Muscle injury terminologies

[Linh]

Hi Steve,

I’ve come across terms describing muscle injuries in MR and US such as intramuscular tear, contusion injury, muscle strain injury. Are there any differences in those terms?

For example, I’ve seen soleal tear on a Rugby player with an impaction injury with obvious muscle architectural distortion (heterogeneity/loss of fibrillary pattern) at lateral proximal muscle belly and the radiologist describe it as muscle strain.

There is another case where the patient does martial arts competition and her opponent repeatedly kicked onto her lateral thigh and the result was a large haematoma in the vastus lateralis with intramuscular oedema (on MR). These are described as sequela of a contusional injury. It means there is an intramuscular tear that is filled with blood?

Can you please enlighten me 🙂

[Stephen Bird]

Hi Linh,

These various terms can be used loosely sometimes.

You mention a few:

intramuscular tear: I don’t think I would ever use this term as it implies the muscle has simply torn through the “meaty” part of the central muscle and I personally don’t think this is a thing.
When I see a muscle tear in the central part of a muscle (hamstring its a good example) it is always associated with one of the intramuscular tendon extensions (some people call them aponeurotic expansions) . They are natural anatomical extensions of the tendon which travel deep into the muscle. When the muscle tears from these intramuscular tendons I refer to this as a musculotendinous junction failure. Then it is also possible for the intramuscular tendon to fail itself and this is a more significant injury in terms of return to activity time. In these cases I describe the rupture of the intramuscular tendon. In all of these tears the mechanism is overloading of the muscle.

Contusion injury is completely different as this is not a result of overloading of the muscle but rather compression of the muscle from an external source (like being hit). In the case of a contusion the compression of the muscle causes capillaries inside the muscle to explode, leaking blood into the interstitial space of the muscle architecture. Sometimes larger vessels are damaged and a haematoma may result. The key difference is a muscle “tear” is associated with overloading stress and a contusion is associated with external compression.

Muscle strain injury, I think of as a minor version of an intramuscular tear where there is no significant ultrasound findings of architectural failure, but the patient still feels like they have damaged the muscle.

Another mechanism is delayed onset muscle soreness (DOMS) where the muscle is overloaded with too much exercise and reaches a state of metabolic exhaustion. It is the feeling you have in a muscle after you work too hard at the gym after not going for a while and the muscle aches or burns a few days after and then resolves. If you have a significant DOMS you will see similar findings to a contusion where the muscle looks a little more echogenic than normal and feels tight under the transducer. It usually affects the whole muscle where as a contusion can be more localised. The difference is really in the history. The contusion injury has a history of being struck and the DOMS has a history of overuse.

Steve

[Linh]

Thanks Steve, great explanations that are easy to understand.

1)
I assisted in a PRP inj for a Semimembranosus tear and I was reading the report as follows:
Acute high grade partial tear SM tendon at mid thigh level, towards prox MTJ with involvement of >50% cross sectional area of tendon, with redundant prox & dist tendon edges lying within haemorrhagic fluid collection. Adjacent feathery intramuscular odema & muscle architectural distortion => consistent w British athletics grade 3C injury

Does “redundant” in this case mean that there is 2 tendon stumps? So it is full thickness/complete tear?

Out of interest, I did some preliminary imaging/taking clips/comparing to other side and the US appearance looks a bit underwhelming to me as I can see a thickened, hypoechoic SM prox tendon, not much haematoma to see the tendon “stumps”/disruption but apparent muscle heterogeneity/hyperechogenicity at its MTJ.

2) How do you differentiate from the sonographic appearances of DOMS and rhabdomyolysis since the mechanism of injury is roughly the same?

Best regards,
Linh

[Linh]

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[Stephen Bird]

Yes, I think the term redundant indicates that the central tendon has popped which makes this a high grade injury with a longer recovery time.

I have experienced what you describe many times and it is not unusual for me to scan a hamstring and be happy there is a subtle but significant tear and then for the radiologist who is viewing it in real time with me to be unconvinced that it is a certain abnormality. They can be very subtle sometimes on ultrasound. In this case I always suggest a quick MRI sequence through the area to prove me right or wrong. The radiologist is always happy with this as they will then have confidence in their report. When you do the MRI the injury is MUCH worse than I expected. So the MRI will always show the complete extent of the injury as it is so sensitive to the oedema and extravasated blood products. The ultrasound certainly underestimates the extent of the injury in my opinion.

DOMS and rhabdomyolysis are a bit different to a tear. Firstly and most importantly the history is different. With a tear there is a clear history of an acute event which stopped the person performing the activity or at least an acute awareness that something had gone wrong. With DOMS and rhabdo the pain comes a day after the activity and there is no clear point of acute injury.
Secondly a tear affects a defined area of the muscle architecture , for example the proximal MTJ etc but DOMS / rhabdo tend to affect the muscle more globally.

You could have a patient who was tracking to an inevitable DOMS / rhabdo event and then did an acute tear as well. This would be tricky, but I still think you could make the diagnosis based on the history and imaging findings.

Steve

[Linh]

Thanks Steve. If patient has an MR and US of the Hamstring on the same day, what can US add to the MR findings (since MR is clearly superior)?

I haven’t worded my question right. I meant: How do you differentiate DOMS FROM Rhabdo since they are similar in US appearances and history?

My patient increased her weights too rapidly from 5kg to 10kg and both arms were tight the next few days. The below file shows that her long head triceps is affected but not the lateral or medial heads? I did not know this selective involvement is possible.

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