Relaxed skin tension lines (RSTL) versus other skin lines

The seven best known skin tension lines are presented. The directions they convey are schematically compared with those of the relaxed skin tension lines. Commentaries and discussion by the author are given in order to help the reader arrive at his or her own conclusions on which directions his or her incisions should take so as to obtain the best scarring.     

Treatment of facial wounds with botulinum toxin A improves cosmetic outcome in primates

Surgeons have constantly sought to achieve the most aesthetic scar. A major factor determining the final cosmetic appearance of a cutaneous scar is the tension acting on the wound edges during the healing phase. Since Theodor Kocher pioneered the alignment of skin incisions with Langer's lines in 1892, surgical techniques that attempt to overcome closing tension have become standard. Yet, no treatment has been available to minimize underlying muscle contractions, which are the major cause of this tension. Botulinum toxin A is a potent drug that produces temporary muscular paralysis when injected locally. It has proven to be safe and effective in the treatment of a variety of disorders, including hyperkinetic facial lines. The objective of this randomized, double-blind, placebo-controlled primate study was to investigate the efficacy of a single injection of botulinum toxin A to improve the cosmetic appearance of cutaneous scars. Symmetric pairs of standardized excisions were performed on either side of the forehead of six primates. The half foreheads were randomized to the botulinum toxin A treatment side versus the placebo injection side. A panel of three blinded facial surgeons assessed the cosmetic appearance of the mature scars 3 months postoperatively. The wounds that had been immobilized with botulinum toxin A were rated as significantly better in appearance than the control wounds (p < 0.01). Histologic examination confirmed that all scars were mature. Blinded, randomized, placebo-controlled human clinical trials are presently under way at the Mayo Clinic.     

A simplified model of scar contraction

The healing of wounds is a complex process and the contraction of the resulting scar can have a negative impact on the neighbouring skin. A finite element model of skin simulating the contraction of a scar and deformation of the surrounding skin is presented. The skin is represented by an orthotropic–viscoelastic constitutive law, which is validated against experimental data in the literature. A simplified experimental model of a contracting scar in real skin is also developed. The pattern and size of the wrinkles formed around the contracting scar in the finite element model compare favourably with those formed in the experimental model. The orthotropic nature of skin plays a significant role in the behaviour of skin around scars—the wrinkles have a preferential orientation that corresponds to a direction perpendicular to the Langer's lines in the skin. The pre-stress in skin (a property that is ignored in many skin models) is shown to be an important factor in wrinkle formation around scars. The proposed model can be used to analyse the suturing and closure of wounds of various shapes.     

Tension lines of the auricular cartilage

Utilizing Langer's technique for skin tension lines, we punctured the auricular cartilage of 10 human cadavers and 2 mature rabbits and 24 immature rabbits with a conical awl to determine their tension lines. Deformation of the holes into straight lines indicated the direction of maximum tension. A regular pattern was observed in adult rabbits and humans: Tension was at right angles to the long axis at the auricular base and parallel at the apex. This pattern was not present at birth, but developed at 1 to 2 weeks of age in rabbits. It is felt that these tension lines are responsible for the clinical results of auricular reconstruction. In children less than 1 week of age, tension lines are disorganized so that nonsurgical correction will be successful as long as hypoplasia is not present. In older children, correction will be successful when the deformity is parallel to the tension lines.     

Considerations on the role of surface tension and epidermal growth factor in the mechanism of integumental pattern formation

The formation of the posterior parietal hair whorl during normal human development is proposed as a morphogenetic problem in which the effects of surface tension and the appearance of singularities figure prominently. Surface tension is considered in the sense of "Langer's lines" which define local contours of tension in the skin of the organism. According to this view, an analysis of the organism's skin tension field is fundamental to problems of integumental pattern formation. A computational analysis of the skin tension field is proposed, potentially using methods from finite element theory applied to molecular and cellular mechanisms within the skin which resist deformation. To this end, surface tension is provisionally defined as the differential adsorption (adhesion) of molecular and supramolecular binding elements within the skin. In practical applications, it is suggested that epidermal growth factor (EGF) and similar molecules have the physicochemical features and the biological effects required to experimentally probe surface tension phenomena at supramolecular levels. In this regard, the concept of topological discontinuities is introduced as a potential theoretical bridge across levels of organization. Specific examples of these discontinuities are given and discussed in terms of the development of singularities in control surfaces. It is hoped that these considerations will be useful in the mechanistic analysis of hair whorl formation during human embryo-genesis and in other problems of integumental pattern formation and nonequilibrium surface behavior.     

