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The incidence of osteochondrosis in the tibiotarsal joint of norwegian standardbred trotters
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THE INCIDENCEOF OSTEOCHONDROSIS IN THETIBIOTARSALJOINTOF NORWEGIANSTANDARDBREDTROTrERS A Radiographic Study
A. M. Grcndahl, DVM
SUMMARY
The tibiotarsal joints of 753 Norwegian Standardbred trotters, all yearlings, were radiographed. Osteochondrosis (OCD) was diagnosed at the intermediate ridge of the distal tibia and/or at the lateral trochlea of the talus in 108 (14.3%) horses. The changes were bilateral in 49 (45.4%) affected horses. A significant difference between the sexes in the incidence of OCD was not observed (15.0% of mares and 13.7% of stallions). Radiographs were repeated on 79 horses after 6-18 months and revealed OCD in only one additional joint. INTRODUCTION
Intra-articular bony fragments are a common radiographic finding in the tibiotarsal joints of Standardbred trotters. Bony lesions at the intermediate ridge of the distal tibia were originally described as intracapsular bony fragments,a but were subsequently termed osteochondritis dissecans? Osteochondritis dissecans is reported to be the clinically most important manifestation of osteochondrosis.11 Authorsaddress: Norwegian College of Veterinary Medicine, Department of Large Animal Clinical Science, P. B. O. 8146 Dep., N-0033, Oslo 1, Norway, Acknowledgments: The cooperationof Dr. Reidar Birkeland and Dr. Nile • Ivar Dolvik in the interpretation of radiographs is gratefully acknowledged, as is their guidance in experimental design. The author also thanks Charles Press for help with the language and for constructive criticism of the manuscript.
272
Many aspects of OCD in the tibiotarsal joint have been reported including clinical signs, radiographic findings, surgical management and response to conservative treatment. Possible etiologic factors on the development of OCD has been reviewed.5Comparison of the performance of Standardbred trotters with and without OCD in the tibiotarsal joint revealed that horses with OCD had a lower racing capacity. This observation was however based on a relatively small number of animals, z Frequency studies of OCD in the tibiotarsal joints of young, healthy Standardbred trotters have reported incidences of OCD ranging from 9.7% to 26% (Table 1). A large radiographic survey was performed on tibiotarsal and fetlockjoints of Norwegian Standardbred yearlings to investigate the incidence and significance of OCD and bony fragments in the Standardbred population in Norway. This paper presents the results of the frequency study of OCD in the tibiotarsal joints and the results of follow-up radiographic examinations. Data gathered from the survey dealing with T a b l e 1 . F r e q u e n c y of O C D in the tibiotarsal joint of Stand a r d b r e d trotters.
Authors Falk-Ronne et al e Hoppe et als Hoppe 7 Sandgren 14 Ron~us et a112
No. of horses
Age in years
133 226 208 130 139 264
2-3 0-2 0-2 0-3 0-6 1-2
% OCD 13.5 9.7 10 26 18 15.0
% bilat occurrence
29 38 56 34.8
EQUINE VETERINA.RY SCIENCE
Table 2. Age of the horse when radiographed.
Age in months Number examined Number OCD Percent OCD
6-7
8-9
10-11
12-13
14-15
16-17
18-19
20-21
21 1 5
108 15 14
295 46 16
244 34 14
48 10 21
12 0 0
20 2 10
5 0 0
heritability, performance capacity and findings in the fetlock joints will be published separately.
