Effect of radiation on skin expansion and skin flap viability in pigs

The aim of the present study was to investigate the effect of radiation treatment both on skin tissue expansion with the chronic inflation of subcutaneous expanders and on skin flap viability in surgically delayed and expanded skin in the pig. One flank in each of six pigs (initially weighing 17 +/- 1.8 kg) was randomly assigned for radiation treatment, and the contralateral flank served as a nonirradiated control. Three mirror-image, 8 x 10 cm, rectangular templates were marked on each flank; these templates were randomly assigned to the construction of a delayed skin flap (group A), a skin flap raised on expanded skin (group B), or a skin flap raised on expanded skin with a capsulectomy before flap surgery (group C). Radiation treatment was performed using sequential radiation with three fractions per week (810 cGy/fraction) for 2 weeks, with a total dose of 4,860 cGy. Twelve weeks after radiation treatment, skin expanders (8 x 10 cm) were installed subcutaneously in the locations assigned for skin expansion. Skin expansion by the inflation of subcutaneous skin expanders with saline twice weekly was started 8 weeks later and lasted for 3 weeks. Two weeks after surgical delay and the last skin expansion, 8 x 20 cm skin flaps were raised on the locations assigned for delayed skin flaps, expanded skin flaps, and expanded skin flaps with a capsulectomy. Skin flap viability was assessed 24 hours later using a fluorescein dye-staining technique. Skin expansion by the inflation of subcutaneous expanders with saline was slower (p < 0.05) in the radiated skin (39 +/- 6 ml/filling) than in the nonirradiated control skin (51 +/- 6 ml/filling). Radiation reduced the overall area of expanded skin by 23 percent (p < 0.05) compared with the control. Radiation treatment also reduced skin viability by 36 percent (p < 0.05) in the delayed skin flaps, 27 percent (p = 0.10) in the expanded skin flaps, and 36 percent (p < 0.05) in the expanded skin flaps with a capsulectomy when compared with their contralateral, nonirradiated controls. There were no significant differences in skin viability among these three types of skin flaps within the radiated and nonirradiated groups. Taken together, these observations indicate that radiation treatment reduced the effectiveness of the surgical delay procedure, the amount of subcutaneous skin expansion (by an increase in skin area), and skin flap viability. However, a capsulectomy alone did not affect the viability of skin flaps raised on expanded skin.     

Biomechanical effect of rapid mucoperiosteal palatal tissue expansion with the use of osmotic expanders

The comparative study was performed to investigate the biomechanical properties (maximum tangential stiffness, maximum tangential modulus and tensile strength) of expanded mucoperiosteal palatal tissue after rapid expansion regimen correlated with histological findings. Rabbit palatal model was used to correlate the non-operated control group, sham-operated control (subperiosteal tissue dissection) groups and 24- and 48-hour tissue expansion groups. There was no observed damage of tissue collagen network in both tissue expansion groups analyzed immediately after expansion, and biomechanical profile was not significantly different from the profile of control groups. However, rapid tissue expansion activates remodeling of mucoperiosteal tissue structure that revealed significant changes in mechanical properties during the 4-week follow-up. The 24-hour expansion induced transient increase of resilience observed 2 weeks after surgery in comparison to the control groups. As a result of maturation of newly created collagen fibers and mucoperiosteum rebuilding, there were no significant differences between any of the analyzed tensile parameters 4 weeks after the 24-hour expansion. Increased and elongated inflammatory response and connective matrix synthesis observed during healing of 48-hour expanded tissue led to a significant decrease of tensile strength value in comparison to the control groups. Even though 4 weeks after surgery, the resilience of 48-hour expanded tissue was similar to the control groups, tissue healing was not completed and limited scar formation might considerably change the final biomechanical tissue profile. These findings provide new information about tensile properties to rapid mucoperiosteal palatal tissue expansion with the use of osmotic expanders for cleft palate repair by tissue augmentation.     

