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  • How to Interpret Radiographs of the Carpus andTarsus of the Young Performance Horse

    Elizabeth M. Santschi, DVM, Diplomate ACVS

    Authors address: Department of Veterinary Clinical Sciences, The Ohio State University, 601Vernon L. Tharp Street, Columbus, OH 43210; santschi.5@osu.edu. 2013 AAEP.

    1. Introduction

    Routine radiographic evaluation of young perfor-mance horses has become commonplace in Thor-oughbreds but also occurs in other performancebreeds. This practice has resulted in the frequentdiscovery of radiographic abnormalities (RA) thatare often clinically silent but can cause concern inbuyers and sellers of young performance stock.The prevalence of radiographic developmental or-thopedic disease in 6-month-old horses has been re-ported to be 25% in Warmbloods, 41% inStandardbreds, and 34% in Thoroughbreds.1 InThoroughbred yearlings intended for racing, 86.3%exhibit RA2; in young Standardbreds, 42%3; in year-ling Warmblood horses, 69.5%4; and in 1- and2-year-old Quarter Horses intended for cutting,89%.5 Predicting the significance of RA to futureperformance can be challenging and frustrating forbuyers and sellers, which is further complicated bythe possibility of treatment, including surgery, onprognosis.

    2. Identifying RA

    Because radiographic images are reviewed in sets ofprojections of one joint, this paper will discuss ab-normalities by each projection. Examiners are re-sponsible for reading the entire image; however,

    there are areas that are more commonly affected byRA, and they should receive the closest scrutiny.These will be denoted by black circles on the radio-graphic images included in these proceedings. RAbest detected on a specific projection will be listed inbold, but should be confirmed on other projectionswhen possible. Finally, readers should always con-sider three general factors when reviewing radio-graphic images:

    (1) Make sure that the films are of the correcthorse.

    (2) Make sure the date is appropriate andconsistent.

    (3) Make sure all required views are present andof acceptable quality.

    3. Carpus

    Most radiographic abnormalities in the carpus ofyoung horses can be imaged on three projections:dorsolateral (35) to palmaromedial oblique, dorso-medial (25) to palmarolateral oblique, and flexedlateral to medial. A skyline of the distal row canadd information if injury to the dorsal surface of thecarpal bones is suspected. At Thoroughbred sales,this view is used only for horses that have raced andis not routine for younger stock. Traditional de-scriptions of carpal views also include a dorsopalmar

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    HOW TO TAKE AND INTERPRET RADIOGRAPHS OF THE YOUNG PERFORMANCE HORSE

    NOTES

  • and standing lateral projection, but, in the interestof controlling cost and radiation exposure, are notincluded in sale radiographs.

    Dorsolateral (35) to Palmaromedial ObliqueProjection of the Carpus (Fig. 1).The areas of greatest concern on this view arethe dorsomedial aspect of the distal radius and theproximal radial, distal radial, and proximal thirdcarpal bones. The radial articulation of the acces-sory carpal bone, the palmar aspect of the ulnarcarpal bone, and the palmar pouch of the middlecarpal joint are also of interest.

    Abnormalities best identified on the dorsolateral(35) to palmaromedial oblique are listed below. Ifthe RA is in bold type, it is the best projection todetect that RA.

    (1) Osteochondral fragments or remodelingof the distal radial carpal bone

    (2) Osteochondral fragments or remodelingof the proximal third carpal bone

    (3) Osteochondral fragments or remodelingof the distomedial radius

    (4) Osteochondral fragments or remodeling of theproximal radial carpal bone

    (5) Fractures of the radial articulation of the ac-cessory carpal bone

    (6) Palmar fragments in the middle carpal joint(7) Ulnar carpal bone lucencies or axial fragments

    Dorsomedial (25) to Palmarolateral ObliqueProjection of the Carpus (Fig. 2).The areas of greatest concern on this view arethe dorsolateral aspect of the distal radius and theproximal intermediate, distal intermediate, andproximal third carpal bones. The ulnar carpal boneand the palmar pouch of the middle carpal joint arealso of interest.

    Abnormalities best projected on the dorsomedial(25) to palmarolateral oblique projection of the car-pus are listed below. If the RA is in bold type, it isthe best projection to detect that RA.

    Fig. 1. Carpus dorsolateral (35) to palmaromedial oblique pro-jection. This image demonstrates remodeling of the distal radialand proximal third carpal bones (white circle). This radiographwill be discussed by the panel as Case 1.

