Antalgic Gait in Children

Etiology

The etiology of antalgic gait can be divided into traumatic and non-traumatic categories. Traumatic etiologies are typically contusions, strains, and overuse injuries, while non-traumatic etiologies include infectious, oncologic, and bone processes.

Traumatic Etiologies

In most cases, there is a history of trauma resulting in symptoms that prompt a caregiver to seek evaluation by a healthcare provider. The management of these children depends on physical examination and imaging findings. A commonly encountered cause of an antalgic gait in older infants and young children is the toddler’s fracture. These are spiral fractures of the tibia that may follow minimal trauma, and sometimes there may be no trauma history. The most common finding in these children is a refusal to bear weight; the physical examination may be normal, or there may be pain elicited over the distal tibia when palpated. Plain radiographs of the affected extremity may show the fracture, but in some 40% of children, these radiographs may be normal.[5] Consultation with a pediatric orthopedist may be warranted depending on the degree of injury.

A practitioner must always consider non-accidental trauma in any pediatric patient of any age, but especially in infants, non-ambulatory children with fractures or injuries that either a child is not developmentally capable of causing or that do not fit with the given history. There is a low threshold for a thorough evaluation of non-accidental trauma if any of these are present. Additional "red flags" include a delay in seeking care, other signs of injury such as patterned bruising or bruising in unusual locations, such as behind the ears or on the back, and other fractures, particularly fractures in various stages of healing. Fractures that require a significant amount of force, such as scapular fractures, or unique fracture types, such as corner fractures and bucket-handle fractures, should raise suspicion for non-accidental trauma. An appropriate evaluation (skeletal survey, laboratory testing, and possible neuroimaging), prompt social services consultation, and/or child protective services notification is indicated. If available, the practitioner should also consult with a child abuse pediatrician. The American Academy of Pediatrics has published guidelines on the radiographic evaluation of a child with suspected non-accidental trauma. This includes a proper skeletal survey in children younger than 2 years of age (this imaging test should be performed on children ages 2 to 5 years on a case-specific basis) with a repeat survey done in 10 days to evaluate for healing occult fractures that may not be evident on the initial surgery. In children older than 5 years of age, skeletal surveys are of limited value.

Non-Traumatic Etiologies

Infectious Etiologies

The presence of fever and antalgic gait should raise suspicion for an infectious cause. Viral and bacterial agents can produce symptoms. The most frequent bacterial agents are Staphylococcus aureus and Streptococcus pyogenes. There may be associated with soft tissue infections, such as cellulitis or an abscess, although this is less common. Involved locations may be in the bones of an extremity, the vertebrae, or discs of the spine. Infections can follow trivial trauma, puncture wounds, or animal bites.

Transient Synovitis: Commonly seen in young school-age children, this condition mimics osteomyelitis or septic arthritis, producing pain and sometimes a refusal to ambulate. Fever may or may not be present. Also known as “toxic synovitis,” this condition follows a viral infection and is inflammatory. It is self-limited.

Osteomyelitis: Typically, osteomyelitis is acquired through the hematogenous spread and most often involves long bones. Infants with osteomyelitis may present with fever, and fussiness or pain may be elicited with a movement of the involved extremity. Older children will present with fever and painful gait. There may be reproducible pain to palpation or pain with a range of motion of the involved extremity. Young children have a predisposition to have concomitant septic arthritis with osteomyelitis due to boney vascular anatomy; this becomes less common as children age. While S. aureus is the most common etiologic agent, there has been a recent increase in infections due to Kingella kingae, which also is associated with the development of a Brodie abscess.[6]

Myositis: Viral myositis is a common cause of antalgic gait in pediatric patients. Influenza is the most predominant virus in these children and is often bilateral. While any gram-positive bacterial species can cause pyomyositis, staphylococcal species predominate. This is often focal and may have associated osteomyelitis.[7]

Discitis/epidural abscess: Often progressing on a more indolent course, discitis or epidural abscess presents a diagnostic challenge, as children may not localize pain to the back, and physical examination findings may be limited. Older children may localize pain to the back (especially the lumbar area), and infants may become irritable when placed in a sitting position and may prefer to be prone.[8] Back pain in young children is not a common symptom and should alert the clinician to a more serious underlying cause other than musculoskeletal pain. 

Bone Abnormalities

Two common etiologies of antalgic gait in pediatric patients are slipped capital femoral epiphysis (SCFE) and Legg-Calve-Perthes disease (LCP).

