Comparison of single versus dual vector technique using facial suspension threads a cadaveric study using skin vector displacement analysis

Comparison of Single- Versus Dual-Vector Technique Using Facial Suspension Threads: A Cadaveric Study Using Skin Vector Displacement Analysis Steven Liew, MD,* Konstantin Frank, MD,† Jack Kolenda, MD,‡ Martin Braun, MD,x and Sebastian Cotofana, MD, PhD║ BACKGROUND Facial suspension threads have been successfully used for facial soft-tissue repositioning When using facial suspension threads, it is unclear which technique and/or material has the greatest lifting effect for the middle and lower face or which technique/material best reduces the appearance of the jowls Material and Methods Three female and male cephalic specimens of Caucasian ethnicity (65.2 8.3 years; 20.72 2.6 kg/m2) were analyzed in an upright secured position Polydioxanone and polycaprolactone bidirectional barbed facial suspension threads were introduced by an 18 G, 100 mm cannula The single-vector technique aimed toward the labiomandibular sulcus, and the dual-vector technique aimed toward the labiomandibular sulcus and the mandibular angle Computation of vertical lifting, horizontal lifting, and volume reduction at the jowls and along the jawline were calculated using 3D imaging RESULTS The dual-vector technique effected a greater vertical lifting effect (4.45 2.78 mm vs 2.99 2.23 mm) but a reduced horizontal lifting effect (0.33 1.34 mm vs 0.49 1.32 mm) The dual-vector technique effected less volume reduction at the jowls 0.32 0.24 cc versus 0.41 0.46 cc and less volume reduction along the jawline 0.46 0.48 cc versus 0.87 0.53 cc (dual-vector vs single-vector) CONCLUSION This study provides evidence resulting from cadaveric observations for the overall nonsuperiority of the dual-vector technique compared with the single-vector technique The authors declared no potential conflicts of interest with respect to the research, authorship, and publication of this article S Liew and K Frank contributed equally to this work F acial suspension threads are specially designed medical sutures aimed to suspend and lift facial tissue through a minimally invasive approach They have been shown to create facial soft-tissue lifting and repositioning with a low risk of complications, minimal procedure, and recovery time.1,2 This noninvasive modality is expected to have the fastest growth rate in the aesthetic segment in the United States over the next years.3 One reason for its increase in popularity is its low costs, less down time, perceived less invasive nature, and lower costs compared with (invasive) surgical face-lifting procedures.1,2 The material of the suspension threads varies between resorbable and nonresorbable materials, but to date, most of the resorbable materials are either polydioxanone (PDO) or polycaprolactone (PCL).4 Another characterizing factor of facial suspension threads is the anchoring modality The thread can be *Shape Clinic, Sydney, Australia; †Department for Hand, Plastic and Aesthetic Surgery, Ludwig—Maximilian University Munich, Germany; ‡Department of Otolaryngology, University of Toronto, Toronto, Canada; xVancouver Laser & Skin Care Centre, Vancouver, Canada; ║Department of Clinical Anatomy, Mayo Clinic College of Medicine and Science, Rochester, Minnesota Supplemental digital content is available for this article Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.dermatologicsurgery.org) © 2020 by the American Society for Dermatologic Surgery, Inc Published by Wolters Kluwer Health, Inc All rights reserved ISSN: 1076-0512 Dermatol Surg 2020;46:1721–1727 DOI: 10.1097/DSS.0000000000002574 · · 1721 © 2020 by the American Society for Dermatologic Surgery, Inc Published by Wolters Kluwer Health, Inc Unauthorized reproduction of this article is prohibited EFFECTIVENESS OF SINGLE- VERSUS DUAL-VECTOR TECHNIQUE barbed unidirectional, bidirectional, or multidirectional or knotted which provides stability for the anchoring cones.4 These suspension threads are classically positioned at the level of the superficial muscoloaponeurotic system (SMAS) A retrospective analysis of 160 patients (136 women and 24 men) underwent facial lifting procedures using barbed PDO suspension threads