MATERIALS AND M E T H O D S
A list of all Norwegian Standardbred trotters born in 1988 and registered before August 1989 (total 1179 horses) was obtained from the Norwegian Trotting Association. The owners of these horses were contacted by telephone and invited to include their horses in a radiographic survey. The radiographic examination took place in 1989 and 753 yearlings participated. It was not possible to contact all owners: 328 owners were not registered in the telephone directory, 68 owners were unable or unwilling tobe involved, and 3 owners had secrettelephone numbers. Eighteen horses were abroad at the time and 9 horses were dead. No selection was undertaken among the horses that did take part in the survey and horses from all parts of Norway were represented. About 200 horses were x-rayed at the Norwegian College of Veterinary Medicine, using Philips diaphragms, Rotalix 350 x-ray tube, Maximus CM 80 Generator, Gevamatic 240 U developer and CAWO U-cassettes (par speed). The remaining horses were x-rayed either at a racetrack or at the owner's farm using a Portable x-ray unit type SP 104, Gevamatic developer and Curix MR-400 cassettes. The film used was Curix RP 1L. Before radiographic examination, the horses were given detomidine (2-3 rag. I.V.).a Radiographs were taken of both tibiotarsaljoints in dorsomedial-plantarolateral oblique (DMPLO) view. The horses were not given a clinical examination. The only orthopedic problems reported by the owners were in a few horses with acquired contracted flexor tendons or distention in the tibiotarsaljoint(s). In the period from January to June 1989 the 716 horses examined had not yet started training. Most of the 37 horses examined from October to December, 1989 had just started training. The tibiotarsal joints of 79 horses were x-rayed a second time 6-18 months later. These horses were selected at random from the 716 horses radiographed in the first half of 1989. All radiographs were scrutinized by the author and one other qualified person, jointly, for the presence of lesions suggestive of OCD. For this study, horses with characteristic radiographic defects at the anterior edge of the intermediate ridge of the distal tibia and/or at the lateral trochlea of talus were diagaDornosedan®,Farmos,GroupLimited,Turku, Finland.
Volume 11, Number 5, 1991
nosed as having OCD. In a few horses, radiographic changes suggestive of a piece of bony tissue adherent to the distal end of the lateral trochlea of talus were found. Cystic-like changes in the medial or lateral malleolus of the tibia and changes in the central and third tarsal bone were also observed. These radiographic changes were not interpreted as OCD. The differencesbetween groups were assessed using chisquare test.
RESULTS
Radiographic examinations were performed on 753 horses aged between 6-21 months (Table 2) and included 387 (51.4%) mares and 366 (48.6%) stallions. OCD was diagnosed in 108 horses (14.3 %) with a total of 157 affectedjoints. The radiographic changes of OCD were bilateral in 49 (45.4%) affected horses, and occurred only in the right tibiotarsal joint in 23 (21.3%) horses and only in the left in 36 (33.3 %) horses. OCD was present in 58 (53.7%) mares and 50 (46.3%) stallions. The percentage of mares (15.0%) affected was higher than percentage of stallions (13.7%) affected, but the difference was not statistically significant (p>0.05). The characteristic radiographic changes of OCD in the tibiotarsal joints were divided into three types. Horses with Type 1 changes had bony fragment(s) with defects in the underlying bone tissue at the intermediate ridge of the distal tibia. Horses with Type 2 changes had defects in the bone tissue at the intermediate ridge without bony fragment(s) and horses with Type 3 changes had defects at the lateral trochlea of the talus. More than one type of OCD could be present in the same joint. The frequency of the different types of OCD is shown in Table 3. A second radiographic examination was performed on the tibiotarsaljoints of 79 horses, 6-18 months after the first examination.At the first examination of this group of horses, OCD was present in 16joints. The second examination of these horses, now beyond one year of age, revealed OCD in only one additional joint. This gives an incidence of 0.7% of OCD in the tibiotarsal joint developing in horses after one year of age.
DISCUSSION
The extensive survey of Norwegian Standardbred yearlings demonstrated an incidence of OCD in tibiotarsal joints (14.3%) and a bilateral occurrence (45.4%) that was similar
273
Table 3. Frequency of different types of osteochondrosis in the tibiotarsal joint. REFERENCES Type
Type
la
2b
Type 3c
Type 1+3 d
Totally
No. of horses
94
13
8
4
108
No. of joints
130
15
8
4
157
aType 1: Bony frag ment(s) and defects at intermediate ridge of distal tibia. bType 2: Defects without fragments at intermediate ridge of distal tibia. C'l'ype 3: Defects at lateral trochlea of talus. dType 1+3: Joints with both Type 1 and Type 3.
