow and fetal tissues (umbilical cord blood and matrix). They are multipotent with the capabilities of
Aspirating SVF from sterile centrifuge vessel prior to injection
FLORIDA-ASSOCIATION -OF-EQUINE-PRACTITIONERS | The Practitionerâ€‚ 21
differentiating into the three connective tissue types that constitutes the ‘mesenchyme’ of the mesoderm (bone, adipose, and cartilage) and therefore are called mesenchymal stem cells. Bone marrow collection yields two components of marrow. The red marrow contains red blood cells, platelets, and white blood cells whereas the yellow marrow consists of fibroblasts, macrophages, adipocytes, osteoblasts, osteoclasts, and endothelial cells. Two lines of stem cells are present in the red bone marrow, the hematopoietic stem cell and the non-hematopoietic stem cell. The non-hematopoietic stem cell is contained within the bone marrow stromal cell population and is a multipotent, undifferentiated cell capable of tripotential (osteogenic, chondrogenic, adipogenic) differentiation. Bone marrow derived mesenchymal stem cells are derived from the mononuclear layer of bone marrow through adherence to a tissue culture plate or density gradient centrifugation followed by adherence. Although bone marrow has been the most popular source of MSCs in horses for research and clinical applications, harvesting adipose tissue, as a source of regenerative cells, is advocated because it is readily available in large quantities beneath the subcutaneous space and avoids pain and possible complications associated with bone marrow aspiration. Conflicting evidence exists regarding the comparison between adipose and bone marrow derived MSCs. Several studies have indicated little difference in the regenerative and differentiation potential, growth kinetics, cell senescence and efficiency of gene transduction of MSCs obtained from the two sources, whereas other research has supported the notion that fat has a superior yield of MSCs compared to bone marrow (2% vs 0.002%) that these cells demonstrate faster rates of proliferation and have a greater immunosuppressive ability. One possible explanation for the superior yield of MSCs from fat may be derived from recent evidence of a link between cultured MSCs and vascular density of the tissue of origin. MSCs were found to be associated with the vasculature, validating the use of adipose tissue as a source of mesenchymal progenitor cells for clinical purposes. Because MSCs can be isolated from various sources, expanded in culture, and then differentiated into many tissue types, they have become a prime resource for research into tissue healing. Not only can they contribute in part to architectural regeneration, but the cells have been shown to exhibit potent anti-inflammatory and immunomodulatory properties through cell-cell interactions and/or release of factors into the local environment. This will be discussed in detail in a later presentation.
Equine bone marrow is commonly obtained from the sternebrae and bone marrow-derived mesenchymal stem cells (BM-MSCs) have been expanded and characterized. An adequate sample of marrow can also be collected from the cancellous portion of other bones such as the crest of the ileum or the proximal humerus and tibia. When harvesting from the sternum, horses are restrained in stocks and sedated with a combination of detomidine hydrochloride (10 μg/kg) and butorphanol (20 μg/kg). After clipping the area of the midline of the sternum, the intersternebral spaces are identified by ultrasonography. Aseptic preparation and local
infiltration of anesthetic solution allows a stab incision to be made with a No. 15 scalpel blade on the sagittal plane of the sternum. A 10 gauge Jamshidi biopsy needle is introduced through the stab incision and advanced until it is in contact with the chosen sternebra. The needle is subsequently further advanced 3 or 4 cm with slow rotational motions. Syringes containing anticoagulant are attached to the needle and marrow aspiration is completed. Once transferred to the laboratory, the bone marrow aspirate is processed using several cell isolation techniques including direct adherence to a plastic tissue culture plate or density gradient centrifugation followed by adherence. With either one of these methods, MSCs are grown using specific essential growth media, typically containing fetal bovine serum, and “purified” from the mononuclear cell fraction of the marrow because of their selective adherence to the plastic. The MSC amplification process involves the regular removal of non-adherent cells to obtain a more homogeneous cell culture, a process that requires between 2 and 4 weeks, depending on the number of cells harvested and the desired final cell number. Of interest, is that when MSCs are seeded at low density, they demonstrate a classic spindle-like shape, but when near confluence, they begin to proliferate in layers and become flat with irregular cellular margins.
Ultrasound still image showing needle placement into a damaged superficial digital Flexor tendon.
