Flap Tension Research Articles

Surgical Site Assessment for Soft Tissue Management in Ridge Augmentation Procedures.

The success of bone augmentation is usually dependent on primary wound closure. This review provides a literature-based system to assess the predictability of achieving primary wound closure. Seven pertinent factors that determine the risk for wound exposure were identified: (1) the width of keratinized mucosa, (2) flap thickness, (3) flap tension, (4) vestibular depth, (5) type and (6) size of the bony defect, and (7) materials used. Clinical cases are used to demonstrate evaluation of these factors. This evaluation system may aid clinicians in differentiating cases with various risks of wound exposure and making decisions on flap modifications and the most appropriate surgical designs.

Reconstruction of skin defects around the Achilles tendon with rectangle advancement flap in children

Objective To explore the clinical efficacy of rectangle advancement flaps used in the re-construction of skin defects around the Achilles tendon in children. Methods From May 2014 to June 2015, 7 children with skin defects around the Achilles tendon were admitted to our trauma center. The areas of skin defect ranged from 3.4 cm × 2.7 cm to 5.5 cm × 4.0 cm. The integrity of Achilles tendon was preserved in 6 cases but the tendon insertion was partly disrupted in one case. The skin defects were reconstructed with self-designed rectangle advancement flaps after debridement. In the one case with the Achilles tendon partly disrupted, the contaminated tendon ends were excised before wound closure. The injured ankles were immobilized in plantar flexion with one 1.5 mm K-wire and plaster splint to decrease the postoperative tension of the flap. Results All the flaps survived completely by primary intention but local infection occurred in 2 wounds which was cured by second intention of dressing change. The follow-up periods ranged from 8 to 12 months (average, 11.5 months). The scar around the flap was remarkable in 2 cases, but the flaps in the other cases ap-peared normal in terms of color and texture. The ankle function was satisfactorily normal in all the cases. Conclusion Our self-designed rectangle advancement flaps provide a simple, safe and reliable way to repair skin defects around the Achilles tendon in children. Key words: Foot; Wounds and injuries; Surgical flaps; Child

Effects of multimodal analgesia on postoperative rehabilitation in patients with lower limbs free flap transplantation

Objective To evaluate the effects of multimodal analgesia on postoperative rehabilitation in patients with lower limbs free flap transplantation. Methods A total of 100 patients scheduled for lower limbs free flap transplantation of department of traumatology and orthopedics were recruited from December 2013 to March 2015 in Nanfang Hospital of Southern Medical University. They were randomly divided into experimental group (50 cases, multimodal analgesia including patient-controlled analgesia, oral or vein painkillers on schedule and ration, on demand) and control group (50 cases, analgesia on demand, giving routine analgesia medicine according to the actual demands of patients). The effects of analgesia and sedation, sleep quality, satisfaction degree of patients towards discharge, the situation of angiospasm, the blood flow of skin flaps blood-vessels were compared between two groups. Results Repeat measurement of variance analysis results showed that there were significant differences among scores of the visual analogue scale (VAS) on postoperative patients with multimodal analgesia in different time points (8, 16, 24, 32, 40, 48h after operation) (Ftime=9.89, P 0.05). Statistical significance was found in Ramesay scores between experimental group and control group was (Fbetween group=6.84, P<0.05). Time effect and intervention interacted with each other (Finteraction=5.41, P<0.05). The score of sleep quality (3.7±1.1) in experimental group were lower than that in control group (5.2±1.9). The blood flow velocity of skin flaps blood-vessels in experimental group [(7.21±1.84) mm/s] was higher than that in control group [(6.21±1.43) mm/s] (t=2.254, P<0.05). The tension of skin flap in experimental group [(7.63±1.23) N] was lower than that in control group [(8.24±2.01) N]. Differences were statistically significant (t=2.771, 2.254, 2.006; P<0.05). Conclusions The multimodal analgesia can improve the effects of analgesia and sedation, sleep quality and microcirculation of local skin slaps in patients with lower limbs free flap transplantation. Key words: Pain measurement; Skin flap transplantation; Multimodal analgesia; Postoperative care

