Concomitant chemoradiotherapy versus induction chemotherapy followed by chemoradiotherapy as definitive, first line treatment of squamous cell carcinoma of the head and neck. A retrospective single center analysis.

PURPOSE: Despite the lack of evidence to support its implementation in the clinical practice, induction chemotherapy (IC) before chemoradiotherapy (CRT) is often used in patients with locally advanced squamous cell carcinoma of the head and neck (SCCHN). We retrospectively examined the tolerability, feasibility, and clinical outcome of both concepts in a single center analysis. PATIENTS AND METHODS: In all, 83 patients were treated between 2007 and 2010 with IC + CRT (n = 42) or CRT alone (n = 41). IC consisted of docetaxel, cisplatin and 5-fluorouracil (TPF), or cisplatin and 5-fluorouracil (PF). All patients were scheduled to receive 2 cycles of PF during concurrent CRT. Adverse events were assessed according to the common toxicity criteria of adverse events (CTCAE v. 3.0). Associations were tested using the χ² test, and survival estimates were calculated according to Kaplan-Meier. RESULTS: The median follow-up was 30.35 months (range 2.66-61.25 months). At 2 years, the overall survival rate was significantly higher for primary CRT compared to IC + CRT group (74.8 % vs. 54 %, respectively; p = 0.041). Significantly more treatment-related overall grade 4 toxicities were documented in the IC + CRT group compared to the CRT group (42.9% vs. 9.8%; p = 0.001). Renal toxicity ≥ grade 2 occurred in 52.4 % vs. 7.3 % (p < 0.001), respectively. In all, 93 % of the patients with primary CRT compared to 71 % with IC + CRT received the planned full radiotherapy dose (p = 0.012). CONCLUSION: This is, to our knowledge, the largest retrospective study to compare IC + CRT with primary CRT. IC showed high acute toxicity, compromised the feasibility of concurrent CRT, and was associated with reduced overall survival rates compared to primary CRT. The lack of clinical benefit in conjunction with the increased toxicity does not support implementation of IC.

Influence of the elasticity module of synthetic and natural polymeric tissue substitutes on the mobility of the diaphragm and healing process in a rabbit model.

Mesh implants are frequently used in congenital diaphragmatic hernia. This experimental study aimed to examine the influence of different materials on the diaphragmatic movement over time as well as their mechanical qualities after 4 months. Ultrapro®, Surgisis®, and Proceed® were implanted onto a diaphragmatic defect in growing rabbits. Diaphragmatic mobility was determined at three time points. At 4 months, defect shrinkage and mechanical properties were measured. The break strength decreased for Ultrapro® and Surgisis®, but did not change relevantly for Proceed®. Ultrapro® (32.46 N/cm) and Proceed® (31.75 N/cm) showed a four-fold higher resistance to tearing than Surgisis® (8.31 N/cm). The elasticity of Ultrapro® showed no significant difference compared to Surgisis® (p = 0.75). Proceed®, on the other hand, was more than twice as elastic as Ultrapro® or Surgisis® (p = 0.015). Ultrapro® had a higher spring rate (6.48 N/mm) compared to Surgisis® (3.82 N/mm) or Proceed® (5.23 N/mm). Observing the standardized movement rates of the diaphragm for each mesh group over time the only statistical differences were seen for the Proceed® group. On account of its material qualities Ultrapro® was found to be the most suitable mesh material for demanding locations in our model.

Is biocompatibility affected by constant shear stress?--comparison of three commercially available meshes in a rabbit model.

Mesh implants as standard treatment for tissue defects can be adapted to patient's needs by specific bioactive coatings. The biophysical interaction with the surrounding tissue must be understood to describe the influence of coatings qualitatively and quantitatively. This study investigates the use of meshes to repair diaphragmatic defects. The physical stress in this tissue is high in comparison to other applications. Therefore, knowledge gained from this experimental model can be applied to other locations. Meshes were implanted on surgically created diaphragmatic defects in growing rabbits. A standardized load model was used to investigate 33 rabbits. The commercial products Ultrapro®, Surgisis®, and Proceed® were implanted. The adhesive properties of the meshes as well as the defect size were determined macroscopically at explantation after 4 months. Sections of the explanted meshes and diaphragms were examined histologically and immunohistochemically. The median defect size for all mesh groups decreased from the initial size of 10 mm down to 4.5 mm at explantation. No statistically significant differences were seen between the three mesh groups. Surgisis® was found to be completely disintegrated after 4 months. Ultrapro® and Proceed® showed no macroscopic differences compared to their original appearance. Both sealed the original diaphragmatic defect as tightly as at time of implantation. Histological and immunohistochemical analyses showed significant differences between the three mesh groups. Proceed® caused stronger inflammatory reaction in the surrounding tissue and inferior connective tissue formation. Regarding the composition of the newly generated tissue within the defect area, Ultrapro® and Surgisis® were found superior. This can sufficiently be explained by the different gradient of inflammatory reaction in the surrounding tissue. Because Surgisis® offers no sufficiently lasting support for the diaphragmatic defect, our future main focus for mesh modification is laid on Ultrapro®.

