Standing MRI Lesions Identified in Jumping andDressage Horses With Lameness Isolated to theFoot

Richard D. Mitchell, DVM; Ryland B. Edwards III, DVM, PhD, Diplomate ACVS;Lynsey D. Makkreel, DVM; and Traci D. Oliveira, CVT

Lameness diagnosis with the standing magnetic resonance imaging scanner can reveal previouslyundetectable lesions that contribute to foot pain. Jumping and dressage horses are subject toparticular stresses that may result in unique injuries and conditions. This paper reviews the lesionsidentified in 98 jumping and dressage sport horses over an 18-mo period and provides an indicationof response to specific clinical treatment of cases 6 mo after examination. Authors’ address: Fair-field Equine Associates, P.C., 32 Barnabas Road, Newtown, CT 06470; e-mail:Rmitch2074@aol.com. © 2006 AAEP.

1. Introduction

Foot pain is a common source of lameness in jump-ing and dressage horses. While the principles ofperineural and intra-articular anesthesia have longallowed veterinarians to localize the source of footpain,1 the determination of the specific cause hasoften proven elusive. Newer imaging techniques ofdigital radiography, nuclear scintigraphy, and ultra-sound have further enhanced the ability of the ex-aminer to identify the cause of lameness. The verynature of the equine foot limits the practical appli-cation of many imaging modalities. Magnetic res-onance imaging (MRI) has proven to be a valuabletool for identifying specific pathology in the equinefoot,2 and many of these lesions have been corrobo-rated with anatomical and histopathologicalstudies.3

As MRI technology has advanced in human clini-cal medicine, many imaging devices have become

available for use in the horse. Closed and openmagnets, both of the low-field and high-field type,are now available and affordable for use in equineclinical practice. Most MRI systems require thehorse to be anesthetized to fit within the field of themagnet. More recently, a low-field standing MRIhas been developed and is now in widespread use inEurope and the United States. Motion can have asignificant effect on image quality, and whereas gen-eral anesthesia may eliminate motion artifact, ade-quate sedation techniques and motion correctionsoftware are now available. The necessary equip-ment and specific concerns of general anesthesiaand recovery are eliminated by using a standingscanning device.

As the use of MRI is becoming more commonplace,many apparent lesions and abnormalities are beingidentified in the equine foot. Several excellent re-views of MRI lesions have been published.4 Thepopulation of horses in these reviews has been some-

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NOTES

what mixed. A review of the more common lesionsspecifically seen in jumping and dressage horses asseen with a standing MRI scanner has not beenpublished. The purpose of this paper is to reviewthe more common lesions seen in jumping and dres-sage horses in the northeastern United States pre-sented for a complaint of foot-related lameness andimaged with a standing low-field MRI scanner.Additionally, an indication of responses to treat-ment of the identified lesions is provided.

2. Materials and Methods

All horses in this review were examined at FairfieldEquine Associates, P.C. (FEA) in Newtown, CT, be-tween October 2004 and May 2006. The horses inthis review were restricted by discipline to sporthorses participating in show jumping or dressage.Lameness cases included regular patients of thepractice and referrals for specific imaging tech-niques and case work-up. Cases for MRI wereidentified by those showing resolution of lamenessby palmar (plantar) digital or abaxial sesamoidnerve blocks, thus limiting the lameness to struc-tures distal to the fetlock. Routine lameness eval-uation, nerve blocks, ultrasound, and radiographshad failed to elucidate the specific source of thelameness in all cases. A total of 98 horses wereincluded in this review. Thirty horses were alsoevaluated with nuclear scintigraphy before or afterMRI. MR imaging was accomplished using a low-field, fixed, 0.27-T unit for use in the standinghorse.a

Use of the standing MRI scanner has been de-scribed previously.5 Cases at FEA were sedated byvarious techniques of bolus sedation and constantintravenous drip using combinations of detomidineb

and butorphanol.c A radiofrequency receiving coilwas placed on the foot to be imaged, and the magnetwas positioned in a manner that placed the footcentrally within the magnetic field. Pilot scans ofshort duration were performed to determine properpositioning and for purposes of establishing properangle for the scanning sequences. Movement of thehorse during the scanning sequences resulted in theneed for new pilot scans to re-establish proper posi-tion. A standard protocol for foot imaging was usedthat included gradient echo T1-weighted, fast spinecho T2-weighted, and short time inversion recovery(STIR) sequences in sagittal, transverse, and frontalplanes. Both feet of the horse were typicallyscanned, and protocol demanded that lesions werefound in more than one plane to be considered valid.Typically, the contra-lateral limb was compared forsymmetry.

