What is Perthes Disease?
Perthes disease (also called Legg-Calve-Perthes disease) is a condition where there is damage to the hip joint due to lack of blood supply to the femoral head in children (ball of the hip joint). Damage due to a lack of blood supply causes death of the bone. Avascular necrosis (Avascular: Lack of blood supply, Necrosis: Death of tissue/ bone). The cause of Perthes disease remains unknown. Perthes disease is more accurately called “Idiopathic avascular necrosis of the femoral head” in a child (Idiopathic: Having no known cause).
What causes Perthes Disease?
As mentioned previously, the exact cause remains unknown. There are various theories about the possible cause(s) of Perthes disease. In spite of numerous studies conducted in different parts of the world, no single cause has emerged. Some of the studies have pointed to certain associations/ risk factors that are listed below.
- Small hyperactive children
- Conditions that cause thickening of the blood, typically genetic conditions where certain proteins involved in the blood clotting mechanism do not function properly
- Collection of fluid within the hip joint which constricts the blood supply to the femoral head
- Changes to the blood supply of the femoral head
- Socio-economic deprivation was also cited as a possible cause of Perthes disease, though the exact mechanism is unclear.
In most cases, however, there is no treatable cause. The condition needs treatment but it is not a condition that can be cured either through medication or surgery.
What are the symptoms of Perthes?
This condition occurs only in childhood. Avascular necrosis of the hip (AVN) in adults behaves very differently to Perthes and the 2 conditions are not comparable. The management of adult AVN is also entirely different to that of Perthes disease.
Perthes typically affects children between the ages of 4 and 8 years, though it can occur at any age. Boys are more commonly affected than girls.
The condition starts as unexplained pain in one or both hips. The pain can be quite mild and tolerable to start with but over a matter of weeks to months, becomes severe and restricts activities. The child starts limping and is unable to walk distances or play sports in school. The affected leg can be shorter than the normal side and this exaggerates the limp.
The child will otherwise be well with no lever, loss of weight or appetite (called "constitutional symptoms"). If such symptoms are present along with hip pain, the cause is likely to be some other condition such as infection in the hip or Juvenile Inflammatory arthritis.
How does Perthes disease progress over time?
Perthes disease naturally progresses through 4 stages namely
- Sclerosis: the femoral head (ball of the hip joint) looks compacted on the x-ray, this stage represents
- Fragmentation: the ball starts to break up and collapse. It appears flattened compared to the normal side
- Re-ossification: The fragmented ball reforms back to a more normal looking bone shape and structure
- Re-modelling or healing: If the hip has deformed significantly during the collapse stage, the natural processes of growth and healing attempt to make the femoral head more normal spherical, though this process does not always occur reliably or result in a completely normal femoral head.
The above process occurs in every child with Perthes disease. It can take 3 – 5 years for the process to complete and no treatment to date has succeeded in shortening the course or duration of the condition.
During the stage of collapse and fragmentation, there can be significant pain and muscle spasm. This along with the change in the shape of the ball causes it to gradually come out of the socket. As the ball edges out of the socket, it is at risk of being dented and deformed further.
The mainstay of treatment is therefore to keep the vulnerable ball of the hip joint within the socket whilst the condition runs its course. This is called CONTAINMENT. This is important because once the ball becomes dented, it is difficult to "un-dent" it.
A good result from treatment of Perthes disease will therefore result in a ball that matches well with the socket. This is called "congruity" of the hip joint. It also helps to have a femoral head that is as spherical as possible, though not as critical as congruity.
Long term studies clearly show that congruity determines whether early arthritis occurs in the hip joint.
How is Perthes diagnosed?
Clinical examination of the child is very important to assess the range of movement present within the hip joint, whether there is any contracture and to assess the difference in length between the legs. The findings on clinical examination also help to decide whether surgery is needed or not. The diagnosis of established Perthes disease is not difficult. A plain x-ray of the hip will show the classical changes of Perthes disease.
Early in the course of the illness, hip pain may be present but the x-ray may appear normal. In such cases, an MR scan of the hip can show the lack of blood supply to the femoral head.
Some centres use a test called an Isotope bone scan but this test has largely gone out of favour either to diagnose Perthes or to determine the severity of the condition.
