(human hip similar to a dogs' hip)
When Penn hip was developed in the late 1980's, I found the concept very intriguing. The thought of having a tool that could prognosticate a four month old puppy hip for potential adult breeding consideration, was exciting. As most know, OFA certification is only given to dogs two years and older.
The Penn Hip measure the joint laxity between the femoral head and the acetabulum (hip socket). The theory of Penn Hip is the degree of laxity found at four months of age will not change as the dog gets older. So, a dog that tests normal at four months, will or should in theory be normal at two years of age. This is not the case with a standard wedge radiograph that is used for OFA. That is why the two year limit for OFA was set. Many dogs that would pass a preliminary OFA evaluation at one year, fail at two years.
As a former Airedale breeder, who by the way have serious problems with Hip Dysplasia, this was very promising until, I witnessed a Penn Hip radiograph performed on a three year old male Airedale. I found thiss very disturbing and I would never subject a dog of mine, let along a four month old puppy to this procedure.
The dog while under anesthetic is placed on their back with their rear legs pointing up. A devise of some sort is placed or wedged in the groin and pushed down along the inner thigh to drive the hips out of their sockets. At the point of maximum force on the the hip, the X ray is taken. After the X ray dries, two concentric circles are drawn on the film itself, one around the femoral head and another in the hip socket. The two circles will intersect (unless the dog is very badly dysplastic), it is that area that is measured for joint laxity.
After witnessing this procedure, I always said I would never subject a STILL DEVELOPING puppies hips to
those forces. Who would know how much damage was being done at the time of the test? I will stick with breeding OFA clear animals, and hope for the best.