Intended for healthcare professionals

Endgames Picture quiz

A limping child

BMJ 2011; 342 doi: https://doi.org/10.1136/bmj.d3565 (Published 22 June 2011) Cite this as: BMJ 2011;342:d3565
  1. Daniel C Perry, Monk research fellow and PhD student, orthopaedic surgery1,
  2. Aenone R Harper, core surgical trainee2,
  3. Colin E Bruce, consultant paediatric orthopaedic surgeon and honorary senior lecturer1
  1. 1University of Liverpool and Alder Hey Hospital, Liverpool L12 2AP, UK
  2. 2Mersey Deanery, Liverpool, UK
  1. Correspondence to: D C Perry danperry{at}doctors.org.uk

A 4 year old boy attended the emergency department with a two week history of “limping.” On further questioning he also had vague left sided pain in the knee and thigh. He was otherwise well, with no constitutional symptoms and no history of injury. On examination he was afebrile. He was reluctant to put weight on the affected leg, hurrying quickly off it when walking. Knee movements were unremarkable, but he had marked restriction of internal rotation and abduction of the left hip. Blood results showed a haemoglobin of 130 g/L (reference range 100-148), white blood cell count of 9×109 cells/L (6.3-16.2), C reactive protein of 5 mg/L (0-8), and erythrocyte sedimentation rate of 12 mm/h (2-8). Given the duration of symptoms radiography was performed. The findings were thought to be inconclusive (fig 1), so pelvic magnetic resonance imaging (MRI) was performed (fig 2).

Figure1

Fig 1 Plain anteroposterior radiograph of the pelvis

Figure2

Fig 2 T2 weighted coronal magnetic resonance imaging scan of the pelvis

Questions

  • 1 What is the name for this gait pattern?

  • 2 What are the differential diagnoses of limping in a 4 year old?

  • 3 What is the diagnosis, and what radiological features support this?

  • 4 What is the role of baseline haematological investigation in the work-up of this child?

  • 5 How should this condition be managed?

Answers

1 What is the name for this gait pattern?

Short answer

A limp caused by a shortened stance phase in the gait cycle is known as an antalgic gait.

Long answer

A limp is an abnormal gait pattern commonly caused by pain, weakness, or deformity. The term is generally used to describe a shortened “stance phase” in the gait cycle, with the person “hurrying” off one leg to offload a source of pain; it is better described as an antalgic gait. The term “limping” may be used generally to describe any abnormality of gait. Children do not have a mature reproducible rhythmic gait cycle until they are over 7 years of age,1 so it is difficult to assess gait in children below this age. To make a thorough assessment, the doctor must elicit specific changes in the child’s gait by discussion with the parents.

2 What are the differential diagnoses of limping in a 4 year old?

Short answer

Limping and knee pain in children must alert the investigator to the possibility of hip pathology. The main diagnoses to consider are fracture or soft tissue injury, transient synovitis, Legg-Calvé-Perthes disease, infective processes (septic arthritis or osteomyelitis), and developmental hip dysplasia. Rarer diagnoses include rheumatological, neoplastic, haematological, and neuromuscular diseases.

Long answer

In cases of limping in children, the differential diagnosis largely depends on age. Table 1 outlines key differential diagnoses by age group.2 Many of the diseases relate to the hip so meticulous examination of the hip is vital.

Table 1

Key differential diagnoses according to age group

View this table:

Although pathology usually arises within the hip the pain is often referred to the knee, especially in Legg-Calvé-Perthes disease and slipped upper femoral epiphysis.

Clues to the diagnosis may also be gained by observing the nature of the limp—an antalgic (painful) gait is typical of trauma, infection, transient synovitis, or Legg-Calvé-Perthes disease, whereas a Trendelenburg gait is typical of developmental hip dysplasia or Legg-Calvé-Perthes disease.

3 What is the diagnosis, and what radiological features support this?

Short answer

The plain radiographs show subtle flattening and sclerosis of the left femoral epiphysis (fig 3). The T2 weighted MRI images show altered marrow signal in the left femoral epiphysis, which is indicative of necrosis (fig 4). This is consistent with avascular necrosis of the left femoral epiphysis. In childhood, idiopathic avascular necrosis of the femoral epiphysis is known as Legg-Calvé-Perthes disease.

