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  • 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; 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 performance breeds. This practice has resulted in the frequent discovery of radiographic abnormalities (RA) that are often clinically silent but can cause concern in buyers 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% in Standardbreds, and 34% in Thoroughbreds.1 In Thoroughbred yearlings intended for racing, 86.3% exhibit RA2; in young Standardbreds, 42%3; in year- ling Warmblood horses, 69.5%4; and in 1- and 2-year-old Quarter Horses intended for cutting, 89%.5 Predicting the significance of RA to future performance can be challenging and frustrating for buyers and sellers, which is further complicated by the possibility of treatment, including surgery, on prognosis.

    2. Identifying RA

    Because radiographic images are reviewed in sets of projections 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 by RA, and they should receive the closest scrutiny. These will be denoted by black circles on the radio- graphic images included in these proceedings. RA best detected on a specific projection will be listed in bold, but should be confirmed on other projections when possible. Finally, readers should always con- sider three general factors when reviewing radio- graphic images:

    (1) Make sure that the films are of the correct horse.

    (2) Make sure the date is appropriate and consistent.

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

    3. Carpus

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

    AAEP PROCEEDINGS � Vol. 59 � 2013 379

    HOW TO TAKE AND INTERPRET RADIOGRAPHS OF THE YOUNG PERFORMANCE HORSE

    NOTES

  • and standing lateral projection, but, in the interest of controlling cost and radiation exposure, are not included in sale radiographs.

    Dorsolateral (35°) to Palmaromedial Oblique Projection of the Carpus (Fig. 1). The areas of greatest concern on this view are the dorsomedial aspect of the distal radius and the proximal radial, distal radial, and proximal third carpal bones. The radial articulation of the acces- sory carpal bone, the palmar aspect of the ulnar carpal bone, and the palmar pouch of the middle carpal joint are also of interest.

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

    (1) Osteochondral fragments or remodeling of the distal radial carpal bone

    (2) Osteochondral fragments or remodeling of the proximal third carpal bone

    (3) Osteochondral fragments or remodeling of the distomedial radius

    (4) Osteochondral fragments or remodeling of the proximal 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 Oblique Projection of the Carpus (Fig. 2). The areas of greatest concern on this view are the dorsolateral aspect of the distal radius and the proximal intermediate, distal intermediate, and proximal third carpal bones. The ulnar carpal bone and the palmar pouch of the middle carpal joint are also 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 is the best projection to detect that RA.

    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 will be discussed by the panel as Case 1.

    Case Prognosis Summary

    Case 1. Remodeling of the Distal Radial and Proximal Third Carpal Bones

    Performance Goal

    Surgery Yes/No/ Maybe

    Excellent Prognosis

    Good Prognosis

    Guarded Prognosis

    Poor Prognosis

    Racing Yes owner/ buyer

    Western performance Yes

    owner/ buyer

    English performance Yes

    owner/ buyer

    General purpose Yes owner buyer

    Case Prognosis Summary

    Case 2. Remodeling of the Distal Intermediate Carpal Bone

    Performance Goal

    Surgery Yes/No/ Maybe

    Excellent Prognosis

    Good Prognosis

    Guarded Prognosis

    Poor Prognosis

    Racing No owner/ buyer

    Western performance No

    owner/ buyer

    English performance No

    owner/ buyer

    General purpose 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 be discussed 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 distal intermediate 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 the Carpus (Fig. 3). The areas of greatest concern on this view are the proximal dorsal margin of the radial and inter- mediate carpal bones, the distal dorsal margin of the radial and intermediate carpal bones, the proximal dorsal margin of the third carpal bone, and the cau- dal aspect of the distal radius.