MSCs in tendon and ligament injury
Tendon and ligament injuries in horses are a major cause of unsoundness in part because these injuries require prolonged healing times and are often cause of re-injury and further loss of soundness. Experimental studies have shown very promising results in tendon healing following MSC treatment, including improved tissue organization, composition and mechanics as compared to control subjects. There is convincing evidence that the therapeutic benefits of MSCs are due to their well-established anti -inflammatory and immunomodulatory capability, as well as to their postulated ability to modulate local humoral and cellular tissue repair mechanisms through direct and/or paracrine signaling. Despite these encouraging reports, equine MSC therapy in tendon injury is still lacking thorough scientific awareness and
22 The Practitioner Issue 2 • 2017
specific guidelines for practical applicability. Most importantly, progress made in understanding the biology behind regenerative approaches has not corresponded to an optimization of the delivery methods as they relate to clinical outcomes in horses with tendon lesions. Only a few reports are available that describe the long-term outcome of horses with naturally occurring tendonitis treated intralesionally with MSCs. One large study reviewed 168 horses with superficial digital flexor tendonitis treated with approximately 10x106 expanded BM-MSCs. That study found that the re-injury rate was significantly lower (13% and 18% for horses in full training) than had previously been reported for both race and sport horses. Furthermore, another report of 120 cases where BM-MSCs were used to treat tendonitis and desmitis reported that nearly 80% of horses with superficial digital flexor tendonitis and over 70% of horses with suspensory ligament desmitis had returned to their previous level of performance. In an additional clinical study, adipose-derived MSCs, grown in the presence of autologous platelet lysate, were inoculated into injured equine flexor tendons after the cells had been dispersed in activated platelet -rich plasma. A total of 14 out of 16 treated horses showed a functional recovery and were able to return to their normal activity.
MSCs in joint disease
Regeneration of articular cartilage presents unique challenges due to its lack of vascularity and innervation leading to an inefficient and slow intrinsic healing capacity. Often times, the healing tissue that is laid down consists of scar tissue or fibrocartilage that lacks the necessary mechanical properties to withstand the normal physiological strain of the joint resulting in further degeneration of the surrounding cartilage. The majority of studies evaluating the use of BM-MSCs in articular regeneration use 3-dimensional scaffolds and growth factors to chondrogenically differentiate MSCs and promote extracellular matrix formation. However, a large body of research has been dedicated to the implantation of undifferentiated BM -MSCs in suspension and relying on the synovial environment to influence the BM-MSCs toward the chondrocytic phenotype. Injection of BM-MSCs in suspension would be clinically superior to scaffold implantation because of the minimally invasive nature of injection rather than the arthrotomy that scaffold implantation would require. In addition to the ease of administration, reduced cost, reduced morbidity, and decreased recovery time are also important advantages. Furthermore, injections of BM-MSCs would theoretically treat the synovial environment as a whole rather than only the local environment of the articular cartilage defect. Unfortunately, little is known regarding the intra- articular behavior of MSCs in vivo. Many pertinent questions remain thus far unanswered regarding the differentiation of MSCs into the surrounding host cell tissue or the possible trophic effect they may have on the surrounding cells through release of growth factors or cytokines to produce extracellular matrix. The answers to all of these questions are likely to be complicated when one takes into account the various permutations of the osteoarthritic synovial environment. Regarding the intra-articular use of MSCs in horses, there is substantial contrast between the paucity of research and clinical WWW.FAEP.NET |
trials and the relatively numerous anecdotal reports of horses benefiting from injections of autologous MSCs. It is important to note that there are no controlled clinical trials that evaluate the use of MSCs in naturally acquired equine joint disease. In contrast, and as reviewed more in detail in the stromal vascular fraction section, the intra -articular injection of BM-MSCs, adipose derived stromal-vascular fraction, and a placebo was compared in an established experimental model of equine osteoarthritis. The only reported beneficial effect of BM-MSC treatment was a significant decrease in the PGE2 concentration in synovial fluid in both the sham operated and treated joints indicating a possible systemic effect of the BM-MSCs. Despite these results, a report was published on 162 equine cases treated with BM-MSCs from 6 different equine referral centers. A total of 97 horses with 101 treated lesions were available for follow-up. Three horses that were injected intra-articularly had adverse reactions, but improved and were able to return to work. Fifty -two of 61 (85%) horses with soft tissue injuries and 29/40 (73%) with orthopedic injuries were able to return to work with mean follow up time of 21 months. No significant association with outcome was found for age, sex, breed, discipline, or severity of lesion.