COMBINED THREE OPERATIONS FOR ONE STAGE DEFECTS REPAIR AFTER RESECTION OF LARGE XANTHELASMA PALPEBRARUM WITH EPICANTHUS

To investigate the effectiveness of combined three operations (rotated total upper eyelid skin flap, construction of double eyelid, and "Z" flap epicanthal plasty) for one stage defect repair after resection of xanthelasma palpebrarum with epicanthus. Between December 2013 and December 2015, 12 female patients with large xanthelasma palpebrarum and epicanthus underwent rotated total upper eyelid skin flap, construction of double eyelid, and "Z" flap epicanthal plasty for one stage defect repair. The age ranged from 36 to 59 years (mean, 43 years). The course of disease was 3 to 16 years, with an average of 11 years. The initial resection was performed in 6 cases, second resection of residual xanthelasma palpebrarum in 4 cases, and 2 cases had recurrence after resection. The maximum diameter of xanthelasma palpebrarum was 0.5-1.3 cm (mean, 1.0 cm). According to CHE Junmin et al criterion, epicanthus was rated as mild in 7 cases, moderate in 3 cases, and severe in 2 cases. The blood lipid level was in normal range. Primary healing of incision was obtained, and the flaps survived in all patients; no complication occurred. Scar hyperplasia was found in 4 cases at 1 month after operation, and the comprehensive treatment of scar was performed. All patients were followed up for 3 months to 2 years, with an average of 1.5 years. Double eyelid effects were good, and no xanthelasma palpebrarum recurred. A combination of rotated total upper eyelid skin flap, construction of double eyelid, and "Z" flap epicanthal plasty is an effective operative procedure to repair defect after resection of xanthelasma palpebrarum with epicanthus; and better curve of double eyelid, better shape of endocanthion, and less tension of flap can be got.

Simple Metric Measurement To Choose A keystone Flap Design On Extremities: A Cadaveric Study

Background: Closing defect on extremities can be challenging because of limited donor area in order to obtain similar quality, color, texture, and adequate size with the defect. The keystone flap has gained popularity as a tool for local reconstruction because of its simple design, short operative time, good aesthetic outcome, and cost-effective wound closure. The aim of this study is to introduce a method in choosing a keystone flap design based on simple metric measurement resulting in lower tension..&#x0D; Methods: Four circular defects were created on 4 different regions of a fresh cadaver’s upper limbs. Diameters were 5 cm for upper arms and 3 cm for lower arms. Two options of keystone flaps designs were introduced. The keystone could be advanced in longitudinal manner or in transversal manner according to limb’s axis. We then calculated the percentage of the skin required to stretch, in order to close the defects. The less percentage of skin required to stretch between the two manners indicated the lower tension of the keystone flap.&#x0D; Results: Measurements in all of 4 regions of upper limbs showed that the percentage of skin stretch in closing the defects was lower in longitudinal advancement keystone flap compared to transversal advancement (19.88% versus 27.8% for upper arms and 15.71% versus 21.67% for lower arms)&#x0D; Conclusion: Simple metric measurements in choosing a keystone flap can be applied to defects on extremities. With less tension when raising the keystone flap, acceptable scar is expected and the occurrence of contracture and flap necrosis can be reduced.

Application of finite element modeling to optimize flap design with tissue expansion.

Tissue expansion is a widely used technique to create skin flaps for the correction of sizable defects in reconstructive plastic surgery. Major complications following the inset of expanded flaps include breakdown and uncontrolled scarring secondary to excessive tissue tension. Although it is recognized that mechanical forces may significantly impact the success of defect repair with tissue expansion, a mechanical analysis of tissue stresses has not previously been attempted. Such analyses have the potential to optimize flap design preoperatively. The authors establish computer-aided design as a tool with which to explore stress profiles for two commonly used flap designs, the direct advancement flap and the double back-cut flap. The authors advanced both flaps parallel and perpendicular to the relaxed skin tension lines to quantify the impact of tissue anisotropy on stress distribution profiles. Stress profiles were highly sensitive to flap design and orientation of relaxed skin tension lines, with stress minimized when flaps were advanced perpendicular to relaxed skin tension lines. Maximum stresses in advancement flaps occurred at the distal end of the flap, followed by the base. The double back-cut design increased stress at the lateral edges of the flap. The authors conclude that finite element modeling may be used to effectively predict areas of increased flap tension. Performed preoperatively, such modeling can allow for the optimization of flap design and a potential reduction in complications such as flap dehiscence and hypertrophic scarring.

