The Evil Twin - Orthopaedic Problems in Children Pt 2: Painful Presentations

Pretty much every individual symptom in children is likely to be something which is either normal or at very least will follow a benign course. Orthopaedic presentations are no exception.  If you've already read part 1 (orthopaedic problems in children) and came away with the impression that almost all children with bow legs, knock knees, in-toeing etc are essentially normal and that the problem is likely to self-resolve, you're not wrong.

This is one of the wonderful things about paediatrics.  Many concerning presentations are actually normal, allowing us to feel like we've done something great just by reassuring a parent that their child doesn't have anything wrong with them.  Also, many problems self resolve allowing us to take a light touch approach, avoiding unnecessary tests or treatment, always remembering to act in the best interests of the child.

These factors are also one of paediatrics greatest difficulties.  Everything is normal, except when it isn't and everything in children's health has an evil twin.

Let me give you some non-orthopaedic presentations as examples.

Paediatric orthopaedics is similarly riddled with presentations where the likelihood is that it is something that needs no intervention, while there always exists the possibility of a much more problematic pathology.  Like the evil twin (often used as a complicated anti-hero in literature and film) concept, the pathology that we have to be wary of usually shares many characteristics with the more benign explanation for the symptoms.  Since common things are common, the temptation is always to presume the more likely option. So how do we recognise the more dangerous orthopaedic problems, while avoiding over-investigation and over-referral?

First, it is important to know what is typical so that we can know what is atypical.  For example, irritable hip is usually seen from the age of one to six years old.  It can occur outside of that age range but is uncommon and so is diagnosed with an appropriate caution.

If a preschool child has a fall, the outcome is usually no injury or a fracture.  Sprains are uncommon in this age group because they are too flexible to easily strain a ligament to the point of injury.

Once we are familiar with what is both normal and common, it is important to know what the signs are of the common and expected, we need to know what should alert us to the more significant yet less common pathologies.  In other words, what are the red flags?

There are some red flags that are fairly reliable and these are listed here.

However some of the red flags that are listed elsewhere are rather contextual, proving the evil twin problem.  For example, Arthritis Research UK lists nocturnal pains as a red flag symptom (1) while NHS choices lists nocturnal symptoms as a typical feature of growing pains (2).  That is  why red flags will only get you so far.  Sometimes certain presentations are a set piece.  Here are a few examples:

A 12 year old presents with bilateral knee pain, worse on the right.  The pain is worse after sports and is particularly bad on stairs.  He is limping.  Both knees have full range of movement and no effusion.  The tibial tuberosity is swollen and tender in both knees.

This is Osgood-Schlatters disease.  Simple.  This problem of adolescence is more a biomechanical problem than a true disease process.  There is little that can be done for this problem apart from symptomatic treatment and a careful management of the balance between being active and being in pain.  An orthopaedic surgeon can't fix this problem unfortunately.

A 7 year old presents with a limp and pain in the hip.  There is no history of injury.  They are not unwell or febrile.  Simple analgesia has helped but the limp is still obvious.  Examination is normal apart from a reduced internal and external rotation of one hip.

There are various possible explanations for this presentation, however index of suspicion for Perthe's disease has to be very high.  The mysterious onset of symptoms that is typical of Perthe's diease makes it a difficult diagnosis.  The early recognition of the disease is further hampered by the tendency that children have to reduce activity instead of increasing their complaining.  Orthopaedic surgeons don't have a magic treatment for Perthe's but will do everything they can to reduce the progression of this difficult disease.  X-ray or referral at presentation is recommended for a patient like this.

A 13 year old presents with what they think is a knee injury.  They have had some left knee discomfort which was made much worse by running yesterday.  Today, the pain is significant despite analgesia and they have a marked limp.  The most notable clinical finding is that movements of the left hip are restricted by pain.

This could be a muscular or ligamentous injury.  However it is also possible that this young person has a slipped upper femoral epiphysis.  The growth plate in adolescents is at risk of fracture and the subsequent movement can cause permanent damage if not treated as soon as possible.  These presentations are tricky as they come with a story that sounds more like a straightforward soft tissue injury.  The important thing is to have a high index of suspicion and a low threshold for X-ray or same day referral.

Edward Snelson
@sailordoctor
Specialising in conjoined Meducaction

Disclaimer: Once again, many thanks to the team of orthopaedic surgeons at the Sheffield Children's Hospital. This concludes the planned mini series of paediatric orthopaedic posts but if you have further questions or simply wish to tell us your favourite orthopaedic surgeon joke, please post in the comments box below.

References

1. Foster E et al, Growing pains: a practical guide for primary care, www.arthritisresearchuk.org
2. Growing pains (recurrent limb pain in children), NHS choices website

Why Do Different Children Wheeze Differently? - Simple, but first you have to understand all of paediatrics (also simple)

When a child or young person has one or more wheezy episode, there are various possible causes.  The vast majority of paediatric wheeze is caused by bronchiolitis, viral wheeze and asthma.  It is easy to confuse these conditions, but clarity of diagnosis has real benefits when it comes to providing evidence based treatment.

We know that getting the diagnosis right isn't straightforward, possibly because there are no tests which reliably distinguish these entities from each other in children.  For example, evidence suggests that 50% of children diagnosed as asthmatic do not have asthma (1).  One knock-on effect of any diagnostic difficulties is that people make up rules for us.  "Asthma should not be diagnosed under the age of 5 years."   "Inhalers don't work under the age of 12 months."   These rules are meant to be helpful, but they are both wrong.  If you were only playing the odds, living by these rules would be the way to go, but clinical medicine is also about pattern recognition.  If it looks like a duck etc.

