Blood vessel matrix: a new alternative for abdominal wall reconstruction.

BACKGROUND: Biologic matrices offer a new approach to the management of abdominal wall defects when the use of other foreign material is not ideal. A member of our team (GEA) developed a biological decellularized matrix generated from harvested blood vessels of swine blood vessel matrix (BVMx). The aim of our study was to investigate whether this novel collagen-based biological matrix is safe and effective for the repair of abdominal wall hernia defects in a rat model. METHODS: Full thickness abdominal wall defects were created in rats and repaired with our BVMx. After implantation as an underlay for 30 and 90 days, animals were sacrificed and the implanted material evaluated for herniation, adhesions, breaking strength, inflammation, and revascularization. RESULTS: No evidence of herniation was noted at 30 (n = 7) or 90 (n = 7) days after repair. Adhesions, if present, were filmy and easily separated. The mean area of visceral adhesions to the BVMx was 18.9 +/- 11.0% at 30 days and 7.1 +/- 3.1% at 90 days post implantation (P = 0.33). The breaking strength of the BVMx-fascial interface was 4.5 +/- 0.8 N at 30 days and 4.5 +/- 2.4 N at 90 days post implantation (P = 0.98). Histologic analysis demonstrated that the BVMx elicited a mild transient inflammatory response and supported fibroblast migration, deposition of newly formed collagen, and neovascularization. CONCLUSIONS: These data confirm that this BVMx supports vascular ingrowth and provides adequate strength for the repair of abdominal wall defects. Future studies in a large animal model are required to assess its validity for human application.

Functional small-diameter neovessels created using endothelial progenitor cells expanded ex vivo.

Arterial conduits are increasingly preferred for surgical bypass because of inherent functional properties conferred by arterial endothelial cells, especially nitric oxide production in response to physiologic stimuli. Here we tested whether endothelial progenitor cells (EPCs) can replace arterial endothelial cells and promote patency in tissue-engineered small-diameter blood vessels (4 mm). We isolated EPCs from peripheral blood of sheep, expanded them ex vivo and then seeded them on decellularized porcine iliac vessels. EPC-seeded grafts remained patent for 130 days as a carotid interposition graft in sheep, whereas non-seeded grafts occluded within 15 days. The EPC-explanted grafts exhibited contractile activity and nitric-oxide-mediated vascular relaxation that were similar to native carotid arteries. These results indicate that EPCs can function similarly to arterial endothelial cells and thereby confer longer vascular-graft survival. Due to their unique properties, EPCs might have other general applications for tissue-engineered structures and in treating vascular diseases.

Tissue engineered stents created from chondrocytes.

PURPOSE: Trauma, operations or instrumentation of the urethra or ureter may lead to stricture disease. The use of a natural urethral stent made of autologous tissue would be advantageous due to its biocompatibility. In this study we investigated the feasibility of engineering cartilage stents in vitro and in vivo. MATERIALS AND METHODS: We fabricated 40 cylinders 10 mm. long with an inner and outer diameter of 5 and 9 mm., respectively, from polyglycolic acid mesh coated with 50:50 polylactic-co-glycolic acid. Chondrocytes isolated from bovine shoulders were seeded onto the tubular polymer scaffolds at a seeding density of 60 x 106 cells per ml. Scanning electron microscopy was performed to determine the even distribution of chondrocytes throughout the polymer scaffolds. We implanted 20 cylinders under the skin of nude mice and 20 were cultured in stirred bio-reactors. Cytological characteristics, collagen content and mechanical durability were evaluated 4 and 10 weeks after cell seeding. RESULTS: Gross examination of the engineered stents showed the solid, glistening appearance of cartilaginous tissue. Cytological analyses with hematoxylin and eosin, trichrome, alcian blue and safranin O confirmed cartilage, and the deposition of collagen and glycosaminoglycan in each group. Increased deposition of collagen and glycosaminoglycan was observed in the stents created in vivo. Biomechanical testing demonstrated that the cartilaginous cylinders in each group were readily elastic and withstood high degrees of pressure. CONCLUSIONS: This study demonstrates the feasibility of creating cartilaginous stents in vitro and in vivo using chondrocyte seeded polymer matrices. This technology may be useful clinically for stricture disease in the genitourinary tract.