Axillary Fistula and Scar Contracture due to Uncontrolled Chronic Infection after Trans-Axillary Augmentation Mammaplasty.

Axillary Fistula and Scar Contracture due to Uncontrolled Chronic Infection after Trans-Axillary Augmentation Mammaplasty.

The role played by a suspended external-internal suture in reducing marginal flap tension after bone reconstruction: a clinical prospective cohort study in the maxilla.

To define the role played by a suspended external-internal (SEI) suture in reducing marginal flap tension after bone augmentation in the maxilla and in enhancing primary wound healing. Twenty partially edentulous patients requiring bone augmentation (either guided bone regeneration or autogenous bone block placement) before or simultaneous with implant insertion in the maxilla were enrolled in this clinical prospective cohort study. Flap tension was measured by a dynamometer, which was accurate to within 1 g. The force recorded was that needed to enable the vestibular extensible flap to reach the edge of the palatal nonextensible flap. Flap tension was recorded after the periosteum-releasing incision was made (before application of any suture; T1), and after the SEI suture was applied (T2). Final marginal flap adaptation was accomplished via horizontal mattress sutures and simple stitches. Wound healing was monitored at 1, 2, 4, and 16 weeks and classified as "obtained primary closure" or "compromised" as a result of dehiscence or marginal flap necrosis. The mean flap tension measured at T1 was 32.9 ± 7.7 g. After the SEI suture was applied, the mean marginal flap tension decreased to 4.1 ± 1.5 g. The marginal flap tension was reduced by 87.6% compared to the initial strain. All patients healed uneventfully, and no complications such as dehiscences or marginal flap necrosis were recorded. The application of the SEI suture reduced the tension on the margins of the flaps and played a decisive role in obtaining primary wound healing. In case of passive wound closure (strain < 5 g), the type of augmentation procedure (guided bone regeneration or autogenous block) was revealed to have no impact on the quality of wound healing.

Shortening Foreheadplasty; Minimization of the Tension of Scalp Flap

Shortening Foreheadplasty; Minimization of the Tension of Scalp Flap

Endaural access to remove the projectile from a firearm

Surgical approaches to temporomandibular region have been the subject of numerous controversies in the literature. Pre-auricular approaches have been used with the observance of high success rate, and during surgery history, various modifications of this approach were conducted in order to reduce irreversible sequelae. Thus, given the relevance of the study, this article proposes to alert the professionals that carry out these surgical approaches in relation to the anatomical structures involved and to describe and emphasise the benefits of endaural approach. A Caucasian male patient, victim of a firearm injury, sustained a wound on the right pre-auricular region, and at the time of assessment, he complained of pain, mouth opening difficulty and dysphagia. On physical examination, there was oedema and ecchymosis in the right periorbital region. In the radiological examination, a foreign body compatible with a firearm projectile was observed in the right pre-auricular region, being in accordance with the information collected. The endaural incision and divulsion by plans was then made until the projectile. For proper exposure of the region, several studies were designed to evaluate the patterns of branching and anastomosis of the facial nerve. As for the best cosmetic result with the different pre-auricular approaches, the endaural approach was described as an approach that offers great cosmetic results because the incision design guides the surgeon in the wound closure and causes a decrease in the tension of flap, unlike that observed by some authors.

