Practitioner Issue 3, 2013 by FVMA

The Practitioner Published by the Florida Association of Equine Practitioners, an Equine-Exclusive Division of the Florida Veterinary Medical Association Issue 3 • 2013

DEVELOPING TREATMENT STRATEGIES FOR PALMAR FOOT PAIN Pg. 6 - Tracy A. Turner, DVM, MS, Dipl. ACVS

EQUINE DENTAL RADIOLOGY Pg. 11 - Jack Easley, DVM, MS, DABVP (Equine)

The Value of Quality

Foot Radiographs

and the Impact they have on

Balanced Farriery Pg. 26 Randy B. Eggleston, DVM, DACVS

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The President's - at the three quarter pole: OFF AND RUNNING WITH THE FAEP . . .

–

Anne L. Moretta, VMD, MS - FAEP President

t is with great pleasure that I invite you to attend one or both of our fall continuing education programs. I am very excited about the exceptional and diverse programs the FAEP council is presenting.

The 9th Annual Promoting Excellence Symposium will be held from October 17th – 20th at the legendary Boca Raton Resort & Club, a Waldorf Astoria property in Boca Raton, Florida. This is a fun, family oriented destination that offers world-class old-world elegance with modern luxury amenities. It has been a destination in itself on Florida’s east coast for more than 80 years. This year’s symposium integrates a ‘whole horse’ approach with its equine sports medicine and rehabilitation topics. The symposium schedule features an in-depth ophthalmology program, an in-depth master class on the neck and back, and topics in performance horse medicine, cardiology, neurology, surgery, lameness, and imaging. Our popular rehabilitation tract offers current topics on the biomechanics of injury and case studies of rehabilitation protocols from ‘start to finish’ to take home. Our dynamic exhibitor marketplace will showcase the very latest in products and services available to the equine veterinary profession. The 51st Annual Ocala Equine Conference, ‘For Practitioners by Practitioners’, offers outstanding equine CE on November 15th – 17th, 2013 in Ocala, Florida. Dr. Scott Palmer, past president of the American Association of Equine Practitioners, is our distinguished keynote speaker who will address the important topic of ‘Medication Issues in Racing’. Our educational program includes topics in alternative medicine, dentistry, dermatology, infectious disease, lameness and lower respiratory disease. The Ocala conference offers two full-day wet labs focusing on ‘Advanced Dentistry’ and ‘Field Procedures’ for practitioners who want to sharpen their skills and enhance their potential for increased revenue. This issue of The Practitioner contains new and relevant articles for your practice. I keep my back copies of The Practitioner in my truck for quick reference on the road! The center spread of this issue of The Practitioner features the speakers, topics, schedule and registration details for the Ocala conference. We have launched conference websites to provide you with everything you need to know about The 9th Annual Promoting Excellence Symposium and The 51st Annual Ocala Equine Conference. For information on PES, please visit: http://eventscribe.com/2013/pes/. For information on Ocala please go to: http://eventscribe.com/2013/ocala/. I look forward to personally welcoming you to our fall continuing education meetings. We want to promote excellence in our profession by offering you smaller, more cohesive, and interactive colleague-to-colleague experiences. I encourage you to register today!

Resolve To Be Involved In 2013/2014. Please Join our FAEP Community. There are many talented veterinarians in our FAEP community. We invite you to join us as committee members for our educational meetings and our publication, The Practitioner. Participation and feedback from our membership and attendees is a crucial part of what makes our programs successful.

• EXECUTIVE COUNCIL • •

•

Suzan C. Oakley, DVM, Diplomate ABVP (Equine)

Gregory D. BonenClark, DVM, Diplomate ACVS

FAEP Council President-Elect FAEP Council Past President

oakleyequine@gmail.com gbonenclark@fevaocala.com

Mr. Philip J. Hinkle

Executive Director phinkle@fvma.org

Amanda M. House, DVM, Diplomate ACVIM housea@ufl.edu

Liane D. Puccia, DVM pucciavet@aol.com

Corey Miller, Jacqueline S. Shellow, DVM, MS, Diplomate ACT DVM, MS Representative to the FAEP Council Vice President cmiller@emcocala.com FVMA Executive Board rrichter@surgi-carecenter.com cmiller@emcocala.com Ruth-Anne Richter, BSc (Hon), DVM, MS

The Practitioner is an official publication of the Florida Association of Equine Practitioners, an Equine-Exclusive Division of the Florida Veterinary Medical Association.

4 The Practitioner

Issue 3 • 2013

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DEVELOPING TREATMENT STRATEGIES FOR PALMAR FOOT PAIN by Tracy A. Turner, DVM, MS, Dipl. ACVS

Introduction:

The palmar digital nerve block desensitizes the palmar onethird to one-half of the foot.1-3 Lamenesses in this region account for more than one-third of all chronic lamenesses in the horse. It must be understood that a palmar digital nerve block simply localizes the source of the pain the horse senses to the back of the foot. It is important to identify as specifically as one can, the pathological and clinical findings. This in turn will help the clinician make the best assessment of the problem, and recommend the most specific treatment. Diagnosis:

The first step in developing a logical approach to the treatment of palmar hoof pain is an accurate assessment of the pain and careful evaluation of hoof structures that may predispose to, or cause the pain. Four diagnostic tests should be performed: hoof tester examination, distal limb flexion, hoof extension wedge test, and palmar hoof wedge test.4 A positive response to any of these tests is important but a negative response is equivocal and does not rule out any problem. Hoof tester examination should begin with systematic evaluation of the sole and then to the distal sesamoid region which includes the collateral sulci to opposite hoof wall, central sulcus to toe, and across the heels. A positive response should be repeatable, and in the distal sesamoid region the pain response should be uniform over those areas and must be evaluated in relation to examination of the remaining foot. That is, a positive response in the heels and quarters of the sole would also be expected to cause a positive response across the distal sesamoid region in the same area of the foot. Percussion utilizing a small hammer can also provide important information regarding pain in the hoof wall or sole. Distal limb flexion test may exacerbate lameness if any of the three distal joints of the leg are affected by synovitis or

Frog wedge test - the single best test for deep pain in the foot 6 The Practitioner

osteoarthritis.1,4 A positive response could also be expected by any condition that causes induration of the tissues of the foot. This has been shown to be positive in over 95% of horses with palmar foot pain.4 The hoof extension test is performed by elevating the toe with a block, holding the opposite limb, and trotting the horse away after 60 seconds. The palmar hoof wedge test is performed by placing the block under the palmar two-thirds of the frog and forcing the horse to stand on that foot. The test can be further modified so that the wedge can be placed under either heel to determine if the pressure there causes exacerbation of the lameness. As part of the overall evaluation of these horses an objective assessment of hoof balance is important.3 Eleven measurements are made of each foot. The horse's weight is determined with a weight tape or scale. Seven measurements are made of the hoof length with a tape measure: medial and lateral heel lengths; medial and lateral quarter lengths, dorsomedial and dorsolateral toe lengths, and sagittal toe length. These measurements are recorded on a graph to illustrate the general shape of the foot. In addition, the frog's length and width are measured at their longest and widest points. The hoof circumference immediately below the coronary band and the hoof angle (using a hoof gauge) are also measured. From these measurements, two additional measurements can be calculated: the frog ratio (frog width divided by length) and the body size to hoof area (horse's weight (pounds) X 12.56 / square of the hoof wall circumference(C) (inches)). A dorsopalmar (plantar) and a lateral radiograph of the hoof can also be used to determine valuable information about hoof balance.3 The horse must be standing with the metacarpus (tarsus) perpendicular to the ground, which can most easily be determined by either the use of a level placed against the cannon bone or the use of a weighted string to align the leg. The radiographic beam should be horizontal and centered on the hoof. Resting the horse's foot on a block to raise the hoof off the ground facilitates these exposures (the opposite limb should be similarly elevated). Typically, all these before-mentioned lamenesses will be improved by at least 90% after perineural anesthesia of the palmar digital nerves but it does not help differentiate these lamenesses.1 Anesthesia of the distal interphalangeal (DIP) joint or the podotrochlear bursa are additional procedures that provide information about palmar hoof pain.4 In a study reported by Turner, in 95% of the horses examined using DIP and bursa anesthesia, significant new information about the pain the horse exhibited was realized. The pain relief by anesthesia of any of these three regions has been shown to overlap. The DIP joint and podotrochlear bursa do not communicate, and yet the results of injecting anesthetic into these synovial cavities are similar. Both cavities have in common the navicular bone, the impar ligament, and the collateral sesamoidean ligament (proximal suspensory ligament of the navicular bone). The neuroreceptors for the navicular bone are in those 2 ligaments and they can be anesthetized from either synovial cavity.3 Further, Bowker has Issue 3 • 2013

