Grading Primary Elbow Dysplasia Lesions and Elbow Osteoarthrosis According to the IEWG Protocol
B. Tellhelm; Kerstin Amort; Nele Ondreka
Department of Small Animal Clinics, Section of Surgery, University of Giessen, Germany
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 website (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 registers signs of arthrosis and the presence of the major forms of primary lesions (FCP, OCD, UAP, incongruity). The films are evaluated in a two-stage process: a) to assess the degree of secondary joint disease (arthrosis) and b) to check for signs of a primary lesion.
Any other abnormal finding should also be reported.
The status of the elbow joint regarding arthrosis is scored as either "normal" (grade 0), mild (grade 1, osteophytes less than 2 mm high anywhere in the joint), moderate (grade 2, osteophytes 2–5 mm high) and severe (grade 3, osteophytes higher than 5 mm). In the updated protocol the severity of joint incongruity has been included.
The primary lesions have been defined by the IEWG (for details see the IEWG website).
Scoring (Updated 2010)
The elbow findings are scored according to the severity of the arthrosis (DJD) and/or the presence of a primary lesion
Elbow dysplasia scoring
Normal elbow joint
Normal elbow joint
No evidence of incongruency, sclerosis or arthrosis
Presence of osteophytes < 2 mm high, sclerosis of the base of the coronoid processes - trabecular pattern still visible
Moderate arthrosis or suspect primary lesion
Presence of osteophytes of 2–5 mm high
Obvious sclerosis (no trabecular pattern) of the base of the coronoid processes
Step of 3–5 mm between radius and ulna (INC)
Indirect signs for a primary lesion (UAP, FCP/ Coronoid disease, OCD)
Severe arthrosis or evident primary lesion
Presence of osteophytes of > 5 mm high
Step of > 5 mm between radius and ulna (obvious INC)
Obvious presence of a primary lesion (UAP, FCP, OCD)
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 (e.g., Germany, France, Italy).
How Many Projections?
The minimal requirement is a true ML projection of each elbow. Excessive pronation or supination should be avoided. In a maximally flexed position (as it is the standard view in many countries) the elbow is often markedly supinated, making correct interpretation of shape and structure of MCP, sclerosis caudal to MCP and spur formation cranially difficult.
An OC defect may easily be missed on the ML projection, but can usually be identified on a CrCd 15° pronated view. As scrutineers in many European countries (e.g., Scandinavia, UK) ask only for a maximally flexed ML view or two ML views with different flexion of the elbows respectively, an OC lesion may not be recognized.
For many years a Cr15L-CdMO pronated view was considered mandatory for the diagnosis of FCP. However, recent results of CT examinations and arthroscopy indicate that radiological findings typical for the presence of FCP can be identified on the ML view quite consistently. The ML projection may therefore be sufficient to diagnose or suspect the presence of a FCP reliably in a screening program. As reported before, two ML-projections - flexed (30–40°) and neutral (100–120°) position give the best information concerning shape and structure of MCP and is also diagnostic for incongruity and osteophytes. On radiographs of good quality, even many OC lesions are visible on the flexed ML.
The main problem from my point of view is not the number of radiographs but the intention of the expert to register all findings which can be detected even on one ML view if it is of good quality and the elbow positioned correctly.
How to Score Elbow Dysplasia?
Elbow dysplasia scoring on the basis of a combination of the severity of arthrosis (DJD) and radiographic findings indicative for a primary lesion or evidence of a primary lesion is not uniformly used in Europe and overseas. The Scandinavian countries for example started scoring in the early 80s prior to the foundation of IEWG. Their classification is based on the degree of arthrosis, while of the primary lesions only UAP is recorded. This scoring system is used in Scandinavia and also in the UK and USA/Canada.
The most common primary elbow lesion is a FCP. Pertinent radiological findings on the ML projection are a blurred and deformed cranial edge of the medial coronoid process (MCP), a reduced opacity of its tip, an increased opacity of the ulnar notch at the level of the coronoid processes, and an increased and/or incongruent joint space between humerus and radius. It is important to recognize that even minimal changes are usually pathognomonic for FCP qualifying an elbow for at least an ED grade 2 (moderate ED, coronoid disease/FCP indicated) according to the current IEWG protocol regardless of the height of osteophytic new bone formation. The severity of new bone formation is quite variable and some dogs may not show any new bone formation at all. If grading is based on the size of the osteophytes only, many elbows with FCP will be underscored and may even be considered free of ED.
Beware of Conflicting Data
As mentioned above, the IEWG scoring system is a two-step procedure: a) assessing the degree of arthrosis and b) registering any signs indicative of a primary form 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.
Slice Imaging and Appeal Procedure
Diagnosing FCP radiographically may be based on subtle findings which may be difficult to convey to the dog owner. As a consequence, an increasing number of appeals are filed and owners ask for a CT study to be included in the reevaluation process. No standardized protocol for CT examination of the canine elbow have been proposed. IEWG plans to install a standardised protocol for appeal procedures, the use of CT and/or MRI examinations, and the technical requirements of such studies.