Using PDO threads: A scarcely studied rejuvenation technique. Case report and systematic review

Thread lifting procedures for facial rejuvenation have made great strides with the development of absorbable threads. Although they have gained fame among plastic surgeons and dermatologists, there have been very few studies published in scientific articles on the effects of absorbable threads in facial rejuvenation, as well as few studies published by aesthetic physicians. The most effective and efficient techniques to determine the adequate place to insert the reabsorbable thread, and the different ways to evaluate the effectiveness of these aesthetic procedures, are still unknown.


| INTRODUC TI ON
Minimally invasive aesthetic procedures are increasingly recognized, and preferred, by users who are interested in improving the appearance of some part of their body without surgery. These procedures are in high demand, worldwide. Patients often seek in-office techniques that can help improve the signs of aging without the risk of mortality of surgical procedures. The threads are absorbable and come in different shapes and sizes. The number of effects, adverse reactions, complications, and procedure time is low, which attracts the attention and interest of patients. Necessarily, these procedures must be performed by trained specialists, with knowledge in facial anatomy, to achieve the best and safest results. 1 The affordable cost of these protocols and their few side effects attract the attention of many people. Polydioxanone (PDO) threads are fine strands of suture threads that are inserted under the skin, producing a support effect that improves tissue sagging and stimulates collagen production, changing the density of the skin.
One of the main characteristics or anatomical manifestations of aging is the deepening of the nasolabial fold with reduction of malar enhancement, caused by sagging of the midface. 2 Forehead wrinkles are the result of frontalis muscle contracture and the skin aging process. The most commonly used procedures for the correction of these wrinkles are hyaluronic acid filler and botulinum toxin. 3 There are few reports of complications with this procedure in the bibliographic databases. The only reported case has been a procedure performed by non-medical professionals, with very little training and knowledge of human anatomy. The most recent case report states that the main complications that could occur after this procedure are dimpling, thread exposure, alopecia, under-correction, asymmetry, and injury to the parotid gland. All these consequences and reactions are mild to moderate in intensity, and they can be corrected by a simple procedure. 4 The most commonly reported minor complications are postoperative hematoma, infection, and temporary sensory/motor impairment. 2 Currently, there are few scientific studies on the use of threads in aesthetic protocols. Physicians are just beginning to know the effect of aesthetic procedures performed with PDO threads. Some have had good experiences and results, others have not. Therefore, it is necessary to review each of the experiences that have been reported in the scientific literature.
This review will answer some questions about the use of PDO threads in aesthetic facial rejuvenation procedures.

| ABOUT A C A S E ( WHI CH IN S PIRED THIS LITER ATURE RE VIE W )
A 54-year-old female patient consulted because she wanted to improve the appearance of her face, she had not felt comfortable for several years, and her birthday was approaching. During the evaluation, deep nasolabial folds, marionette lines, and very marked jowls were evident. The patient wanted a treatment that would not generate too much disability but with good results. Taking into account what the patient wanted, a non-surgical treatment with PDO spiculated threads was suggested. In a single session, eight PDO spiculated threads were used: four in each hemiface (three bidirectional threads of 15 cm with cannula 18G type W and a multidirectional thread of 15 cm with cannula 18G type W). Previously, the assessment and marking of the vectors for the application of the wires was performed (Figure 1). Asepsis and antisepsis of the area to be treated was performed with chlorhexidine. Anesthesia (lidocaine with 2% epinephrine) is applied in the entry points, which is then approached with a 18G needle, using only the bevel. Then, the PDO threads mounted on cannulas are inserted in the subcutaneous plane, in the direction of the respective vectors, later, the cannula is removed, leaving the threads in the tissue. They are tractioned and knotted, the ends of the threads without spicules are cut with a number 15 scalpel, while the ends of the threads with spicules are re-canulated. There were no complications, only slight pain in the treated area and appliques mainly in the area of the caudal cephalic vector, remission of such applique was observed after 2 weeks. Very noticeable results of improvement were seen at the end of the procedure ( Figure 2).  Their main effect is to stimulate the production of collagen and elastin by fibroblasts. They also have a minor indirect tensor effect as a result of the skin renewal they create. Some of these threads contain spicules on their sides and can also have a direct tensor effect.

| ME THODOLOGY
The most commonly used rejuvenation techniques include chemical peels, skin rhytidectomy, laser resurfacing, dermal filler injection, neurotoxins, and invasive surgical procedures. Patients with brow ptosis, appearance of jowls, and more prominent nasolabial folds are seeking non-invasive, safe, short downtime facial rejuvenation procedures such as PDO thread lifting.