Increased survival and vascularity of random-pattern skin flaps elevated in controlled, expanded skin

Controlled clinical tissue expansion, a new technique of providing donor tissue, results in an increase in surface area of expanded skin. The aim of the present study was to determine the effect of controlled tissue expansion on the surviving lengths of random-pattern skin flaps elevated in expanded tissue. In five pigs the surviving lengths of flaps raised in skin expanded for 5 weeks using a 250-cc rectangular Radovan-type tissue expander were compared with the survival lengths of flaps elevated in tissue in which a similar prosthesis was not expanded, bipedicle flaps delayed for 5 weeks, and control acutely raised random-pattern flaps. The expanded flaps had a mean increase in surviving length of 117 percent over control flaps, which was statistically significant. The delay flaps had an increase in survival of 73 percent over control flaps, which was also statistically significant. There was no significant difference in survival between expanded flaps and delayed flaps. Morphologic studies using radiographic techniques on one pig demonstrated increased vascularity with tissue expansion. The results of this work demonstrate that in addition to providing increased surface area with controlled expansion, flaps raised in expanded skin have a significantly augmented surviving length. The mechanism for this increased vascularity with expansion is not known at this time, but it may be due to physical forces associated with expansion acting as a stimulus for angiogenesis.     

Continuous versus conventional tissue expansion: experimental verification of a new technique

Historically, tissue expansion is a prolonged process, typically requiring at least 6 weeks to complete. Recently, interest has increased in shortening this time period. In the current study, a continuous infusion device maintaining constant expander pressure less than capillary filling pressure was used in a canine model in seven dogs to minimize the time period needed to achieve significant expansion. There were no complications, except one device malfunction, corrected by changes in design. The process was shown to be a safe and effective means of producing amounts of expansion similar to traditional methods in approximately 72 hours, with expansion of 28 percent (n = 6) for continuous tissue expansion (CTE) versus 34 percent (n = 6) for a 2-week rapid expansion protocol. This expansion was derived from either stretch of preexisting tissue (46 percent for CTE, 35 percent for 2-week expansion) or recruitment of adjacent tissue. The clinical application of continuous tissue expansion could permit the advantages of tissue expansion to be obtained in many more situations than are currently available to traditional tissue expansion techniques.     

The tensiometric properties of expanded guinea pig skin

Our purpose in this study was to evaluate the tensile properties of expanded skin. In five guinea pigs, 29-cc ovoid tissue expanders were placed and sequentially expanded every 4 days until maximum volume was achieved. Five control and five expanded skins were harvested. Using an Instron tensile testing apparatus, skins were evaluated for stress-strain, maximum stiffness, and tensile strength, and the results were statistically compared. Centrally located expanded specimens demonstrated significantly weaker stress-strain values: 9.51 in.lb/in3 for expanded versus 30.11 in.lb/in3 for control (p less than 0.001). Maximum stiffness was similarly reduced: 4.56 lb/mm2 for expanded vs. 12.98 lb/mm2 for control (p less than 0.001). This is a 67.4 and 64.9 percent reduction, respectively, for the stress-strain and maximum stiffness. No statistically significant difference was seen in peripherally located expanded specimens relative to the controls: stress-strain expanded, 28.7 in.lb/in3 (p greater than 0.5); maximum stiffness expanded, 12.84 lb/mm2 (p greater than 0.5). Expanded skin demonstrated an average 35 percent reduction in tensile strength. We conclude that the tensile properties of expanded skin are significantly less than unexpanded skin and are a function of the degree of expansion.     

Dermal and epidermal response to soft-tissue expansion in the pig

To evaluate the dermal and epidermal response to soft-tissue expansion in the pig, round tissue expanders were placed dorsally under tattooed patterns and inflated over 6 weeks. Surface area, skin thickness, histologic changes, and collagen content were evaluated at 6-week intervals. Epidermal thickening and dermal thinning were observed. Dermal thinning persisted 36 weeks after expansion. Dermal collagen content was decreased, although collagen density remained unchanged. Total collagen content calculated within an expanded square grid increased. These data support a theoretical gain in the dermal layer as well as epidermal layer in response to tissue expansion.     

