Review article — Oorsigartikel

Elbow dysplasia in the dog: pathophysiology, diagnosis and control

R M Kirbergera and S L Fouriea

incongruity, probably as result of ABSTRACT small growth abnormalities of the long Elbow dysplasia is a non-specific term denoting abnormal development of the elbow. Elbow making up the elbow joint32. The dysplasia encompasses the clinical and radiographic manifestation of ununited anconeal cartilaginous growth disturbance is likely process, fragmented medial coronoid process, dissecans, erosive cartilage to have genetic and environmental, lesions and elbow incongruity. The net result is elbow arthrosis, which may be clinically mainly traumatic, and nutritional inapparent or result in marked lameness. These conditions may be diagnosed by means of causes31. The most important nutritional routine or special radiographic views and other imaging modalities, or the precise cause of factors are an excess supply of energy and the arthrosis or lameness may remain undetermined. Breeds most commonly affected are 31 the rottweiler, Bernese mountain dog, Labrador and golden retriever and the German relative over-nutrition with calcium . shepherd dog. Certain breeds are more susceptible to a particular form of elbow dysplasia Trauma is usually minimal and associated and more than 1 component may occur simultaneously. The various conditions are thought with hyperactivity or excessive body 31 to result from of the articular or physeal cartilage that results in disparate weight . Figure 1 denotes the relationship growth of the radius and . Heritability has been proven for this polygenic condition of factors involved in elbow dysplasia and and screening programmes to select suitable breeding stock have been initiated in several the development of arthrosis. Severe countries and have decreased the incidence of elbow dysplasia. trauma resulting in premature closure of Key words: elbow dysplasia, elbow incongruity, fragmented medial coronoid process, a physis is a separate clinical entity osteochondritis dissecans, ununited anconeal process, screening programmes. causing severe growth disturbance of the affected long that may markedly Kirberger R M, Fourie S L Elbow dysplasia in the dog. Journal of the South African Veterinary Association (1998) 69(2): 43–54 (En.). Department of , Faculty of Veterinary Science, influence joints adjacent to the trauma- University of Pretoria, Private Bag X04, Onderstepoort, 0110 South Africa. tised physis, and is excluded from the elbow dysplasia syndrome. Elbow dysplasia is a worldwide problem in intermediate and heavy-set INTRODUCTION resulting in mild arthrosis may be present breeds and is commonly seen in South Elbow dysplasia is the abnormal with no clinical evidence and breeders are Africa in the rottweiler, Labrador and development of the elbow joint. The term unaware of the problem in their breeding golden retriever, and dysplasia is derived from the Greek words stock36. In a study of rottweilers, 57 % of dog. Other breeds commonly affected dys meaning abnormal and plasia mean- dogs had radiographic signs of elbow worldwide are the Bernese mountain ing development. Elbow dysplasia is an dysplasia but only 15 % were lame36. dog, Saint Bernard, Newfoundland, all-encompassing term comprehensible to Developmental elbow abnormalities and bull mastiff. The condition is seen the dog-breeding fraternity and has included in the term elbow dysplasia are sporadically in many other breeds. Breeds gained popular recognition, particularly fragmented medial coronoid process may be predisposed to a particular form in communicating scientific information (FMCP), osteochondrosis and osteochon- of elbow dysplasia, e.g. the German to the public2,10,40. In scientific publica- dritis dissecans (OCD) of the medial shepherd dog suffers more from UAP16, tions, however, specific aetiologies should humeral condyle, ununited anconeal the rottweiler rarely has OCD11,17 and be referred to where possible10 or, if only process (UAP), humero-ulnar, humero- the Labrador retriever is most likely to secondary arthritic changes are seen on radial and radio-ulnar incongruity and have combined OCD and FMCP17. The routine radiographic views with no articular cartilage erosion. These condi- condition is more likely to occur in males, evidence of the primary cause, the term tions, singly or in combination, result in probably owing to their faster rate of elbow arthrosis should be used40. As irreversible elbow arthrosis with resultant growth or a sex-linked factor5,11,17,20. Elbow elbow dysplasia is a developmental pain and lameness. Osteochondrosis, the dysplasia is a polygenic and multifactorial condition, clinical signs are usually seen disturbed endochondral ossification of condition, the incidence of which can from 4–8 months and are followed by articular or physeal cartilage, is most likely be reduced by selective breeding15,20,40. elbow arthrosis. Long-standing elbow the underlying cause for all the conditions Affected dogs are more likely to have arthrosis due to undetected elbow included in elbow dysplasia31-33. Under- offspring with dysplastic than dysplasia may only be diagnosed later in development of the trochlear notch with normal dogs. The greater the degree of life. In particular, lameness in both secondary incongruity is postulated by arthrosis in the parents, the greater elbows may result in a peculiar gait that others to be the primary cause45,47,50. In percentage of puppies are likely to suffer the owner may not have realised was osteochondrosis, normal cartilaginous from the condition. abnormal. Often minor elbow dysplasia development and maturation fails in the Recognition of the condition by veteri- hypertrophic zone, resulting in thickened narians and breeders and the institution cartilage31. In the elbow joint, articular of screening and breeding programmes aRadiology Section, Department of Surgery, Faculty of Veterinary Science, University of Pretoria, Private Bag cartilage involvement results in OCD are required to decrease the incidence of X04, Onderstepoort, 0110 South Africa. while non-articular cartilage alterations this often crippling disease. Elbow Received: January 1998. Accepted: March 1998. are assumed to result in FMCP, UAP and dysplasia is a progressive disease and

