Pediatric Musculoskeletal Infections, Inflammatory Disorders, and Nonaccidental Trauma

Amy L. McIntosh, MD

Dr. McIntosh or an immediate family member is a member of a speakers’ bureau or has made paid presentations on behalf of Globus Medical.

ABSTRACT

Recently, musculoskeletal infections in children and adolescents have increased in incidence and severity. Bacterial behavior likely contributes to this rising disease burden. The variability of clinical presentations makes the diagnosis of musculoskeletal infections a challenge. Adhering to strict diagnostic and treatment algorithms while utilizing new classifications and scoring systems to determine the severity of illness can predict patient outcomes and improve patient care and resource utilization. The most common inflammatory conditions that affect pediatric patients are poststreptococcal reactive arthritis, juvenile idiopathic arthritis, and Lyme disease-associated arthritis. Treatments are specific to each disease, so accurate diagnosis is important. Fractures related to nonaccidental trauma are common, especially in children younger than 12 months. It is the duty of the orthopaedic surgeon to recognize and report suspected nonaccidental trauma to social services and local child protective service representatives.

Keywords: inflammatory arthritis; musculoskeletal infection; nonaccidental trauma

Introduction

Musculoskeletal infections in children generally occur during the first decade of life, and one-half of all cases present in children younger than 5 years. The majority of cases are caused by Staphylococcus species, followed by Streptococcus species. Early recognition and treatment by a coordinated multidisciplinary team that utilizes severity of illness (SOI) scores and disease classification systems can optimize resource utilization and improve patient outcomes.

Nonaccidental fractures resulting from the physical abuse of a child is also common and is a major public health concern. Traumatic injuries account for 18% of child abuse presentations, and 1,680 children die annually from abuse.¹ The physical abuse of children, especially those younger than year, frequently manifests as a fracture, which is second only to bruising as the most common sign of physical abuse.² Up to 20% of burns are nonaccidental in the pediatric population.³

Pediatric Musculoskeletal Infections

In recent decades, musculoskeletal infection (MSKI) have increased in incidence and severity.⁴ However, substantial differences exist in the regional manifestations of MSKI. There is a higher incidence of MSKI in regions that have temperate climates (southern United States) compared with northern regions of the United States.⁵ There is also seasonal variation with MSKI. Summer is the most common season for MSKI occurrence.⁶

Diagnosis

Traditionally, musculoskeletal infections were classified on the type of tissue infection: superficial abscess, septic joint, osteomyelitis, and deep abscess/pyomyositis. These conditions can occur in isolation, but MSKIs often occur in combination. A failure to recognize a complex MSKI that involves more than one tissue type and/or anatomic location can lead to treatment delays, prolonged hospitalizations, and increased risk for complications.⁵ For these reasons, a novel stratification system has been proposed for MSKI based on the degree of system involvement, regardless of the type of tissue infection or causative bacteria.⁷ This three-tiered classification system is based on the severity of the infection and the degree of dissemination. Pediatric MSKI patients should be classified into three groups: (1) inflammation, (2) local infection, or (3) disseminated infection (Table 1). The MSKI is classified as inflammation if all of the following were
true: negative local culture, negative blood culture, and criteria for local or disseminated infection are not met. The MSKI is classified as a local infection, if imaging was characteristic of infection in one anatomic site or a single positive blood culture. Disseminated infection is defined as the presence of multiple positive blood cultures, positive tissue culture from different anatomic sites, imaging characteristic of infection in multiple anatomic sites, and/or thromboembolic disease.⁷ The patients with disseminated infections are statistically more likely to undergo surgical débridement, have longer hospital stays, be admitted to the intensive care unit (ICU), and require a longer duration of antibiotic treatment. They also demonstrate higher C-reactive protein (CRP) levels, erythrocyte sedimentation rates (ESRs), white blood cell (WBC) counts, and temperature peaks.⁷ Deep vein thrombosis (DVT) and pulmonary embolism (PE) are more likely to develop in patients with disseminated infections.⁸ It is recommended that children who present with disseminated infection and are admitted to the ICU should undergo ultrasonograpic screening to assess for DVT.⁸

