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LUCIA CARRIE.SMOKE N HONEY.1 31 May 2016

Diagnosis and Management of Palmar Foot Pain

Tracy A. Turner, DVM, MS, Dipl. ACVS

Take Home Message:            The diagnosis of palmar foot pain is based on a thorough examination that differentiates various types of pain emanating from the foot. Management is based on shoeing to improve hoof biomechanics and therapy aimed at the results of diagnostics.

Introduction: The palmar digital nerve block has traditionally been described as desensitizing the palmar one-third to one-half of the foot.1-3 But we know that the nerve block desensitizes much more including the coffin joint, most of the distal phalanx, and the sole of the hoof. 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 their 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 a 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 the 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 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 have been shown to overlap. The DIP joint and podotrochlear bursa do not communicate, and yet the results of injecting anesthetic into these synovial cavities is 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 showed 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 horse 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 desensitisized 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 should be noted,  podotrochlear bursa injection can be difficult compared to the DIP joint which is easier. We have found that not only is radiographic control necessary to successfully perform podotrochlear bursa injection 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 Injection into the bursa was made from the palmar surface with the limb flexed at the carpus. Injection into the bursa was made from the palmar surface with the limb flexed at the carpus. 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 palmaroproximal–palmarodistal (PP-PD) 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 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 twelve 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. To date, we have had no complications to the podotrochlear bursa injection.

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 hyper echoic line.7 The bursa is seen as a hypo echoic (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 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 this 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 in 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 the 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 effected by NRP and 46% by other sources of PHP.5 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 has a positive bone scan indicating that the navicular bone may be involved in a complex problem of heel pain.

A 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 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, in the author’s opinion, correct shoeing should be the basis of all treatment. Furthermore, 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 pre-existing 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 insure 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 broken-back, 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 the author’s experience the change is limited to 5-7º change. 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 horses.15 The necessity of correcting underrun heels has been well documented. The author’s experience has shown, 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 dorso-palmar 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.12 One study identified small feet as an indicator of poor prognosis in the treatment of navicular syndrome.15 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.15 This was done to get a rough idea of the hoof 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 their 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 the lameness. However, 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, 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; these cases should be treated for inflammation of that joint. This may include systemic non-steroidal anti-inflammatory therapy but intra-articular therapy or specific joint therapy should be considered.10 The use of hyaluronic acid or corticosteroids as anti-inflammatories within the joint is well reported in the literature and are often combined. In addition, the use of intra-articular or intramuscular polysulfated glycosaminoglycans has been useful in the control of joint disease.3 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’s lameness is exacerbated by medial/lateral wall wedge tests I suspect distal interphalangeal collateral desmitis. I will exam the collaterals sonographically to determine if desmitis is present. If desmitis is present the joint is treated differently. In the author’s opinion, 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 by the author 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 is treated by intramuscular polysulfated glycosaminoglycans. In the author’s opinion, tears in the bursa need to be treated with rest; however, persistent pain in this region has been a problem.

It has been suggested that blood flow may play a role in some types of palmar foot pain and these cases 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.

When desmitis of the navicular suspensory ligament or impar ligament is suspected there are basic 2 treatment alternatives.3 Treatment is designed to reduce strain on the ligament. This can be achieved by either raising the heels of the horse’s foot or by cutting the collateral sesamiodean ligaments (CSL). Collateral sesamoidean desmotomy  is a surgery that has become popular in Europe and has been effective on selected cases of navicular syndrome.3

Similarly, when the deep flexor tendon is involved, raising the heels of the hoof will decrease strain on the tendon.3 But in addition, desmotomy of the inferior check ligament has also recently been shown to be effective in treatment of these cases. But if tendonitis is diagnosed the tendon needs to be rested. With the new regenerative medicine, tendons certainly can be aided in their healing by PRP or stem cell injections. Shockwave therapy has also been used in these cases.

