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Soft Tissue Abscess

KEY FACTS Terminology Abscess: Walled-off liquefied collection of necrotic tissue, inflammatory cells, & bacteria Imaging Most commonly affects single site: Typical lymph node location vs. other subcutaneous or intramuscular focus Septic emboli can cause multifocal collections Ultrasound: Excellent for detecting superficial collections & defining drainability Thick-walled centrally avascular collection with surrounding edema ± hyperemia Swirling internal debris upon compression MR: Clearly defines deep extent, evaluates adjacent bone/cartilage/joint, & helps…

Osteomyelitis

KEY FACTS Imaging Long bone metaphyses 70% (femur > tibia > humerus), short bones 6%, pelvis 5%, spine 2% Metaphysis or equivalent > epiphysis, diaphysis Multifocal in 10% overall but 22% in neonates Absence of radiographic bone findings does not exclude early osteomyelitis Earliest finding: Soft tissue swelling next to bone Bone destruction, periosteal reaction by 7-14 days MR: Best advanced imaging choice if diagnosis unclear…

Septic Arthritis

KEY FACTS Terminology Septic arthritis: Microbial (typically bacterial) invasion of joint leading to inflammation & purulence Imaging US: Highly sensitive for fluid distending joint capsule Complexity & volume do not predict/exclude infection MR: Nonspecific joint fluid with synovial thickening Findings favoring septic arthritis over transient synovitis – Presence of marrow &/or soft tissue edema – ↓ enhancement/perfusion of articular epiphysis Top Differential Diagnoses Transient synovitis, juvenile…

Transient Synovitis

KEY FACTS Terminology Idiopathic self-limited inflammation of pediatric hip Synonyms: Toxic synovitis You’re Reading a Preview Become a Clinical Tree membership for Full access and enjoy Unlimited articles Become membership If you are a member. Log in here

Stress Injuries of Bone

KEY FACTS Terminology Fatigue fracture: Fracture due to abnormal stresses applied (over time) to normal bone Insufficiency fracture: Fracture due to normal stresses applied to abnormal bone Stress response/reaction: Result of stresses upon bone prior to development of macroscopic fracture Chronic physeal stress injury: Repetitive stress to growth plate interrupts normal endochondral ossification Imaging Stress injury of formed bone Periosteal new bone ± transversely oriented lucent…

Other Fractures of Child Abuse

KEY FACTS Imaging High specificity for child abuse Classic metaphyseal lesions, posterior rib fractures Scapular fractures – Transverse or oblique fractures of mid acromion process most common – Acromion tip fracture mimics ossification center Sternal fractures – Linear lucency or buckling of anterior cortex – Widened sternal synchondrosis or malalignment of sternal segments Spinous process fractures – Cartilage/bone avulsion at interspinous ligamentous attachment due to hyperflexion…

Child Abuse, Metaphyseal Fractures

KEY FACTS Terminology Classic metaphyseal lesion (CML) or metaphyseal corner fracture: Transverse fracture of subphyseal metaphysis that undercuts subperiosteal bone collar peripherally Fracture of infants with high specificity for child abuse Imaging Most common at distal femur, proximal & distal tibia Radiographic appearance Acute fractures subtle, often difficult to identify initially – Triangular fragment at metaphyseal corner when x-ray beam perpendicular to bone long axis –…

Incomplete Fractures

KEY FACTS Terminology Incomplete fracture: Macroscopic fracture line does not traverse entire bony diameter Pediatric bones more elastic than adult bones Greater propensity to bow or bend before breaking Buckle fracture: Focal outward bulge of cortex (without frank interruption) on compression side; cortex usually intact on tension side Plastic deformation: Smooth but accentuated bending of shaft without visible fracture line Greenstick fracture: Discrete fracture line on…

Apophyseal Injuries

KEY FACTS Terminology Apophysis: Nonarticular secondary center of ossification that serves as attachment site for muscle or tendon Acute injury: Avulsion fracture of osseous &/or cartilaginous apophysis through subjacent physis Chronic injury: Repetitive submaximal tensile forces (avulsive microtrauma) exceed rate of repair, leading to local growth plate disturbance (± symptoms) Imaging Acute injury: Displaced apophyseal ossification center Chronic injury: Mild soft tissue swelling with ossific irregularity…