"Zigzag" wavy-line periareolar incision

There is almost no mention of improvement in the aesthetics of areolar incisions in the plastic and reconstructive surgery literature. The most visible area of the breast is the central mound; therefore, it behooves surgeons to make an areolar incision as inconspicuous as possible. Minimal incision breast operations and short-scar operations, such as mastopexy and vertical reduction mammaplasty, use a circumareolar incision. This circumareolar technique, which specifically avoids a purse-string support suture, is useful in all periareolar incisions. This method creates a scar that mimics the elusive, natural irregularity between the areola and periareolar skin. The goal is to have an irregular, random, wavy line that appears more natural. Between August of 1998 and August of 1999, 104 "zigzag" wavy-line procedures were performed. The complications seen in this series included delayed healing in four patients and hypertrophic scar in two patients. No scars were surgically revised. The results demonstrated a definite difference compared to a circular scar. The zigzag wavy-line technique complements the innovative methods that shorten scars while they create a more natural, lasting breast mound. For areolar incisions, good results are deceptively subtle, but unnatural results can be painfully obvious. The zigzag wavy-line incision subtly eludes the eye in diminishing the signs the patient has undergone an operation.     

Survey of antibiotic prophylaxis in gastrointestinal surgery in Scotland.

The current use of prophylactic antibiotics in gastrointestinal surgery in Scotland was established by postal questionnaire. Twenty-one per cent of surgeons used prophylactic antibiotics during cholecystectomy, 49% during appendicectomy, and 95% for elective colorectal surgery. Two-thirds of those surgeons who did not provide routine antibiotic cover considered that the incidence of wound sepsis in their surgical practice was too low to merit special measures. Most surgeons using prophylaxis chose an appropriate antibiotic. The parenteral route for administration of antibiotic was used by 93% of surgeons during cholecystectomy, 29% during appendicectomy, and 45% in elective colorectal surgery. Most did not prolong cover beyond 24 hours postoperatively. This survey shows that the concepts governing the use of antibiotic prophylaxis have been absorbed into current surgical practice. Most surgeons used appropriate antibiotic regimens; many prefer the parenteral route of administration; most do not prolong cover beyond 24 hours.     

The expanded transposition flap: shifting paradigms based on experience gained from two decades of pediatric tissue expansion

The authors present their experience with the design of expanded skin flaps gained over the past two decades in a large series of 995 expanded flap reconstructions performed in 626 operations in 430 patients. The indications for tissue expansion were giant congenital pigmented nevi (72.7 percent), scar contractures (11.2 percent), and a remainder for a variety of congenital and acquired deformities. Surgical strategies were reviewed retrospectively to determine the location in the body where the tissue expansion was performed, the number of procedures required to accomplish the reconstructive goal, and the design of the expanded flap that was used to reconstruct the involved area. Specific points that were noticed included contour deformities (such as webbing, dog-ears, or decreased limb circumference) following flap reconstruction, anatomic distortions (such as distortion of the eyebrow or the distance from the brow to hairline) following reconstruction, final position of the scars in relation to anatomic landmarks, borders of aesthetic units, and relaxed skin tension lines, and the potential for later scar contracture. Careful examination of reconstruction by region of involvement demonstrated significant advantages in the use of expanded transposition flaps over pure advancement. These advantages and the modifications in the design of expanded flaps for each body region are discussed in a series of representative cases. They emphasize the ability of transposition flaps to dissipate tension away from the flap apex and distribute it more proximally, thus redirecting the tension lines so there is less likelihood of anatomic distortion in the reconstructed area. Also, flaps designed in this manner allow improved contour by avoiding webbing, tenting across concavities, and bunching of skin laterally. The authors conclude that restricting the expanded flap design to advancement alone to minimize potential scarring severely limits the reconstructive capabilities of the added tissue and distracts from the surgeon's ability to accomplish the initial reconstructive goal. The cost of additional incisions is worthwhile to achieve better final contour of the reconstructed part, lesser risk of anatomic distortion, better position of the scars, and lowered risk of scar contracture.     

