Small Animal Clinic, Department of Veterinary Clinical Sciences, Giessen, Germany
Learning Objectives
The diagnosis of canine elbow dysplasia (ED) in screening programs is based on the evaluation of radiographs according to the protocol of the International Elbow Working Group (IEWG). The most recent update of this protocol is available on the IEWG web site (http://www.vet-iewg.org). A mediolateral flexed projection of each elbow joint is mandatory for interpretation and an additional craniocaudal pronated view is highly recommended. The IEWG protocol allows for both registration of arthrosis and the presence of the major forms of primary lesions: FCP, OCD, UAP, incongruity. Radiographs are evaluated in a two-tiered procedure: joints are evaluated and graded according to the presence of arthritic changes first and assessed for signs of a primary lesion in a second step. Any other abnormal finding should be reported too.
Arthrosis scores are assigned as normal (Grade 0) in the absence of arthritic lesions or according to the height of osteophytes as either mild (Grade 1, osteophytes less than 2 mm in height), moderate (Grade 2, osteophytes 2–5 mm) or severe (Grade 3, osteophytes higher than 5 mm). In the updated protocol the severity of joint incongruity has been included.
The primary lesions fragmented medial coronoid process (FCP), osteochondritis dissecans (OCD), ununited anconeal process (UAP), incongruity have been defined by the IEWG (for details see the table below and IEWG website).
Scoring (Last Updated 2010)
The elbow findings are scored according to the severity of the arthrosis (DJD) and/or the presence of a primary lesion.
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Elbow dysplasia scoring
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Radiographic findings
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0
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Normal elbow joint
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Normal elbow joint
No evidence of incongruity, sclerosis or arthrosis
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1
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Mild arthrosis or suspect primary lesion
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Presence of osteophytes < 2 mm
Sclerosis of the base of the coronoid processes - trabecular pattern still visible
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2
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Moderate arthrosis
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Presence of osteophytes 2–5 mm
Obvious sclerosis (no trabecular pattern) of the base of the coronoid processes
Step of 3–5 mm between radius and ulna (incongruity)
Indirect signs for other primary lesion (UAP, FCP/coronoid disease, OCD)
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3
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Severe arthrosis or evident primary lesion
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Presence of osteophytes > 5 mm
Step of > 5 mm between radius and ulna (obvious incongruity)
Obvious presence of a primary lesion (UAP, FCP, OCD)
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A borderline (BL) score between ED 0 and ED 1 is allotted to dogs with minimal anconeal process modelling of undetermined aetiology in some countries (i.e., Germany, France, Italy).
ED scoring based on the combination of arthritic changes and presence of primary lesions is used non-uniformly throughout Europe and overseas. In Scandinavia, UK and USA/Canada for example classification is based on the degree of arthrosis mainly, whereas the UAP is the only primary lesion recorded.
Radiographic Views
The minimal requirement for elbow joint scoring is a true ML projection of each elbow.
As has been reported before two ML-projections, a flexed (30°–40°) and a neutral (100°–120°) position provide the best information regarding the medial coronoid process, incongruity, and presence of osteophytes. With high image quality even OC lesions may be recognized on ML views with reasonable consistency. With modest image quality many OC lesions go undetected on ML views. The by far best view to highlight medial trochlear OC lesions is the Cr Cd 15° pronated projection. Protocols lacking this view - as conducted in many European countries - approve the flaw of missing potential OC lesions depending on image quality.
Conclusion
The IEWG scoring system is a two-tiered procedure, a) assessing the degree of arthrosis and b) registering any signs indicative of a primary lesion of ED. Bear in mind that various countries in Europe and overseas only rely on step a. Both concepts have proven to be useful in reducing ED in a population. However, problems arise when dogs are to be used for breeding in countries with differing scoring system. In such a case it is advised to re-score the dog again according to the local scoring mode. It will be the aim of IEWG to harmonize the scoring systems in the future.