reported that the most frequently observed complication was superficial displacement with 11.2% (n = 18), followed by erythema 9.4% (n = 15) and skin dimpling 6.2% (n = 10).1 The overall complication rate in that study was 34.4% (n = 55), and it was commented that this could have been due to the used insertion technique or material sterility.2 Comparing this new but rapidly growing field in the aesthetic segment to the field of soft-tissue filler injections, it can be observed that experimental or cadaveric validation studies are missing and that there is a paucity of data providing robust evidence for technique effectiveness or complication management.5–15 To date, it is unclear which technique and/or material has the greatest lifting effect of the middle and lower face To address this question, we conducted an experimental cadaveric split-face study and compared the single-vector versus dualvector insertion technique using PDO and PCL suspension threads for their effectiveness in facial softtissue repositioning Material and Methods Study Sample Three female and male cephalic specimens of Caucasian ethnicity with a mean age of 65.2 8.3 years (range: 55–74 years) and a mean body mass index of 20.72 2.6 kg/m2 were included in this experimental study The cephalic specimens were screened and not included into this analysis if previous facial surgery, trauma, or diseases disrupted the integrity of facial anatomy, especially the facial soft tissues 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 ethical standards of the country where the study was conducted 1722 Facial Suspension Thread Materials Two different types of absorbable facial suspension threads were used on either the left or the right facial side of the same specimen to investigate the difference in effectives of the single-vector versus the dual-vector technique On the left side (random choice), a PDO bidirectional barbed facial suspension thread was used, introduced by a 18 G, 100 mm cannula, and on the right side (random choice), a PCL bidirectional barbed facial suspension thread was used, introduced likewise by a 18 G, 100 mm cannula Insertion Techniques The head of each body donor was positioned and secured in an upright position to account for the effects of gravity (Figures and 2) The same techniques for the left and for the right side of the face were applied First, the threads directed toward the labiomandibular sulcus intended for jowl treatment (anterior vector) were positioned on both sides of the face, followed by the threads directed to the mandibular angle (posterior vector) intended for jawline contouring The anterior threads were introduced through a dermal access puncture cm anterior and cm superior to the mid portion of the zygomatic arch The 18 G, 100 mm cannula was advanced in the SMAS in the direction of the labiomandibular sulcus The superior (more anteriorly positioned) cannula aimed for a position cm posterior and cm inferior to the corner of the mouth lateral to the labiomandibular sulcus The inferior (more posteriorly located) cannula aimed for a point in the SMAS cm posterior and cm inferior to the corner of the mouth also lateral to the labiomandibular sulcus (Figure 1) The average trajectory of both threads was measured to be 69° The posterior threads were introduced through a dermal access puncture cm superior and exactly at the middle of the zygomatic arch (= cm posterior to the dermal access of the anterior vector) The cannula was advanced in the SMAS in the direction of the mandibular angle The more anteriorly located thread was directed to a point in the SMAS cm anterior and cm superior to the mandibular angle, whereas the posterior thread was DERMATOLOGIC SURGERY © 2020 by the American Society for Dermatologic Surgery, Inc Published by Wolters Kluwer Health, Inc Unauthorized reproduction of this article is prohibited LIEW ET AL horizontal skin displacement and in volume change of the jowls and along the jawline was determined as the effect of the dual-vector technique Figure Photograph showing the vector (black lines) of the posterior threads (A) A processed 3-dimensional scan showing the skin displacement vectors, represented with colored arrows, which were used for the consecutive analysis (B) aimed to a point cm anterior and cm superior to the mandibular angle (Figure 2) The average trajectory of both threads was measured to be 80° Values for skin displacement are calculated as x-coordinates and y-coordinates comparable to the x-axes and y-axes in a Cartesian coordinate system The skin displacement in the positive x-axis direction represents skin movement from the chin to the ear (= horizontal lifting), whereas skin displacement in the positive y-axis direction represents skin movement in the cranial direction (= vertical lifting) All surface analytic procedures were conducted by the same investigator (D.F.) (Figures and 4) Statistical Analyses After anchoring of the distal (inferior) segment of both threads, the cannula was removed, and the proximal (superior) segment of the thread was left free and external to the entry point The anchored distal facial soft tissues (jowls and jawline) were lifted and engaged with the proximal (superior) segment of the thread After the thread was tightly positioned in the facial soft tissue, the excess material was cut All procedures were performed by the first author of the study (S.L.) to reduce operator’s dependent and technique variation Imaging Procedure The image analysis procedures were conducted as previously described.16,17 3D images of the faces were taken by using a Vectra H1 camera system (Canfield Scientific Inc., Fairfield, NJ) The first 3D image was taken at baseline that is before any facial suspension thread was placed The second 3D image was taken after the anterior threads directed to the labiomandibular sulcus were positioned on both sides of the face The difference in vertical and horizontal skin displacement and in volume change at the labiomandibular sulcus and along the jawline between the first and the second 3D image was determined as the effect of the single-vector technique The third 3D image was taken after the posterior threads (in addition to the anterior threads) directed to the mandibular angle were positioned on both sides of the face The difference to baseline in vertical and Skin displacement of the lateral face and volume changes of the jowls and along the jawline was computed Differences in vertical and horizontal skin displacement and volume changes of the jowls and along the jawline were calculated comparing single-vector versus dual-vector effects using a paired t-test and comparing the difference between the used materials (= facial sides) using an independent sample t-test Because of the small sample size (n = 5), paired and independent sample statistic calculations were performed using the bootstrapping method based on 1,000 bootstrap samples All analyses were performed using SPSS Statistics 23 (IBM, Armonk, NY), and results were considered significant at a probability level of #0.05 Results are presented with the biascorrected and accelerated 95% bootstrap interval (BCa 95% confidence interval [CI]).18,19 Results Difference Between Thread Materials Using the Single-Vector Technique The vertical lifting effect of the PDO threads with the single-vector technique (cranial skin displacement and positive y-axis values) averaged at 4.00 2.69 mm; BCa 95% CI 1.79–6.44, whereas the vertical lifting effect using PCL threads was 1.97 1.17 mm; BCa 95% CI 1.04–2.96 with p = 162 (See Supplemental Digital Content 1, Figure S1, http:// links.lww.com/DSS/A431) The horizontal lifting 46:12:DECEMBER 2020 1723 © 2020 by the American Society for Dermatologic Surgery, Inc Published by Wolters Kluwer Health, Inc Unauthorized reproduction of this article is prohibited EFFECTIVENESS OF SINGLE- VERSUS DUAL-VECTOR TECHNIQUE Figure Photograph showing the vector (black lines) of anterior threads (A) A processed 3-dimensional scan showing the skin displacement vectors, represented with colored arrows, which were used for the consecutive analysis (B) effect (posterior skin displacement towards the ear, positive x-axis values) was for the PDO threads 0.98 0.93 mm; BCa 95% CI 0.22–1.79, whereas it was 1.36 0.41 mm; BCa 95% CI 1.05–1.71 for the PCL threads with p = 426 (See Supplemental Digital Content 1, Figure S2, http://links.lww com/DSS/A431) Reduction in volume of the jowls was 0.51 0.30 cc; BCa 95% CI 0.75–0.22 cc using PDO