Charles T. Price M.D. - The Parents Guide to Perthes

Perthes disease, also called Legg-Calv-Perthes disease, is a condition in which the bone in the ball in a childs hip joint loses its circulation and becomes brittle. Over time, this causes the bone to die, but as circulation returns to the joint, new bone gradually grows in place of the brittle bone. For some children, this process affects the shape of the ball at the top of the thigh bone, which is called the femoral head. This can occur in one hip or both hips.

This stoppage of circulation in the hip can occur at any age, but the problem has different names for other age groups. A name that applies to any age group is avascular necrosis (AVN). Avascular means the loss of vascularity (blood flow) and necrosis means death. So, the term AVN means death of the bone because of loss of blood supply. However, doctors use a lot of different terms for this condition. You dont need to remember all of the names that are used for Perthes. They are explained here and are also in the glossary for reference. Perthes disease is the most common name, but you may hear Legg-Calv-Perthes disease, or simply AVN because AVN is the medical term for what happened. In fact, AVN can occur in babies and in adults, but its only called Perthes in the age group between 2 and 14 years. To make matters more confusing, AVN in babies and adults is also called osteonecrosis, or dead bone, in addition to being called AVN. So, you can see that doctors use many terms to identify one problem. This is similar to the way we identify ourselves by our names, full names, nicknames, family relationships, or other terms.

One possible reason that the term Perthes is used for the age group between 4 and 13 is how Perthes affects the shape of the ball at the top of the thigh bone. Babies with AVN always recover with a round ball, but adults never do without treatment. The age between 4 and 13 is unpredictable. Some children in this age group recover without any intervention and others need treatment. So, the first question to ask is: who needs treatment and who doesnt in the age group between 4 and 13 years? Doctors rely on observations, tests, and experience to help decide who needs to be treated and who can be allowed to heal without intervention. We hope that this book will give you some insight into the keys for those decisions.

A hip joint is a ball-and-socket joint. The top of the thighbone (femur) is round, like a ball, and is called the femoral head. It fits deep inside the hip socket, which is called the acetabulum.

Cartilage covers the surfaces of the joint, and allows it to glide smoothly. Oily fluid inside the joint keeps it lubricated. That fluid is made by the lining of the joint called the synovium. A rim of soft tissue called the labrum surrounds the hip socket: it adds extra support and provides a seal that helps keep the ball inside the socket. Because it is not made of bone, the labrum cannot be seen on x-rays.

In , notice that the blood vessels do not cross the growth plate because it is cartilage in the child. This limits the blood supply to the ball until the growth plate turns to bone as an adult. Sometimes Perthes causes the growth plate to turn to bone prematurely and this can cause a growth disturbance.