0038-2809 Jl S.Afr.vet.Ass. (1998) 69(2): 43–54 43 Fig. 1: Flow diagram of interrelationship between elbow dysplasia and elbow arthrosis. owners must be made aware that medical shoulder and elbow32. In the rottweiler, allows for the most accurate evaluation of or surgical treatment may result in the palmar metacarpal region should be joint incongruity but true lateral improvement but not normality48. The evaluated to exclude palmar metacarpal positioning is vital. Humeral condyles can objective of this article is to review the sesamoid pathology36. Radiographs of the be evaluated for OCD but minor changes pathophysiology and diagnosis of the rest of the limb may be required to exclude may not be detected. The medial coronoid various conditions involved in elbow other conditions such as panosteitis. process is seen superimposed on the dysplasia, briefly consider therapy and proximal radius with its cranial tip at the discuss measures to prevent and control Radiography level of the radial physis. Osteophyte the condition. Optimal radiographic detail is essential reactions on the cranial aspect of the joint to accurately evaluate elbow pathology. are seen more readily than in the flexed This is obtained by using table-top ML view. Early osteophyte formation DIAGNOSTIC IMAGING TECHNIQUES techniques, non-grid exposures, dorsally on the anconeal process may be Good quality, well-positioned radio- collimating to the elbow joint, centring obscured by the medial humeral condyle, graphs remain the most cost-effective the primary beam on the medial particularly on suboptimal radiographs. method of diagnosing elbow dysplasia. epicondyle of the , using detail- Radiographs, however, do not show all intensifying screens and short-scale Lateral recumbency – mediolateral view abnormalities or are often only suggestive contrast (low kVp and high mAs exposure with the joint maximally flexed (flexed of an abnormality. This is often the case technique). Sedation or anaesthesia may ML) (Fig. 2b) in the growing dog when arthrosis has be indicated for accurate positioning. The angle between the humerus and not yet developed. Three-dimensional Standard craniocaudal and mediolateral radius and ulna is about 45°. This view imaging techniques such as computed views have been supplemented by maximally exposes the anconeal process tomography (CT) and magnetic resonance numerous additional views in an attempt and thus optimises visibility of UAP and imaging (MRI) are the most reliable to highlight certain anatomical locations early osteophyte formation within the methods, as they allow slices of the or pathological conditions. Minor lesions dorsal hollow of the anconeal process. affected joint to be evaluated. Linear such as erosion of the medial humeral This view does not contribute much to the tomography has also proven to be of condyle cartilage will not be visible in any demonstration of OCD and FMCP com- benefit9,44. Positive contrast arthrography, of these views. Microfocal radiography pared to the other views44. although technically fairly easy to per- of the elbow has been described and form, does not contribute to evaluating yielded more information than standard Lateral recumbency – mediolateral view FMCP but could assist in the diagnosis of radiography but some lesions were still with the joint maximally extended and OCD27. The contralateral elbow should not detectable and this is not a readily the limb supinated approximately 15° always be imaged because of the high available technique19. (extended supinated ML = incidence of bilateral disease or as a Cd75°MCrLO)30,44 (Fig. 2c) control11,26,32,48. If the origin of a forelimb Lateral recumbency – routine mediolat- This projection results in a true lateral lameness is uncertain, shoulder radio- eral view of the joint (semi-flexed ML) view of the medial coronoid process. The graphs should also be made to exclude (Fig. 2a) radiograph allows the cranial border of OCD of this region. A small number of The angle between the humerus and the medial coronoid process to be seen in dogs may have lesions in both the radius and ulna is about 110°. This view 94 % of cases as compared to 50 % and

44 0038-2809 Tydskr.S.Afr.vet.Ver. (1998) 69(2): 43–54 a b

c d

e f

Fig. 2a: Lateral recumbency – mediolateral view with the joint semi-flexed (ML). Fig. 2b: Lateral recumbency – mediolateral view with the joint maximally flexed (flexed ML). Fig. 2c: Lateral recumbency – mediolateral view with the joint extended and the limb supinated approximately 15° (extended supinated ML=Cd75°MCrLO). Fig. 2d: Sternal recumbency – true craniocaudal view (CrCd). Fig. 2e: Sternal recumbency – craniolateral to caudomedial oblique view (Cr30°LCdMO). Fig. 2f: Sternal recumbency – craniomedial to caudolateral oblique view (CrMCdLO).

0038-2809 Jl S.Afr.vet.Ass. (1998) 69(2): 43–54 45 56 % respectively in the semi-flexed ML and flexed ML views30. One study proved this view to be more reliable in detecting FMCP than the ML view31.

Sternal recumbency – true craniocaudal view (CrCd) (Fig. 2d) Useful to detect osteochondral defects of the medial humeral condyle but some lesions may only be seen in the extended supinated ML view, or if they are located more cranially, only in the ML view44. Osteophyte reactions on the medial humeral epicondyle and medial coronoid process are readily seen.

Sternal recumbency – craniolateral to caudomedial oblique views (Cr30°LCdMO)30,44 (Fig. 2e) This view is also known as the pronated CrCd view and is used to skyline the medial coronoid process and medial humeral condyle. The cranial aspect of the Fig. 3: Computed tomography transverse cross-section of the radius and ulna, illustrating medial coronoid process is seen en face in a fragmented medial coronoid process (arrow) (courtesy of P Steyn, Colorado State this view making it difficult to see University). cleavage lines30. Osteophyte reactions on the medial humeral epicondyle and medial coronoid process and osteochon- Computed tomography (Fig. 3) Magnetic resonance imaging dral defects of the medial humeral Computed tomography is significantly Owing to cost considerations, MRI is condyle are readily seen. more accurate than radiography, linear rarely used for elbow evaluations but is tomography and xeroradiography for the more accurate and sensitive than radio- Sternal recumbency – craniomedial to diagnosis of FMCP owing to its exceptional graphs for the detection of FMCP and OCD. caudolateral oblique view (CrMCdLO)44 contrast resolution and ability to image Additionally it allows non-displaced, (Fig. 2f) the medial coronoid process in a 3rd non-mineralised fragments to be seen39. Also known as the supinated CrCd view plane6. Non-mineralised cartilage frag- and highlights the lateral humeral con- ments occur more commonly than Linear tomography (Fig. 4) dyle and as such does not contribute to mineralised cartilage fragments and are Linear tomography is a useful the evaluation of conditions involved in much more likely to be seen with CT than technique to demonstrate potential elbow dysplasia. with radiographs6. disease areas that are obscured by super-

a b

Fig. 4a: ML linear tomography image of a normal medial coronoid process (arrow). Fig. 4b: ML radiograph of same dog. Note improved visibility of medial coronoid process in Fig. 4a.

