Introduction. Keywords Equine, metacarpophalangeal joint, metatarsophalangeal

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1 Origial Research Radiographic features of the dorsal codylar sagittal ridge of the third metacarpal ad metatarsal boes i youg Warmblood stallios S. Hauspie 1 ; A. Martes 2 ; J. Declercq 2 ; V. Busoi ; K. Vaderperre 1 ; H. va Bree 1 ; J. H. Sauders 1 1 Departmet of Veteriary Medical Imagig ad Small Aimal Orthopaedics, Faculty of Veteriary Medicie, Ghet Uiversity, Salisburylaa, Belgium; 2 Departmet of Surgery ad Aaesthesia of Domestic Aimals, Faculty of Veteriary Medicie, Ghet Uiversity, Salisburylaa, Belgium; Departmet of Medical Imagig, Faculty of Veteriary Medicie, Uiversity of Liege, Sart-Tilma; Belgium Schattauer Keywords Equie, metacarpophalageal joit, metatarsophalageal joit, radiography, Warmblood stallio Summary Objectives: To describe the radiographic appearace of the dorsoproximal aspect of the sagittal ridge of the third metacarpal/metatarsal boe i Warmblood horses. Methods: The lateromedial radiographic projectios of the metacarpo-/metatarsophalageal joits performed o horses as a part of stallio selectio were used. The dorsal aspect of the distal third metacarpal/metatarsal boe was divided i two areas. The appearace of the boe surface i area I was classified as ormal, irregular, otch, idetatio ad lucecy. For area II, the categories were ormal, irregular, depressio or lucecy ad flatteig of the sagittal ridge. Other abormalities at the dorsal aspect were also oted. Correspodece to: Stij Hauspie, DVM Faculty of Veteriary Medicie Ghet Uiversity Departmet of Veteriary Medical Imagig ad Small Aimal Orthopaedics Salisburylaa Merelbeke Belgium Phoe: Fax: Stij.hauspie@uget.be Fudig: Stij Hauspie is a research fellow of the Special Research Fud, Ghet Uiversity (Belgium). Results: I area I, 51.5 of the ridges appeared ormal, 19. were irregular, 8.9 had a otch, 8.1 had a lucecy, ad 12.2 had a idetatio. I 1.2 of the horses a fragmet was preset, ad i 1.7 a fragmet was suspected. I area II, 90.6 of the metacarpo-/metatarsophalageal joits were ormal, 6.2 were irregular, 2.9 showed a depressio or lucecy, ad the sagittal ridge i 0.2 was flatteed. A fragmet was preset i 0., ad suspected i 0.4. Cliical sigificace: Morphological variatio is preset at the dorsal aspect of the metacarpo-/metatarsophalageal joit i youg Warmblood stallios. These various aspects should be recogised ad described i horses preseted for prepurchase examiatio. However, their cliical relevace i the idividual horse is uclear ad eeds further ivestigatio. Vet Comp Orthop Traumatol 2010; 2: doi:10.415/vcot Received: December 22, 2009 Accepted: May 1, 2010 Pre-published olie: September 9, 2010 Itroductio The dorso-proximal aspect of the equie metacarpo-/metatarsophalageal joit is composed of a thick joit capsule, icludig a syovial pad, a layer of cartilage, subchodral boe, a syovial membrae ad syovial fluid (1 ). Although the exact fuctio of the syovial pad has ot bee studied, its locatio ad structure suggest that it acts as a cotact iterface or cushio betwee the proximal dorsal rim of the proximal phalax ad the dorsal surface of the distal third metacarpal/metatarsal boe (MCIII/MTIII) durig full extesio of the fetlock joit (4). This aatomical regio ca be affected by specific disorders (e. g. osteochodrosis or chroic proliferative syovitis i the metacarpophalageal joit), or it ca be ivolved i a geeralised joit disorder (e. g. capsulitis or syovitis, osteoarthritis, ifectious or traumatic arthritis) (5, 6). A examiatio is frequetly performed prior to the sale of a horse i order to assess the suitability of the aimal for the purpose for which it is required. Depedig o the iteded use ad value of the aimal, a radiographic examiatio may be part of the examiatio. If a decisio is made to take radiographic images, the projectios of the metacarpo-/metatarso-phalageal joits will be icluded (7). Should the veteriaria make a mistake i iterpretig the radiographic images, the ecoomic ad legal cosequeces may be disastrous (7). However, there is a geeral lack of published iformatio regardig the cliical sigificace of may radiographic fidigs, as well as the acceptable aatomical variatios Vet Comp Orthop Traumatol 6/2010

