Advanced anatomy for Botox treatments: vectors, biomechanics & myomodulation
To excel in medical aesthetics, there is more to learn than just basic facial anatomy and injection technique. Aesthetic clinicians must understand the complex dynamics between structures like muscles, fat pads, bones, and ligaments and the nuances of the human form when we use cosmetic injectables.
In this blog, Dr Tim Pearce will explore levelling up your anatomy knowledge with a deeper exploration into concepts such as myomodulation, biomechanics, and vectors caused by gravity and muscle activity when it comes to facial anatomy and botulinum toxin treatments.
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What are vectors and how do muscles and gravity impact on facial features?
The first basic understanding within facial aesthetics and our impact on the face starts with botulinum toxin treatments and how muscles affect our appearance. If you relax the muscles, the wrinkles in the face start to fade. These lines and wrinkles are fading all the time; however, as we express ourselves, we keep ‘waking them up’ by moving. Thus, if you stop the movement, the lines fade. As Dr Tim points out, it is a lot more complex than this primary understanding.
Having understood the relaxation component, we can appreciate the relationship between different muscles and the vectors across the face. A vector is a force with a particular direction. All facial features are held in place by multiple different forces – muscles and gravity are the major components in control – and these are involved in a tug of war affecting the position of features like the eyebrow, the corner of the mouth, or the cheek.
If you over relax a muscle, gravity will take over and cause a drop in facial features, for example, with a flattened eyebrow or brow ptosis. This highlights that a muscle may be resisting a force, in this case gravity, and we must ensure enough muscle tension remains to support structures by not over treating or over relaxing muscles with botulinum toxin.
Every muscle in the face can impose a force on the skin or on a facial feature.
Similarly, it has a direction in which it pulls. This combination of force and direction is the vector and tells you the resting position of a facial structure.
A good example for illustration is the eyebrow. The eyebrow is held in position by the corrugator muscle that pulls medially, the frontalis muscle that pulls superiorly, and orbicularis oculi that pulls inferiorly. All these muscles are imposing a resting tension, (ligaments, fat pads and skin elasticity are also involved but we will talk about those later). Using a muscle relaxant, you weaken one side of this tug of war and the remaining muscles pull in a different direction – you cannot relax a muscle without altering the vector across the face, which is why we target certain muscles for treatment. This is made more complex because of the movement generated by different expressions which cause different vectors, that will be altered when you relax certain muscles. Signs of over treatment can be noted when the vectors are unnatural, e.g., Spock brow.
Dr Tim advises that you should look out for the vectors in every area of the face that you treat – think about what the net effect will be on the collection of muscles in the area. Review after photographs and video dynamic movement; over time with a patient, you will see the changes (good or bad) in the vectors and be able to optimise their treatment.
Why not get your hands on this beautiful anatomy poster as a useful reminder of all the muscles within the face.
What are the biomechanics of facial muscles and how can this impact on botulinum toxin treatment?
Biomechanics is an area that Dr Tim learnt about when visiting a physiotherapist for back pain. He discovered that he has one leg that is very slightly shorter than the other, which causes his muscles to extend in different places, affecting his flexibility, in turn causing back pain.
The same applies to the face – there are little differences between different people that cause different results with the same treatment, another reason why you cannot use one-size-fits-all approaches to treatment. For example, the origin and insertion points of a muscle, this is the angle at which a muscle is attached from the bone onto the skin, can change from person to person, and this will have an effect when you relax the muscle.
For example, the corrugator; its origin and insertion can completely change the likelihood of a medial brow drop if you just treat the frontalis. Thus, it is common practice never to treat the frontalis without treating the glabellar complex or corrugator because many patients have a downward vector that pulls their eyebrows down when they frown. However, this is not universal, and an understanding of the biomechanics allows you to establish which patients do not require simultaneous treatment to the glabellar complex.
To diagnose different biomechanics, Dr Tim encourages you to watch your patients as they move their face, and this does not necessarily just mean the movements they make because you have requested a facial expression.
He notes that the best observations you can make are when you have not asked them to move but you are watching their expressions as you listen to them speak during the consultation. When you do ask them to move, and make specific expressions, try and seek natural movement, rather than exaggerated or extreme facial expressions.
