Biomedical subjects
Publications and source records attributed to L Scott Levin.
Extravasation injury is a common event in pediatric intensive-care units. This is the first report of successful utilization of the prepuce as a skin graft to reconstruct a full thickness skin necrosis due to a phenobarbital extravasation to the forefoot of a newborn.
Suture anchors have been commercially developed to facilitate stable attachment of soft tissues to bone. Although their use is well characterized in orthopedic literature, suture anchors may also be of benefit in the reconstruction of large soft tissue defects by plastic surgeons. Suture anchors (Mitek Surgical Products, Inc., Westwood, MA) were used to fasten pedicled muscle flaps to exposed bone in 7 patients at Duke University undergoing reconstruction of large soft tissue defects. The suture anchor appeared to provide stability for the advancement flap, and there were no suspected postoperative muscle dehiscences or suture breakages. The suture anchor provides an easy, secure method to attach soft tissue to exposed bone, and preliminary experience appears to support their use in certain soft tissue reconstruction procedures by plastic surgeons. Suture anchors should be reserved for cases in which a large muscle flap is needed to cover exposed bone and poses a risk of shearing away from the bone, or adequate periosteum and soft tissue is not available for standard suture techniques.
Fibrous capsule formation around implants remains a difficult problem that has been studied for decades. The etiology is elusive, but the end result is the deposition of a dense collagenous capsule around implanted materials. The purpose of this study was to determine the effects of a type I collagen synthesis inhibitor, halofuginone, on fibrous capsule formation around implanted materials. Silastic disks were implanted subcutaneously into 4 groups of adult male rats for up to 8 weeks. Group 1 received drug throughout the study, group 2 received drug during the first half only, group 3 received drug during the second half only, and the control group received no drug. Implants were removed and histology of the capsules was examined. A collagen index score was calculated from digital images of trichrome-stained histologic sections, which permitted semiquantitative comparison of collagen content among the 4 groups. The collagen index values clearly indicate that halofuginone effectively inhibited collagen deposition within the capsule around the implanted disks. Halofuginone treatment also resulted in a decrease in the collagen index score in rat skin, indicating that halofuginone may affect preexisting collagenous structures. The ability of halofuginone to inhibit collagen deposition in new and preexisting fibrous capsules suggests that it may be a useful adjunct to minimize the formation of capsules around implantable prostheses.
OBJECTIVE: Abbe and Payr introduced vascular techniques and devices to facilitate vessel anastomosis over a century ago. Obora published the idea of a sutureless vascular anastomosis with use of magnetic rings in 1978. The purpose of this study was to assess the performance of a new magnetic device to perform a side-to-side arteriovenous anastomosis in a dog model. MATERIAL AND METHODS: Male fox hounds (25 kg) were treated preoperatively and daily postoperatively with clopidogrel bisulfate (Plavix) and aspirin. The femoral artery and vein were exposed unilaterally in 3 dogs and bilaterally in 4 dogs (n = 11 anastomoses). A 4-mm arteriotomy was performed, and 1 oval magnet 0.5 mm thick was inserted into the lumen of the artery and a second magnet was applied external to the artery, compressing and stabilizing the arterial wall to create a magnetic port. An identical venous magnetic port was created with another pair of oval magnets. When the 2 ports were allowed to approach each other, they self-aligned and magnetically coupled to complete the arteriovenous anastomosis. Patency was assessed for the first hour with direct observation, again after 9 weeks with duplex ultrasound scanning, and at 10 weeks under direct open observation. The anastomoses were explanted after 10 weeks. Hydrodynamic resistance was measured ex vivo on the final 8 anastomoses by measuring the pressure drop across an anastomosis with a known flow rate. RESULTS: After implantation, very high flow created visible turbulence and palpable vibration. All 11 anastomoses were patent under direct observation and palpation. Ten of 11 anastomoses were clearly patent on duplex scans, and patency of 1 anastomosis was questionable. Hydrodynamic resistance averaged 0.73 +/- 0.33 mm Hg min/mL (mean +/- SEM). CONCLUSIONS: Vascular anastomoses performed with magnets demonstrated feasibility; exhibited 100% patency after 10 weeks in a dog arteriovenous shunt model; lacked apparent aneurysm or other potentially catastrophic failure; demonstrated remodeling of the vessel wall after several weeks to incorporate the magnets, making the magnetic force unnecessary; and warrants further study in vessels with different sizes, flow rates, and locations. CLINICAL RELEVANCE: We present a magnet-based device used to perform side-to-side peripheral vascular anastomoses. Its advantages include the ability to anastomose vessels without requiring circumferential surgical exposure. Vascular anastomosis performed with these magnets demonstrated 100% patency in the dog, lacked apparent aneurysm or other potentially catastrophic failure, and demonstrated remodeling of the vessel wall after several weeks, to incorporate the magnets, making indefinite retention of field strength unnecessary. This technique could enable minimally invasive procedures, such as complex reconstructive and revascularizing surgery, and warrants further study in vessels with different sizes, flow rates, and locations.