A retrospective study of 1270 cases with free flap transplantation

Objective Evaluate data of 1270 cases with free flap transplant,to find the problems in the process of operation,and then to analyse its causes and how to prevent and solve it,as well as providing reference for clinical colleagues. Methods To study 1270 cases of free flaps,musculocutaneous flap and perforator flap who was treated in our hospital from October 2000 to October 2010 retrospectively. A total of 722 cases of the group were followed-up 6 months to 5 years. To detective and search the problems and imperfection from designing,harvesting,tranfer,to the management and function of donor site after free flap transplantion.And also to analysis the couse of problems and operation failure,discuss the conclude of and to provide advisable measure. Results Total 1270 free flaps were transplanted successfully except 64 can-celled or failured for some reason, the success rate was 95.0％, the postopertive necrosis rate was 3.8％.Seventy-six cases were encountered vascular complications venous crisis in 42,arterial crisis in 38.Fifty-five cases were saved successfully without surgery,and 15 cases survived completely by vessel explorative operation. Five cases were partial necrosis and 7 cases necrosis. The rate of postoperative infection of emergency cases and chronic one were 4.7％ (682 cases)and 8.8％(588 cases) which show the infective incidence of latter was higher than former. In addition, there were many other problems were found such as distal flaps necrosis,contracture,deformation,impairment function of doner site,etc. Conclusion Preventing and management timely to vessle crisis is the key to flap suvive. The principle of dissecting flap should be followed strictly,and control the indications of modified processing during flap harvest,keep the proper flap tension were technical requirements in flap transplantion. Right way of donor site closed and management of insufficient timely were equally important to prevent and solve to complications and dysfunction. Key words: Surgical flaps; Soft tissue injury; Transplantation; Microsurgry

Effects of hyperbaric oxygen therapy on rapid tissue expansion in rabbits

Tissue expansion has been widely used to provide additional soft tissue for clinical reconstruction. Rapid expansion requires a much shorter clinical period than conventional expansion; however, less natural skin growth occurs resulting in a larger stretch-back ratio and insufficient extra soft tissue for clinical use. In this study, hyperbaric oxygen therapy (HBOT) was used in the inflation phase of rapid expansion to increase natural skin growth. Twelve rabbits were divided into two groups. Each group received rapid expander inflation every day. One group received HBOT and the other did not. Blood flow in the expanded skin of each rabbit was assayed in the 10-day inflation phase. After the inflation phase, a rectangular expanded flap of each rabbit was harvested. The instant stretch-back ratio, tension, weight and histological characteristics of the flaps were evaluated. (1) After the second inflation day, the mean blood flow of the HBOT group became significantly higher than that of the control with each day (P < 0.05). At the last day, the blood flow of the HBOT group increased to 131 ± 17 pu, while the control group decreased to 35 ± 5 pu. (2) The mean instant stretch-back ratio of the HBOT group under no-tension conditions was 29 ± 4%, which was significantly less than that of the control group, 46 ± 3% (P < 0.01). (3) The mean flap tension of the HBOT group was 15.3000 ± 1.47648 g and 12.9833 ± 0.73598 g in the transverse and longitudinal axis, respectively, both significantly smaller than that of the control group (33.9167 ± 4.78390 g and 26.5000 ± 2.45031 g, respectively) (P < 0.01). (4) Mean per unit flap weight of the HBOT group was 0.221 ± 0.005 g cm(-2), significantly heavier (P < 0.01) than that of the control group (0.143 ± 0.010 g cm(-2)). (5) Histologically, the epidermal layer and thickness of the expanded skin of the HBOT group were much thicker than those of the control group, and more vessels were visible in the subcutaneous tissue. The use of HBOT in the inflation phase of rapid expansion can effectively promote blood flow in the expanded skin, increase its natural skin growth and reduce the instant stretch-back ratio and tension of expanded skin.

