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

Elizabeth M. Santschi, DVM, Diplomate ACVS

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

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Fig. 1. Carpus dorsolateral (35°) to palmaromedial oblique projection. 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 intermediate 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 accessory 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

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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 projection. 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 caudal 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

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

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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 demonstrates 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 plantarolateral oblique, dorsolateral (10°) to plantaromedial, 4. Tarsus and lateral to medial. Traditional descriptions of Similar to the carpus, most radiographic abnormal- tarsal views include a lateral to medial oblique pro- ities of the tarsus of young horses can be imaged on

Case Prognosis Summary Case Prognosis Summary Case 6. Two Enthesophytes: Dorsal Margin of MT3 at the Tarsometa- Case 5. Large Medial Malleolar Lucency With Multiple Fragments tarsal Joint and Distal Aspect of the Medial Trochlear Ridge

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 owner/ General owner/ purpose Yes buyer purpose No buyer

382 2013 ր Vol. 59 ր 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% 4 Any Quarter Horse 68.2% 9 OCD of DIRT Thoroughbred 3.4–5% 2, 5, 7, 8 OCD of DIRT Quarter Horse 3.8% 2, 6–8 OCD of DIRT Standardbred 14.5–17.7% 10, 11 OCD of medial malloleus of tibia Thoroughbred 0.4–1.8% 2, 5–8 OCD of medial malloleus of tibia Quarter Horse 1.10% 9 OCD of medial malloleus of tibia Standardbred 2.5% 10, 11 OCD of lateral malloleus of tibia Thoroughbred 0.5% 2 OCD medial trochlear ridge of talus Thoroughbred 0.1–2.4% 2, 5, 7, 8 OCD medial trochlear ridge of talus Quarter Horse 0.8% 9 OCD lateral trochlear ridge of talus Thoroughbred 1–2.6% 2, 5, 7, 8 OCD lateral trochlear ridge of talus Quarter Horse 2.3% 9 OCD lateral trochlear ridge of talus Standardbred 1.6–3.8% 10, 11 Dorsal osteophytes PIT, DIT, TMT Thoroughbred 20.1–25% 2, 5, 7, 8 Dorsal osteophytes PIT, DIT, TMT Quarter Horse 47.9% 9 Fractures Thoroughbred 0.1% 2 Lucency DIT, TMT Thoroughbred 7.30% 5 Wedging of T3 or T central Thoroughbred 0.6–1.6% 5–7 Wedging 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 8. Remodeling of the dorsal margins of the central and Case 7. Small DIRT fragment and large distal lateral trochlear third tarsal bones and proximal MT3. ridge fragment.

Case Prognosis Summary Case Prognosis Summary Case 7. Small DIRT Fragment and Large Distal Lateral Trochlear Ridge Case 8. Remodeling of the Dorsal Margins of the Central and Third Fragment Tarsal Bones and Proximal MT3

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 owner/ General owner/ purpose Yes buyer purpose No buyer

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Case 9. Ulnar carpal bone lucency with fragment. jection, but, in young horses, this is of minimal ad- ditional beneﬁt. Case 10. Remodeling of the distal radial carpal bone. Dorsomedial (65°) to Plantarolateral Oblique Projection of the Tarsus (Fig. 4). The areas of greatest concern on this view are can also be best detected on this view, which can the distal intermediate ridge of the tibia (DIRT), the increase scrutiny of other typical locations of abnor- lateral trochlear ridge of the talus, and the dorsolat- malities, and, rarely, bony injury to the proximal eral margin of the proximal and distal intertarsal metatarsus can be detected. and tarsometatarsal joints. Abnormalities best projected on the dorsolateral Abnormalities best projected on dorsomedial (65°) (10°) to plantaromedial projection view of the tarsus to plantarolateral oblique projection of the tarsus are listed below. If the RA is in bold type, it is the are listed below. If the RA is in bold type, it is the best projection to detect that RA. best projection to detect that RA. (1) Lucencies and osteochondral fragments (1) Osteochondral fragments on the distal on the axial aspect of the medial malleolus intermediate ridge of the tibia (2) Tarsocrural effusion (2) Defects and osteochondral fragments of (3) Plantar damage on MT3 at suspensory origin the lateral trochlear ridge of the talus (3) Osteoarthritis and fractures of the central and Lateral to Medial Projection of the Tarsus third tarsal bones (Fig. 6). Dorsomedial (10°) to Plantarolateral The areas of greatest concern on this view are the Projection of the Tarsus (Fig. 5). distodorsal tibia, the dorsal aspect of both trochlear ridges, and the dorsal aspect of the proximal and distal The areas of greatest concern on this view is the intertarsal and the tarsometatarsal joints. medial malleolus. However, tarsocrural effusion