shown that the palmar digital nerve is in very close proximity to the medial and lateral limits of the bursa and the nerve may be anesthetized at this level whenever the bursa is injected. Palmar foot pain can be divided into 5 groups,4 those horses with navicular region pain (desensitized by DIP analgesia and bursa analgesia, as well as palmar digital analgesia), those with distal interphalangeal pain (desensitized by DIP analgesia, as well as palmar digital analgesia but not bursa analgesia), those that are not desensitized by DIP analgesia but are desensitized by bursa analgesia, as well as palmar digital analgesia, those that are improved by either DIP or bursa analgesia but are not sound but are sound after palmar digital analgesia, and those that are not desensitized by either DIP or bursal analgesia but are desensitized by palmar digital analgesia. It has also been noted recently that injection of the podotrochlear bursa can be very difficult and that it is quite easy to inject the DIP joint instead. We have found that not only is radiographic control necessary to successfully perform this block, but that adding contrast media to the anesthetic to prove the limits of the block is also necessary. This has lead to a new method of assessing navicular pathology, by evaluating the cartilage of the flexor surface of the navicular bone by contrast arthrography.6 Aseptic injection techniques were used to inject a 3-ml mixture of 1:1 contrast material and local anesthetic or medication. The landmarks for needle insertion was a point just proximal to the central sulcus of the frog, with the needle directed towards the apex of the frog and in a direction parallel to the ground surface of the hoof. A 20 gauge, 3.5-in. (9 cm) needle was used. The needle was inserted until resistance was encountered; this was usually at 2/3 the length of the needle. If the needle was inserted further before encountering resistance, it usually indicated incorrect placement. A lateral radiograph of the hoof was taken to confirm the position of the needle prior to injection. Ideally the needle tip was midway between the proximal and distal borders. Once the needle position was confirmed, the bursa was injected with the contrast mixture and a second lateral hoof radiograph was taken to confirm the filling of the bursa. If the bursa had been successfully injected, then a palmaroproximalâ&#x20AC;&#x201C;palmarodistal (PPPD) oblique projection of the navicular bone was obtained. The contrast material seen from a lateral view normally had the shape of an apostrophe. The contrast, seen from the PP-PD projection, was a distinct line of

Normal www.faep.netâ&#x20AC;

Bursogram showing abnormally widened bursa possibly from a distal annular ligament disruption contrast material juxtaposed to the deep digital flexor tendon which was normally separated from the navicular cortical bone by a layer of radiolucent fibrocartilage. The bursograms were evaluated for several different changes:6 (1) normal flexor fibrocartilage seen as a uniform radiolucent area 1-2mm in thickness covering the flexor surface of the navicular bone; (2) thinning or erosions of the flexor fibrocartilage, seen as a loss of the thickness of the previously mentioned radiolucent line; (3) fibrillation or splits of the deep flexor tendon within the navicular bursa, which was noted as filling defects along the bursal surface of the deep flexor tendon; (4) presence of flexor subchondral bone cystic defects, which were noted as focal filling of the flexor cortical area with contrast; (5) communication of the navicular bursa with the distal interphalangeal joint, seen as leakage of the contrast from the bursa into distal interphalangeal joint; (6) complete focal loss of the dye column, which was thought to be a result of flexor tendon adhesion to the bone; (7) narrowing or enlargement of the proximal to distal borders of the bursa (bursa change) thought to represent inflammatory changes of the bursa; (8) leakage of contrast from the bursa suggesting a tear of the border of bursa; (9) marked widening of the contrast thickness thought to indicate loss of palmar support of the tendon by the distal annular ligament; (10) contrast within the body of the tendon thought to be a focal deep flexor tear; (11) contrast within the impar ligament assumed to be indicative of tearing or damage to the impar ligament; and (12) contrast within or surrounding the proximal suspensory of the navicular bone indicative of ligament injury. Recently it has become possible to examine the podotrochlear region sonographically.7 In order to examine the podotrochlea the superficial horn must be pared from the frog to expose soft, spongy frog tissue. Next, sonographic gel is liberally applied to the frog. The ultrasound transducer is then applied to the frog. Images of the podotrochlea are apparent from the center of the frog to the apex. A 7.5 MHZ probe provides the best image. Generally, at the center third of the frog, the flexor surface of the navicular bone is readily noticeable as a hyperechoic line.7 The bursa is seen as a hypoechoic (fluid filled) region juxtaposed to the navicular bone. The deep flexor fibers can be seen curving around the bone. As the probe is moved toward the apex of the frog, the distal aspect of the navicular bone can be identified, The Practitionerâ&#x20AC;&#x201A; 7

as can the intersection between the deep flexor tendon and the impar ligament. As the probe reaches the apex of the frog, the deep flexor’s insertion on the third phalanx becomes apparent. Ultrasound is an excellent means to visualize soft tissue structures.7 However, examination of the foot has been limited to the pastern because the hoof capsule served as a barrier to examination of the hoof. The proximal regions of the navicular bone could be examined if one had a special probe that would fit between the bulbs of the horse’s heels. However, this gave no information as to what may be occurring further distally. The frog however, because of its high water content, can serve as the hoof’s “stand off”. By removing the hard outer layers, this exposes tissue that can transmit sound waves allowing the examiner to see these distal tissues. Radiography of the navicular bone includes a minimum of 4 projections of each foot5, the D65Pr- PaDiO, the lateral to medial, the PaPr-PaDiO projection, and a horizontal DP projection. Projections are assessed for changes of the navicular bone including enlarged synovial fossa, enthesiopathy, cyst-like formations, or changes of the flexor cortical region. Radiographic examination is the imaging method most often used to assess osseous changes in the distal sesamoid bone and third phalanx. These changes with the exception of fractures are usually not pathognomonic but do provide insight into damage that has occurred to the foot. Fractures also may not be radiographically visible until 10 to 14 days after the injury occurred. Through thorough examination of the horse affected by pain in the palmar region of the foot, a more precise diagnosis can be made, whether the diagnosis reflects injury to the hoof capsule, third phalanx, or podotrochlear region. Treatment then should be based on the type of injury. There are differences in the clinical presentation of navicular region pain (NRP) and palmar heel pain (PHP). Approximately 54% of the cases seen are affected by NRP and 46% by other sources of PHP. Clinical signs for these two groups have shown interesting differences. Distal limb flexion has been positive in 100% of the NRP and only 88% positive in horses in the PHP group. Hoof tester examination which is considered a cardinal sign of navicular problems was positive in only 54% of the horses with NRP as compared to 65% for those with PHP. The frog wedge was positive in 79% of the NRP as compared to 70% of the PHP horses; whereas, the toe wedge was positive 64% in NRP and only 43% in PHP. Circulatory testing indicated that only 26% of the NRP horses had poor circulation as a component to their disease,8 compared to 53% of the PHP horses having compromised circulation. Scintigraphy was positive in only 62% of the NRP cases indicating that pain can be present without scintigraphic changes.9 Also 20% of the PHP horses have a positive bone scan indicating that the navicular bone may be involved in a complex problem of heel pain. Thorough examination of the horse affected with palmar foot lameness syndrome is important not only to determine that the horse has the syndrome, but also to try to determine which type of disease process is at work. Treatment then should be based on the type of injury. Management:

The treatments of navicular syndrome vary widely, which probably reflects the treatment of multiple causes. By 8 The Practitioner

determining the most likely cause of the syndrome, the most specific problem can be treated. The treatment of caudal hoof lameness is as controversial as any aspect of this syndrome. However, it has been shown that correct shoeing should be the basis of all treatment. Any medicinal or surgical therapy should be as an adjunct to shoeing. The most successful approach to shoeing is that based on individual case needs rather than a standard formula.12 The following principles should be followed: (1) Correct any preexisting problems of the hoof, such as underrun heels, contracted heels, sheared heels, mismatched hoof angles, broken hoof/ pastern axis. (2) Use all weight bearing structures of the foot. (3) Allow for hoof expansion. (4) Decrease the work of moving the foot. Shoeing is most effective when corrections are made within the first 10 months of lameness, up to 96% success. This is in contrast to when shoeing changes are not made until after 1 year of lameness, where only 56% of the cases have been successfully treated. These principles can be accomplished using many different methods and techniques.12 Shoeing is of utmost importance in dealing with hoof pain causing the signs associated with navicular syndrome or remodeling of the bone (osseous form). It is necessary to ensure proper hoof balance and support in order to eliminate the pain and stop or decrease the stresses that are causing the problem. Six hoof balance abnormalities have been described: broken hoof axis, underrun heels, contracted heels, shear heels, mismatched hoof angles, and small feet. Some authors have attempted to define these hoof abnormalities objectively.3,12 A broken hoof axis exists when the slopes of the pastern and hoof are not the same. This condition is further defined as brokenback, when the hoof angle is lower than the pastern angle, and as broken-forward when the hoof angle is steeper than the pastern angle. Underrun heels have been defined as angle of the heels of 5o less than the toe angle. A contracted heel was defined as frog width less than 67% of the frog length. Sheared heels were defined as a disparity between the medial and lateral heel lengths of 0.5cm or more. Small feet (small feet to body size) were defined as a weight to hoof area ratio of greater than 78 pounds per square inch. The hoof angle should be the same as the hoof axis.12 Utilizing the lateral radiographic projection, the ideal hoof angulation to properly align the second and third phalanges can be measured accurately.3 The appropriate correction can be determined by measuring the degree of malalignment (flexion or extension) present in the coffin joint and raising or lowering the hoof angle that amount. For instance, if the lateral radiographic projection showed 4o flexion of the coffin joint, then the hoof angle should be lowered 4o. In addition to hoof axis deviations, the lateral radiographic projection can be used to document problems of heel support. Measuring the appropriate position on the radiograph can determine the proper position of the heels. From a practical point, the heel-ground contact should be even with the base of the frog. Underrun heels are the most commonly encountered hoof abnormality. In one study of foot-related lameness it was found in 77% of the horses and in another study of normal performance horses this condition was found in 52% of the Issue 3 • 2013