Short-scar face lift with extended SMAS platysma dissection and lifting and limited skin undermining

In the past 8 years, short-scar cervicofacial rhytidectomy has been used with great success and a high level of patient satisfaction. The operation involves limited incisions in the sideburn and preauricular areas, extending just around the fold of the ear lobule. Extensive undermining of the superficial musculoaponeurotic system (SMAS)/platysma is performed, and lifting of the face and neck is performed mainly at this level. Skin undermining is kept to a minimum, eliminating the need for extended incisions to reduce dog-ears. The preservation of fibrous bands between the skin and the SMAS/platysma unit is an important factor in making such an operation practical and is the reason why the skin incisions can be kept short. Dissection of large areas of skin and separation of the skin from the underlying SMAS necessitate larger incisions. The operation is safe, speedy, less traumatic, and well tolerated among patients at high risk, such as smokers. The risks of complications are also reduced with this operation.     

Comparison of analytical and inverse finite element approaches to estimate cell viscoelastic properties by micropipette aspiration

The viscoelastic properties of cells are important in predicting cell deformation under mechanical loading and may reflect cell phenotype or pathological transition. Previous studies have demonstrated that viscoelastic parameters estimated by finite element (FE) analyses of micropipette aspiration (MA) data differ from those estimated by the analytical half-space model. However, it is unclear whether these differences are statistically significant, as previous studies have been based on average cell properties or parametric analyses that do not reflect the inherent experimental and biological variability of real experimental data. To determine whether cell material parameters estimated by the half-space model are significantly different from those predicted by the FE method, we implemented an inverse FE method to estimate the viscoelastic parameters of a population of primary porcine aortic valve interstitial cells tested by MA. We found that inherent differences between the analytical and inverse FE estimation methods resulted in statistically significant differences in individual cell properties. However, in cases with small pipette to cell radius ratios and short loading periods, model-dependent differences were masked by experimental and cell-to-cell variability. Analytical models that account for finite cell-size and loading rate further relaxed the experimental conditions for which accurate cell material parameter estimates could be obtained. These data provide practical guidelines for analysis of MA data that account for the wide range of conditions encountered in typical experiments.     

Marsupial cells in long-term culture

Cell lines have been developed from several species of Australian marsupials and studied during long-term growth. Cell lines developed from macropodid skin or heart tissues all had reproducible finite life-spans. However, cell lines developed from dasyurids showed bariable behavior in culture: lines developed from Antechinus stuartii and Dasyurus viverrinus had finite life-spans, while lines developed from Sminthopsis crassicaudata had indefinite life-spans. S. crassicaudata lines usually became heteroplloid, but one was still diploid after 150 population doublings, while another contained a proportion (10%) of haploid cells. Other lines were developed from the peramelid, Perameles nasuta, and the phanlngerid, Trichosurus vulpecula.     