Staphylococcus aureus is the single most common cause of osteomyelitis in humans. Incidences of osteomyelitis caused by S. aureus have increased dramatically in recent years, in part due to the appearance of community-acquired antibiotic resistant strains. Therefore, understanding the pathogenesis of this organism has become imperative. Recently, we have described the surprising ability of bone-forming osteoblasts to secrete a number of important immune mediators when exposed to S. aureus in vitro. In the present study, we provide the first evidence for the in vivo production of such molecules by osteoblasts during bacterial infection of bone. These studies demonstrate the expression of the key inflammatory cytokine interleukin-6 by osteoblasts in organ cultures of neonatal mouse calvaria, and in vivo using a mouse model that closely resembles the pathology of trauma-induced staphylococcal osteomyelitis, as determined by confocal microscopic analysis. Importantly, we have established the clinical relevancy of these findings in infected human bone tissue from patients with S. aureus-associated osteomyelitis. As such, these studies demonstrate that bacterial challenge of osteoblasts during bone diseases, such as osteomyelitis, induces cells to produce inflammatory molecules that can direct appropriate host responses or contribute to progressive inflammatory damage.
The anterolateral thigh flap is an extremely versatile flap first described in 1984. The flap is based on either a septocutaneous or musculocutaneous perforator of the descending branch of the lateral circumflex femoral system. It can be designed as a skin and subcutaneous flap, fasciocutaneous, or musculocutaneous flap. Furthermore, it can be harvested as a sensate flap by taking the lateral cutaneous nerve of the thigh. Technique for harvesting the flap is described in detail. Complications include flap failure and donor site morbidity. Due to its versatility, the anterolateral thigh flap is particularly useful for upper extremity reconstruction.
Partial transverse rectus abdominis myocutaneous (TRAM) flap loss in breast reconstruction can be a devastating complication for both patient and surgeon. Surgical delay of the TRAM flap has been shown to improve flap viability and has been advocated in "high-risk" patients seeking autogenous breast reconstruction. Despite extensive clinical evidence of the effectiveness of surgical delay of TRAM flaps, the mechanisms by which the delay phenomenon occurs remain poorly understood. To examine whether angiogenic growth factors such as basic fibroblast growth factor (bFGF) may play a role in the delay phenomenon, the authors studied the expression of bFGF in rat TRAM flaps subjected to surgical delay. Thirty-five female Sprague-Dawley rats were randomly assigned to one of four TRAM flap groups: no delay (n = 6), 7-day delay (n = 12), 14-day delay (n = 10), or 21-day delay (n = 7). Surgical delay consisted of incising skin around the perimeter of the planned 2.5 x 5.0-cm TRAM flap followed by ablation of both superior epigastric arteries and the left inferior epigastric artery, thus preserving the right inferior epigastric artery (the nondominant blood supply to the rectus abdominis muscle of the rat). TRAM flaps were then elevated after 7, 14, and 21 days of delay by raising zones II, III, and IV off the abdominal wall fascia. Once hemostasis was assured, the flaps were sutured back in place. All flaps were designed with the upper border of the flap 1 cm below the xiphoid tip. Three days after the TRAM procedure, postfluorescein planimetry was used to determine percent area viability of both superficial and deep portions of TRAM flaps. All rats were euthanized and full-thickness TRAM specimens were taken from zones I, II, III, and IV for enzyme-linked immunoabsorbent assay analysis of bFGF levels. Statistical testing was done by t test (percent viability) and two-way analysis of variance (bFGF levels). All delayed flaps had significantly higher bFGF levels when compared with all nondelayed control flaps (p < 0.05). The bFGF levels were not different in the rats that received TRAM flaps 7, 14, or 21 days after delay surgery. There was also no significant difference in bFGF levels among zones I through IV. Control rats had more peripheral zone necrosis compared with all delayed TRAM rats. All delayed flaps had a significantly higher area of flap viability superficially than nondelayed control flaps (p < 0.05). There was no difference in deep flap viability. Surgical delay of rat TRAM flaps is associated with improved flap viability and significantly elevated levels of bFGF over nondelayed TRAM flaps at postoperative day 3 after TRAM surgery. The increases in bFGF noted at this time point suggests that bFGF may play a role in the improved TRAM flap viability observed after delay surgery. Further investigation is needed to evaluate the role bFGF may play in the delay phenomenon.
