Biomechanical and viscoelastic properties of skin,SMAS, and composite flaps as they pertain to rhytidectomy

Previous studies have focused on biomechanical and viscoelastic properties of the superficial musculoaponeurotic system (SMAS) flap and the skin flap lifted in traditional rhytidectomy procedures. The authors compared these two layers with the composite rhytidectomy flap to explain their clinical observations that the composite dissection allows greater tension and lateral pull to be placed on the facial and cervical flaps, with less long-term stress-relaxation and tissue creep. Eight fresh cadavers were dissected by elevating flaps on one side of the face and neck as skin and SMAS flaps and on the other side as a standard composite rhytidectomy flap. The tissue samples were tested for breaking strength, tissue tearing force, stress-relaxation, and tissue creep. For breaking strength, uniform samples were pulled at a rate of 1 inch per minute, and the stress required to rupture the tissues was measured. Tissue tearing force was measured by attaching a 3-0 suture to the tissues and pulling at the same rate as that used for breaking strength. The force required to tear the suture out of the tissues was then measured. Stress-relaxation was assessed by tensing the uniformly sized strips of tissue to 80 percent of their breaking strength, and the amount of tissue relaxation was measured at 1-minute intervals for a total of 5 minutes. This measurement is expressed as the percentage of tissue relaxation per minute. Tissue creep was assessed by using a 3-0 suture and calibrated pressure gauge attached to the facial flaps. The constant tension applied to the flaps was 80 percent of the tissue tearing force. The distance crept was measured in millimeters after 2 and 3 minutes of constant tension. Breaking strength measurements demonstrated significantly greater breaking strength of skin and composite flaps as compared with SMAS flaps (p < 0.05). No significant difference was noted between skin and composite flaps. However, tissue tearing force demonstrated that the composite flaps were able to withstand a significantly greater force as compared with both skin and SMAS flaps (p < 0.05). Stress-relaxation analysis revealed the skin flaps to have the highest degree of stress-relaxation over each of five 1-minute intervals. In contrast, the SMAS and composite flaps demonstrated a significantly lower degree of stress-relaxation over the five 1-minute intervals (p < 0.05). There was no difference noted between the SMAS flaps and composite flaps with regard to stress-relaxation. Tissue creep correlated with the stress-relaxation data. The skin flaps demonstrated the greatest degree of tissue creep, which was significantly greater than that noted for the SMAS flaps or composite flaps (p < 0.05). Comparison of facial flaps with cervical flaps revealed that cervical skin, SMAS, and composite flaps tolerated significantly greater tissue tearing forces and demonstrated significantly greater tissue creep as compared with facial skin, SMAS, and composite flaps (p < 0.05). These biomechanical studies on facial and cervical rhytidectomy flaps indicate that the skin and composite flaps are substantially stronger than the SMAS flap, allowing significantly greater tension to be applied for repositioning of the flap and surrounding subcutaneous tissues. The authors confirmed that the SMAS layer exhibits significantly less stress-relaxation and creep as compared with the skin flap, a property that has led aesthetic surgeons to incorporate the SMAS into the face lift procedure. On the basis of the authors' findings in this study, it seems that that composite flap, although composed of both the skin and SMAS, acquires the viscoelastic properties of the SMAS layer, demonstrating significantly less stress-relaxation and tissue creep as compared with the skin flap. This finding may play a role in maintaining long-term results after rhytidectomy. In addition, it is noteworthy that the cervical flaps, despite their increased strength, demonstrate significantly greater tissue creep as compared with facial flaps, suggesting earlier relaxation of the neck as compared with the face after rhytidectomy.     

Stretching and tissue expansion for rhytidectomy: an improved approach

Intraoperative expansion of the skin of the face supplies additional tissue that permits closure of the face lift incision with minimal tension. This paper presents the findings in rhytidectomy patients over the last 3 years using both intraoperative stretching and intraoperative stretching combined with tissue expansion utilizing the Man face lift expander. Sixty-seven patients underwent rhytidectomy surgery, of whom 50 were treated with stretching techniques alone and 17 were treated with the combined stretching and expansion method. The patients' ages ranged from 28 to 78 years. Results indicate that the patients treated with combined stretching and expansion had significantly more skin removed. This new technique appears to offer significant clinical advantages over usual face lifts.     

