What is Perthes (Legg-Calve-Perthes)?

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This condition is named after three doctors who described it, in around 1910 - Dr Legg, an American; Dr Calve, a Frenchman; and Dr Perthes, a German.

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It is found in children only, generally between the ages of 3-15 years.  It occurs when the blood supply to the femoral head (ball in the hip joint) is disrupted - the cause of this is unknown.  As the bone dies, it fragments and is re-absorbed by the body, sometimes a fracture line is seen on xrays which will indicate how extensive the involvement will be.

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The growth plate can also be involved, which can lead to LLD (leg length discrepancy).  If this is the case, then a very simple procedure can be done when the child is older, where the growth plate in the knee end of the femur, on the good leg is 'stapled' to halt its growth and allow the discrepancy to be resolved more naturally.

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Eventually the blood supply is restored to the femoral head and it re-grows.  It tends to grow back more oval/ovoid in shape, but as long as it is contained in the socket (acetabulum) and moves well, the hip is functional and pain levels are pretty good, then this should last into adulthood.

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FOUR STAGES OF PERTHES



1.  Femoral head becomes more dense with possible fracture of supporting bone (takes approx. 6-12 months)

2.  Fragmentation and re-absorption of bone - re-vascularisation starts at this point, as this helps to remove the dead bone (takes a year or more)

3.  Re-ossification or Regrowth - new bone is laid down/formed 

4.  Re-modelling - final shaping of femoral head, sometimes called 'perthes healed' (both stages 3 & 4 may go on for many years)



FIRST SYMPTOMS


Usually the first symptoms noticed are a limp or pain in the groin, hip or behind the knee (this is called 'referred' pain).  In a lot of cases the child is too young to accurately describe where the pain is, or why it hurts, but will point to where it hurts.  Not all children experience pain either - it may be that they had a fall or some other sort of injury that requires an xray that shows the previously un-diagnosed damage.​​
 

DIAGNOSIS

Your GP will refer you to a paediatric orthopaedic specialist who will test your childs' ROM (range of movement) as well as organise xrays and/or an MRI.  You will then start a cycle of regular visits, most of the time involving xrays to watch what is happening.  These visits are usually at three monthly intervals to start with, but if you notice any changes and particularly if your childs pain increases dramatically, ring and organise an earlier appointment.

If you aren't happy with the treatment being offered by your specialist, particularly if your child is older (over 7 years) and the specialist has recommended a 'wait and see' approach, when you feel that being more pro-active would be beneficial, you can seek a second opinion.  However, for every specialist you see, you will be given a different treatment plan, this is because there is no standardised treatment for perthes. Every case of perthes is as unique as the child themselves and there are many factors that need to be taken into account:~

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​•  Childs age at diagnosis

​•  % of involvement, ROM (range of movement) and whether or not the femoral head is contained
•  What your specialist has been trained to do or has had success with in cases like your childs, also what treatment your hospital supports
•  What is right for your child and family



CLASSIFICATIONS

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Catterall Classification specifies four different groups to define radiographic (xray) appearance during the period of greatest bone loss.

Salter-Thompson Classification simplifies the Catteral Classifications by reducing them down to two groups:  Group A (Catterall I, II) which shows that less than 50% of the ball is involved, and Group B (Catterall Ill, IV) where more than 50% of the ball is involved.  Both classifications share the view that if less than 50% of the ball is involved, the prognosis is good, while more than 50% involvement indicates a potentially poor prognosis.

Herring Classification studies the integrity of the lateral pillar of the ball.  In the Lateral Pillar Group A, there is no loss of height in the lateral 1/3 of the head and little density change.  In Lateral Pillar Group B, there is lucency and loss of height of less than 50% of the lateral height - sometimes the ball is beginning to extrude the socket.  In Lateral Pillar Group C, there is more than 50% loss of lateral height.

Many doctors utilise these classifications, as they provide an accurate method of determining prognosis and help in determining the appropriate form of treatment.​​
 

POSSIBLE CAUSES​​
 

All that is known is that there is an interruption to the blood supply to the femoral head, resulting in bone death. What causes this to happen is widely disputed and some of the theories include:~



*  Traumatic injury to the femoral head

*  Blood clot

*  Secondary smoke

*  Poor diet, health and living conditions

There are instances of perthes showing in more than one generation of a family and also of siblings who get it. However, these are most certainly the exceptions and the chances of this happening are millions to one