After diagnosis, a portion of the horses weretreated at FEA, whereas some returned to the refer-ring veterinarian for therapy. Therapy includedcorrective shoeing, rest, injection of the distal inter-phalangeal (DIP) joint, injection of the navicularbursa, intravenous tiludronate, and short-termphenylbutazone (2.0 mg/kg/day) depending on the

individual diagnosis and duration of lameness.Pentoxifylline (8.0 mg/kg, q 12 h) or isoxsuprine (1.0mg/kg, q 12 h) was prescribed in a limited number ofcases. Focused extracorporeal shockwave therapyd

was used on selected DDF tendon core lesions.Tiludronatee was administered for apparent navic-ular bone inflammation at a dose of 1.0 mg/kg di-luted in 1 l of saline and given as a slow infusionover 90 min.6 The navicular bursa was injectedunder fluoroscopic guidance with a combination of tri-amcinolonef (6 mg) and sodium hyaluronateg (22 mg);a total volume of 3 ml was used.7 The same combi-nation of medications was used for treatment of DIPjoint synovitis in relatively acute cases. Other casesof DIP synovitis deemed to be more chronic weretreated with IRAPh per manufacturer’s instructions.Owner preference and economic considerations af-fected choice of therapeutics in some cases.

Those horses �6 mo from time of examinationwere assessed for soundness by veterinary examina-tion or owner/trainer reports. Information was col-lected on the age and use of all horses examined,predominantly affected lame limb, combinations oflesions, duration of lameness before MRI examina-tion, and percentage of horses that returned tosoundness.

3. Results

A total of 98 sport horses were examined with thestanding MRI scanner between October 2004 andMay 2006. Nuclear scintigraphy was performed on30 horses of this group. Breed distributions wereas follows: Warmblood, 70; Quarter Horse andQuarter Horse cross, 9; Thoroughbred, 6; Thorough-bred cross, 7; various other breeds, 6. There were 69geldings, 26 mares, and 3 stallions. The mean ageof all horses examined was 10.7 yr (range, 4–24 yr).The mean duration of lameness before MRI scan was33 wk (range, 1 wk to 4 yr). Seventy-seven horseswere training in jumping disciplines, and 21 horseswere training in dressage.

Fifty-seven (58%) of the horses had a primarycomplaint of right front limb lameness; 39 horses(40%) were primarily lame in the left front limb,with 2 horses (2%) having complaints of hind footlameness. More specifically, the trend toward rightfore lameness was even greater in jumpers with 46right fore (RF) (60%) and 29 left fore (LF) (38%) asopposed to dressage horses that showed a muchmore balanced distribution of 11 RF (52%) and 10LF (48%).

Abnormal findings in the navicular bone were themost common lesions identified, appearing in 75horses (77%). Navicular bone lesions included fluidsignal within the body of the navicular bone, sclero-sis, contour defects, cyst-like defects, and fragmen-tation (Figs. 1 and 2). DIP joint effusion (Fig. 3)was observed in 67 horses (68%). Deep digitalflexor (DDF) tendon lesions of various locations anddimensions were diagnosed in 64 horses (64%).Lesions of DDF tendons included evidence of tendon

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thickening and distortion of shape, fluid signal, mar-gin changes such as fibrillation, core lesions, andother evidence of significant fiber pattern disruption(Fig 4). Navicular bursitis was noted in 48 horses(49%). Bursitis was identified as increased fluidsignals from the region of the bursa and evidence of

synovial proliferation (Fig. 5). In contrast to a pre-vious presentation regarding Warmblood horseswith foot lameness,8 desmitis of the medial and lat-eral collateral ligaments of the distal interphalan-geal joint was only identified in 21 horses (21%).Other abnormalities identified included desmitis ofthe navicular collateral ligament (n � 13), impar

Fig. 1 T2*W 3D Trans HR image showing focal core lesionswithin the medial (arrow) and lateral lobes of the deep digitalflexor tendon (DDFT).

Fig. 2. STIR FSE SAG image showing coffin joint effusion in thedorsal (arrow) and the palmar compartments.

Fig. 3. STIR FSE SAG showing fluid signal within the spongio-sum and compact bone of the navicular bone.