46 0038-2809 Tydskr.S.Afr.vet.Ver. (1998) 69(2): 43–54 imposed structures. Linear tomography is performed in the extended supinated ML view at the level of the medial coronoid process with the tube movement perpen- dicular to the axis of the leg and a swing angle of 40° 44. The technique is used to see FMCP not visible in other views9,44 and may detect up to 30 % more FMCP cases44. Another study showed no significant difference between linear tomography and radiographs but the combination of the 2 imaging modalities approached an accuracy similar to CT for detecting FMCP6.

CLINICAL CONDITIONS Clinical signs are usually seen from 5–6 months of age. A stiff, slightly stilted fore- limb gait after rest progresses to lameness after exercise and pain on flexion and extension of the elbow joint33. The lower limb and elbow are slightly abducted and supinated. As clinical signs are mild and insidious, the patient is often only Fig. 5: ML view with 2 separate medial coronoid fragments (arrows) superimposed on the proximal radius, and severe arthrosis. presented at about 6–9 months and after having been lame for 3–4 weeks11,33. Occasionally dogs are only presented in pathology occurs in both32. Fragmented changes are most likely to be seen in the later life due to bilateral arthrosis33. The medial coronoid process is thus extended supinated ML and pronated inciting condition results in an inflamma- commonly seen together with OCD6 or CrCd (Fig. 6b) views. Radiographic tory reaction within the joint and erosive lesions and rarely with UAP. The changes are often seen only from about 7 arthrosis33 and the primary cause is often disparate growth may still be evident at months and then secondary arthritic only established after arthrotomy17 or the time of presentation or may have changes may be all that are seen11,32,33. The arthroscopy1. corrected itself. arthritic changes are similar to those caused by other conditions (see below). Fragmented medial coronoid process Radiographic changes Osteophyte reactions tend to be less se- The medially located fragment should vere than with UAP and more severe than Pathophysiology not be confused with the sesamoid bone with OCD26. Joint incongruity may also be Fragmentation of the medial coronoid in the origin of the supinator muscle evident, with the lateral coronoid process process is believed to be a manifestation on the lateral side or with osteophyte displaced proximally to the radial head, of the osteochondrosis complex26,33 and is formation on the medial coronoid resulting in step formation (Fig. 7). If the most common clinical entity causing process. The fragment is rarely seen on more sophisticated imaging techniques elbow arthrosis14. The cartilaginous radiographs24,26,32, with fragment visibility are not available, the diagnosis can medial coronoid process ossifies from its reported as low as 9.8 %13. If visible, it may often only be confirmed by means of base to the tip, i.e. it has no separate be seen as a single loose fragment or as arthrotomy or arthroscopy1,43. Arthro- ossification centre, and ossification is several smaller fragments (Fig. 5). Factors scopy allows excellent visualisation of completed at 20–22 weeks33. Osteochon- contributing to poor or non-visualisation joint incongruity, free fragments, joint drosis results in the inability of the deeper of the fragment include partial fragmen- mice, abrasions, fissures and osteophyte chondrocytes in the thick layer of cartilage tation, minimal fragment displacement30, formation of the medial coronoid to survive, and they undergo chondro- small fragment, fragment location process1. Dogs presented with clinical malacia with eventual fissuring of the between the radial head and remaining evidence of an elbow problem at less than cartilage and subsequent fragmentation26. intact coronoid process31, or that the 7 months of age with normal radiographs The fragment often mineralises as a result fragment cleavage line is often oblique to should undergo arthroscopy1 or must of receiving blood supply through its the X-ray beam, making it impossible to return for follow-up radiographs 4–8 fibrous connection with the annular see30,48. Additionally, the medial coronoid weeks later32. ligament, which inserts on the coronoid process may be only fissured1,14,24,31 and process33. Mechanical stresses have also non-displaced, non-mineralised39 or Treatment been incriminated as a cause of FMCP33. abnormally shaped24, making radio- Surgical exploration by means of A recent popular hypothesis postulates graphic evaluation impossible and arthrotomy, or preferably , asynchronous growth of the radius and requiring more sophisticated imaging with the removal of fragments is ulna32. Overgrowth of the ulna relative to techniques. Additional radiographic recommended in dogs less than 1 year old the radius appears to be the main cause of changes that may be indicative of medial before the development of severe FMCP32. It places an abnormal load on the coronoid pathology include loss of sharp arthrosis1,12,26,28,48. Older dogs with exten- medial humeral condyle and medial delineation of the cranial edge of the sive arthrosis may improve clinically coronoid process and if these structures medial coronoid (Fig. 6a) or blunting of after surgery26. Weight control, exercise are weakened by delayed ossification, the coronoid process3. Medial coronoid restriction and analgesic therapy are all

0038-2809 Jl S.Afr.vet.Ass. (1998) 69(2): 43–54 47 a b

Fig. 6a: ML view of 8-month-old German shepherd dog with poorly-visible medial coronoid process, degenerative changes and mild joint incongruity. Fig. 6b: Slightly pronated CrCd view of same dog with separate medial coronoid fragment (arrows).

Osteochondritis dissecans of the medial humeral condyle

Pathophysiology The pathophysiology is very similar to that described for FMCP. Osteochondritis dissecans without concomitant FMCP is very rare6. The cartilage flap rarely mineralises33. The cartilage flap may separate and form a joint mouse.

