Bone and Soft-Tissue Disorders
Cause: direct trauma, usually by blunt object
Site: deep within muscle belly
- injury at point of impact
- NO architectural changes
- feathery appearance of diffuse muscle edema
- increased muscle girth
- deep intramuscular hematoma (with severe trauma resulting in disruption of muscle fibers):
- high SI on T1WI (= T1 shortening of methemoglobin)
- low SI on T2WI ( = T2 shortening of hemosiderin)
- blooming with gradient-echo sequence
Cause: single traumatic event from excessive stretching
Susceptibility factors:
- muscle composed of (fast contracting) type II fibers
- fusiform shape of muscle
- extension across two joints
- superficial location of muscle
- eccentric muscle action
Site: myotendinous junction (= weakest point of musculotendinous unit)
Classification:
- 1° degree = stretch injury (some fiber disruptions)
- no loss of muscle function
Path: interstitial edema + hemorrhage at myotendinous junction with extension into adjacent muscle fibers - feathery appearance of muscle
- no loss of muscle function
- 2° degree = partial tear without retraction
- mild loss of muscle function
- hematoma at myotendinous junction
- perifascial fluid collection
- 3° degree = complete rupture
- complete loss of muscle function
- retracted muscle tendon
- hematoma at myotendinous junction
Cause: forceful unbalanced often eccentric muscle contraction
Path: periosteal stripping with hematoma at tendon attachment site
Site: at tendon insertion
- loss of function, severe tenderness
- waviness + retraction of the torn end of tendon with fragment of bone / cartilage