Written by Loredana Guetg-Wyatt, CEO of Steps Charity Worldwide for Nursing in Practice
Children quite often turn up at the school nurse’s office, or are brought to the local GP practice, with pain that isn’t easy to explain. If they’re particularly active children – and especially if they’re smaller than most of their peers – the fairly obvious conclusion is that they’ve probably done some not very important damage, and that the best approach is a ‘wait and see’ one. And obviously, this is usually right. However, repeated leg pains can signal a condition that is rare, but needs to be identified early, because the later the diagnosis the bigger the risk of permanent damage. It is only just over a century since Perthes disease (also known as coxa plana, Legg-Calvé-Perthes, Legg-Perthes, and/or Legg-Calvé), a disease which affects the hips in children, was first identified.
The patient in practice
For some reason – researchers are yet to establish how or why – Perthes affects the blood supply to the hip joint: specifically, to the rounded head of the femur where it fits into the hip socket, and to the growth plate (physis). Over time, this blood loss means that the bone starts to soften and break until the blood vessels regrow and new bone is produced. This may take several years – and importantly, the new bone growth may not be in the ‘right’ shape to fit properly into the hip socket.
In practice, this means that children present with pain in their hips, groin, legs and/or knees (this may be referred hip pain). They may also be limping, and/or find it difficult to get the full range of movement with their hips. It may have come on suddenly or have been happening for some time.
This is not the only symptom that distinguishes children with Perthes Disease, though. They are usually boys (four out of five patients), and Daniel Perry, who is the associate professor of orthopaedics and trauma surgery at Oxford University’s Nuffield department of orthopaedics, rheumatology and musculoskeletal science as well as an honorary consultant Children’s Orthopaedic Surgeon at Alder Hey Hospital, explains some of the classic physical characteristics. ‘My patients are usually shorter than average, and they tend not to have grown much in the past year – in fact they are often the shortest child in the class. They’re a little bit wiry, and they’re also a bit hyperactive, compared to other children. In addition, they’ve sometimes got some kind of genitourinary abnormality such as a hernia, or undeveloped testes or hypospadias.’ These are the children, therefore, who’re more likely to ring alarm bells for Perthes if they keep showing up with pain.
The bone condition
The reason for their pain is what is happening to their hip joint. The bone changes go through the initial necrosis, sclerosis, fragmentation and reossification phases, before reaching the final ‘healed’ stage. As the new blood vessels form the dead bone is broken down and reabsorbed, while new bone is formed from the outside in. In the final reossification stage the central bone of the new femoral head is formed.
There are two main problems. One is the pain and mobility difficulties that the young patients usually experience while the hip is unable to work properly, and which often brings them back to see practitioners. The other is that the new bone does not always reform into the original rounded shape. It may be a more oval ‘rugby ball’ shape or really quite flat. The more it diverges from a ball shape, the less likely it is to fit properly into the hip socket, affecting mobility permanently and causing pain as well. A significant proportion of adults who had Perthes as children need a hip replacement in later life. And the later the condition is diagnosed, the more likely it is that they’ll continue in pain that isn’t taken seriously – and even more importantly, if the bone is reforming badly, this won’t be noticed till there’s been permanent damage.
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Understanding a painful, little-known condition in children: Perthes disease