Radiotherapy: effects on expanded skin

Although the combination of radiation and tissue expansion has been associated with a significant rate of complications, the specific pathophysiology has yet to be clearly elucidated. The objective of this study was to develop a model to identify and examine specific histologic changes associated with tissue expansion and irradiation. Rectangular 50-cc silicone tissue expanders were placed subcutaneously over the midline dorsum of 18 adult New Zealand white rabbits. Preoperative radiographic dosimetry demonstrated that the radiation portal was away from vital intraabdominal structures. The expanders were inflated with 10 cc of saline every other day for a total of 80 cc. Expanders were left in place for 2 to 3 weeks to allow fibrovascular capsule formation. The rabbits were then divided into three groups (six rabbits per group), each receiving one of three nonfractionated doses of radiation (20, 25, or 35 Gy). Half of the expanded skin was irradiated using a single dose, and the other half served as a nonirradiated control. Capsules and skin were harvested 6 weeks after the delivery of radiation, allowing the beginning of chronic radiation changes to occur. Using hematoxylin and eosin staining, histomorphometric analysis was performed. The data were analyzed using Student's test. Although irradiation did not affect dermal thickness, it did cause a statistically significant increase in epidermal thickness. At 20, 25, and 35 Gy the increase in epidermal thickness was 43, 90, and 130 percent, respectively. Although significant epidermal changes could be identified, capsular and dermal alterations were not evident. Further studies evaluating the long-term effects of alterations in capsular formation caused by radiation may be required.     

Effect of capsulectomy on the hemodynamics and viability of random-pattern skin flaps raised on expanded skin in the pig

Skin flaps constructed on expanded skin usually include the underlying capsular tissue. It has been hypothesized that capsulectomy may jeopardize the viability of the expanded skin flap. The experiments reported herein were designed to test this hypothesis. Specifically, we studied the hemodynamics and viability of random-pattern skin flaps (8 X 20 cm) raised on delayed bipedicle flaps (group A) and on expanded skin pockets with capsulectomy at the time of flap elevation (group B) or with intact underlying capsular tissue (group C). Each group was randomly assigned to each flank in 16 pigs. Skin pockets were expanded by inflation of subcutaneous silicone tissue expanders with sterile saline (299 +/- 7 ml; X +/- SEM) over a period of 3 weeks. At the end of this period, the bipedicle flaps were constructed. Eight days later, random-pattern skin flaps were raised on bipedicle flaps and skin pockets. The length and area of skin flap viability, judged by the fluorescein dye test performed 1 day postoperatively, were not significantly different (p greater than 0.05) among groups A, B, and C (n = 31 to 32). There also were no significant differences (p greater than 0.05) in total skin capillary blood flow measured 1 day postoperatively (A = 2.6 +/- 0.4, B = 2.4 +/- 0.4, and C = 2.7 +/- 0.6 ml/min per flap; n = 15 to 16) and in skin viability assessed 7 days postoperatively (A = 74 +/- 2, B = 75 +/- 2, and C = 76 +/- 2 percent; n = 16) among delayed skin flaps and skin flaps raised on expanded skin pockets with or without capsulectomy. The results of this flap viability study were confirmed in 5 minipigs in a separate experiment. We conclude that capsulectomy did not have a detrimental effect on the hemodynamics and viability of random-pattern skin flaps raised on expanded skin. Furthermore, we hypothesize that skin flaps raised on expanded skin are similar to delayed skin flaps in that the skin blood flow is optimally augmented; therefore, the capsular tissue does not add significant blood supply to the overlying skin.     

Bone graft survival in expanded skin

The effect of tissue expansion on iliac bone graft (onlay) survival was studied on the skulls of 35 New Zealand white rabbits. Wet bone weights at the time of grafting and at sacrifice in control animals (group I) were compared to three experimental groups. Histologic sections of the developing and resolving pseudosheath and skin envelope were performed. A self-inflating 5-mil-thick silicone expander was used for soft-tissue expansion over the rabbit snout. Bone grafts were subsequently placed in this site. Elliptical snout excision without expansion (group II) demonstrated no statistically significant difference in bone graft survival when compared to controls (group I) (p = 0.350). Full tissue expansion followed by immediate bone grafting (group III) within the pseudosheath cavity likewise demonstrated no statistically significant difference in bone graft survival when compared to controls (group I) (p = 0.500); however, when full tissue expansion was followed by delayed (2 weeks) bone grafting to allow for resolution of the giant cell inflammatory reaction of the pseudosheath (group IV), a statistically significant increased bone graft survival was achieved (p less than 0.001). The study demonstrates that the increased vascularity in the pseudosheath and in the expanded soft-tissue envelope significantly increased bone graft survival only when bone grafting was delayed.     