References are available upon request.
John F. Peroni, DVM, MS, DACVS Associate Professor, Large Animal Medicine University of Georgia College of Veterinary Medicine Dr. Peroni graduated from the College of Veterinary Medical Science at the University of Parma, in Italy in 1994. During Veterinary School he traveled to the U.S. and attended several institutions for prolonged periods of time, including: Delaware Equine Center, the University of Pennsylvania at New Bolton Center, Davis College of Veterinary Medicine, Rood and Riddle Equine Hospital and Chino Valley Equine Hospital. He completed a surgical residency and a MS degree from 1996 to 2000 at Michigan State University and was nominated Chairman of the North American Veterinary Regenerative Medicine Association (NAVRMA www.navrma.org). Peroniâ€™s research interests began with and still include the area of equine laminitis. The main focus of this interest has been the understanding of microvascular flow within the equine hoof capsule and the changes that occur to blood flow during the onset of laminitis. In the last five years, however, his research interest has shifted toward the development of animal models for the implementation of regenerative therapies aimed at the repair of musculoskeletal disorders, primarily fracture repair. Two additional areas that have occupied much of his recent interest and efforts have been the study of (i) the anti-inflammatory and immunomodulatory effects of mesenchymal stem cells and (ii) the interaction between delivered cellular therapies and the host environment.
FLORIDA-ASSOCIATION -OF-EQUINE-PRACTITIONERS | The Practitionerâ€‚ 23
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Tracks of My Tears: Corneal Conditions Seen in the Field ANN E. DWYER | DVM Introduction: Veterinarians are frequently called out to examine and treat horses with corneal disease. While a normal cornea is transparent and covered with smooth epithelium, abnormal findings may include disruption of the normally smooth ocular surface (ulceration), and/or opacification of the normally transparent corneal layers. Trauma is the most common cause of disruption of the equine ocular surface, but neoplasia, foreign bodies and some immune mediated conditions may also cause ulceration. Infection, mechanical damage and host proteinase activity are frequent complications that complicate healing. Clinicians presented with a horse that has ulcerative corneal disease should perform diagnostic tests to determine the etiology of the condition and prescribe treatment based on the analysis of those tests. Therapy must be administered several times a day and multiple recheck appointments may be required for successful resolution. Certain cases may require intense medical or surgical therapy that is best provided by referral institutions. An understanding of the differential diagnosis of ulcerative corneal disease, coupled with the results of clinical diagnostic tests and response to rational treatment, will dictate case management and optimize the chance for successful outcomes. Numerous factors may cause loss of corneal transparency. Opacity of the epithelium may result from neoplastic transformation of the surface or focal edema. Opacity of the stroma may reflect fibrosis, cellular infiltrate, foreign bodies, neoplasia or focal edema. Opacity of the deepest aspects of the cornea may reflect changes in the contour of Descemet’s membrane or edema accompanying endothelial dysfunction.
Key Clinical Diagnostic Points:
• Digital photography of corneal problems is essential for documenting disease and assessing response to therapy, especially on deep or melting ulcers. Many inexpensive digital cameras take very good images. • Head support will optimize the ocular exam and facilitate the collection of diagnostic samples. A simple “table” can be built with bales of hay or shavings. Horses with very painful eyes may require sedation and periocular nerve blocks for completion of the examination and diagnostic tests, as well as administration of stallside treatments or device insertion. • Fluorescein dye tests for integrity of the corneal epithelium. Rose bengal dye tests for the integrity of the mucin layer of the tear film. Both tests provide needed WWW.FAEP.NET |
Green fluorescein dye outlines the patch of epithelium that has been damaged in this superficial ulcer.
