Comparison of AlloDerm and AlloMax tissue incorporation in rats.

BACKGROUND: Human acellular dermal matrices (HADMs) are used in a variety of settings. AlloMax is a new HADM currently being used for breast reconstruction and hernia repair. We compared the in vivo tissue integration of AlloMax to AlloDerm, a well-studied HADM, in rats. METHODS: We implanted AlloDerm and AlloMax patches into subcutaneous pockets on the backs of 32 male Sprague-Dawley rats. The animals were killed after either 4 or 8 weeks, and the patches were recovered and stained for histopathologic analyses. Microscopic end points included patch thickness, vascularization, tissue in-growth, fibroblast proliferation, and inflammation. RESULTS: All animals completed the study without complications or infection. There were no significant differences in graft thicknesses at 4 and 8 weeks. Microscopically, at 4 weeks, AlloDerm sections had significantly more microvessels than AlloMax (P = 0.02). This disparity increased by 8 weeks (P < 0.01). Similarly, we found greater tissue in-growth and fibroblast proliferation in AlloDerm than AlloMax sections at 4 (P < 0.01) and at 8 (P < 0.01) weeks. Inflammatory infiltrates consisted of lymphocytes, histiocytes, eosinophils, and plasma cells. Deep graft infiltration by predominately lymphocytic inflammatory cells was significantly higher in AlloDerm than AlloMax grafts at 4 (P = 0.01) and 8 (P = 0.02) weeks. Graft necrosis was uncommon, but marginal fibrosis was similar in both. CONCLUSIONS: AlloDerm grafts had greater neovascularization, tissue infiltration, fibroblast proliferation, and inflammatory reaction than AlloMax grafts when placed subcutaneously in rats. AlloDerm may be better incorporated than AlloMax when placed in vivo.

The use of visible light spectroscopy to measure tissue oxygenation in free flap reconstruction.

The loss of a free flap is a feared complication for both the surgeon and the patient. Early recognition of vascular compromise has been shown to provide the best chance for flap salvage. The ideal monitoring technique for perioperative free flap ischemia would be noninvasive, continuous, and reliable. Visible light spectroscopy (VLS) was evaluated as a new method for predicting ischemia in microvascular cutaneous soft tissue free flaps. In an Institutional Review Board-approved prospective trial, 12 patients were monitored after free flap reconstructions. The tissue hemoglobin oxygen saturation (StO (2)) and total hemoglobin concentration (THB) of 12 flaps were continuously monitored using VLS for 72 hours postoperatively. Out of these 12 flaps 11 were transplanted successfully and 1 flap loss occurred. The StO (2 )was 48.99% and the THB was 46.74% for the 12 flaps. There was no significant difference in these values among the flaps. For the single flap loss, the device accurately reflected the ischemic drop in StO (2) indicating drastic tissue ischemia at 6 hours postoperatively before the disappearance of implantable Doppler signals or clinical signs of flap compromise. VLS, a continuous, noninvasive, and localized method to monitor oxygenation, appeared to predict early ischemic complications after free flap reconstruction.

An experimental design to study adipocyte stem cells for reconstruction of calvarial defects.

Autogenous osteogenic differentiated rat adipose stromal cells (ASCs) were used to repopulate cadaveric processed bone in a critical calvarial defect model to improve bone healing as compared with the standard treatment of cadaveric bone implantation alone. Forty-two skeletally mature Sprague-Dawley rats were randomized to 5 groups including bone graft only, bone/osteogenic differentiated ASCs, fibrin glue/osteogenic differentiated ASCs, and bone/fibrin glue/osteogenic differentiated ASCs; 2 animal calvarias were left empty. Adipose stromal cells were isolated from the inguinal fat pad of rats and differentiated into osteogenic cells, verified using von Kossa and alkaline phosphatase staining, and osteocalcin immunohistochemistry. These cells were added to sterilized, 8-mm cadaveric bone graft disks and placed back into calvarial defect for 6 weeks. The rat calvarias then underwent bone density analysis and histology. Intact cells were observed in the bone graft of the bone/osteogenic differentiated ASC group only. Islands of bone were seen in the bone-graft-only group, the bone/osteogenic differentiated ASC group, and the bone/fibrin/osteogenic differentiated ASC group. The bone-graft-only group and bone/osteogenic differentiated ASC group were similar in bone mineral density (1397 +/- 184.5 vs 1365 +/- 160.4). The bone/fibrin/osteogenic differentiated ASC group density was less than the bone and bone/osteogenic differentiated ASC groups at 835.2 +/- 319.5 (P < 0.001). Allograft bone scaffolds with autogenous osteogenic differentiated ASCs showed cellularity within the bone grafts and had larger bone islands. The presence of osteogenic differentiated ASCs did not increase overall bone density compared with bone graft only.