2 412 S. Hauspie et al.: Radiographic features of the dorsal codylar sagittal ridge of MCII/MTIII Fig. 1 Lateromedial radiograph of the fetlock. Two regios were used to categorise the radiographic chages o the distal third metacarpal/ metatarsal boe: A) Area I: proximal third of the visible dorsal aspect of the sagittal ridge, at the level of the syovial pad. B) Area II: distal twothirds of the visible dorsal aspect of the sagittal ridge, the regio distal to the syovial pad ad ot superimposed to the proximal phalax o the lateromedial projectio. (8). Moreover, i additio to the horse s fuctio, the ower s expectatios will largely determie their sigificace (9 11). Because of the differece i type ad duratio of their sportig careers, great cautio should be exercised whe usig the coclusios draw from Thoroughbred horses to iterpret the radiographs of a Warmblood horse (7 9, 12, 1). The goal of this study was to describe the radiographic variatios observed at the dorso-proximal aspect of the sagittal ridge of the MCIII/MTIII ad to assess their relative prevalece i a populatio of youg Warmblood stallios. Materials ad methods The latero-medial radiographic projectios of the metacarpo- ad metatarso-phalageal joits performed o horses preseted at our Istitutio (Ghet Uiversity s Large Aimal Teachig Hospital) as a part of stallio selectio betwee April 2007 ad March 2009 were used. Oly horses youger tha six years were used i this study. A short lameess examiatio was performed: horses were evaluated trottig i a straight lie ad lugig (hard ad soft surface). However, due to the ature of the stallio selectio, a i-depth lameess examiatio, with flexio tests, was ot perform- Fig. 2 Lateromedial radiograph of the fetlock showig the differece i shape of the proximal aspect of the sagittal ridge (area I): A) flat ad smoothly delieated; B) sharp ad smoothly delieated (arrow). The smooth, curved aspect of the distal part of the ridge (area II) is also demostrated (arrowhead). ed. Usig a computed radiography imagig system, radiographs were made with a horizotal radiographic beam ad with the horse bearig weight. The radiographs were evaluated usig commercially available software. If the projectio was excessively oblique defied as superimpositio of the distal codyles of the MCIII/MTIII o the sagittal ridge, ad thus prevetig a thorough radiographic iterpretatio the radiograph was ot used i the study. Two readers a board-certified radiologist (JHS) ad a PhD-studet (SH) reviewed all of the examiatios together, ad each decisio was made cosesually. Special attetio was give to the dorsal aspect of the distal MCIII/MTIII, which was divided ito two areas ( Fig. 1). The first area (area I) correspoded to the proximal third of the visible dorsal aspect of the sagittal ridge, at the level of the syovial pad. The appearace of this area was classified accordig to the followig five categories: ormal (defied as flat or sharp ad smoothly delieated; Fig. 2), irregular, well-defied otch, irregularly shaped lucecies, or a sharply delieated idetatio ( Fig. ) (1, 14). The presece of a fragmet or a suspected fragmet was also oted; if possible, the surface area of the fragmet was measured directly from the latero-medial radiographic projectio without allowace for magificatio. A crude idicatio of the surface area was obtaied by drawig a closed polygo aroud the outer edges of the fragmet ad the calculatig the surface area with commercially available imagig software a. a OsiriX : The secod area (area II) icluded the distal two-thirds of the visible dorsal aspect of the