Unilateral Cervical Burn Scar Deformity Elimination With Contralateral Cervicothoracic Flap—A New Approach

Unilateral postburn cervical deformity is a severe cosmetic and functional defect and a challenging reconstructive problem. Many flaps have been suggested; however, after surgery, operational scars, located along the anterior neck's middle line, and the flap's skin differ from cervical healthy skin. A small flap resembles a patch. A more effective and safer technique is neck resurfacing with cervicothoracic adipocutaneous flap which had been used by the author in 32 burned patients. The flap's peculiarities are as follows: axis blood circulation via superficial cervical artery perforator; exclusion of platysma (flap is thin and elastic); and undamaged donor site. The mobilized healthy neck's skin with thin fat layer and adipocutaneous layer of the chest wall are elevated as a whole large flap. After scar excision, the cervicothoracic flap is advanced on the wound with tension. As a result of flap tension, the skin of neck's back, thoracic wall, and axilla are displaced to the anterior neck surface covering the donor wound. On an average, 6 cm of the deformed neck anterior surface was restored. No flap loss but only local superficial scar necrosis along the flap's border occurred. The cervical contracture and scar deformity (25 patients) were eliminated in all cases by a single procedure. For complete neck skin restoration, seven patients underwent staged reconstruction using the same technique. Excellent functional and good cosmetic follow-up results were achieved. The proposed technique is easy to plan and perform and yields good results; therefore, the author believes that the contralateral cervicothoracic flap's use is an exclusive option for unilateral cervical contracture and deformity elimination in adults and pediatric patients.

Analysis of Flap Tension in Surgical Rejuvenation of the Midface

To determine the flap tension present for 2 different surgical approaches for midface lifts and whether a gingivobuccal incision for release of the midface periosteum will diminish the resultant load on the midface flap. Cadaver study. Anatomy laboratory at the University of Florida. Twelve fresh-frozen cadaver heads are subjected to a transblepharoplasty (TB) approach on one side of the cadaver head while a transtemporal (TT) approach is performed on the contralateral side. The tension (grams) generated by moving the midface flap a distance of 1.03 cm is recorded by a digital load cell. A gingivobuccal incision is made on each side to allow transoral periosteal release (TOPR) of the midface flap, and the experiment is repeated. Three trials are performed for each operation, and the average load is calculated. A paired t test is applied. The tension resulting from the TT approach (172 g) was not found to be significantly different from that of the TB approach (179 g; P = .75). Significant differences in the resultant tension were not appreciated when comparing standard techniques to TT with TOPR (141.5 g; P = .27) or for TB with TOPR (164.1 g; P = .45). An experimental method is described for determining flap tension in facial rejuvenation surgery. No significant difference is found between flap tensions generated in the TB and TT approaches to the midface.

Trapeze-Flap Plasty: An Effective Technique for Postburn Edge Elbow Contracture Elimination

Background Scar flexion elbow contracture is a common complication of burns that restricts upper limb function and requires surgical elimination. In spite of the many surgical techniques that have been suggested, the contracture reconstruction still presents a challenge for surgeons. Methods One hundred and twenty-six patients with 174 edge elbow contractures were operated on. Edge elbow contracture, comprising 70% of all elbow contractures, is characterized by the presence of the fold located on the medial or/and lateral edge of cubital fossa. A crescent-shaped fold consists of a lateral sheet, comprising scars; the medial sheet and cubital fossa consists of healthy skin. The fold's crest is the edge of the scar sheet. The contracture is caused by the scar sheet's surface deficit in length; the scar's surface deficit is present all the way from the fold's crest to the joint rotation axis, and possesses a trapezoid shape. The best tissue for scar sheet deficit compensation and contracture elimination the comprises healthy skin of the cubital fossa and medial fold sheet. After fold sheet division, scar sheet dissection and joint extension, the trapeze-shaped wound is formed as a rule. The adipose-cutaneous trapezoid flap, which includes all the cubital fossa and medial fold sheet surface, is elevated. The flap advances on the wound with tension. As a result of flap tension, the adjacent skin of the contralateral side and the back surfaces of the elbow are displaced towards the cubital fossa, participating in donor wound coverage and contracture elimination. Results Mild edge elbow contractures were eliminated with a single trapezoid flap. In the case of moderate and severe contractures, additional trapezoid adipose-scar flaps were elevated from the scar sheet in order to cover the donor wound on the sides of the main flap. The adipose-cutaneous and adipose-scar trapezoid flaps are large, have no acute angles, do not undergo rotation and have steady blood circulation. Contractures were eliminated completely in 166 cases. Local flap end necrosis of the adipose-scar flap occurred in eight cases. The extended healthy flap's skin continued to grow. Full range of flexion and extension was achieved in all cases, except for eight cases with articular changes; there was no contracture recurrence and no re-operations were needed. The cubital fossa as the donor site preserved a normal shape as a result of growth of the stretched skin. Conclusion The single-staged trapeze-flap technique using cubital fossa flap is easy to plan and perform; edge elbow contractures of different severity were eliminated in full and definitively without skin grafting, pedicled and free flaps.