Radiographic changes The defect is readily seen in the CrCd or pronated CrCd views as a radiolucent lesion (Fig. 8a) or dished-out defect on the medial humeral condyle and may be seen from 5–6 months of age and prior to secondary arthrosis5,11,33. In more advanced cases the defect may be surrounded by a sclerotic rim32. In ML views it may be seen as a flattening of the caudodistal edge of the medial humeral trochlea47 Fig. 7: Sagittal computed tomography images to illustrate proximal displacement of lateral (Fig. 8b). If OCD is the sole lesion, coronoid process (arrow) in relation to caudal radial head and incongruent humero- arthrosis is less marked than with FMCP ulnar joint space (courtesy of P Steyn, Colorado State University). alone11,21 but clinical signs may occur earlier and may be more disabling than important additional therapeutic aids26,48. but a more rapid recovery in the medi- FMCP on its own21. Combined OCD and Owners should be made aware of the cally treated cases4. Radiographic and FMCP lesions result in the most severe progressive nature of the condition. range of motion scores, however, still arthrosis17,21. Several surgical approaches are possible showed progression of arthrosis. A study but muscle separation between the comparing surgery to treatment with rest Treatment pronator teres and flexor carpi radialis and aspirin had similar results23. In early Surgical exploration and removal of currently appears to be the method of cases with a step between the radial head fragments followed by curettage is choice28. Other studies cast doubt on the and the coronoid process, a proximal ulna performed as described for FMCP. The benefits of surgery. A study comparing sliding osteotomy will reduce the incon- medial coronoid process should be surgical to medical treatment with gruency1. Treating the incongruency is evaluated at the same time. pentosan polysulphate showed no probably more beneficial than removing Medical treatment is the same as for difference in clinical status after 9 months, the fragment. FMCP. Surgical results may be better than

48 0038-2809 Tydskr.S.Afr.vet.Ver. (1998) 69(2): 43–54 a b

Fig. 8a: CrCd view with a triangular radiolucent defect in the medial humeral condyle (arrows) in a 4-month-old boerboel with bilateral elbow OCD. Fig. 8b: ML view of same dog with flattening of the medial condyle (arrows). for FMCP, particularly if surgery is Ununited anconeal process surgical approaches are different6,24,50. performed at a young age12. Pathophysiology Radiographic changes Erosive lesion/cartilage defect The condition occurs mainly in the The condition is readily seen in German shepherd dog16,18,38. The separate flexed ML view as an irregular vertical Pathophysiology ossification centre of the anconeal radiolucent line through the caudal An erosive lesion or cartilage defect is process, only present in larger breeds, aspect of the anconeal process (Fig. 9a). seen most commonly on the medial appears at 11–14 weeks and the anconeal Superimposition of the medial humeral humeral condyle and occasionally on the process is united with the olecranon at epicondyle physis in views that are not medial coronoid process1,14,32 and probably 20–22 weeks (greyhound 14–15 weeks, fully flexed should not be confused with has the same aetiology as FMCP and OCD German shepherd dog 16–20 weeks)33,41. a UAP in dogs less than 8 months old7. and is due to ulnar overgrowth32. It may The ununited anconeal process may be The fragment may separate completely not be possible macroscopically to completely separated or joined to the ulna from the olecranon (Fig. 9b). Arthritic determine if a medial humeral condyle by fibrous or fibrocartilagenous tissue38,41. changes become severe over time. It is lesion is primary osteochondrosis or a Overgrowth of the radius with a relatively essential to make multiple views to ensure secondary erosive lesion and histopathol- shorter ulna is postulated by Olsson22 to no other causes of elbow arthrosis are ogy may be required32. Erosive lesions be the cause. The radius forces the hu- present7. commonly accompany FMCP17. Erosive meral trochlea in a proximal direction and lesions are postulated to occur rather the floor of the olecranon fossa exerts Treatment than FMCP or OCD if the ulnar growth more pressure than normal on the an- Conservative therapy is unrewarding disparity occurs at a slightly older age when coneal process, damaging the anconeal and results in persistent lameness and the medial coronoid process and medial process ossification centre. If osteochon- progressive arthrosis18,37. Surgical therapy humeral condyle cartilage are almost drosis is present, the entire structure is less is the treatment of choice but at present no mature32. Alternative hypotheses are that resistant to trauma and a tear in the technique can ensure a functionally minor joint incongruity may result in the weakened cartilage prevents osseous normal joint7. Surgical excision via a lesions48 or that they are earlier stages of bridging of the gap32. In 2 separate lateral arthrotomy has been the tradi- FMCP and OCD14. These lesions are also studies, measurements made of the tional treatment. This, however, results known as ‘kissing’ lesions but Olsson olecranon in German shepherd dogs with in instability with progressive arthrosis, differentiates this from an erosive lesion32. UAP showed a significantly shorter but if performed early, results in accept- olecranon or proximally displaced radius able longterm function7,16,37. Surgical Radiographic changes in affected limbs18,38. Weis45 and Wind47, on re-attachment by means of a lag screw Lesions are not seen on radiographs of the other hand, propose a hypothesis of a aims to prevent arthrosis by providing affected joints13 but secondary arthrotic primary incongruent joint with an stability7. This technique may, however, changes may be seen. abnormally developed slightly elliptical aggravate arthritic changes if incongruity trochlear notch causing UAP (see elbow caused by asynchronous growth is Treatment incongruity). Ununited anconeal process present. Proximal ulnar osteotomy is a Surgical removal of affected cartilage is is rarely seen together with FMCP but, if recently-proposed technique that aims to recommended32. present, has important implications as the redress joint incongruity caused by