An arthrogram (dye test to visualise the hip joint) is sometimes useful in determining the need for surgery and the exact type of surgery that is likely to help. Because the hip joint is deep and not easily felt through the skin, a short general anaesthetic is required so that the child will lie still during the procedure. The anaesthetic also relaxes any tight muscles and allows the surgeon to determine the true range of movement in the hip joint.
What are the treatment options?
The treatment options for children with Perthes disease has evolved over time. The guiding principle is CONTAINMENT of the affected hip (keeping the ball inside the socket). Because the socket of the hip joint is not affected by Perthes, it retains its spherical shape for much of the active phase of the disease. The spherical socket is therefore used as a "mould" to guide remodelling of the softened femoral head whilst Perthes runs its course. If the head remains within the spherical socket, it is more likely to regain a spherical shape.
In 2004, the results of a large multi-centre study comparing different types of treatment for Perthes was published. Whilst there are shortcomings in the study, some important facts came to light.
- Children younger than 6 years at the time of onset of condition do better
- Boys do slightly better than girls (probably because girls of comparable age are biologically more mature than boys
- Children older than 8 years at onset did poorly in spite of treatment (though only femoral and pelvic osteotomies were included in this study, in particular the utility of the Shelf procedure was not evaluated – see below)
- Hip abduction braces were found to be of NO benefit
- Surgery helped children older than 6 years at onset who had a more severe grade of Perthes
There are several other studies that have helped us understand and treat Perthes better. For instance, the treatment of children older than 8 years has changed and newer treatment approaches have shown early promising results. Suffice to say that a thorough understanding of the latest literature is essential in managing Perthes in an evidence-based manner.
- Brace treatment:
- Brace treatment involves placing 1 or both legs in a caliper from hip to foot. Children find it difficult to stand or walk with the brace. The child’s education is likely to be affected. In any case, braces have shown to be ineffective. There is the potential for long-term psychological damage to the child due to lack of proper interaction with peers.
For these reasons, long-term treatment in hip abduction braces has NO role in the modern management of Perthes disease.
- Maintaining range of motion in the affected hip is a critical aspect of managing Perthes in the early stages. A specific set of exercises to strengthen the muscles that abduct (pull the leg away from the body) the hip is useful. A period of light skin traction at home also helps to overcome muscle spasm and relieve pain. Hydrotherapy and gait training are also useful adjuncts to regular land-based exercises.
The exercises have to performed at home but supervised by a physiotherapist. The overall management should be overseen by a paediatric orthopaedic surgeon and regular assessments are required to ensure that physiotherapy is achieving the intended goals. If a child does not appear to be making sufficient progress with physiotherapy, an early referral back to the orthopaedic team and further x-rays is advisable.
- In spite of regular physiotherapy, surgery to contain the femoral head within the socket is required in many children with Perthes disease. In 1 study, early surgery shortened the course of the condition and the femoral head did not fragment (break up). Surgery should be performed when the hip becomes increasingly stiff and before the femoral head fragments. This approach is associated with the best results.
There are at least 4 surgical procedures that are commonly used in the treatment of Perthes disease including
- Varus femoral osteotomy: useful in children under 8 years for containment
- Pelvic osteotomy: children under 8 years of age for containment
- Shelf procedure: useful in children over the age of 8 years for containment and to assist in obtaining a congruent hip joint
- Valgus femoral osteotomy: useful as a salvage procedure in older children and young adults with previous history of Perthes disease and a deformed femoral head
In children under the age of 8 years, containment can be achieved by either a varus femoral osteotomy (surgery on the thigh bone/ femur to tilt the ball back towards the socket) or a pelvic osteotomy (surgery to tilt the socket towards the ball). Both are associated with similar results.
In this author’s experience, a femoral osteotomy is preferable for the following reasons:
- Femoral osteotomy is a lesser procedure with fewer complications, shorter hospital stay and less pain
- It makes sense to operate on the femur which is the affected bone in Perthes, rather than operate on a normal pelvic bone
- Children recover quicker from a femoral osteotomy
- Femoral osteotomy is a 2-dimensional procedure and less likely to cause any unwanted anatomical distortions compared to a 3-dimensional pelvic osteotomy.
This operation is very useful in older children with Perthes disease.
- In younger children, the femoral osteotomy is a good option because it contains the vulnerable femoral head well but the adverse effects of the operation are corrected with growth. This process is called remodelling of the bone.
- A femoral osteotomy is unsuitable in older children because the procedure could result in a permanent alteration in the anatomy of the bone. There is not enough growth left in older children for the remodelling process to occur fully.
