My book, Save Your Hips, does talk about dysplasia, a concept first put forth in 1939 by Gunnar Wiberg. By this time, radiology was well established and the practice of orthopedics focused primarily on bones. Throughout the previous century a deep level of understanding had been centered on imbalances in the soft tissues surrounding the joint as the initial, fundamental pathology in common hip disease.
I believe The Problem of Wiberg (I just coined this phrase) to be the tipping point in changing current understanding of chronic hip disease.
Center Edge Angle of Wiberg
Wiberg saw on AP radiograph that some acetabulae provide less coverage to the femoral head than others. Working with impressive 2D images that were easy to manipulate mathematically, he produced a theory stating that at a certain point in his diagnostic parameter, called the center edge angle of Wiberg (CEA), a hip could be considered dysplastic or not.
The CEA contains a large margin of error, however, because it does not take into account the major musculoskeletal movement that positions the acetabular roof over the femoral head which is, of course, sacral nutation (i.e. lordosis). When we lie supine for a standard AP radiograph, the femoral head moves slightly up and out of its socket. When we stand up, the femoral head moves down and medially. The hip joint follows the sacrum in this movement. Therefore, none of the images Wiberg was working with gave a true representation of how much of the weight-bearing joint was actually covered by the acetabular roof. No doubt he saw some very abnormal joints. But his parameter is largely erroneous because it measures spacial relationships in a non-weight-bearing position. This wouldn’t be a problem if the joint didn’t radically change from supine to standing…but it does! Wiberg and all the diagnosticians after him never really knew from an AP radiograph which hips were going to be covered-enough as the lumbar spine extended with standing. There are other imaging technologies today, but no one has wanted to confront The Problem of Wiberg. Therefore the images are digitally manipulated to give a standard AP view of the pelvis (“anterior pelvic plane”).
Crazy, but true. This is what Save Your Hips is all about.
But what were Wiberg and others through the century seeing in a dysplastic acetabulum? That it is “shallow” and “oval-shaped”, instead of more circular (it is actually a spiral, which my daughter, who is also my artist, and I realized at the same moment).
The only possible gravitational dynamic capable of creating such an acetabular shape is bearing the center of mass on the front aspect of the joint. One bears the COM in this way by flattening lumbar curvature while weight-bearing. The degree to which the lumbar spine is flattened from its natural, wide-radius curvature, is the same degree the femoral head is moved up and laterally.
It is also true that there is another, far less common, condition where the femoral head has been held slightly out of the joint from birth or early childhood. Thus, we have a true developmental dysplasia, and also an acquired (degenerate) condition. Spinal and/or pelvic obliquity (scoliosis) can also cause the hip joint to twist and elongate.
So how should a thirty or forty-year-old who has new-onset or slowly progressing hip pain with radiologic signs of dysplasia be categorized? You would not be able to determine (other than by history) which hip dysplasia was acquired and which was developmental. The trained eye, however, would be able to tell by subtle differences in the bones themselves. But this distinction is not studied and therefore not mentioned in orthopedic literature. It is all classified as developmental.
Acquired dysplasia causes the anterior aspect of the symmetrical, arched acetabular roof to (1) stretch – as gravity pulls the joint downward, elongating the acetabulum like taffy, and (2) apply bone to what becomes the anterior-superior aspect of the acetabulum in the counternutated position (lumbar curve flattened). This area becomes thickened and protruding as it tries to cover and protect the joint.
The process of stretching and bone deposition at the anterior-superior aspect of the joint is probably largely responsible for other popular orthopedic theories, acetabular retroversion and pincer FAI, which describe the same architectural characteristics. This is why I describe in my book how orthopedics creates new diseases out of thin air.
To convolute matters further, the practice of orthopedics believes this dysplastic area to be the weight-bearing roof of the normal acetabulum, due to a 500 year-old misconception of pelvic orientation in the bipedal position.
Orthopedics has used flawed, circular logic to justify the mutilation of millions of hips.
Which kind of dysplasia do you believe you have, Cara?