In addition to the resources in this post, please see also Pediatric Orthopedics: The Limbing Or Non-Weight Bearing Child – Some Resources Posted on February 23, 2016 by Tom Wade MD
S – Septic Arthritis
This is the most urgent consideration in our differential diagnosis. The hip is the most common joint affected, followed by the knee. Lab work can be helpful, as well as adjunct use of US of the hip to look for an effusion, but sometimes, regardless of the results, the joint just has to be tapped to know for sure. [emphasis added]
T – Toddler’s fracture
This is usually a torque injury when the wobbling toddler pivots quickly or trips and falls. Toddler’s fractures occur in children 1 to 3 years of age, most commonly in the distal 1/3 of the tibia. Sometimes a long-leg cast is needed, but currently there is a new trend in foregoing casting in mild cases. [For more see Toddler’s Fracture BY DR SEAN FOX · FEBRUARY 1, 2013 of Pediatric EM Morsels
O – Osteomyelitis
Bacteremia – from any source – can seed into any bone. It’s not very common, but it happens: approximately 2% of children who present to an ED with limp will have osteomyelitis. Plain films, ESR, and CRP are a fair screen to start. For more than the casual concern, MRI is the best modality to evaluate, followed by radionuclide scintigraphy. Although not the first choice modality, CT can show periosteal changes, such as inflammatory new bone formation or periosteal purulence
P – Perthes disease
This is the famous Legg-Calvé-Perthes idiopathic avascular necrosis of the hip, usually affecting children from 3 to 12 years. They present with a slow onset pain and with an antalgic gait. Patients will have trouble with internal rotation and abduction of the hip. Radiographs may be initially normal. MRI can show the culprit: decreased perfusion to the femoral head and subsequent necrosis.
L – Limb-Length Discrepancy
I – Inflammatory
Transient Synovitis. This is what we want them to have right? The typical age is between 3 and 6 years, sometimes just after a URI. To be comfortable with this diagnosis, we should have considered all of the dangerous diagnoses, the child should be well, afebrile, in minimal discomfort, and he should respond almost completely to an NSAID. He’s the one running up and down the department after treatment – or just from sheer boredom after observation.
M – Malignancy
Primary bone tumors such as Ewing’s sarcoma or osteogenic sarcoma typically affect older children. Limping, however, may be a presenting symptom of leukemia. If you have any suspicion of the general wellness of the child, get a screening CBC, and perhaps a peripheral blood smear. Whatever you do, make sure you get close follow up for these kids that are on your malignancy radar — the blast crisis may not have occurred yet – but it can happen hours to days later.
Plain films are insensitive for leukemic involvement of bone but they may show diffuse osteopenia, or metaphyseal bands – symmetrical high-uptake markings around the joint. They look like stacks of paper within normal bone – you can see them also in anemia, lead poisoning, and other causes. Also look for periosteal new bone formation, sclerosis, or lysis.
P – Pyomyositis
This usually presents with vague irritability, pain, and fever, and sometimes after subacute minor trauma. These children do not appear well.
Also think about simple run-of-the-mill myositis, usually from a viral cause, such as influenza. Typically the calves are affected and are always tender. Hydration and supportive therapy are indicated for viral causes.
For bacterial focal pyomyositis, give empiric antibiotics, admit them for a major inpatient workup, and think about early surgical consultation if you think you need sepsis source control.
I – Iliopsoas Abscess
Children most often will develop a primary abscess from bacteremia from an unresolved infection. Adults more commonly form secondary abscesses from Crohn’s disease, post-op complications, a vertebral infection, or even a bad chronic urinary tract infection. Lest you think this is a dramatic presentation, think again: iliopsoas abscesses present with protracted vague symptoms of back, flank, abdominal, or hip pain, and sometimes with fever. The median time from symptoms to diagnosis in children is a whopping 20+ days, according to one study. If iliopsoas abscess is starting to get your attention, get the CT or MRI.
N – Neurologic
Not to be alarmist, but children do have strokes; unlike adults, half are hemorrhagic, and half are thromboembolic. Typically they’ll have some underlying pathology that will alert you, such as a cardiac lesion, sickle cell disease, or a complicated infectious or metabolic history. The good news is that it won’t just be a limp – you’ll have some other neuro sign or symptom to go after.
Guillain Barré is another thing to consider – early lower extremity weakness may present as a limp or refusal to walk. Maybe it’s not the hip that should be tapped, but the spinal canal.