diagnostic information. Rose bengal can be irritating and should be diluted by tearing off a piece of dye strip and mixing it with saline in the barrel of a small syringe. The dyed saline can be dripped onto the ocular surface. • A Schirmer tear test (STT) should be performed on all eyes that appear to have dull or dry corneal epithelium. Normal equine corneas have an abundant tear film that will soak over 15mm of the STT strip in less than 30 seconds. • Cytologic analysis is beneficial for all but the most superficial corneal erosions. Collection of corneal cells for cytology should be done with a Kimura spatula or the blunt end of a sterile scalpel blade—samples should be spread on two to three slides, which are then stained with Diff-Quik® and gram stains. Cytology should ask three questions: 1. Are inflammatory cells present? If so, what kindPMNs, bands, eosinophils, mast cells? 2. Are infectious agents (bacteria or fungi) present or absent? If so, what are the staining and morphologic features? 3. Are there any foreign bodies or other non-cellular elements present in the sample? (Plant material, crystals of calcium, parasites, etc.) • Culture is indicated for deep or persistent ulcers in addition to standard cytologic analysis. Culture samples should be obtained before cytologic samples and debridement, and may be plated directly or transported in broth which is then plated out if it becomes turbid with microbe growth. • Vascularization of the cornea occurs in many disease processes. Superficial vessels are individual, long, branching vessels that lie within the epithelium or
FLORIDA-ASSOCIATION -OF-EQUINE-PRACTITIONERS | The Practitioner 25
anterior stroma. Deeper, mid-stromal vessels are short and straight and present as a brush border along a portion of the limbus or along the entire circumference. Very deep vessels that rest on the Descemet’s membrane interface are individual, long, branching vessels. • Desmetoceles (or very deep ulcers) will show a craterlike contour and lack of fluorescein stain uptake centrally. Eyes with desmetoceles are at risk for perforation: all manipulation should be done with caution.
Desmetocele on this blind phthisical eye is seen as a rim of dark cornea surrounding stromal tissue that stains green.
deeper layers. • The next layer of the cornea is the stroma, which is the thickest layer, comprising over 90 percent of the corneal thickness. Stroma is composed of Type I collagen fibrils that are arranged in a parallel lamellar lattice pattern. Disruption of the lattice causes opacity. Healing of stromal defects involves a balance of resorptive remodeling (facilitated by the proteinases that are released from bacteria, corneal cells and infiltrating PMNs), and restorative repair where fibroblasts lay down collagen to fill in the defect. Successful healing of defects is followed by several months of collagen remodeling that may return the tissue to a degree of its original transparency. In deep lesions, or lesions where healing is delayed, the collagen is laid down in a thick, random fashion, making an opaque scar. In severe cases, remodeling by proteinase activity is excessive, resulting in keratomalacia (melting) or perforation. • The next deepest layer of tissue is a thin basement membrane called Descemet’s membrane. • The final layer of the cornea is a very thin monolayer of cells, the endothelium. This layer of cells has a sodium and potassium-activated ATP-ase dependent electrolyte pump that constantly works to keep the corneal stroma relatively dehydrated. Disruption of the normal pump activity results in edema of the endothelium and overlying stroma that can be permanent.
• Host proteinases play an important role in the pathogenesis of corneal ulcers. Elevated levels of Common problems of the cornea include: matrix metalloproteinases (MMPs) and serine proA. Superficial corneal erosions: Erosions are defects teinases such as neutrophil elastase (NE) are present that do not break into the stroma. If these do not get in the pre-corneal tear film of eyes with corneal ulcers. infected, they heal quickly without visible scars. Topical While some tissue lysis and remodeling is essential for mydriasis and antibiotic therapy is indicated. corneal healing, excessive proteinase activity can lead to keratomalacia or melting. Autologous serum is an B. Superficial keratitis: May present as punctate areas effective treatment that contains high levels of growth of stain uptake, as focal vascularization, as pigment deposifactors and anti-proteinases. Some clinicians also use tion or as focal superficial opacities. Punctate keratitis other anti-proteinase therapies like 1% EDTA or 5-10 may have a herpetic, fungal or an idiopathic etiology. The percent acetylcysteine. lesions may be painful or comfortable. Epithelium shows fluorescein stain uptake in a dot-like pattern that is scatKey Etiologic and Pathophysiologic Points: tered over the corneal surface. A trial of topical idoxyuriThe cornea: This consists of several layers of tissue with dine may improve the condition. Topical NSAIDS, especially an average total thickness of about 1 mm; thinnest in 0.1 percent diclofenac, may be very helpful. Some forms the center. of keratitis will respond to topical NSAIDs or antivirals, • The outer layer is a relatively impermeable epithelium, while others respond to topical antibiotics. Cases that do which is richly innervated and very thin (0.14 mm and not respond to simple treatment should be assessed for six to eight cell layers thick), with an underlying basefungal elements. ment membrane. The epithelium is covered by the precorneal tear film that some anatomists