Renal therapy using tissue-engineered constructs and gene delivery.

Currently available renal replacement therapies are not optimal for most patients. In addition to the inherent shortage of transplant organs, significant complications are associated with renal transplantation and immunosuppressive therapy. Dialysis neglects the resorptive, homeostatic, metabolic, and endocrinologic functions of the kidney and only partially replaces its filtration properties, resulting in morbidity and mortality. Application of tissue-engineering techniques may improve many aspects of renal function replacement. Identification of the growth factors capable of directing tissue development and of the technique to be used for their delivery would aid in the engineering of human tissue. The combination of tissue-engineering strategies with gene therapy might allow the transfection of diseased tissues with designated cDNA to eliminate inherent or acquired defects. Devices that have been targeted at replacing a single aspect of renal function, in addition to three-dimensional renal units that are capable of excreting urine-like solutes, have been used experimentally. Combination of these strategies may allow the formation of tissue-engineered kidneys in the future.

Use of N-butyl-2-cyanoacrylate in elective surgical incisions--longterm outcomes.

BACKGROUND: Histoacryl Blue (N-butyl-2-cyanoacrylate) is a tissue adhesive that has been used clinically for more than 20 years. In the last decade, N-butyl-2-cyanoacrylate has been used for cutaneous closure of low-tension lacerations in children and adults and has become a preferred method for closure of pediatric facial lacerations in many emergency rooms outside the United States. Many pediatric elective surgical procedures are performed in tension-free areas and may be suitable for closure with a tissue adhesive. In order to assess this approach, a retrospective study was conducted to evaluate the cosmetic outcomes and complications of the application of N-butyl-2-cyanoacrylate for the approximation of elective surgical incisions in a pediatric population. STUDY DESIGN: Records of 1,098 patients, ages 1 month to 16 years, who, between January 1995 and December 1996, underwent one of the following: orchidopexy, inguinal hernia, umbilical hernia, or hydrocele repair were analyzed. In all patients, N-butyl-2-cyanoacrylate was applied to close the surgical incision. A 12-item questionnaire was created to assess the presence of complications and to determine shortterm and longterm cosmetic outcomes of the incision. Data were collected by conducting telephone interviews of family members. RESULTS: Among the 1,033 children who were treated, 66% had inguinal hernias, 15% hydroceles, 15% undescended testis, and 4% umbilical hernias. Redness or tenderness at the incision site (5.5%), discharge from the surgical wound (1.9%), and wound dehiscence (1.1%) were the main immediate complications after surgery. Overall satisfaction with the cosmetic outcomes of the surgical scar was high, with an average score of 4.73 out of 5 (94.6%). CONCLUSIONS: Our results demonstrate that administration of N-butyl-2-cyanoacrylate for the closure of small low-tension surgical incisions in the pediatric population is safe, has a low complication rate, and produces excellent cosmetic outcomes.

Current and future modalities for functional renal replacement.

Approximately 310,000 Americans suffer from end-stage renal disease, with more than 70,000 new cases reported each year. Advances in immunosuppressive therapy for transplanted patients, in addition to the refined care of patients who are dependent on dialysis, have led to an improved survival for patients with renal failure. Structural, molecular, and pharmacologic developments continue to enhance the efficacy and safety of dialysis in the future. In addition, progressive improvements in the past 2 decades in organ transplantation, a greater insight into the immunobiology of graft rejection, and better surgical and medical management have resulted in improved outcomes. Although renal xenotransplantation is still in its early stages of development, additional research is leading this technology forward. Recent successes in harvesting and expanding renal cells in vitro and the development of biologically active synthetic materials allow for the creation of three-dimensional functioning renal units, which, in the future, may be applied ex vivo or in vivo for partial or full replacement of kidney function.

Increasing examiner involvement in an objective structured clinical examination by integrating a structured oral examination.

