Osteomyelitis and Beyond
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Osteomyelitis and Beyond R. Paul Guillerman, MD Associate Professor of Radiology Baylor College of Medicine Department of Pediatric Radiology Texas Children’s Hospital Houston, Texas Disclosure of Commercial Interest Neither I or a member of my immediate family have a financial relationship with a commercial organization that may have an interest in the content of this educational activity Objectives Review the characteristic imaging findings of pediatric musculoskeletal infections Focus particularly on MRI and invasive community- acquired Staphylococcus aureus (CA-SA) infections Present the differentiating features of potential mimics of infection Pediatric Osteomyelitis Classic clinical signs of fever, pain, swelling, and decreased mobility present in only a slight majority ↑ wbc count in 30-65% Blood cultures + in 30-75% Organism isolated by tissue biopsy in 50-85% ↑ ESR or fever in 70-90% ↑ CRP in 98% Conventional Approach to Imaging Acute Pediatric Musculoskeletal Infections Obtain bone scan if XR negative Reserve MRI for suspected spinal or pelvic osteomyelitis or lack of treatment response No longer optimal with advent of community-acquired Staphylococcus aureus (CA-SA) Community-Acquired Staphylococcus aureus (CA-SA) Distinctions from traditional Staphylococcus aureus: Community-acquired Affects otherwise healthy, immunocompetent children Can have rapid, invasive course Can be methicillin-resistant (MRSA) or sensitive (MSSA) Surgical debridement and drainage of associated abscesses and effusions is the mainstay of therapy Gadolinium-enhanced MRI is the imaging modality of choice, particularly for detection of early osteomyelitis and associated soft-tissue disease Clinical Spectrum of Invasive CA-SA MSK Infections Osteomyelitis Septic arthritis Pyomyositis Deep abscess Clinical Spectrum of Invasive CA-SA MSK Infections Osteomyelitis Septic arthritis Pyomyositis Deep abscess Infants at higher risk CA-SA MSK Infection T1-W STIR Gad T1-W FS Osteomyelitis with subperiosteal abscess CA-SA MSK Infection Gad T1-W FS Gad T1-W FS Readily breaches musculoskeletal tissue barriers Browne Pediatr Radiol 2008 CA-SA MSK Infection Gad T1-W FS Gad T1-W FS Involvement often multifocal CA-SA MSK Infection Gad T1-W FS Associated with septic thrombophlebitis near osteomyelitis site Browne Pediatr Radiol 2008 CA-SA MSK Infection STIR Septic pulmonary emboli associated with higher mortality Browne Pediatr Radiol 2008 8-year-old with left hip pain, fever, elevated ESR and CRP “Cold” Osteomyelitis Gad T1-W FS Toddler with “normal” bone scan Toddler with “normal” bone scan T1-W Gad T1-W FS Tibial Osteomyelitis with Intra-Osseous Abscess T1-W Gad T1-W FS 5-month-old not moving right arm Epiphyseal and Metaphyseal Osteomyelitis Gad T1-W FS 1-month-old with suspected septic arthritis of the right hip T1-W STIR STIR Epiphyseal Involvement Occult on Pre- Contrast MRI Sequences T1-W STIR Gad T1-W FS STIR Gad T1-W FS Age-Dependence of Osteomyelitis Location Childhood Infancy Marin Curr Prob Diagn Radiol 2004 Growth Cartilage “Osteomyelitis” May relate to septic thrombosis or necrosis of cartilage Applies to the epiphyses and apophyses 7-Week-Old with Multifocal Epimetaphyseal Involvement Dynamic Contrast-Enhanced MRA 7-Week-Old with Multifocal Epimetaphyseal Involvement Delayed Post-Contrast MRI Gad T1-W FS Gad T1-W FS Skeletal Extremity CA-SA Infection in Infants Involves growth cartilage of epiphyses or epiphyseal- equivalents in 50% of cases and exclusively in 25% Occult on non-enhanced MRI sequences in 80% Manifests as hypo-enhancing foci in the growth cartilage on contrast-enhanced MRI sequences Not excluded by the absence of joint effusion Skeletal Extremity CA-SA Infection in Infants Follow-up XR reveals growth disturbances in 80% of those with growth cartilage involvement Gad T1-W FS 17-days-old 3-years-old Browne AJR 2012 Imaging of Pediatric MSK Infections in CA-SA Endemic Areas MRI preferred over bone scan as primary imaging test High incidence (2/3) of extra-osseous complications Abscess, septic thrombophlebitis Preoperative MRI reduces operative time and exposure High incidence (1/2) of “cold” or occult osteomyelitis or chondritis on bone scan, particularly in infants 20-month-old, limping for 3 weeks, afebrile, normal ESR/CRP 20-month-old, limping for 3 weeks, afebrile, normal ESR/CRP T1-W STIR Gad T1-W FS Brodie Abscess Subacute osteomyelitis Central abscess fluid Penumbra of enhancing high T1-W signal granulation tissue Very low T1-W signal sclerotic rim Low T1-W signal peri-lesional edema T1-W Brodie Abscess Subacute osteomyelitis Central abscess fluid Penumbra of enhancing high T1-W signal granulation tissue Very low T1-W signal sclerotic rim Low T1-W signal peri-lesional edema