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How to Interpret Radiographs of the Carpus and Tarsus of the Young Performance Horse

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How to Interpret Radiographs of the Carpus and Tarsus of the Young Performance Horse HOW TO TAKE AND INTERPRET RADIOGRAPHS OF THE YOUNG PERFORMANCE HORSE How to Interpret Radiographs of the Carpus and Tarsus of the Young Performance Horse Elizabeth M. Santschi, DVM, Diplomate ACVS Author’s address: Department of Veterinary Clinical Sciences, The Ohio State University, 601 Vernon L. Tharp Street, Columbus, OH 43210; [email protected]. © 2013 AAEP. 1. Introduction there are areas that are more commonly affected by Routine radiographic evaluation of young perfor- RA, and they should receive the closest scrutiny. mance horses has become commonplace in Thor- These will be denoted by black circles on the radio- oughbreds but also occurs in other performance graphic images included in these proceedings. RA breeds. This practice has resulted in the frequent best detected on a specific projection will be listed in discovery of radiographic abnormalities (RA) that bold, but should be confirmed on other projections are often clinically silent but can cause concern in when possible. Finally, readers should always con- buyers and sellers of young performance stock. sider three general factors when reviewing radio- The prevalence of radiographic developmental or- graphic images: thopedic disease in 6-month-old horses has been re- (1) Make sure that the films are of the correct ported to be 25% in Warmbloods, 41% in horse. Standardbreds, and 34% in Thoroughbreds.1 In (2) Make sure the date is appropriate and Thoroughbred yearlings intended for racing, 86.3% consistent. exhibit RA2; in young Standardbreds, 42%3; in year- (3) Make sure all required views are present and ling Warmblood horses, 69.5%4; and in 1- and of acceptable quality. 2-year-old Quarter Horses intended for cutting, 89%.5 Predicting the significance of RA to future 3. Carpus performance can be challenging and frustrating for Most radiographic abnormalities in the carpus of buyers and sellers, which is further complicated by young horses can be imaged on three projections: the possibility of treatment, including surgery, on dorsolateral (35°) to palmaromedial oblique, dorso- prognosis. medial (25°) to palmarolateral oblique, and flexed lateral to medial. A skyline of the distal row can 2. Identifying RA add information if injury to the dorsal surface of the Because radiographic images are reviewed in sets of carpal bones is suspected. At Thoroughbred sales, projections of one joint, this paper will discuss ab- this view is used only for horses that have raced and normalities by each projection. Examiners are re- is not routine for younger stock. Traditional de- sponsible for reading the entire image; however, scriptions of carpal views also include a dorsopalmar NOTES AAEP PROCEEDINGS ր Vol. 59 ր 2013 379 HOW TO TAKE AND INTERPRET RADIOGRAPHS OF THE YOUNG PERFORMANCE HORSE Fig. 1. Carpus dorsolateral (35°) to palmaromedial oblique pro- jection. This image demonstrates remodeling of the distal radial and proximal third carpal bones (white circle). This radiograph Fig. 2. Carpus dorsomedial (25°) to palmarolateral oblique pro- will be discussed by the panel as Case 1. jection. This image demonstrates remodeling of the distal inter- mediate carpal bone (white circle). This radiograph will be discussed by the panel as Case 2. and standing lateral projection, but, in the interest of controlling cost and radiation exposure, are not (3) Osteochondral fragments or remodeling included in sale radiographs. of the distomedial radius (4) Osteochondral fragments or remodeling of the Dorsolateral (35°) to Palmaromedial Oblique proximal radial carpal bone Projection of the Carpus (Fig. 1). (5) Fractures of the radial articulation of the ac- The areas of greatest concern on this view are cessory carpal bone the dorsomedial aspect of the distal radius and the (6) Palmar fragments in the middle carpal joint proximal radial, distal radial, and proximal third (7) Ulnar carpal bone lucencies or axial fragments carpal bones. The radial articulation of the acces- sory carpal bone, the palmar aspect of the ulnar Dorsomedial (25°) to Palmarolateral Oblique carpal bone, and the palmar pouch of the middle Projection of the Carpus (Fig. 2). carpal joint are also of interest. The areas of greatest concern on this view are Abnormalities best identified on the dorsolateral the dorsolateral aspect of the distal radius and the (35°) to palmaromedial oblique are listed below. If proximal intermediate, distal intermediate, and the RA is in bold type, it is the best projection to proximal third carpal bones. The ulnar carpal bone detect that RA. and the palmar pouch of the middle carpal joint are (1) Osteochondral fragments or remodeling also of interest. of the distal radial