Role of flap tension in primary wound closure of mucoperiosteal flaps: a prospective cohort study

To evaluate the role of suture tension in primary wound closure of mucoperiosteal flaps. Sixty patients, scheduled for a single implant installation, were recruited. Before suturing, the wound closing forces were measured with an electronic tension device. One week after the surgery, the wounds were inspected with regard to complete closure. The applied tension varied between 0.01 and 0.4 N. In 72% a tension of 0.01-0.1 N was applied, resulting in few dehiscences (10%). Higher closing forces (>0.1 N) increased the percentage of wound dehiscences significantly (> or = 40%). It appears necessary to control flap tension at the time of wound closure to achieve a primary closure.

The surgical separation of pygopagus conjoined twins

To explore the program of preoperative evaluation, preoperative preparation and separation operation of pygopagus conjoined twins. Clinical data of one case of pygopagus (male, gestational age 37 weeks, uterine-incision delivery, 3.5 months old; twins of triplets; total body weight 8.0 kg. The twins have self-governed extremities, anus, penis. Four limbs can move independently). Separated successfully were analyzed. The auxiliary examination of X-rays, MRI, ultrasound, CT and 3D reconstruction, sensory evoked potential showed that there were process hypoplasia and lamina bifid of lumbosacral vertebrae below L3. Dural sac connected below L3 and conus medullaris located at L3. There were no conjunction of spinal cord and cauda equine. The decision of direct suture of dural sac was made by preoperative evaluation through measurement of circumference and area of conjoined dural sac. The separation surgery program was decided through team debate and sham operation. Separation operation was performed under the general anaesthesia. Crossing V-shaped skin flap was used to cover the wound surface. The dura of conjoined twins were sutured directly. The tension of skin flap was normal postoperative with continuing negative pressure drainage under the flap and pressure sterilized dressing. Successful separation of pygopagus conjoined twins was achieved. Lower extremities movements of separated twins were normal 6 h after operation. The drainage was removed 1 day postoperative, blood supplies of skin flap were normal. There were no complications of infection, cerebrospinal fluid leakage and neurological deficit. The healing of the skin flap was good. With 6 months follow-up, the growth and neurological function were normal. Consummate preoperative preparation, accurate preoperative investigations, meticulous operative management, careful postoperative administration and good team cooperation are the keys to successful separation of pygopagus conjoined twins.

Analysis of Flap Tension in Midface Surgery

Problem Despite a large volume of literature addressing rejuvenation of the midface, there is an absence of objective data addressing the various approaches to midface lifting. This study compares flap tensions generated by midface lifts though transblepharoplasty (TB) and transtemporal (TT) surgical approaches, with and without the additional intervention of a transoral periosteal release. Methods 12 fresh cadaver heads underwent standard TB and TT approaches for midface lifting with Endotine (Coapt Systems, Inc, Palo Alto, CA) fixation devices. A machined apparatus, designed for this experiment, pulled the midface flap one centimeter along a posterior-superior vector while a precision digital load cell recorded the generated tension (grams). A transoral periosteal release was performed and flap tensions were measured again after this intervention. Green-house-Geisser test allowed analysis of the three-way interaction between surgical approach, periosteal release, and the number of times the test was repeated. Results Flap tension decreased significantly during testing with each sequential repeated pull on the midface (p&lt;0.0001). Average flap tension for TB approach did not differ significantly from that of TT approach, whether or not a periosteal release was performed. However, while no particular approach was found to have a significant reduction in flap tension, a transoral periosteal release produced a significant reduction in flap tension (12%) when compared to trials without periosteal release (p=0.0191). Conclusion A significant reduction in flap tension as a result of transoral periosteal release is demonstrated in both transtemporal and transblepharoplasty approaches for midface lifting. This objective reduction in flap tension may allow the surgeon greater mobility of the midface tissues and perhaps less tension opposing flap fixation. Significance The objective reduction in flap tension by employing a transoral subperiosteal release may allow the surgeon greater mobility of the midface tissues and perhaps less tension opposing flap fixation. Support Coapt Systems, Inc, (Palo Alto, CA) provided the endotine devices utilized in the experiment.