Reinforced orbitotemporal lift: contribution to midface rejuvenation

The changes in the aging face occur from progressive ptosis of the skin, fat, and muscle, in conjunction with bone absorption and cartilage atrophy. In the orbital region, hollowness and compartmentalization occur. Conventional face lift procedures correct only the skin flaccidity, and superficial musculoaponeurotic system techniques reposition the skin and platysma without repositioning the middle third of the face, creating an artificial jawline. Subperiosteal rhytidectomy disrupts the anatomy of the periorbita, which gives the patient a certain scarecrow aspect. Composite rhytidectomy associated with brow lift and blepharoplasty may offer better results, with improvement in the malar and orbital regions. The reinforced orbitotemporal lift (ROTEL) is a new procedure in a face lift that allows the orbicularis oculi muscle and all the structures connected to it to be elevated and stretched and the orbitotemporal skin to be raised, repositioning these structures and ending orbital compartmentalization. The result is an impressive improvement in the malar-orbitotemporal region, resulting in a natural and youthful appearance.     

Composite rhytidectomy.

Signs of aging in the face reflect the change in position of deep anatomic elements, which are the platysma muscle, cheek fat, and the orbicularis oculi muscle. These changes occur from progressive ptosis of these elements, which continue to keep their intimate relationship with each other throughout the aging process. Conventional face lift procedures disrupt this normal relationship by separating the skin from these elements. All SMAS techniques reposition only the platysma muscle without repositioning the cheek fat and orbicularis muscle. This composite rhytidectomy allows elevation of a composite musculocutaneous flap containing all three elements for repositioning while maintaining their intimate relationship with each other and with the skin. One-hundred and sixty-seven composite rhytidectomies have been done with impressive results and minimal complications.     

Endoscopic foreheadplasty: a histologic comparison of periosteal refixation after endoscopic versus bicoronal lift

Endoscopic brow lift techniques using temporary fixation rely on rapid readherence of the periosteum to calvarial bone. Little is known about the histologic events that occur during the early postoperative period after these procedures. An animal study was designed to compare and contrast periosteal fixation to bone and unelevated periosteum, with endoscopic and bicoronal brow lift techniques. One method of temporary fixation is the use of absorbable (polylactic/polyglycolic acid copolymer) LactoSorb screws; a histologic analysis of implanted LactoSorb screws was also performed. Sixteen rabbits underwent brow lifts; eight underwent endoscopic brow lift and fixation with LactoSorb screws without skin excision, and another eight underwent traditional bicoronal brow lift with skin excision and closure under tension. Animals were killed 1, 2, 6, and 12 weeks after the procedures were performed to evaluate the interaction of periosteum and bone and the normal, unelevated periosteum/calvarium interface at a site distant from the operative area. Histologic specimens were examined for the degree of apposition of periosteum to bone and for any fibrous or bony reaction at this interface. Histologic analysis showed various degrees of periosteal fibrosis and fixation to calvarial bone. After an initial phase of minimal periosteal adherence and moderate inflammation, the periosteum became progressively more adherent to bone in both groups, with no significant differences between treatment groups in rates of fixation. Fixation required at least 6 weeks. LactoSorb screws were surrounded by an area of mild inflammation and were progressively hydrolyzed and digested. Periosteal fixation increases over time for bicoronal and endoscopic brow lifts with minimal differences between the two techniques. With this animal model, periosteal adherence to calvarium requires at least 6 weeks with complete adherence by 12 weeks. In addition, the use of absorbable fixation screws seems to be both effective and well tolerated. The histologic changes associated with periosteal healing observed in this study suggest that permanent or semipermanent fixation may improve the accuracy and early postoperative maintenance of forehead advancement.     