In vitro osteogenic differentiation of adipose stem cells after lentiviral transduction with green fluorescent protein.

BACKGROUND: Adipose-derived stem cells (ASCs) have the potential to differentiate into osteogenic cells that can be seeded into scaffolds for tissue engineering for use in craniofacial bone defects. Green fluorescent protein (GFP) has been widely used as a lineage marker for mammalian cells. The use of fluorescent proteins enables cells to be tracked during manipulation such as osteogenic differentiation within three-dimensional scaffolds. The purpose of this study was to examine whether ASCs introduced with GFP-encoding lentivirus vector exhibit adequate GFP fluorescence and whether the expression of GFP interfered with osteogenic differentiation of ASCs in both monolayer and three-dimensional scaffolds in vitro. METHODS: Primary ASCs were harvested from the inguinal fat pad of Sprague Dawley rats. Isolated ASCs were cultured and infected with a lentiviral vector encoding GFP and plated into both monolayers and three-dimensional scaffolds in vitro. The cells were then placed in osteogenic medium. Osteogenic differentiation of the GFP-ASCs was assessed using alizarin red S, alkaline phosphate staining, and immunohistochemistry staining of osteocalcin with quantification of alizarin red S and osteocalcin staining. RESULTS: The efficacy of infection of ASCs with a lentiviral vector encoding GFP was high. Cell-cultured GFP-ASCs remained fluorescent over the 8 weeks of the study period. The GFP-ASCs were successfully induced into osteogenic cells both in monolayers and three-dimensional scaffolds. Whereas the quanitification of alizarin red S revealed no difference between osteoinduced ASCs with or without GFP, the quantification of osteocalcin revealed increased staining in the GFP group. CONCLUSIONS: Transduction of isolated ASCs using a lentiviral vector encoding GFP is an effective method for tracing osteoinduced ASCs in vitro. Quantification data showed no decrease in staining of the osteoinduced ASCs.

Aesthetic outcomes in breast conservation therapy.

BACKGROUND: Since the National Surgical Adjuvant Breast and Bowel Project B06 (NSABP-B06) trial demonstrated equivalent survival outcomes between patients with breast cancer undergoing modified radical mastectomy versus lumpectomy and radiation, an increasing number of patients are seeking breast conservation therapy. Traditionally, only patients who have undergone total mastectomy have been referred for reconstruction. OBJECTIVE: The purpose of the study was to determine the number of dissatisfied patients treated with breast conservation therapy who have suboptimal cosmesis and should be referred for reconstruction. METHODS: After obtaining approval from the Institutional Review Board and patient consent, patients identified as more than 1 year posttreatment from breast conservation therapy (1999-2004) were interviewed and photographed. Data were gathered by use of a questionnaire that included patient aesthetic score, patient satisfaction, and change in body image. Photographs were shown to a surgical oncologist, a general surgeon, and a plastic surgeon for a physician aesthetic score. RESULTS: Thirteen of 46 patients (28.3%) were dissatisfied with their cosmetic result. Women who were dissatisfied with their cosmetic result were more likely to have a negative change in their body image when compared with patients who were satisfied with their cosmetic result (46.2 % vs 6.1%, P = .02). Additionally, dissatisfied patients were more likely to rate their cosmetic result as poor (15.4 % vs 0%, P = .007) and were more likely to consider reconstruction (46.2% vs 9.1%, P = .01) when compared with satisfied patients. Risk factors to predict dissatisfaction in our patient population included age younger than 52 years and the resection of tumor from the upper inner quadrant. CONCLUSIONS: Twenty-eight percent of patients in this study were dissatisfied with their cosmetic result. Furthermore, a large portion of these patients would consider reconstruction if it were offered. Although this study only identified a few broad risk factors for suboptimal cosmetic outcome, it confirms our hypothesis that many patients who have undergone breast conservation therapy should be referred for plastic surgery consultation.

Cardiopulmonary effects of continuous negative pressure wound therapy in swine.