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Vascular Endothelial Growth Factor (VEGF), a potent angiogenic, mitogenic and vascular permeability enhancing protein, appears to improve survival of ischemic flaps independent of its route of administration. The purpose of this study was to examine VEGF protein expression in biopsies of surgical flaps with immunohistochemical techniques. In 6 male Yorkshire-type pigs, 10 cm x 15 cm Latissimus dorsi musculocutaneous flaps were elevated bilaterally. Flap zones I, II, and III were established according to their distance from the vascular pedicle. After isolation of the thoracodorsal artery and vein, one flap was randomly assigned to ischemia by temporary occlusion of the vascular pedicle. Ischemia (4 hours) was followed by 2 hours of reperfusion (ischemia group, n = 6). The contralateral (nonischemic) flap served as a control (control group, n =6). Skin and muscle biopsies of flaps were taken at the end of the protocol for immunohistochemical staining using a VEGF antihuman monoclonal antibody. Epidermis of flap skin did not demonstrate VEGF-positive staining, but the dermis and subcutaneous tissue did. Muscle components of biopsies demonstrated staining of interfascicular septa and staining of myocytes. A semi-quantitative scoring system with a scale of 0 to 3 was used for grading of immunohistochemical staining. In skin, areas adjacent to the flap showed an overall mean VEGF staining score of 0.7. All zones of ischemic flaps showed increased mean immunohistochemical staining for VEGF (scores = 1.2, 1.6, and 1.4 in zones I, II, and III, respectively). In muscle, however, only zone I showed increased VEGF immunohistochemical staining from 0.7 in adjacent areas to 1.7 in ischemic flaps. The results indicate only moderate endogenous up-regulation of VEGF in flaps, supporting the utilization of exogenous VEGF as an adjunct in microsurgical therapy.
Complex regional pain syndrome, vasospastic disorders, and hyperhidrosis are chronic and debilitating upper extremity problems. Twenty-nine consecutive patients treated with thoracoscopic sympathectomy are presented. Diagnoses included complex regional pain syndrome, hyperhidrosis, Buerger's disease, Raynaud's disease, and peripheral vascular disease. All patients with hyperhidrosis had complete symptom resolution. Patients with Buerger's and Raynaud's disease had excellent/good results. Six patients with complex regional pain syndrome had excellent or good relief; the remaining six patients had varying degrees of recurrence. A statistically significant association was noted between duration of complex regional pain syndrome prior to sympathectomy and outcome. Thoracoscopic sympathectomy is an effective treatment for hyperhidrosis and vasospastic disorders. Although the results for complex regional pain syndrome are not uniformly excellent, this technique offers promise in the treatment of this difficult problem.
PURPOSE: Perineal pressure ulcers are a common and devastating complication for paralyzed or chronically bedridden patients. Controversy exists on the benefit of fecal diversion for the treatment and prevention of these ulcers. This study compared outcomes in bed-bound patients with pressure ulcers who electively underwent fecal diversion with those who did not. METHODS: A retrospective review was performed on all disabled patients who underwent surgery for medically intractable pressure ulcer from 1993 to 2001. Charts were divided into the colostomy group or noncolostomy group. Recurrence rates, healing times, morbidity and mortality, and number of reoperations were calculated for each group. Additionally, stoma patients were interviewed for quality of life assessment. RESULTS: Sixty-seven patients were treated during the study period (colostomy, n = 41; noncolostomy, n = 26). The majority of colostomies were performed laparoscopically, with a 9.7 percent incidence of postoperative complications. The ulcer recurrence rate was lower in the treated colostomy group (43 percent) compared with the noncolostomy group (69 percent; P < 0.05). In addition, noncolostomy patients had longer healing times (7 vs. 3 months; P < 0.05), and this group required more ulcer operations than the stoma patients did. Quality of life and bowel care were much improved by the colostomy. CONCLUSIONS: Stoma construction is a safe procedure with low morbidity and mortality that helps heal pressure ulcers and decreases the incidence of recurrence. Additionally, laparoscopic stoma construction represents a technical advance that may reduce operative complications that have been previously reported with open fecal diversion.
