Musculoskeletal Imaging

Fracture

a break in continuity of bone, cartilage or both, which is also associated with soft tissue injury.

Fracture, Table 1. Terminology of fractures.

Transchondral fractureInvolves entire thickness of cartilage down to subchondral bone
Chondral fractureInvolves cartilage alone
Osteochondral fractureInvolves cartilage and subjacent bone
Closed (simple) fractureSkin is intact
Open fractureSkin is broken
Complete fractureInvolves the entire circumference (tubular bone) or both cortical surfaces (flat bone) of a bone
Incomplete fractureBreak in the cortex does not extend completely through the bone
Comminuted fractureInvolves more than two fracture fragments
Butterfly fragmentWedge-shaped fracture fragment arising from the shaft of a long bone
Segmental fractureFracture lines isolate a segment of the shaft of the tubular bone
Avulsion fractureOccurs when a bone fragment is pulled from the parent bone by a tendon or ligament
Impaction fractureOccurs when one fragment of bone is driven into an apposing fragment
Depression fractureAn impaction fracture that results when the forces occur between a hard bone surface and a softer surface
Compression fractureAn impaction fracture involving vertebral bodies
Pathologic fractureOccurs at a site of previous abnormality, often by means of a stress that would not normally cause fracture
Bone bruiseTrabecular microfracture
Stress fractureOccurs after repeated cyclic loading
Osteochondritis dissecansFragmentation and possible separation of joint surface
Greenstick fracturePerforates cortex and ramifies in medullary bone
Buckling fractureCauses buckling of cortex
Bowing fracturePlastic response to longitudinal compression
Fatigue fractureResults from abnormal stress on a bone with normal elasticity
Insufficiency fractureResults from normal stress on a bone with deficient elasticity

Many of the fractures listed in Table 1 are discussed under their specific names.

Fracture Alignment and Position

The alignment of a fracture refers to the longitudinal relationship of one fracture fragment to another (that is, the presence or absence of angulation). Fracture position describes the relationship of the fracture fragments in comparison to the normal orientation in other ways than by angulation. Deviation from anatomic position is called displacement. Apposition denotes the degree of bone contact at the fracture site.

Fracture Healing

Under most circumstances, bone healing occurs after fracture, leading to bone union. Sometimes the process is slowed (delayed union) or fails completely (nonunion). After nonunion, a typical pseudarthrosis or a fibrous union develops. Malunion may also occur, with the fragments becoming healed in an improper position.

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