threads and was 0.30 0.59 cc; BCa 95% CI 0.29–0.65 cc using PCL threads with p = 499 (See Supplemental Digital Content 1, Figure S3, http:// links.lww.com/DSS/A431) Volume reduction along the jawline was 0.96 0.43 cc; BCa 95% CI 0.56–1.26 cc using PDO threads and 0.77 0.65 cc; BCa 95% CI 0.15–1.34 cc using PCL threads with p = 603 (See Supplemental Digital Content 1, Figure S4, http://links.lww.com/DSS/A431) Difference Thread Material Using the DualVector Technique The vertical lifting effect of the PDO threads with the dual—vector technique was 4.08 2.60 mm; BCa Figure A processed 3-dimensional scan showing the cadaveric specimen after placement of both anterior and posterior threads (A) The vertical and horizontal displacement was assessed within the blue encircled area (B) using colored vectors and (C) shows the scatter plot of the vertical and horizontal skin displacement 1724 95% CI 1.74–6.16 and was 4.83 3.20 mm; BCa 95% CI 2.03–7.52 for the PCL threads with p = 694 (See Supplemental Digital Content 1, Figure S1, http://links.lww.com/DSS/A431) The horizontal lifting effect was 1.10 0.01 mm; BCa 95% CI 0.57–1.71 for the PDO threads and 1.08 0.94 mm; BCa 95% CI 0.32–1.85 for the PCL threads with p = 968 (See Supplemental Digital Content 1, Figure S2, http://links.lww.com/DSS/A431) Volume reduction of the jowls was 0.39 0.17 mm; BCa 95% CI 0.22–0.53 using PDO threads and 0.26 0.30 mm; BCa 95% CI 0.03–0.52 using PCL threads with p = 419 (See Supplemental Digital Content 1, Figure S3, http://links.lww.com/DSS/A431) Volume reduction along the jawline was 0.33 0.28 mm; BCa 95% CI 0.10–0.61 using PDO threads and was 0.59 0.63 mm; BCa 95% CI 0.03–1.07 using PCL threads with p = 414 (See Supplemental Digital Content 1, Figure S4, http:// links.lww.com/DSS/A431) Single-Vector Versus Dual-Vector Techniques Independent of the thread material used, the vertical lifting effect of the single-vector technique was 2.99 2.23 mm; BCa 95% CI 1.84–4.44, whereas the vertical lifting effect using the dual vector technique was 4.45 2.78 mm; BCa 95% CI 2.66–5.99 (p = 140) Using the single-vector approach, independent of the thread material used, horizontal lifting was 0.49 1.32 mm; BCa 95% CI 0.27–1.29, whereas for the dual-vector technique, it was 0.33 1.34 mm; BCa 95% CI 0.46–1.05 (p = 394) Volume reduction of the jowls was 0.41 0.46 cc; BCa 95% CI 0.12–0.63 using the singlevector technique and was 0.32 0.24 cc; BCa 95% Figure A processed 3-dimensional scan showing the volume change along the jawline (A) and at the marionette line (B) DERMATOLOGIC SURGERY © 2020 by the American Society for Dermatologic Surgery, Inc Published by Wolters Kluwer Health, Inc Unauthorized reproduction of this article is prohibited LIEW ET AL CI 0.18–0.48 using the dual-vector technique (p = 507) Volume reduction along the jawline was 0.87 0.53 cc; BCa 95% CI 0.58–1.17 using the single-vector technique and was 0.46 0.48 cc; BCa 95% CI 0.17–0.74 using the dual-vector technique (p = 064) Discussion The results of this experimental cadaveric split-face study revealed that none of the outcome measures, such as vertical lifting, horizontal lifting, and volume reduction, of the jowls and along the jawline were statistically significantly influenced by the suspension thread material (PDO or PCL) The dual-vector technique that is combined positioning of suspension threads positioned toward the labiomandibular sulcus and at the mandibular angle displayed a greater vertical lifting effect of the middle and lower face as compared with the singlevector technique that is suspension threads at the labiomandibular sulcus alone: 4.45 2.78 mm versus 2.99 2.23 mm (dual-vector vs single-vector) Interestingly, the dual-vector technique resulted in less horizontal lifting 0.33 1.34 mm versus 0.49 1.32 mm (dual-vector vs single-vector), less volume reduction of the jowls 0.32 0.24 cc versus 0.41 0.46 cc (dualvector vs single-vector), and less volume reduction along the jawline 0.46 0.48 cc versus 0.87 0.53 cc (dualvector vs single-vector) A strength of this study is that a standardized procedure with exactly the same parameters (same investigator, same material per facial side, same entry points, and same trajectory of the suspension threads) was conducted