to earlier investigations of comparable populations. 7,12,14 Many reports based on clinical cases have shown a sex difference for the occurrence of OCD in the tibiotarsal joints. 9,1°,15,17In this study, a significant difference between the sexes in occurrence of OCD was not observed. Other frequency studies of young, healthy Standardbred trottersZ.12.14have also failed to find a significant sex difference. The radiographic changes in the tibiotarsal joints described in this paper are characteristic of OCD? 8 For this study only one radiograph (DMPLO view) was routinely taken of each tibiotarsal joint. Thus, some OCD changes may have been missed as was the situation for OCD lesions of the medial malleolus. However, the DMPLO view provides a good view of the intermediate ridge of the distal dbia and also allows evaluation of the lateral trochlea of the talus. Reports have indicated that 92-94% of OCD in the tibiotarsal joints of gotters were located at the intermediate ridge of the distal tibia,a,15 While several theories for the etiology of OCD have been considered, its pathogenesis is still uncertain. OCD has been considered to occur during the growth period of the horse.1,18 Rooney13 stated that "OCD develops during the 3rd to 6th month after birth." Hoppe6 found a higher incidence of OCD among 2 year old trotters than one year old trotters, and suggested that OCD might occur after the horse was one year old. The results of the present study in Norwegian Standardbred trotters would suggest that OCD in the tibiotarsal joints rarely occurs after one year of age. Since most of the horses were younger than one year old the owners/trainers had not or]ust started to break in these horses. Because of this, a clinical examination would be difficult to perform and evaluate, and was therefore not performed. The present paper describes a purely radiographic study without clinical evaluation. The occurrence of OCD in horses at this early age, and without registered lameness, makes it difficult to evaluate the significance of these changes and thus the need for treatment. The performance capacity of affected horses would provide important information for recommending appropriate therapeutic management.
274
1. Adams OR: Lameness in horses. Philadelphia:Lea & Febiger, p398,1974. 2. Birkeland R, Haakenstad L: Intracapsular bony fragments of the distal tibia in the horse. JAm VetMedAssoc 152:15261529,1968. 3. De Moor A, Verchooten F, Desmet P, Steenhaut M, H ooren s J, Wolf G: Osteochondritis dissecan s of the ti bio-tarsal joint in the horse. Equine VetJ 4:139-143,1972. 4. Falk-Ronne J, Kristoffersen J: Forekomsten af osteochondrose i talo-cruralleddet hos unge travheste i traening. Dan Vet Tidsskr 63(4):141-143,1980. 5. Glade MJ: The control of cartilage growth in osteochondrosis: a review. J Equine Vet Sci 6(4):175-187,1986. 6. Hoppe F, Philipsson J, Jeffcott LB: Epidemiologiska och genetiska aspekter avseende osteochondros hos unga h~star i Sverige. Sven Vet Tidskr suppl 3, 35:66-69,1983. 7. Hoppe F: Osteochondrosis in Swedish horses. Thesis, Swedish University of Agricultural Sciences, Uppsala, 1984. 8. Hoppe F: Radiological investigations of osteochondrosis dissecans in Standardbred Trotters and Swedish Warmblood horses. Equine Vet J 16(5):425-429,1984. 9. Lindsell CE, Hilbert BJ, McGill CA: A retrospective clinical study of osteochondrosis dissecans in 21 horses. Aust Vet J 60:291-293,1983. 10. Olsson l, Pettersson H, Stromberg B: Prognos vid behandling av osteochondros i talocruralleden hos travh&st. Sven Vet Tidskr suppl 3, 35:70-71,1983. 11. Olsson SE: Osteochondrosis in domestic animals. Acta Radiol suppl 358:9-14,1978. 12. Ron6us B, Carlsten J: Lesa benbitar i kot- och hasleder hos unga travh~istar. Sven Vet Tidskr 7:417-422,1989. 13. Rooney JR: Osteochondrosis in the horse. Mod VetPract 56(1):41-43,1975. 14. Sandgren B: Bony fragments in the tarsocrural and metacarpo- or metatarsophalangeal joints in the Standardbred horse - a radiographic survey. Equine Vet J suppl 6:66-70,1988. 15. Schougaard H, Falk-Renne J, Sonnichsen HV, Kristoffersen J: Osteochondrose i talo-cruralleddet hos best. Dan Vet Tidsskr 62(21):1021-1026,1979. 16. Stremberg B, Rejne S: Osteochondrosis in the horse. 1. A clinical and radiologic investigation of osteochondritis dissecans of the knee and hock joint. Acta Radiol supp1358:139-152,1978. 17. Trotter GW, Mcllwraith CW: Osteochondritis dissecans and subchondral cystic lesions and their relationship to osteochondrosis in the horse. J Equine Vet Sci 1:157-162,1981.
