Assessment of Superficially-placed Microaliquots of Small-particle HA

Hyaluronic acid (HA) fillers are traditionally used in minimally invasive cosmetic procedures to address fine lines, wrinkles, and contour irregularities.¹ HA fillers are able to provide the skin with structural support through hydration and stimulation of neocollagenesis.^2,3

Small-particle HA at 20mg/mL with lidocaine 0.3% (SP-HAL; Restylane Silk, Galderma Laboratories) is a transparent injectable HA gel that is FDA-approved for subdermal lip augmentation and correction of perioral rhytids. Fillers with low density and viscosity, such as SP-HAL, can be injected more superficially compared to other HA fillers with little to no risk of Tyndall effect.⁴ As a result, SP-HAL has been studied by some investigators for “skin boosting,” a technique where microaliquots of HA are placed in the papillary dermis.⁵

Our research team performed the first single center, randomized, sham-controlled, double-blinded, split-face trial using SP-HAL microaliquots in a grid-like injection pattern to address fine lines of the cheeks, which was published in 2018.⁶ Although we found no statistically significant change in the degree of wrinkling or elastosis between the treated and control sides, elastosis trended toward improvement post-injection Day 14. This minimal improvement may be due to a combination of factors including a lack of power (six patients were lost to follow-up), deep placement of SP-HAL, and the protocol being limited to a single treatment rather than a series of treatments, which is normally what occurs in clinical practice.

Our present study uses a modified protocol to include a series of treatments and include both biomechanical and clinical endpoints.

Study Details

This was an institutional review board approved prospective study that was conducted in accordance with the principles of the 1975 Declaration of Helsinki.

Males or females, 18 years and older with visible signs of aging involving at least a 9cm² area of the mid to low cheeks were eligible to participate in the study. The enrollment period was from February 2019 to January 2020. Written consent was obtained from all subjects prior to enrollment.

Exclusion criteria included: pregnant, planning pregnancy during the course of the study or breastfeeding; severe static rhytids to the mid to low cheeks; previous use of any form of soft tissue augmentation in the treatment area within the past 12 months; pre-existing medical or dermatologic condition in the treatment area that may affect the treatment or interpretation of treatment effect (at investigator discretion); presence of tattoo and/or scar in the treatment area that in the investigator’s opinion would interfere with study assessments; use of oral/topical retinoids within one month of baseline; previous use of botulinum toxins in the treatment area within the past six months; previous surgical procedure in the treatment area within the past 12 months; presence or evidence of any conditions that in the opinion of the investigator might impede the subject’s ability to give consent or comply with protocol requirements; current participation or participation within 30 days prior to the start of this study in a drug or other investigational research study; history of non-compliance with clinical research protocols; ablative laser resurfacing to on their face within 12 months; non-ablative laser or light procedures to their face within the past three months; and known allergy to Restylane Silk or any of its constituents.

Intervention. A total of 20 subjects were enrolled and received SP-HAL to both cheeks. The specific evaluated area was defined as the following: a line extending from the upper margin of the nasal ala to the upper margin of the tragus, from the tragus to 1cm above the mandibular angle, from 1cm above the mandibular angle to 1cm above the pre-jowl sulcus, and from 1cm above the pre-jowl sulcus to the upper margin of the nasal ala. The injections were delivered intradermally via multiple 0.02cc microinjections distributed in a grid array pattern with 1-2cm between each injection point (Figure 1). A 1cc syringe with a 30gauge 0.5-inch needle was used. Patients were offered the option of topical numbing application with LMX 4% Lidocaine cream, which was applied 30 minutes prior to procedure if requested. Prior to injection, the treatment area was cleansed with chlorhexidine. Following completion of injection treatment, manual massage by the injecting physician was applied to the full area to promote even distribution of the product.

Figure 1: Injections were delivered intradermally via multiple 0.02cc microinjections distributed in a grid array pattern with 1-2cm between each injection point.