to evaluate the effectiveness of the procedures Another strength of this study is that study outcomes were objectively assessed using 3-D surface scanning.20–26 These measurements were based on a mathematic algorithm and are thus independent of observer subjectivity Another study strength is the upright donor positioning to account for gravity A supine positioning would result in laterally oriented gravitational effects, thereby reducing generalizability to real-life clinical scenarios A limitation of this study, however, is the small sample size consisting of only cephalic specimens from female and male Caucasian body donors A larger sample might have provided more robust data and might have eliminated outliers To account for the small sample size, which resulted in not normal distributed data samples, we conducted the bootstrap method based on 1,000 bootstrap samples for all calculated statistical analyses This enabled us to resample our data and to obtain normally distributed data samples for the tests performed.18,19,27 Another limitation includes the use of cadavers instead of living patients The cadaveric model was chosen to facilitate more accurate image analysis because the subjects were secured in an upright, fixed position during image acquisition In living individuals, facial expressions and posture changes influence skin position and skin light/shadow relationships, even when using a manual matching algorithm for the alignment of the 3D surface scans Every patient has different needs when addressing facial aging signs so patient recruitment using a standardized protocol is challenging; a standardized treatment algorithm using the same thread trajectory for prescribed facial regions may yield aesthetically unappealing results In a cadaveric model, protocol (as described above) can be used to obtain objective and standardized results A drawback inherent in cadaveric studies is that cadavers lack blood pressure, muscle tone, regular tissue pressure, have a different temperature than living individuals, and are older than most aesthetic patients (range: 55–74 years) The basic mechanism of action behind facial suspension threads is primarily mechanic and was reproduced in this cadaveric model Because of the mechanical material-tissue interaction through the barbed sutures facial tissues are first tightly secured to the suspension thread, repositioned to the new location and then anchored The placement of the thread at the SMAS level is important to improve the suspension capability of the barbs onto a fibrous layer, rather than a fatty layer with higher chance of cheese wiring This tissue repositioning has local and regional effects Using the single-vector technique, facial soft tissues of the medial and lateral midface are being repositioned closer to the entry point of the suture that is to the zygomatic arch 46:12:DECEMBER 2020 1725 © 2020 by the American Society for Dermatologic Surgery, Inc Published by Wolters Kluwer Health, Inc Unauthorized reproduction of this article is prohibited EFFECTIVENESS OF SINGLE- VERSUS DUAL-VECTOR TECHNIQUE Besides the vertical lifting component, the singlevector technique also had a horizontal lifting component as the suspension thread trajectory was 69° toward the labiomandibular sulcus As the additional vector of the dual-vector technique had a trajectory of 80°, no additional horizontal lifting effect was observed On the contrary, the vertically oriented lifting effect reduced the horizontal lifting effect of the single-vector technique because the soft tissues were moved cranially toward the applied suspension thread trajectory without having any additional horizontal lifting component (Figures and 2) Along with the above described local effects, regional effects were observed Due to tissue repositioning, a volume decrease in the lower face that is jowls and along the jawline was observed The volume reduction after the single-vector technique was 0.41 0.46 cc of the jowls and 0.87 0.53 cc Interestingly, after the insertion of the second vector directed toward the mandibular angle, volume in the lower face increased and the overall effect after the dualvector technique was reduced when compared with the single-vector technique: increase in