sBMJ | The limping child

The limping child

PHOTOS.COM

Tosan Okoro takes us through the approach and management of limp disorders in children

A limp is a common reason for a child to present to the doctor.¹ Because of the long list of potential diagnoses, some of which demand urgent treatment, an organised approach to evaluation is required. It is essential to understand the components of gait and the pathophysiology of specific abnormalities. Gait reflects the coordinated action of the lower extremities. The body moves forwards smoothly with economy of motion and energy. The stance phase (60% of the entire gait cycle) is the weight bearing portion.² It is initiated by heel contact and ends with toe lift-off from the same foot. Swing phase is initiated with toe off and ends with heel strike. Limb advancement occurs during the swing phase (40% of normal gait cycle; fig 1). During this phase the foot pronates first and then supinates. Pronation shortens the foot, which helps it to clear the ground. Pronation also minimises the energy expenditure necessary for ground clearance as the non-weight bearing limb passes the weightbearing limb.² Supination stabilises the bony architecture of the foot thus preparing it for heel strike, when the foot must absorb the shock of striking the ground. Table 1 shows the developmental progression of a child’s gait, which should be incorporated into the assessment.

Gait differences

The gait of a child is different from that of an adult for the first three years of life.⁵ Children typically take a lot more steps per minute at a slower speed than adults to compensate for their immature balance. Toddlers tend to flex their hips, knees, and ankles more than adults in order to lower their centre of gravity and improve their balance.⁵

History

The history for a child with a limp should be detailed (see box 1). The examination of a child starts with basic observation, which depends on the age as well as the level of cooperation and discomfort. The hip is most commonly examined, but one should not fail to consider referred pain from the knee. It is best to follow the normal orthopaedic routine of look, feel, move, and special tests outlined in table 2.

The common causes of limp by age group are in box 2. If there has been unilateral limitation of all hip movements, spontaneous recovery after bed rest, and normal radiology, a retrospective diagnosis of transient synovitis of the hip is made if all three prerequisites are met. If other joints are involved, juvenile idiopathic arthritis should be considered.

Investigations

The investigations that are useful in the assessment of a limping child are given in table 3.

Treatment options

The therapeutic options depend on the diagnosis. The options are laid out in box 3 (on studentbmj.com) along with salient clinical features and investigation findings for each clinical condition.

In conclusion, a variety of causes exist for a limp in a child, but it is important to bear in mind the components of the gait cycle in order to assess this common complaint. The tried and trusted sequence of history taking, clinical examination, investigations, and management applies more than ever.

Table 1 Developmental stages of gait⁴
Age (months)	Developmental stage
10-12	Cruises while holding on to objects
12-14	Walks short distances and stands unaided
17-21	Walks on one foot long enough to walk up steps
30-36	Balances on one foot for more than one second
36	Develops sufficient balance to attain a normal gait pattern

Box 2: Common causes⁷

1-5 years old

Trauma
Transient synovitis
Osteomyelitis or septic arthritis
Developmental dysplasia of the hip
Juvenile rheumatoid arthritis

5-10 years old

Trauma
Transient synovitis
Osteomyelitis or septic arthritis
Legg-Calve-Perthes disease

10-15 years old

Trauma
Osteomyelitis or septic arthritis
Slipped upper femoral epiphysis
Chondromalacia
Neoplasm

Box 1: History — questions to be asked⁶

Duration and progression of limp?
Recent trauma and mechanism? Beware limitations of paediatric history and possibility of unintentional trauma
Associated pain and its characteristics?
Accompanying weakness?
Time of day when limp is worse?
Can the child walk or bear weight?
Has the limp interfered with normal activities?
Presence of systemic symptoms like fever, weight loss?
Do not forget the medical history, BIND—birth history, immunisation history, nutritional history, and developmental history
Also include the other essentials—drug history and allergies and family history

Table 2 Examination of a child⁷
Examination	Points to consider
Look	For evidence of deformity, erythema, swelling, effusion, limitation of motion, asymmetry. Assess shoes for unusual wear on the soles, asymmetry, point of initial foot strike, and also assess the fit. In older children look for scoliosis, midline dimples, and hairy patches, which could indicate spinal pathology. Assess gait with the child barefoot. Any discomfort as the child bends down
Feel and move	Measure true leg length from the anterior superior iliac spines to medial malleoli. Assess thigh or calf circumference if asymmetry suggests atrophy. Feel for warmth, fluctuance, palpable masses, stiffness. Assess range of movement, laxity, stiffness with guarding, pain, discomfort, and fluidity
Special tests	Neurological assessment of the lower limbs is essential.⁶The range of spinal motion (in flexion and extension) should be tested and recorded. Prone internal rotation of the hip is the most sensitive test for intra-articular pathology. With the child prone and the pelvis kept flat on the table, the knees are flexed and the ankles left to fall away from the body. Any inflammation in the hip manifests as decreased internal rotation of the hip. The FABER test ( hip flexion, abduction and external rotation) is performed by placing the ipsilateral ankle on the contralateral knee in the supine patient and then providing gentle downward pressure on the knee. This test is positive if it causes pain in the sacroiliac joint which may be involved in adolescents in infectious and inflammatory conditions. The Galeazzi test is performed by putting the child in a supine position and bringing the ankles to the buttocks with the hips and knees flexed. The test is positive when the knees are at different heights, suggesting developmental dysplasia or a leg length discrepancy