Case Prognosis Summary Case Prognosis Summary Case 9. Ulnar Carpal Bone Lucency With Fragment Case 10. Remodeling of the Distal Radial Carpal Bone Surgery Performance Yes/No/ Excellent Good Guarded Poor Surgery Goal Maybe Prognosis Prognosis Prognosis Prognosis Performance Yes/No/ Excellent Good Guarded Poor Goal Maybe Prognosis Prognosis Prognosis Prognosis owner/ Racing No buyer Racing Maybe owner buyer Western owner/ Western owner/ performance No buyer performance No buyer English owner/ English owner/ performance No buyer performance No buyer General owner/ General owner/ purpose No buyer purpose No buyer

384 2013 ր Vol. 59 ր AAEP PROCEEDINGS HOW TO TAKE AND INTERPRET RADIOGRAPHS OF THE YOUNG PERFORMANCE HORSE Abnormalities best projected on the lateral to me- ● Arthroscopy for tarsocrural osteochondrosis dial projection of the tarsus are listed below. If the (Standardbreds); 75% race after surgery.16 RA is in bold type, it is the best projection to detect ● Arthroscopy for tarsocrural osteochondrosis that RA. (Standardbreds);43% race at 3 years of age (1) Degenerative joint disease of the distal after surgery; Thoroughbreds, 78% race at 3 intertarsal and tarsometatarsal joints years of age.17 (2) Small axial DIRT fragments 7. Cases (3) Enthesophytes of proximodorsal MT3 The summary prognosis charts (1–10) with each im- (4) Osteochondral fragments in the proximal in- age are predicated on the lesion being detected in a tertarsal joint yearling intended for one of the four disciplines. Tarsal abnormalities that are believed to affect The focus is on performance and not resale blem- later athletic performance are fairly common (31– ishes. The prognosis given to a horse owner and 68%) and the frequency appears to vary by breed the prognosis given to a potential buyer, if different, (Table 2).6–11 is indicated. 5. Determining the Significance of an RA to References Performance 1. Lepeule J, Bareille N, Valette JP, et al. Developmental ortho- paedic disease in the limbs of foals: between-breed variations in Some studies of young stock have included RA of the the prevalence, location and severity at weaning. Animal 2008;2: carpus and tarsus in their attempts to associate 284–291. young horse RA and performance.2,12 These stud- 2. Jackson M, Vizard A, Anderson G, et al. A Prospective Study of ies can be challenging to interpret by strict statisti- Presale Radiographs of Thoroughbred Yearlings. Australian Gov- ernment Rural Industries Research and Development Corpora- cal methods (P Ͻ 0.05) because they have many tion. RIRDC Publication No. 09/082. https:// confounding factors and incomplete outcome infor- rirdc.infoservices.com.au/downloads/09–082.pdf. 2009. mation, usually racing data only. Because of the 3. Courourse´-Malblanc A, Leleu C, Bouchilloux M, et al. Abnormal radiographic findings in 865 French Standardbred trotters and overall low numbers of affected horses, subclassify- their relationship to racing performance. Equine Vet J Suppl ing lesions (size, severity, number of limbs affected, 2006;36:417–422. etc) to determine prognosis is usually not possible. 