Muscle oedema,
architectural distortion / rupture of muscle fibres and intra- or intermuscular haemorrhage are relevant changes in muscles that can visualized with high resolution MRI.
A flexible body coil allows to reach a homogenous MR signal.
In some cases it could be helpful to mark the painful area with a capsule.
Proposed MRI protocol:
- Coronal Short-Tau Inversion Recovery (STIR),
slice thickness: 4 mm
- Axial Proton density fat saturated (PD fs),
thickness: 3 mm
- Sagittal Proton density fat saturated (PD fs), slice thickness: 3 mm
- Coronal Proton density fat saturated (PD fs),
slice thickness: 3 mm
- Axial T1 weighted,
slice thickness: 3 mm
Different classification systems as Munich muscle injury classification (Table 1),
British Athletics muscle injury classification (Table 2) and consensus-based classifications organize morphologic patterns concerning their severity.
Validation of these classification systems showed good discrimination in predicting lay-off times.
Table 1.
Munich Muscle Injury Classification.
Type
|
Classification
|
Definition
|
MRI
|
1A
|
Fatigue-induced muscle disorder
|
Circumscribed
longitudinal
increase of
muscle tone
due to overexertion
|
|
1B
|
Delayed-onset
muscle soreness
(DOMS)
|
More generalised
muscle pain
following unaccustomed,
eccentric deceleration
movements
|
|
2A
|
Spine-related
neuromuscular
muscle disorder
|
Circumscribed
longitudinal
increase of
muscle tone due
to functional or
structural spinal/
lumbopelvical disorder
|
|
2B
|
Muscle-related
neuromuscular
muscle disorder
|
Circumscribed area
of increased
muscle tone.
May result from
dysfunctional
neuromuscular control
such as
reciprocal inhibition
|
|
3A
|
Minor
partial
muscle tear
|
Tear with a
maximum
diameter of less
than muscle
fascicle/bundle.
|
- Fibre disruption
- Intramuscular haematoma
|
3B
|
Moderate partial
muscle tear
|
Tear with a diameter
of greater than
a fascicle/bundle
|
- Significant fibre disruption (probably some retraction)
- with fascial injury and intermuscular haematoma
|
4
|
(Sub)total muscle
tear/tendinous
avulsion
|
Tear involving the
subtotal/complete
muscle diameter/
tendinous injury
involving the
bone–tendon junction
|
- Subtotal/complete discontinuity of muscle/tendon (probably wavy tendon and retraction)
- with fascial injury and intermuscular haematoma
|
Table 2.
British Athletics Muscle Injury Classification.
Type
|
Definition
|
MRI
|
0a
|
Focal area
of muscle pain
|
|
0b
|
Generalised
muscle pain
following
unaccustomed exercise
|
- Negative or patchy oedema
|
1a
|
Small
myofascial tear
|
- Oedema at the fascial border
- < 10 % extension in muscle belly
- < 5 cm craniocaudal distance
|
1b
|
Small
muscle-tendon junction tear
|
- Oedema < 10 % cross-sectional area at the muscle-tendon-junction
- < 10% extension in muscle belly
|
2a
|
Moderate
myofascial tear
|
- Oedema at the fascial border with extension into the muscle
- 10 - 50 % cross-sectional area at the muscle-tendon-junction
- 5 - 15 cm craniocaudal distance
- Architectural fibre disruption usually noted < 5 cm
|
2b
|
Moderate
muscle-tendon junction tear
|
- Oedema at the muscle-tendon-junction
- 10 - 50 % cross-sectional area at the muscle-tendon-junction
- 5 - 15 cm craniocaudal distance
- Architectural fibre disruption usually noted < 5 cm
|
2c
|
Moderate
intratendinous tear
|
- Oedema extends into the tendon with longitudinal length of tendon involvement <5 cm
- < 50% of maximal tendon cross-sectional area
- No loss of tension or discontinuity within the tendon
|
3a
|
Extensive
myofascial tear
|
- Oedema at the fascial border with extension into the muscle
- > 50 % cross-sectional area at the muscle-tendon-junction
- > 15 cm craniocaudal distance
- Architectural fibre disruption noted > 5 cm
|
3b
|
Extensive
muscle-tendon junction tear
|
- Oedema at the muscle-tendon-junction
- > 50 % cross-sectional area at the muscle-tendon-junction
- > 15 cm craniocaudal distance
- Architectural fibre disruption noted > 5 cm
|
3c
|
Extensive
intratendinous
tear
|
- Oedema extends into the tendon with longitudinal length of tendon involvement >5 cm
- > 50% of maximal tendon cross-sectional area
- probably loss of tendon tension,
no discontinuity
|
4
|
Full thickness tear
of muscle
|
- Complete discontinuity of the muscle with retraction
|
4c
|
Full thickness tear
of tendon
|
- Complete discontinuity of the tendon with retraction
|
Case 1.
