hipscoring

Canine Hip Scoring

Dogs genetically predisposed to hip dysplasia are born with normal joints. However from about two months of age the hips of dysplastic dogs will subsequently undergo progressive structural changes. Either the socket (acetabulum) will become too shallow or the ligaments and/or muscles do not exert enough control to keep the femoral head from slipping away from the socket. The head of the femur loses its close contact with the acetabulum. The joint becomes unstable, causing stretching of the joint capsule and osteoarthritis. Due to the poor contact, the femeral head and acetabulum develop abnormally, creating a squared-off ball, and a shallow socket. This further increases the instability within the joint. Pain is caused by the stretching of the joint capsule and the inflamation of the osteoarthritis. As growth ceases at about 12 months of age, the joint capsule thickens and the muscles strengthen to stabilise the joint as the dog matures. From then on, the continued development of secondary osteoarthritis in the abnormal joint is slowely progressive and variable, affected by many factors.
source:The Hips-Hip Dysplasia and Hip Scores Ella Canham - Pet focus

The British Veterinary Association (BVA) and the Kennel Club (KC) developed a scheme in 1984 to assess the degree of hip malformation of dogs through radiography and since then over 100,000 X-rays have been assessed. An x-ray is taken of the hips, and is sent to be scored by an expert group of veterinary surgeons. They measure nine parameters in each hip, scoring each hip individually. The degree of hip dysplasia present is indicated by the sum of the points awarded for each of nine aspects of the X-rays of both hip joints. The minimum hip score is 0 and the maximum is 106 (53 for each hip). The lower the score the less the degree of hip dysplasia present. Both hips should be more or less symmetrical. An average (or mean) score is calculated for all breeds scored under the scheme and advice for breeders is to use only breeding stock with scores well below the breed mean score. Currently 97 breeds are surveyed by the scheme in the UK and the score is valid for the lifetime of the dog.

There are several established scoring systems to evaluate radiographs for the presence of hip dysplasia. (Dysplasia means abnormal development)

OFA http://www.offa.org
The Orthopedic Foundation for Animals evaluates a standard ventrodorsal view with hips extended and stifles rotated internally. Radiographs are scored based on degenerative joint changes and evidence of subluxation. Dogs must be 2 years of age at the time the x-rays are taken (preliminary radiographs can be done earlier, but the dog cannot be certified until two years of age even if the hips are deemed free of dysplasia) in order to be certified by the OFA.

To obtain the correct view for x-ray, the animal must be placed on its back in a dorsal recumbency with the rear limbs extended and parallel to each other. The knees (stifles) are rotated internally and the pelvis is symmetric. Sedation to the point of relaxation is recommended but is not a requirement. It is usually necessary for proper positioning.

The phenotypic evaluation of hips done by the Orthopedic Foundation for Animals falls into seven different categories. Those categories are normal (Excellent, Good, Fair), Borderline, and dysplastic (Mild, Moderate, Severe). Once each of the three radiologists classifies the hip into one of the 7 phenotypes above, the final hip grade is decided by a consensus of the 3 independent outside evaluations. Certificates are issued only to those dogs that are considered to be dysplastic-free with ratings of excellent, good or fair (a confidential consensus report is issued on dogs found to be dysplastic). Hip Grades

An OFA number is assigned to the dog and the OFA reports this number to the AKC and to the appropriate breed club. The OFA will only forward certification numbers on dogs that are permanently identifiable by either a tattoo or microchip. OFA is a closed type of registry, that is the AKC and breed clubs are notified of only non-dysplastic dogs and therefore, owners who suspect their dogs are dysplastic do not always forward their radiographs to the OFA. This limits the data-collection process.

PennHip http://www.pennhip.org/
The PennHip method uses a quantitative measure of joint laxity (based on distraction and compression views) to determine the Distraction Index (DI), as well as the standard hip-extended view, to evaluate a dog for hip dysplasia. The DI is a measure of passive hip laxity and is expressed as a number between 0 and 1. (A DI near 0 would indicate no joint laxity and very tight hips. A DI closer to 1 would indicate a high degree of laxity and very loose hips.) Dogs with DI scores less than 0.3 do not develop osteoarthritis, with increased incidence of osteoarthritis as the DI increased above 0.3. Across all breeds a DI of 0.5 gives a 50% chance of developing DJD.