A 5-year study of the transmalar subperiosteal midface lift with minimal skin and superficial musculoaponeurotic system dissection: a durable, natural-appearing lift with less surgery and recovery time

The transmalar subperiosteal midface lift is a simple, direct-approach procedure to be performed with a meloplasty. The entry into the midface is at the site of maximum suture tension, which allows for more elevation. The skin is elevated enough to expose the entry site, which is on the zygoma just cephalad to the origins of the zygomaticus muscles. Through a small hole at that site, a periosteal elevator is used for the midface dissection. This is a blind dissection, and the technique is described. The advantages of the technique are that there is (1) no lower-lid incision or risk of an ectropion, (2) a resultant tightening and elevation of the lower lid, (3) more elevation and durability because the zygomaticus muscle origins are elevated with the periosteum and are sutured to the very substantial deep temporal fascia, (4) a simple and fast procedure, and (5) no telltale sign of a face lift. Both the superficial musculoaponeurotic system (SMAS) and the skin are substantially elevated with the transmalar subperiosteal midface lift to the extent that they should be only minimally dissected. In the author's opinion, the extended dissection of the skin and/or the SMAS does not increase the amount of tissue lift and probably reduces it in most cases, considering that the goal is a natural look and not one that appears pulled or stretched. The skin is elevated only for exposure, and the SMAS is elevated only enough to create a preauricular SMAS-platysma flap to tighten the neck. With two fewer layers of dissection, there is significantly less postoperative swelling and recovery time. The article presents the technique, the results on 272 patients over a period of 5 years, and a discussion. No patients described have had secondary procedures such as lasers, so the transmalar subperiosteal midface lift can be evaluated on its own merit.     

Endoscopic brow lift: a retrospective review of 628 consecutive cases over 5 years

Since its introduction in 1992, endoscopic brow lift has gained tremendous recognition because it has been promoted as a novel technique to correct brow ptosis as well as glabella rhytids in a minimally invasive manner with fewer complications than the classic coronal brow lift method. In this retrospective study, 628 endoscopic brow lift procedures performed over a 5-year period (1997-2001) at Manhattan Eye Ear and Throat Hospital were reviewed. The number of endoscopic brow lift procedures performed at this institution has declined 70 percent. The purpose of this study was to elucidate the causes of this striking trend by soliciting the opinions of 21 New York plastic surgeons on their current brow ptosis management. The response rate was 84 percent (21 of 25 surgeons contacted). Currently, 25 percent of the interviewed plastic surgeons perform endoscopic brow lift regularly, 50 percent of the plastic surgeons perform endoscopic brow lift occasionally, and 25 percent of the participants no longer perform endoscopic brow lift. While most patients (70 percent) were satisfied with their results, only 50 percent of the plastic surgeons were pleased with the long-term results (after more than 2 years of follow-up). Observed postsurgical complications of endoscopic brow lift included alopecia, hairline changes, infected hardware, brow asymmetry requiring surgical revision, prolonged forehead/brow paresthesia, frontal branch nerve paralysis, and scalp dysesthesia. These complications were similar to those resulting from open brow lifts. Seventy-one percent of the surveyed New York plastic surgeons routinely administered botulinum toxin type A (Botox) within 6 months of the endoscopic brow lift procedure. Possible explanations for the decline in the overall number of endoscopic brow lift procedures include the following: (1) the selection criteria for the ideal endoscopic brow lift patients are currently more limited; (2) other techniques equal or surpass endoscopic brow lift in effectiveness and predictability; and (3) endoscopic brow lift is ineffective in the majority of patients. There is no single superior surgical procedure for brow ptosis management available at this time.     