Large-pore PDS mesh compared to small-pore PG mesh.

BACKGROUND: Currently, absorbable meshes are used as temporary closure in case of laparostoma. Unfortunately the multifilament polyglycolic acid (PG) meshes with small pores reveal little elasticity acting rather as a fluid barrier than permitting drainage of intra-abdominal fluids. Therefore, a new mesh was constructed of absorbable polydioxanon monofilaments (PDS) with increased porosity and longer degradation time. MATERIAL AND METHODS: For evaluation of the tissue response the new PDS mesh was implanted as abdominal wall replacement in each five rats for 7, 21, or 90 days, respectively, and compared to a PG mesh. Histological analysis included HE staining with measurement of the size of the granuloma and immunoshistochemistry for TUNEL, Ki67, TNF-R2, MMP-2, YB1, FVIII, gas6, AXL. Parameters for neovascularization and nerve ingrowth were analyzed. RESULTS: The inflammatory and fibrotic tissue reaction is attenuated with PDS in comparison to PG, e.g., the size of the granuloma was smaller with less cell turnover, and less remodeling as represented by, e.g., reduction of apoptosis, expression of MMP-2, or TNF-R2. The number of ingrowing nerves and vessels explored via AXL, gas6, and factor VIII was increased in the PDS mesh. CONCLUSION: The results from the present investigation showed that a mesh can be constructed of monofilament PDS that induce significant less inflammatory and fibrotic reaction, however permits fluid drainage and preserves elasticity.

Influence of mesh materials on the integrity of the vas deferens following Lichtenstein hernioplasty: an experimental model.

BACKGROUND: The utilization of mesh reinforcement of the inguinal area with polypropylene mesh has increased drastically over the last decade. Infertility due to obstructive azoospermia is a rare but serious complication following inguinal hernia repair, especially in young patients. The aim of this study was to evaluate the effect of different mesh structures on integrity of the vas deferens. MATERIALS AND METHODS: Twenty male Chinchilla rabbits were used. The spermatic cord was dissected free and a Lichtenstein repair was performed with a low-weight polypropylene mesh (UltraPro) and a heavy-weight polypropylene mesh (Prolene) on the contralateral side. A vasography was performed after six months in order to investigate obstructions of the vas deferens. Light microscopy of the mesh host tissue interface was also performed and the foreign body reaction analyzed. Spermatogenesis was evaluated using the Johnsen score. RESULTS: Vasography revealed relevant obstructions (>75% of lumen diameter) located at the mesh margins (50% of Prolene and 22.2% of UltraPro mesh samples). Microscopic investigation of the mesh-host tissue interface showed typical formation of foreign body granulomas. The diameters of the foreign body granulomas were significantly reduced in the UltraPro mesh group (41.7 +/- 5.5 microm) compared to the Prolene mesh group (48.7 +/- 7.7 microm). Upon investigating the percentages of apoptotic (TUNEL) and proliferating (Ki67) cells, no significant differences were found. Following Prolene mesh implantation, a mean Johnsen score of 9.1 +/- 1.2 was estimated, which was not significantly different from the UltraPro mesh samples (8.9 +/- 1.4, P > 0.05). CONCLUSIONS: If a mesh material is needed for inguinal hernia repair in young patients, the use of modern low-weight large porous and elastic samples appears to have a beneficial effect on integrity of the vas deferens.

Mesh migration into the esophageal wall after mesh hiatoplasty: comparison of two alloplastic materials.