horses. The necessity of correcting underrun heels has been well documented. If left uncorrected, underrun can cause alterations in hoof wall growth that can be very difficult to correct and it can predispose to lameness problems that range from bruised heels to navicular syndrome. Medial/lateral imbalance or shear heels have been shown to cause, or predispose to a number of hoof-related lameness.12 Medial/lateral balance can be assessed by both the hoof measurements and the radiographic examination. The graph of hoof wall measurements will clearly show if one side of the hoof is longer than the other. The obvious correction is to make the walls equal, although it is not always that simple. The dorsopalmar radiograph will also clearly demonstrate any imbalance. Since this projection will also show the effect the imbalance has on the coffin joint, this radiograph can be used to emphasize the need for correction. The magnification in most radiographs makes even subtle disparities more obvious. It is accepted that conformation can alter this balance. The radiograph will help determine if the imbalance is hoof related or conformational. Hoof-related imbalances will show medial/lateral hoof length disparities, and the first and second phalanges can be bisected equally. If the medial/lateral disparity is conformationally related, the first and second phalanges will appear oblique on the DP radiograph. The final assessment of balance is the weight of the horse in proportion to its feet.3,12 Small feet have been a commonly described problem, particularly in Quarter Horses, that predispose the horse to lameness. One study identified small feet as an indicator of poor prognosis in the treatment of navicular syndrome. Most descriptions of what actually constitutes a small foot are quite subjective. However, studies have been performed utilizing simplistic formulas to make this assessment objective. These studies measured the circumference of the hoof immediately below the coronary band. This was done to get a rough idea of the hoofâ&#x20AC;&#x2122;s cross sectional area. This was then compared to the horse's weight and statistical analysis was performed. A ratio of seventy-eight pounds per square inch was determined to be the maximum weight to hoof area ratio for a normal performance horse. The steps to determine this number have been simplified to the following formula: 12.56 X wt (lbs)/C2(in2). Once identified, a high weight to hoof area ratio can be used to show a client that the horse should lose weight. In addition, it can be used to show the necessity of fitting a shoe as fully as practical in order to produce the largest surface area as possible for that particular horse's hoof. The author believes there is a hierarchy of hoof problems;3 in other words when dealing with these problems, which is the most important. The most important problems relate to heel support; and this means not simply adding shoe but improving the ability of the quarters and heels of the hoof capsule to bear weight. The next most important issue to deal with is that of medial to lateral balance. Improving the ability of the hoof to expand follows this. This is followed by body size to foot size mismatches. The least important of the hoof problems appears to be hoof pastern axis. Oddly enough this is the one most commonly and easily treated. These hoof balance issues have importance relative to prognosis.12 Caudal hoof lameness treated with shoeing alone within the first 10 months of lameness has been 97% successful in managing www.faep.netâ&#x20AC;

the lameness. However, in horses that have been lame for one year or more, shoeing is only 54% successful. The presence of underrun, contracted and sheared heels in the feet makes it four times less likely to be successful. Finally, in horses with a hoof area to weight ratio of 83 lbs/in2 or more, none were successfully treated with shoeing. Even though shoeing is the key to therapy, each of these cases usually requires additional therapy. The selection of therapy should be based on clinical and imaging findings.3,10 Coffin joint pain is inferred in horses that respond to coffin joint anesthesia. Coffin joint pain may be suspected if the distal limb flexion is very positive and other manipulative tests are either mild positive or negative. It is my opinion that these cases should be treated for inflammation of that joint. This may include systemic nonsteroidal antiinflammatory therapy, but intra-articular therapy or specific joint therapy should be considered.10 The use of hyaluronic acid and corticosteroids as anti-inflammatories within the joint is well documented. In addition, the use of intra-articular or intramuscular polysulfated glycosaminoglycans has been useful in the control of joint disease. Most frequently I use PSGAGs if I suspect cartilage damage (500mg IM, every 4 days for 4 weeks). Whenever encountering coffin joint pain, if the horse responds to medial/lateral wall wedge tests I suspect distal interphalangeal collateral desmitis. I will examine the collaterals sonographically to determine if desmitis is present. If desmitis is present the joint is treated differently. Collateral desmitis must be treated with rest to allow time for the ligaments to heal. The average time for healing is 4 to 5 months. The author has found shockwave therapy to reduce the healing time by half. PRP and stem cell therapy have also been used to reduce healing time. In cases where the frog wedge test is the most positive manipulative test,3 I suspect pain in the navicular bursa area. This lameness should be eliminated by navicular bursa analgesia. The author treats these cases by intrabursal corticosteroid. Cartilage damage on the flexor surface can most easily be assessed by contrast navicular bursagraphy. Cartilage damage is treated by polysulfated glycosaminoglycans. Tears in the bursa need to be treated with rest; however, persistent pain in this region has been a problem. Treatment of vascular forms of the disease will need to be treated with vasoactive drugs.3,11 Four drugs have been used for this purpose, warfarin, isoxsuprine, metrenperone, and pentoxifylline. The author uses only isoxsuprine for these cases. Isoxsuprine HCl is the most common drug used to increase the circulation to the podotrochlea. Although, there is some controversy as to the effectiveness of oral administration. It is dosed at 0.6-1.2mg/kg b.i.d. until sound, then decreased to s.i.d. for 2 weeks then further decreased to every other day. My approach to using this drug has been to dose at 1.2 mg/kg b.i.d. for 2 weeks, followed by 1.2 mg/kg s.i.d. for 1 week, and then 0.6 mg/kg s.i.d. for 1 week. The drug is discontinued after the fourth week and the effect reassessed. If the horse becomes lame after discontinuance, the drug is restarted at 1.2 mg/kg s.i.d., then reduced weekly to the minimum effective dose. In cases where desmitis of the navicular suspensory ligament or impar ligament is suspected there are basically 2 treatment alternatives.3 Treatment is designed to reduce strain on the ligament. This can be achieved by either raising the heels of the The Practitionerâ&#x20AC;&#x201A; 9