sagittal ridge, which correspods to the regio we assumed to be distal to the syovial pad ad ot superimposed oto the proximal phalax o the latero-medial projectio. For this area, the shape of the sagittal ridge was recorded as: ormal (smooth, curved ridge) ( Fig. 2), irregular, showig a depressio or lucecy, or flatteed ( Fig. 4). The presece or suspicio of a fragmet, as well as its characteristics, was also recorded. If the fragmet was close to (less tha 1 mm) the dorso-proximal aspect of the proximal phalax, the fragmet was cosidered to be a fragmet at the dorso-proximal aspect of the proximal phalax ad, therefore, it was scored like other radiographic abormalities (1 15). Statistical aalysis was performed to determie if there was a differece betwee left ad right metacarpo-/metatarso-phalageal joits ad betwee the fore- ad hidlimbs. Statistical aalysis was performed usig the chi-square test (or the Fisher's exact test if sample sizes were small). Results Aimals A total of 122 radiographs of metacarpo-/ metatarso-phalageal joits of 08 stallios were available for this retrospective evaluatio. The mea age of the populatio was 2.75 years ( Fig. 5). Noe of the horses showed lameess. Twety-eight radiographs were excluded from the study because of excessive obliquity. I total, 1204 Vet Comp Orthop Traumatol 6/2010 Schattauer 2010

3 S. Hauspie et al.: Radiographic features of the dorsal codylar sagittal ridge of MCII/MTIII 41 Fig. Lateromedial radiograph of the fetlock showig chages recorded at the proximal aspect of the sagittal ridge (area I): A) irregular; B) otch; C) lucecy; D) idetatio. Fig. 4 Lateromedial radiograph of the fetlock showig chages recorded at the distal aspect of the sagittal ridge (area II): A) irregular; B) depressio or lucecy; C) flatteed. radiographs were used for iterpretatio: 594 were of forelimbs ad 610 were of hidlimbs. Radiographic fidigs i area I The radiographic fidigs are summarised i Table 1. I area I, 51.5 ( = 620) of the distal MCIII/MTIII had a ormal appearace, 19. ( = 22) were irregular, 8.9 ( = 107) had a otch, 8.1 ( = 98) had a lucet area, ad 12.2 ( = 147) had a well-defied idetatio ( Fig. ). There were ot ay sigificat differeces foud betwee left ad right metacarpo- ad metatarsophalageal joits. A sigificat differece (p <0.0001) was foud betwee forelimbs ad hidlimbs: a idetatio was more ofte preset i the hidlimbs tha i the forelimbs. I 1.2 ( = 15) of the joits, a fragmet was preset always dorsal to, or partially superimposed o the sagittal ridge. The appearace of the sagittal ridge was evely distributed over the five categories. The shape of the fragmet varied from liear to oval, with a mea surface of 0.09 cm 2 (from cm 2 to cm 2 ) ( Fig. 6A). I 1.7 ( = 20) of the joits, the presece of a fragmet was suspected always completely superimposed o the sagittal ridge ( Fig. 6B). I this case, the appearace of the sagittal ridge was mostly ormal to irregular. Oe horse had a fragmet i both forelimbs ad oe horse had a fragmet i the left forelimb ad hidlimb. Radiographic fidigs i area II The radiographic fidigs are summarised i Table 1. I area II, 90.6 ( = 1091) of the joits had a ormal appearace, 6.2 ( = 75) were irregular, 2.9 ( = 5) had a depressio or lucecy at the sagittal ridge, ad the sagittal ridge was flatteed i 0.2 ( = ). No sigificat differeces were foud betwee left ad right joits. A sigificat differece (p <0.0001) i appearace of the distal part of the sagittal ridge was foud betwee forelimbs ad hidlimbs, with more depressio or lucecy preset at the hidlimbs compared to the forelimbs. A fragmet was preset i 0. ( = ) of the joits ad was superimposed o the sagittal ridge. A depressio was preset at the level of the ridge i oly oe of the joits presetig a fragmet. Although they were located more tha 1 mm from the dorsoproximal aspect of the proximal phalax, it was suspected that the other two fragmets may have origiated from the dorsoproximal aspect of the proximal phalax. The fragmets varied from liear ( = 2) to oval ( = 1), with a mea surface of cm 2 (from 0.06 cm 2 to cm 2 ) ( Fig. 7A). A fragmet was suspected i Schattauer 2010 Vet Comp Orthop Traumatol 6/2010