The dog must be anesthetized while a series of three views are taken. The first is a traditional extended view (like OFA requires), the second is a compression view and the third is a distraction view taken with the aid of a distraction device. The veterinarian taking these radiographs must be PennHIP-certified. The three separate radiographs taken for evaluation will give an indication of the probability of a dog developing DJD/displasia/arthritis in later life. Dogs may be evaluated by this technique as young as 16 weeks of age. A PennHIP report is sent to both the owner of the dog and their veterinarian.

Anatomy Of Hip Joint		This Diagram Shows Scores of 0
	1. Cranial Acetabulem Edge (CrAE) 2. Cranial Effective Acetabulem Rim (CrEAR) 3. Dorsal Acetabular Edge (DAE) 4. Caudal Acetabulem Edge (CaAE) 5. Joint Space 6. Head of Femur (ball) (FH) 7. Neck of Femur 8. Acetabulem Fossa (AF) 9. Lesser Trochanter AN - Acetabular Notch FV - Foveal Drfect

From the x-ray taken at the owner's vets, the BVA scores each of the hip joints

The Norberg Angle (0-6)
This reading gives a measured assessment of several features; the degree of congruence between the femoral head (FH) and acetabulum; the length of the cranial acetabular edge (CrAE), which gives a relative indication of acetabular depth and a measure of coxofemoral subluxation (laxity).

Subluxation (0-6)
Subluxation (SL): is based principally on the degree of congruence between the femoral head and acetabulum. The general 'fit' of these two components is assessed by the relationship between the femoral head centre (FHC) and the underlying image of the dorsal acetabular edge (DAE). The cranial joint space is seen as a radiolucent shadow between the CrAE and adjacent cranial articular margin of the FH.

Score
0	the FHC must be medial to the DAE and the cranial joint space uniformly narrow, with the curve of the CrAE exactly following that of the FH.
1	mild divergence of the cranial joint space, either medially or laterally, with the FHC remaining medial to the DAE.
2	superimposition of the FHC on the DAE (with the FH in this position, the cranial joint space will inevitably diverge).
3	includes a wide range of femoral positions, with anything between less than one-half and more than one-quarter of the FH lying medial to the DAE.
4 & 5	are given for severe degrees of subluxation.
6	complete separation of the images of the two components.

Cranial Acetabular Edge (0-6)
Cranial acetabular edge (CrAE): minor alterations in the shape, contour and possibly the length of the CrAE are generally believed to be indicators of poor articular congruence, while more severe changes are clearly consequences of chronic instability, abnormal marginal wear and remodelling of the joint.

Score
0	the CrAE should be concave, uniformly curved and match exactly the contour of the adjacent femoral head with no lateral or medial divergence of the cranial joint space.
1	minor flattening of the outer quarter of the CrAE with slight divergence of lateral joint space.
2	the CrAE is flattened throughout most or all of its length and there is usually both medial and lateral joint space divergence.
3	higher scores are given when there is positive evidence of abnormal wear and/or remodelling of the edge. Early change is manifested by slight bilabiation, which shows as cranial curvature of a small outer segment of the CrAE.
4 & 5	are given to progressively more extensive bilabiation and cranial orientation of the edge.
6	development of a steep cranial slope.

Dorsal Acetabular Edge (0-6)
Dorsal acetabular edge (DAE): the DAE forms a well defined interface which traverses the FH almost vertically and extends a little beyond it cranially and caudally. The clarity with which it can be seen is highly variable, depending on radiographic technique.

Score
1	a minor change in the contour of the DAE, which is normally slightly curved but small localised irregularities, seen only on radiographs of exceptionally high quality, are considered to be within normal limits.
2	related to definitive pathological changes associated with degenerative joint disease (osteoarthritis), the smallest being minor exostosis, which is usually seen cranially.
3 & 6	progressively increasing new bone formation accompanied by marginal wear of the edge, which leads to reduction in width of the articular surface and thus contributes to subluxation according to severity.