horse's foot or by cutting the collateral sesamiodean ligaments References: 1. Turner TA: Diagnosis and treatment of the navicular syndrome in horses. (CSL). Collateral sesamoidean desmotomy is a surgery that has in Yovich JV (ed): The Equine Foot, Vet Clin of NA: Eq Prac, Philadelphia, WB become popular in Europe and has been effective on selected Saunders Co, 1989: 131-‐144. 2. Turner TA, Fessler JF: The anatomic, pathologic and radiographic aspects of cases of navicular syndrome. navicular disease. Comp Cont Ed, 4(8): S350-‐ S355, 1982. Similarly, when the deep flexor tendon is involved, raising 3. Turner TA. Caudal hoof lameness, in Floyd AE and Mansmann RA: Equine 3 the heels of the hoof will decrease strain on the tendon. But Podiatry. Saunders-‐Elsevier, St. Louis, 2007, 294-‐312. in addition, desmotomy of the inferior check ligament has also 4. Turner TA: Predictive value of diagnostic tests for navicular pain. In recently been shown to be effective in treatment of these cases. Proceedings 42nd Annual Meeting Am Assoc Eq Pract, 1996; 42: 201-‐204. 5. Turner TA, Kneller SK, Badertscher RR, Stowater JL: Radiographic changes in But if tendonitis is diagnosed the tendon needs to be rested. With the navicular bones of normal horses. In Proceedings 32nd Annual Meeting of Am the new regenerative medicine, tendons certainly can be aided in Assoc of Equine Pract, 1986; 32: 309-‐314. their healing by PRP or stem cell injections. Shockwave therapy 6. Turner TA: Use of navicular bursography in 97 horses.in Proceedings 44th has also been used in these cases. Annual Meeting Am Assoc Eq Pract, 1998; 44: 227-‐229. 10 If shockwave therapy is to be used, the foot must be clean of 7. Sage AM, Turner TA: Ultrasonography of the soft tissues of the equine foot. Eq Vet Educ, 2002; 4: 278-‐283. debris (soak if preferred for optimal energy transmission) and 8. Turner TA, Fessler JF, Lamp M, Pearce JA, Geddes LA: Thermographic trim the hair in the area of treatment, wipe skin with alcohol, evaluation of horses with podotrochlosis. Am J Vet Res 1983; 44(4): 535-‐ 539. and apply the ultrasound gel to the area of treatment.13 When 9. Dyson SJ. Subjective and quantitative scintigraphic assessment of the equine foot treating through the frog, trim outer layers so the frog is soft. If and its relationship with foot pain, Eq Vet J 2002; 34: 164-‐170. you can get an ultrasound image through the frog, then shock 10. Trotter GW: Therapy for navicular disease. The Compendium on Cont Ed, 1991; 13: 1462-‐1465. waves will also penetrate there. Two thousand shocks at highest 11. Colles CM. Navicular disease and its treatment. In Prac 1982; March: 29-‐ 35. energy setting using the 5 mm or 20 mm probe depending on 12. Turner TA. Navicular disease management: shoeing principles, in Proceedings. the depth of the lesion: for Navicular Syndrome, deliver energy 32nd Annu Conv Am Assoc Equine Practnr 1986; 32: 625-‐ 633. at the hairline over the palmar pastern and/or over the frog, for 13. McClure S, Evans BE, Miles KG, et al. Extracorporeal shock wave therapy for collateral ligament desmitis, deliver 1,000 pulses over the injury treatment of navicular syndrome, in Proceedings Annual Meeting Am Assn of Equine Pract 2004; 50: 316-‐319. and the remaining 1,000 shocks over the joint, for deep flexor 14. Denoix, J.M., Thibaud, D. and Riccio, B. (2003) Tiludronate as a new therapeutic tendon injuries, navicular bursa, edema, cartilage erosion, cystic agent in the treatment of navicular disease: a double-‐blind placebo controlled lesions, and adhesions, focus the energy over the center of the clinical trial. Equine vet. J. 35, 407-‐ 413. injury. Post-treatment protocol; advise the client to begin walking or working the horse immediately after treatment. Repeat the treatment in 3 weeks and walk the 9 horse during the healing process. Staying in the stall does more harm than good. You may want to remove a horse’s shoes when the horse is in the stall, trim the hoof appropriately: abnormal stress on the hoof causes Tracy Turner, DVM, MS, Dipl. ACVS Anoka Equine Veterinary Services abnormal stresses on soft tissues and delays healing. Elk River, MN In long-standing cases of navicular pain, excessive remodeling of the navicular bone is a problem. In these cases tiludronate • DVM, Colorado State University, 1978 has been used effectively to treat the disease.14 Dosage is either • Interned at the University of Georgia 0.1mg/kg administered slowly intravenously daily for 10 con• Surgical Residency and MS, Purdue University secutive days or 1mg/kg administered slowly intravenously once. • Served on the faculties of the University of Illinois, There are reports of veterinarians using the 0.1mg/kg dose as a University of Florida and University of Minnesota regional perfusion. There is no scientific evidence that this is an • Has practiced in Sports Medicine, Lameness and Surgery effective administration of the drug. at Anoka Equine Clinic, Elk River, MN since 2004 When all other treatments have failed or have not had the • Named to the American Farriers Journal International desired effect, palmar digital neurectomy remains a viable treatEquine Veterinarians Hall of Fame, 2004 ment alternative.10 Numerous techniques are available but all Dr. Turner's primary area of research interests has focused on follow some basic rules. First, the neurectomy will not improve equine lameness with particular interest in equine podiatry and the lameness any more than a palmar digital nerve block. Therethermography. He has spoken nationally and internationally fore, it is highly recommended that the nerves be anesthetized on lameness topics. He has written over 100 peer-reviewed manuscripts, over 250 with the owner/rider present so that they can decide whether the non-peer- reviewed papers, and 30 book horse has sufficiently improved. Second, neuromas are a common chapters on equine lameness, podiatry and problem but can be avoided by atraumatic surgical technique. thermography. Dr. Turner is one of only four Atraumatic surgery can really only be learned by practice. Neuveterinarians who are certified in Thermology roma formation can be decreased by allowing the surgical wounds by the American Board of Thermology. to heal as well as possible, before returning to work. This usually requires 4 to 6 weeks rest after the surgery. Third, the horse will lose skin sensation in the back half of its foot but probably loses all or most of its sole sensation. However, the horse will always know where the foot is. The foot then should be protected somehow, usually by a pad. 10 The Practitioner

Issue 3 • 2013

EQUINE DENTAL RADIOLOGY INTRODUCTION For years, equine surgeons have found equine skull radiography to be a valuable tool in the diagnosis and management of dental disease. The excellent contrast among air, bone, soft tissue and tooth substance makes the head an ideal area for radiographic evaluation. Conventional or standard radiographic projections adequately image the reserve crown apices, lamina dura denta, alveolar space and alveolar bones as well as changes in the associated maxillary, mandible and sinonasal structures. With these conventional closed mouth radiographic projections, the erupted crown is obscured by superimposition of the crowns of the opposite dental arcades. Until recently, radiography has been of limited value in the assessments of lesions involving the gingival margins or evaluation of the exposed tooth crown. With the recent introduction of open mouth oblique radiographic views, a more accurate diagnosis of lesions affecting the clinical crowns of the check teeth can be made. With the development of smaller flexible intra-oral equine dental cassettes used with plane film or DR plates, the entire crown and apical region of a tooth can be imaged. Several factors may limit the practitioner from acquiring good quality films (i.e., size of the horse, types of intensifying screens and films and exposure capabilities of the portable x-ray machine). Some limitations can be overcome by reducing movement of the horse’s head and appropriate positioning of the x-ray cassette and x-ray machine while taking the radiography. The differences in tissue density and the increasing width of the horse’s head from rostral to caudal may require more than one radiographic exposure of the anatomical area to highlight the tissues to be evaluated. With DR and CR the computer algorithms in the radiographic system can be adjusted to compensate for most variations in tissue thickness. In order to generate the required image, knowledge of skull anatomy and topographic landmarks is necessary to ensure correct positioning of the x-ray unit, cassettes and horse’s head. The head is anatomically complex and the use of large cassettes -14” x 17” (34cm x 48cm) – helps maintain spatial relationships when evaluating the radiograph. Coning down on the radiograph will allow better contrast and detail over a smaller area of greater concern. It is helpful to use both right and left projections in order to take advantage of image sharpness and magnification in the location of interest. Because of age-related changes in the hypsodont teeth of the horse, it is beneficial, at times, to take lesion-orientated oblique views of the affected area and the opposite (normal) side of the skull to have a comparison film to evaluate. Good quality radiographs can be taken with a high-frequency portable x-ray unit capable of generating 80KVp and 15MA. Medium or regular speed rare earth cassettes with fast speed film without a grid can be used with a focal film distance of 80-100cm. Most of the DR and CR systems on the equine market are well suited to head and dental radiography. A table or headstand with a flat surface (approximately 100cm off the ground) is used to www.faep.net

by Jack Easley, DVM, MS, DABVP (Equine)

support the sedated horse’s head. Smaller cassettes are used for lesion oriented oblique films. Wooden or foam blocks are used to position the head and x-ray cassettes. These blocks are also used to support smaller cassettes and to elevate the cassettes to the height of the cheek teeth arcade. Bungee cords are useful to hold cassettes in position. A blindfold or towel placed over the horse’s eyes aids in restraint and helps avoid motion artifacts. Three different 10cm long sections of PVC pipe can be used as mouth gags. A 7.5cm diameter section of pipe is used on smaller horses and ponies. This diameter equates to two clicks on the standard McPherson mouth speculum. Sections of 9cm diameter and 11.5cm diameter PVC pipe are used to wedge the mouth open in larger horses. Two sections of 3-meter long x 0.5cm diameter cotton or nylon rope are used to steady the horse’s head and/ or put traction on the mandible. A cassette holder and suitable radiation protection equipment consisting of gloves, apron, and thyroid guards are used when taking the x-rays. Heavy sedation of the horse is necessary both to safely obtain skull radiographs and to facilitate separation of the maxillae and hemi-mandibles. A combination of xylazine hydrochloride @ .3-.6mg/Kg or detomidine hydrochloride @ 10-20mcg/Kg with butorphanol tartrate 10mcg/Kg provides 20-30 minutes of heavy sedation. This allows time for a comfortable and detailed oral examination and relaxed, motionless radiographs with the horse resting its muzzle on the table or head stand.

