Keywords
lips - contouring - volumizing - labial arteries - danger zone
Lips are the central point of focus in the lower face and have always played a key role in facial attractiveness. Besides their function as a perioral sphincter (together with the perioral muscular complex), lips are majorly involved in the expression of emotions, speech building, and food intake. The human lips have evolved during various evolutionary steps when compared with the lips of apes: they have increased in volume and the vermillion became more everted.[1] The eversion of the lips is thought to increase the contrast between the white/brown perioral skin, and the increased volume is thought to facilitate nonverbal communication and thus increase attractiveness.[1]
In today's society, these features, contrasting pigment color and lip fullness, are still considered to increase facial attractiveness and have become a major area of interest. Using lipstick increases the contrast between the lips and the perioral skin, whereas using soft-tissue fillers increases the lip volume. The demand for the latter (soft-tissue filler volumization) is increasing independent of gender, ethnic background, or age. Hyaluronic acid-based soft-tissue fillers are one of the most used agents for this type of treatment.[2]
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On the contrary, loss of lip contour, lip volume, and/or presence of perioral wrinkles are considered signs of facial aging and have been associated with reduced attractiveness.[12]
[13] Reducing the signs of lip aging is crucial to restore facial attractiveness. Multiple techniques to restore facial aging via the treatment of the lips have been described.[14]
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[19] However, few of these techniques have been validated for the positioning of the injected product in relation to the superior/inferior labial arteries. It is widely accepted that injection of soft-tissue filler material into the arterial system is associated with tissue loss (necrosis) and potential end-arterial embolism (potential blindness).[20]
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The present study describes and summarizes injection techniques targeting the lips with hyaluronic acid-based soft-tissue fillers, which are frequently used in Middle Eastern and Caucasian patients. The injection techniques included in this anatomical study are based on the experience of the authors, each with more than 20 years of experience treating signs of facial aging and the lips using soft-tissue fillers. The included injection techniques were verified in the cadaveric model for their positioning within the upper/lower lip in relation to the superior/inferior labial arteries.
Material and Methods
Injection Techniques
The injection techniques presented in this study are based on the experience and personal selection of the authors. The authors have assessed, treated, and evaluated for more than 20 years patients from the Middle East and Central Europe. Based on individual algorithms of the authors, some of the most frequently used injection techniques are presented in the following.
The injection techniques presented include the usage of a 27G x 1/2” and 30G x 1” sharp needle (various companies) and 22G x 2” and 25G x 1 ½” blunt tip cannula (various companies). Various injection points were used and each technique was tailored in application and amount of injected product based on patients' needs and clinical indication.
Anatomical Verification
The same injection techniques as used by the authors in the (living) patients were performed in the upper and in the lower lips of three fresh cadaveric specimens (1x male / 2x females) having a mean age of 84.67 ± 10.02 years and a body mass index of 26.18 ± 5.45 kg/m2. Specimens were screened and not included into this analysis if previous facial surgery or diseases disrupted the integrity of the facial anatomy. Each body donor had given informed consent while alive for the use of his or her body for medical, scientific, and educational purposes. All aspects of the study conform to the laws of the country where the study was conducted.
The injected product (for the cadaveric injections) was commercially available hair gel mixed with commercially available food coloring to visualize the injected product inside the cadaveric tissue. The superior and inferior labial arteries were previously injected with red latex, to visualize the arterial vascular system of the lips. Cross-sectional dissections and photo-imaging was performed to identify the placement of the injected colored product inside the lips and to relate the position of the product to the superior/inferior labial arteries.
Discussion
This study presented 12 different injection techniques frequently used in Middle Eastern and Central European patients when addressing the lips for aesthetic purposes. The presented techniques included contouring (using a needle), volumizing (using both needles and cannulas), and labiomental treatment (using both needles and cannulas) for labiomental volume loss. Cadaveric verification was performed for each of the presented techniques to identify the positioning of the injected product inside the superior/inferior lip. The results of the anatomic analyses revealed that in 58.3% of the performed injections the product was placed in close proximity to the superior/inferior labial arteries. The placement of the injected material in the vicinity of the superior/inferior labial arteries indicates a high risk for intra-arterial applications, leading to tissue loss (necrosis) and potential end-arterial embolism (potential blindness). In 60.0% of the cases, applications using a needle placed the injected product in endangered locations, whereas 57.1% of the cases using cannulas placed the product in endangered locations (i.e., in the vicinity of the superior/inferior labial arteries).