0038-2809 Jl S.Afr.vet.Ass. (1998) 69(2): 43–54 49 a b

Fig. 9a: Flexed right elbow ML view of a 2-year-old German shepherd with bilateral ununited anconeal process. The dog had a history of being mildly lame in the left front limb. Note vertical radiolucent line through anconeal process and secondary osteophyte formation. Visibility of pathology can be enhanced by making a fully flexed ML view. Fig. 9b: Flexed left elbow ML view of same dog. Note cranially displaced united anconeal process (arrows). asynchronous radius or ulnar growth7,32. Intermediate and heavy-set breeds have notch46,47 (Fig. 10). These changes are well Results appear good, with olecranon a longer proximal ulna relative to the illustrated in a radiographic guide of the fusion taking place in up to 95 % of cases38, adjacent radius than in other breeds50. elbow joint49. although in 27 % of these a narrow Wind50 postulated that this reflects a need radiolucent line remained. The clinical to accommodate a trochlear notch of Treatment response appears superior to that sufficient size to encompass a heavier and Treatment is determined by concurrent achieved by the other 2 techniques7,38. larger humeral trochlea. Insufficient FMCP, OCD and UAP, while the trochlear Olsson’s short olecranon/overgrown development of the trochlear notch with notch incongruity is treated conserva- radius hypothesis is supported by the resultant incongruity is thus most likely in tively28. ulnar ostectomy treatment, which these larger dogs50. Incongruity may not relieves the pressure on the anconeal always be evident at the time of radio- Arthrosis process, resulting in fusion of the graphic examination, due to compensa- Arthrosis is a chronic, degenerative, ununited anconeal process with the tory adjustments during growth48. non-infectious joint disease involving ulna32,38. This treatment is unlikely to have According to Olsson32, the incongruity is joint cartilage, joint capsule and subchon- a similar effect in relieving olecranon caused by asynchronous growth as dral bone tissue10. pressure if the UAP was due to trochlear discussed under FMCP. notch with a smaller radius of curvature, Radiographic changes as proposed by Weis45 and Wind47. Radiographic changes Early changes are best seen in the ML In the semi-flexed ML and CrCd view views with osteophyte formation Elbow incongruity of a normal elbow joint there should be commencing on the dorsal anconeal small, even joint spaces between the process and lateral epicondylar ridge, Pathophysiology humeral trochlea and the ulnar trochlear followed by the margins of the cranio- According to Weis45 and Wind47, incon- notch and between the humeral condyle, proximal radius and craniodistal humerus gruity (described under radiographic radius and medial coronoid process of the articular surfaces and sclerosis surround- changes) is due to the trochlear notch ulna47. The joint space forms a continuous ing the trochlear notch24,48 (Figs 5, 6, 9, 11). developing in a slightly elliptic shape with arc in the ML view47. The lateral coronoid The latter tends to start distally and may the articular curvature of the trochlear process should lie close to and run be the result of osteophyte formation at notch too small to fully encompass the continuously with the adjacent proximal the joint capsule insertion or subchondral humeral trochlea. If the incongruity radius47. Incongruity is characterised by a sclerosis or both47. The anconeal osteo- occurs after 6 months it may be present on gap or step formation between the lateral phytes correspond to the insertion of the its own, with only elbow arthrosis coronoid process and the adjacent proxi- olecranon ligament and joint capsule on resulting47. If present before 6 months, mal radius, a more proximally located the proximal non-articular surface of the incongruity may also predispose the dog medial coronoid process, humerus anconeal process24. In CrCd view, osteo- to FMCP, OCD and UAP owing to displaced cranially on the centre of the phytes are seen on the medial humeral increased mechanical forces on these radial articulation, increased humero- epicondyle and on the medial aspect of structures and incongruity may thus be ulnar and humero-radial joint space and the medial coronoid process. Severe seen together with these conditions47. an indistinct outline of the trochlear arthrosis may develop over time and joint

50 0038-2809 Tydskr.S.Afr.vet.Ver. (1998) 69(2): 43–54 mice may be present cranial to the medial coronoid process or in the olecranon fossa14. Arthrosis may be present without any radiographic evidence of a primary cause and could be due to erosive lesions, healed FMCP or minor incongruity.

HERITABILITY Elbow dysplasia is inherited as multifac- torial polygenic traits15,20,34,40, i.e. requires more than 1 gene to cause the phenotype to be expressed in an individual34. A simple autosomal recessive mode of inheritance has been ruled out for the inheritance of OCD and FMCP and they appear to be inherited independently from each other as polygenic traits34. The frequency of elbow arthrosis caused by elbow dysplasia varies from 30–50 %, with males generally more frequently and severely affected15,21. However, in one study in Bernese mountain dogs, the female was shown to be more suscepti- Fig. 10: ML view of 8-month-old German shepherd dog with incongruent elbow joint. 40 ble . Radiographic studies are usually Compare to Fig. 2a. Note slightly proximally displaced lateral coronoid process performed at 12 months. Severely and widened humero-ulnar and humero-radial joint space. Osteophyte reactions affected cases diagnosed at a younger age present and medial coronoid process poorly seen. Three medial coronoid fragments found at surgery. and possibly destroyed are therefore excluded and consequently the incidence of elbow dysplasia may be underesti- mated15. The rottweiler is the breed with the highest incidence but the degree of arthrosis tends to be more severe in the Bernese mountain dog15,22. The risk of developing elbow dysplasia is higher in dogs with affected parents compared to dogs with unaffected parents15,40. Heritability varies from 0.10–0.4815, 0.28– 0.4040, 0.45 (females)20, and 0.77 (males)20. In rottweilers and Bernese mountain dogs, breeding parents that are both normal resulted in a 31 % incidence of elbow dysplasia in the offspring, breeding 1 normal with 1 arthritic parent resulted in 44–48 % of offspring affected and breeding affected parents with each other resulted in 59–62 % of offspring being affected22. In Sweden, concerted efforts to decrease the prevalence of elbow arthrosis have reduced the incidence from 60 to 38 % in the Bernese mountain dog and from 60 to 45 % in the rottweiler over a period of 5 years40. During the same period the incidence of moderate to severe arthrosis decreased from 42 to 14 % in the Bernese mountain dog and from 40 29 to 14 % in the rottweiler . Fig. 11: Schematic illustration of International Elbow Working Group elbow arthrosis Heritability is a definite factor in the grading scheme illustrating osteophyte location in flexed ML and CrCd views. development of elbow arthrosis and elbow joints should be radiographed in susceptible breeds at the same time as hip parents, litter mates and offspring already determine the degree of elbow involve- dysplasia evaluations are performed15. born15,34. ment, with the intent to limit breeding Breeding animals, particularly in with severely affected dogs. Elbow susceptible breeds, should be selected by CONTROL PROGRAMMES grading for degree of arthrosis has been their phenotypic status and by informa- Screening programmes to grade elbow performed by numerous investigators tion on the elbow status of parents, grand- arthrosis have been established to who often devised their own grading