Fig. 4. T1W 3D SAG HR showing a cyst-like defect (arrow) inthe flexor surface of the navicular bone.

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ligament injury (n � 4), pedal bone fracture (n � 2),and subchondral cyst of P2 (n � 2).

Fluid signal of the navicular bone was often seenconcurrently with other lesions.9 Of those withfluid signal (or cyst-like lesion) from the navicularbone (75 horses), 61 horses (81%) had DDF tendonlesions, 48 horses (64%) had navicular bursitis, and40 horses (53%) had DIP joint effusion. Twenty-five horses (26% of the total population) had concur-rent DDF tendon lesions and DIP joint effusion.

Of the 30 horses examined with nuclear scintig-raphy, 26 showed increased uptake of radioisotopein the region of the navicular bone, which corre-sponded with abnormalities indicated on MRI.Eight horses also showed increased uptake of radio-isotope at the insertion of the DDF tendon and sub-sequently had indication of tendonitis on MRI.

Sixty-six horses were �6 months after examina-tion at the time of review. Soundness was assessedas a successful return to function in the same orrelated activity before injury. Forty-four of 66horses (67%) were sound and in work, 17 (26%) werestill lame, 3 (4%) had undergone palmar digitalneurectomy and were functioning as before, and 2horses (3%) were lost to follow-up. Twenty-nine of46 horses (63%) affected with navicular bone lesionswere sound and in work. Fifteen of 23 horses (65%)with coffin joint effusion were reported sound.Twenty-five of 48 horses (52%) affected with DDFtendon lesions were sound and had returned towork. Sixteen of 24 horses (67%) with evidence ofnavicular bursitis were reported sound. Of 10horses diagnosed with desmitis of the DIP collateral

ligaments, 8 (80%) were sound after 6 months ormore.

Corrective shoeing was recommended in all casesof foot lameness. Corrective shoeing primarily con-sisted of improving hoof-pastern axis (normally cor-recting a broken back axis) and medial to lateralbalance. Egg bar shoes were used most often forDDF tendon injuries. Rest involved stall rest ini-tially for 30–60 days and then confinement to asmall “medical paddock” that discouraged vigorousactivity for at least another 2 mo. Sixteen horseswere treated with a brief course of phenylbutazone,corrective shoeing, and rest. Eight horses (50%) somanaged were reported sound at 6 mo. Ten horsesthat showed navicular lesions were treated with ti-ludronate, corrective shoeing, and rest; of these, 8(80%) were reported sound at 6 mo. The navicularbursas were injected in 10 horses (in addition toshoeing recommendations) as therapy for navicularbone inflammation, navicular bursitis, and tendoninflammation in the region adjacent to the navicularbone. Of those treated, seven horses (70%) werereported sound after 6 mo. Sixteen of 20 horses(80%) treated concurrently with intravenous tilu-dronate and injections of the navicular bursa werereported sound in the same time period. Twohorses were treated with injection of the DIP jointfor synovitis: one with triamcinolone and sodiumhyaluronate and one with IRAP. These two casesof synovitis were reported to be sound after 6 mo.Three horses were treated for core lesions of theDDF tendon with focused shockwave therapy (in aneffort to reduce lesion size),10 corrective shoeing, andrest. These three horses were all reported sound at6 mo.

4. Discussion

Foot pain is a major source of lameness in the jump-ing and dressage horse and may be related to thenature of the repetitive work performed in jumpingand extended gaits. New diagnostic techniqueshave allowed veterinarians to more precisely locatethe source of pain, yet the physical structure of theequine foot limits imaging techniques for preciseidentification of causative lesions. MRI has beenshown to solve many of the physical problems en-countered with ultrasound, radiography, and scin-tigraphy.4,8 The standing MRI scanner providesconsiderable insight for the diagnosis of foot pain inthe sport horse. While the low-field magnet mayhave less resolution compared with a high-field mag-net, images have proven very satisfactory whileavoiding some of the issues associated with generalanesthesia. General anesthesia can be very laborintensive, may pose some risk for the horse, andincreases the expense for some examinations. Be-cause the horse is fully load bearing, the standingscanner provides anatomical correctness that maybe distorted by general anesthesia and recumbency.The quality of images from the standing scanner is

Fig. 5. STIR FSE TRA showing effusion (arrow) localized to themedial aspect of the navicular bursa.

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most seriously affected by incorrect positioning ofthe horse and movement during imaging.