If shockwave therapy is to be used, the foot must be clean of debris (soaking the foot is preferred for optimal energy transmission) and trim the hair in the area of treatment, wipe skin with alcohol, and apply the ultrasound gel to the area of treatment.13 When treating through the frog, trim outer layers so the frog is soft. If you can get an ultrasound image through the frog, then shock waves will also penetrate there. The author uses two thousand shocks at the highest energy setting using the 5 mm or 20 mm trodea depending on the depth of the lesion: for Navicular Syndrome, deliver energy at the hairline over the palmar pastern and/or over the frog, for collateral ligament desmitis, deliver 1,000 pulses over the injury and the remaining 1,000 shocks over the joint, for  deep flexor tendon injuries, navicular bursa, edema, cartilage erosion, cystic lesions, and adhesions, focus the energy over the center of the injury. Post-treatment protocol, advise the client to begin walking or working the horse beginning immediately after treatment. Repeat the treatment in 3 weeks and walk the horse during the healing process. In the author’s opinion, staying in the stall does more harm than good. 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 abnormal stresses on soft tissues and could delay healing.

In long standing cases of navicular pain, excessive remodeling of the navicular bone can be a problem. In these cases, tiludronate, in one report, was used effectively to treat the disease.14 Dosage is either 0.1mg/kg administered slowly intravenously daily for 10 consecutive days or 1mg/kg administered slowly intravenously once. There are reports of veterinarians using the 0.1mg/kg dose as a regional perfusion, there is no scientific evidence that this is an effective administration of the drug.

When all other treatments have failed or have not had the desired affect, palmar digital neurectomy remains a viable treatment alternative.10 Numerous techniques are available but the author follows some basic rules. First, the neurectomy will not improve the lameness any more than a palmar digital nerve block. Therefore, it is highly recommended that the nerves be anesthetized with the owner/rider present so that they can decide whether the horse has sufficiently improved. Second, neuromas are a common problem but can be avoided by atraumatic surgical technique. Atraumatic surgery can really only be learned by practice. Neuroma formation can be decreased by allowing the surgical wounds 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.

 

References

  1. Turner TA: Diagnosis and treatment of the navicular syndrome in horses. in Yovich JV (ed): The Equine Foot, Vet Clin of NA: Eq Prac, Philadelphia, WB Saunders Co, 1989: 131-144.
  2. Turner TA, Fessler JF: The anatomic, pathologic and radiographic aspects of navicular disease. Comp Cont Ed, 4(8): S350-S355, 1982.
  3. Turner TA. Caudal hoof lameness, in Floyd AE and Mansmann RA: Equine Podiatry. Saunders-Elsevier, St. Louis, 2007, 294-312.
  4. Turner TA: Predictive value of diagnostic tests for navicular pain. In Proceedings 42nd Annual Meeting Am Assoc Eq Pract, 1996; 42: 201-204.
  5. Turner TA, Kneller SK, Badertscher RR, Stowater JL: Radiographic changes in the navicular bones of normal horses. in Proceedings 32nd Annual Meeting of Am Assoc of Equine Pract, 1986; 32: 309-314.
  6. Turner TA: Use of navicular bursography in 97 horses. in Proceedings 44th Annual Meeting Am Assoc Eq Pract, 1998; 44: 227-229.
  7. Sage AM, Turner TA: Ultrasonography of the soft tissues of the equine foot. Eq Vet Educ, 2002; 4: 278-283.
  8. Turner TA, Fessler JF, Lamp M, Pearce JA, Geddes LA: Thermographic evaluation of horses with podotrochlosis. Am J Vet Res 1983; 44(4):535-539.
  9. Dyson SJ. Subjective and quantitative scintigraphic assessment of the equine foot and its relationship with foot pain, Eq Vet J 2002; 34: 164-170.
  10. Trotter GW: Therapy for navicular disease. The Compendium on Cont Ed, 1991;13: 1462-1465.
  11. Colles CM. Navicular disease and its treatment. In Prac 1982; March: 29-35.
  12. Turner TA. Navicular disease management: shoeing principles, in Proceedings. 32nd Annu Conv Am Assoc Equine Practnr 1986; 32: 625-633.
  13. McClure S, Evans BE, Miles KG, et al. Extracorporeal shock wave therapy for treatment of navicular syndrome, in Proceedings Annual Meeting Am Assn of Equine Pract 2004; 50: 316-319.
  14. Denoix, J.M., Thibaud, D. and Riccio, B. (2003) Tiludronate as a new therapeutic agent in the treatment of navicular disease: a double-blind placebocontrolled clinical trial. Equine vet. J. 35, 407-413.
  15. Turner TA: How to subjectively and objectively examine the equine foot, in Proceedings Annual Meeting An Assn of Equine Pract 2006; 52: 531-537.

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