    Case Prognosis Summary

    Case 1. Remodeling of the Distal Radial and Proximal Third CarpalBones

    PerformanceGoal

    SurgeryYes/No/Maybe

    ExcellentPrognosis

    GoodPrognosis

    GuardedPrognosis

    PoorPrognosis

    Racing Yesowner/buyer

    Westernperformance Yes

    owner/buyer

    Englishperformance Yes

    owner/buyer

    Generalpurpose Yes owner buyer

    Case Prognosis Summary

    Case 2. Remodeling of the Distal Intermediate Carpal Bone

    PerformanceGoal

    SurgeryYes/No/Maybe

    ExcellentPrognosis

    GoodPrognosis

    GuardedPrognosis

    PoorPrognosis

    Racing Noowner/buyer

    Westernperformance No

    owner/buyer

    Englishperformance No

    owner/buyer

    Generalpurpose No

    owner/buyer

    Fig. 2. Carpus dorsomedial (25) to palmarolateral oblique pro-jection. This image demonstrates remodeling of the distal inter-mediate carpal bone (white circle). This radiograph will bediscussed by the panel as Case 2.

    380 2013 Vol. 59 AAEP PROCEEDINGS

    HOW TO TAKE AND INTERPRET RADIOGRAPHS OF THE YOUNG PERFORMANCE HORSE

  • (1) Osteophytes on the proximal intermedi-ate carpal bone

    (2) Osteophytes or remodeling on the distalintermediate carpal bone

    (3) Osteochondral fragments from the disto-central radius or proximal intermediate car-pal bone

    (4) Osteochondral fragments from the prox-imal third carpal bone

    (5) Osteochondral fragments from the plamar as-pect of the radial carpal bone

    Flexed Lateral to Medial Projection of theCarpus (Fig. 3).The areas of greatest concern on this view arethe proximal dorsal margin of the radial and inter-mediate carpal bones, the distal dorsal margin of theradial and intermediate carpal bones, the proximaldorsal margin of the third carpal bone, and the cau-dal aspect of the distal radius.

    Abnormalities best projected on the flexed lateralto medial projection of the carpus are listed be-

    low. If the RA is in bold type, it is the best projec-tion to detect that RA.

    (1) Osteochondral fragments or remodelingof the distal radial carpal bone

    (2) Osteochondral fragments or remodelingof the distal intermediate carpal bone

    (3) Osteochondral fragments or remodelingof the proximal third carpal bone

    (4) Osteochondroma formation on the cau-dal radius

    Carpal abnormalities that are believed to affectlater athletic performance are not common and aregenerally reported to have a 7% prevalence insales yearlings (Table 1). Lucencies in the ulnarcarpal bone are detected with greater frequency butare generally considered insignificant blemishes.

    Fig. 3. Carpal flexed lateral to medial projection. This imagedemonstrates a small osteochondroma on the caudal radius(white circle). This radiograph will be discussed by the panel asCase 3. Fig. 4. Tarsal dorsomedial (65) to plantarolateral oblique pro-

    jection. This image demonstrates a DIRT lesion composed ofmultiple fragments (white circle). This radiograph will be dis-cussed by the panel as Case 4.

    Case Prognosis Summary

    Case 3. Small Osteochondroma on the Caudal Distal Radius

    PerformanceGoal

    SurgeryYes/No/Maybe

    ExcellentPrognosis

    GoodPrognosis

    GuardedPrognosis

    PoorPrognosis

    Racing Noowner/buyer

    Westernperformance No

    owner/buyer

    Englishperformance No

    owner/buyer

    Generalpurpose No

    owner/buyer

    Case Prognosis Summary

    Case 4. DIRT Lesion With Multiple Fragments

    PerformanceGoal

    SurgeryYes/No/Maybe

    ExcellentPrognosis

    GoodPrognosis

    GuardedPrognosis

    PoorPrognosis

    Racing Yesowner/buyer

    Westernperformance Yes

    owner/buyer

    Englishperformance Yes

    owner/buyer

    Generalpurpose Maybe

    owner/buyer

    AAEP PROCEEDINGS Vol. 59 2013 381

    HOW TO TAKE AND INTERPRET RADIOGRAPHS OF THE YOUNG PERFORMANCE HORSE

  • 4. Tarsus

    Similar to the carpus, most radiographic abnormal-ities of the tarsus of young horses can be imaged on

    three projections: dorsomedial (65) to plantarolat-eral oblique, dorsolateral (10) to plantaromedial,and lateral to medial. Traditional descriptions oftarsal views include a lateral to medial oblique pro-

    Fig. 5. Tarsal dorsolateral (10) to plantaromedial projec-tion. This image demonstrates mild tarsocrural effusion (whitearrows) and a large medial malleolar lucency with fragments (whitecircle). This radiograph will be discussed by the panel as Case 5.