4. van Grevenhof EM, Ducro BJ, van Weeren PR, et al. Prevalence of various radiographic manifestations of osteochondrosis and However, these studies do have important informa- their correlations between and within joints of Dutch Warmblood tion to help guide veterinarians examining young horses, Equine Vet J 2009;41:11–16. performance horses. RA in the carpus or tarsus 5. Kane AJ, McIlwraith CW, Park RD, et al. Radiographic changes that have been associated with poorer racing out- in Thoroughbred yearlings, part 1: prevalence at the time of the Յ yearling sales. Equine Vet J 2003;35:354–365. comes (P 0.05) include dorsal medial intercarpal 6. Furniss C, Carstens A, van den Berg SS. Radiographic changes joint disease and osteophytes in distal intertarsal or in Thoroughbred yearlings in J South African Vet Assoc 2011;82: tarsometatarsal joints.12 RA in the tarsus or car- 194–204. Ͻ 7. Scott NJ, Hance S, Todhunter P, et al. Incidence of radiographic pus that demonstrate a tendency (P 0.2) for poorer changes in Thoroughbred yearlings: 755 cases. Adv Equine Nu- racing performance include carpal osteophytes, trition III 2005;347–348. fracture of accessory carpal bone, change of medial 8. Oliver LJ, Baird DK, Baird AN, et al. Prevalence and distribu- trochlear ridge of talus,12 and osteochondrosis of tion of radiographically evident lesions on repository films I the 2 hock and stifle joints of yearling Thoroughbred horses in New DIRT or medial malleolus. Zealand. N Z Vet J 2008;56:202–209. There also are multiple publications that focus on 9. Contino EK, Park RD, McIlwraith CW. Prevalence of radio- the treatment of a specific carpal or tarsal lesion, graphic changes in yearling and 2-year-old Quarter Horses intended for cutting. Equine Vet J 2012;44:185–195. and some of these studies have been able to grade 10. Alvarado A, Marcoux M, Breton L. The incidence of osteochon- lesions and document that severity or size can affect drosis in a Standardbred farm in Quebec, in Proceedings. Am prognosis.13–17 Clinicians must judge young stock Assoc Equine Pract 1989;35:293–307. 11. Lykkjen S, Roed KH, Dolvik NI. Osteochondrosis and osteochon- with RA on the basis of careful reading of available dral fragments in Standardbred trotters: prevalence and rela- studies, experience with RA in a given performance tionships. Equine Vet J 2012;44:332–338. discipline, and evaluation of the appearance and 12. Kane AJ, McIlwraith CW, Park RD, et al. Radiographic changes clinical presentation of a specific RA. in Thoroughbred yearlings, part 2: associations with racing performance. Equine Vet J 2003;35:366–374. 13. McIlwraith CW, Yovich JV, Martin GS. Arthroscopic surgery for 6. Prognosis for Carpal or Tarsal RA After Treatment the treatment of osteochondral chip fractures in the equine carpus. J Am Vet Med Assoc 1987;191:531–540. ● Arthroscopy for osteochondral chip fractures of 14. Ross MW, Richardson DW, Beroza GA. Subchondral lucency of the third carpal bone in Standardbred racehorses: 13 cases (1982–1988) carpus: 68% race at level equal to or better J Am Vet Med Assoc 1989;195:789–794. than previous, 11% at lower level; greater car- 15. Dabreiner RM, White NA, Sullins KE. Radiographic and ar- tilage damage results in lower success.13 throscopic findings associated with subchondral lucency of the distal ● radial carpal bone in 71 horses. Equine Vet J 1996;28:93–97. Arthroscopy for lucency of third carpal bone 16. Laws EG, Richardson DW, Ross MW, et al. Racing performance (Standardbreds); 75% race at equal level, 14% of Standardbreds after conservative and surgical treatment for at lower.14 tarsocrural osteochondrosis. Equine Vet J 1993;25:199–202. ● Arthroscopy for lucency of distal radial carpal 17. Beard WL, Bramlage LR, Schneider RK, et al. Postoperative racing performance in Standardbreds and Thoroughbreds with osteo- bone; 68% race at level equal to or better than chondrosis of the tarsocrural joint: 109 cases (1984–1990). JAm 15 previous, 12% at lower. Vet Med Assoc 1994;204:1655–1659.

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