consider a C. Ulcerative keratitis: Ulcers are defects that extend “fifth layer” of the cornea. through the corneal epithelial layers and basement mem Healing of non-infected superficial defects in brane into the stroma. Healing of these defects is a balancthe epithelium usually is rapid and occurs initially ing act: ideally, tear film proteinases remodel the stromal via the “sliding leapfrog” motion of adjacent cells defect and native fibroblasts restore stromal integrity. Bacto cover the wound bed, and then later by basal terial or fungal infections as well as various host factors cell mitosis. may tip the balance towards excessive resorption, result Healing of deeper defects where the basement ing in melting of stromal collagen or even perforation of membrane is disrupted involves re-epithelialization, the globe. Ulcers are very painful and are accompanied followed by a longer period of remodeling of the by secondary uveitis, so the syndrome is complicated by 26 The Practitioner Issue 2 • 2017
progress rapidly and incite extensive collagenolysis. Melting ulcers are expensive and time consuming as treatment must be immediate and aggressive. Outcomes may be optimized if the horse is sent to a referral center where anti-infective and antiproteinase therapy (serum, EDTA, acetylcysteine, ilomastat) is administered every one to two hours around the clock.
Cytology on this corneal scraping demonstrates bacterial infection (large cocci in chains) as well as a neutrophilic infiltrate.
patient objection to topical therapy. Adjunctive surgical therapy may involve debridement or keratectomy. Complex cases may need conjunctival grafts, amniotic membrane grafts, or tarsorrhaphy, and therefore may be best handled as referral cases. Very serious cases may require corneal transplantation by penetrating keratoplasty (PK), penetrating lamellar keratoplasty (PLK), or deep anterior lamellar keratoplasty (DALK). Ulcers with bacterial infection can be diagnosed by cytology. Initial therapy choices are dictated by the type of bacteria seen on slides, and later may be adjusted according to clinical response and results of lesion culture and sensitivity. Therapy is intense, usually four to six times per day. Antibiotics are combined with mydriatics and topical antiproteinases. Systemic NSAIDs help control pain. Subconjunctival injection may be used to supplement topical therapy. Treatment of cooperative patients without obvious keratomalacia may be via ointments administered at home, and resolution may be straightforward. Treatment of fractious patients, or patients with deep defects may be via liquid medications administered through an SPL tube at home or at a referral hospital. Frequent monitoring will be necessary until it is clear that healing is occurring. The most common antibiotic drugs used on bacterial keratitis are fluoroquinolones (ciprofloxacin, ofloxacin, and moxifloxacin), chloramphenicol, cephazolin, tobramycin, gentamicin, and amikacin. The application of atropine should be to effect. Topical antiproteinase therapy using serum application is routine and may include a combination of other MMP inhibitors such as EDTA or acetylcysteine. Debridement should be judicious, but may need to be repeated weekly. Melting ulcers: In some cases an ulcer may be sterile, but host proteinase activity is severe enough to cause corneal “melting” that threatens globe integrity. In other cases, corneal melting may be related to bacterial infections, particularly those caused by beta hemolytic Streptococcus spp or Pseudomonas aeroginosa, as both of these infections WWW.FAEP.NET |
Cytology on this corneal scraping demonstrates fungal infection. Hyphae are seen as long, branching septate structures with parallel walls
Fungal keratitis: Ulcers with fungal invasion are common in humid southern climates. While less common in northern or desert regions, reports of fungal keratitis have increased in these areas in recent years. The presence of septate branching hyphae on a corneal cytology sample is diagnostic, but sequential cytology samples may be needed to discover fungal elements, and treatment is often begun if the index of suspicion for fungus is high. Antifungal sensitivities vary from one region to the next, so it is helpful to know what medications have been most effective in a specific geographic area. Fungal infections are very painful and the host inflammatory reaction is extreme. Fungi have the ability to tunnel down to Descemet’s membrane where topical drug activity may be limited. Prognosis is always guarded; early surgical intervention may be necessary for resolution. Surgical treatment involves keratectomy with conjunctival grafting or corneal transplantation. Topical antifungal therapy may involve the use of voriconazole, miconazole, natamycin, itraconazole, or silver sulfadiazine. Systemic antifungal therapy may be instituted using fluconazole or itraconazole. Non-healing indolent ulcers: Shallow ulcer defects may fail to heal in some older horses if the epithelium does not generate a normal basement membrane for secure adherence. These cases may be helped by debridement with a swab or blunt blade, or temporary tarsorrhaphy. If a non-infected ulcer does not heal in two weeks, diamond
FLORIDA-ASSOCIATION -OF-EQUINE-PRACTITIONERS | The Practitioner 27
burr debridement with an AlgerBrush II® or a superficial linear keratotomy may stimulate healing. Both forms of debridement create small defects in the superficial stroma, providing a lattice for adherence of new epithelial cells. It is important to perform cytology on any non-healing lesion to rule out infection before attempting one of these procedures.