SCFE: This condition, in which the capital femoral epiphysis is displaced from the femoral neck through the epiphysis, is most often encountered in adolescent patients, particularly those who are obese.[9] Males are more commonly affected. The most frequent presenting symptoms are progressively worsening hip pain and difficulty ambulating without fever. However, up to 15% of patients will present with referred pain to the ipsilateral knee.[10] SCFE can also be associated with chronic medical conditions, such as hypothyroidism and pituitary disorders. Physical examination of these patients reveals an afebrile child's limited range of motion of the hip and tenderness. 

LCP: Often seen in school-age children with a peak incidence of 5 to 7 years of age and has a male preference.[11] Most cases are unilateral, but up to 20% can be bilateral. Symptoms include a gradual onset of hip pain and difficulty ambulating. This condition can be preceded by trauma (often trivial) or associated with chronic corticosteroid use. The physical examination uncovers a limited range of motion of the hip, but pain may not be a prominent symptom.

Oncologic Etiologies

Benign and malignant tumors can present with ambulation difficulties in children.

Osteoid Osteoma: This benign lesion is most commonly encountered in the teenage population.[12] The classic history of this lesion is pa ain at night that is relieved by non-steroidal anti-inflammatory medications.

Osteosarcoma and Ewing sarcoma: These are the two most common malignant bone lesions in the pediatric population. They most often are found in the distal tibia. Progressively worsening pain is the usual symptom and may not respond to anti-inflammatory medications.

Leukemia: Almost half of the pediatric populations diagnosed with leukemia experience pain that may impact ambulation. There are often systemic complaints such as fever, pallor, and easy bruising.

Rheumatologic Etiologies

While not common in the pediatric population, rheumatology causes of antalgic gait do occur, primarily in children with juvenile rheumatoid arthritis (JRA) and lupus. Often the child will have an existing diagnosis of rheumatologic disease, but the clinician should keep this possibility in mind, especially in older children, for example, teenagers.

Other Etiologies

Children with appendicitis or testicular torsion may present with an antalgic gait. It is essential to perform a thorough physical examination, including the abdomen and genital areas, to exclude these processes.

Epidemiology

Some causes of pediatric antalgic gait have an age-wise predilection. The common causes in adolescents and teenagers include SCFE and osteoid osteoma, whereas the causes in younger children include LCP and transient synovitis.

Pathophysiology

Several factors should be considered regarding pediatric bone anatomy and physiology. Pediatric bones are unlike adult bones. The epiphysis is the growth plate of the bone, is open, closing with time, and is a common fracture location. During development, the epiphysis is weaker than surrounding ligaments, which results in vulnerability to fracture. The porous nature of pediatric bones allows for unique fracture patterns, such as Greenstick fractures and buckle (or torus) fractures and bowing deformities in response to injury.

History and Physical

A thorough history and physical examination are essential first steps in evaluating a child with an antalgic gait. The clinician must ask if a child has reached specific developmental milestones, particularly motor milestones such as crawling or cruising in infants and toddlers or the ability to climb in toddlers and school-age children. This is crucial when the etiology of the child’s pain is due to a fracture. Underlying medical conditions such as osteogenesis imperfect can result in significant injuries even in the setting of apparently trivial trauma and must be taken into account in approaching these children.

The physical examination of the child needs to be developmentally appropriate. Pediatric vital signs vary with age. Often it is helpful to simply observe the child as they interact with their caregiver before performing a physical examination. Examining the non-affected extremity first, followed by gradually examining the area in question, is a useful technique to ease stranger anxiety. Note for any signs of edema, erythema, deformity, or diminished range of motion. Pay close attention to the hips (particularly in infants) and perform a thorough range of motion examination, looking for any signs of distress. If developmentally appropriate, having the child attempt to ambulate to the parents may help determine the location of the pain as one observes the child’s gait pattern.

Evaluation

History and physical examination will dictate whether laboratory studies, imaging, or both are indicated. Most children do not warrant testing. The presence of fever, prolonged symptoms, toxic appearance, or concerning symptoms such as weight loss, easy bruising, joint pain are reasons to initiate a workup.

Laboratory Studies

When an infectious or oncologic source is suspected, there are basic hematologic tests that can be useful. Complete blood count (CBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) tests are recommended if an infectious etiology is suspected; a blood culture should also be obtained.[13] It is also recommended that a chemistry panel (including liver function tests) be obtained to help identify if other organ systems are involved, which is not uncommon in children with both infectious and oncologic processes. If an oncologic process is suspected, then lactate dehydrogenase and uric acid tests may be helpful. There are published risk stratification guidelines that help a clinician differentiate between transient synovitis and osteomyelitis based on clinical examination and laboratory results.[14][15]

Imaging

Exposure to ionizing radiation is always a concern in the pediatric population. There are numerous guidelines and expert consensus resources that have endorsed the “as low as reasonably achievable” concept. There are several common imaging modalities can that be employed.