The results of the anatomical analyses, however, need to be interpreted with caution. First, positioning the product in close proximity to an artery does not necessary mean that the product was placed inside that respective vessel. Placing any product inside the lips requires skills and experience. The location where a product can be injected is limited to the reduced thickness of the lips, which holds especially true for aged lips and those needing treatment. Thus, it can be assumed the any product injected has a certain relationship to the labial vasculature, but the precise plane and the used injector will influence the outcome. However, being in the same plane as the artery (submucosal, intramuscular, or subcutaneous) represents a higher risk to potentially penetrate intra-arterially, whereas having the product separated by the orbicularis oris muscle represents a certain degree of safety.
Second, the vasculature of the lips is highly variable. A recent study has reported that three different positions of the labial arteries are possible: submucosal (i.e., between the oral mucosa and the orbicularis oris muscle in 78.1% of the cases), intramuscular (i.e., between the superficial and deep layers of the orbicularis oris muscle in 17.5% of the cases), and subcutaneous (i.e., between the skin and the orbicularis oris muscle in 2.1% of the cases). The variability in changing the respective position along the labial course was 29% for the total upper and 32% for the total lower lip.[24] The present study confirms the results presented in this report as the labial arteries were identified to run in variable positions independent of the upper/lower lip. On the contrary, the presence of multiple labial arteries also indicates that lips are very forgiving in their nature due to their excellent vascularization. Adverse vascular events might be tolerated and masked well before being clinically apparent. This might be one of the reasons why this few adverse vascular events are being reported in relation to the magnitude of performed labial injections for aesthetic purposes.[22]
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[26] It can be stated that injections deep inside the lips, that is, intramuscular or submucosal, for volumizing procedures (independent if conducted with a needle or a cannula), are associated with a higher risk for intra-arterial positioning of the product.
Third, in the present study the lumen of the arteries was filled with latex, which does not allow a needle or a cannula to penetrate inside the vessel. In a clinical scenario, some of the performed injections in this experimental setting might have positioned the material inside the artery. This is represented in the current analysis by a close relationship between product and artery and could be potentially considered as an indicator for a higher risk for an intra-arterial injection.
The injection techniques presented in this study are based on the experience and personal selection of the authors. The authors have assessed, treated, and evaluated for more than 20 years patients from the Middle East and Central Europe when targeting lip contour, lip volume, and labiomental volume loss. Albeit the focus of a specific treatment might be the lips, which can be sometime expressed very directly by the consulting patient, it has to be well explained that the perioral region needs to be addressed first and later the lips themselves. Lip treatment is a multistep approach. Perioral volume loss, perioral wrinkles, and even midfacial or upper facial corrections should be assessed first (if agreed by the patient). Perioral treatment options can influence significantly the positioning of the lips (cranial repositioning after addressing the nasolabial sulcus) and the volume of the lips (increased eversion after treating the deep midfacial fat compartments due to influence of the levator labii superioris alaeque nasi muscle). Age-related changes in the perioral region are caused by a combination of several factors including changes in bony structures (loss of alveolar process), loss of subcutaneous volume (fatty deflation theory), skin laxity (loss of collagen and elastic fibers), and skin sagging (gravity induced). These changes can cause ptosis of the oral commissures, resulting in an inferiorly positioned and deflated labiomental region. The formation of a prominent labiomandibular sulcus (i.e., the marionette lines) can likewise influence the appearance of the lips due to the close relationship to the corners of the mouth.
Middle Eastern females have in general good labial volume, whereas Central European females in the same age group have slightly less volume. Thus, the treatment should focus here rather on contouring than on volumizing. Applying volume in the white (skin covered) and red lips forms a subcutaneous scaffold that stabilizes the lips and provides support for the lower third of the face. Based on the cadaveric part of the present study, it should be noted that 58.3% of the volumizing procedures were related to a potential intra-arterial injection because the product was injected deep inside the body of the lips. On the contrary, procedures aiming for contouring can be regarded as safer as in this case, the product was positioned in the subcutaneous plane which is separated from the arteries by the orbicularis oris muscle.
Conclusion
Based on the experience of the authors, the treatment of the lips should be a multistep approach focusing first on the far (upper and middle face) and close (labiomandibular and labiomental) perioral regions. Individuals with an acceptable lip volume should be directed more toward the treatment of the lip contours, whereas individuals with volume deficiency should have first the volume and secondary the contours addressed. The lips are a potential danger zone as 58.3% of the performed cadaveric injections were in close proximity to the superior/inferior labial artery (and its branches), representing an elevated risk for tissue loss (necrosis) and potential end-arterial embolism (potential blindness).