Table 1 Infection Severity Classification

	Definition	Example
Inflammation	All of the following must be true: Negative blood culture Negative local culture The criteria for local or disseminated infection are not met	Transient synovitis
Local infection	One of the following must be true: Osteomyelitis or pyomyositis in one anatomic site Local culture positive AND/OR fluid/tissue consistent with infection One positive blood culture The criteria for disseminated infection are not met	Isolated distal femoral osteomyelitis with no subperiosteal abscess Isolated septic hip
Disseminated infection	Two or more anatomic sites, at least one of the following must be true: Imaging diagnostic for osteomyelitis or pyomyositis Local culture positive AND/OR fluid/tissue consistent with infection Two or more positive blood cultures Thromboembolic disease	Septic hip with surrounding muscle pyomyositis Distal fibular osteomyelitis with subperiosteal abscess

Pediatric patients with MSKI present with fever and focal tenderness, warmth, or swelling near the ends of long bones and decreasing ability to bear weight or use the extremity. Range of motion of the adjacent joint may be limited because of local inflammation or due to contiguous septic arthritis. All patients should undergo a through physical examination as well as appropriate laboratory tests and imaging studies. The routine laboratory tests to be performed are blood culture, complete blood count (CBC) with differential, ESR, and CRP. Plain radiographs of the involved bone are often negative initially, but they may demonstrate deep soft-tissue swelling when inspected carefully for this finding. Bone destruction is not observed on radiographs until an infection is present for at least 7 to 14 days. MRI is a key component to the workup of patients in whom an MSKI is suspected. MRI is an accurate and reliable modality to determine the anatomic and spatial extent of infection, provides a more complete understanding of the primary and contiguous tissues involved in the infection, and helps determine all foci of infection that require débridement and/or drainage. Disadvantages associated with MRI include its cost, the need for sedation in most children, and the logistics of obtaining the study in a timely fashion in busy pediatric medical centers. Ultrasonography is readily available and inexpensive. However, it is limited in its capability to identify deep infections of the muscle and bone (pyomyositis and osteomyelitis). In a recent study of pediatric patients evaluated in an emergency department to rule out septic hip arthritis, pelvis pyomyositis was twice as common as an isolated septic hip arthritis.⁹ Another study reported that contiguous osteomyelitis was observed 68% of the time in patients who have septic hip arthritis.¹⁰ The MRI can also be used to direct the approach for a joint aspiration. If the MRI demonstrates pelvic pyomyositis that affects the adductor musculature, then the joint aspiration should be approached
anteriorly instead of from a medial approach to avoid contamination of the hip joint aspiration from the contiguous pyomyositis.⁵

For these and other reasons, MRI is the preferred imaging modality for the diagnosis of MSKI. At the institution of the author of this chapter, a noncontrast fast spin-echo sequence protocol is obtained from nonsedated pediatric patients with suspected MSKI in less than 30 minutes. This MRI protocol includes a coronal T1-weighted short tau inversion recovery MRI and an axial T2-weighted MRI. Both sequences provide the orthopaedic surgeon enough detail to make an accurate diagnosis as well as identify any foci of MSKI that are amendable to surgical or interventional radiologic débridement and/or drainage.⁵

Antibiotic Treatment

The timing of appropriate empiric antibiotic administration should balance the priorities of identifying the causative bacteria and avoiding unnecessary delay in antibiotic administration in children who may be demonstrating signs of sepsis. Antibiotics should not be administered until a blood culture is obtained.¹¹ If a specimen can be obtained from the specific site of infection in a timely manner, then antibiotics should be withheld until after that culture is obtained. Whenever clinical concern exists about the potential for evolving sepsis, which is discernible by the presence of fever, the ill appearance of the child, and hemodynamic changes, antibiotics should be administered regardless of the timing of anticipated advanced imaging or surgery. Empiric antibiotics should be selected on the basis of the most prevalent bacteria responsible for MSKI within the local community.¹² Currently, most children are treated effectively with a much shorter course of intravenous antibiotics, followed by 3 to 4 weeks of targeted oral therapy. Identifying oral antibiotics with good bioavailability to which the bacteria are susceptible offers flexibility in treatment options for the administration route. Sequential parenteral-to-oral antibiotic therapy is considered safe and effective and should be used in the absence of contraindications such as malabsorption, noncompliance, or antibiotic resistance of the causative organism that requires intravenous antibiotic therapy.

Only gold members can continue reading. Log In or Register to continue