DENTAL RADIOGRAPHS VIEWS AND TECHNIQUE Lateral Radiographs:

This view is obtained with the cassette positioned in a vertical plane, as close as possible to the affected side of the head. The rostral aspect of the facial crest is approximately the center of the cheek tooth rows in most horses, and the horizontal x-ray beam should therefore be centered at this point. This view is easy to obtain and is useful for assessment of the paranasal sinuses for fluid lines, which may be caused by empyema due to apical infection of the 3rd to 6th maxillary cheek teeth. The main disadvantage of this view is that the apices of the left and right cheek teeth are superimposed and it is therefore not possible to evaluate individual apices for radiographic changes. 30-degree dorsolateral-lateral oblique radiographs (maxillary check teeth apices):

This oblique radiographic view separates the left and right maxillary cheek teeth rows, allowing evaluation of The Practitioner 11

individual apices and the surrounding maxilla. The cassette is again positioned in a vertical plane, as close as possible to the affected side of the head. The x-ray tube is positioned at a higher level on the opposite side, with the beam directed 30 degrees down from the horizontal and centered at the rostral aspect of the facial crest. The additional presence of rostro-caudal angulation is a common technical fault associated with this projection and should be avoided.

Open-mouthed oblique radiographs (15 degrees ventrolaterallateral for maxillary 7 erupted crowns, 10- to 15-degree dorsolateral-lateral for mandibular erupted crowns):

35- to 45-degree ventrolateral-lateral oblique radiographs (mandibular cheek teeth apices):

This oblique radiographic view separates the left and right mandibular cheek teeth rows, allowing evaluation of individual apices and the surrounding mandible. For this projection,the cassette is again positioned vertically as close as possible to the affected side. The x-ray tube is positioned at a lower level on the opposite side, and the beam directed 35-45 degrees up from the horizontal, centered on the affected tooth. Although increasing the angle gives greater separation of the left and right cheek teeth rows, increasing distortion of the apices also occurs, making dental evaluation more difficult. A larger angle is required to separate the cheek rows in smaller heads where the intermandibular distance is short. The thick masseter and pterygoid muscles overlay the caudal 2-3 cheek teeth and increased exposure is usually required to image these apices, as compared to the rostral 3-4 cheek teeth.

These radiographic projections are useful for evaluating the erupted (clinical) crown of the cheek teeth, which are usually not visible on conventional views due to superimposition of the opposing arcade. A Butler’s gag or hollow PVC pipe is placed between the incisors of the sedated patient to separate the maxillary and mandibular erupted crowns. The direction of the x-ray beam is the opposite of that used for conventional (closed mouth) views and the angle of incidence of the beam is also reduced (i.e., 10-15 degrees). Disorders such as coronal fractures, diastemata and disorders of wear can be well evaluated using these projections. Intra-oral occlusal radiographs of incisor teeth:

Dorso-ventral radiographs:

This radiographic view is obtained by positioning the cassette underneath and parallel to the hemi-mandibles (the horse’s head can be “rested” on the cassette). The x-ray beam is directed perpendicular to the plate, centered in the midline, at the level of the rostral aspect of the facial crest. Positioning is very important when taking this radiographic view because any lateral distortion from a true DV will cause superimposition of the mandibular and maxillary arcades on one side. This view is most useful for evaluating the areas of the ventral conchal sinus (medial compartment of the rostral maxillary sinus), nasal cavity, and nasal septum. Laterally or medially displaced teeth can also be observed from this view, sagittal fractures, and advanced caries of the maxillary cheek teeth can also be detected. The mandibular cheek teeth are not as easily evaluated from this view because the dense cortical bone of the hemi-mandibles overlies their lateral aspects. Transverse fractures of the mandible and occasionally maxillary bone fractures may also be observed with this view.

12 The Practitioner

These projections are useful for evaluating the incisors and canines. A small cassette or non-screened film is placed between the incisors and canines, as far caudally as possible, and the x-ray beam is directed at 60-80 degrees in order to include the reserve crown and apices of the incisors. Intra-oral radiographs of the cheek teeth:

This modified Gibbs technique utilizes a flexible 4”x 8” cassette and a bisecting angle technique that was perfected by David Klugh. It provides Issue 3 • 2013

Lecture Topics Include • • • •

Alternative Medicine Dentistry Dermatology Infectious Disease

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Neonatal Lameness/Medication Issues in R acing Lower Respir atory Disease

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Dr. Aric Adams, DVM, DACVS Intravenous regional perfusion (IVRP) has become a common and efficacious treatment for localized infections of the distal limbs of horses. It can be a useful delivery technique for various antimicrobials, antifungals, and other medications. It allows for the administration of lower drug dosages with achievement of drug levels in the targeted region that are much higher than levels achieved by systemic administration. In the laboratory, we will learn about appropriate antimicrobial selection and protocols, proper patient restraint and preparation, and various techniques in performing IVRP in different anatomic locations of the horse.

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Rosanna Marsella, DVM, DACVD 5:25 p.m. - 6:55 p.m. Reception & Dinner 6:55 p.m. - 7:45 p.m.

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Spinal Manipulation to Enhance Lameness Diagnosis Carla Pasteur, DVM, CVA

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Clinical Cases and Alternative Medicine in Sport Horses Carla Pasteur, DVM, CVA

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Practical Neonatal Foal Evaluation and Care Part I Carol Clark, DVM, DACVIM

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Practical Neonatal Foal Evaluation and Care Part II Carol Clark, DVM, DACVIM

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Florida Laws and Rules Governing the Practice of Veterinary Medicine Part I Ed Bayó, JD

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Florida Laws and Rules Governing the Practice of Veterinary Medicine Part II Ed Bayó, JD

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The Practitioner 21

Continued from Page 13

In early cases of dental disease, scintigraphy (which provides a functional image of bone) is proving a useful adjunctive tool to radiography, being highly sensitive (95%), but of moderate specificity (86%) (Weller et al, 2001). Because of the major short and longterm consequences of extracting the wrong cheek tooth, it is better to take a conservative approach in such cases if scintigraphy is not available, or if the combined results of these two imaging modalities are unclear. If there is any doubt as to whether a tooth needs to be removed, it is better to err on the side of caution by treating suspected dental infection with systemic antibiotics and re-evaluating radiographically in four to six weeks time, where changes may have become more marked.

the sinuses may decrease the amount of fluid accumulation within the sinuses and allow for a more accurate radiographic evaluation of the underlying structures such as cheek teeth apices and ethmoturbinates. Dental Sinusitis

Periapical dental infections are a common cause of sinusitis in horses (Lane et al. 1987b, Gibbs and Lane 1987). The apices of the third, fourth, fifth and sixth (and variably, the second ) maxillary cheek teeth lie within the rostral and caudal maxillary sinuses, and abscesses which form around the dental apices can erode the thin alveolar bone, with resultant infection of the sinuses. NASAL CAVITY AND PARANASAL SINUSES Radiographic changes consistent with early periapical infection include widening of the periodontal space and thinning Normal Anatomy of the lamina dura denta (the dense rim of cortical bone which The rostral maxillary sinus (RMS) is usually positioned dorsal lines the alveolus). When periapical infection has been present to the upper 08s and 09s (third and fourth cheek teeth) apices for many weeks, the affected apices develop lytic changes, and is separated from the caudal maxillary sinus (CMS) by a especially in mature teeth where the true roots (non-enamel complete bony septum. This septum is usually angulated from areas) are well formed. These changes manifest as periapical rostro-lateral to caudo-medial and therefore is not usually seen radiolucent “halos,” and the rounded or “clubbed” appearance as a single radiodense line in lateral radiographs. In horses under of the tooth roots are due to gross lyses and destruction of the 7 years-of-age, the reserve crowns of the upper 08s and 09s can root structures. In more chronic periapical infections, a zone almost completely fill the lateral compartment of the RMS; of radio dense sclerosis usually surrounds the periapical “halo.” and even in the older horse with shorter cheek teeth reserve This is due to new bone deposition around the lytic infected crowns, the RMS often remains a small structure. The medial area. A more marked sclerosis develops around the apices of the compartment of the RMS is also known as the ventral conchal first two maxillary cheek teeth than the caudal maxillary cheek sinus (VCS), and communicates with the lateral compartment teeth. This is because the first two maxillary cheek teeth are over the infra-orbital canal. The VCS often extends caudally (as usually positioned in more dense bone than the caudal maxillary the ventral conchal “bulla”) to the level of 111/211 (sixth cheek cheek teeth, which are situated in thin alveolar bone within the tooth), and is best radiographically evaluated using a dorso- maxillary sinuses. ventral projection. Longstanding periapical infection may result in abnormal The CMS is usually positioned immediately dorsal to the depositions of cementum at the tooth apex. Dystrophic upper 10s and 11s (fifth and sixth cheek teeth) apices, and mineralization of the nasal conchae (coral formation) may also communicates with the concho-frontal sinus via the large occur with chronic maxillary cheek teeth periapical infections fronto-maxillary aperture. The frontal sinus is the dorso- (Lane et al. 1987b). caudal extension of the conchofrontal sinus, and appears as a Soft tissue densities may also be apparent in the sinuses if triangular structure on lateral radiographs, positioned dorsal to periapical infection of the caudal 3-4 maxillary cheek teeth has the ethmoturbinates and rostral to the cranium. occurred. This may be due to a rounded, soft tissue granuloma or The nasal cavities are positioned medial and rostral to the later, an encapsulated abscess developing over the infected apex. VCS and the left and right cavities are separated by the nasal septum that runs in the midline. This structure, which can be References: Arnbjug J, Bittegeko S. Radiographing the incisor and canine teeth seen on DV radiographs, should be evaluated for lateral distortion, of horses. J Vet Dent, 1996, Vol 12, 14 No 2, 74. most commonly due to space occupying lesions within the nasal Banner, TA. Using computed tomography in evaluation of equine dental disease. In Proceedings, Am Assoc Equine Pract, Focus on cavity or VCS. Primary Sinusitis