BACKGROUND: Negative pressure wound therapy (NPWT) has been used for complex sternotomy wounds. Some reports describe foam placement below the posterior sternal table. We compared the hemodynamic and pulmonary effects of foam location during NPWT after median sternotomy. METHODS: Swine were randomized into four groups (n = 6 per group). A polyurethane open cell foam dressing was placed either within or below the sternal table. In one-half, a silicone mesh barrier was placed between the heart and the foam. The NPWT was applied at -125 mm Hg and then released to ambient pressure. This cycle was repeated two more times, and the foam was removed. Heart rate, mean arterial pressure, cardiac output, mixed venous oxygenation, central venous pressure, and pulmonary artery wedge pressure were measured. Peak inspiratory pressure, mean airway pressure, work of breathing, and intrathoracic pressure measurements were recorded. RESULTS: Intersternal placement of foam did not affect hemodynamic parameters. Substernal placement resulted in depression of hemodynamic variables which improved when negative pressure was applied. Pulmonary mechanics were not affected by foam location. CONCLUSIONS: Initial placement of the foam dressing below the posterior sternal table caused reversible depression of cardiac function which appears to be consistent with direct cardiac compression. NPWT therapy had no clinically significant impact on pulmonary parameters. The use of a protective barrier does not alter hemodynamic or pulmonary parameters but continues to be recommended when NPWT is used for sternotomy wounds.

Selective cerebral perfusion: real-time evidence of brain oxygen and energy metabolism preservation.

BACKGROUND: Deep hypothermic circulatory arrest (DHCA) is commonly used for complex cardiac operations in children, often with selective cerebral perfusion (SCP). Little data exist concerning the real-time effects of DHCA with or without SCP on cerebral metabolism. Our objective was to better define these effects, focusing on brain oxygenation and energy metabolism. METHODS: Piglets undergoing cardiopulmonary bypass were assigned to either 60 minutes of DHCA at 18 degrees C (n = 9) or DHCA with SCP at 18 degrees C (n = 8), using pH-stat management. SCP was administered at 10 mL/kg/min. A cerebral microdialysis catheter was implanted into the cortex for monitoring of cellular ischemia and energy stores. Cerebral oxygen tension and intracranial pressure also were monitored. After DHCA with or without SCP, animals were recovered for 4 hours off cardiopulmonary bypass. RESULTS: With SCP, brain oxygen tension was preserved in contrast to DHCA alone (p < 0.01). Deep hypothermic circulatory arrest was associated with marked elevations of lactate (p < 0.01), glycerol (p < 0.01), and the lactate to pyruvate ratio (p < 0.001), as well as profound depletion of the energy substrates glucose (p < 0.001) and pyruvate (p < 0.001). These changes persisted well into recovery. With SCP, no significant cerebral microdialysis changes were observed. A strong correlation was demonstrated between cerebral oxygen levels and cerebral microdialysis markers (p < 0.001). CONCLUSIONS: Selective cerebral perfusion preserves cerebral oxygenation and attenuates derangements in cerebral metabolism associated with DHCA. Cerebral microdialysis provides real-time metabolic feedback that correlates with changes in brain tissue oxygenation. This model enables further study and refinement of strategies aiming to limit brain injury in children requiring complex cardiac operations.

Screening cervical spine MRI after normal cervical spine CT scans in patients in whom cervical spine injury cannot be excluded by physical examination.

BACKGROUND: Cervical spine injuries can occur in as many as 10% of patients with blunt trauma with mental status changes from closed head injuries. Despite normal results on cervical spine computed tomography (CT), magnetic resonance imaging (MRI) is often recommended to exclude ligamentous or soft tissue injury. METHODS: A retrospective review was conducted of trauma patients admitted to a level I trauma center from 2002 to 2006, in whom cervical spine injuries could not be excluded by physical examination. All patients with normal results on cervical spine CT followed by cervical spine MRI were included in the analysis. RESULTS: One hundred twenty patients underwent MRI to examine their cervical spines. Seven patients had abnormal MRI findings suggestive of acute traumatic injury. No MRI studies led to operative intervention. Screening MRI increased from 1% of comatose patients in 2002 to 18% in 2006. CONCLUSIONS: The use of MRI in patients with normal results on cervical spine CT does not appear to alter treatment.

Laparoscopic appendectomy is superior to open appendectomy in obese patients.

BACKGROUND: There are minimal data comparing laparoscopic appendectomy (LA) with open appendectomy (OA) in obese patients. METHODS: We reviewed consecutive adult patients from 2003 to 2005 who underwent an appendectomy at a University-affiliated teaching hospital. Obesity was defined as a body mass index of 30 or greater. Outcome measures included length of stay, surgical times, intra-abdominal abscesses, wound infections, and hospital charges. RESULTS: There were 116 patients with a mean body mass index of 35. Eighty-five patients underwent LA, 12 were converted to open, 4 of 12 (31%) were perforated. Thirty-one patients underwent OA. Overall, 21 (18%) were perforated. Length of stay for LA was better, 3.4 days versus 5.5 days for OA (P = .02), and wound closure rate was better, 90% for LA versus 68% for OA (P < .01). Other outcome measures were equivalent. CONCLUSIONS: LA is associated with shorter lengths of stay, fewer open wounds, and equivalent hospital charges and intra-abdominal abscess rates; and should be considered the procedure of choice for obese patients with appendicitis.