OBJECTIVE: Poststernotomy mediastinitis, although infrequent, is a potentially life-threatening complication of cardiac surgery that continues to have a significant morbidity and mortality despite aggressive therapy. Vacuum-assisted closure uses controlled suction to provide evacuation of wound fluid, decrease bacterial colonization, stimulate granulation tissue, and reduce the need for dressing changes. METHODS: One hundred two patients from Duke University Hospital, The Durham Veterans Administration Hospital, and referring institutions underwent vacuum-assisted closure treatment. There were 63 men and 39 women, with a mean age of 67. The infection was noticed between postoperative days 8 and 34, at which time the wounds were opened and debrided. RESULTS: Ninety-six of the 102 patients received vacuum-assisted therapy while the remaining 6 underwent daily multiple dressing changes without vacuum-assisted therapy. Fifty-three of the 96 patients required only sternal debridement, followed by wound vacuum therapy and closure by secondary intention, while the remaining 43 had an additional procedure. Of these, 33 patients underwent omental transposition and 10 patients had a pectoralis flap. The length of stay for all patients was 27 +/- 12 days. This was related in part to intravenous antibiotics. Hospital mortality for all patients was 3.7% (4 patients). Two of these patients underwent vascular flap and succumbed to multisystemic organ failure, while the other 2 received only wound vacuum therapy following debridement and succumbed to overwhelming sepsis. CONCLUSION: Vacuum-assisted drainage is an effective therapy for mediastinitis following debridement or before placement of a vascularized tissue flap.
Based on the dissection of 20 fresh cadaver legs, the authors have further defined the vascular anatomy of the peroneal artery and its cutaneous perforator vessels. They identified a total of 95 cutaneous perforators of the peroneal artery greater then 0.3 mm in 20 legs. The average number of cutaneous perforators was 4.8 (range: three to seven) per leg. The cutaneous perforators were either musculocutaneous (34 percent) or septocutaneous (66 percent). The musculocutaneous perforators were found predominantly in the upper two-thirds of the lower leg; the septocutaneous perforators were located in the lower two-thirds of the leg. The external diameter of the cutaneous perforators at the posterior border of the fibula was 0.6 (range: 0.3 to 1.5) mm. The blood supply of the proximal fibula epiphysis and fibula head was found not to be in the vascular territory of the peroneal artery. These results are the basis of the established osteoseptocutaneous fibula transfer, the peroneal fasciocutaneous free flap, and the double-paddle peroneal tissue transfer that all require dissection of highly vascularized tissue adjacent to the fibula, in order to reach the peroneal vessels. These constant anatomic findings should encourage the surgeon to harvest skin flaps just to the level of the posterior border of the fibula, thereby creating perforator flaps based on the peroneal system.
Tissue expansion in the upper extremity is a valuable technique with expanding indications and expected outcomes. The primary indications are coverage problems after trauma, but the technique is also applicable to defects caused by treatment of hemangioma, nevi, tattoos, or hypertrophic scars as well as correction of unstable tissue or as an alternative to free tissue transfer. The advantage of expansion-specifically, match in tissue texture and retention of sensibility-may be more important in the hand and upper extremity than in other areas. The inevitable capsule that forms around the expander does provide a smooth gliding surface for tendons in the forearm and wrist. In conclusion, tissue expansion of the upper extremity offers the surgeon the ability to improve cosmesis in one location without having to sacrifice cosmesis at a second site.
There are limited reconstructive options for segmental bone defects of the upper extremity larger than 6 cm in length, especially when associated with soft-tissue loss. Among the limited treatment options the osteoseptocutaneous fibular transplant is well established. The anatomy is reliable, the blood supply is constant, and the operative technique can be standardized. The advantage of including skin with the vascularized fibular transplant is twofold. First, the skin paddle can be used to augment the soft-tissue envelope. Second, the skin paddle serves as a monitor, providing an immediate, ongoing, and reliable method to monitor the blood flow to the graft. The osteoseptocutaneous fibular transplant proved to be an effective treatment of combined segmental bony and soft-tissue defects of the forearm and humerus.