Squamous cell carcinoma of the cornea. Lesion started as small raised area on the limbus and has infiltrated the perilimbal region.
D. Corneal tumors: Squamous cell carcinoma is the most common tumor of the corneal surface, especially in Appaloosa, Paint or draft breeds. The limbus is a common area of tumor. Other tumors include: melanoma (most common in gray horses), hemangioma, hemangiosarcoma, mast cell tumors and lymphosarcoma. Prompt referral for surgery, with added adjunctive therapy like beta irradiation, cryotherapy, photodynamic therapy or laser ablation is advised. Enucleation may be the best treatment for some cases. E. Corneal foreign bodies: Horses occasionally present with foreign bodies embedded in the stroma or epithelium. Superficial foreign bodies can often be “wicked” out with a sterile cotton swab, flushed out with a pressure lavage of saline pushed through a broken-off hub of a 25G needle, or “scooped out” by careful undermining with the bevel of a 20G needle or small 2 mm biopsy punch. The remaining ulcer should be swabbed and lavaged with 2% povidone iodine/saline solution and treated medically. Very deep or penetrating foreign bodies must be referred for surgery and supportive care. F. Eosinophilic keratoconjunctivitis (EK): EK is a condition of probable immune-mediated etiology in which a horse presents with limbal granulation tissue, chemosis, mucoid discharge, and/or limbal, axial or paraxial corneal ulcers that may have a rubbery texture, or may have white or yellow raised plaques with gritty chalk-like material embedded along the margins. Cytology will reveal an abundance of intact eosinophils and loose eosinophilic granules, and also may show scattered mast cells. Therapy includes
debridement or debulking of the plaques (possibly using an AlgerBrush II® battery-powered tool), atropine, antibiotics, topical mast cell inhibitors, and topical steroids. Note that this is the one condition where steroids are sometimes used in the face of ulcerated epithelium—this therapy is appropriate, in certain cases, but must be monitored closely. Many clinicians have found that a tapering dose of systemic steroids in addition to systemic NSAIDs is beneficial. Recent reports on the addition of a systemic oral human antihistamine (ceterizine or Zyrtec®, 0.4mg/kg PO BID) have been encouraging. G. Burdock pappus bristle keratopathy: Horses that live in regions where burdock is a common pasture weed often present in the fall with tiny pappus bristles embedded in the cornea or nictitans. Large, burr-like burdock thistles are commonly found tangled in the tail and mane. Affected horses present with signs of corneal ulceration or erosion, particularly in the medial canthus under the nictitans. The tiny burdock bristles are not visible in field conditions, but in chronic cases there may be vessel patterns on the nictitans conjunctiva or on the cornea that “point” to their location. All suspect areas should be debrided. Nictitans debridement is facilitated by everting the whole membrane with a small towel clamp or hemostat, and gently scraping the conjunctiva with the serrated edge of a sterile hemostat until it bleeds. Resolution is prompt if the bristles have been completely removed. Treatment involves topical atropine and antibiotics, plus systemic NSAIDs. H. Calcific band keratopathy: Some cases of chronic uveitis are complicated by mineralization of the cornea with deposits of calcium. This “calcific band keratopathy” may be related to repeated topical steroid application. Gritty plaques of calcium are deposited in the corneal epithelium and upper stroma in the central axial region where the lid aperture exposes a central band of corneal tissue. Often the plaques protrude through the epithelium and are associated with erosions and ulceration. Removal of the irritating deposits may require superficial keratectomy and/or chelation with topical 1 or 2 percent EDTA. Recurrence is common. I. Non-ulcerative corneal disease--Stromal abscesses: One of the most serious corneal conditions that presents without ulceration of the epithelium is a stromal abscess (SA). Stromal abscesses are seen as single or multiple non-staining focal fluffy yellow to tan-white densities, which reflect microabscesses located deep within the corneal stroma. These focal lesions are very painful and are usually accompanied by an intense ingrowth of deep vessels from the closest region of the limbus. Many of these lesions have been found to contain fungal hyphae, so aggressive antifungal therapy is advised in addition to antibacterial and mydriatic treatment, and systemic NSAIDs. Superficial SAs may respond to intense topical therapy, but deeper SAs may be completely refractive to medical therapy or debridement, and many patients with SAs end up requiring enucleation if they are not treated surgically at a specialty hospital.