EQUINE VETERINARY SCIENCE
, ~'~. . . ~ .
~:
.~ ~-~ •~
~
Refereed
THE INCIDENCEOF OSTEOCHONDROSIS IN THETIBIOTARSALJOINTOF NORWEGIANSTANDARDBREDTROTrERS A Radiographic Study
A. M. Grcndahl, DVM
SUMMARY
The tibiotarsal joints of 753 Norwegian Standardbred trotters, all yearlings, were radiographed. Osteochondrosis (OCD) was diagnosed at the intermediate ridge of the distal tibia and/or at the lateral trochlea of the talus in 108 (14.3%) horses. The changes were bilateral in 49 (45.4%) affected horses. A significant difference between the sexes in the incidence of OCD was not observed (15.0% of mares and 13.7% of stallions). Radiographs were repeated on 79 horses after 6-18 months and revealed OCD in only one additional joint. INTRODUCTION
Intra-articular bony fragments are a common radiographic finding in the tibiotarsal joints of Standardbred trotters. Bony lesions at the intermediate ridge of the distal tibia were originally described as intracapsular bony fragments,a but were subsequently termed osteochondritis dissecans? Osteochondritis dissecans is reported to be the clinically most important manifestation of osteochondrosis.11 Authorsaddress: Norwegian College of Veterinary Medicine, Department of Large Animal Clinical Science, P. B. O. 8146 Dep., N-0033, Oslo 1, Norway, Acknowledgments: The cooperationof Dr. Reidar Birkeland and Dr. Nile • Ivar Dolvik in the interpretation of radiographs is gratefully acknowledged, as is their guidance in experimental design. The author also thanks Charles Press for help with the language and for constructive criticism of the manuscript.
272
Many aspects of OCD in the tibiotarsal joint have been reported including clinical signs, radiographic findings, surgical management and response to conservative treatment. Possible etiologic factors on the development of OCD has been reviewed.5Comparison of the performance of Standardbred trotters with and without OCD in the tibiotarsal joint revealed that horses with OCD had a lower racing capacity. This observation was however based on a relatively small number of animals, z Frequency studies of OCD in the tibiotarsal joints of young, healthy Standardbred trotters have reported incidences of OCD ranging from 9.7% to 26% (Table 1). A large radiographic survey was performed on tibiotarsal and fetlockjoints of Norwegian Standardbred yearlings to investigate the incidence and significance of OCD and bony fragments in the Standardbred population in Norway. This paper presents the results of the frequency study of OCD in the tibiotarsal joints and the results of follow-up radiographic examinations. Data gathered from the survey dealing with T a b l e 1 . F r e q u e n c y of O C D in the tibiotarsal joint of Stand a r d b r e d trotters.
Authors Falk-Ronne et al e Hoppe et als Hoppe 7 Sandgren 14 Ron~us et a112
No. of horses
Age in years
133 226 208 130 139 264
2-3 0-2 0-2 0-3 0-6 1-2
% OCD 13.5 9.7 10 26 18 15.0
% bilat occurrence
29 38 56 34.8
EQUINE VETERINA.RY SCIENCE
Table 2. Age of the horse when radiographed.
Age in months Number examined Number OCD Percent OCD
6-7
8-9
10-11
12-13
14-15
16-17
18-19
20-21
21 1 5
108 15 14
295 46 16
244 34 14
48 10 21
12 0 0
20 2 10
5 0 0
heritability, performance capacity and findings in the fetlock joints will be published separately.