Each subject underwent a total of three treatment sessions one month apart: Day 1, Week 4, and Week 8. The maximum amount of SP-HAL used per treatment session/per cheek was 1.5cc per cheek and the maximum total amount of product used for all three treatments in both cheeks was 9cc. Three-dimensional digital photography utilizing the Vectra 3D System (Canfield) was utilized to document pre-treatment status, sites of injection, and post-treatment effect. Subjects were followed up at 4 weeks, 8 weeks, post-treatment Day 90, and post-treatment Day 180. Objective measures including total epidermal water loss (TEWL; g/m²), elasticity (%), visco-elasticity (%), tiring effect (mm), relaxation (mm), and skin fatigue (mm) were measured with a cutometer (Cutometer Dual MPA 580, Courage & Khazaka, Köln, Germany) at baseline, post-treatment Day 90, and post-treatment Day 180 visits.

Study End Points. The primary endpoint was the Investigator Five Point Global Aesthetic Improvement Score (IGAIS) from baseline to all follow up visits through posttreatment Day 180, and objective improvement in TEWL, elasticity, visco-elasticity, tiring effect, relaxation, and skin fatigue from baseline to the last visit. The IGAIS was assessed on the following scale: (1) very much improved, (2) much improved, (3) improved, (4) no change, and (5) worse.

The secondary endpoint was the Subject’s Evaluation of Satisfaction (SES) performed at posttreatment Day 90 and 180 follow-up visits, which was assessed on a 6-point scale: (1) extremely satisfied, (2) satisfied, (3) slightly satisfied, (4) slightly dissatisfied, (5) dissatisfied, and (6) extremely dissatisfied.

Statistical Analyses. Statistical analyses were conducted on an intent-to-treat basis (i.e., all randomized subjects, with at least one follow-up visit, will be included in the analysis). All statistical tests were two-sided and interpreted at a 5% significance level. Descriptive statistics (i.e., mean, standard deviation, etc.) were provided for all continuous variables and frequencies for all categorical variables collected in this study.

Demographics. The demographics for this study are summarized in Table 1. Of the 20 patients that were enrolled in the trial, one patient was a screen failure (five percent) and eight patients (40 percent) were lost to follow up: two patients after the first treatment visit, two patients after the second treatment visit, two patients after the third treatment visit (one of these patients attended the final post-treatment Day 180 visit), and two patients before post-treatment Day 180 visit. Patients who dropped out of the study cited the following reasons: lack of clinical improvement and injection-related adverse effects, such as pain, bruising, and nodules.

Results. All patients opted to receive topical numbing prior to each treatment. Out of the patients who completed the study, the average amount of SP-HAL used per cheek per treatment was 1.0cc and the average total amount used in both cheeks overall was 6.1cc.

In terms of IGAIS, mean ± SD score was 3.76 ± 0.56, 3.67 ± 0.61, 3.41 ± 0.51, 3.63 ± 0.50 at Week 4, Week 8, post-treatment Day 90 and post-treatment Day 180 visits, respectively (Figure 2).

Figure 2: Mean IGAIS comparing Week 4, Week 8, posttreatment Day 90, and posttreatment Day 180.

Figure 3: Mean subject TEWL scores comparing baseline, posttreatment Day 90, and posttreatment Day 180.

The mean ± SD TEWL scores at post-treatment Days 90 and 180 were respectively 5.15 ± 2.60g/m² and 16.50 ± 4.33 g/m², compared to 19.28 ± 4.48 g/m² at baseline (Figure 3). A statistically significant change in mean TEWL score was noted across baseline, post-treatment Day 90 visit, and post-treatment Day 180 visit (p = 0.024; Figures 5-6). In regard to other cutometer-measured scores, there was no statistically significant changes in elasticity, visco-elasticity, tiring effect, relaxation, and skin fatigue (Figure 4) across visits or between baseline and post-treatment Day 90 or 180 visits (all p value above 0.17).

Figure 4: Mean subject cutometer scores (elasticity, visco-elasticity, tiring effect, relaxation, and skin fatigue) comparing baseline, posttreatment Day 90, and posttreatment Day 180.

Figure 5: 45-year-old Fitzpatrick skin type II subject with improvement of skin texture and hydration (left side)

Figure 6: Same patient as Figure 5 (right side).

Lastly, the mean ± SD SES score at post-treatment Day 90 and Day 180 was 3 ± 1.41 and 3.45 ± 1.51, respectively. There was no statistically significant change in mean SES score between post-treatment Day 90 and Day 180 follow-up visits (p = 0.46).

