Background  Hyaluronic acid fillers can be manufactured using various processes. They have multiple properties, including their concentration, degree of modification, and rheological data. Cohesion is one such property to evaluate gel integrity; however, there is no standardized method for calculating this parameter. This study aimed to evaluate different tests for calculating hyaluronic acid cohesion and discuss the importance of hyaluronic acid cohesion as a consideration when selecting fillers. Methods  The cohesion levels of five different hyaluronic acid fillers with different rheological properties were evaluated and compared using the drop weight, compression, tack, and dispersion time tests. Results  The cohesion tests yielded different results in the samples. Samples 2 and 4 showed approximately two times the number of droplets when compared with Sample 5 in drop weight test. Samples 1, 2, 3, and 4 were superior to Sample 5 in tack test. Samples 1, 2, and 3 showed cohesive appearances at 95 seconds in most cases in dispersion test. Rheological test results did not reflect the measures of cohesion. Conclusion  Although there are no definite standardized tests to evaluate the cohesion of hyaluronic acid fillers, our proposed tests showed similar results for different hyaluronic acid filler products. Further studies are needed to evaluate the cohesion of hyaluronic acid fillers and determine the clinical use of this distinguishing characteristic for clinicians selecting the product of choice. Level of evidence statement: These data are Level IV evidence.

UNASSIGNED: Biofilm formation is a major cause of delayed-graft complications. Similarly to implants, dermal fillers carry the risk of biofilm formation, which can lead to the development of nodules, chronic inflammatory reactions, abscesses and other complications. In this study, we investigated the late or delayed complications associated with biofilm formation on dermal fillers.
UNASSIGNED: In this retrospective analysis, we analyzed all cases of complications caused by filler injections at a single center between January 2017 and December 2022, the majority of which comprised nodule formation and chronic persistent inflammatory reactions. The risk of biofilm formation with fillers was summarized and analyzed based on the results of bacterial culture and pathological examination.
UNASSIGNED: Sixty-one patients were enrolled, including 42 cases of nodule formation, 15 of chronic inflammatory reactions, and 4 of active infection. Bacterial culture of the tissue samples obtained from seven patients after surgical treatment were positive, and comprised four cases of Staphylococcus aureus, one case of Staphylococcus epidermidis, one case of Staphylococcus saprophyticus and one case of Mycobacterium abscessus. The corresponding histopathological results indicated extensive mononuclear lymphocyte infiltration, with a giant cell reaction in the fibrous connective tissue.
UNASSIGNED: The results of this study suggest that biofilm formation is a significant risk factor for late and delayed complications following filler injection, and is caused by the contamination of resident bacteria and recessive infection at the injection site.

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Doppler ultrasound can be used to detect almost all arteries of the face before injecting the hyaluronic acid (HA) filler. The relatively more dangerous sites of filler injection are the glabellar wrinkle, forehead, temple, nose, and nasolabial fold area, and it is recommended to map the vasculature of these areas by Doppler ultrasound before performing filler injection. The Doppler ultrasound detection method is included as a video. Internal carotid arterial branches, the supratrochlear, supraorbital, and dorsal nasal arteries, and external carotid arterial branches, the superficial temporal and facial arteries, are very important arteries when injecting HA filler; thus, Doppler ultrasound detection is recommended.

BACKGROUND: Defined as a contour line from the hairline, the zygomatic arch, to the ramus and gonial angle area of the mandible, posterior facial frame (PFF) is an important aesthetic units of the face. With the development of hyaluronic acid fillers and the improvement of injection techniques, minimally invasive injection has become one of the first options to improve PFF. However, effective and systematic injection methods to improve PFF are rarely reported in the literature.
METHODS: We retrospectively analyzed 200 patients treated with area four technique for PFF. According to the clinical manifestations, PFF was divided into four types, and the injection strategies of the different types were described. GAIS (Global Aesthetic Improvement Scale) at 1 month and 3 months by patients after treatment was evaluated as primary end point. Nine-item aesthetic assessment scores reviewed by two independent observers with experience were performed.
RESULTS: GAIS showed that patients\' profile was remarkably improved for 90% of total number of subjects. Before and 3 months after treatment, the assessed scores of the lateral cheek lifting (3.17 ± 0.21 vs. 2.56 ± 0.31) and PFF (3.78 ± 0.56 vs. 2.19 ± 0.48) were statistically significant reduced (p < 0.01). The jawline contouring scale (2.32 ± 0.45 vs. 1.23 ± 0.31) and the lateral cheek fullness scale (3.01 ± 0.23 vs. 2.09 ± 0.17) showed a statistically moderate decrease (p < 0.05).
CONCLUSIONS: Area four technique provides a safe and convenient method for classifying and treating patients with insufficent PFF, which makes up for the multisite systematic injection of the face.