Sediment quality criteria in use around the world

 There have been numerous sediment quality guidelines (SQGs) developed during the past 20 years to assist regulators in dealing with contaminated sediments. Unfortunately, most of these have been developed in North America. Traditionally, sediment contamination was determined by assessing the bulk chemical concentrations of individual compounds and often comparing them with background or reference values. Since the 1980s, SQGs have attempted to incorporate biological effects in their derivation approach. These approaches can be categorized as empirical, frequency-based approaches to establish the relationship between sediment contamination and toxic response, and theoretically based approaches that attempt to account for differences in bioavailability through equilibrium partitioning (EqP) (i.e., using organic carbon or acid volatile sulfides). Some of these guidelines have been adopted by various regulatory agencies in several countries and are being used as cleanup goals in remediation activities and to identify priority polluted sites. The original SQGs, which compared bulk chemical concentrations to a reference or to background, provided little insight into the ecosystem impact of sediment contaminants. Therefore, SQGs for individual chemicals were developed that relied on field sediment chemistry paired with field or laboratory-based biological effects data. Although some SQGs have been found to be relatively good predictors of significant site contamination, they also have several limitations. False positive and false negative predictions are frequently in the 20% to 30% range for many chemicals and higher for others. The guidelines are chemical specific and do not establish causality where chemical mixtures occur. Equilibrium-based guidelines do not consider sediment ingestion as an exposure route. The guidelines do not consider spatial and temporal variability, and they may not apply in dynamic or larger-grained sediments. Finally, sediment chemistry and bioavailability are easily altered by sampling and subsequent manipulation processes, and therefore, measured SQGs may not reflect in situ conditions. All the assessment tools provide useful information, but some (such as SQGs, laboratory toxicity and bioaccumulation, and benthic indices) are prone to misinterpretation without the availability of specific in situ exposure and effects data. SQGs should be used only in a “screening” manner or in a “weight-of-evidence” approach. Aquatic ecosystems (including sediments) must be assessed in a “holistic” manner in which multiple components are assessed (e.g., habitat, hydrodynamics, resident biota, toxicity, and physicochemistry, including SQGs) by using integrated approaches. Received: December 26, 2000 / Accepted: December 28, 2001     

Designing a strategy to implement cost-effective blood transfusion management in elective hip and knee arthroplasties: A study protocol

ABSTRACT: BACKGROUND: Total hip and knee arthroplasties are two of the most commonly performed procedures in orthopedic surgery. Different blood-saving measures (BSMs) are used to reduce the often-needed allogenic blood transfusions in these procedures. A recent large randomized controlled trial showed it is not cost effective to use the BSMs of erythropoietin and perioperative autologous blood salvage in elective primary hip and knee arthroplasties. Despite dissemination of these study results, medical professionals keep using these BSMs. To actually change practice, an implementation strategy is needed that is based on a good understanding of target groups and settings and the psychological constructs that predict behavior of medical professionals. However, detailed insight into these issuses is lacking. Therefore, this study aims to explore which groups of professionals should be targeted at which settings, as well as relevant barriers and facilitators that should be taken into acount in the strategy to implement evidence-based, cost-effective blood transfusion management and to de-implement BSMs. METHODS: The study consists of three phases. First, a questionnaire survey among all Dutch orthopedic hospital departments and independent treatment centers (n?=?99) will be conducted to analyze current blood management practice. Second, semistructured interviews will be held among 10 orthopedic surgeons and 10 anesthesiologists to identify barriers and facilitators that are relevant for the uptake of cost-effective blood transfusion management. Interview questions will be based on the Theoretical Domains Interview framework. The interviews will be followed by a questionnaire survey among 800 medical professionals in orthopedics and anesthesiology (400 professionals per discipline) in which the identified barriers and facilitators will be ranked by frequency and importance. Finally, an implementation strategy will be developed based on the results from the previous phases, using principles of intervention mapping and an expert panel. DISCUSSION: The developed strategy for cost-effective blood transfusion management by de-implementing BSMs is likely to reduce costs for elective hip and knee arthroplasties. In addition, this study will lead to generalized knowledge regarding relevant factors for the de-implementation of non-cost-effective interventions and insight in the differences between implementation and de-implementation strategies.     

The screening of non-H-2 congenic lines forSk loci

Thirty-seven histocompatibility congenic lines of mice, including at least 27non- H-2 lines, developed by Bailey on the C57BL/6 background, were screened for loci determining Sk (skin-specific) histocompatibility antigens. Background strain hosts were inoculated with lymphoid cells from the congenic lines and subsequently challenged with skin test grafts from the same donors. Comparison of the survival times of these test grafts with those of first- and second-set skin grafts in the same donor-host combinations suggests that the lymphoid cells from 35 of the congenic lines apparently immunized or tolerized at least some of the hosts. Thus, the histocompatibility antigens involved were shared by lymphoid cells and skin, and by definition could not be Sk antigens. The tests were indecisive with two of the non-H-2 lines, but if Sk antigens were involved, their contribution to the immunogenicity of conventional skin allografts probably was negligible. Hence ifSk congenic lines are desired, they probably will have to be developed on their own by procedures specifically designed to select for Sk antigens of significant immunogenicity.     