jowls volume by 0.09 cc to 0.32 0.24 cc and along the jawline by 0.41 cc to 0.46 0.48 cc after the dual-vector technique These results are contradictory to the vertical lifting effect results, which reveal an additive effect of both suspension thread vectors However, this effect can be explained by the assumption that an increased vertical lifting effect (4.45 2.78 mm vs 2.99 2.23 mm [dual-vs single-vector]) results in a cranial displacement of mandibular soft tissue, which ultimately lead to a reduced volume reduction after the dual-vector technique It could be hypothesized that a greater cranial soft-tissue displacement results in a greater mandibular soft-tissue repositioning from inferior to superior to the jawline This could result in the observed volume increase after the dualvector technique The jawline soft tissues include the supraplatysmal jowl fat compartment,28 which has been shown to descend with aging and the subplatysmal deep fat located around the facial artery and vein at their mandibular crossing.13 The repositioning of these fat compartments might have a beneficial effect when neck contouring is targeted This was however not the objective of this study 1726 Future studies with a larger cadaveric sample size or conducted in living patients will need to address the emerging additional questions raised from the presented experiments Conclusion This study provides evidence resulting from cadaveric observations for the overall nonsuperiority of the dual-vector technique compared with the single-vector technique Using an upright cadaveric model and 3D imaging, it was revealed that no statistically significant difference between the used materials was observed The dual-vector technique had a greater vertical lifting effect (4.45 2.78 mm vs 2.99 2.23 mm) but a reduced horizontal lifting effect (0.33 1.34 mm vs 0.49 1.32 mm), less volume reduction of the jowls 0.32 0.24 cc versus 0.41 0.46 cc, and less volume reduction along the jawline 0.46 0.48 cc versus 0.87 0.53 cc (dual-vector vs single-vector) Future studies will be needed to objectively evaluate the effectiveness of aesthetic procedures using nonsubjective and reproducible outcome measures References Bertossi D, Botti G, Gualdi A, Fundarò P, et al Effectiveness, longevity, and complications of facelift by barbed suture insertion Aesthet Surg J 2019;39:241–7 Wu WTL Commentary on: effectiveness, longevity, and complications of facelift by barbed suture insertion Aesthet Surg J 2019;39:248–53 ReportBuyer Aesthetic Threads Market—Growth, Trends, and Forecast (2019–2024) Available from: https://www.reportbuyer com/product/5790917/aesthetic-threads-market-growth-trends-andforecast-2019-2024.html#free-sample Accessed August 13, 2019 Gülbitti HA, Colebunders B, Pirayesh A, Bertossi D, et al Thread-lift sutures: still in the lift? A systematic review of the literature Plast Reconstr Surg 2018;141:341e–347e Frank K, Freytag DL, Schenck TL, Green JB, et al Relationship between forehead motion and the shape of forehead lines-A 3D skin displacement vector analysis J Cosmet Dermatol 2019 [Epub 2019 July 8] Cotofana S, Lachman N Anatomy of the facial fat compartments and their relevance in aesthetic surgery J Dtsch Dermatol Ges 2019;17:399–413 Suwanchinda A, Webb KL, Rudolph C, Hladik C, et al The posterior temporal supraSMAS minimally invasive lifting technique using softtissue fillers J Cosmet Dermatol 2018;17:617–24 Cotofana S, Lachman N Arteries of the face and their relevance for minimally invasive facial procedures: an anatomical review Plast Reconstr Surg 2019;143:416–26 Pavicic T, Webb KL, Frank K, Gotkin RH, et al Arterial wall penetration forces in needles versus cannulas Plast Reconstr Surg 2019; 143:504e–512e DERMATOLOGIC SURGERY © 2020 by the American Society for Dermatologic Surgery, Inc Published by Wolters Kluwer Health, Inc Unauthorized reproduction of this article is prohibited LIEW ET AL 10 Cotofana S, Gotkin RH, Frank K, Koban KC, et al The functional anatomy of the deep facial fat compartments – a detailed imaging based investigation Plast Reconstr Surg 2019;143:53–63 20 Koban KC, Frank K, Etzel L, Schenck TL, et al 3D mammometric changes in the treatment of idiopathic gynecomastia Aesthet Plast Surg 2019;43:616–24 11 