0038-2809 Jl S.Afr.vet.Ass. (1998) 69(2): 43–54 51 a b

c

Fig. 12a: Grade 1 elbow arthrosis. Fig. 12b: Grade 2 elbow arthrosis. Fig. 12c: Grade 3 elbow arthrosis. systems15,17,21,25. Many of these pro- veterinarians, veterinary radiologists, standard2,29. Control programmes in grammes involved certain breeds or geneticists and dog breeders and meets different countries are encouraged to organisations e.g. Bernese mountain dogs annually in different parts of the world to utilise the IEWG criteria when initiating in Switzerland25, Bernese mountain dogs discuss current knowledge and promote screening programmes. The current and rottweilers in Scandinavia15,22,40, elbow screening schemes. More informa- IEWG elbow screening protocol includes rottweilers in Australia36 and Dutch tion on the IEWG can be obtained from submission of permanently-identified seeing-eye dogs42. The grading system their web site at: good quality flexed ML radiographs of does not, however, predict the type of both elbows from 12 months onwards for lesion present and thus does not correlate http://www.vetmed.ucdavis.edu/iewg/ osteophyte evaluation (Fig. 11). The with the degree of lameness that may be iewg.html flexed ML view has been proven to be a evident17. sensitive predictor of elbow arthrosis The International Elbow Working The IEWG has established guidelines resulting from elbow dysplasia even Group (IEWG) was established in 1989 to for elbow screening and these have been though the inciting cause is not always lower the incidence and promote a adopted by the Fédération Internationale evident24. Grading is as follows (Figs 11, 12): greater worldwide understanding of Cynologique and World Small Animal Grade 1 (mild arthrosis) – osteophytes elbow dysplasia. The group consists of Veterinary Association as the official <2 mm anywhere in the elbow but