Proteomic studies support the use of multi-product immunoassays to monitor host cell protein impurities

In the biopharmaceutical industry, recombinant protein drugs are commonly produced in Chinese hamster ovary (CHO) cells. During the development process, removal of CHO cell-derived proteins from the biopharmaceutical product is monitored using multi-product immunoassays. Such immunoassays are developed by raising antibodies to a single CHO cell protein preparation. However, these assays are utilized to monitor CHO cell protein impurities during the recovery of products from different CHO cell lines. To address whether underlying differences between CHO cell lines result in sufficient protein expression changes to exclude the suitability of multi-product immunoassays, a comparative proteomics study of three independently generated CHO cell lines was performed. Statistical analysis of over 1000 proteins resolved by 2-D PAGE demonstrated that the protein expression profiles of three different CHO cell lines exhibit very few differences in protein expression. Only 11 qualitative changes in protein expression and 26 quantitative changes greater than two-fold were observed. Identification of protein spots by mass spectrometry revealed that many of the observed changes were due to post-translational modifications rather than expression of novel proteins in each cell line. These results suggest that multi-product immunoassays are suitable for monitoring host cell proteins in biopharmaceuticals produced in different CHO cell lines.     

Managed care's attempts to capture aesthetic surgery

Managed care organizations recently have attempted to add aesthetic surgery to their line of available services. To better understand the challenges posed by these actions, all members of the American Society for Aesthetic Plastic Surgery were surveyed about managed care overtures to aesthetic plastic surgeons, their responses, and the likely responses of their patients. The goal was to examine both the supplier and consumer ends of the aesthetic surgery market to determine the likely effects of managed care's attempts to capture aesthetic surgery. A total of 632 plastic surgeons returned the surveys (response rate, 54.5 percent). Twenty-two percent reported being approached by managed care organizations about joining a panel of aesthetic surgeons. Approximately one-quarter of the plastic surgeons said they would participate in aesthetic surgery panels developed by managed care organizations. Characteristics significantly associated with willingness to participate were solo practice structure, a low percentage of practice revenues from aesthetic surgery, and a very competitive practice environment. Plastic surgeons believed that their colleagues would be even more willing to acquiesce to managed care aesthetic surgery; more than one-third said that 25 to 50 percent of their colleagues would join, and nearly one-third thought that more than half would participate. Plastic surgeons believed that many of their patients would also participate in managed care aesthetic surgery. Twenty-four percent thought that more than half of their patients would choose an aesthetic surgeon through their managed care organization if that organization developed a network for aesthetic surgery. This figure increased to almost 40 percent if the organization would deny coverage for complications resulting from nonpanel surgeons, and to 41 percent if the organization would offer price discounts. This survey shows that most plastic surgeons are against managed care aesthetic surgery. But it also shows that some plastic surgeons will participate, and that most plastic surgeons think many of their colleagues and patients will do likewise. This means that managed care organizations have the potential to make inroads in aesthetic surgery on both the supplier and consumer ends of the market. To prevent managed care from capturing aesthetic surgery, plastic surgeons must anticipate the likely business strategy of managed care. To this end, they must understand the steps involved in the creation of a new service business and offer organized countermeasures against each of them.     

A practical guide to molecular dating

Molecular dating has now become a common tool for many biologists and considerable methodological improvements have been made over the last few years. However, the practice of estimating divergence times using molecular data is highly variable among researchers and it is not straightforward for a newcomer to the field to know how to start. Here I provide a brief overview of the current state-of-the-art of molecular dating practice. I review some of the important choices that must be made when conducting a divergence time analysis, including how to select and use calibrations and which relaxed clock model and program to use, with a focus on some practical aspects. I then provide some guidelines for the interpretation of results and briefly review some alternatives to molecular dating for obtaining divergence times. Last, I present some promising developments for the future of the field, related to the improvement of the calibration process.     