Rudolph C, Hladik C, Hamade H, Frank K, et al Structural gender dimorphism and the biomechanics of the gluteal subcutaneous tissue Plast Reconstr Surg 2019;143:1077–86 21 Koban KC, Cotofana S, Frank K Precision in 3-dimensional surface imaging of the face: a handheld scanner comparison performed in a cadaveric model Aesthet Surg J 2019;39:NP36–NP44 12 Moqadam M, Frank K, Handayan C, Hakami M, et al Understanding the shape of forehead lines J Drugs Dermatol 2017;16:471–7 13 Schenck TL, Koban KC, Schlattau A, Frank K, et al Updated anatomy of the buccal space and its implications for plastic, reconstructive and aesthetic procedures J Plast Reconstr Aesthet Surg 2018;71:162–70 14 Pavicic T, Frank K, Erlbacher K, Neuner R, et al Precision in dermal filling: a comparison between needle and cannula when using soft tissue fillers J Drugs Dermatol 2017;16:866–72 15 Ghannam S, Sattler S, Frank K, Freytag DL, et al Treating the lips and its anatomical correlate in respect to vascular compromise Facial Plast Surg 2019;35:193–203 16 Braun M, Frank K, Freytag DL, Gotkin RH, et al The influence of the insertion angle on middle and lower face tissue-mechanics when treating the nasolabial folds with facial suspension threads—an experimental split-face cadaveric study Facial Plast Surg 2020;36: 268–75 17 Casabona G, Frank K, Koban KC, Freytag DL, et al Lifting vs volumizing-The difference in facial minimally invasive procedures when respecting the line of ligaments J Cosmet Dermatol [Epub August 12, 2019] 18 Davison AC, Hinkley DV Bootstrap Methods and Their Application (1st ed) Cambridge, United Kingdom: Cambridge University Press; 1997 19 Chernick MR, LaBudde RA An Introduction to Bootstrap Methods with Applications to R (1st ed) Hoboken, NJ: Wiley; 2011 Available at: https://www.wiley.com/en-cc/An+Introduction+to+Bootstrap+ Methods+with+Applications+to+R-p-9780470467046 Accessed April 28, 2019 22 Koban K, Leitsch S, Holzbach T, Volkmer E, et al 3D Bilderfassung und Analyse in der Plastischen Chirurgie mit Smartphone und Tablet: eine Alternative zu professionellen systemen? Handchir Mikrochir Plast Chir 2014;46:97–104 23 Cotofana S, Koban CK, Frank K The surface-volume-coefficient of the superficial and deep facial fat compartments—a cadaveric 3D volumetric analysis Plast Reconstr Surg 2019;143:1 24 Frank K, Koban K, Targosinski S The anatomy behind adverse events in hand volumizing procedures Plast Reconstr Surg 2018;141: 650e–662e 25 Koban KC, Härtnagl F, Titze V, Schenck TL, et al Chances and limitations of a low-cost mobile 3D scanner for breast imaging in comparison to an established 3D photogrammetric system J Plast Reconstr Aesthet Surg 2018;71:1417–1423 26 Cotofana S, Koban K, Pavicic T, Yankonva M, et al Clinical validation of the surface volume coefficient for minimally invasive treatment of the temple J Drugs Dermatol 2019;18:533 27 Curran-Everett D Explorations in statistics: the assumption of normality Adv Physiol Educ 2017;41:449–53 28 Schenck TL, Koban KC, Schlattau A, Frank K, et al The functional anatomy of the superficial fat compartments of the face: a detailed imaging study Plast Reconstr Surg 2018;141:1351–9 Address correspondence and reprint requests to: Sebastian Cotofana, MD, PhD, Associate Professor of Anatomy, Department of Clinical Anatomy, Mayo Clinic College of Medicine and Science, Mayo Clinic, Stabile Building 9-38, 200 First Street, Rochester, MN, 55905, or e-mail: cotofana.sebastian@mayo.edu 46:12:DECEMBER 2020 1727 © 2020 by the American Society for Dermatologic Surgery, Inc Published by Wolters Kluwer Health, Inc Unauthorized reproduction of this article is prohibited  ... conducted an experimental cadaveric split-face study and compared the single- vector versus dualvector insertion technique using PDO and PCL suspension threads for their effectiveness in facial softtissue... repositioning Material and Methods Study Sample Three female and male cephalic specimens of Caucasian ethnicity with a mean age of 65.2 8.3 years (range: 55–74 years) and a mean body mass index of 20.72... patients (range: 55–74 years) The basic mechanism of action behind facial suspension threads is primarily mechanic and was reproduced in this cadaveric model Because of the mechanical material-tissue