So, what is a Shelf procedure? This operation essentially creates an additional roof over the femoral head, not dissimilar to an awning. The child’s own bone is taken from the pelvis and used to create the additional roof.
The pelvis is essentially 2 flat plates of bone with spongy bone in the middle (a bit like a jam sandwich!). Therefore one of the plates (one slice of bread from the sandwich, to stretch the analogy) can be harvested and used without any adverse effects. The flat plate of bone is cut to shape, a slot is created above the hip socket (acetabulum) and the flat plate is inserted into the socket.
There are many ways of doing the Shelf procedure. We use a particular type called the Tectoplasty (first devised by a Japanese surgeon). It produces reliable coverage of the femoral head and good containment.
When the collapsed femoral head heals in young children, it may end up in an ovoid shape. However, since these children have excellent remodelling the socket (acetabulum) also takes up an ovoid shape over time. The head matches up with the socket and we have a good result.
In older children however, the acetabular remodelling does not occur so reliably.
The Shelf procedure converts the spherical acetabulum into a larger ovoid shape that will match up quite well with the ovoid femoral head. If Perthes disease starts after the age of 8 years, it is unlikely that a perfectly spherical femoral head can be obtained at the end of treatment.
So, the Shelf procedure ends up making the best of a relatively bad situation. The Shelf procedure is sometimes called a "salvage procedure". Such salvage operations are typically done when there are irreversible changes and it is not possible to reconstruct normal anatomy. But, studies indicate that when a Shelf procedure is carried out at an early stage even before the head collapses, the end result in relatively good and a congruent hip joint can be obtained.
Valgus femoral osteotomy: This procedure is typically used in teenagers who had Perthes disease a few years previously. The disease has run its course and the femoral head has healed but with some deformation. In cases where the femoral head is aspherical or flattened but the socket is spherical, a valgus femoral osteotomy brings a relatively spherical portion of the ball back into contact with the acetabulum. Thus, it can make an incongruent hip joint into a congruent joint. As we have learnt previously, this reduces the risk of premature arthritis in the hip. The valgus osteotomy also increases the length of the affected femur (a positive side-effect of the procedure in Perthes disease where the affected leg is typically short). The valgus osteotomy also improves the mechanics of the hip joint by increasing the mechanical advantage of the hip abductor muscles. These muscles are important in maintaining the pelvis in a stable position during walking. Thus, a valgus osteotomy can produce significant improvements in the right situation. Patient selection is critical.
Valgus femoral osteotomy is generally technically more challenging than the more common varus femoral osteotomy. The recovery is longer as these are older individuals and the complication rates are higher.
There are a host of "newer" operations that are being tried in Perthes disease. Whilst many of these operations such as application of an external fixator across the hip joint have shown promising early results and/or have a sound scientific basis, no long term results are available. This is mostly because these operations have not been around for long enough.
One has to treat these procedures as "experimental" and approach decision making with suitable caution. Problems associated with such complex procedures do not emerge until we have long-term follow-up of operated cases. To quote an oft repeated phrase: "Nothing ruins a good result like long-term follow-up". A poor result from such complicated surgeries can leave the child in a worse situation than pre-operatively.
What we do for children with Perthes at SPARSH Hospital?
The approach at SPARSH is straight forward and evidence based. We do not perform any experimental surgeries, instead relying on time tested operations that are known to be effective.
- The basis for all treatment is CONTAINMENT
- We do not use any braces in Perthes disease because these have been shown to be entirely ineffective
- Regular clinical examination with x-rays helps to identify those children at risk of a poor result
- Regular physiotherapy programme is continued
- The child is allowed to walk, run and play within the limits of pain. Painkillers and anti-inflammatory tablets/ syrups can be used.
- If the head is "at-risk", we perform a varus femoral osteotomy in children under the age of 8 years.
- In older children, a shelf procedure is recommended
- When the active phase of Perthes has completed, options such as a valgus osteotomy are appropriate in selected cases
Who is at risk of Perthes disease? How can it be prevented?
There is no way to prevent Perthes disease from occurring but if your child has been diagnosed with the condition, we recommend consulting a paediatric orthopaedic surgeon as soon as possible. Early appropriate treatment of the condition gives the best chances of obtaining a good result ie preventing the onset of early arthritis in the hip joint.