Endoscopic forehead lift: review of technique,cases, and complications

Endoscopy has provided a significant improvement in the surgical rejuvenation of the upper face. It offers a minimally invasive alternative that avoids many of the undesirable effects associated with the coronal approach. The standard minimal access forehead endoscopic procedure consists of a subperiosteal undermining through three small triangular prehairline incisions. To successfully elevate the eyebrows, it is essential to release the periosteum at the level of the supraorbital rims and ablate the brow depressor muscles of the glabella. Until the periosteum reattaches itself, elevation is maintained by a temporary suspension suture between staples at the incision sites and 5 cm posterior to the hairline. The transverse closure of the triangular skin incisions achieves some additional elevation. The biplanar approach adds a partial subcutaneous undermining of the forehead to the endoscopic technique and allows plication of the frontalis muscle and excision of excess forehead skin. It is offered to patients with very ptotic eyebrows, deep transverse wrinkles, or a high forehead. The prehairline incision is a disadvantage but is tolerated quite well in older patients. The medical records of 393 consecutive patients who underwent endoscopic forehead lift from 1994 to 2000 were reviewed. Because seven patients had the endoscopic forehead lift repeated, the number of forehead endoscopies totaled 400. The complication rate was quite acceptable and did not markedly increase when a forehead lift was performed in combination with other facial procedures. The endoscopic forehead lift consistently attenuated the transverse forehead wrinkles, reduced the glabellar frown lines, and raised the eyebrows. It provided an appearance that was less tired and angry in addition to opening the area around the eyes. Long-term follow-up has shown that the endoscopic forehead lift produces lasting and predictable results.     

Tension decrease during skin stretching in undermined versus not undermined skin: an experimental study in piglets

In a controlled study using 15 piglets, the efficacy of skin stretching using a skin stretching device was tested by quantifying the tension decrease during skin stretching in undermined and not undermined wounds. The viability of the skin margins was examined in both situations. Thirty standardized wounds was created: around 15 wounds on one flank, the surrounding skin was undermined; whereas around the 15 wounds on the opposite flank, the surrounding skin was not undermined. The force required to close the 9 x 9 cm defect was measured at the beginning, after undermining, and after 30 minutes of skin stretching. Also examined was the wound healing after 1 day and 1 week. A tension decrease of 3.02 N (13.6 percent reduction of the total force that is required to close the wound at the beginning) was seen due to undermining the surrounding skin. Skin stretching for 30 minutes without undermining the skin showed a tension decrease of 6.10 N (26.5 percent). Therefore, the tension decrease due to skin stretching was twice as high in comparison with undermining the skin margins alone. This has been statistically proven to be significant (-d (difference) = 3.08, 95 percent confidence interval = 2.16; 4.00, p < 0.001). When the undermined skin of the wound was stretched for 30 minutes, we measured a total tension decrease of 7.60 N (34.1 percent). There was a statistically significant but small difference in total tension decrease as a result of undermining combined with skin stretching in comparison with skin stretching without undermining (-d = 1.51, 95 percent confidence interval = 0.77; 2.23, p < 0.001). Undermining the surrounding skin involved cutting musculocutaneous perforating vessels. Looking at the viability of the skin, seven wounds, all found in the undermined group, showed skin necrosis after 1 week. Excessive seroma formation was seen in all wounds around which the skin was undermined. In the not undermined wounds, there were no problems in wound healing. In conclusion, skin stretching for only 30 minutes using a skin stretching device significantly reduces wound closing tension. The additional advantage of skin stretching over that of undermining alone is clearly shown. Undermining the wound margins before skin stretching gives a small additional tension decrease but has well-known complications, such as skin-edge necrosis and seroma formation.     

Lip augmentation with superficial musculoaponeurotic system grafts: report of 103 cases.

