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Hip Scoring

The British Veterinary Association (BVA) and The Kennel Club in the UK (TKC) have joined together to run a hip scoring scheme for breeders, in order to test for canine hip dysplasia, the most common inherited joint problem of large breed dogs. This current system came into effect in 1984.

Dogs are scored from the age of 12 months, and can only be scored once in their lifetime.

The BVA/TKC publish a list of Breed Mean Scores (BMS) for each breed, together with the number of dogs tested to date and the range of scores achieved. It is then recommended that breeders ensure their breeding stock have scores which are well below the BMS. The current BMS for Canaan Dogs in the UK is 15, a total of 16 dogs have been tested, the lowest score was 7 and highest 45.

From an x-ray taken at the owner's vets, the BVA scores each of the hip joints — the norberg angle (0-6); subluxation (0-6); cranial acetabular edge (0-6); dorsal acetabular edge (0-6); cranial effective acetabular rim (0-6); acetabular fossa (0-6); caudal acetabular edge (0-5); femoral head and neck exostosis (0-6); femoral head recontouring (0-6), thus each hip can receive a maximum score of 53 and overall score of 106. The lower the score the better, so 0/0 would be perfect, while 53/53 would mean that the dog had no hips at all!

 Diagram of hip joint Diagram shows scores of 0.
AF - Acetabular fossa
AN - Acetabular notch
FH - Femoral head
FV - Foveal defect
DAE - Dorsal Acetabular edge
CaAE - Caudal acetabular edge
CrAE - Cranial acetabular edge
CrEAR - Cranial effective acetabular rim

Norberg Angle
Measures two features — the degree of congruence between the FH and acetabulum and the length of the CrAE which gives a relative indication of acetabular depth.

Evaluation is based principally on the degree of congruence between the femoral had and acetabulum. The general 'fit' of these two components is assessed by the relationship between the FHC and the underlying image of the DAE; the configuration of the cranial joint space is also taken into account, particularly at the lower end of the scoring scale, when abnormalities are relatively minor. The cranial joint space is seen as a radiolucent shadow between the CrAE and adjacent cranial articular margin of the FH. For a zero score the FHC must be medial to the DAE and the cranial joint space uniformly narrow, with the curve of the CrAE eactly following that of the FH.

Cranial Acetabular Edge
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. For a score of zero the CrAE should be convex, uniformly curved and match exactly the countour of the adjacent femoral head with no lateral or medial divergence of the cranial joint space.

Dorsal Acetabular Edge
On good quality radiographs, the DAE forms a well-defined density interface which traverses the fH almost vertically and extends a little beyong it cranially and caudally. The clarity whith which it can be seen is highly variable. A minor change in the contour of the DAE, which is normall slightly curved, merits a score of 1, but small localised irregularities, seen only on radiographs of exceptionally high quality, are considered to be within normal limits. Higher scores are related to definitive pathological changes associated with degenerative joint disease (osteoarthritis), the smallest being minor exostosis, which is usually seen cranially.

Cranial Effective Acetabular Rim
The earliest detectable abnormalities of the CrEAR 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-biblabiated CrAE.

Acetabular Fossa
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 degennerative joit disease (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 han average, the importance of a high level of accuracy is diminished.

Caudal Acetabular Edge
The CaAE is the segment of the acetabulum which is subject to the widest range of normal radiographic variation. Radiographic abnormalities are scored between 0 and 5 and changes are due mainly to exostosis with signs of wear being apparent only in advanced cases.

Femoral Head and Neck Exostosis
The normal FH should have a smooth rounnnnndish profile, but the shape may vary considerably.

Recontouring of the Femoral Head
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 following total destruction of articular cartilage.

Scoring Criteria:

Score Norberg Angle Subluxation Cranial Acetabular Edge Dorsal Acetabular Edge Cranial Effective Acetabular Rim Acetabular Fossa Caudal Acetabular Edge Femoral Head/Neck Exostosis Femoral Head Recontouring
0 +15 & over Femoral head well centred in acetabulum Even curve, parallel to femoral head throughout DAE has slight curve Sharp, clear-cut junction of DAE & CrAE A fine bone line curves medial and caudal from caudal end of CrAE Clean line Smooth rounded profile Nil
1 +10 to +14 Femoral head centre lies medial to DAE. Lateral or medial joint space increases slightly. Lateral or medial 1/4 CrAE flat. Lateral or medial joint space diverges slightly Loss of S-curve only in the presence of other dysplastic change Indistinct junction of DAE and CrAE Slight increase in bone desnity medial to AF. 'Fine line' hazy or lost Small exostosis at lateral CaAE Slight exostosis in 'ring form' and/or dense vertical bony line adjacent to trchanteric fossa ('Morgan line') Femoral head does not fit in circle due to exostosis or bone loss
2 =5 to +9 Femoral head centre superimposed on DAE. Medial joint space increase obvious CrAE flat throughout most of its length Very small exostosis on cranial DAE Very small exostosis or very small facet Fine line lost in AF and ventral AE hazy due to new bone. Notch at CaAE clear Small exostosis at lateral and medial CaAE Slight exostosis visible on skyline and/or density on medial femoral head Some bone loss and/or femoral head/neck ring of exostosis
3 0 to +4 Femoral head centre just lateral to DAE. 1/2 femoral head within acetabulum CrAE shows slight bilabiation Obvious exostosis on DAE (especially cranially) and/or minor 'loss of edge' Facet and/or small exostosis and/or slight bilabiation Incomplete remodelling of acetabulum with medial face lateral to AF. Ventral AE lost. AF hazy. Notch irregular Large exostosis and narrow notch at CaAE Distinct exostosis in 'ring formation' Obvious loss and distinct exostosis giving slight conical appearance
4 -1 to -5 Femoral head centre clearly lateral to DAE 1/4 femoral head within acetabulum CrAE shows moderate bilabiation Exostosis well lateral to DAE and/or moderate 'loss of edge' Obvious facet and/or obvious exostosis and/or moderate bilabiation Marked exostosis and 'hooking' of lateral end of CaAE Obvious complete collar of exostosis Gross remodelling. Obvious bone loss and exostoosis gives mushroom appearance
5 -6 to -10 Femoral head centre well lateral to DAE. Femoral head just touches DAE CrAE shows gross bilabiation Marked exostosis all along DAE and/or gross 'loss of edge' Gross exostosis and/or facet and/or gross bilabiation Gross remodelling. Dense new bone throughout acetabulum. CaAE notch lost and AF obscurred Gross distortion due to mass of new bone in acetabulum. Notch lost completely Massive exostosis giving mushroom appearance Very gross remodelling with marked bone loss and much new bone
6 -11 and over Complete pathological dislocation Entire CrAE slopes cranially Massive exostosis from cranial to caudal DAE Complete remodelling of CrEAR. Massive exostosis and/or gross facet Complete remodelling and new articular surface, well lateral to AF. Notch lost Void Massive exostosis and infill of trochanteric fossa and below femoral head Femoral head imporperly shaped due to maldevelopment or femoral head centre

References: BVA/KC scoring scheme for control of hip dysplasia: interpretation of criteria; Christine Gibbs, BVSc, PhD, DVR, MRCVS

This page was updated on 10-Dec-2005

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