Horses with primary sinusitis often have free fluid within the sinuses that may be seen as a horizontal fluid line (with increased opacity below the line) on standing lateral radiographs. Other changes associated with primary sinusitis are localized, diffuse or delineated intra-sinus radio-opacity, nasal septum deviation and mineralization of sinus contents in more chronic cases. In many cases of sinusitis, the increased soft tissue density within the sinuses may simply be due to inflamed and hypertrophied sinus mucosa, which occurs with chronic sinus infections (Lane et al., 1987b). It should be remembered that fluid or soft tissue densities within the sinuses may also be seen secondary to other disorders causing sinusitis. Trephination and lavage of 22 The Practitioner

Dentistry, 2006. Barakzai, S; Dixon PM. A study of open-mouthed oblique radiographic projections for evaluating lesions of the erupted (clinical) crown. Equine Vet Edu, 2003, 15(3), 143-148. Barakzai, S. Radiology and scintigraphy, techniques and normal and abnormal findings. In Proceedings, Am Assoc Equine Pract, Focus on Dentistry, 2006. Baratt, RM. How to use computed dental radiography in ambulatory practice. In Proceedings, Am Assoc Equine Pract, Focus on Dentistry, 2006, 293-306. Baratt, RM. How to obtain equine dental radiographs in ambulatory practice. In Proceedings, Am Assoc Equine Pract, 2007, Vol 53, 460-465. Barakzai, SZ. Dental Imaging. In Easley J, Dixon PM, Schumacher J, eds Equine Dentistry 3rd ed, Edinburgh: Saunders/Elsevier, 2010; 199-230

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Behrens E, Schumacher J, Morris E, et al. Equine paranasal sinusography. Vet Radiology, 1991, Vol 32, No 3, 98-104. Dixon PM, Copeland AN. The radiological appearance of m andibular cheek teeth in ponies of different ages. Equine Vet Educ, 1993, 5(6), 317-323. Finn ST, Park RD. Radiology of the nasal cavity and paranasal sinuses in the horse. In Proceedings, Am Assoc Equine Pract, 1987; 33: 383-397. Gibbs C. Dental imaging. In Baker GJ and Easley J, eds. Equine Dentistry. London: WB Saunders, 2005; 171-202. Gibbs, C; Lane, JG. Radiographic investigations of the facial, nasal, and paranasal regions of the horse. Equine Vet J, 1987, 474-492. Klugh DO. Intraoral radiology in equine dental disease. Clin Tech Equine Pract, 2005, 4:162-170. Lane, JG; Gibbs, C; Meynink, S, et al. Radiographic examination of the facial, nasal and paranasal regions of the horse: indications and procedures in 235 cases. Equine Vet J, 1987; 19: 466-473. Lane, JG; Gibbs, C; Meynink, S, et al. Radiographic examination of the facial, nasal, and paranasal sinus regions of the horse: Part I. Equine Vet J, 1987, 466-473. Misk, NA; Seilem, SM. Radiographic studies on the development of cheek teeth in donkeys. Equine Pract, 1997, Vol 19(2), 27-38. Pascoe, JR. Dental radiography/radiology. In Proceedings, Am Assoc Equine Pract, 1991; 37: 99-111. Puchalski, SM. Computed tomography and ultrasonographic examination of equine dental structure: normal and abnormal findings. In, Proceedings, Am Assoc Equine Pract, Focus on Dentistry, 2006. Salano, M; Brawer, RS. CT of the equine head: Technical considerations, anatomical guide, and selected diseases. Clin Tech Equine Pract, 2004, 3:374-388. Tietze, S; Becker, M; Bockenhoff, G. Computed tomographic evaluation in head diseases in the horse: 15 cases. Equine Vet J, 1996; 28: 98-105.

Tucker, RI; Farrell, E. Computed tomography and magnetic resonance imaging of the equine head. Vet Clin North Am, Equine Pract 2001; 17: 131-144. Weller R, Livesey L, Nuss K, et al. Comparison of radiography and scintography in the diagnosis of dental disorders in the horse. Equine Vet J. 2001; 33:49-58. Zaluski, P; Davis, M. How to obtain diagnostic radiographs of the equine molars. In Proceedings, Vet Dental Forum, 2003.

Jack Easley, DVM, MS, DABVP (Equine) Equine Veterinary Practice, LLC Shelbyville, KY • • • •

DVM, Tuskegee University College of Veterinary Medicine, 1976 Equine Surgical Residency and MS, Kansas State University Associate Professor of Surgery, Kansas State University, 1978 – 1980 Associate Professor of Surgery, Virginia-Maryland College of Veterinary Medicine, 1980 - 1982 • Certified DABVP (Equine) , 1982, 1992, 2002, 2011 Dr. Easley is a member of the American Association of Equine Practitioners (AAEP), the American Veterinary Dental Society, International College of Equine Veterinary Odontologists, American Veterinary Medical Association, Kentucky Veterinary Medical Association, Kentucky Association of Equine Practitioners (past president), KY Veterinary Medical Association, Shelby Co. Chamber of Commerce, and Shelby Co. Community Foundation.

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The Value of Quality Foot Radiographs and the Impact they have on Balanced Farriery by Randy B. Eggleston, DVM, DACVS

adiographic evaluation of the horse’s foot for the purpose planning process. This simplifies evaluation of break-over, sole of consultation with the farrier is becoming more popular, depth, and balance of the foot. If a source of lameness has been but is still an underutilized use of radiographic imaging. localized to the foot, removal of the shoes may be necessary in In the absence of lameness, detailed radiographic evaluation of order to obtain the additional views necessary to fully evaluate the horse’s foot is very useful in preplanning and management of the foot. Proper shoe removal technique is a skill that the trimming and shoeing of a horse’s foot, and in the prevention of veterinarian must be comfortable with. lameness. Horses exhibiting poor foot conformation, imbalance, Cleaning the foot of all particulate matter as well as removing or abnormal patterns of growth can be clues to impending foot any fragmented wall and overgrown sole and frog will reduce disease and lameness. Radiographic evaluation of a horse’s foot the potential for gas artifacts. Any flakiness of or accumulations gives tremendous insight into the relationship between the of debris on the outer wall can be removed with either a rasp structures within the foot, and between the foot and distal limb. or a sanding block. Radiographs taken to guide trimming and Digital photography has also been shown to be useful and shoeing do not require packing the foot; if additional films are accurate in the assessment of the horse’s foot.1 However, the required, packing the foot is recommended. Packing the sulci relationship of the distal phalanx with the hoof capsule cannot (Play-Doh® or appropriate putty material) reduces the likelihood be appreciated with photography alone. of radiographic artifact due to gas in the sulci. Liberal use of The quality of information obtained from a radiographic study the packing material should be used to fill the depths of the depends solely on the quality of the radiographs (“garbage in, sulci; however, overpacking will cause packing artifact along the garbage out”). Producing quality radiographs is dependent on the margins of the packing. Traditional packing in horses that have use of quality equipment, developing a proficiency at operating deep center sulci or overgrown bars can be difficult in eliminating that equipment, and maintaining consistency when performing all gas artifacts. Placing the foot in a water bath is an effective radiographic studies. A systematic approach should be taken method of displacing trapped gas deep within the sulci or wall. when planning a radiographic study of the foot; the “point and shoot” approach is not always the best approach. Taking multiple standard views, although not always necessary, is important to avoid missing a diagnosis. Additional projections may be required to further investigate initial findings or confirm a diagnosis. There are a number of preplanning questions that need to be asked before performing foot radiographs: 1) What is the purpose of the study, investigation of lameness or consultation with the farrier? 2) What do I expect to gain from the study, source of lameness or information useful in managing the foot? and 3) What information do I need to obtain from the study, relationship of the hoof capsule and the distal phalanx? The answers to these questions will guide in planning the study with regard to the appropriate views to be taken, the appropriate technique, and the appropriate positioning of the foot and centering of the x-ray beam. Taking the time to examine the foot and prepare it properly The water depth should be at a level just proximal to the heel will avoid the need, risk, and expense of repeating images and bulbs. Placing the cassette or digital sensor in a plastic protective will improve the quality and therefore the interpretation of cover (trash bag) prior to placement of the foot will reduce your radiographic images. Before performing a full series of foot the potential for water damage. A 50% increase in technique radiographs it is common practice to recommend removing the is recommended when using digital radiography; when using shoes. However, when acquiring radiographs for the purpose of film-screen radiography a significant increase in mAs will also trimming and shoeing be necessary and will depend on whether a grid is used or not. issues, leaving the Digital radiography (DR) has become commonplace in equine shoes in place can practice and gives rise to a number of advantages over film/screen be beneficial. Direct radiography when evaluating the foot. The advantages of DR over visualization of the film/screen radiography include digital postprocessing, improved weight-bearing surface image quality, and improved archiving. Digital radiographs and the position of the have tremendous exposure latitude compared with plain film shoe in relation to the radiography. With a single image from a single exposure the hoof capsule and distal clinician has the ability to adjust brightness and contrast allowing phalanx can help in the 26 The Practitioner