4 414 S. Hauspie et al.: Radiographic features of the dorsal codylar sagittal ridge of MCII/MTIII five other cases; all were superimposed o the sagittal ridge ad without a cocurrig lesio at the level of the sagittal ridge ( Fig. 7B). Other radiographic abormalities A osseous remodellig or cocavity at the dorso-distal aspect of the MCIII boe, just proximal to the sagittal ridge, was see i 12 joits ( Fig. 8). This was a bilateral fidig i five horses. Of these 12 joits, seve did ot have ay other radiographic abormalities. I two joits (both forelimbs of the same horse) a otch was preset i area I, oe joit had a fragmet at the dorsoproximal aspect of the proximal phalax, ad a mieralisatio was detected at the level of the distal sesamoidea ligamets i 2 joits (forelimbs of the same horse). Other abormalities were osteochodral fragmets i joits (2.6) at the dorsoproximal aspect of the proximal phalax (2 horses, 5 of which had two limbs affected). Discussio I our study, there was a lot of variatio at the level of the dorso-proximal aspect of the sagittal ridge of the MCIII/MTIII. I a previous study performed o Thoroughbred horses, it was stated that these variatios have o implicatios for future performace i sport (1). It is temptig to extrapolate these coclusios. However, i cotrast to the populatio of Thoroughbred horses used for racig, our populatio cosisted of Warmblood horses used primarily for jumpig or dressage (1). Compressive strais at the dorsal aspect of the MCIII/ MTIII have bee show to be more prevalet i racehorses workig at high speed, whereas dressage or jumpig horses which usually work at a lower level of impact have a differet directio of strai, a loger sports career, ad the possibility of other coformatio shows as well (16 18). Fig. 5 Age (years) distributio of the horses. Fig. 6 Lateromedial radiograph of the fetlock showig the presece A) or the suspected presece B) of a fragmet i area I. Table 1 Radiographic fidigs i metacarpo- ad metatarsophalageal joits i youg Warmblood stallios. Left forelimb Right forelimb Left hidlimb Right hidlimb Total Category Area 1 Normal Irregular Notch Lucecy Idetatio Area 2 Normal Irregular Depressio / Lucecy Flatteed Excessive obliquity Key: = umber. Vet Comp Orthop Traumatol 6/2010 Schattauer 2010

5 S. Hauspie et al.: Radiographic features of the dorsal codylar sagittal ridge of MCII/MTIII 415 Fig. 7 Lateromedial radiograph of the fetlock showig the presece A) or the suspected presece B) of a fragmet i area II. Fig. 8 Lateromedial radiograph of the fetlock showig a osseous cocavity just proximal to the sagittal ridge. I our study, 55 of the forelimbs ad 46 of the hidlimbs showed a ormal appearace of the dorso-proximal aspect of the sagittal ridge (area I), compared to 72 ad 75, respectively, i a previous study of Thoroughbreds (9). Besides the differece i breed, this differece i percetages ca be explaied by the use of additioal parameters (irregular ad idetatio) i the preset study. If the metacarpo-/metatarso-phalageal joits with a irregular outliig are cosidered to be ormal, 77 of the forelimbs ad 65 of the hidlimbs fall ito this category, which correspods more closely to the previous study (9). The presece of a otch was a bilateral fidig i 2. of the forelimbs ad i 27.7 of the hidlimbs of the horses i our study. This is i cotrast to the result of a previous study i which this fidig was bilateral i 65 of the horses (9). A lucecy was preset i 47 forelimbs ad 5 hidlimbs, ad was a bilateral fidig i two horses ad five horses, respectively. This is i agreemet with the study of Kae et al. i which a lucecy was most ofte a uilateral fidig (9). I the distal part of the sagittal ridge (area II), a