Muscle Injury

Muscle Injury

KEY FACTS

Terminology

• Contusion : Direct blunt compressive trauma to muscle without definable tear
• Tear : Discontinuity of muscle fibers typically at myofascial or myotendinous junction
• Hernia : Focal protrusion of part of muscle through epimysium
• DOMS : Overuse → muscle edema without definable tear
- Pain peaking 1-3 days after overuse

Imaging

• Muscle contusion
- Ill-defined hyperechogenicity of muscle or muscles
- No discrete muscle tear (fiber discontinuity)
• Muscle tear
• Muscle hematoma
- Typically associated with grade 2 or 3 tears
- Appearance varies with duration of hematoma, severity, and location
• DOMS
- Affected muscle may be normal or diffusely hyperechoic due to diffuse muscle edema
• Muscle hernia
- Focal protrusion of muscle through epimysium
- Accentuated by muscle contraction or exercise

Clinical Issues

• Most muscle injuries improve with conservative treatment
- Serial US examination not shown to be useful for guiding speed of rehabilitation
• Functional recovery precedes structural recovery

Longitudinal US of an unaffected leg shows normal sharp angulation of the myotendinous and myofascial junction at the distal end of the medial belly of gastrocnemius muscle. This is the most common site of calf muscle tears.

Longitudinal US of an unaffected leg shows normal sharp angulation of the myotendinous and myofascial junction at the distal end of the medial belly of gastrocnemius muscle. This is the most common site of calf muscle tears.

Clinical photograph shows a patient with a recent calf muscle tear. There is moderate calf swelling and bruising with more intense, gravity-related bruising at the ankle region .

Clinical photograph shows a patient with a recent calf muscle tear. There is moderate calf swelling and bruising with more intense, gravity-related bruising at the ankle region .

Longitudinal US of a symptomatic leg shows a myofascial junction tear at the distal end of the medial belly of gastrocnemius muscle. The medium-severity tear is filled with fluid. No muscle retraction is present.

Longitudinal US of a symptomatic leg shows a myofascial junction tear at the distal end of the medial belly of gastrocnemius muscle. The medium-severity tear is filled with fluid. No muscle retraction is present.

Transverse US of the same area shows the moderate-severity myofascial tear . Overall, ~ 15% of the cross-sectional area (CSA) of the muscle insertion is torn. The plantaris tendon is normal.

Transverse US of the same area shows the moderate-severity myofascial tear . Overall, ~ 15% of the cross-sectional area (CSA) of the muscle insertion is torn. The plantaris tendon is normal.

TERMINOLOGY

Synonyms

• Muscle tear, muscle contusion, muscle hematoma, muscle strain, “pulled muscle,” “tennis leg,” delayed-onset muscle soreness (DOMS), muscle hernia

Definitions

• Tear: Discontinuity of muscle fibers typically at myofascial or myotendinous junction
• Contusion: Direct blunt compressive trauma to muscle without definable tear
• Hernia: Focal protrusion of part of muscle through epimysium
• DOMS: Overuse causing muscle edema without definable tear
- Pain peaking 1-3 days after overuse

IMAGING

General Features

• Best diagnostic clue
- Muscle tear; hypoechoic area within muscle or at myotendinous junction
• Location
- Usually affects lower limb muscles (gastrocnemius > rectus femoris, adductor longus, biceps femoris, semimembranous, semitendinosus, and soleus muscles)
- Typically at myofascial junction within muscle or myotendinous junction
  - – These are weak areas at interface between tissues of different elastic property
• Morphology
- Muscle fiber discontinuity with local hemorrhage and edema

MR Findings

• T1WI
• T2WI
- Muscle tear
- DOMS
  - – Diffuse homogeneous hyperintensity
• T2* GRE
- Susceptibility artifact due to hemorrhage

Ultrasonographic Findings

• Muscle contusion
• Muscle tear
• Healing muscle tear
• Muscle hematoma
• DOMS
- Affected muscle may be normal or, if severe, diffusely hyperechoic due to diffuse muscle edema
- No discernible muscle tear
• Muscle hernia
- Focal protrusion of muscle fibers through epimysial fascial defect
- Accentuated by muscle contraction or exercise

Imaging Recommendations

• Best imaging tool
- US since most muscle tears are accessible
  - – MR preferable in pelvitrochanteric muscles, adductor or hamstring insertions as less accessible with US
• Protocol advice

Tags: Diagnostic Ultrasound Musculoskeletal

Apr 9, 2020 | Posted by admin in MUSCULOSKELETAL IMAGING | Comments Off

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