The earliest that an official BVA/KC hip x-ray can be taken is one
year of age but a number of owners like to have an idea of the hip
status of their pup at an earlier age. The reasons are possibly
concern over movement, selection for retention of future breeding
stock, or just plain curiosity.
Early screening x-rays are taken from six months of age but often
the official results at one year appear worse than the screening
ones and this is due to the fact that the early hips are maturing
and remodelling. Also the labrum or cartilaginous lip of the
acetabulum has not, at that age, become bony making the true
dimensions impossible to determine on the x-ray.
All of the different hip schemes around the world exist to determine
the probability of a dog developing hip osteoarthritis at a later
age and so to advise on the suitability of that dog for breeding.
Osteoarthritis is the painful sequel to hip dysplasia and is always
progressive. Dysplasia means misshapen. It has been scientifically
proven that none of the schemes that rely on a hip extended view can
predict the probability of developing osteoarthritis. The BVA/KC and
the German SV schemes rely on the hip extended view.
The measurement of hip joint looseness or laxity has been proven to
be a measurable objective component that does predict the
probability of developing osteoarthritis and this is the basis of
the PennHIP scheme founded at the University of Pennsylvania and now
operating in many countries. However this scheme relies on the
manual positioning of the limbs for the x-ray and this raises
serious health and safety issues in the UK.
Additional faults with the BVA/KC scheme are many. In the hip
extended position the hips are actually tightened and this has the
effect of reducing the observed laxity by up to 50%. The breed mean
score published, that has decreased little over the decades, is
totally meaningless as many x-rays of poor hips are just not
submitted. With the PennHIP scheme failure to submit, results in the
operator loosing his certification making that breed mean score
accurate.
The one good point about the BVA/KC scheme is that the
identification of poor hips is accurate. But because laxity is not
measured, about 50% of the so called good hips will go on to develop
osteoarthritis and these dogs should be excluded from breeding.
In fact in my opinion, any dog that already has radiographic
signs of osteoarthritis at screening should not be used for
breeding.
Hands free or non-manual positioning is now available in the UK and
it is possible to measure hip laxity legally. The degree of laxity
is called the distraction index (DI) and it ranges from about 0.3 to
1. A DI of 0.3 is considered normal and it means that there is 30%
less coverage of the femoral head when the hips are distracted. It
also means that it is most unlikely that the dog will develop
osteoarthritis, where as a dog with a DI of 0.8 may have a 90%
chance of developing osteoarthritis by three years of age.
Distraction radiography can be done from 16 weeks of age with
accurate results and, according to PennHIP, breeding is recommended
only from dogs with a lower DI (tighter hips) than the breed mean.
Obviously selecting tight hips in both dam and sire will result in
better hips in the offspring. The current breed mean distraction
index for German shepherd dogs is 0.45.
Very early determination of the distraction index will also identify
the dogs that might benefit from juvenile pubic symphysiodesis (JPS)
surgery that increases femoral head coverage. The window for this
procedure is 14 to 18 weeks of age. Perhaps this may be the subject
of an article in the future!
Distraction radiography is available at Nantwich Veterinary Hospital
with the fee being the same as an ordinary hip film. This costing
includes the calculation of the DI and its interpretation. JPS
surgery is also a procedure offered.
:
+44 (0)1905 830900