Table 3 Investigations for assessing limp in children^7-10
Investigation	Aids to diagnosis
Full blood count	Differential white cell count
Erythrocyte sedimentation rate	More specific in indicating the presence of infection than C reactive protein assay but not as sensitive
C reactive protein assay	Most sensitive early test for musculoskeletal infections; abnormally high values rapidly return to normal after effective treatment
Joint aspiration	If effusion is present. Requires cell count and differential, Gram’s stain, and culture and sensitivity
Blood cultures	For causative organism in septic arthritis, and osteomyelitis; it may need to be repeated at peaks of temperatures
Imaging	Plain x ray of hip as part of initial study. Yield is low if specific findings are not noted on physical examination. X ray of the limb above and below the affected area may also be useful. A bone scan is sensitive but not highly specific; it defines areas of increased or decreased metabolic activity caused by neoplasm, infection, or avascular disease. Ultrasound is useful for assessing for joint effusion or abscess. Computed tomography defines bone and soft tissues anatomically. Magnetic resonance imaging is most effective in evaluating neurological disorders such as disciitis and spinal tumours
Surgical	Hip arthroscopy is also an option; it is significantly less invasive than arthrotomy and avoids dislocation of the femoral head and the corresponding risk of osteonecrosis.

Fig 1 The gait cycle³

Box 3: Therapeutic options^7-11
Trauma

Diagnosis is by plain x ray as a primary investigation. Anteroposterior and lateral views are indicated.
Treatment is by appropriate immobilisation

Transient synovitis

Commonly occurs after a respiratory illness.
Full blood count and erythrocyte sedimentation rate normal or slightly elevated
X ray image may be normal
Ultrasound may show effusion
Main treatment is bed rest and physiotherapy.
Non-steroidal anti-inflammatory drugs are useful for treatment and can shorten the duration of symptoms in children

Septic arthritis or osteomyelitis

Blood cultures are commonly positive
Raised white cell count and C reactive protein, which normalises more rapidly than erythrocyte sedimentation rate once infection is brought under control
X ray images show delayed changes. Radiographic evidence of acute osteomyelitis first is suggested by overlying soft tissue oedema at 3-5 days after infection. Bony changes are not evident for 14-21 days and initially manifest as periosteal elevation followed by cortical or medullary lucencies. By 28 days, 90% of patients show some abnormality. About 40-50% focal bone loss is necessary to cause detectable lucency on plain films
Joint aspiration is the definitive diagnostic procedure and the most common pathogen isolated is Staphylococcus aureus
Emergency orthopaedic consultation with subsequent aspiration, arthroscopy, drainage and debridement is required. Antibiotics are required as adjunctive treatment.

Legg-Calve-Perthes disease

X ray image shows widened joint space between ossified head and acetabulum
Radionuclide bone scan or magnetic resonance imaging helps evaluate for avascular necrosis
If avascular necrosis is shown, bracing, physiotherapy and protection of the hip may be indicated. An operation to “contain” the femoral head within the acetabular cup may sometimes be necessary. This is known as a femoral varus osteotomy, and it is done with or without rotation to redirect the ball of the femoral head into the socket of the acetabulum

Slipped upper femoral epiphysis

Most common in obese or rapidly growing prepubescent male children (aged 12-15 years)
There’s 25% bilateral involvement
X ray shows widening and irregularity of the plate of the femoral epiphysis. The displacement of the epiphyseal plate is medial and superior. Surgical pinning of the hip is usually required and should be done quickly.

Developmental dysplasia of the hip

Must be detected early
Delayed identification leads to more prolonged morbidity
Classic screening tests are Barlow’s and Ortolani’s. Ortolani’s test assesses if the hip is dislocated, and Barlow’s test assesses whether the hip is dislocatable. Ultrasound scanning is usually done
Management depends on age. 0-6 months requires a Pavlik harness. The Pavlik harness is fit to the baby and attempts to place the hips in the human position by flexing them more than 90 degrees (preferably 100-110 degrees) and maintaining relatively full, but gentle abduction (50-70 degrees). This redirects the femoral head towards the acetabulum and spontaneous relocation of the femoral head occurs typically in 3-4 weeks.
Above six months requires closed reduction and the use of a Spica cast. A spica cast is a special type of cast used to immobilize the hip joints and it usually extends from the mid-chest down to below the knee. If the problem is on both hips, then the cast will extend past both knees, or if the problem is only on one side the cast will extend below one knee. A hole is left in the groin are to allow the child to use the bathroom or for diapers to be changed. This cast is usually left in place for 6-8 weeks

Neoplasm

Osteogenic sarcoma causes an acute unremitting limp or limb pain and often involves the distal femur and proximal tibia
A haematological problem, such as leukaemia, causes ill defined migratory bone or joint pain and generalised weakness, and a neuroblastoma can produce nerve impingement
Appropriate treatment is multidisciplinary and involves referral to paediatric oncology and orthopaedics.

Juvenile rheumatoid arthritis

Autoimmune disease that may present affecting a single ankle or knee (pauciarticular)
Presence of associated systemic findings such as high fever, a salmon coloured pink rash and eye inflammation are also useful in diagnosis
Treatment is also multidisciplinary and involves the paediatric rheumatologists, ophthalmologists, orthopaedic surgeons, rehabilitation specialists, and occupational therapists

Tosan Okoro, senior house officer, neurosurgery,Walsall Manor Hospital
Gabriel Alo, consultant,orthopaedic surgeon, Queen Elizabeth Hospital, Birmingham
Email: Tosanwumi@hotmail.com

studentBMJ 2006;14:1-44 January ISSN 0966-6494

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