52 0038-2809 Tydskr.S.Afr.vet.Ver. (1998) 69(2): 43–54 particularly at 1 or more of the following DISCUSSION dogs that have elbow dysplasia as well as sites : Evidence appears to favour osteochon- reduce the incidence of this often a) on the dorsal border of the anconeal drosis in combination with asynchronous crippling disease. process; growth of the radius and ulna to be a b) on the cranioproximal edge of the major contributing factor causing elbow REFERENCES radius; arthrosis. This is corroborated by the small 1. Bardet J F 1997 Arthroscopy of the elbow in c) on the proximal edge of the medial number of cases that have simultaneous dogs. Part II: cranial portals in the diagnosis coronoid process; FMCP and UAP that would, according to and treatment of the lesions of the coronoid d) on the proximal edge of the lateral this hypothesis, tend to be mutually process. Veterinary and Comparative Ortho- paedics and Traumology 10: 60–66 epicondylar ridge; exclusive. However, asynchronous radius 2. Bedford P G C 1994 Control of hereditary e) and/or sclerosis in the area caudal to and ulnar growth could possibly occur elbow disease in pedigree dogs. Journal of the distal end of the ulnar trochlear alternatively with first the ulna and then Small Animal Practice 35: 119–121 notch and the proximal radius. the radius, or vice versa, growing past 3. Berry C R 1992 Evaluation of the canine elbow for fragmented medial coronoid Grade 2 (moderate arthrosis) – osteo- each other. This hypothesis requires process. Veterinary Radiology & Ultrasound phytes 2–5 mm high at 1 or more locations further investigation. The hypothesis of 33: 273–276 as described for grade 1. an abnormally developed slightly ellipti- 4. Bouck G R, Miller C W, Taves C L 1995 A Grade 3 (severe arthrosis) – osteophytes cal trochlear notch proposed by Weis and comparison of surgical and medical treat- >5 mm high in 1 or more locations as Wind seems unlikely to be a major ment of fragmented coronoid process and osteochondritis dissecans of the canine described for grade 1. contributing factor, as combined UAP and elbow. Veterinary and Comparative Orthopae- Osteophytes may also be evaluated on FMCP should then occur in much larger dics and Traumatology 8: 177–183 a CrCd radiograph at the following numbers of dogs and ulnar ostectomy 5. Boudrieau R J, Hohn R B, Bardet J F 1983 locations: would have no effect in cases with UAP7,38. Osteochondritis dissecans of the elbow in f) distal aspect of medial humeral It is, however, also possible that the time the dog. Journal of the American Animal Hospital Association 19: 627–635 condyle; at which incongruency develops may 6. Carpenter L G, Schwarz P D, Lowry J E, g) medial aspect of medial coronoid affect the outcome. Trochlear notch Park R D, Steyn P F 1993 Comparison of process. malformation under 20 weeks of age may radiologic imaging techniques for diagnosis result in UAP, while such malformation of fragmented medial coronoid process of In addition, if the primary pathology is after the anconeal process has fused to the the cubital joint in dogs. Journal of the American Veterinary Medical Association 203: evident it should be noted. Screening ulna could result in FMCP. 78–83 programmes should be performed at Open registries are essential to combat 7. Cross A R, Chambers J B 1997 Ununited a standard and narrow age interval, i.e. elbow dysplasia. Evaluating the progeny, anconeal process of the canine elbow. Com- as close to 12 months as possible, as particularly of sires, will also make a pendium on Continuing Education for the Prac- increasing age has a significant influence marked difference as it has been shown ticing Veterinarian (Small Animals) 19: 349–360 of the prevalence and severity of elbow that there is a lower incidence of elbow 8. Fox S M, Bloomberg M S, Bright R M 1983 40 arthrosis . Dogs with clinical signs of arthrosis in the progeny of unaffected Developmental anomalies of the canine elbow pathology or offspring bred with a sires40. In Sweden, an open registry is elbow. Journal of the American Animal high risk of developing elbow arthrosis sponsored by the Swedish kennel club Hospital Association 19: 605–615 are radiographed at an earlier age so that and has resulted in a marked decrease in 9. Fox S M, Roberts R E 1987 Linear 48 tomography in diagnosing fragmented affected dogs may be submitted for the incidence of elbow arthrosis . In the coronoid processes in canine elbows. Com- surgery before arthrotic changes develop. United States an open registry system for pendium on Continuing Education for the Prac- The benefit versus cost ratio of an elbow elbow dysplasia is controlled by the ticing Veterinarian (Small Animals) 9: 61–65 arthrosis screening programme has been Institute for Genetic Disease Control 10. Grondalen J 1979 Arthrosis with special extensively studied in Sweden40. The cost (GDC) which also maintains open reference to the elbow joint of young rapidly growing dogs. I. Nordisk Veterinær- of screening and registration of dogs for genetic registries for a multitude of other medicin 31: 62–68 elbow dysplasia was found to be less than inherited diseases. The GDC is 11. Grondalen J 1979 Arthrosis with special the value of dogs estimated to have been cooperating with Canada, Australia, reference to the elbow joint of young saved from moderate to severe arthrosis. Japan and has been asked to assist in rapidly growing dogs. II. Nordisk Veterinær- medicin 31: 69–75 Information gained from screening establishing an open registry in Europe as 12. Grondalen J 1979 Arthrosis in the elbow programmes should be available in an ‘shared knowledge is the greatest tool in joint of young rapidly growing dogs. III. 35 open registry system to researchers and the world for understanding’ . Nordisk Veterinærmedicin 31: 520–527 responsible owners to improve the In South Africa, screening programmes 13. Grondalen J 1982 Arthrosis in the elbow selection of breeding stock. It is ideal not should be introduced in predisposed joint of young rapidly growing dogs. VI. Nordisk Veterinærmedicin 34: 65–75 to breed with a dog with any grade of breeds such as the rottweiler, Labrador 14. Grondalen J, Grondalen T 1981 Arthrosis in arthrosis, but this is likely to result in retriever, golden retriever and German the elbow joint of young rapidly growing breeder resistance and breeding shepherd dog. The Kennel Union of dogs. V. Nordisk Veterinærmedicin 33: 1–16 programmes should thus be adapted South Africa, affected-breed clubs, 15. Grondalen J, Lingaas F 1991 Arthrosis in the to the incidence of elbow dysplasia in veterinary clinicians, radiologists and elbow joint of young rapidly growing dogs: a genetic investigation. Journal of Small the breed to ensure breeder compliance. surgeons should combine their resources Animal Practice 32: 460–464 In Australia, rottweilers have a high and expertise to initiate such pro- 16. Grondalen J, Rorvik A M 1980 Arthrosis in incidence of elbow arthrosis and, grammes. Cooperation with the GDC can the elbow of young rapidly growing dogs. in accordance with current IEWG be considered. As conditions involved in IV. Nordisk Veterinærmedicin 32: 212–218 recommendations, it was suggested that elbow dysplasia are being recognised 17. Guthrie S 1989 Use of a radiographic scoring technique for the assessment of dogs with dogs with evidence of grade 2 and 3 earlier and more frequently and some elbow osteochondrosis. Journal of Small elbow arthrosis should not be used for progress is being made in their treatment, Animal Practice 30: 639–644 breeding36. screening programmes will benefit those 18. Guthrie S 1989 Some radiographic and