MRI of a football player demonstrates patchy oedema in the rectus femoris muscle without architectural fibre disruption in axial (Fig. 1) and coronal (Fig. 2) Proton Density fat saturated images.
Munich muscle injury classification: 2B
British Athletics Muscle Injury Classification: 0b
Case 2.
MRI shows small architectural fibre rupture in the long head of the biceps femoris muscle at fascial border with extension into the muscle (Fig. 3, Fig. 4).
Surrounding oedema of 5 cm craniocaudal length.
Munich muscle injury classification: 3A
British Athletics Muscle Injury Classification: 2a
MRI is able to detect risk factors for re-injury and prolonged lay-off times,
especially intratendinous tears (British Athletics muscle injury classification "c" for example 3c with a mean of 80 lay-off days).
However,
some studies conclude that MRI does not add value over clinical examination and patient history (Wangensteen et al.).
In more severe muscle injuries MRI is able to visualize muscle / tendon healing in order to help guide further rehabilitation: restricted training vs.
longer break from training.
Case 3.
MRI two weeks after primary muscle injury (Fig. 5, Fig. 6):
Small architectural fibre disruption in the long head of the biceps femoris muscle at fascial border with extension into the tendon and muscle.
MRI six weeks after primary muscle injury (Fig. 7):
Recovering of tendon structure with thickening and surrounding oedema demonstrates prolonged time to return to play.
Munich muscle injury classification: 3A
British Athletics Muscle Injury Classification: 2c/3c
Case 4.
Field hockey player with complete rupture of the long head of biceps femoris tendon.
Note the wavy contour of the tendon and the architectural fibre disruption (Fig. 8,
Fig. 9).
MRI after 6 weeks (Fig. 10,
Fig. 11) demonstrates healing with thickening of the tendon structure with hypointense signal.
Munich muscle injury classification: 4
British Athletics Muscle Injury Classification: 4c
Case 5.
Pain and swelling of the right lower leg after collision during football game.
Coronal and axial STIR (Fig. 12,
Fig. 13) as well as axial T1 weighted image (Fig. 14) showed a 4 cm intramuscular haematoma in the medial head of the gastrocnemius muscle with surrounding oedema but no architectural fibre disruption.
Munich muscle injury classification: direct muscle injury
British Athletics Muscle Injury Classification: not classifiable
Diffusion-Tensor-Imaging (DTI) is a promising tool to detect muscle injuries that cannot be visualized by standard MR-sequences as STIR or T2 / PD fat sat.
Froeling et al.
examined the upper legs of five longdistance runners (DTI,
T1-weighted MR imaging,
and T2-weighted MR imaging with fs) 1 week before,
2 days after,
and 3 weeks after they participated in a marathon.
Fractional anisotropy (FA) was significantly increased in the biceps femoris muscle 2 days after running,
even when T2-weighted MR imaging with fs was normal.