MATERIALS AND M E T H O D S
A list of all Norwegian Standardbred trotters born in 1988 and registered before August 1989 (total 1179 horses) was obtained from the Norwegian Trotting Association. The owners of these horses were contacted by telephone and invited to include their horses in a radiographic survey. The radiographic examination took place in 1989 and 753 yearlings participated. It was not possible to contact all owners: 328 owners were not registered in the telephone directory, 68 owners were unable or unwilling tobe involved, and 3 owners had secrettelephone numbers. Eighteen horses were abroad at the time and 9 horses were dead. No selection was undertaken among the horses that did take part in the survey and horses from all parts of Norway were represented. About 200 horses were x-rayed at the Norwegian College of Veterinary Medicine, using Philips diaphragms, Rotalix 350 x-ray tube, Maximus CM 80 Generator, Gevamatic 240 U developer and CAWO U-cassettes (par speed). The remaining horses were x-rayed either at a racetrack or at the owner's farm using a Portable x-ray unit type SP 104, Gevamatic developer and Curix MR-400 cassettes. The film used was Curix RP 1L. Before radiographic examination, the horses were given detomidine (2-3 rag. I.V.).a Radiographs were taken of both tibiotarsaljoints in dorsomedial-plantarolateral oblique (DMPLO) view. The horses were not given a clinical examination. The only orthopedic problems reported by the owners were in a few horses with acquired contracted flexor tendons or distention in the tibiotarsaljoint(s). In the period from January to June 1989 the 716 horses examined had not yet started training. Most of the 37 horses examined from October to December, 1989 had just started training. The tibiotarsal joints of 79 horses were x-rayed a second time 6-18 months later. These horses were selected at random from the 716 horses radiographed in the first half of 1989. All radiographs were scrutinized by the author and one other qualified person, jointly, for the presence of lesions suggestive of OCD. For this study, horses with characteristic radiographic defects at the anterior edge of the intermediate ridge of the distal tibia and/or at the lateral trochlea of talus were diagaDornosedan®,Farmos,GroupLimited,Turku, Finland.
Volume 11, Number 5, 1991
nosed as having OCD. In a few horses, radiographic changes suggestive of a piece of bony tissue adherent to the distal end of the lateral trochlea of talus were found. Cystic-like changes in the medial or lateral malleolus of the tibia and changes in the central and third tarsal bone were also observed. These radiographic changes were not interpreted as OCD. The differencesbetween groups were assessed using chisquare test.
RESULTS
Radiographic examinations were performed on 753 horses aged between 6-21 months (Table 2) and included 387 (51.4%) mares and 366 (48.6%) stallions. OCD was diagnosed in 108 horses (14.3 %) with a total of 157 affectedjoints. The radiographic changes of OCD were bilateral in 49 (45.4%) affected horses, and occurred only in the right tibiotarsal joint in 23 (21.3%) horses and only in the left in 36 (33.3 %) horses. OCD was present in 58 (53.7%) mares and 50 (46.3%) stallions. The percentage of mares (15.0%) affected was higher than percentage of stallions (13.7%) affected, but the difference was not statistically significant (p>0.05). The characteristic radiographic changes of OCD in the tibiotarsal joints were divided into three types. Horses with Type 1 changes had bony fragment(s) with defects in the underlying bone tissue at the intermediate ridge of the distal tibia. Horses with Type 2 changes had defects in the bone tissue at the intermediate ridge without bony fragment(s) and horses with Type 3 changes had defects at the lateral trochlea of the talus. More than one type of OCD could be present in the same joint. The frequency of the different types of OCD is shown in Table 3. A second radiographic examination was performed on the tibiotarsaljoints of 79 horses, 6-18 months after the first examination.At the first examination of this group of horses, OCD was present in 16joints. The second examination of these horses, now beyond one year of age, revealed OCD in only one additional joint. This gives an incidence of 0.7% of OCD in the tibiotarsal joint developing in horses after one year of age.
DISCUSSION
The extensive survey of Norwegian Standardbred yearlings demonstrated an incidence of OCD in tibiotarsal joints (14.3%) and a bilateral occurrence (45.4%) that was similar
273
Table 3. Frequency of different types of osteochondrosis in the tibiotarsal joint. REFERENCES Type
Type
la
2b
Type 3c
Type 1+3 d
Totally
No. of horses
94
13
8
4
108
No. of joints
130
15
8
4
157
aType 1: Bony frag ment(s) and defects at intermediate ridge of distal tibia. bType 2: Defects without fragments at intermediate ridge of distal tibia. C'l'ype 3: Defects at lateral trochlea of talus. dType 1+3: Joints with both Type 1 and Type 3.