Plain Radiography: Easily available and with low ionizing radiation exposure, this is the first-line imaging modality in children with an antalgic gait. Selected imaging of the involved extremity is recommended. The tibia is cited as the bone that is most likely to have pathology on plain imaging.[16] Plain radiography is useful in detecting trauma, SCFE, and LCP disease, and it is employed as a first-line imaging modality in suspected cases of osteomyelitis or joint infection, primarily to exclude other pathology. A proper imaging technique is essential to maximize the effectiveness of the modality as pediatric fractures can be subtle. This includes at least 2 views of an involved extremity or a full pelvis view in evaluating hip pain, not a hemipelvis view.[17] It is also helpful to provide as many relevant historical and physical examination findings as possible to the interpreting radiologist. Ewing sarcoma has a classic “onion skinning” pattern and osteosarcoma a “sunburst” pattern on plain radiography. Both lesions may show poorly defined margins.

Computed Tomography (CT): This modality can be useful in detecting subtle fractures when plain radiography is indeterminate, making it useful in the setting of trauma. CT is not useful for the evaluation of infectious processes. While widely available in most clinical settings, CT scanning does employ ionizing radiation. Contrast is not employed in trauma settings.

Magnetic Resonance Imaging (MRI): The advantage of MRI is the lack of ionizing radiation and superb image resolution. This modality is excellent for the evaluation of infectious or oncologic processes. Images are usually obtained with and without contrast. There are several disadvantages of MRI, including lack of availability, cost, and the time required to obtain a study, which often requires sedation in younger children.[18]

Ultrasound (US): This modality is useful for the detection of fractures [19] and has the advantage of availability, lack of ionizing radiation, and does not require contrast. However, US cannot distinguish the causes of hip effusion and can be misleading if not performed adequately or performed in an untimely manner.[20]

Treatment / Management

Fractures

Most children with simple, non-displaced fractures can be treated with appropriate splinting, followed by casting for several weeks. Surgical treatment for fractures depends on the degree of injury and the age of the child. Open fractures are often managed in the operating room with vigorous irrigation, cleaning, and exploration, followed by reduction if indicated and casting. Consultation with pediatric orthopedics is recommended, especially if there is doubt regarding the appropriate treatment and disposition of the child.

SCFE/LCP Disease

Emergency pediatric orthopedic consultation is indicated in these children. Children with SCFE require operative repair, albeit not necessarily in cases of mild slippage; these children should be made non-weight bearing and have very close follow-up; prophylactic pinning is usually done to prevent worsening slippage. Management for children with LCP disease ranges from immobilization to operative intervention. This will depend on the degree of symptoms and radiographic findings.

Osteomyelitis/Myositis/Discitis

Children with these conditions are admitted for appropriate intravenous antibiotics. Consultation with pediatric infectious disease and/or pediatric orthopedics is recommended before antibiotic initiation. If there is an associated abscess, operative management is required.

Oncologic Etiologies

Oncologic etiologies warrant admission for further evaluation and management after consultation with pediatric oncology and staging of the lesion.

Rheumatologic

The disposition of the child depends on the degree of pain and the child’s response to analgesia. Consultation with pediatric rheumatology is recommended.

Differential Diagnosis

The differential diagnosis of the child with an antalgic gait is broad. Consideration must be given to traumatic, infectious, rheumatologic, and oncologic etiologies. A thorough history and physical examination, accompanied by appropriate laboratory testing and imaging utilization will help narrow the diagnosis.

• Appendicitis
• Contusions
• Discitis
• Ewing sarcoma
• Fractures
• Juvenile rheumatoid arthritis
• LCP disease
• Leukemia
• Myositis
• Non-accidental trauma
• Osteomyelitis
• Osteosarcoma
• SCFE
• Septic arthritis
• Septic joint
• Transient synovitis

Prognosis

Most children with fractures do well after appropriate treatment, as do children with an infectious cause of their pain. The prognosis of children with an oncologic etiology depends on the type and stage of the malignancy, which will impact management choices. Children with a rheumatologic cause of their pain are maintained on appropriate medications, based on their diagnosis, for example, JRA versus lupus.

Complications

Morbidity and mortality depend on the etiology of the child’s symptoms. Appropriate and timely care will significantly impact the development of complications. Osteomyelitis can progress to bone abscess formation, sepsis and even result in death. Children with septic joints can develop gait disturbances that are permanent, impacting the quality of life. Oncologic processes necessitate treatment with chemotherapeutic agents, surgical procedures, or both. This process involves multiple hospitalizations, and children receiving such agents are at risk for significant bacterial and viral infections. Rheumatologic etiologies can produce a significant impact on activities of daily living; the treatment agents used for these children also may place them at risk for significant infections.