Many patients suitable for a lip augmentation are of face lift age, and could benefit from a simultaneous lip enhancement during the rhytidectomy procedure. The healthy, live superficial musculoaponeurotic system (SMAS) tissue obtained from the face lift can be recycled and grafted with minimal additional operating time. From April of 1995 to January of 2000, 103 patients (99 women and four men) underwent a lip augmentation procedure by the senior author (N.L.) using SMAS grafts harvested from a simultaneous rhytidectomy. Indications for surgery were purely aesthetic in all 103 cases. The surgical technique used for the SMAS graft lip augmentation is as follows: Using a narrow tenotomy scissors, an intramuscular tunnel was created with blunt and sharp dissection across the lip. The graft, obtained from the posterior edge of the SMAS dissection, is left as long as possible, and is pulled through the tunnel with a tendon forceps. The lips are then stretched manually from the central point upward and downward, respectively. It is important to avoid suturing the ends of the graft into the closure; the grafts should be allowed to move freely, to avoid postoperative tethering on smiling or mouth opening.Most patients expressed some initial concern with their early appearances caused mainly by the swelling. By 2 weeks, most patients were extremely pleased with the size and shape, and their main concern was that the lip fullness would shrink even more. By 3 to 4 weeks, shrinkage largely ceased and the correction remained for varying periods, some as long as 5 years. A sampling of the results was obtained by means of a questionnaire mailed to all patients having undergone the SMAS graft lip augmentation. Fifty-four patients (52 percent) returned the questionnaire with their responses. Of those who responded to the survey, 42 patients (78 percent) reported fuller lips than before their operation. Significantly, 11 of 14 patients (79 percent) followed up after 24 months postoperatively reported fuller lips and excellent or good results. Complications and unsatisfactory results were very rare, occurring generally at the beginning of the learning curve of the series.SMAS grafts are useful for long-lasting lip augmentation, producing a youthful appearance by adding natural, soft roundness and fullness to lips without the artificial look and feel of synthetic material.     

Improved repair of dermal wounds in mice lacking microRNA‐155

Wound healing is a well-regulated but complex process that involves haemostasis, inflammation, proliferation and maturation. Recent reports suggest that microRNAs (miRs) play important roles in dermal wound healing. In fact, miR deregulation has been linked with impaired wound repair. miR-155 has been shown to be induced by inflammatory mediators and plays a central regulatory role in immune responses. We have investigated the potential role of miR-155 in wound healing. By creating punch wounds in the skin of mice, we found an increased expression of miR-155 in wound tissue when compared with healthy skin. Interestingly, analysis of wounds of mice lacking the expression of miR-155 (miR-155^−/−) revealed an increased wound closure when compared with wild-type animals. Also, the accelerated wound closing correlated with elevated numbers of macrophages in wounded tissue. Gene expression analysis of wounds tissue and macrophages isolated from miR-155^−/− mice that were treated with interleukin-4 demonstrated an increased expression of miR-155 targets (BCL6, RhoA and SHIP1) as well as, the finding in inflammatory zone-1 (FIZZ1) gene, when compared with WT mice. Moreover, the up-regulated levels of FIZZ1 in the wound tissue of miR-155^−/− mice correlated with an increased deposition of type-1 collagens, a phenomenon known to be beneficial in wound closure. Our data indicate that the absence of miR-155 has beneficial effects in the wound healing process.     

Refinements in face lifting: enhanced facial contour using vicryl mesh incorporated into SMAS fixation

As we have gained experience with the extended superficial musculoaponeurotic system (SMAS) technique in face lifting, refinements in our procedure have led to increased consistency in results. The important factors that have led to our technical modifications include the following: (1) the significance of the retaining ligaments of the midface, which determine the degree of surgical dissection required for both skin and SMAS in rhytidectomy; (2) the changes in facial shape that occur with aging, secondary to the descent of facial fat; (3) the possibility of modifying facial shape through the repositioning of facial fat in an extended SMAS face lift; (4) the improved longevity of result to be obtained by incorporating Vicryl mesh into SMAS fixation; (5) the artistic nuances of incision design that help to minimize scar perceptibility. Understanding these factors enables surgeons to use the extended SMAS technique successfully with more challenging cases, enhancing facial appearance while minimizing signs that the patient has undergone a surgical procedure.     

National plastic surgery survey: brow lifting techniques and complications.

The purpose of this survey was to assess trends in brow lifting philosophy, techniques, and complications. This is the second of a three-part survey; the first part reported on complications with face lift techniques, and the final report will address practice management issues, including facility and ancillary procedures. Surveys were sent to 3800 members of the American Society of Plastic Surgeons; the response rate was 15 percent. This survey represents data on 6951 brow lifts, of which approximately 50 percent were performed endoscopically and 50 percent with a coronal incision. Several conclusions about the practice of the respondents were reached: (1) Both brow lift techniques were considered to be effective. (2) Surgeons considered coronal brow lifting to be more effective for the three basic goals of brow lifting: brow elevation, reduction of transverse lines, and reduction of glabellar lines. (3) Reported complication rates for both techniques were low, and the most frequent complication was alopecia (varying from 2.9 percent to 4 percent). (4) Patient satisfaction varied from 98.2 percent to 99.2 percent. (5) Major complications were rarely reported.     

