Effect of pdo facelift threads on facial skin tissues: An ultrasonographic analysis

Recent studies demonstrate that PDO threads, after being introduced into the facial skin, provide benefits due to collagen formation around the thread and improved vascularization.

| 2535 LOTS safe conduct and effective minimally invasive facial procedures. 2 An effective and successful facelift treatment must be based on a thorough understanding of the changes in the face due to aging. 3 Polydioxanone (PDO) threads have been routinely and safely used as suture threads in surgical procedures for over 3 decades. It is an absorbable polyester monofilament consisting of a very flexible polymer, composed of paradioxanone monomer, which is degraded in the body by simple hydrolysis. 4 Acting as a neovascularization agent in collagen regeneration 5 and as a degenerating agent of adipocytes. 6 In the same histopathological study, Yoon 6 demonstrates that there is a proliferation of fibroblasts between 0 and 24 weeks after thread insertion, forming fibrous connective tissues, which can stimulate soft tissue reinforcement by fusion with existing connective tissues, in addition to improvement in circulation, via increased capillary volume. The ultrasound examination can promote anatomical details changes in the skin and deep tissues. Ultrasound has become a unique medical imaging tool in the investigation of dermatological diseases and normal skin. By providing high-resolution gray scale images and blood flow information in real time, ultrasound can provide detailed anatomic and physiologic data of skin lesions and deeper soft-tissue changes. Lesions size in three dimensions-lengths, width and depth, morphology, inner structure-solid, cystic or mixed, homogeneous or inhomogeneous, foci of calcifications or necrosis, location, and extension can be diagnosed. 8 Ultrasonography was first introduced in 1979 by Alexandre Miller as a non-invasive imaging technique without ionizing radiation to assess skin thickness. 9 Ultrasound can promote anatomical and physiological details of the skin and deep tissue changes, and using high F I G U R E 1 Hyperechoic images of the formation of fibrosis around the PDO thread at days, 30, 60, 90 and day 120. frequency ultrasound ranging from 6 to 18 MHz, it is possible to define the skin layers and deep structures, as well as the vascularization walls, in real time. In the same study, the authors demonstrate on high-resolution ultrasound images of normal skin and its deep structures: The epidermis can be seen as a thin hyperechoic layer; the dermis can be seen as a hyperechoic band with varying thickness; the subcutaneous layer is hypoechoic, usually with fat lobes surrounded by hyperechoic septal lines; muscles are hyperechoic, with hypoechoic lines; marginal bone part appears as a hyperechoic line. 10 Strong echo ultrasound produces hyperechoic images like epidermis, bones, cartilage, septa involving fat, muscle fascia, Russian threads, and PDO threads (with formation of fibrosis around the thread) ( Figure 1); intermediate echo produces hypoechoic images like glands, muscle fibers, connective tissue, soft tissue, and low crosslinking hyaluronic acid; weak echo ultrasound produces anechoic images like vessel lumen, high crosslinking hyaluronic acid, and PDO thread (immediate to insertion).

| Study Sample
The clinical part of this study involved 10 patients aged 40-  (Figure 4). The initial measurements, 30, 60, 90, and 120 days, after lifting will be displayed on a table.
The linear probe used in this study was placed on the skin in a fixed standard position, with the echo recorded at a speed of F I G U R E 2 Photographs of a subject before and 120 days after the procedure. 1580 m/s, to obtain a two-dimensional image. Parameters TA-Texture analysis (contrast, correlation, energy, homogeneity) 12 were used from the selected regions of interest.

| Statistical analysis methodology
For this study, generalized linear models were used for repeated measurements over time. The analyzes were performed in the statistics program R, 13 considering the significance level of 5%. Objective: Compare measurements over time.
The study carried out aims to demonstrate that the face lift technique was based on the anchorage of the PDO threads in the true ligaments of the face: Inferior Temporal Septum, Zygomatic Adhesion Ligament, and Mandibular Ligament, [14][15][16] as an agent of lipolysis degrading adipocytes, and as an inducer of collagen formation starting in fourth week after insertion of the threads, proven through ultrasound measurements for 120 days.
With patients able to receive the facelift treatment, after 30 days of skin preparatory procedures, the lifting was performed with 8 threads Sculpt 18G 100 × 85 mm, 4 on each side of the face, and 20 Flats threads distributed 5 on each side of the face in the sulci: Naso labial and Naso mentoniano, in the same session ( Figure 4). Table 1 shows the results of measurements of the epidermis/dermis and hypodermis layers. There is an increase in statistically significant measurements of the epidermis/dermis layer in the nasomental sulcus, anterior chin, on both sides of the patients, over time (p < 0.05).

| RE SULTS
Variations were then analyzed. The measurements between the time and the results of these comparisons are presented with letters. The time that did not show statistically significant differences (p > 0.05) received the same letters, according to the grade of the  In the zygomatic region on the right side, at 30 days, the layer thickness was significantly smaller than at the initial time (p < 0.05), already on the left side, after 60 days the thickness in this region was significantly smaller than in the initial time

| DISCUSS ION
Ultrasound provides reliable support in detecting cosmetic fillers; it has the potential to map the aesthetic pre-procedure and can be used to assess longevity and effects characteristics of cosmetic materials. 17 The ultrasound examination is a non-invasive, risk-free, and radiation-free diagnostics tool. Ultrasound images are identified in terms of reflected echoes, which are converted into electrical energy, amplified, processed, and displayed in a screen with hypoechoic, hyperechoic, and anechoic images. 18 The diagnosis ultrasound is compared to clinical, radiographic, and histopathological diagnosis. 19 The 360° molded PDO threads (Molding Cog) have high lifting capacity and support of the ptosis tissues, with greater anchoring force,

| CON CLUS ION
Corroborating previous studies, this work observes an increase in facial dermal thickness, and decrease in the hypodermic layer, starting after implantation of the PDO threads, evaluated through ultrasound measurements for 120 days.
The effect of increasing the thickness of the Dermal layer PDO thread installation is acquired by the formation of fibrosis formed around the thread, indicating the growth of the interstitial and collagen component, as well as improvement in the appearance of the sagging skin evaluated by photographic control. The effect of decreasing the hypodermic layer is acquired through the denaturation of adipocytes and tissue repositioning, by non-surgical lifting whith the PDO thread.

AUTH O R CO NTR I B UTI O N
PHM conceptualized and supervised the study and methodology.
TCL performed the formal analysis. Both authors contributed to the investigation, project and resources administration, writing of the original draft, review and editing.

FU N D I N G I N FO R M ATI O N
This study was partially sponsored by MedBeauty as they provided the PDO threads.

CO N FLI C T O F I NTE R E S T S TATE M E NT
None of the authors listed have any commercial associations or financial disclosures that might create a conflict of interest with the methods applied or the results presented in this study.

DATA AVA I L A B I L I T Y S TAT E M E N T
The data that support the findings of this study are openly available in Telma Lots at (DOI).

E TH I C A L A PPROVA L
Authors declare human ethics approval was not needed for this study.