0038-2809 Jl S.Afr.vet.Ass. (1998) 69(2): 43–54 53 clinical aspects of ununited anconeal Constance, Germany, 1 July 1995: 3–5 40. Swenson L, Audell L, Hedhammar A 1997 process. The Veterinary Record 124: 661–662 30. Miyabayashi T, Takiguchi M, Scrader S C, Prevalence and inheritance of and selection 19. Guthrie S, Buckland-Wright J C, Vaughan Biller D S 1995 Radiographic anatomy of the for elbow arthrosis in Bernese mountain L C 1991 Microfocal radiography as an aid medial coronoid process of dogs. Journal of dogs and rottweilers in Sweden and to the diagnosis of canine elbow ostechon- the American Animal Hospital Association 31: benefit:cost analysis of a screening and drosis. Journal of Small Animal Practice 32: 125–132 control program. Journal of the American 503–508 31. Nap R C 1995 Pathophysiology and clinical Veterinary Medicine Association 210: 215–221 20. Guthrie S, Pidduck H G 1990 Heritability of aspects of canine elbow dysplasia. Proceed- 41. Thacher C 1993 Ununited anconeal process. elbow osteochondrosis within a closed ings of the 7th International Elbow Working In Slatter D (ed.) Textbook of small animal population of dogs. Journal of Small Animal Group Meeting, Constance, Germany, 1 July surgery (2nd edn). W B Saunders, Philadel- Practice 31: 93–96 1995: 6–8 phia: 1977–1981 21. Hazewinkel H A W, Meij B P, Nap R C, 32. Olsson S E 1993 Pathophysiology, morphol- 42. Ubbink G, Hazewinkel H A W, Wolvekamp Dijkshoorn N E, Ubbink G, Wolvekamp W ogy, and clinical signs of osteochondrosis W th C, Rothuizen J, Van de Broek J 1995 1995 Radiographic views for elbow dys- in the dog. In Bojrab M S, Smeak D D, Preliminary results of the genetic analysis of plasia screening in Bernese mountain dogs. Bloomberg M S (eds) Disease mechanisms in the ED program of the Dutch seeing eyes Proceedings of the 7th International Elbow small animal surgery (2nd edn). Lea & dogs. Proceedings of the 7th International Working Group Meeting, Constance, Germany, Febiger, Philadelphia: 777–796 Elbow Working Group Meeting, Constance, 1 July 1995: 29–32 33. Olsson S E 1983 The early diagnosis of Germany, 1 July 1995: 43–45 22. Hedhammar A A 1991 The hereditary as- fragmented coronoid process and osteo- 43. Van Bree H, Van Ryssen B 1995 Diagnostic pects of canine elbow dysplasia. Proceedings chondritis dissecans of the canine elbow and surgical arthroscopy of the canine of the 16th World Small Animal Veterinary joint. Journal of the American Animal Hospital elbow. Proceedings of the 7th International Association Congress, Vienna, Austria, 2–5 Association 19: 616–626 Elbow Working Group Meeting, Constance, October 1995: 578–579 34. Padgett G A, Mostosky U V, Probst C W, Germany, 1 July 1995: 22–23 23. Huibregtse B A, Johnson A L, Muhlbauer Thomas M W, Krecke C F 1995 The 44. Voorhout G, Hazewinkel H A W 1987 M C, Pijanowski G J 1994 The effect of treat- inheritance of osteochondritis dissecans Radiographic evaluation of the canine ment of fragmented coronoid process on and fragmented coronoid process of the elbow joint with special reference to the the development of of the elbow joint in Labrador retrievers. Journal of medial humeral condyle and the medical elbow. Journal of the American Animal the American Animal Hospital Association 31: coronoid process. Veterinary Radiology 28: Hospital Association 30: 190–195 327–330 158–165 24. Keller G G, Kreeger J M, Mann F A, Lattimer 35. Poulos P W 1997 GDC update: current 45. Weis M 1983 Knochenwachstumunter- J C 1997 Correlation of radiographic, status and the role in the international suchungen mittels fluoreszenzmikrosko- necropsy and histologic findings in 8 dogs community. Proceedings of the 8th Interna- pischer, mikroradiographischer und with elbow dysplasia. Veterinary Radiology tional Elbow Working Group Meeting, phasenkontrastmikroskopischer Tech- & Ultrasound 38: 272–276 Birmingham, Great Britain, 2 April 1997: 18– niken am Ellbogengelenk sowie distal an 25. Lang J 1995 Comparison of two classifica- 21 Radius und Ulna beim jungen Hund. Ein tion protocols in the evaluation of elbow 36. Read R A, Armstrong S J, Black A P, Beitrag zur Aetiologie und Pathogenese der disease in the Bernese mountain dog. Macpherson J C, Davey T 1996 Relationship Osteochondrosis des Ellbogengelenkes. Proceedings of the 7th International Elbow between physical signs of elbow dysplasia Inaugural dissertation, Faculty of Veteri- Working Group Meeting, Constance, Germany, and radiographic score in growing nary Medicine, University of Zurich 1 July 1995: 37–38 rottweilers. Journal of the American Veterinary 46. Wind A P 1982 Incidence and radiographic 26. Lewis D D, Parker R B, Hager D A 1989 Medical Association 209: 1427–1430 appearance of fragmented coronoid Fragmented medial coronoid process of the 37. Roy R G, Wallace L J, Johnston G R 1994 A process. California Veterinarian 6: 19–25 canine elbow. Compendium on Continuing retrospective long-term evaluation of 47. Wind A P 1986 Elbow incongruity and de- Education for the Practicing Veterinarian ununited anconeal process excision on the velopmental elbow diseases in the dog: Part (Small Animals) 11: 703–715 canine elbow. Veterinary and Comparative I. Journal of the American Animal Hospital 27. Lowry J E, Carpenter L G, Park R D, Steyn Orthopaedics and Traumatology 7: 94–97 Association 22: 711–724 P F, Schwarz P D 1993 Radiographic 38. Sjöström L, Kasstöm H, Källber M 1995 48. Wind A P 1993 Elbow dysplasia. In Slatter D anatomy and technique for arthrography of Ununited anconeal process in the dog. (ed.) Textbook of small animal surgery (2nd the cubital joint in clinically normal dogs. Pathogenesis and treatment by osteotomy edn). W B Saunders, Philadelphia: 1966– Journal of the American Veterinary Medical of the ulna. Veterinary and Comparative 1977 Association 203: 72–77 Orthopaedics and Traumatology 8: 170–176 49. Wind A P, Doval J 1994 Guide to radiographic 28. Meij B P, Hazewinkel H A 1995 Treatment 39. Snaps F, Balligand N, Saunders J, Park R, interpretation of the canine elbow joint. of canine elbow dysplasia. Proceedings of Daenen B, Dondelinger R F 1996 Compari- Institute for Genetic Control in Animals, the 7th International Elbow Working Group son of radiography and MRI for the diagno- University of California, Davis Meeting, Constance, Germany, 1 July 1995: sis of fragmented medial coronoid process 50. Wind P, Packard M E 1986 Elbow incongru- 18–21 of cubital joint in dog. Proceedings of the 4th ity and developmental elbow diseases in 29. Meutstege F J 1995 Aims of the international European Association of Diagnostic Imaging the dog: Part II. Journal of the American elbow working group. Proceedings of the 7th Conference, Cambridge, Great Britain, 29 Animal Hospital Association 22: 725–735 International Elbow Working Group Meeting, August – 1 September 1996 (Poster)

54 0038-2809 Tydskr.S.Afr.vet.Ver. (1998) 69(2): 43–54