28 The Practitioner Issue 2 • 2017
A deep stromal abscess is seen as a yellow density buried within the stroma at 8:00. The lesion is several weeks old and is accompanied by a marked vascular reaction and hypopyon.
Surgical options for SAs include several different types of corneal transplantation procedures including penetrating keratoplasty (PK), penetrating lamellar keratoplasty (PLK), or deep anterior lamellar keratoplasty (DALK). Outcomes are improved if referral is made is early in the course of disease, and if the referral institution has broad experience in treating equine patients. Recently, improved outcomes have been reported when stromal abscesses are treated with intrastromal injection of voriconazole. J. Non-ulcerative corneal disease--“Immune-mediated keratitis” (IMMK): Less serious, but still problematic transparency changes are seen in the group of conditions known as the immune-mediated keratopathies. This group of diseases is poorly understood. The variants termed IMMK demonstrate focal or diffuse regions of opacity limited to the stroma or endothelium that retain an intact epithelium and thus do not take up ophthalmic stains. Many of these conditions are recurrent. Confocal microscopy of opaque regions usually reveals an infiltrate of lymphocytes and plasma cells within the affected stroma and an absence of infectious elements. Although some cases are bilateral, most are unilateral and a careful history may reveal a previous episode of trauma in the affected eye. The observed opacity may reflect a cellular immune reaction to antigens expressed within the stroma. The intensity and regional pattern of observed opacification often varies over time. Areas that were previously opaque may clear only to have other geographical regions of the cornea lose transparency. Often there is vascularization of the opaque areas that will also change pattern over time. Pain is variable—some horses never exhibit pain while others may have episodes of severe pain that accompany increasing opacity.
Key Therapeutic Points:
• Debridement of the cornea should be routinely performed in all but the most superficial ulcerative conditions. It can be as simple as swabbing the lesion with a sterile cotton swab, or as involved as actually cutting away some cornea with a #15 or #63 blade. Opinions vary on intervals between debridement sessions, but reassessment at weekly intervals WWW.FAEP.NET |
is common. • The Algerbrush II® is an inexpensive, battery-powered tool that is being used with increasing frequency by equine ophthalmologists for light debridement of selected corneal lesions. It works like a miniature Dremel® tool when it is fitted with a round, diamond pterygium burr. Evidence is growing for the best cases to select for burring, but success has been reported in the treatment of indolent ulcers and eosinophilic keratitis. More information on the Algerbrush can be found at: http://www.algercompany.com/brush/ • Subconjunctival injections of antibiotic or antifungal drugs are occasionally used as adjunct topical ulcer therapy. Injection administration is safest if the horse’s head is supported by a table made of bales, and the handler, who is standing on the contralateral side of the horse, uses the ear of the horse to tilt the top of the head away from the clinician, thereby exposing target sclera. • Application of topical anesthetic via sterile cotton swab and a small volume squirted onto the target surface with a small syringe fitted with the hub of a broken-off, 25G needle will facilitate subconjunctival injections and debridement or inspection of the nictitans. • Lavage catheters (SPL tubes) are useful ways to deliver medication to the surface of the eye, especially in fractious horses. Mila International (http://milainternational.com) supplies catheters in two sizes that have swedged-on tubing that is very easy to insert. • Management of IMMK cases requires lifelong monitoring. Treatment may involves systemic NSAIDs and topical antiinflammatory therapy for horses that present with pain or increasing areas of opacity. Some horses will respond well to topical NSAIDs (diclofenac); others may be helped by
Ann E. Dwyer, DVM Co-Owner, Genesee Valley Equine Scottsville, New York Dr. Ann Dwyer is co-owner of the Genesee Valley Equine Clinic, PLLC, and has worked at the practice since graduating from Cornell in 1983. She has a special interest in equine ophthalmology and practice management and has lectured widely on these topics. Dr. Dwyer’s field research has focused on equine ophthalmology, particularly uveitis, leptospirosis, and blindness in horses. As a result, she has authored several book chapters on field ophthalmology for ambulatory clinicians as well as blindness. In 2011, Dr. Dwyer was named an honorary member of the American College of Veterinary Ophthalmology. She holds an appointment as a clinical associate at the Flaum Eye Institute (the ophthalmology arm of the medical school at the University of Rochester). Dr. Dwyer was a member of the board of directors at the AAEP from 2006 through 2008; she then became an officer of the AAEP in 2011, serving as VP that year, as president-elect in 2012, and as president in 2013. Additionally, she served as the program chair for the AAEP 2012 Anaheim convention and organized the first Focus on Equine Ophthalmology meeting that the AAEP staged in 2009.