Sensibility of the abdomen after abdominoplasty

Abdominal skin hypesthesia may occur after abdominoplasty. The purpose of this study was to find out (1) which sensibility modalities are decreased and (2) which areas of the abdominal wall are affected, so that patients can be warned preoperatively about this condition. Forty patients were divided in two groups of 20 patients each. In the control group, patients had no previous abdominal incisions. The sensibility evaluation of patients from the experimental group was made from 12 to 60 months after abdominoplasty, with an average of 31.5 months. These patients were divided into two groups of 10 patients each, a short-term follow-up group (12 to 30 months postoperatively) and a long-term follow-up group (31 to 60 months postoperatively). The abdominal skin was divided into 12 areas; nine were above the abdominoplasty incision and three were below it. Sensibility to superficial touch, superficial pain, and hot and cold modalities was recorded as positive in all areas by a variable number of patients of the experimental group. However, in area 8 (hypogastric area), a statistically significant number of patients had decreased sensibility in all sensibility modalities (Fisher's test and t test). Patients in the experimental group also showed decreased sensibility to hot and cold temperature in area 11 (pubic area). Sensibility to pressure decreased significantly in all areas of the abdomen when compared with the control group (t test). When patients of the short-term follow-up group were compared with those of the long-term follow-up group, there was no statistically significant difference for all modalities of sensibility in the areas studied, except for area 5. In this area it was found that long-term follow-up patients recovered sensibility to cold and hot temperatures. These findings help plastic surgeons to orient their patients about possible risk of exposure to injuries in the areas with decreased sensibility after abdominoplasty. Most importantly, as these patients have decreased sensibility to pressure and hot temperature in a more extensive area of the abdomen, they are exposed to a higher risk of burn injury.     

Glycerol treatment as recovery procedure for cryopreserved human skin allografts positive for bacteria and fungi

Human donor skin allografts are suitable and much used temporary biological (burn) wound dressings. They prepare the excised wound bed for final autografting and form an excellent substrate for revascularisation and for the formation of granulation tissue. Two preservation methods, glycerol preservation and cryopreservation, are commonly used by tissue banks for the long-term storage of skin grafts. The burn surgeons of the Queen Astrid Military Hospital preferentially use partly viable cryopreserved skin allografts. After mandatory 14-day bacterial and mycological culture, however, approximately 15% of the cryopreserved skin allografts cannot be released from quarantine because of positive culture. To maximize the use of our scarce and precious donor skin, we developed a glycerolisation-based recovery method for these culture positive cryopreserved allografts. The inactivation and preservation method, described in this paper, allowed for an efficient inactivation of the colonising bacteria and fungi, with the exception of spore-formers, and did not influence the structural and functional aspects of the skin allografts.     

Unfixed cryosections of striated muscle to study dynamic molecular events.

The structures of the actin and myosin filaments of striated muscle have been studied extensively in the past by sectioning of fixed specimens. However, chemical fixation alters molecular details and prevents biochemically induced structural changes. To overcome these problems, we investigate here the potential of cryosectioning unfixed muscle. In cryosections of relaxed, unfixed specimens, individual myosin filaments displayed the characteristic helical organization of detached cross-bridges, but the filament lattice had disintegrated. To preserve both the filament lattice and the molecular structure of the filaments, we decided to section unfixed rigor muscle, stabilized by actomyosin cross-bridges. The best sections showed periodic, angled cross-bridges attached to actin and their Fourier transforms displayed layer lines similar to those in x-ray diffraction patterns of rigor muscle. To preserve relaxed filaments in their original lattice, unfixed sections of rigor muscle were picked up on a grid and relaxed before negative staining. The myosin and actin filaments showed the characteristic helical arrangements of detached cross-bridges and actin subunits, and Fourier transforms were similar to x-ray patterns of relaxed muscle. We conclude that the rigor structure of muscle and the ability of the filament lattice to undergo the rigor-relaxed transformation can be preserved in unfixed cryosections. In the future, it should be possible to carry out dynamic studies of active sacromeres by cryo-electron microscopy.