An important component of plastic surgery residency training is independent cosmetic patient management. A resident cosmetic clinic was created at Oregon Health & Science University in 2007 to expand this experience. The cosmetic clinic has traditionally been most successful in offering nonsurgical facial rejuvenation with neuromodulators and soft tissue fillers. This study focuses on the demographics of the patient population and the treatments provided over a 5-year period and compares this experience to those of the same program\'s attending cosmetic clinics.
A retrospective chart review of all patients seen at Oregon Health & Science University\'s Plastic and Reconstructive Surgery Resident Cosmetic Clinic between January 1, 2017, and December 31, 2021 was performed. Patient demographics, type of injectable received (neuromodulator versus soft tissue filler), location of injection, and additional cosmetic procedures were evaluated.
Two hundred patients met the study criteria, which included 114 seen in the resident clinic (RC), 31 seen in attending clinic (AC), and 55 patients seen in both. A primary analysis compared the two groups seen in the resident and attending only clinics. The average age of patients seen in the RC was younger, 45 versus 51.5 (P ≤ 0.05). There was a trend toward more patients in the RC being involved in healthcare as compared to those patients seen in the AC, but this difference was not found to be statistically significant. The median number of neuromodulator visits in the RC was 2 (1, 4) versus 1 (1, 2) in the AC (P ≤ 0.05) The most common location for neuromodulator injections in both clinics was the corrugators.
Patients in the resident cosmetic clinic were younger females, most receiving neuromodulator injections. No statistically significant differences were identified in patient population, injections received, and location of injections between the two clinics, indicating a similar trainee skill set and patient care plan between the two clinics.

Minimally invasive hyaluronan (HA) tissue fillers are routinely employed to provide tissue projection and correct age-related skin depressions. HA fillers can advantageously be degraded by hyaluronidase (HAase) administration in case of adverse events. However, clear guidelines regarding the optimal dosage and mode of administration of HAase are missing, leaving a scientific gap for practitioners in their daily practice. In this study, we implemented a novel rheological procedure to rationally evaluate soft tissue filler degradability and optimize their degradation kinetics. TEOSYAL RHA® filler degradation kinetics in contact with HAase was monitored in real-time by rheological time sweeps. Gels were shown to degrade as a function of enzymatic activity, HA concentration, and BDDE content, with a concomitant loss of their viscoelastic properties. We further demonstrated that repeated administration of small HAase doses improved HA degradation kinetics over large single doses. Mathematical analyses were developed to evaluate the degradation potential of an enzyme. Finally, we tuned the optimal time between injections and number of enzymatic units, maximizing degradation kinetics. In this study, we have established a scientific rationale for the degradation of HA fillers by multidose HAase administration that could serve as a basis for future clinical management of adverse events.

Volume restoration and enhancement of the gluteal region appearance has become nowadays a popular concern in particular for many women. Several options are available, none however are without complications and side effects. Volume enhancement with soft tissue fillers of the gluteal region is emerging as a highly attractive minimally invasive modality. It has led unfortunately to more unlicensed, nonmedical practitioners administering illicitly injections for buttock augmentation at relatively low costs.
To determine safety, efficacy, and cost effectiveness of mostly used soft-tissue fillers for buttock augmentation, a systematic literature search of PubMed, Medline, and Embase was conducted to identify the mostly used fillers for gluteal augmentation. It was complemented by searching for each of the identified filler material separately to retrieve any missed reports. References of clinical studies and trials, reviews, and consensus reports were reviewed as well for the same objective.
In the final analysis 12, mostly strongly biased clinical reports providing a low level of evidence, were identified for inclusion in the review. Two studies involved Polymethylmethacrylate (PMMA), 5 Poly-L-lactic acid, 1 Calcium hydroxyapatite and 4 hyaluronic acid filler injection. No studies were identified involving liquid silicone or Polyacrylamide hydrogel. The little available evidence provided by this review indicates that a specific brand of PMMA in Brazil has a demonstrable relatively good safety, efficiency, and cost-effectiveness record superior to surgical alloplastic gluteal augmentation or to lipofilling only when injected by experts.
Gluteal augmentation with soft tissue fillers is not as simple and innocuous as advertised. Serious complications may occur. Moreover, optimal buttock contouring entails not only volume augmentation but also volume removal; thus, volume augmentation with soft tissue fillers may not be ideal. Popularizing this modality must also be approached with great care. Serious complications do occur; they become inevitable when performed illegally by non-specialized, non-authorized, and unscrupulous practitioners in non-accredited facilities. Patients must be warned that adherence to regulations is critical and that only well-trained certified experts practicing legally in accredited facilities can address safely and efficiently their concerns.
This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Medical devices became subject to the current framework of regulation and premarket review by the Food and Drug Administration (FDA) in 1976. Devices are distinguished from drugs by the means in which they achieve their primary intended purposes. All medical devices, regardless of risk, share certain regulatory requirements to assure quality, safety, and transparency. Moderate- to high-risk devices must additionally be cleared or approved by FDA before being introduced into interstate commerce. Dermatologic devices regulated by FDA range from high-power energy-based devices to wound dressings, and from complex electronic devices to topically applied barrier creams.

Nasal enhancement is one of the most challenging and intriguing of aesthetic procedures. Although the nose is the most central and prominent facial feature, it should not be dominant while maintaining both a harmonious relationship with the face and its own intrinsic beauty. In this article, the first author shares his experience on how to specifically apply intradermal soft-tissue fillers (for particular indications) in nasal enhancement and incorporates patient assessment, anatomy of the nose, and injection techniques to provide guidance. Intradermal injections are required for specific regions, as for example in the treatment of internal and external valve collapse; however, several precautionary measures need to be implemented to minimize risks resulting in vascular compromise.