differece betwee forelimbs ad hidlimbs was preset. For the forelimbs, our study foud a higher percetage of ormal joits compared to a previous study (95 i our study versus 78 i the previous study). However, for the hidlimbs, our study foud a lower percetage of ormal joits (86 i our study versus 98) (9). I aother populatio of Warmblood horses, 6.8 of the metacarpo-/ metatarso-phalageal joits had a irregular surface of the sagittal ridge ad oe percet had a well-defied depressio much less tha i our study (19). I additio, withi the populatio from the other study, a fragmet was preset at the level of the sagittal ridge i 1. of the cases, compared to 0. i our study (19). A depressio or lucecy was sigificatly more frequet i this area i the hidlimbs. This fidig is compatible with osteochodrosis ad is i accordace with a previous study of a populatio of Stadardbred trotters (20). I this area, the heritability of osteochodrosis has bee demostrated for both flatteed boe cotours ad fragmets (21). A boe fragmet was more frequetly suspected tha cofirmed i both areas I ad II. The difficulty i detectig a fragmet ca be due to poor fragmet opacificatio, superimpositio o other boy structures, or variatio i soft tissues (22). Additioal projectios ca partially address this problem, but they are ot part of the stadard radiographic protocol for the stallio selectio at this istitute. Ultrasoography has bee show to be superior to radiography for detectig ad characterisig dorsal boe fragmets (2). However, performig a ultrasoographic examiatio i stallios for screeig purposes is urealistic. Other techiques such as arthroscopy, computed tomography or MRI may also eable detectio of boe fragmets (2 25). However, due to their cost ad ivasiveess, the use of these techiques is eve less realistic i equie selectio. As metacarpo- ad metatarso-phalageal joit fragmets may have a ifluece o a horse s future lameess, it is importat to detect them early (26). Radiography remais the diagostic method of choice for the practitioer because of its low cost ad high availability versus other imagig modalities (27). I 2 horses (7.2), a fragmet was preset at the dorso-proximal aspect of the proximal phalax. These fragmets were foud i 15 forelimbs ad 18 hidlimbs. These results cotrast with studies of Thoroughbreds ad Stadardbred trotters, i which most of the proximal phalax fragmets were located i the forelimbs (20, 28). However, i aother study of Warmblood horses, the dorsal fragmets were evely distributed betwee the forelimbs ad hidlimbs as i our study (26). Oly oe projectio (latero-medial) was used i the preset study, thus small fragmets superimposed to the sagittal ridge may have bee missed. I 12 metacarpo-/metatarso-phalageal joits, all of which were forelimbs, a osseous cocavity was preset just proximal to the sagittal ridge. Dabareier et al detected Schattauer 2010 Vet Comp Orthop Traumatol 6/2010

6 416 S. Hauspie et al.: Radiographic features of the dorsal codylar sagittal ridge of MCII/MTIII this radiographic fidig i 9 of a populatio of horses with joit syovial pad proliferatio which was affectig the forelimbs (2). If we assume that this radiographic sig is idicative for syovial pad proliferatio i our horses ad compare the results, some differeces are preset. I our study, this radiographic abormality was maily a bilateral fidig i 71 (5 out of 7) of the horses, while i the study of Dabareier et al, this was a uilateral fidig i 79 (50 out of 6) of the horses (2). I the study of Dabareier et al, all of the horses had lameess, joit effusio, or both sigs associated with oe or both metacarpophalageal joits (2). These fidigs were ot preset i our study. O the other had, this radiographic feature could also represet a aatomical variatio i Warmblood horses istead of beig a sig of syovial pad proliferatio. Refereces 1. Deoix JM, Jacot S, Bousseau B, et al. 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