Tanshinon IIA Injection Accelerates Tissue Expansion by Reducing the Formation of the Fibrous Capsule

The tissue expansion technique has been applied to obtain new skin tissue to repair large defects in clinical practice. The implantation of tissue expander could initiate a host response to foreign body (FBR), which leads to fibrotic encapsulation around the expander and prolongs the period of tissue expansion. Tanshinon IIA (Tan IIA) has been shown to have anti-inflammation and immunoregulation effect. The rat tissue expansion model was used in this study to observe whether Tan IIA injection systematically could inhibit the FBR to reduce fibrous capsule formation and accelerate the process of tissue expansion. Forty-eight rats were randomly divided into the Tan IIA group and control group with 24 rats in each group. The expansion was conducted twice a week to maintain a capsule pressure of 60 mmHg. The expansion volume and expanded area were measured. The expanded tissue in the two groups was harvested, and histological staining was performed; proinflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) and transforming growth factor-β (TGF-β) were examined. The expansion volume and the expanded area in the Tan IIA group were greater than that of the control group. The thickness of the fibrous capsule in the Tan IIA group was reduced with no influence on the normal skin regeneration. Decreased infiltration of macrophages, lower level of TNF-α, IL-6, IL-1β and TGF-β, less proliferating myofibroblasts and enhanced neovascularization were observed in the Tan IIA group. Our findings indicated that the Tan IIA injection reduced the formation of the fibrous capsule and accelerated the process of tissue expansion by inhibiting the FBR.     

Alterations in skin properties during rapid and slow tissue expansion for breast reconstruction.

This study comprises 23 women who had had mastectomies because of breast cancer. They were randomly divided into two groups when they were admitted for breast reconstruction by tissue expansion. The first group was expanded rapidly, i.e., every day, and the other group was expanded slowly, i.e., every week. There were no other differences in the treatment between the two groups. Three months after completion of expansion, the expander was replaced by a permanent prosthesis. The follow-up time was up to 6 months after the second operation. Three different parameters--distensibility, elasticity, and hysteresis--were measured noninvasively on the breast skin and at a control site on several occasions throughout the treatment. During the treatment period there were no differences in skin properties between rapidly and slowly expanded patients. Of the three parameters, distensibility showed the most prominent changes: decreasing during the expansion period, increasing after the expander had been replaced by a permanent prosthesis, and decreasing during the following 6 months. Elasticity did not change significantly, except decreasing after insertion of the permanent prosthesis, and the hysteresis increased at the same time. These findings indicate that tissue expansion alters breast skin only to a small extent and that the mechanical resistance sometimes encountered during tissue expansion is due to deeper structures such as underlying muscles or capsule formation.     

Easy tissue expansion of prelaminated mucosa-lined flaps for cheek reconstruction in a canine model

In head and neck reconstruction, there is sometimes the need for a skin flap lined with mucosa. The object of this study was to determine whether small pieces of mucosa grafted onto the undersurface of a skin flap can be expanded in a reasonable time to provide the material required to reconstruct a full-thickness cheek defect as a free flap. The study consisted of two phases: prelamination and expansion of the flap, and vascularized free-tissue transfer of the flap. Six adult mongrel dogs were used. First, a 5 x 10-cm flap based on the saphenous vessels was elevated on the lower leg, and then four 1 x 2-cm pieces of mucosa harvested from the tongue were grafted onto the undersurface of the flap. A tissue expander (5 x 10 cm) was then placed under the flap, and the incision was closed primarily. The expanders were initially filled with just enough normal saline to obliterate dead space immediately after surgery. The expansion was continued twice weekly for 3 weeks until sufficient expansion was obtained. Two of six flaps were followed for an additional 6 weeks after the 3-week expansion period to observe whether additional mucosa could be obtained. After measurement of the mucosal area, each flap was transferred as free flap to reconstruct an iatrogenic cheek defect. The increase of mucosal surface area was compared with the original graft, and differences were analyzed using the paired t test. All flaps were successfully expanded without any complications. Histologic evaluation revealed that grafted mucosa took well without evidence of graft necrosis, and the intergraft area was covered with histiocytes. Angiography revealed well-defined vascular structures covering the entire area of the flap. The new mucosal area (23.5 +/- 2.4 cm2) was significantly larger than the original mucosal graft (8.7 +/- 0.9 cm2) (p < 0.001). The net increase of the mucosal area was 172.9 +/- 32.4 percent. The increase of mucosal area in two flaps, following a 6-week consolidation period after 3 weeks of expansion, was only slightly greater (25.9 +/- 1.3 cm2) than those without the consolidation period (22.3 +/- 1.8 cm2). This increase of the mucosal area appears to be related to the amount of expansion, and not to the length of the consolidation period. The flaps were successfully transferred as free flaps to reconstruct the full-thickness cheek defects without major complications. Although a staged operation to allow flaps to mature is needed, the present procedure has the advantages of providing a mucosa-lined flap and allowing primary closure of the donor site. The authors conclude that expansion of this flap has great potential in reconstructive surgery.     

