Hamstring free tendon tears

[Sally Quinn]

Hi Steve,
Could you comment on the above please?
I have trouble with the concept that a conjoint tendon can be torn at the M/T junction, but only involving the biceps femoris and not the semi T.
Any grading of tears tips would be good.
Thanks

[Stephen Bird]

Hi Sally,

Yes, it is a difficult concept to get your head around.

The best metaphor I can think of is if we were on the same team in a tug of war competition.

So we are both holding the same rope, but we each have our own hands gripping it and we are both pulling as hard as we can to try and beat the other team.

In this scenario I am not as strong as I would like to be! So I am only generating a moderate amount of force on the rope and hence my grip is secure and the rope is held easily by my hands. You a=on the other hand are an athlete and your superior core strength means you are generating a lot more force on the rope and will be a much more =important member of our team. Unfortunately however, the extra force you are generating is too much for the grip strength of your hands and the rope is slipping through your hands and the full force you are generating is not passed on to our opposition.

So this is in fact a metaphor for a MTJ tear of your muscle from the conjoint tendon while my muscle has not been damaged.

So let’s look at this in hamstring anatomy.

The “Conjoint tendon” is a single piece of collagen that is attached at its origin to the bony ischial tuberosity (and also the sacrotuberous ligament, but this is another story).

This conjoint tendon is shared on the lateral aspect by the long head of biceps femoris and on the medial side by the semitendinosus muscles.

It may be that during a violent hamstring contraction muscle fibres from both muscles are torn from the conjoint tendon and this is what I describe as being an “undoing of a zip” type injury and I think this is fairly easy to understand.

BUT

The biceps femurs long head muscle is much stronger than the semitendinosus muscle, so in my scenario you are the biceps femoris and I am the semitendinosus.
When the hamstring contraction occurred the biceps femoris long head muscle fibres (you) were disrupted from the conjoint tendon, but at the same time the semitendinosus fibres (me) were not damaged.

And this is how it happens.

There are many examples of this throughout the anatomy of the human body and the same thing can also occur within a single muscle if the design of the muscle is bi-pennate. An example of a bi-pennate muscle would be supraspinatus, where the muscle uses a single, centrally placed tendon like the quill of a feather and attaches to each side of it.

As for grading:

MRI is still the gold standard and the British Journal of Sports Medicine have published a paper on grading using MRI that also includes some return to play time advice. It is a paper I personally find a little confusing and contradictory at times, not unlike the TIRads literature.

For ultrasound I like to keep it simpler.

Firstly describe the muscle(s) involved and the location:
Enthesis injury
Tendon injury
MTJ injury

Some folk also include myofascial injuries, however I feel these are really just MTJ injuries occurring further into the muscle associated with the intramuscular extension (expansion) of the tendon.

The the severity of the injury:

Grade 0 = Painful hamstring but no ultrasound abnormality

Grade 1 = A minor ultrasound finding like a focal area of increased echogenicity in the muscle adjacent to the tendon , but with our architectural damage to the muscle

Grade 2: A defined area of muscle failure with associated haematoma and architectural damage to the muscle

I don’ mind using 2A and 2B for minor versions of these and more severe versions, but i would prefer to just describe the findings.

Grade 3: Complete disruption of the muscle / tendon unit

This brings me to one more important point. When you look at a hamstring MTJ tear, you need to consider that the tendon actually passes deep into the muscle and in fact extends so far it passes the distal tendon extension in the opposite direction.
So you need to ask: Did the muscle tear from the tendon and the intra-muscular tendon stayed intact, OR did the intra-muscular tendon fail?

The difference is important in terms of rehab and time to return to play.

So search down that intra-muscular extension of the tendon and try and ascertain if it has remained intact or failed.

I do love hamstrings, but they can be complicated!

Steve.

[Sally Quinn]

Hi Steve,
Thanks for the detailed reply.
So when you say the intramuscular extension of the tendon has ‘failed’, does this mean fully torn/ruptured?
I understand that your metaphor scenario is the situation where the muscle tore from the tendon.
Cheers

[Stephen Bird]

Yes, indeed Sally,

When I say the intramuscular extension has failed, I mean it has torn “popped” and there is no longer an intact line of collagen tendon running through the muscle.

I think of this as a sort of scaffolding for the muscle.

Steve.

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