carpal bone Abnormalities best projected on the dorsomedial (2) Osteochondral fragments or remodeling (25°) to palmarolateral oblique projection of the car- of the proximal third carpal bone pus are listed below. If the RA is in bold type, it is the best projection to detect that RA. Case Prognosis Summary Case Prognosis Summary Case 1. Remodeling of the Distal Radial and Proximal Third Carpal Bones Case 2. Remodeling of the Distal Intermediate Carpal Bone Surgery Surgery Performance Yes/No/ Excellent Good Guarded Poor Performance Yes/No/ Excellent Good Guarded Poor Goal Maybe Prognosis Prognosis Prognosis Prognosis Goal Maybe Prognosis Prognosis Prognosis Prognosis owner/ owner/ Racing Yes buyer Racing No buyer Western owner/ Western owner/ performance Yes buyer performance No buyer English owner/ English owner/ performance Yes buyer performance No buyer General General owner/ purpose Yes owner buyer purpose No buyer 380 2013 ր Vol. 59 ր AAEP PROCEEDINGS HOW TO TAKE AND INTERPRET RADIOGRAPHS OF THE YOUNG PERFORMANCE HORSE Fig. 3. Carpal flexed lateral to medial projection. This image demonstrates a small osteochondroma on the caudal radius (white circle). This radiograph will be discussed by the panel as Case 3. Fig. 4. Tarsal dorsomedial (65°) to plantarolateral oblique pro- jection. This image demonstrates a DIRT lesion composed of (1) Osteophytes on the proximal intermedi- multiple fragments (white circle). This radiograph will be dis- ate carpal bone cussed by the panel as Case 4. (2) Osteophytes or remodeling on the distal intermediate carpal bone (3) Osteochondral fragments from the disto- low. If the RA is in bold type, it is the best projec- central radius or proximal intermediate car- tion to detect that RA. pal bone (1) Osteochondral fragments or remodeling (4) Osteochondral fragments from the prox- of the distal radial carpal bone imal third carpal bone (2) Osteochondral fragments or remodeling (5) Osteochondral fragments from the plamar as- of the distal intermediate carpal bone pect of the radial carpal bone (3) Osteochondral fragments or remodeling Flexed Lateral to Medial Projection of the of the proximal third carpal bone Carpus (Fig. 3). (4) Osteochondroma formation on the cau- dal radius The areas of greatest concern on this view are Carpal abnormalities that are believed to affect the proximal dorsal margin of the radial and inter- later athletic performance are not common and are mediate carpal bones, the distal dorsal margin of the generally reported to have a Ͻ7% prevalence in radial and intermediate carpal bones, the proximal sales yearlings (Table 1). Lucencies in the ulnar dorsal margin of the third carpal bone, and the cau- carpal bone are detected with greater frequency but dal aspect of the distal radius. are generally considered insignificant blemishes. Abnormalities best projected on the flexed lateral to medial projection of the carpus are listed be- Case Prognosis Summary Case Prognosis Summary Case 3. Small Osteochondroma on the Caudal Distal Radius Case 4. DIRT Lesion With Multiple Fragments Surgery Surgery Performance Yes/No/ Excellent Good Guarded Poor Performance Yes/No/ Excellent Good Guarded Poor Goal Maybe Prognosis Prognosis Prognosis Prognosis Goal Maybe Prognosis Prognosis Prognosis Prognosis owner/ owner/ Racing No buyer Racing Yes buyer Western owner/ Western owner/ performance No buyer performance Yes buyer English owner/ English owner/ performance No buyer performance Yes buyer General owner/ General owner/ purpose No buyer purpose Maybe buyer AAEP PROCEEDINGS ր Vol. 59 ր 2013 381 HOW TO TAKE AND INTERPRET RADIOGRAPHS OF THE YOUNG PERFORMANCE HORSE Table 1. Prevalence of Carpal Radiographic Abnormalities in Young Performance Horses Carpal Radiographic Abnormality Breed Prevalence Reference Fragment Thoroughbred 0.7–2.2% 2, 5, 8 Osteophytes Thoroughbred 1.1–3.3% 2, 6–8 Osteophytes Quarter Horse 3.5% 9 Enthesophyte Thoroughbred 2.6% 2 Ulnar carpal bone lucency Thoroughbred 8.3–22.2% 2, 6, 7 Dorsomedial carpal disease Thoroughbred 2.7% 6 Dorsomedial carpal disease Quarter Horse 6.4% 9 Subchondral cyst Thoroughbred 0.2–0.3% 6, 8 Accessory carpal bone fracture Thoroughbred 0.40% 6 Fig. 6. Tarsal lateral to medial projection. This image demon- strates a large enthesophyte on MT3 at the dorsal margin of the tarso-metatarsal joint and another on the distal aspect of the medial trochlear ridge (white circle). This radiograph will be Fig. 5. Tarsal dorsolateral (10°) to plantaromedial projec- discussed by the panel as Case 6. tion. This image demonstrates mild tarsocrural effusion (white arrows) and a large medial malleolar lucency with fragments (white circle). This radiograph will be discussed by the panel as Case 5. three projections: dorsomedial (65°) to plantarolat- eral oblique, dorsolateral (10°) to plantaromedial, 4. Tarsus and lateral to medial. Traditional descriptions of Similar
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