The Limping Child

Lawson A. B. Copley

Among the causes of gait abnormality in childhood, those that should be kept in mind in acute settings include infection, trauma, and malignancy. Children who develop a limp acutely should be evaluated carefully with a detailed history and physical examination, appropriate radiographs and laboratory studies, and timely referral for subspecialty evaluation in order to exclude these potentially worrisome causes. When necessary, the lower extremity should be carefully immobilized and protected from weight bearing until a definitive diagnosis can be achieved. When infection is suspected, the workup should be conducted in either an observation or inpatient status until the diagnosis is confirmed or excluded. This ensures that appropriate diagnostic and therapeutic resources can be brought to bear in a timely manner before the infection worsens without a correct diagnosis. Regardless of the underlying cause of the limp, vigilance is necessary in order to make an accurate diagnosis in a timely manner to ensure the best outcome.

MUSCULOSKELETAL INFECTION

Infections of bone and joint are discussed in Chapter 234.

From an epidemiological perspective, the most common cause of an unexplained limp in childhood is infection. Whereas injury generally occurs as a discretely observed event and results in a sudden onset of limited mobility, infection often has a more insidious onset. Following trauma, radiographs usually reveal the alteration in skeletal anatomy which makes the diagnosis clear. Although exceptions may exist, such as Salter Harris type 1 physeal injuries or occult elbow fractures with positive fat pad signs, the ability to distinguish fractures with plain radiographs is usually straightforward. However, with infection, plain radiographic findings may be subtle, with deep soft tissue swelling being the first identifiable sign in many cases.

Trauma may be reported as an antecedent event in approximately 35% of children with infection.¹ In these circumstances, the physician should be mindful of subtle details in the history and physical examination. One should ask about the timing of the injury with respect to the onset of symptoms, the mechanism of injury, and the presence of fever. One should also inspect the area of concern for signs of erythema, warmth, and swelling that may not be consistent with injury, based on the reported timing or mechanism of the injury.

Whenever infection is suspected, laboratory studies should be obtained to assess for a systemic response to the infection. These should include a complete blood count (CBC) with differential, C-reactive protein (CRP), and the erythrocyte sedimentation rate (ESR). Among these studies, the most sensitive test for identifying the inflammation associated with acute musculoskeletal infection is the CRP.² Abnormalities of the infectious indices should raise the level of concern and motivate the physician to perform more dedicated imaging to help define the nature and extent of the problem.

If a precise location can be determined from physical examination, then magnetic resonance imaging (MRI) with and without intravenous contrast is the most sensitive and specific study to evaluate for infection, even if the onset has been within 24 hours.³ Findings from the MRI will be useful to guide surgical decision making, if indicated, as the spatial extent and involvement of various tissue types can be identified. If infection is suspected, but the location is uncertain, then bone scintigraphy is preferable.

TRAUMA

Trauma is far more common in childhood than infection or malignancy. However, it is seldom that any diagnostic dilemma occurs because of limping in the aftermath of an injury. Frequently, children with fractures and severe contusions present to medical attention in a timely manner. The history is consistent with injury, without suggestion of fever or malaise. Physical findings often demonstrate bruising or swelling without erythema. Radiographs are indicated to evaluate for fracture, dislocation, or physeal injury. These radiographs should include at least two views of the area of injury and should span the regions including the joint above and below the area of involvement.

When radiographs do not demonstrate obvious skeletal injury, the soft tissues should be inspected to look for other signs of injury, such as joint effusion, ligament avulsions, or soft tissue swelling. Clinical findings of tenderness directly over a growth plate, despite negative radiographs, may suggest a possible growth plate injury that should be protected as a fracture, as this is a far more common injury than a sprain in childhood.

If a fracture or growth plate injury is suspected, then the timing of subspecialty referral should be determined. Fractures that are displaced or angulated should be addressed acutely with conscious sedation and closed treatment with manipulation followed by appropriate immobilization. This should be performed by an orthopedic surgeon, or the surgeon’s designated associates, in the emergency room. Occult fractures, suspected Salter Harris type 1 physeal injuries, or nondis-placed fractures should be immobilized carefully with weight-bearing protection provided and subsequent outpatient follow-up should be arranged with an orthopedic surgeon.

Care must be taken to immobilize the lower extremity to ensure that the site of injury is protected and that ample padding is used to prevent heel pressure ulcers or marginal skin breakdown from the splint. Instruction should be given with an assistive device to aid ambulation and prevent further injury that may occur if the child is unable to ambulate safely. In general, it is safer for small children to use a walker than to use crutches. If necessary, a wheelchair may need to be provided for long distances or if the child cannot ambulate safely with a walker.

An important condition to keep in mind in the discussion of a traumatically related limp is slipped capital femoral epiphysis (SCFE). Children and adolescents from approximately age 9 to 14 are at risk for developing this condition if they are overweight or have underlying endocrine abnormalities. If a limp is present with associated pain in the thigh or knee in an individual in this age group, it is important to obtain anteroposterior (AP) and lateral radiographs of both hips to evaluate for this condition. If a SCFE is suspected, subspecialty consultation should be obtained immediately to determine the treatment plan. Children with a suspected SCFE are admitted to the hospital to prevent inadvertent progression of the slip and undergo surgical stabilization at the time of availability of the surgical team.

MALIGNANCY

Although extremely rare as a cause of limp in childhood, malignancy should be considered whenever a clearly identifiable cause is not determined. Radiographs of the region of concern should be inspected for permeative changes, periosteal elevations, and marrow replacement or lucencies. Laboratory studies should be reviewed for subtle elevations of the inflammatory indices or alterations of the hematopoietic elements to include red cells, white cells, and platelets. An automated white blood cell differential should not be trusted under circumstances of increased clinical suspicion, as blast cells may be mistakenly identified as atypical lymphocytes. Rather, a manual differential should be requested.

Acute lymphoblastic leukemia (ALL) (Chapter 449) is the most common childhood malignancy, with a peak incidence at age 4 years (range 3 to 9 years). One study found that 22% of children with ALL had bone pain.⁴ Other forms of malignancy that may be seen in childhood or adolescence include Ewing’s sarcoma and osteogenic sarcoma (Chapters 453 and 454). When clinical suspicion exists of these diagnoses, sub-specialty referral should be made. Oncologists will perform a biopsy to obtain histological confirmation of the diagnosis.⁵

SUMMARY

There are many causes of gait abnormality in childhood. The most worrisome causes, including trauma, infection, and malignancy, should be excluded by a diligent, timely workup including a careful history and physical examination, appropriate radiographic and laboratory studies, and prompt subspecialty referral when necessary.

REFERENCES

See references on DVD.

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