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for visualization of multiple tissue densities. Once captured, beam be flawless when evaluating the foot for the purposes of processed, and saved, the images can be archived electronically, podiatry. True assessment and measurement of the dorsal hoof resulting in easier storage and follow-up evaluation, comparison wall and heel angle, sole depth, joint congruity, medial to lateral and manipulation.2 Despite the advantages of digital technology, balance, and toe to heel ratio is dependent on proper positioning. like any imaging technology it has its limitations. Furthermore, Slight abduction or adduction of the limb or shifting of weight high-quality conventional radiographs are satisfactorily diagnostic can cause joint incongruity on the horizontal beam dorsal-palmar for many purposes. However, because there is less exposure view. The horse should be placed on a firm level footing with the latitude with conventional film/screen radiography, it is limbs squarely beneath them. Limb conformation should also important to establish standard technique charts, taking into be evaluated prior to taking radiographs. When placing the foot consideration the view to be taken, what information is to be on the positioning blocks it is important to allow the foot to obtained from the particular view, and the size of the foot.3 position itself as dictated by the limb's conformation (toed-in, Additionally, because the same degree of detail and contrast is not toed-out). To reduce magnification the foot should be placed on as obvious on conventional film, establishing multiple techniques the positioning block in such a way that the foot is as close as (soft tissue and bone) for each view is necessary to visualize and possible to the cassette or sensor plate. evaluate soft and osseous tissues. Commercial positioning blocks and stands are available that Accurate identification of key points on the foot, allowing aid in standardizing focal distance, foot placement and alignfor evaluation of dorsal hoof wall and heel angles, sole depth, ment of the x-ray beam. Wood blocks of the appropriate size and and medial and lateral wall height, is not always possible height work well; commercial blocks are available but they are depending on the technique used and the conformation of the also simple to fabricate to the practitioner’s desired specificafoot. Digital radiography allows improved visualization of soft tions. A variation of the standard block, and one that the author tissues; however, accurate identification of the coronary band uses, is one that has been adapted from one originally described and heels can still be difficult. Edge burn through (saturation by Caudron.4 It is composed of two independent circular blocks artifact) at the periphery of soft tissues is a common artifact with digital radiography.4 This in particular can result in inaccurate assessment of hoof wall thickness. Rigid metallic markers are often used to identify the true border of the dorsal wall; however, accurate identification of the wall length and contour is impossible unless the marker equals the length of the toe and can be contoured to the true shape of the wall. Running a 2mm bead of Barium paste (can be easily stored in and applied from a 60 connected in such a way which allows rotation of the two halves. ml syringe) directly over the dorsal median hoof wall extending A copper wire is embedded in the surface of the block forming a from the coronary band to the tip of the toe allows for accurate 15 cm circle; this acts as a radiographic marker for the weightidentification of the toe length, wall contour and border, and an bearing surface. Regardless of the beam angle with the surface of appreciation of hoof wall distortion. Due to the increased beam the block, a line drawn from the two apices of the ellipse will be attenuation of the Barium paste, a halo artifact (Überschwinger) parallel to the weight bearing surface. The rotational component may be seen surrounding the Barium but this will not preclude of the block works well for horses that exhibit abnormal conforaccurate border identification.5 Spot marking at 1) widest point mation such as a toed-in or toed-out conformation. When the of the proximal (coronary) and distal wall in the quarters, 2) foot is placed on the block the rotation of the block allows the proximal and distal wall in the heels, and 3) 2.0-2.5cm dorsal to foot to position itself naturally, influenced by the horse’s conforthe apex of the frog, will aid in the evaluation of quarter angles, mation, thereby alleviating the possibility of positional artifacts quarter wall height, heel angle and height, sole depth, and toe to such as joint space asymmetry. When designing or purchasing heel ratio. Marking the dorsal hoofwall becomes very useful in a positioning block it is important to take into consideration the height of the block and the center of the x-ray beam of your particular x-ray machine. Incorporating some type of metallic marker within the surface of the block is useful in aiding accurate identification of the ground surface, thus improving the accuracy of foot measurements. The lateromedial and horizontal dorsopalmar/plantar projections are the most useful views to perform when evaluating the foot for conformation and balance. Consideration of the area of interest, as well as having solid anatomical knowledge horses with upright feet, the best example being the club-footed of the horse’s foot is important when performing these radiohorse. As the foot grows out in these horses there is a propensity graphic views. for the dorsal wall to distort and flare, producing multiple angles When performing the lateromedial (L-M) projection for the to the dorsal wall. Radiographic evaluation of the dorsal wall purpose of evaluating foot balance and symmetry, the center with a conforming marker allows accurate assessment of the of the beam should be aimed 1.5-2.0 cm proximal to the weight distortion of the wall and true angle of the foot. bearing surface and midway between the toe and the heel; the It is crucial that the positioning of the patient, foot and x-ray beam angle should be parallel with the heel bulbs and the ground www.faep.net