INTRODUCTION: The role of physician examiners in an objective structured clinical examination (OSCE) is relatively passive. In our institution examiners criticized the passive nature of their role. This study evaluates the reliability and viability of adding a structured oral examination to an OSCE. METHOD: Ten 24-minute stations consisted of three parts. Part I: 12 minutes-patient encounter. Part II: 6 minutes-oral presentation covering findings, differential diagnosis, and management plan. Part III: 6 minutes-structural oral examination (SOE), containing 5 predetermined questions. RESULTS: Over 6 consecutive days, 72 graduates were assessed. Overall average score: 72.02 (SD 5.05); reliability 0.84. Part I of the OSCE average score: 69.2 (SD 7.4); reliability 0.69. Part II oral presentation average score 64 (SD 5.8) reliability 0.87. SOE average score 77.7 (SD 6.3); reliability 0.64. Eighty-nine percent of the examiners indicated satisfaction with the new format. CONCLUSIONS: The SOE was a reliable component of an OSCE and contributed to the overall reliability. Examiners reported a higher degree of satisfaction with the examination.

Using a video conference to teach clinical clerks in a one-week cardiothoracic clerkship.

BACKGROUND: Students report that their operating room experience during specialty clerkships has been less than satisfactory. To deal with this and other problems in a 1-week cardiothoracic clerkship, a video conference system was introduced. METHODS: Three teaching strategies were used: a seminar dealing with the disease process and a description of the operative procedure; bedside pre-operative assessment of the patient, with a tutor; and a live video conference of the operation. The tutor observed the live video presentation with the students, initiating interaction with the operating surgeon and facilitating questions and discussion. Video quality was maintained by one camera connected to the headlight of the surgeon and another placed above the operative field. RESULTS: Both students and staff expressed a high degree of satisfaction in debriefing sessions and on a standard faculty evaluation form. CONCLUSIONS: This innovation in surgery specialty teaching contributes to the acquisition of educational objectives in the operating room and in a cardiothoracic clerkship.

Variability in the clinical skills of residents entering training programs in surgery.

BACKGROUND: Residents may have significant differences in clinical skills at the start of their surgical training. The purpose of this study was to investigate the variability in these skills by using an objective structured clinical examination. METHODS: A needs assessment was performed, and an objective structured clinical examination composed of 10, two-part stations was developed. Standardized patients (SPs) were trained, validated, and used as both simulated patients and evaluators to assess history taking, physical examination, and interpersonal skills of 10 first-year surgical residents. Structured patient notes (PNs) written by residents after the SP encounters were used to assess history and physical examination documentation skills. Data from one station were not used because more than 25% of the SP ratings were missing. RESULTS: The alpha-reliability was 0.78 for SP ratings, 0.91 for PN scores, and 0.91 for the combined scores. ANOVA revealed significant variation in individual residents' clinical skills as assessed by SPs (F = 4.56, p < 0.01), PNs (F = 11.09, p < 0.001), or both (F = 10.9, p < 0.001). Paired t tests showed that residents scored significantly higher on history taking than on physical examination and attained significantly lower scores on documentation as compared with performance of both history and physical examination (p < 0.001 for each comparison). CONCLUSIONS: The results showed significant variability in clinical skills of the group of residents and yielded detailed information on the performance of each resident. The data were shared with individual residents and are being used to make changes in the educational activities of the program.

Assessment of emergency medicine: a comparison of an experimental objective structured clinical examination with a practical examination.

An emergency medicine and trauma programme was implemented at Ben Gurion University Medical School in Israel. Clinical performance assessment of the first-year course in emergency medicine and trauma was done using a practical examination (PE). In the continuous process of critically reviewing the course objectives and assessment methods the objective structured clinical examination (OSCE) was chosen, for the first time in our medical school, as a tool for course development as well as evaluation of the existing PE. Seven experimental OSCE stations were designed which covered some of the course and practical examination topics. Twenty-six first-year medical students have taken both examinations concurrently. Twenty-three students answered an attitude questionnaire regarding both examinations. Results have indicated that the OSCE provided additional and crucial information on students' deficiencies in clinical performance which were not available from the PE. Those differences were probably due to realistic OSCE station content, highly simulated set-ups, and the objectivity of the examiner, all of which have contributed to a more challenging examination, as compared to the PE. The OSCE in emergency medicine and trauma seemed to have a relatively high level of acceptance by both staff and students. In our opinion it seems that the OSCE is a better tool for first-year level final assessment in emergency medicine and trauma. is a better tool for first-year level final assessment