Perthes Disease, also called Legg-Calve-Perthes Disease, is when the head of the thigh bone
dies, collapses, and heals over several years.
It is often a painful and frustrating process.
The hip is made up of muscles, ligaments, and bones, which have a ball, your femur,
and a socket, your acetabulum.
The ball is contained within the socket by a strong set of ligaments, called the joint
capsule, and the labrum.
Together, the hip joint allows your leg to support your weight while in motion, and standing
still.
At birth, our bones are mostly made up of soft, flexible cartilage.
This cartilage acts as a temporary scaffolding which is slowly replaced by bone as we grow
into adulthood.
As they grow, the ball and socket work together to form a matching a pair of a close-fitting,
spherical joint.
Our bones need a steady supply of blood to live and grow, and the ball of the femur has
its own unique blood supply due to a special region called the growth plate.
In children, the growth plate makes this blood supply very fragile.
If part, or all of this blood supply somehow becomes lost, the ball starts to die.
This is stage 1 of Perthes disease.
The rest of the femur is not affected, since it has its own blood supply.
There are four stages of Perthes disease, which can vary greatly in length and severity.
The diagram to the left shows the femur within the socket, with the inner surface of the
socket highlighted.
The labrum can be seen as well, hugging the ball.
On the right is an x-ray view.
Remember that some parts of children's bones are still made up of cartilage, which doesn't
show up on x-rays.
This is why children's bones look so strange on x-rays.
Stage 1, Necrosis, can last 3 months to a year.
On an x-ray, the dying bone may look slightly more white.
The hip may become inflamed, stiff, and painful.
Stage 2, Fragmentation, can last 6 months to 2 years.
The body starts rebuilding the ball by clearing out the dead bone, and replacing it with new,
soft cartilage, which will be replaced by bone later on.
Different areas start regrowing at different times, however, making it look fragmented,
and irregular.
As the ball becomes fragile and soft, it starts to change shape under the weight of the body.
The hip remains inflamed, and some muscles become tight, preventing the hip from moving
smoothly.
Together, these changes may make the ball move, or escape, out of the socket over time.
Pain is generally worse, and can spread to the thigh or knee.
Children often limp and tend to guard their hip, especially after being active.
In some cases, they may be unable to bear weight.
Stage 3, Re-ossification, can last 1 to 3 years.
Blood flow starts to become restored to the ball, and new bone starts replacing the soft
cartilage.
This new bone is also soft, and is easily reshaped.
In this stage, pain typically starts to decrease.
In Stage 4, Remodeling, the ball continues to be shaped until the child stops growing,
as the ball hardens.
Often, it appears more oval shaped, and the socket may become shallow as well.
Typically, the final shape of the joint, and the amount of hip motion, determines the long-term
outlook of the child.
We don’t know what causes Perthes disease.
It occurs more often in boys, and affects about 4 in 100,000.
Exams usually include an x-ray, and may include a perfusion MRI, to evaluate blood flow.
Since Perthes is so complex, treatment must be tailored to each child, with regular checkups
until they stop growing.
Every treatment we offer follows the “Principle of Containment,” which aims to keep the
ball contained within the socket, and maintain the hip's range of motion as much as possible,
so that as the ball heals, it is molded into a matching pair with the socket.
As the disease progresses, however, the ball changes shape, which can lead to the ball
escaping from the socket.
This is called a “loss of containment,” which complicates the disease.
The change in shape, increased inflammation, poor hip motion, and tight muscles all contribute
to the loss of containment.
In an attempt to prevent this, there is a robust set of non-surgical, and surgical options.
Non-surgical treatment aims to maintain hip motion, and minimize pain.
This includes physical therapy, bracing, casting, anti-inflammatory medicines, or in some cases,
restricting key activities.
Surgery may be necessary in some cases.
Surgery can be done on the femur, or can be done on the pelvis, or on a key tendon to
help improve motion.
Injections can also be used to relax tight muscles or reduce inflammation.
Regardless of treatment, the effects of Perthes may have long-term implications.
Our team will work with you to achieve the best outcome for your child’s hip and minimize
their pain.
To learn more, contact the Orthopedics Institute at Children’s Hospital Colorado by calling
us, or visit the website by clicking the links below.