Learn more about the problems when patients return for a follow-up and create ‘over-testing’ facial movement after Botox® treatment. These recruit different muscles and often occur when they are trying to convince you that they require a (free) top-up treatment.
How do fat pads and ligaments impact on muscles?
Fat pads can help and hinder facial features and movement at different stages of life. If a patient has put on weight and has extra volume in the face, the fat pads dampen muscle movement, providing resistance as they contract, because they are trying to the squeeze the fat pad as well. Similarly, even as it relaxes, there will be other fat pads that are dampening the amount of movement it can make; in some cases, patients have reduced expression due to the impact of the voluminous fat pads on their muscles. Fine lines and wrinkles are fewer in those with larger fat pads because the muscle is less able to create a crease.
Conversely, if a patient’s fat pads shrink, due to ageing in older patients who have lost volume, then there will be more movement, which can be exaggerated and caricature-like. They could benefit from volume restoration with dermal fillers to balance the muscle movement. A patient who has lost weight often goes on to develop more fine lines and wrinkles. As muscles contract, particularly in those where the fat pads have shrunk, the position of the ligaments tends to be revealed because they are the last thing resisting within the tissue, highlighted on the face as shadows and lines.
What is myomodulation?
Everything we have discussed in this blog is related to myomodulation. If you cosmetically treat the face, you will modulate how the muscles interact with the rest of the structures – chemical myomodulation with botulinum toxin relaxes muscles and mechanical myomodulation with dermal fillers can increase or even reduce muscle action.
However, there is a deeper level of understanding, which Dr Tim explains using this illustration. Myomodulation is like a tug of war within a tug of war with myosin and actin working together. If you picture them like two teams in a tug of war battle except the difference is that when you look at a sarcomere (a contractile unit of muscle fibre) the teams are switched to face the other direction and they are pulling the walls together to contract the muscle. The rope is actin, and the players are the myosin. As they pull, they have a different amount of rope, and a different amount of room left.
So, let’s picture some muscles types, firstly a really stretched muscle – there are very few players who have any rope to hold on to; the resting strength of that muscle, the first ability for it to contract is quite low, therefore, it is not very strong.
At the other extreme, if we have a muscle that is all contracted, there is no room to pull the rope any further, and the players are all compressed together. This is also a weak muscle.
The ideal position of a muscle is when it sustains itself because there is a decent amount of overlap, with room to contract and many of the myosin and actin fibres are easily in contact. The resting tone is therefore at its best. This is how muscles present in youth, but with different amounts of either over stretching or over compression, it results in the facial features being negatively affected.
Myomodulation in action means that if, for example, you have a muscle where there is little support from the fat pads it becomes stretched, replacement of the fat pad using dermal fillers will allow it to move back into its zone of strength, to pull up the facial features slightly and harmonise. Check out why 80% of visible ageing is due to ligaments and fat pads.
If you have any questions or comments about facial anatomy, vectors, muscle biomechanics, or mymodulation, you can find Dr Tim Pearce on Instagram.
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Aesthetics Mastery Show
ADVANCED ANATOMY ESSENTIALS: Myomodulation, vectors, biomechanics explained
In this Aesthetics Mastery Show, Dr Tim has a deep exploration of how the sometimes opposing, and sometimes collaborative forces in our faces affect the aesthetic treatments we perform in our clinics, such as Botox and dermal filler. He covers concepts such as myomodulation, biomechanics, vectors, and gravity. Watch the full Aesthetics Mastery Show here.
The show has had great feedback and comments, including:
Pa Nan said:
“Such critical points in the fundamental understanding of facial harmony, and the essence of beauty, as it pertains to preserving the ever so elusive character of the youthful expression.. I think it to be most key to the beauty of a face . I am hopeful more practitioners will adopt these theories. Thank you”
“Thank you for this. Excellent teaching. So happy you covered this. Every face is definitely different and no treatment should be one size fits all. You are wonderful together. Keep up the great work.”
Read more comments or join in the debate on our YouTube channel.
Dr Tim Pearce eLearning
Dr Tim Pearce MBChB BSc (Hons) MRCGP founded his eLearning concept in 2016 in order to provide readily accessible BOTOX® and dermal filler online courses for fellow Medical Aesthetics practitioners. His objective was to raise standards within the industry – a principle which remains just as relevant today.
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