Influence of suture tension to the tearing characteristics of the soft tissues: an in vitro experiment

To evaluate the influence of flap tension on the tearing characteristics of mucosal tissue samples in relation to various suture and needle characteristics. Lining and masticatory mucosal tissue samples obtained from pig jaws were prepared for in vitro testing. Tension tearing diagrams of 60 experiments were traced for 3-0, 5-0 and 7-0 sutures with applied forces up to 20 N. In the second part, the same experiments were repeated with 100 diagrams to test the influence of needle characteristics with 5-0 and 6-0 sutures using only gingival tissue samples. 3-0 sutures mainly lead to tissue breakage at an average of 13.4 N. In contrast, 7-0 sutures only resulted in breakage of the thread at a mean applied force of 3.7 N. With 5-0 sutures, both events occurred at random at a mean force of 14.6 N. Irrespective of the needle characteristics, the mean breaking force for gingival samples with 5-0 and 6-0 sutures was approximately 10 N. Tissue trauma may be reduced by choosing finer suture diameters, because thinner (6-0, 7-0) sutures lead to thread breakage rather than tissue breakage.

The influence of local and systemic preconditioning on oxygenation, metabolism and survival in critically ischaemic skin flaps in pigs

Stress proteins represent a group of highly conserved intracellular proteins that provide adaptation against cellular stress. The present study aims to elucidate the stress protein-mediated effects of local hyperthermia and systemic administration of monophosphoryl lipid A (MPL) on oxygenation, metabolism and survival in bilateral porcine random pattern buttock flaps. Preconditioning was achieved 24h prior to surgery by applying a heating blanket on the operative site (n = 5), by intravenous administration of MPL at a dosage of 35 microg/kg body weight (n = 5) or by combining the two (n = 5). The flaps were monitored with laser Doppler flowmetry, polarographic microprobes and microdialysis until 5h postoperatively. Semiquantitative immunohistochemistry was performed for heat shock protein 70 (HSP70), heat shock protein 32 (also termed haem oxygenase-1, HO-1), and inducible nitrc oxide synthase (iNOS). The administration of MPL increased the impaired microcirculatory blood flow in the proximal part of the flap and partial oxygen tension in the the distal part by approximately 100% each (both P<0.05), whereas both variables remained virtually unaffected by local heat preconditioning. Lactate/pyruvate (L/P) ratio and glycerol concentration (representing cell membrane disintegration) in the distal part of the flap gradually increased to values of approximately 500 mmol/l and approximately 350 micromol/l, respectively (both P<0.01), which was substantially attenuated by heat application (P<0.01 for L/P ratio and P<0.05 for glycerol) and combined preconditioning (P<0.01 for both variables), whereas the effect of MPL was less marked (not significant). Flap survival was increased from 56% (untreated animals) to 65% after MPL (not significant), 71% after heat application (P<0.05) and 78% after both methods of preconditioning (P<0.01). iNOS and HO-1 were upregulated after each method of preconditioning (P<0.05), whereas augmented HSP70 staining was only observed after heat application (P<0.05). We conclude that local hyperthermia is more effective in preventing flap necrosis than systemic MPL administration because of enhancing the cellular tolerance to hypoxic stress, which is possibly mediated by HSP70, whereas some benefit may be obtained with MPL due to iNOS and HO-1-mediated improvement in tissue oxygenation.