    Abnormalities best projected on the flexed lateral to 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 remodeling of the distal radial carpal bone

    (2) Osteochondral fragments or remodeling of the distal intermediate carpal bone

    (3) Osteochondral fragments or remodeling of the proximal third carpal bone

    (4) Osteochondroma formation on the cau- dal radius

    Carpal abnormalities that are believed to affect later athletic performance are not common and are generally reported to have a �7% prevalence in sales yearlings (Table 1). Lucencies in the ulnar carpal bone are detected with greater frequency but are generally considered insignificant blemishes.

    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 multiple 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

    Performance Goal

    Surgery Yes/No/ Maybe

    Excellent Prognosis

    Good Prognosis

    Guarded Prognosis

    Poor Prognosis

    Racing No owner/ buyer

    Western performance No

    owner/ buyer

    English performance No

    owner/ buyer

    General purpose No

    owner/ buyer

    Case Prognosis Summary

    Case 4. DIRT Lesion With Multiple Fragments

    Performance Goal

    Surgery Yes/No/ Maybe

    Excellent Prognosis

    Good Prognosis

    Guarded Prognosis

    Poor Prognosis

    Racing Yes owner/ buyer

    Western performance Yes

    owner/ buyer

    English performance Yes

    owner/ buyer

    General purpose 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 of tarsal views include a lateral to medial oblique pro-

    Fig. 5. Tarsal dorsolateral (10°) to plantaromedial projec- 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.

    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 discussed 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 0.7–2.2% 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

    Case Prognosis Summary

    Case 5. Large Medial Malleolar Lucency With Multiple Fragments

    Performance Goal

    Surgery Yes/No/ Maybe

    Excellent Prognosis

    Good Prognosis

    Guarded Prognosis

    Poor Prognosis

    Racing Yes owner/ buyer

    Western performance Yes

    owner/ buyer

    English performance Yes

    owner/ buyer

    General purpose 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

    Performance Goal

    Surgery Yes/No/ Maybe

    Excellent Prognosis

    Good Prognosis

    Guarded Prognosis

    Poor Prognosis

    Racing No owner/ buyer

    Western performance No

    owner/ buyer

    English performance No

    owner/ buyer

    General purpose 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% 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 Prognosis Summary Case 7. Small DIRT Fragment and Large Distal Lateral Trochlear Ridge Fragment

    Performance Goal

    Surgery Yes/No/ Maybe

    Excellent Prognosis

    Good Prognosis

    Guarded Prognosis

    Poor Prognosis

    Racing Yes owner/ buyer

    Western performance Yes

    owner/ buyer

    English performance Yes

    owner/ buyer

    General purpose Yes

    owner/ buyer

    Case Prognosis Summary Case 8. Remodeling of the Dorsal Margins of the Central and Third Tarsal Bones and Proximal MT3

    Performance Goal

    Surgery Yes/No/ Maybe

    Excellent Prognosis

    Good Prognosis

    Guarded Prognosis

    Poor Prognosis

    Racing No owner/ buyer

    Western performance No

    owner/ buyer

    English performance No

    owner/ buyer

    General purpose No

    owner/ buyer

    Case 7. Small DIRT fragment and large distal lateral trochlear ridge fragment.

    Case 8. Remodeling of the dorsal margins of the central and third 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 Oblique Projection of the Tarsus (Fig. 4). The areas of greatest concern on this view are the distal intermediate ridge of the tibia (DIRT), the lateral trochlear ridge of the talus, and the dorsolat- eral margin of the proximal and distal intertarsal and tarsometatarsal joints.

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

    (1) Osteochondral fragments on the distal intermediate ridge of the tibia

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

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

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

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

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

    (1) Lucencies and osteochondral fragments on 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 the distodorsal tibia, the dorsal aspect of both trochlear ridges, and the dorsal aspect of the proximal and distal intertarsal and the tarsometatarsal joints.