Cranial Effective Acetabular Margin (CrEAM) (0-6)

Score
1	the earliest detectable abnormalities of the CrEAM are either minor exostosis, usually in the form of a small, well modelled osteophyte, or slight 'rounding off' of the junction between the CrAE and DAE, which may be seen in the presence of a non-bilabiated CrAE.
2	more advanced changes at the CrEAM are indicators of abnormal wear and must therefore be associated with articular instability. Initially, a small facet forms on the rim (margin), usually in conjunction with minor bilabiation of the CrAE. Exostosis may or may not be present.
3 to 6 (depending on severity)	increasing secondary changes lead to the development of larger facets and exostoses, which can become massive and extend well up the shaft of the ilium.

Acetabular Fossa (0-6)
Acetabular fossa (AF): it is well recognised that the acetabular fossa and notch are sites of bone proliferation in unstable hips, an impression of the amount of new bone present may be gained from the size and intensity of indistinctly marginated areas of increased opacity in the region of the caudomedial acetabulum and obliteration or partial obscuring of the normally clear radiolucent shadow which represents fat in the acetabular notch. Detectable bone deposition in the AF is almost always associated with marked subluxation and the amount tends to increase in proportion with the increase in the other radiographic hallmarks of secondary osteoarthritis. Objective numerical scoring of this criterion is difficult, but as changes are likely to be recorded only in dogs with a total score considerably higher than average, the importance of a high level of accuracy is diminished.

Caudal Acetabular Edge (CdAE) (0-5);
Caudal acetabular edge is the segment of the acetabulum which is subject to the widest range of normal radiographic variation. It is dependent to a large extent on the pelvis/film angle, but may also be influenced by individual differences in conformation. Radiographic abnormalities of the CdAEs are scored between 0 and 5 and changes are due mainly to exostosis, with signs of wear being apparent only in advanced cases.

Score
1	a small osteophyte on the CdAE.
2	new bone localised laterally and medially adjacent to the acetabular notch.
3 & 5	are used to record progressively increasing bone proliferation which ultimately fills the notch and produces extensive remodelling.

Femoral Head and Neck Exostosis (FH) (0-6)

Score
0	the normal FH should have a smooth roundish profile but the shape may vary considerably.
1	a well defined, vertically orientated ridge of new bone extending from the base of the neck towards the trochanteric fossa (Morgan and Stephens 1985). Correct exposure and good radiographic detail are required to show this earliest recordable change.
2	minor exostosis, visible on the 'skyline' at the lateral and/or medial margins
3	is given when a distinct collar of new bone is visible around the articular margin.
4 to 6	denotes increasing amounts of periarticular proliferation which at its most severe, extends to cover the femoral neck and fill the trochanteric fossa.

Femoral Head Recontouring (0-6)
This criterion is used to record the extent to which the FH shape is altered as a consequence of instability. Thus, scores are likely to be awarded only in cases in which secondary changes are well established, when remodelling occurs as a result of the combined effects of periarticular new bone formation and loss of subchondral bone (eburnation) following total destruction of articular cartilage. Recontouring is difficult to evaluate numerically however.

Score
1	slight distortion of the outline of the FH
2 to 5	degrees of flattening and expansion of the articular contour
6	permanent luxation in which the FH is grossly deformed, small and almost conical in shape.

A database of all scored dogs is kept to calculate the current average score for each breed. It is recommended that only animals with scores significantly below the breed mean score should be used for breeding. MAKE USE OF THESE REGISTRIES PRIOR TO BUYING OR BREEDING, FOR THE BETTERMENT OF THE BREED (afterall, isn't that what we are all striving toward??).

source
References: BVA/KC scoring scheme for control of hip dysplasia: interpretation of criteria; Christine Gibbs, BVSc, PhD, DVR, MRCVS
http://www.maremmano.com/chd.htm

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