to earlier investigations of comparable populations. 7,12,14 Many reports based on clinical cases have shown a sex difference for the occurrence of OCD in the tibiotarsal joints. 9,1°,15,17In this study, a significant difference between the sexes in occurrence of OCD was not observed. Other frequency studies of young, healthy Standardbred trottersZ.12.14have also failed to find a significant sex difference. The radiographic changes in the tibiotarsal joints described in this paper are characteristic of OCD? 8 For this study only one radiograph (DMPLO view) was routinely taken of each tibiotarsal joint. Thus, some OCD changes may have been missed as was the situation for OCD lesions of the medial malleolus. However, the DMPLO view provides a good view of the intermediate ridge of the distal dbia and also allows evaluation of the lateral trochlea of the talus. Reports have indicated that 92-94% of OCD in the tibiotarsal joints of gotters were located at the intermediate ridge of the distal tibia,a,15 While several theories for the etiology of OCD have been considered, its pathogenesis is still uncertain. OCD has been considered to occur during the growth period of the horse.1,18 Rooney13 stated that "OCD develops during the 3rd to 6th month after birth." Hoppe6 found a higher incidence of OCD among 2 year old trotters than one year old trotters, and suggested that OCD might occur after the horse was one year old. The results of the present study in Norwegian Standardbred trotters would suggest that OCD in the tibiotarsal joints rarely occurs after one year of age. Since most of the horses were younger than one year old the owners/trainers had not or]ust started to break in these horses. Because of this, a clinical examination would be difficult to perform and evaluate, and was therefore not performed. The present paper describes a purely radiographic study without clinical evaluation. The occurrence of OCD in horses at this early age, and without registered lameness, makes it difficult to evaluate the significance of these changes and thus the need for treatment. The performance capacity of affected horses would provide important information for recommending appropriate therapeutic management.
274
1. Adams OR: Lameness in horses. Philadelphia:Lea & Febiger, p398,1974. 2. Birkeland R, Haakenstad L: Intracapsular bony fragments of the distal tibia in the horse. JAm VetMedAssoc 152:15261529,1968. 3. De Moor A, Verchooten F, Desmet P, Steenhaut M, H ooren s J, Wolf G: Osteochondritis dissecan s of the ti bio-tarsal joint in the horse. Equine VetJ 4:139-143,1972. 4. Falk-Ronne J, Kristoffersen J: Forekomsten af osteochondrose i talo-cruralleddet hos unge travheste i traening. Dan Vet Tidsskr 63(4):141-143,1980. 5. Glade MJ: The control of cartilage growth in osteochondrosis: a review. J Equine Vet Sci 6(4):175-187,1986. 6. Hoppe F, Philipsson J, Jeffcott LB: Epidemiologiska och genetiska aspekter avseende osteochondros hos unga h~star i Sverige. Sven Vet Tidskr suppl 3, 35:66-69,1983. 7. Hoppe F: Osteochondrosis in Swedish horses. Thesis, Swedish University of Agricultural Sciences, Uppsala, 1984. 8. Hoppe F: Radiological investigations of osteochondrosis dissecans in Standardbred Trotters and Swedish Warmblood horses. Equine Vet J 16(5):425-429,1984. 9. Lindsell CE, Hilbert BJ, McGill CA: A retrospective clinical study of osteochondrosis dissecans in 21 horses. Aust Vet J 60:291-293,1983. 10. Olsson l, Pettersson H, Stromberg B: Prognos vid behandling av osteochondros i talocruralleden hos travh&st. Sven Vet Tidskr suppl 3, 35:70-71,1983. 11. Olsson SE: Osteochondrosis in domestic animals. Acta Radiol suppl 358:9-14,1978. 12. Ron6us B, Carlsten J: Lesa benbitar i kot- och hasleder hos unga travh~istar. Sven Vet Tidskr 7:417-422,1989. 13. Rooney JR: Osteochondrosis in the horse. Mod VetPract 56(1):41-43,1975. 14. Sandgren B: Bony fragments in the tarsocrural and metacarpo- or metatarsophalangeal joints in the Standardbred horse - a radiographic survey. Equine Vet J suppl 6:66-70,1988. 15. Schougaard H, Falk-Renne J, Sonnichsen HV, Kristoffersen J: Osteochondrose i talo-cruralleddet hos best. Dan Vet Tidsskr 62(21):1021-1026,1979. 16. Stremberg B, Rejne S: Osteochondrosis in the horse. 1. A clinical and radiologic investigation of osteochondritis dissecans of the knee and hock joint. Acta Radiol supp1358:139-152,1978. 17. Trotter GW, Mcllwraith CW: Osteochondritis dissecans and subchondral cystic lesions and their relationship to osteochondrosis in the horse. J Equine Vet Sci 1:157-162,1981.
EQUINE VETERINARY SCIENCE