    Case Prognosis Summary

    Case 9. Ulnar Carpal Bone Lucency With Fragment

    Performance Goal

    Surgery Yes/No/ Maybe

    Excellent Prognosis

    Good Prognosis

    Guarded Prognosis

    Poor Prognosis

    Racing No owner/ buyer

    Western performance No

    owner/ buyer

    English performance No

    owner/ buyer

    General purpose No

    owner/ buyer

    Case Prognosis Summary

    Case 10. Remodeling of the Distal Radial Carpal Bone

    Performance Goal

    Surgery Yes/No/ Maybe

    Excellent Prognosis

    Good Prognosis

    Guarded Prognosis

    Poor Prognosis

    Racing Maybe owner buyer Western

    performance No owner/ buyer

    English performance No

    owner/ buyer

    General purpose No

    owner/ buyer

    Case 10. Remodeling of the distal radial carpal bone.

    Case 9. Ulnar carpal bone lucency with fragment.

    384 2013 � Vol. 59 � AAEP PROCEEDINGS

    HOW TO TAKE AND INTERPRET RADIOGRAPHS OF THE YOUNG PERFORMANCE HORSE

  • Abnormalities best projected on the lateral to me- dial projection of the tarsus are listed below. If the RA is in bold type, it is the best projection to detect that RA.

    (1) Degenerative joint disease of the distal intertarsal and tarsometatarsal joints

    (2) Small axial DIRT fragments (3) Enthesophytes of proximodorsal MT3 (4) Osteochondral fragments in the proximal in-

    tertarsal joint Tarsal abnormalities that are believed to affect

    later athletic performance are fairly common (31– 68%) and the frequency appears to vary by breed (Table 2).6–11

    5. Determining the Significance of an RA to Performance

    Some studies of young stock have included RA of the carpus and tarsus in their attempts to associate young horse RA and performance.2,12 These stud- ies can be challenging to interpret by strict statisti- cal methods (P � 0.05) because they have many confounding factors and incomplete outcome infor- mation, usually racing data only. Because of the overall low numbers of affected horses, subclassify- ing lesions (size, severity, number of limbs affected, etc) to determine prognosis is usually not possible. However, these studies do have important informa- tion to help guide veterinarians examining young performance horses. RA in the carpus or tarsus that have been associated with poorer racing out- comes (P � 0.05) include dorsal medial intercarpal joint disease and osteophytes in distal intertarsal or tarsometatarsal joints.12 RA in the tarsus or car- pus that demonstrate a tendency (P � 0.2) for poorer racing performance include carpal osteophytes, fracture of accessory carpal bone, change of medial trochlear ridge of talus,12 and osteochondrosis of DIRT or medial malleolus.2

    There also are multiple publications that focus on the treatment of a specific carpal or tarsal lesion, and some of these studies have been able to grade lesions and document that severity or size can affect prognosis.13–17 Clinicians must judge young stock with RA on the basis of careful reading of available studies, experience with RA in a given performance discipline, and evaluation of the appearance and clinical presentation of a specific RA.

    6. Prognosis for Carpal or Tarsal RA After Treatment

    ● Arthroscopy for osteochondral chip fractures of carpus: 68% race at level equal to or better than previous, 11% at lower level; greater car- tilage damage results in lower success.13

    ● Arthroscopy for lucency of third carpal bone (Standardbreds); 75% race at equal level, 14% at lower.14

    ● Arthroscopy for lucency of distal radial carpal bone; 68% race at level equal to or better than previous, 12% at lower.15

    ● Arthroscopy for tarsocrural osteochondrosis (Standardbreds); 75% race after surgery.16

    ● Arthroscopy for tarsocrural osteochondrosis (Standardbreds);43% race at 3 years of age after surgery; Thoroughbreds, 78% race at 3 years of age.17

    7. Cases

    The summary prognosis charts (1–10) with each im- age are predicated on the lesion being detected in a yearling intended for one of the four disciplines. The focus is on performance and not resale blem- ishes. The prognosis given to a horse owner and the prognosis given to a potential buyer, if different, is indicated. References 1. Lepeule J, Bareille N, Valette JP, et al. Developmental ortho-

    paedic disease in the limbs of foals: between-breed variations in the prevalence, location and severity at weaning. Animal 2008;2: 284–291.