Training vs. body image: does training improve subjective appearance ratings?

The purpose of this study was to determine if a short-term exercise program (6 weeks) could improve subjective physical appearance ratings. Twenty-five previously sedentary adult men (aged 18-40 years) were randomly assigned to one of 3 training groups: cardiovascular, strength, or control. Subjects participating in an exercise group trained for an average of 34 minutes, 3 times per week. All subjects were pre- and posttested to determine body composition, strength, and cardiovascular fitness. Subjects were also digitally photographed from 4 angles. The photographs were rated by the subjects and by a panel of 6 judges using an analog scale. There was no significant difference in the groups by trials interaction effect for pre- and post-Vo(2)max, percent fat, total lean tissue, percent limb fat, percent trunk fat, lean trunk tissue, or lean limb tissue. The subjects rated themselves higher than the panel, with average scores of 4.74 vs. 3.46, 4.26 vs. 3.10, and 4.61 vs. 3.49 for the cardiovascular, strength, and control groups, respectively (p < 0.05). The men of the panel rated the subjects significantly higher than did the women, with average scores of 4.61 vs. 2.31, 4.13 vs. 2.06, and 4.53 vs. 2.18 for the cardiovascular, resistance, and control groups, respectively (p < 0.05). This study showed that a 6-week training program did not change self-rated or panel-rated appearance scores.     

An accelerated approach to tissue expansion for breast reconstruction: experience with intraoperative and rapid postoperative expansion in 370 reconstructions

Breast reconstruction with tissue expansion is a well-established technique that offers satisfactory aesthetic results with minimal patient morbidity. The traditional period of expansion, however, continues to be a significant source of patient inconvenience and dissatisfaction. The objective of this study was to develop and evaluate a protocol for rapid tissue expansion. A total of 370 breast reconstructions in 314 patients who underwent rapid tissue expansion were retrospectively reviewed. Contraindications to rapid expansion were considered to be previous radiation, mastectomy skin flaps of questionable viability, and an excessively tight skin envelope. All expanders were placed submuscularly and filled to 40 to 50 percent of tissue expander volume. Office expansion was undertaken within 10 to 14 days after the operation and continued on a weekly basis. Each expansion was limited by patient tolerance up to a maximal pressure of 40 mm of water or a volume of 120 cm3. Expansion was considered complete once the expanded breast was 30 to 50 percent larger than the contralateral breast. If required, postoperative chemotherapy was given during the expansion period. Mean patient age was 48 years (range, 23 to 73 years). Two hundred fifty-eight patients had unilateral reconstructions. Three hundred two patients had immediate reconstruction. Mean tissue expander size was 583 cm3 (SD, 108 cm3). Mean intraoperative expansion was 271 cm3, or 46 percent (SD, 9 percent) of the tissue expander size. The first expansion was started 12 days (SD, 3 days) after the operation. The mean volume of each expansion was 88 cm3 (SD, 23 cm3). Expansion was completed in 4.7 office visits (SD, one visit). Mean final expander volume was 672 cm3 (SD, 144 cm3). The expanders were overexpanded by 15.3 percent (SD, 8.4 percent). The mean time between expander placement and the final expansion was 6.6 weeks (SD, 3 weeks). The overall complication rate was 4 percent. Ten patients developed cellulitis, five patients had hematomas requiring drainage, and one expander became exposed. A total of eight expanders were removed: four for cellulitis, one for a hematoma, one because of locally recurrent disease, one because of expander exposure, and one at the patient's request for no medical reason. Intraoperative and rapid postoperative tissue expansion is a safe and reliable technique that offers a significant improvement over conventional techniques. In this accelerated protocol, expansion may be completed in less than 7 weeks. The result is decreased patient morbidity and delays in adjuvant therapy at no detriment to the final surgical outcome.     