I think that it is possible to embrace the rules, while also knowing when to break them.  I believe that there is a simple model for understanding paediatric wheeze which fits into the probability model and the pattern recognition model.  It's fairly simple and all it requires is a good understanding of all of paediatrics.

Paediatrics isn't the art of learning 30,000 rare conditions.  Paediatrics is mostly about understanding what conditions affect children at different ages and how children respond to those illnesses.  That in turn allows us to recognise and treat appropriately wherever possible.  When it comes to infections and immune responses, unsurprisingly the immune system plays a big role.  Of course a child's immune system goes through several stages and each one dictates a different response to infection and allergens.

How does a baby fight infection?  In simple terms, they don't.  Inherited antibodies do most of the work for the first few months.  Few pathogens get past these antibodies and so the baby's own immune system does very little.  This has lots of implications.  Infections that do occur are unlikely to be common viral illnesses and whatever the pathogen, the baby will be at greater risk from that infection.  Even the recognition of an unwell baby is affected by their lazy immune response.  Temperature of 40C in a 7 day old?  Pull the other leg.

These maternal antibodies eventually run out.  The immune system has to learn and develop.  Older children, like adults have a complex and clever immune system which has stored a wealth of information about the pathogens in their environment.  This allows the older child to produce a response to infection that is not just complicated but sometimes over-complicated.

So how does a human survive in-between losing maternal antibodies and learning a more complex immune response?  In scientific terms, their immune system goes nuts.  You have seen it yourself: even with a relatively simple and uncomplicated viral infection, the younger child can have very high temperatures, various rashes and of course viral wheeze.  Other things that are common in this age group are quite possibly in part due to this exaggerated immune response - irritable hips and febrile convulsions.

These three ways of responding to infection align very nicely with the three entities that commonly cause wheeze at different ages in children.

So, the rules about age do have a solid basis.  Would you diagnose asthma when a six week old becomes wheezy?  Please don't.  Would you diagnose bronchiolitis in a 12 year old?  No.

Age alone does not give you the diagnosis since there is some overlap.  Thankfully, because each condition represents a different immune response, they each present with slightly different clinical features. As a result we can combine probability with pattern recognition.  The best bit is that the pattern recognition fits well with these three immunological stages of childhood.

What happens when you are a baby and a virus causes a respiratory tract infection?  In most cases, the answer is simply wetness.  Bronchiolitis is what you might expect from an immune system that has not yet fully woken up from its cocoon of maternal antibodies.  Bronchiolitis tends to slowly progress over days from cough and coryza to wheeze and suboptimal feeding, finally ending up with a variable degree of respiratory distress.  It progresses over days.  The severity and progression of these symptoms will vary from child to child, however the gradual onset is characteristic.  This is not to be confused with deterioration, which can be sudden, especially in high risk babies.

Viral wheeze by contrast tends to come on quickly, over hours rather than days.  This is because in viral wheeze is a different response to the same viral trigger.  In children between the ages of about 1 and 6, when the immune system sees a new virus, it tends to go a bit crazy.  One of the effects of this immuno-enthusiasm seems to be that that many children experience bronchospasm as part of that immune response.  So in addition to being able to tell which is more likely (bronchiolitis or viral wheeze) by the age of the child, the rapidity of the onset of the wheeze is a clue.

Why does it matter that we tell the difference?  These two different entities respond differently to treatment.  The slow development of inflammation and wetness in the airways that is bronchiolitis does not respond to bronchodilators while the bronchospasm of viral wheeze does.  This is probably the reason for the perpetuated myth that children under the age of one don't respond to beta-agonists.  They do, but only if they have bronchospasm (viral wheeze) as opposed to mostly wetness (bronchiolitis).

Finally, when your immune system moves from the "shoot first, ask questions later" mode into adult mode, asthma becomes the most common cause of wheezing in children and young people.  The trouble is that this isn't something that happens suddenly and it certainly isn't the case that there is a consistent age for this to happen.  Once again though, odds are very much affected by the age of the child.  Does the 8 month old have asthma?  No.  Does the 15 year old have episodic viral wheeze.  Almost certainly not.  Once again, the fact that the different entities represent different stages of immune system maturity translates into both probability and pattern recognition.  The 3 year old is probably having episodes of viral wheeze, but this will be confirmed by the fact that all episodes are precipitated by viral illnesses and the lack of interval symptoms.  The 10 year old probably has asthma and if this is the case they will be having episodes of wheeze not just when they get viral illnesses.

This explains the contradictions between all of the things that we know about asthma in children.  We are told that we shouldn't diagnose asthma under the age of five.  That rule works well from a probability point of view but not from a pattern recognition point of view.  What would you do if a 3 year old has a chronic cough and multiple episodes of wheeze that are not all provoked by viral illnesses?  I think that this child might be the exception to the probability rule.  Equally, in a 2 year old with chronic cough and no history of wheeze the temptation to diagnose asthma is a dangerous one given both the lack of  probability and the absence of a classic history.

Understanding the way that children respond to infection at different ages tells us a lot about where (what age) to look for each diagnosis and what to expect (the classic history) to find in order to confirm that diagnosis.  This allows us to maximise the chances of giving the most appropriate treatment, most of the time.

When there is a discrepancy, we need to be aware that probability and pattern have not agreed, and have a low threshold for rethinking.

Edward Snelson
Occasional rule analyst
@sailordoctor

Disclaimer: No-one understands all of paediatrics.  I mean really, who can explain why children will eat glue and drink air freshener but refuse to eat the food that you want them to eat?  That's why it's best to stick to the basics (like immunology) and leave the complicated stuff to the parents.

References

1. Ingrid Looijmans-van den Akker, Karen van Luijn and Theo Verheij, Overdiagnosis of asthma in children in primary care: a retrospective analysis, Br J Gen Pract 2016; 66 (644): e152-e157