    Fig. 6. Tarsal lateral to medial projection. This image demon-strates a large enthesophyte on MT3 at the dorsal margin of thetarso-metatarsal joint and another on the distal aspect of themedial trochlear ridge (white circle). This radiograph will bediscussed by the panel as Case 6.

    Table 1. Prevalence of Carpal Radiographic Abnormalities in Young Performance Horses

    Carpal Radiographic Abnormality Breed Prevalence Reference

    Fragment Thoroughbred 0.72.2% 2, 5, 8Osteophytes Thoroughbred 1.13.3% 2, 68Osteophytes Quarter Horse 3.5% 9Enthesophyte Thoroughbred 2.6% 2Ulnar carpal bone lucency Thoroughbred 8.322.2% 2, 6, 7Dorsomedial carpal disease Thoroughbred 2.7% 6Dorsomedial carpal disease Quarter Horse 6.4% 9Subchondral cyst Thoroughbred 0.20.3% 6, 8Accessory carpal bone fracture Thoroughbred 0.40% 6

    Case Prognosis Summary

    Case 5. Large Medial Malleolar Lucency With Multiple Fragments

    PerformanceGoal

    SurgeryYes/No/Maybe

    ExcellentPrognosis

    GoodPrognosis

    GuardedPrognosis

    PoorPrognosis

    Racing Yesowner/buyer

    Westernperformance Yes

    owner/buyer

    Englishperformance Yes

    owner/buyer

    Generalpurpose Yes

    owner/buyer

    Case Prognosis Summary

    Case 6. Two Enthesophytes: Dorsal Margin of MT3 at the Tarsometa-tarsal Joint and Distal Aspect of the Medial Trochlear Ridge

    PerformanceGoal

    SurgeryYes/No/Maybe

    ExcellentPrognosis

    GoodPrognosis

    GuardedPrognosis

    PoorPrognosis

    Racing Noowner/buyer

    Westernperformance No

    owner/buyer

    Englishperformance No

    owner/buyer

    Generalpurpose No

    owner/buyer

    382 2013 Vol. 59 AAEP PROCEEDINGS

    HOW TO TAKE AND INTERPRET RADIOGRAPHS OF THE YOUNG PERFORMANCE HORSE

  • Table 2. Prevalence of Tarsal Radiographic Abnormalities in Young Performance Horses

    Tarsal Radiographic Abnormality Breed Prevalence Reference

    Any Warmbloods 31.4% 4Any Quarter Horse 68.2% 9OCD of DIRT Thoroughbred 3.45% 2, 5, 7, 8OCD of DIRT Quarter Horse 3.8% 2, 68OCD of DIRT Standardbred 14.517.7% 10, 11OCD of medial malloleus of tibia Thoroughbred 0.41.8% 2, 58OCD of medial malloleus of tibia Quarter Horse 1.10% 9OCD of medial malloleus of tibia Standardbred 2.5% 10, 11OCD of lateral malloleus of tibia Thoroughbred 0.5% 2OCD medial trochlear ridge of talus Thoroughbred 0.12.4% 2, 5, 7, 8OCD medial trochlear ridge of talus Quarter Horse 0.8% 9OCD lateral trochlear ridge of talus Thoroughbred 12.6% 2, 5, 7, 8OCD lateral trochlear ridge of talus Quarter Horse 2.3% 9OCD lateral trochlear ridge of talus Standardbred 1.63.8% 10, 11Dorsal osteophytes PIT, DIT, TMT Thoroughbred 20.125% 2, 5, 7, 8Dorsal osteophytes PIT, DIT, TMT Quarter Horse 47.9% 9Fractures Thoroughbred 0.1% 2Lucency DIT, TMT Thoroughbred 7.30% 5Wedging of T3 or T central Thoroughbred 0.61.6% 57Wedging of T3 or T central Quarter Horse 6.9% 9

    OCD indicates osteochondrosis; DIRT, distal intermediate ridge of talus; PIT, proximal intertarsal joint; DIT, distal intertarsal joint;TMT, tarsometatarsal joint; T3, third tarsal bone; T central, central tarsal bone.