Think also about muscular dystrophy or peripheral neuropathy and its possible underlying etiology.
G – Gastrointestinal and Genitourinary
What else could be going on? Appendicitis may be faking us out here. Perhaps there is a hernia, or testicular or ovarian torsion, all of which can present as lateralizing pain and not wanting to walk. Think outside the box.
Septic Arthritis vs Transient Synovitis
In their original paper in 1999, Dr Kocher et al. performed a retrospective analysis of children who were being evaluated for a septic joint versus transient synovitis over a 15 year period, in a major referral center. They came up with four independent predictors of a septic joint, and calculated the probability of septic arthritis based on the number of features present. In 2004 the same group validated their prediction tool, with a slightly decreased sensitivity and specificity in the validation population.
In short, the Kocher criteria are not perfect, but it’s the best evidence we have at the moment.
The four predictors are:
Inability to walk
Fever of 38.5 °C or greater
ESR > 40 mm/h
WBC > 12,000/mm3 (12 x 109/L)
Bonus mnemonic: Walk FEW: Inability to Walk | Fever | ESR | WBC
The probability of septic arthritis increases with increasing predictor. In this prediction model, each predictor has the same weight.
Probability of Septic Arthritis (Kocher et al. 1999)
0 Predictor – <0.2 %
1 Predictor – 3%
2 Predictors – 40%
3 Predictors – 93.1%
4 Predictors – 99.6%
Now, remember, this is to be used in children in whom you already have some suspicion of a septic joint. So, 0 predictors, generally you’re alright. 1 predictor, you may start to worry. Once you have 2 predictors, your chances jump for 3% to 40%. You really have to go looking.
The Kocher caveat is that there is no single test or single decision rule that will stop you from investigating if you are concerned enough. Don’t have too much faith in this imperfect decision tool – we use it because we need somewhere to start. Treat and push for the aspiration of the hip if you are left in doubt. Septic arthritis can be devastating if not identified early.
Emergency Medicine Cases podcasts has an outstanding two hour podcast seminar – Episode 35: Pediatric Orthopedics Pearls and Pitfalls [The link is to the podcast and the podcast notes]. The section on the limping child runs from 19:20 to 1:04:00. And be sure and review and download the incredibly good pdf notes for this podcast!
Here are the notes to the above podcast about septic arthritis vs. transient synovitis:
APPROACH TO THE CHILD WITH A LIMP:
1)Rule out septic arthritis
2)Look for fractures, which can be very subtle, and ask about trauma
3)Look for clues of systemic illnesses such as a rash, fever, bruising Assess the persistence of the limp from the history and observations of the child. Give analgesia, which can help improve the physical exam. Use distraction and observation of the child at play to complete a full physical examination (4).
SEPTIC ARTHRITIS vs. TRANSIENT SYNOVITIS?
Transient synovitis of the hip is a selflimited inflammation of the synovial lining. It is often preceded by a viral infection, and should resolve in 3–10 days. However, concurrent illness can make diagnosis challenging. Pay attention to vital signs, general appearance (well or unwell appearing) and symptom progression.
The Kocher criteria for predicting septic arthritis gives increasing probability for each of the following criteria met (5):
1) non-weight-bearing on affect side
2) ESR > 40 mm/hr
4) WBC >12,000
The Kocher rule is helpful to rule-in higher pre-test probability patients. Fever is probably the best criteria. What about CRP? Lack of fever and a CRP<2.0 has a good predictive value for ruling out septic arthritis (6) when pretest probability is low.
Ultrasound? Presence of an effusion can support a diagnosis, but cannot rule out septic arthritis.
Treatment: in patients you suspect septic arthritis, usually you can wait to start empiric IV antibiotics until after the joint can be aspirated. However, if there will be a significant delay, start antibiotics first
Irritable Hip (transient synovitis) [But it is only transient synovitis after you have carefully considered every other cause]
Commonest reason for a limp in the pre-school age group.
Usually occurs in 3-8 year olds
History of recent viral URTI (1-2 weeks)
Child usually able to walk but with pain
Child otherwise afebrile and well
Mild-moderate decrease in range of hip movement – especially internal rotation.
Severe limitation of hip movement suggests septic arthritis.
Transient synovitis is a diagnosis of exclusion. Symptoms overlap with those of septic arthritis. If diagnosis in doubt, consult with orthopaedics.