The SMAS and the nasolabial fold.

In a series of histologic sections and clinical and cadaver dissections, the superficial musculoaponeurotic system (SMAS) is seen to become the investing fascia of the zygomaticus major and minor muscles in the medial cheek. The pull on the cheek flap during rhytidectomy is diffused by the attachment of the SMAS to these muscles. I believe that this attachment accounts for the minimal change in the nasolabial crease after a Skoog-type sub-SMAS face lift.     

Rhytidectomy and the nasolabial fold.

I describe a technical modification in the Skoog face lift procedure that releases the deep attachments of the SMAS to the muscles of facial expression for maximal mobility of the medial cheek yet elevates the cheek flap as a composite of skin, subcutaneous tissue, and SMAS to enhance skin perfusion. My results with the procedure in 100 patients are analyzed by using functional zones of the nasolabial fold corresponding to underlying musculature and a simple grading system based on preoperative and postoperative photographs. Marked improvement in the nasolabial fold was noted in over 80 percent of patients by 6 and 12 months postoperatively. This effect seemed to last up to 4 years.     

Stretching skin: undermining is more important than intraoperative expansion

The efficacy of intraoperative expansion in reducing the tension of wound closure was tested in young pigs. The young piglet as a model for studying human skin was characterized by finding a close similarity between the modulus of elasticity of young piglet skin and human abdominoplasty and mammaplasty skin (range 12.8 to 23.7 N/mm2 for piglet skin, 14.3 to 19 N/mm2 for human skin). The tension required to close a standardized wound was determined before undermining, after undermining, and finally after intraoperative expansion. These measurements were performed in 10 young pigs with an average weight of 11.5 kg. Undermining the wound edges resulted in a significant decrease in the force required to close the wounds (p less than 0.0001). Intraoperative expansion did not significantly decrease the tension. Previous work showing the importance of site and direction of pull on the tension for wound closure was confirmed in this study. Analysis of variance demonstrated that the tension required to close a standard wound is greater high on the pig's back than near the belly and near the shoulder as opposed to the hip for midflank wounds (p less than 0.0001). Increasing the extent of undermining from 62 to 136 cm2 significantly decreased the tension for wound closure (p less than 0.05). Further undermining did not result in a significant decrease in wound closure tension. In this model, intraoperative expansion offers no advantage over simple undermining. We suggest that the benefit reported by clinicians using intraoperative expansion may derive from an increase in the extent of undermining required to place expanders under the wound margins.     

Integrin-linked kinase (ILK) modulates wound healing through regulation of hepatocyte growth factor (HGF)

Integrin-linked kinase (ILK) is an intracellular effector of cell–matrix interactions and regulates many cellular processes, including growth, proliferation, survival, differentiation, migration, invasion and angiogenesis. The present work analyzes the role of ILK in wound healing in adult animals using a conditional knock-out of the ILK gene generated with the tamoxifen-inducible Cre-lox system (CRE-LOX mice). Results show that ILK deficiency leads to retarded wound closure in skin. Intracellular mechanisms involved in this process were analyzed in cultured mouse embryonic fibroblast (MEF) isolated from CRE-LOX mice and revealed that wounding promotes rapid activation of phosphatidylinositol 3-kinase (PI3K) and ILK. Knockdown of ILK resulted in a retarded wound closure due to a decrease in cellular proliferation and loss of HGF protein expression during the healing process, in vitro and in vivo. Alterations in cell proliferation and wound closure in ILK-deficient MEF or mice could be rescued by exogenous administration of human HGF. These data demonstrate, for the first time, that the activation of PI3K and ILK after skin wounding are critical for HGF-dependent tissue repair and wound healing.     