Exogenous administration of vascular endothelial growth factor (VEGF) improves long-term viability of myocutaneous flaps. However, endogenous expression of this substance in flaps following ischemia-reperfusion injury has not been reported previously. Endogenous production of VEGF was measured in myocutaneous pig latissimus dorsi flaps after ischemia-reperfusion injury. Latissimus dorsi myocutaneous flaps (15 x 10 cm) were simultaneously elevated bilaterally in six Yorkshire-type male pigs (25 kg). Before elevation, three flap zones (5 x 10 cm) were marked according to their distance from the vascular pedicle. After isolation of the vascular pedicle, ischemia-reperfusion injury was induced in one flap by occlusion of the thoracodorsal artery and vein for 4 hours, followed by 2 hours of reperfusion. The contralateral flap served as a control. Perfusion in each zone was monitored by laser Doppler flowmetry at baseline, during ischemia, and during reperfusion. At the end of the protocol, skin and muscle biopsies of each flap zone and adjacent tissues were obtained for later determination of VEGF protein levels. VEGF concentrations were quantified using the Quantikine human VEGF immunoassay. Skin perfusion was similar among all flap zones before surgery. Flow fell in all flaps immediately after flap elevation. After 4 hours of ischemia, blood flow in the ischemic flaps was significantly decreased (p < 0.05) compared with nonischemic control flaps. After 2 hours of reperfusion, flow in ischemic flap skin recovered to levels similar to those in control flaps. VEGF protein concentrations in muscle tissue exceeded concentrations in skin and decreased from zones 2 to 3 in control and ischemic flaps. No significant differences in VEGF concentrations between ischemic and control muscle zones were observed. However, the concentration of VEGF in all muscle zones was significantly higher (p < 0.05) than muscle adjacent to the flap. Concentrations in skin zones 1 and 2 were significantly higher (p < 0.05) in ischemic flaps than in control flaps, but levels in zone 3 (most ischemic flaps) showed no significant difference.
The popularity of the sural artery flap has increased markedly throughout the years, and favorable results are reported almost uniformly. Previous publications have mainly presented results of small groups and of predominantly younger patients with posttraumatic defects, or they have reported technical modifications of the sural artery flap. The authors have increasingly used the reversed sural artery flap in a high-risk, critically multimorbid, and older patient population, and in contrast to the results of other authors, a considerable necrosis rate of 36 percent was seen. For the first time, a detailed, critical, retrospective complication analysis of 70 sural artery flaps is presented. The results reveal the following risk factors, which can potentially impair successful defect coverage and thus contribute to flap complications: concomitant diseases, particularly diabetes mellitus; peripheral arterial disease or venous insufficiency, which increase the risk of flap necrosis five-fold to six-fold; and patient age of over 40 years, because of an increased rate of comorbidity, underlying osteomyelitis, and the use of a tight subcutaneous tunnel. However, age alone did not seem to represent a risk factor by itself. Given the results of the analysis, the operative procedure was altered, as follows. In cases in which a lesser saphenous vein cannot be found, a delay procedure is recommended, or the flap is not utilized. In addition, an external fixation device seems to facilitate postoperative care markedly without adding specific complications; it is recommended in most patients. This analysis emphasizes specific risk factors that result in higher complication rates of the sural artery flap, and it leads to more realistic and appropriate expectations for this flap.
The effect of sepsis on neovascularization in fractures that follows open fractures is important to the understanding of bone and soft-tissue healing. An animal model was designed that mimics the open fracture and the clinical repair of the human, high-energy open fracture. Vascular endothelial growth factor (VEGF) mRNA levels in canine bone samples were determined in samples from days 0 and 7. Canine right tibiae were fractured with a penetrating, captive-bolt device and then repaired in a standard clinical fashion using an interlocking intramedullary nail. Animals were subject to one of the following experimental protocols: tibial fracture (group I, n = 3); tibial fracture and Staphylococcus aureus inoculation at the fracture site (group II, n = 3); and tibial fracture and S. aureus inoculation with a rotational gastrocnemius muscle flap (group III, n = 3). Bone samples were harvested on days 0 and 7 and prepared for reverse transcriptase polymerase chain reaction assay. Primers for VEGF were commercially prepared and assay products were sequenced. The assay products were associated with Genebank VEGF mRNA sequences. VEGF mRNA levels increased significantly in the fracture-alone group from day 0 to day 7 (n = 3, p < 0.05). In the fracture and S. aureus group (group I), VEGF mRNA expression decreased 79 percent (p < 0.05). In animals with fractures inoculated with S. aureus and a transpositional muscle flap (group III), VEGF mRNA expression was increased 38 percent from day 0 to day 7 (p < 0.05) and was similar to the increase observed in the fracture-alone group. These results demonstrate that S. aureus decreased the normal increase of VEGF mRNA expression during bone wound healing. Use of the transpositional muscle flap in the presence of S. aureus increased VEGF mRNA expression over time to the expression pattern observed in the fracture-alone group. This experimental model demonstrates that specific biological signals and cellular pathways are influenced by bacterial infection and type of surgical closure.