    2. Jackson M, Vizard A, Anderson G, et al. A Prospective Study of Presale Radiographs of Thoroughbred Yearlings. Australian Gov- ernment Rural Industries Research and Development Corpora- tion. RIRDC Publication No. 09/082. https:// rirdc.infoservices.com.au/downloads/09–082.pdf. 2009.

    3. Couroursé-Malblanc A, Leleu C, Bouchilloux M, et al. Abnormal radiographic findings in 865 French Standardbred trotters and their relationship to racing performance. Equine Vet J Suppl 2006;36:417–422.

    4. van Grevenhof EM, Ducro BJ, van Weeren PR, et al. Prevalence of various radiographic manifestations of osteochondrosis and their correlations between and within joints of Dutch Warmblood horses, Equine Vet J 2009;41:11–16.

    5. Kane AJ, McIlwraith CW, Park RD, et al. Radiographic changes in Thoroughbred yearlings, part 1: prevalence at the time of the yearling sales. Equine Vet J 2003;35:354–365.

    6. Furniss C, Carstens A, van den Berg SS. Radiographic changes in Thoroughbred yearlings in J South African Vet Assoc 2011;82: 194–204.

    7. Scott NJ, Hance S, Todhunter P, et al. Incidence of radiographic changes in Thoroughbred yearlings: 755 cases. Adv Equine Nu- trition III 2005;347–348.

    8. Oliver LJ, Baird DK, Baird AN, et al. Prevalence and distribu- tion of radiographically evident lesions on repository films I the hock and stifle joints of yearling Thoroughbred horses in New Zealand. N Z Vet J 2008;56:202–209.

    9. Contino EK, Park RD, McIlwraith CW. Prevalence of radio- graphic changes in yearling and 2-year-old Quarter Horses in- tended for cutting. Equine Vet J 2012;44:185–195.

    10. Alvarado A, Marcoux M, Breton L. The incidence of osteochon- drosis in a Standardbred farm in Quebec, in Proceedings. Am Assoc Equine Pract 1989;35:293–307.

    11. Lykkjen S, Roed KH, Dolvik NI. Osteochondrosis and osteochon- dral fragments in Standardbred trotters: prevalence and rela- tionships. Equine Vet J 2012;44:332–338.

    12. Kane AJ, McIlwraith CW, Park RD, et al. Radiographic changes in Thoroughbred yearlings, part 2: associations with racing per- formance. Equine Vet J 2003;35:366–374.

    13. McIlwraith CW, Yovich JV, Martin GS. Arthroscopic surgery for the treatment of osteochondral chip fractures in the equine car- pus. J Am Vet Med Assoc 1987;191:531–540.

    14. Ross MW, Richardson DW, Beroza GA. Subchondral lucency of the third carpal bone in Standardbred racehorses: 13 cases (1982–1988) J Am Vet Med Assoc 1989;195:789–794.

    15. Dabreiner RM, White NA, Sullins KE. Radiographic and ar- throscopic findings associated with subchondral lucency of the distal radial carpal bone in 71 horses. Equine Vet J 1996;28:93–97.

    16. Laws EG, Richardson DW, Ross MW, et al. Racing performance of Standardbreds after conservative and surgical treatment for tarsocrural osteochondrosis. Equine Vet J 1993;25:199–202.

    17. Beard WL, Bramlage LR, Schneider RK, et al. Postoperative rac- ing performance in Standardbreds and Thoroughbreds with osteo- chondrosis of the tarsocrural joint: 109 cases (1984–1990). J Am Vet Med Assoc 1994;204:1655–1659.

    AAEP PROCEEDINGS � Vol. 59 � 2013 385

    HOW TO TAKE AND INTERPRET RADIOGRAPHS OF THE YOUNG PERFORMANCE HORSE

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