Classification of Muscle Injuries on Ultrasound: Applicability of BAMIC and Related Systems
Basic Clinical Grading
Acute muscle injury is clinically divided into grade 1 (no appreciable fiber disruption), grade 2 (partial tear or moderate fiber disruption with decreased strength), and grade 3 (complete fiber disruption). This grading is the baseline framework for correlating ultrasound findings with clinical presentation.
Ultrasound Semiology
On sonography, acute muscle contusion and hemorrhage appear hyperechoic. Excessive and intense muscle activity on acute scanning may produce focal or diffuse hyperechogenicity due to transient edema—the so-called delayed-onset muscle soreness (DOMS). Muscle tears manifest as an abnormal hypoechoic or mixed echogenicity area with architectural distortion or muscle defect.
Terminologically: contusion is direct blunt compressive trauma without detectable tear; tear is disruption of muscle fiber continuity, typically at the myofascial or musculotendinous junction; DOMS is reversible structural damage at the cellular level resulting from unaccustomed heavy repetitive loading, muscle edema without detectable tear.
Mechanism of Tear
Tears are classified as extrinsic tear (direct external trauma, often rectus femoris) and intrinsic tear (forceful contraction of a lengthened muscle, typically localized at the myofascial junction)—the latter being the most common type of muscle injury.
BAMIC and Other Systems (MRI-Oriented)
In the fragments, BAMIC and Olympic Park Grading System are characterized directly as MRI-based. BAMIC thresholds are presented in relation to MRI signal (high STIR signal), which should be considered when attempting application to ultrasound.
| Grade (BAMIC, 2014) | Criteria (by MRI) |
|---|---|
| 0a | Focal muscle pain with normal MRI |
| 0b | Generalized pain; MRI normal or muscle edema |
| 1 | < 10% cross-sectional area or longitudinal extent < 5 cm with fiber tear < 1 cm |
| 2 | 10-50% cross-sectional area or longitudinal extent 5-15 cm with fiber tear < 5 cm |
| 3 | > 50% cross-sectional area or longitudinal extent > 15 cm with fiber tear > 5 cm |
| 4 | Complete tear |
Grades 1-3 in BAMIC are further subclassified by location: a) myofascial, b) musculotendinous/muscle, c) tendinous.
Olympic Park Grading System (Gastrocnemius Muscle, 2018)
| Grade | Feature |
|---|---|
| 0 | Muscle edema adjacent to intact connective tissue (tendon/aponeurosis/epimysium) |
| 1 | Detachment of myofibrils from connective tissue |
| 2 | Signal change in connective tissue, delamination, or partial tear |
| 3 | Failure/retraction of connective tissue |
Regarding the ISMuLT system, no data are provided in the fragments. [clarification needed]
Frequently asked questions
What ultrasound signs differentiate contusion from tear?
Acute contusion and hemorrhage are hyperechoic, without detectable tear. Tear is a hypoechoic or mixed echogenicity area with architectural distortion or muscle defect.
Can BAMIC thresholds be directly applied on ultrasound?
BAMIC (2014) in the fragments is characterized as an MRI-oriented system with criteria based on STIR signal, so direct transfer of thresholds to sonography is limited.
How does DOMS appear on ultrasound?
Focal or diffuse hyperechogenicity due to transient muscle edema on acute scanning; no detectable tear. This is reversible structural damage at the cellular level.
Where is intrinsic tear most commonly localized?
Typically at the myofascial junction; intrinsic tear (forceful contraction of lengthened muscle) is the most common type of muscle injury.
Is there ISMuLT data in the sources?
No information on ISMuLT system is provided in the fragments [clarification needed]. BAMIC (2014) and Olympic Park Grading System (2018) are described.