Adverse events were minimal, and included swelling, bumpiness, and ecchymosis, which all resolved by the end of the study. No vascular occlusion event or Tyndall effect was reported.

Discussion

In this prospective, open-label clinical trial, subjects underwent a series of three treatments of the mid-to-lower cheek spaced one month apart with up to 1.5cc of SP-HAL used per treatment session/per-cheek/per-subject. In this trial, more than 40 percent of subjects were lost to follow-up due to dissatisfaction with the cosmetic results or injection-related adverse effects. However, out of the twelve subjects who remained in the study, seven showed improvement in IGAIS at post-treatment Day 90 (58.3 percent), and out of the 11 subjects who remained in the study for the post-treatment Day 180 visit, four showed improvement in IGAIS (36.3 percent). Nine of the 12 subjects reported some level of satisfaction with the treatment (75 percent) at post-treatment Day 90 visit, and six subjects out of eleven at post-treatment Day 180 visit (54 percent). Mean TEWL scores significantly improved across baseline, post-treatment Day 90, and post-treatment Day 180 visits (p = 0.024). TEWL scores indicate that the placement of SP-HAL microdroplets effectively provides the skin with hydration through Day 180. However, other cutometer-measured scores (elasticity, visco-elasticity, tiring effect, relaxation, and skin fatigue) did not show statistically significant improvement. The treatment was well tolerated by patients who completed the study, other than expected temporary swelling, lumps, and bruising.

Multiple studies of non-animal stabilized HA (NASHA) fillers (Restylane Vital, Q-Med) have shown significant improvement in biomechanical endpoints, including skin elasticity, roughness, density, and hydration.^7-9 A recent retrospective study by Nikolis et al. demonstrated significant improvement of facial skin hydration level as measured by a corneometer after a series of three treatments with SP-HAL (Restylane Vital) spaced one month apart.¹⁰ However, TEWL scores of the face remained within normal limits and did not significantly change throughout the study.

Data from past studies investigating the clinical efficacy of SP-HAL skin boosting have been inconsistent. Streker et al. studied clinical improvement after three treatment sessions were performed on one side of the face, dorsum of one hand, and one side of the décolletage administering a small-particle HA at 12mg/mL with lidocaine 0.3% (Restylane® Vital Light, Q-Med) with an automated injector system.¹¹ Despite being a lower concentration compared to SP-HAL, their study product improved skin quality in more than 80 percent of subjects, and more than 70 percent of participants were satisfied. However, the split-face clinical trial published by our team in 2018 found no statistically significant improvement of cheek elastosis and wrinkling after a single treatment with SP-HAL compared to normal saline. Those findings prompted our team to devise a new study to perform a series of treatments rather than a single treatment and to look at both clinical and biomechanical primary endpoints such as TEWL, elasticity, and global improvement scores.

One reason our study did not show significant improvement in most clinical endpoints is lack of statistical power. Out of the 20 patients that enrolled into the trial, one patient (five percent) screen failed and eight patients (40 percent) were lost to follow-up due to dissatisfaction, bruising, nodule formation, or injection-related pain. Some of the past studies with favorable results were focused solely on biomechanical endpoints and used an automated injection system to place SP-HAL, which allowed for improved standardization of injection technique. Placement of product above the papillary dermis may lead to nodule formation while placement into the reticular dermis may disrupt vasculature, leading to increased bruising. In order to obtain accurate cutometer readings and clinical scores while mitigating adverse effects, SP-HAL must be always placed consistently and superficially in the papillary dermis. Additionally, using a lower concentration filler over the course of several treatments as Streker did may reduce nodule formation and improve clinical outcome. Lastly, unlike our 2018 trial, this trial was not a split-face randomized controlled trial and thus does not provide the same level of evidence.

Conclusion

A series of three treatments of SP-HAL skin boosting did not demonstrate improvement in biomechanical endpoints, except for mean TEWL. However, clinical improvement was noted throughout the study, as demonstrated by the improvement of SES scores at posttreatment Days 90 and 180, as well as the IGAIS at posttreatment Day 90.

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