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.     

Effects of boric acid feeding on the oxidative stress parameters in testes,sperm parameters and DNA damage in mice

This study was aimed to determine the effects of boric acid on oxidative stress, testicular tissue and spermatozoon DNA. Experiments were performed with Swiss Albino mice divided equally into two groups based on the tratment period: one for 4 and the other for 6-week duration. These groups were further divided into subgroups as Control and those administered daily at oral doses of 115 mg/kg, 250 mg/kg and 450 mg/kg of boric acid. Then, testicular tissue were examined postmortem and analyzed using ex-vivo biochemical tools for oxidative stress, spermatozoon membrane integrity, sperm motility and live cell rate (%). In both 4 and 6-week groups, v. seminalis weight, membrane integrity, motility, live cells and GSH levels exhibited a decreasing trent compared to the controls. In addition, 6-week group had a decrease in SOD level. MDA level was higher in controls in both 4 and 6-week groups. Spermatozoon DNA was intact in the 4-week group, but damaged in the 6-week group, and the degree of the damage dependent on the administered dose. Boric acid induces oxidative stress in testicular tissue, and its long-term application (only 6 weeks) caused damage in spermatozoon DNA.     

Continuous versus intraoperative expansion in the pig model.

Continuous tissue expansion utilizing a continuous infusion device that maintains a constant expander pressure was previously demonstrated to be feasible and successful in obtaining rapid tissue expansion in a canine model. Intraoperative tissue expansion has been described and has gained some clinical acceptance as a method to gain rapid expansion. We compared the efficacy of continuous tissue expansion versus intraoperative tissue expansion in a piglet model. After completing a pilot study, continuous tissue expansion was performed in six pigs (14.5 to 20 kg) on one flank over a 3-day period utilizing an improved prototype device; at the termination of continuous tissue expansion, intraoperative tissue expansion was performed on the opposite flank. There were no complications or continuous tissue expansion device malfunctions. Intraoperative tissue expansion gave a true gain in area of 7.4 percent, while continuous tissue expansion produced a 22 percent gain (p < 0.02). When the effects of both recruitment and expansion were added, continuous tissue expansion gave a dividend of 286 percent versus 192 percent for intraoperative tissue expansion (p < 0.01). Biomechanically, intraoperative tissue expansion skin showed few differences from unexpanded skin, while continuous tissue expansion skin showed a significant increase in stress relaxation (47.78 versus 38.74) and decrease in breaking strength. Histologic analysis revealed some epidermal hyperplasia and inflammation surrounding the continuous tissue expansion expander and some vascular congestion over the intraoperative tissue expansion expander. We conclude that continuous tissue expansion is superior to intraoperative tissue expansion and that the prototype device may be useful clinically.     

Effect of a sprint training protocol on growth rate, conversion efficiency, food consumption and body composition of rainbow trout, Salmo gairdneri Richardson

Rainbow trout were sprint-trained (30 s duration) once or twice on alternate days for a period of 6 weeks. Swim speed for the first 10 s of a training bout averaged 11.4 bls for group 2 (trained once) and 10.2 bl s ⁻¹ for group 3 (trained twice). Food consumption, growth rate and conversion efficiency were measured over 2-week periods. Food consumption was 31-38% less for the trained groups than for the control group (group 1). The growth rates of control and trained fish increased gradually over the training period. The growth rate of trained fish was always significantly less (48-81%) than that of control fish. Although conversion efficiency was significantly less for group 3 at the beginning of training, no other significant differences in conversion efficiency were recorded. Maintenance rations were high in the initial period for all groups, but were lower than the initial values in the second and third periods. While condition factor was significantly lower for the trained groups, there were no differences in percent tissue protein, lipid, or moisture.     