Figure3

Fig 3 Plain anteroposterior radiograph of the pelvis showing subtle flattening and sclerosis of the left femoral epiphysis (arrow)

Figure4

Fig 4 T2 weighted coronal magnetic resonance imaging section of the pelvis showing altered marrow signal in the left femoral epiphysis, which is indicative of necrosis (arrow)

Long answer

The radiograph shows subtle flattening and sclerosis of the left femoral epiphysis. T2 weighted MRI images show altered marrow signal in the left femoral epiphysis, which is indicative of necrosis. Legg-Calvé-Perthes disease is an idiopathic avascular necrosis of the proximal femoral head, which usually occurs in boys (male to female ratio 4:1) aged 4-8 years.3

Waldenstrom described the four classic radiographic stages of Legg-Calvé-Perthes disease—early stage, sclerosis, fragmentation, and healing.4 The early stage is characterised by widening of the joint space as a result of cartilaginous overgrowth. Sclerosis then becomes evident as a consequence of necrosis and marrow calcification.5 New vessels then invade the dead bone and resorption of necrotic bone ensues, which is radiologically apparent as fragmentation. Finally healing occurs as the cartilage is reossified. This entire process takes about three years. Our patient’s radiograph is characteristic of stage 2 (sclerotic phase) disease.

Some prognostic classifications also require a lateral radiograph to quantify the severity of disease. However, such additional imaging is usually unnecessary to establish the diagnosis, except when the presence of a slipped upper femoral epiphysis needs to be excluded in those over 8 years.

If the diagnosis is unclear additional investigations may be needed—usually magnetic resonance imaging or technetium bone scans. In our patient’s T2 weighted coronal image, the changes in the marrow signal in the left femoral epiphysis confirm the diagnosis, although the astute observer could have made the diagnosis on the basis of the plain radiographs alone. MRI offers no additional prognostic value and is not routinely performed if the diagnosis is apparent on plain radiographs.

4 What is the role of baseline haematological investigation in the work-up of this child?

Short answer

In a child with an acute limp of unclear aetiology, haematological investigations may help differentiate between septic arthritis and transient synovitis. In this case, septic arthritis and transient synovitis were unlikely because the limp had lasted for two weeks. Because the radiographs were deemed inconclusive, blood investigations were performed to look for an inflammatory arthropathy or neoplastic disease (such as acute lymphoblastic leukaemia).

Long answer

In cases of acute limping (longer than two weeks) in children of this age the primary distinction to make is between septic arthritis and transient synovitis. Numerous algorithms have been created to help in this differentiation, but the most widely used is that produced by Kocher and colleagues (table 2).6 Such algorithms include haematological values in their decision variables.

Table 2

Algorithm for differentiating between septic arthritis and transient synovitis

View this table:

In cases of persistent or chronic limps (less than two weeks’ duration) with normal radiographs, particular consideration should be given to the other diagnoses listed above. For example, around 15% of cases of childhood leukaemia present with joint pain so haematological values may help identify neoplastic disease.7 Acute lymphoblastic leukaemia may be indicated by raised erythrocyte sedimentation rate, anaemia, thrombocytopenia, leucopenia, and blast cells on blood film. Haematological parameters may also be useful in the diagnosis of rheumatological disease (raised inflammatory markers) or neuromuscular disease (for example, raised creatine kinase).

5 How should this condition be managed?

Short answer

The child should be referred promptly to a paediatric orthopaedic surgeon. Broadly speaking, the clinician will try to contain the femoral epiphysis within the acetabulum to maintain sphericity. An aspherical hip is prone to early onset of osteoarthritis.

Long answers

The treatment of Legg-Calvé-Perthes disease is the subject of considerable debate. Treatment aims to maintain joint sphericity and thereby minimise long term risk of osteoarthritis.8 Prognosis depends on the age and sex of the patient along with the severity of disease.9 The nature of the treatment also depends on the radiological stage of the disease process.

Treatments can take surgical or non-surgical approaches. Non-surgical approaches include observed neglect, usually in very young patients or those with favourable radiological signs, or abduction orthoses. Surgical treatment includes a variety of osteotomies aimed at “containing” the malleable femoral head within the acetabulum and thereby maximising sphericity. There has been a move towards surgical treatments, rather than abduction orthoses, because these have shown more favourable long term results.10

Patient outcome

Given this boy’s favourable prognostic features, which included being under 5 years of age and having a well maintained range of motion, he was managed by observed neglect. He is now entering the reossification stage of the disease.

Notes

Cite this as: BMJ 2011;342:d3565

Footnotes

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Provenance and peer review: Commissioned; externally peer reviewed.

  • Patient consent obtained.

References

View Abstract

Log in

Log in through your institution

Subscribe

* For online subscription