FLORIDA-ASSOCIATION -OF-EQUINE-PRACTITIONERS | The Practitioner 29
topical immunomodulators (compounded cyclosporine (2 percent) or tacrolimus). Topical steroids (prednisolone acetate or dexamethasone) help some cases, but the use of these agents requires close monitoring, as the presence of an undetected infectious agent deep in the stroma can never be fully ruled out, and topical steroids can exacerbate a flare up of infectious keratitis.
Key Prognostic Points:
• Corneal ulcers can be simple traumas that resolve uneventfully or progressive problems that are among the most complicated and expensive that horses experience. Often, prompt assessment and aggressive therapy wards off disaster. Practitioners should commit to seeing painful eyes on the date of occurrence and should perform appropriate diagnostic tests to make rational treatment choices. • Very painful, large, deep or melting ulcers may best be handled at referral institutions. Early referral and consultation may result in the best outcome. • The prognosis for fungal keratitis is guarded: successful resolution often requires surgical intervention or delicate injection. Referral is encouraged. • IMMK cases rarely resolve, but also rarely advance to the point where they cannot be managed. Observed corneal opacities will ebb and flow. Owners should be coached that these horses require lifelong monitoring, and may require intense treatment if the eye is very painful or opaque.
References/Suggested Reading Barnett, KC, et al. Color Atlas and Text of Equine Ophthalmology, 2nd edition. London, Mosby-Wolfe, 2004. Brooks, D. Ophthalmology for the Equine Practitioner. Jackson, Wyoming. Teton NewMedia, 2008. Brooks, D. Equine ophthalmology. Gelatt, KN (ed.) Veterinary Ophthalmology, 5th edition Philadelphia, Lea & Febiger, 2013. Cutler, T. (ed.) Veterinary Clinics of North America. Equine Practice 20 (2), p. 417-428. Updates in Equine Ophthalmology. Philadelphia, Saunders, 2004. Dwyer, AE. How to take digital photographs of equine eyes in practice. p. 52-92. Proceedings Am. Assoc. Equine Practice; 56, 2010. Dwyer, AE. Practical field ophthalmology. p. 72-111. Gilger, B, (ed.) Equine Ophthalmology, 3rd ed. Ames, Wiley Blackwell, 2017. Dwyer, AE. Ophthalmology in equine ambulatory practice. p. 155-174. Ramey, D. and Baus, M. (ed.) Ambulatory Practice. Veterinary Clinics of North America, Equine Practice, 26, 1. Philadelphia, Elsevier, 2012. Dwyer, AE. How to insert and manage a subpalpebral lavage tube. In Proceedings Am. Assoc. Equine Practice; 59: 164-173, 2013. Gilger, B, (ed.) Equine Ophthalmology, 2nd ed. Philadelphia, Elsevier, 2011. (Note: 3rd edition of this text is in press by Wiley Blackwell, due out in 2017). Lavach, D. Large Animal Ophthalmology. St. Louis, Mosby, 1990.
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Issue 2 • 2017
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A publication by the Florida Association of Equine Practitioners, an Equine-Exclusive Division of the Florida Veterinary Medical Association...