Technical variations of the bipedicled TRAM flap in unilateral breast reconstruction: effects of conventional versus microsurgical techniques of pedicle transfer on complications rates

In cases of unilateral breast reconstruction with a transverse rectus abdominis musculocutaneous (TRAM) flap, poorly perfused tissue, which is normally excised to avoid subsequent fat necrosis, must sometimes be used to achieve adequate breast size and projection. In such cases, incorporation of a second vascular pedicle into the flap design improves perfusion. The authors retrospectively examined their experience with bipedicled TRAM flap-based unilateral breast reconstruction to determine whether the use of microsurgical rather than conventional (nonmicrosurgical) techniques for flap transfer resulted in lower incidences of flap-site fat necrosis and donor-site hernia/bulge. The authors retrospectively reviewed the medical records of all patients who underwent unilateral breast reconstruction with a bipedicled TRAM or deep inferior epigastric perforator flap between January of 1991 and March of 2001. Group 1 consisted of patients who had undergone flap transfer using a conventional technique for both pedicles; group 2, patients who had flap transfer using a conventional technique for one pedicle and a microsurgical technique for the other; and group 3, patients who had flap transfer using a microsurgical technique for both pedicles. Of the 863 patients identified, 72 (8.3 percent) had undergone reconstruction using a bipedicled flap. There were 43 patients in group 1, 24 patients in group 2, and five patients in group 3. Only one case of total flap loss had occurred (group 1). Partial flap loss occurred in two patients in group 1 (5 percent) and three patients in group 2 (13 percent). Fat necrosis occurred more frequently in groups 1 (23 percent) and 2 (29 percent) than in group 3 (0 percent) (p = 0.5, Fisher's exact test). Similarly, bulge or hernia was more common in groups 1 (12 percent) and 2 (4 percent) than in group 3 (0 percent) (p = 0.6, Fisher's exact test). In this study, patients who received a bipedicled TRAM flap using microsurgical techniques alone (group 3) appeared to have better flap perfusion and less frequent hernia/bulge than did patients who underwent flap transfer using conventional (group 1) or combined techniques (group 2). However, these differences were not statistically significant, and this trend must be verified in a larger study.     

Balloon expansion of the pectoralis major muscle flap in sternoplasty: a biomechanical and histologic study in a rat model

The pectoralis major advancement flap is currently the most popular technique for reconstruction of the anterior chest in patients with sternotomy wounds. Recently, the SpaceMaker balloon was introduced for rapid expansion of the pectoralis major muscle intraoperatively. The aim of the present study was to investigate the biomechanical and histologic effects of this expansion technique in a rat model. The upper 2 cm of the sternum was resected in 54 male rats. Reconstruction with balloon-assisted pectoralis muscle expansion was performed in 24 rats (study group). Another 24 rats underwent reconstruction with simple muscle advancement without expansion. Submuscular insertion of a catheter for expansion, without inflation, was performed in the remaining six rats (sham group). Rats were killed either immediately or 2 to 4 weeks after surgery. Thirty-eight rats, including 16 after reconstruction with expansion, 16 after reconstruction without expansion, and six in the sham group, were killed immediately after surgery. Sixteen rats were killed 2 to 4 weeks after surgery, eight rats for each reconstruction technique. Before the animals were killed, the biomechanical properties of the muscles were tested with weights to calculate stiffness (in newtons per meter) and compliance gain (in percent). After the animals were killed, biopsy specimens were obtained for histologic analysis. Results indicated significantly lower muscle stiffness in the study group compared with the others immediately after surgery (p = 0.0000), although the difference failed to achieve statistical significance 2 to 4 weeks later (p = 0.76). In the study group, the compliance gain was 74.4 percent immediately after surgery but only 3.4 percent 2 weeks to 1 month postoperatively. Histologic examinations in all groups immediately and 2 to 4 weeks after surgery revealed regular muscle striation with no signs of inflammation. The elastic stiffness of the rat pectoralis major muscle is significantly reduced following rapid intraoperative expansion and returns to normal 2 to 4 weeks later.