    Case Prognosis SummaryCase 7. Small DIRT Fragment and Large Distal Lateral Trochlear RidgeFragment

    PerformanceGoal

    SurgeryYes/No/Maybe

    ExcellentPrognosis

    GoodPrognosis

    GuardedPrognosis

    PoorPrognosis

    Racing Yesowner/buyer

    Westernperformance Yes

    owner/buyer

    Englishperformance Yes

    owner/buyer

    Generalpurpose Yes

    owner/buyer

    Case Prognosis SummaryCase 8. Remodeling of the Dorsal Margins of the Central and ThirdTarsal Bones and Proximal MT3

    PerformanceGoal

    SurgeryYes/No/Maybe

    ExcellentPrognosis

    GoodPrognosis

    GuardedPrognosis

    PoorPrognosis

    Racing Noowner/buyer

    Westernperformance No

    owner/buyer

    Englishperformance No

    owner/buyer

    Generalpurpose No

    owner/buyer

    Case 7. Small DIRT fragment and large distal lateral trochlearridge fragment.

    Case 8. Remodeling of the dorsal margins of the central andthird tarsal bones and proximal MT3.

    AAEP PROCEEDINGS Vol. 59 2013 383

    HOW TO TAKE AND INTERPRET RADIOGRAPHS OF THE YOUNG PERFORMANCE HORSE

  • jection, but, in young horses, this is of minimal ad-ditional benefit.

    Dorsomedial (65) to Plantarolateral ObliqueProjection of the Tarsus (Fig. 4).The areas of greatest concern on this view arethe distal intermediate ridge of the tibia (DIRT), thelateral trochlear ridge of the talus, and the dorsolat-eral margin of the proximal and distal intertarsaland tarsometatarsal joints.

    Abnormalities best projected on dorsomedial (65)to plantarolateral oblique projection of the tarsusare listed below. If the RA is in bold type, it is thebest projection to detect that RA.

    (1) Osteochondral fragments on the distalintermediate ridge of the tibia

    (2) Defects and osteochondral fragments ofthe lateral trochlear ridge of the talus

    (3) Osteoarthritis and fractures of the central andthird tarsal bones

    Dorsomedial (10) to PlantarolateralProjection of the Tarsus (Fig. 5).The areas of greatest concern on this view is themedial malleolus. However, tarsocrural effusion

    can also be best detected on this view, which canincrease scrutiny of other typical locations of abnor-malities, and, rarely, bony injury to the proximalmetatarsus can be detected.

    Abnormalities best projected on the dorsolateral(10) to plantaromedial projection view of the tarsusare listed below. If the RA is in bold type, it is thebest projection to detect that RA.

    (1) Lucencies and osteochondral fragmentson the axial aspect of the medial malleolus

    (2) Tarsocrural effusion(3) Plantar damage on MT3 at suspensory origin

    Lateral to Medial Projection of the Tarsus(Fig. 6).The areas of greatest concern on this view are thedistodorsal tibia, the dorsal aspect of both trochlearridges, and the dorsal aspect of the proximal and distalintertarsal and the tarsometatarsal joints.

    Case Prognosis Summary

    Case 9. Ulnar Carpal Bone Lucency With Fragment

    PerformanceGoal

    SurgeryYes/No/Maybe

    ExcellentPrognosis

    GoodPrognosis

    GuardedPrognosis

    PoorPrognosis

    Racing Noowner/buyer

    Westernperformance No

    owner/buyer

    Englishperformance No

    owner/buyer

    Generalpurpose No

    owner/buyer

    Case Prognosis Summary

    Case 10. Remodeling of the Distal Radial Carpal Bone

    PerformanceGoal

    SurgeryYes/No/Maybe

    ExcellentPrognosis

    GoodPrognosis

    GuardedPrognosis

    PoorPrognosis

    Racing Maybe owner buyerWestern

    performance Noowner/buyer

    Englishperformance No

    owner/buyer

    Generalpurpose No

    owner/buyer

    Case 10. Remodeling of the distal radial carpal bone.

    Case 9. Ulnar carpal bone lucency with fragment.

    384 2013 Vol. 59 AAE...