The Practitioner 27

with “ideal” conformation, the articular surface of the distal phalanx is parallel to the ground, as is a line between the medial and lateral coronary band and, the medial and lateral walls are of equal thickness, and the distance from the medial and lateral solar margins surface.3,6 This beam alignment will produce a film that shows to the ground are similar.8 the medial and lateral solar margins and palmar processes of In horses with significant rotation or angulation in the distal the distal phalanx superimposed on one another (in the “normal” limb, the relation of the distal phalanx with the ground may not foot). Any obliquity in the image can be corrected by raising or be as symmetrical. Furthermore, the distal interphalangeal joint lowering the central beam to adjust for variation in sole depth, space should be approximately even across its width regardless of or adjusting the beam angle in relation to the heel bulbs. angulation of the phalanges. It is normal for the medial quarter The lateromedial projection is useful in evaluating the relation- wall to be at a slightly steeper angle and subsequently measure ship of the distal phalanx with the hoof capsule and distal limb shorter in length.8 However, caution in over interpretation of (hoof-pastern axis), location of breakover, shoe placement, and joint incongruency is recommended because any malpositioning quantitative parameters. Malalignment of the foot and pastern of the limb or foot can create the appearance of medial to lateral is seen in 72.8% of horses with forelimb lameness.7 Malalign- imbalance. ment of the medial and lateral solar margins is common with Quantitative methods of evaluating the horse’s foot have been imbalance or poor conformation, though many normal horses developed.9 Measurements obtained from the L-M and HD-P have some asymmetry of the distal surface of the distal phalanx. radiographic images have been used to evaluate the effects of Additionally, resorption and remodeling of the distal phalanx can trimming and shoeing,7,10,11 the stresses delivered to the deep alter the dorsal contour, solar margins and length of the distal digital flexor tendon when hoof angle is changed,12,13 the phalanx as well as alter the shape and angle of the solar margin, relationship between foot conformation and lameness1,14,15, and complicating interpretation. These changes are seen with lami- in thoroughbreds, the relationship between solar angle and DDFT nitis, pedal osteitis, and other sources of chronic inflammation injuries.12 Quantitative parameters that are commonly evaluated (heel bulb avulsions, osteomyelitis, etc). Investigation with the include the: 1) dorsal hoof wall angle (DHWA), 2) heel angle (HA), orthogonal view (HD-P) will help clarify any solar margin asym- 3) solar or palmar angle (SA), 4) dorsal hoof wall length (DHWL), metry seen in the L-M view. 5) dorsal hoof wall thickness (DHWT), 6) the sole depth (SD), 7) The Horizontal Dorsopalmar/Plantar (HD-P) view is also distance between the dorsal coronary band and the apex of the performed with the horse standing squarely on two positioning extensor process (CED), and 8) the distribution of the dorsal and blocks with the foot placed towards the back of the block. The palmar portions of the foot (T:F), separated by a line extending beam orientation is parallel to the dorsal-palmar/plantar long from the center of rotation of the distal interphalangeal joint, axis of the foot on the median plane of the foot. For consistency perpendicular to the weight bearing surface (Table 1). Subjective the x-ray beam is also centered 1.5-2 cm above the weight-bearing surface of the foot. Depending on the block surface and the horse’s conformation, using the dynamic rotary block may add additional accuracy to the interpretation of this image by alleviating any artifact produced by poor conformation or foot placement. This beam alignment will produce a film that projects the extensor process of the distal phalanx on the median plane of the second phalanx. Regardless of whether a unilateral or bilateral study is being performed, both feet should be placed on blocks of equal height. Correct positioning reduces the likelihood of artifactual changes to the joint space that might otherwise be interpreted assessment of a well taken radiograph is frequently adequate for as joint asymmetry and foot imbalance. evaluating the horse’s foot; quantitative assessment is useful in This projection allows evaluation of medial to lateral balance documenting changes in a foot over time and when comparing and conformation of the foot with observation and measurement feet on the same horse. of the medial and lateral wall length and angle, and the orientation Changes in the DHWA, SA, and disproportionate distribution of the distal phalanx within the hoof capsule. Orientation of the of foot mass in relation to the center of rotation can be appreciated distal phalanx can be assessed by measuring the distance from on the L-M projection and assesses the dorsopalmar balance of the articular surface of the distal phalanx to the ground surface; the foot. There is a wide range in what is considered normal for the solar canal can also be used as a reference point, but it is less the SA (2- 8o).1,7,10,12,16,17 Minimal decreases or flattening of the consistent. Using the solar margin as a point of reference can be SA and DHWA have been associated with lameness.1 An increase variable due to changes that can occur in the bone.8 In horses 28 The Practitioner

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in the solar angle decreases the DDFT force, and therefore, the a comprehensive scientific study to document all of these relaforce on the navicular bone; a one-degree increase in solar angle tionships, but between the studies that are available and clinical decreases the pressure on the navicular bone by 6%.14 At the experience, there is enough information to entertain a fruitful same time, changes in the SA or DHWA will result in changes in discussion on the subject. the hoof pastern axis. The center of rotation (COR) separates the foot mass into dorsal and palmar/plantar proportions. The COR References: 1. Dyson SJ, Tranquille CA, Collins SN, et al. An investigation of the is located midway between the dorsal and palmar/plantar aspects relationships between angles and shapes of the hoof capsule and the of the distal articulation of the middle phalanx; a line dropped distal phalanx. Equine Vet J 2011;43:295-301. 2. McKnight AL. Digital radiography in equine practice. Clin Tech Equine from this point and perpendicular to the weight-bearing surface Pract 2004;3:352- 360. divides the dorsal and 3. Redden RF. Radiographic imaging of the equine foot. Vet Clin North Am palmar/plantar foot Equine Pract 2003;19:379-392, vi. 4. Jimenez DA, Armbrust LJ. Digital radiographic artifacts. Vet Clin North mass. In the “normal” Am Small Anim Pract 2009;39:689-709. foot the T:F should 5. Jimenez DA, Armbrust LJ, O'Brien RT, et al. Artifacts in digital be between 60 and radiography. Vet Radiol Ultrasound 2008;49:321-332. 6. Little DR, Schramme M. Diagnostic imaging - Radiography and radiology 67%.7,18 If viewed from of the foot In: Floyd AE,Mansmann RA, eds. Equine Podiatry. St. Louis: the solar surface the Saunders-Elsevier Inc., 2007;141-159. widest point of the foot 7. Kummer M, Geyer H, Imboden I, et al. The effect of hoof trimming on radiographic measurements of the front feet of normal Warmblood horses. should correspond to Vet J 2006;172:58-66. the COR. Horses with 8. Parks A. The Foot and Shoeing In: Ross MW,Dyson SJ, eds. Dianosis long-toe, low-heel and Management of Lameness in the Horse. 2 ed. St. Louis: Elsevier, Saunders, 2011;282-302. syndrome usually have a 9. Cripps PJ, Eustace RA. Radiological measurements from the feet of low dorsal hoof wall and normal horses with relevance to laminitis. Equine Vet J 1999;31:427-432. solar angle, a long narrow frog, and disproportionate foot mass 10. Kummer M, Gygax D, Lischer C, et al. Comparison of the trimming procedure of six different farriers by quantitative evaluation of hoof with excessive mass dorsal to the center of rotation (> 67%). A radiographs. Vet J 2009;179:401-406. o solar angle of less than 2 is usually associated with a dorsopalmar 11. Van Heel MC, Moleman M, Barneveld A, et al. Changes in location of imbalance, the center of rotation of the DIP joint is displaced centre of pressure and hoof-unrollment pattern in relation to an 8-week shoeing interval in the horse. Equine Vet J 2005;37:536-540. towards the heels, resulting in an increase in the T:F ratio.8 12. Smith A, Dyson S, Murray R, et al. Is there an association between The DHWA, HA, SA, DHWL, SD, and T:F are changed or potendistal phalanx angles and deep digital flexor tendon lesions? Proc Am tially changed when the foot is trimmed and shod and results Assoc Equine Pract 2004;328-331. 13. Page BT, Hagen TL. Breakover of the hoof and its effect on structures in an overall change in the equilibrium and balance of the foot. and forces within the foot. J Eq Vet Sc 2002;22:258-264. Repeating the L-M projection following trimming and shoeing 14. Eliashar E, McGuigan MP, Wilson AM. Relationship of foot the foot is useful in evaluating the affects of the trim. conformation and force applied to the navicular bone of sound horses at the trot. Equine Vet J 2004;36:431-435. Radiography of the foot remains the most practical, economic, 15. Verschooten F, Roels J, Lampo P, et al. Radiographic measurement from and informative imaging modality in the field. Having said that, the lateromedial projection of the equine foot with navicular disease. Res the quality of the information gained from a radiograph is only Vet Sci 1989;46:15-21. 16. Linford RL, O'Brien TR, Trout DR. Qualitative and morphometric as good as the quality of the radiograph itself. Using high-quality radiographic findings in the distal phalanx and digital soft tissues of equipment, maintaining that equipment, and mastering radiosound thoroughbred racehorses. Am J Vet Res 1993;54:38-51. graphic technique and image acquisition are imperative to obtain17. Parks A. Form and function of the equine digit. Vet Clin North Am Equine Pract 2003;19:285-307, v. ing quality information. Depending on the information desired 18. O'Grady SE. Radiographs for the farrier, 2003;1-3. from a radiographic study, a limited number of views are required. Based on the information gained from the standard study and the clinical presentation of the case, there are numerous other Randy B. Eggleston, DVM, DACVS Clinical Associate Professor, Large Animal Surgery specialty views and techniques that can be performed to gain College of Veterinary Medicine additional information. As stated previously, a detailed lameness University of Georgia, Athens, GA examination is also required to guide the practitioner in deciding ■ Received his DVM from Kansas State University, College of what radiographic views should be taken. Radiography is also Veterinary Medicine very useful in more thorough evaluation of the sound horse’s ■ Interned at the University of Georgia, College of Veterinary foot for consultation with the farrier with respect to trimming Medicine from 1995 – 1996. and shoeing protocols. Although DR has improved the ability to ■ Completed surgery residency at the University of Georgia, 2001 visualize and evaluate some of the soft tissue structures within ■ Joined the faculty of the University of Georgia as a Clinical the foot, there remain great limitations to imaging most soft Assistant Professor, 2002 tissue structures within the foot. ■ Diplomate, American College of Veterinary Using radiographs to assess the relationship between the hoof Surgeons, 2003 and the underlying osseous structures as an aid in assessing foot Dr. Eggleston’s clinical interests include balance, is about developing an understanding of the relationgastrointestinal surgery, minimally invasive ships between the position of the hoof capsule, the angle of the surgery, and orthopedic surgery. He also distal phalanx within the hoof capsule, the symmetry of the interhas a strong interest in equine lameness and phalangeal articulations, and the alignment of the phalangeals. diagnostic imaging. It should be mentioned as a caveat at the outset that there isn’t www.faep.net

The Practitioner 29

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30 The Practitioner

Issue 3 • 2013

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