BACKGROUND: Hiatal mesh implantation in the operative treatment of gastroesophageal reflux disease has become an increasing therapy option. Besides clinical results little is known about histological changes in the esophageal wall. METHODS: Two different meshes [polypropylene (PP), Prolene; polypropylene-polyglecaprone 25 composite (PP-PG), Ultrapro] were placed on the diaphragm circular the esophagus of 20 female rabbits. After three months a swallow with iodine water-soluble contrast medium for functional analysis was performed. After the animals were sacrificed, histopathological evaluation of the foreign-body reaction, the localization of the mesh relating to the esophageal wall was analyzed. RESULTS: Sixteen rabbits survived the complete observation period of three months. After three months distinctive mesh shrinkage was observed in all animals and meshes had lost up to 50% of their original size before implantation. We found a delayed passage of the fluid into the stomach in all operated animals. There was a significant increased diameter of the outer ring of granulomas in the PP group (76.5 +/- 8.0) compared to the PP-PG group (64 +/- 8.5; p = 0.002). However, we found a mesh migration into the esophageal wall in six out of seven animals (PP) and five out of nine animals (PP-PG), respectively. CONCLUSION: Experimental data suggest that more knowledge is necessary to assess the optimal size, structure, and position of prosthetic materials for mesh hiatoplasty. The indication for mesh implantation in the hiatal region should be carried out very carefully.

Modification of collagen formation using supplemented mesh materials.

BACKGROUND: Formation of recurrent inguinal and incisional hernia shows an underlying defect in the wound healing process. Even following mesh repair an altered collagen formation and insufficient mesh integration has been found as main reason for recurrences. Therefore the development of bioactive mesh materials to achieve a local modification of the scar formation to improve patients outcome is advisable. METHODS: Thirty-six male Wistar rats were used within this study. A Mersilene (R) mesh sample was implanted after midline skin incision and subcutaneous preparation. Before implantation mesh samples were incubated for 30 minutes with either one of the following agents: doxycycline, TGF-beta 3, zinc-hydrogeneaspartate, ascorbic acid, hyaluronic acid. Incubation with a physiologic 0.9 % NaCl solution served as control. Seven and 90 days after mesh implantation 3 animals from each group (n = 6) were sacrificed for morphological observations. Collagen quantity and quality was analyzed measuring the collagen/protein as well as the collagen type I/III ratio. RESULTS: Following an implantation interval of 90 days supplementation with doxycycline (39.3 +/- 7.0 microg/mg) and hyaluronic acid (34.4 +/- 5.8 microg/mg) were found to have a significantly increased collagen/protein ratio compared to implantation of the pure Mersilene (R) mesh samples (28.3 +/- 1.9 microg/mg). Furthermore, an overall increase of the collagen type I/III ratio was found in all groups indicating scar maturation over time. However, no significant differences were found after 7 and 90 days of implantation comparing collagen type I/III ratio of supplemented mesh samples and control group. CONCLUSIONS: In summary, we found an influence of supplemented mesh materials on collagen deposition. However, the investigated bioactive agents with reported influence on wound healing were not associated with an improved quality in scar formation.

Is there a risk of infertility after inguinal mesh repair? Experimental studies in the pig and the rabbit.

The implantation of a non-absorbable polypropylene mesh during hernia repair causes chronic foreign body reaction involving the surrounding tissue. In case of inguinal hernia repair using mesh techniques, the spermatic cord is potentially affected by this chronic inflammatory tissue remodeling. This effect has been investigated using standardized animal models (pig and rabbit). Fifteen adult male pigs underwent transinguinal preperitoneal implantation of a polypropylene mesh. The contralateral side with a Shouldice repair served as control. After 7, 14, 21, 28, and 35 days, three animals were sacrificed. The spermatic cords were resected and analyzed histologically. In a second experiment Lichtenstein repair using the same polypropylene mesh and Shouldice repair on the contralateral side was done in eight chinchilla rabbits. Three animals served as controls. Three months after operation, the analysis included testicular size, testicular temperature, and testicular and spermatic cord perfusion. We added histological evaluation of the foreign body reaction and the spermatogenesis using the Johnsen score. In the pig, we observed a certain foreign body reaction with diffuse infiltrating inflammatory cells after mesh implantation. Venous thrombosis of the spermatic veins occurred in five of 15 cases. One animal presented focal fibrinoid necrosis of the deferent duct wall. The side of Shouldice repair showed only minor postoperative changes. In the rabbit, we also observed a typical foreign body reaction at the interface between mesh and surrounding tissue, which was not detectable after Shouldice repair. The mesh repair led to a decrease of arterial perfusion, testicular temperature, and the rate of seminiferus tubules with regular spermatogenesis classified as Johnsen 10 (Lichtenstein: 48.1%, Shouldice: 63.8%, controls: 65.8%). Testicular volume increased about 10% after each operation. The implantation of a polypropylene mesh in the inguinal region induces major response of the structures of the spermatic cord. This may have an influence also on spermatogenesis. Due to this a strict indication for implantation of a prosthetic mesh during inguinal hernia repair is recommended.