| Clinical studies of facial rejuvenation with PDO threads
A clinical case report of a 52-year-old patient shows the efficacy and effectiveness of this rejuvenation technique. Polydioxanone threads were used to lift the lower third of the patient's face; in this case, fillers were also used to complement the results. Often, when the tissue is lifted, volume loss is revealed, which is commonly corrected with dermal fillers. This procedure lasted 30 min, and, immediately, there was slight swelling at the insertion points and in the treatment area, which subsided in 7 days. There was no bruising, and, 7 months later, the effect of the aesthetic procedure was still evident. 7 Likewise, other authors claim that, thread rejuvenation pro- Another study, led by Korean researchers, concludes that PDO threads are effective in rejuvenating aging skin, soft tissue retraction, and support, showing fewer complications. It also suggests that treatment with thicker threads may be a more effective procedure, however, to validate the latter claim, the study investigators recommend further research. 9 In India, research with PDO threads has also been carried out.
In this opportunity, a case report evaluating the effect of the use of the PDO thread technique combined with dermal fillers. The results show that the combined use of PDO threads and dermal fillers is an effective technique for facelifts and sagging correction. Significant improvement is observed within 1 week of the procedure, ensuring a high degree of patient satisfaction. 10 Another fundamental aspect, which has been evaluated, is the  This study provides a new paradigm for a more logical implantation pattern in PDO spiculated threads for facial rejuvenation. By generating multiple controlled crisscross patterns, a more intense fibrogenesis can be created, reducing the tension applied to each spiculated thread and, therefore, extending the duration of the result. In the search for information on the safety of the threads, a study by South Korean researchers concluded that the use of PDO threads for midface lift is simpler, faster, and less invasive than the use of conventional surgical methods, and this technique shows successful results for, approximately, 6 months.

| Doppler ultrasound: a technique that minimizes insertion mistakes
Renowned aesthetic procedure researchers from South Korea demonstrated, in their study, that Doppler ultrasound can be used to detect the FBrSTA (superficial temporal artery) in the temple area to avoid vascular complications during a thread lift. This study was performed on 50 patients (45 women and 5 men). Most studies of PDO threads for facial rejuvenation have focused on the material, vectors, or potential complications. The authors of this study sought to clarify appropriate guidelines for entry points for thread lifting, considering the relationship to the FBrSTA, as the ideal lifting vector is considered to pull the skin in the temple area where the FBrSTA is located. In this study, no vascular complications were observed in any patient.
Doppler ultrasound could detect FBrSTA in the temple area, and, thus, many vascular complications in the thread lift would be avoided. 13 Only this example of the use of ultrasound as a technique for the correct insertion of PDO threads was found. With this finding, the methodological gap is evident, and the scientific community is invited to carry out robust studies on the use of techniques, equipment, and tools for the correct and safe insertion of PDO threads.

| Replacement of PDO (polydioxanone) threads with PCL (polycaprolactone) threads
There are several types of threads for facial rejuvenation treatments. Among them, we find monofilament or smooth threads, and This indicates that TGFβ signal transduction leads to fibroblast proliferation that stimulates collagen formation and tissue reformation. In contrast, only type 3α1 collagen increased in the PCL thread group. 15

| Other current uses for polydioxanone threads (PDO)
In addition to facelifts, PDO threads are also used for non-surgical rhinoplasty. Currently, rhinoplasty in Korea has focused on nasal tip augmentation, which is considered a primary aspect of achieving a natural and balanced nose. Researchers from the Catholic University of Korea conducted a study whose main objective was to describe a novel technique using PDO threads in non-surgical rhinoplasty. They also attempted to evaluate the overall safety and efficacy of non-surgical rhinoplasty combining fillers and threads. The results demonstrated that nonsurgical rhinoplasty combining PDO threads and fillers can be safe and effective, and these results have a duration of 6 months. 16 Recently, PDO threads have been used for cosmetic procedures in body parts other than the face. In the United States, PDO threads were used after a liposuction procedure to improve the shape of the navel position, to permanently tighten the lower abdomen, and to redefine liposuction. The results were very satisfactory ( Figure 3; Table 1). Restoration/rejuvenation of the abdomen was achieved and revealed an improved overall body shape and proportion. 17

| DISCUSS ION
Information on scientifically rigorous studies on the use of threads is very scarce, and most of the found sources correspond to research  (PCL), poly L-lactic acids (PLLA), and polydioxanone (PDO). 14 Only in this study was it possible to compare the types of threads that exist, their effects, and duration. In accordance, a call is made to the scientific community with expertise in this type of aesthetic procedures to propose research to compare the effect of the different threads on the skin. There is also no evidence of studies in groups of patients with different age ranges. It would be interesting to evaluate the results of these procedures in different age groups.

| CON CLUSS I ONS
The

CO N FLI C T O F I NTE R E S T S TATE M E NT
None.

DATA AVA I L A B I L I T Y S TAT E M E N T
Data sharing not applicable to this article as no datasets were generated or analyzed during the current study.

E TH I C S S TATEM ENT
No ethics review board approval was utilized for this literature review.