Lesions of the navicular bone are common injumping and dressage sport horses exhibiting distallimb pain. The incidence of navicular bone lesionsin our review was far greater than has been previ-ously reported in other groups. While evaluatorbias may have affected some results, the populationof horses may have been pre-selected by referringveterinarians to likely include such cases. MRIwas performed on many of these horses to confirmsuspicions of navicular bone involvement. Nuclearscintigraphy had indicated increased radioisotopeuptake in the navicular bones of 26 of 30 horsesexamined (87%). The authors speculate that mildfluid signal from the navicular bone in jumping anddressage horses may be a feature of stress remodel-ing and not necessarily a sign of profound patholo-gy.11 Because of the frequent presence of otherlesions, the navicular bone abnormalities seen maynot have been the root cause of the lameness noted,yet could not be ignored in a diagnostic review.DDF tendon lesions are very common in thosehorses diagnosed with foot pain and often accom-pany navicular bone abnormalities. Navicularbone inflammation is often seen concurrently withnavicular bursitis and DIP joint effusion. DIP jointeffusion less commonly accompanies DDF lesions.The DIP effusion apparent in some images may be afunction of weight bearing and might not be as evi-dent in a scan performed under general anesthesia.It is very apparent from this study that palmar footpain is a syndrome involving multiple lesions in themajority of cases.

The results of this review suggests that DDF ten-don lesions respond positively to rest, correctiveshoeing, and medical therapies directed specificallyat the pathology identified on MRI. The percentageof horses that returned to soundness in this groupwas greater than previously reported for horses withsimilar lesions.4 This may be related to duration oflameness before examination, the severity of theinjuries most frequently encountered by jumpingand dressage sport horses, and the select populationof horses included in this review.

The limited number of horses treated with eithertiludronate or injection of the navicular bursa indi-cates an encouraging outcome for treatment of na-vicular bone inflammation and navicular bursitis,respectively. Our results suggest that combiningthe two techniques may prove useful in more seriouscases involving significant inflammation in the twostructures.

Foot pain in jumping and dressage sport horsesoriginates from a variety of sources. After localiza-tion of the pain to the foot, standing MRI can pre-

cisely define the anatomical structures withpathology and assist the attending veterinarianwith developing more specific therapy for the horse.

This paper was reprinted with permission fromthe American College of Veterinary Surgeons.

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4. Dyson SJ, Murray R, Schramme MC. Lameness associatedwith foot pain: results of magnetic resonance imaging in 199horses (January 2001-December 2003) and response to treat-ment. Equine Vet J 2005;37:113–121.

5. Mair TS, Kinns J. Deep digital flexor tendonitis in theequine foot diagnosed by low field magnetic resonance imag-ing in the standing patient: 18 cases. Vet Radiol Ultra-sound 2005;46:458–466.

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8. Martinelli MJ, Rantanen NW. Relationship between nu-clear scintigraphy and standing MRI in 30 horses with lame-ness of the foot, in Proceedings. 51st Annual AmericanAssociation of Equine Practitioners Convention 2005;359–365.

9. Busoni V, Heimann M, Trenteseaux J, et al. Magnetic res-onance imaging findings in the equine deep digital flexortendon and distal sesamoid bone in advanced navicular dis-ease: an ex vivo study. Vet Radiol Ultrasound 2006;47:279–286.

10. Kersh KD, McClure S, Evans RB, et al. Ultrasonographicevaluation of extracorporeal shock wave therapy on collage-nase-induced superficial digital flexor tendonitis, in Proceed-ings. 50th Annual American Association of EquinePractitioners Convention 2004;257–260

11. Schneider RK, Gavin PR, Tucker RL. What MRI is teachingus about navicular disease, in Proceedings. 49th AnnualAmerican Association of Equine Practitioners Convention2003;210–219.

aHallmarq Equine Limb MRI scanner, Hallmarq VeterinaryImaging Ltd., Surrey, United Kingdom GU4 7WA.

bDormosedan, Pfizer Animal Health, Exton, PA 19341.cTorbugesic, Fort Dodge Animal Health, Fort Dodge, IA 50501.dSanuWave, Inc., Marietta, GA 30062.eTildren, CEVA Sante Animale, Libourne, France BP 126 –

33501.fVetalog, Fort Dodge Animal Health, Fort Dodge, IA 50501.gHyvisc, Anika Therapeutics, Woburn, MA 01801.hIRAP, Arthrex Biosystems, Bonita Springs, FL 34134.

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