The influence of inguinal mesh repair on the spermatic cord: a pilot study in the rabbit.

The permanent implantation of a polypropylene mesh during inguinal hernia repair causes chronic inflammatory changes in the surrounding tissue. We investigated the effect of this foreign body reaction on the structures of the spermatic cord in the rabbit. Eight Chinchilla rabbits underwent unilateral inguinal hernia repair by the Lichtenstein technique using Marlex (n = 4) or Ultrapro (n = 4) mesh. The contralateral side was operated upon using the Shouldice repair. Three animals served as controls. Three months after operation we analyzed testicular size, testicular temperature, and arterial perfusion by excitation light of a 780-nm laser after injection of 0.5 mg/kg indocyanin green. Histological evaluation included spermatogenesis (Johnsen score) and foreign-body reaction. Testicular volume increased about 10% after each operation. The decrease of arterial perfusion and testicular temperature was more significant after mesh repair than following Shouldice operation. After mesh implantation we found fewer seminiferous tubules classified as Johnsen 10 (Marlex: 51.3%, Ultrapro: 45.0%) than after Shouldice repair (63.8%) or in the controls (65.8%). The spermatic cord showed a typical foreign-body reaction at the interface between mesh and surrounding tissue, which was not detectable after Shouldice repair. Preserved cremasteric muscle fibers protected the structures of the spermatic cord. The inflammatory foreign-body reaction of the surrounding tissue induced by the inguinal prosthetic mesh includes the structures of the spermatic cord. This may have an influence also on spermatogenesis. Therefore, we recommend strict indications for implantation of a prosthetic mesh during inguinal hernia repair.

PVDF as a new polymer for the construction of surgical meshes.

Abdominal hernia repair is the most frequently performed operation in surgery. Mostly due to lowered recurrence rates mesh repairs in hernia surgery have become an integral component despite increasing mesh-related complications. Current available mesh prosthesis are made of polypropylene (PP). polyethylene-terephtalat or polytetrafluorethylene. though all of them reveal some disadvantages. The introduction of new materials seems to be advisable. Caused by supposed advantageous textile properties and tissue response two mesh modifications made of polyvinylidene fluoride (PVDF) for abdominal hernia repair were developed. In the present study the PVDF meshes were compared to a common heavy weight PP-mesh (Prolene) in regard to functional consequences and morphological tissue response. After implantation in rats as inlay for 3, 14, 21, 42 and 90 days abdominal wall mobility was recorded by three-dimensional photogrammetry. Tensile strength of the suture zone and the mesh itself were determined. Explanted tissue samples have been investigated for their histological reaction in regard to the inflammatory infiltrate. vascularisation, connective and fat tissue ingrowth. Number of granulocytes, macrophages, fibroblasts, lymphocytes and foreign giant body cells have been evaluated to reflect quality of tissue response. The cellular response was grasped by measurement of DNA strand breaks and apoptosis (TUNEL), proliferation (Ki67) and cell stress (HSP70). Analyzing the results confirmed that construction of hernia meshes made of PVDF could be an advantageous alternative to the commonly used materials due to an improved biostability. lowered bending stiffness and a minimum tissue response.

Shorter postoperative atony after laparoscopic-assisted colonic resection? An animal study.

BACKGROUND: The duration of the postoperative ileus after laparoscopic surgery remains a controversial topic. The aim of our study was to compare the restoration of intestinal motility after laparoscopically assisted and conventional resection of the distal colon in a canine model. METHODS: Two weeks after the implantation of three electrodes on the jejunum, the distal colon was resected in a laparoscopic-assisted or conventional procedure in two groups of four dogs each. Gastrointestinal motility was monitored by registration of the electromyograhic activity of the small intestine and by intermittent fluoroscopies of radiopaque markers. RESULTS: Electrical activity in the early postoperative period was characterized by the basic electrical rhythm and the absence of spike activity. The first postoperative activity front of the migrating motility complex (MMC), indicating the restoration of motility, occurred significantly earlier after laparoscopic-assisted resection (4.5 +/- 1 hr) than after conventional resection (31 +/- 10 h). Radiological observations showed a significantly delayed gastric emptying and a prolonged transit of radiopaque markers to the rectum after open surgery. CONCLUSION: These results support the hypothesis that laparoscopic-assisted resection of the colon leads to a shortened postoperative atony in comparison to open surgery.