Intraoperative tissue expansion in rhytidectomy revisited

Intraoperative tissue expansion is an adjunct that has been used during rhytidectomy to rejuvenate the face and neck. This technique has been thought to allow for additional skin resection and, thus, increased skin tightening during rhytidectomy. The stretch of the skin by expansion should allow for additional skin resection before closure. Also, when the force of the underlying expander is removed, the expanded skin would recoil and the advancement of the flap should become tighter, with improved results. The technique achieved some popularity a few years ago but has received little recent attention. In this study, the authors attempted to compare face-lift results of adjunctive intraoperative tissue expansion during rhytidectomy with similar techniques without intraoperative expansion. The results of 50 female patients who underwent rhytidectomy for midface rejuvenation by a single operating surgeon composed the study group. Twenty-five of the patients had undergone rhytidectomy that addressed the cheek, chin, and neck areas without expansion (nonexpanded rhytidectomy group). The other 25 patients (expanded rhytidectomy group) had adjunctive intraoperative tissue expansion performed with the rhytidectomy. A tissue expander was temporarily placed beneath the rhytidectomy flaps on each side and expanded in a standard manner before final skin resection and closure. Frontal and lateral photographs were evaluated by 54 examiners. Preoperative and postoperative photographs of the 50 patients were viewed side-by-side by the examiners. The patients were presented in blind fashion and random order. The examiners graded the results of each patient on a scale of improvement from 1 to 10, with 10 being the maximum level of improvement. The scores were recorded and statistically evaluated by using the two-sample test. Evaluation of the examiners' scores showed that the mean rating given to patients in the expanded rhytidectomy group was 5.07 (SD = 1.12). The mean rating for the nonexpanded rhytidectomy group was 5.27 (SD = 1.57). When the two groups were compared using the two-sample test, the difference between the two was not statistically significant (p = 0.6127). Intraoperative tissue expansion as an adjunct to rhytidectomy did not result in improved facial rejuvenation in this patient series. The authors' impression is that the benefits of tissue expansion do not justify the added expense, time, and risks associated with using tissue expansion during rhytidectomy.     

Topical application of ALK5 inhibitor A-83-01 reduces burn wound contraction in rats by suppressing myofibroblast population

Burn scar contracture that follows the healing of deep dermal burns causes severe deformation and functional impairment. However, its current therapeutic interventions are limited with unsatisfactory outcomes. When we treated deep second-degree burns in rat skin with activin-like kinase 5 (ALK5) inhibitor A-83-01, it reduced wound contraction and enhanced the area of re-epithelialization so that the overall time for wound closing was not altered. In addition, it reduced myofibroblast population in the dermis of burn scar with a diminished deposition of its biomarker proteins such as α-SMA and collagen. Treatment of rat dermal fibroblast with A-83-01 inhibited transforming growth factor-β1 (TGF-β1)-dependent induction of α-SMA and collagen type I. Taken together, these results suggest that topical application of ALK5 inhibitor A-83-01 could be effective in preventing the contraction of burn wound without delaying the wound closure by virtue of its inhibitory activity against the TGF-β-induced increase of myofibroblast population.     

A morphoelastic model for dermal wound closure

We develop a model of wound healing in the framework of finite elasticity, focussing our attention on the processes of growth and contraction in the dermal layer of the skin. The dermal tissue is treated as a hyperelastic cylinder that surrounds the wound and is subject to symmetric deformations. By considering the initial recoil that is observed upon the application of a circular wound, we estimate the degree of residual tension in the skin and build an evolution law for mechanosensitive growth of the dermal tissue. Contraction of the wound is governed by a phenomenological law in which radial pressure is prescribed at the wound edge. The model reproduces three main phases of the healing process. Initially, the wound recoils due to residual stress in the surrounding tissue; the wound then heals as a result of contraction and growth; and finally, healing slows as contraction and growth decrease. Over a longer time period, the surrounding tissue remodels, returning to the residually stressed state. We identify the steady state growth profile associated with this remodelled state. The model is then used to predict the outcome of rewounding experiments designed to quantify the amount of stress in the tissue, and also to simulate the application of pressure treatments.