May be afebrile with normal T1-W inflammatory marker levels 13-year-old male with acute CA-SA osteomyelitis STIR T1-W 4 months later… Gad T1-W Gad T1-W Involucrum, Sequestrum, Cloaca Gad T1-W Gad T1-W Chronic Osteomyelitis Persistence of symptoms for > 1 month after appropriate antibiotic therapy, or infection > 1 month after inadequately treated osteomyelitis Sequestrum – necrotic bone fragment Involucrum – thick periosteal new bone Cloaca – draining tract through defect in cortex and involucrum Marin Curr Prob Diag Rad 2004 Indications for Follow-Up MRI of Pediatric MSK Infection Routine follow-up MRI not warranted Only 10-20% of follow-up MRI exams provide information that affects patient management (e.g., invasive procedure, change in antibiotic therapy) Indications include failure to show clinical improvement or persistent CRP elevation 11-month-old non-weight-bearing, elevated CRP; septic hip arthritis or osteomyelitis suspected by ER MD and orthopedist STIR STIR CA-SA Septic Arthritis of the Knee Gad T1-W FS Gad T1-W FS Difficult to localize infection in infants by clinical exam CA-SA Septic Arthritis of the Knee Gad T1-W FS Gad T1-W FS Important to survey large FOV initially Septic Arthritis Most common in hip or knee Staphylococcus or Streptococcus most common Kingella kingae increasingly recognized in young children and associated with milder disease Poor outcome associated with delay in diagnosis Articular cartilage destruction Osteonecrosis Growth deformity Osteomyelitis, abscess, sepsis 8-year-old with left hip pain, elevated wbc count and CRP Septic Arthritis Persisting fever and high CRP after hip drainage and normal left femur biopsy T1-W STIR Gad T1-W FS Acetabular Osteomyelitis and Obturator Pyomyositis T1-W STIR Gad T1-W FS Suspected Septic Arthritis US vs. MRI 2/3 of patients with septic arthritis have adjacent abscess (subperiosteal or intramuscular) or osteomyelitis Reliable predictors needed to guide management – US and immediate joint drainage vs. pre-operative MRI to define drainable fluid collections and bone biopsy site(s) Age > 4 yr, symptom duration > 3 days, fever > 2 days, elevated CRP, elevated ANC, low platelet count, and bacteremia identified as independent predictors 10-year-old fell on left hip, next day developed right hip pain, fever, high CRP Intolerance to sitting, refusal to walk, pain radiating down back of thigh and leg Gad T1-W FS Gad T1-W FS Piriformis Pyomyositis Gad T1-W FS Gad T1-W FS Pyomyositis Increased incidence related to CA-SA emergence Most common of the lower extremity and pelvis CRP and ESR usually elevated, while CK usually normal Preceded by skin penetration (bug bite, laceration) in 50% and by trauma or vigorous activity in 25% Teenager with right hip pain and fever STIR Gad T1-W FS Teenager with right hip pain and fever Gad T1-W FS Crohn Ileitis with Sinus Tract to Iliopsoas Gad T1-W FS Iliopsoas pyomyositis often secondary to GI, GU, or spinal infection Infectious Osteomyelitis Mimics 16-year-old with acne, elevated ESR/CRP, left shoulder pain then right thigh pain T2-W FS Chronic Recurrent Multifocal Osteomyelitis (CRMO) Auto-inflammatory disorder Personal or family history of dermatologic (psoriasis, pustulosis) or gastrointestinal disorders (IBD) common Treated with NSAIDs, TNF inhibitors, bisphosphonates Protracted clinical course with recurrences 15-year-old with Crohn disease, CRMO STIR Most commonly affects the extremity long bones, clavicles, spine, and pelvis Usually multifocal, asymmetric, metachronous CRMO T1-W T2-W FS Gad T1-W FS Lysis, followed by sclerosis and hyperostosis No abscess, fistula or soft tissue mass 4-month-old with forearm swelling, elevated ESR/CRP Gad T1-W FS STIR 4-month-old with forearm swelling, elevated ESR/CRP Caffey Disease 6-year-old with thigh pain T1-W STIR Acute Leukemia T1-W STIR 12-year-old with elbow pain, elevated ESR, CRP, and LDH T1-W STIR Gad T1-W FS Lymphoblastic Lymphoma T1-W STIR Gad T1-W FS 3-year-old with left thigh pain, fever, elevated ESR STIR Gad T1-W FS 3-year-old with left thigh pain, fever, elevated ESR STIR Gad T1-W FS Langerhans Cell Histiocytosis (LCH) STIR Gad T1-W FS Fever and elevated ESR common in LCH, Ewing sarcoma, and non-Hodgkin lymphoma of bone Limping febrile toddler, normal knee XR Tibia/fibula radiograph 3 weeks later Toddler’s Fracture 15-year-old football player with knee pain, elevated ESR T1-W 15-year-old football player with knee pain, elevated ESR STIR Gad T1-W FS Stress Fracture STIR Gad T1-W FS Septic Arthritis Mimics 5-year-old with left hip pain, joint effusion, T 38 C, normal WBC/ESR/CRP 5-year-old with left hip pain, joint effusion, T 38 C, normal WBC/ESR/CRP Jung J Pediatr Ortho 2003 2.9% probability of septic arthritis, presumed transient synovitis Jung J Pediatr Ortho 2003 No need for further imaging or