The role of ultrasound in aesthetics injections of botulinum toxin and dermal fillers: part 1
Ultrasound is one of the most commonly used imaging modalities worldwide being shown to be extremely safe, reliable and non-invasive (Kaproth-Joslin et al 2015). First utilised by Karl Dussik in 1942 (BMUS 2022, Kaproth-Joslin et al 2015), the use of ultrasound in healthcare has become ubiquitous, with many stake holders including doctors, sonographers, radiologists, sports physicians and physiotherapists among the people now using the technology. Ultrasound was first used in dermatology in 1979 by Alexander and Miller to measure the thickness of the skin (Polanska et al 2017), however the adoption and use of ultrasound in the field of medical aesthetics has been slow (Miller 2022).
A paper by Wortsman and Wortsman (2011) described sonographic outcomes of cosmetic procedures including the most common non-surgical aesthetic procedures of botulinum toxin and cosmetic filler injections. Since this time more research has been published concerning the use of ultrasound in the field of aesthetics and the technology is slowly being incorporated into clinical practice. The main barriers to adopting the practice being the cost of the ultrasound machine and the steep learning curve of identifying sonographic anatomy and delivering aesthetic injections under ultrasound guidance (Miller 2022).
Traditionally, many injections are delivered using anatomical landmarks termed landmark guided injections (LMGI’s) however there is now a movement towards using ultrasound guidance known as ultrasound guided injections (USGI’s) (Alter and Karp 2017). In other fields such as musculoskeletal medicine there is strong evidence that USGIs are more accurate than LMGI’s, moderate evidence that they are more efficacious, and preliminary evidence that they are more cost-effective (Finnoff et al 2015).
The purpose of this paper is to explore the current use of ultrasound in aesthetics with a focus on the most commonly used procedures of botulinum toxin and hyaluronic acid dermal filler injections (Wu et al 2022, Schelke et al 2018, Ho et al 2022).
The use of ultrasound guided botulinum toxin injections
Botulinum toxin injections are prescribed for a variety of conditions such as muscle spasticity and pain, masseter hypertrophy, headaches and migraine as well as for aesthetic procedures such as reducing overactivity of facial muscles to reduce fine lines and wrinkles. (Alter and Karp 2017, Escher 2017, Ho et al 2022). Ultrasound guided botulinum toxin injections are becoming recommended for chemodenervation procedures (Alter and Karp 2017); however, they remain uncommon when delivering botulinum toxin injections for aesthetic procedures (Lee et al 2018). This may in part be due to the very small and superficial nature of the facial muscles being targeted, however with the emergence of high-resolution ultrasound machines systematic ultrasound scanning protocols of the facial muscles have been documented (Wu et al 2022).
Ultrasound guided botulinum toxin injections for masseter hypertrophy have been reported (Wang et al 2022, Quezada-Gaon 2016) as have guided injections of botulinum toxin for the correction of asymmetrical smiles (Lee et al 2018), however these studies are of low-level evidence with small sample sizes. A recent systematic review by Li et al (2021) highlighting 24 studies investigating USGI’s of botulinum toxin into the masseter (n = 16), frontalis (n = 2), glabella complex (n = 2), trapezius (n=1), and gastrocnemius (n = 3) demonstrating these structures are well visualised on ultrasound and that US guided botulinum toxin injections are a useful tool for aesthetic procedures. However due to the inherently low serious adverse reaction and relative safety of botulinum toxin injections (Cavallini 2014, Borba 2022) the practice of US guided injections, although useful in botulinum toxin procedures is not essential.