Comparison of adhesion reformation after laparoscopic and conventional adhesiolysis in an animal model.

This study set out to compare adhesion reformation after conventional and laparoscopic adhesiolysis using two different laparoscopic dissection techniques. In a first operation, 36 rabbits underwent fixation of 6 cm2 of the cecum with the serosa removed to the lateral abdominal wall to induce standardized adhesions. After 4 weeks, adhesiolysis was performed laparoscopically (n = 12) or via laparotomy (n = 12) using sharp and blunt dissection. In a third group (n = 12), laparoscopic adhesiolysis was performed using monopolar electrocautery. Outcome was assessed by incidence, extent, and localization of adhesion reformation. After conventional adhesiolysis, all rabbits developed new adhesions relative to 79% after laparoscopic adhesiolysis. The extent of reformed adhesions (median) was greater after conventional adhesiolysis than laparoscopic adhesiolysis (2725 mm2 vs 230 mm2, P < 0.001). The latter did not differ significantly from laparoscopic adhesiolysis by electrocautery (310 mm2). There were small adhesions to 3 of 72 trocar wounds, but extensive adhesions to 33% of the abdominal incisions were found in the conventional group. In this standardized experimental setting, laparoscopic adhesiolysis is associated with a significantly reduced reformation of adhesions. Different laparoscopic dissection techniques have no significant influence on the extent of adhesion reformation.

New adhesion formation after laparoscopic and conventional adhesiolysis: a comparative study in the rabbit.

This study aimed to compare new adhesion formation after laparoscopic and conventional adhesiolysis. In a first operation, 24 rabbits underwent fixation of deserosated cecum (6 cm2) to the lateral abdominal wall to induce standardized adhesions. After 4 weeks, adhesiolysis was performed by laparoscopy (n = 12) or laparotomy (n = 12). Outcome was assessed by the incidence, extent, and location of adhesion reformation. After conventional adhesiolysis, new adhesions developed in all the rabbits, as compared with 75% after laparoscopic adhesiolysis. The extent of newly formed adhesions was significantly reduced (p < 0.001) after laparoscopic adhesiolysis (368+/-115 mm2) as compared with conventional adhesiolysis (2434+/-245 mm2). There were no adhesions to trocar wounds, but adhesions to the abdominal incision were found in 33% of the conventional group. In a rabbit model comparing laparoscopic and conventional adhesiolysis in a standardized experimental setting, laparoscopic adhesiolysis is associated with a significantly reduced formation of new postoperative adhesions.

Colon interposition for esophageal replacement: isoperistaltic or antiperistaltic? Experimental results.

BACKGROUND: Isoperistaltic colon is preferred to antiperistaltic colon for esophageal replacement, but experimental data do not exist to support this practice. METHODS: In 7 dogs a 20 cm long colon loop was interposed between the skin and the small bowel, isoperistaltically in 3 dogs and antiperistaltically in 4 dogs. Three months later five strain-gauges were implanted and evacuation was investigated by motility testing, barium studies, and scintigraphy. RESULTS: Motility recording showed normal colon motility in the excluded loops. Quiescent states (duration 40.2 +/- 13.6 minutes) were followed by contractile states (duration 7.5 +/- 2.4 minutes, frequency 3.3 +/- 0.6 per minute). The main peristaltic direction of isoperistaltic loops was isoperistaltic, and the main peristaltic direction of antiperistaltic loops was antiperistaltic. Evacuation took place exclusively during the contractile status. Half time emptying was more rapid in isoperistaltic loops (35 +/- 11 vs 69 +/- 16 minutes). The content of antiperistaltic loops was held back by antiperistaltic activity. Application of oatmeal porridge into the loops shortened the quiescent status from 40.2 to 13.2 +/- 4.8 minutes. CONCLUSIONS: The colon graft for esophageal replacement is an active system. Food is stored during the quiescent states and evacuated during the contractile states. The original peristaltic direction is preserved so that retroperistalsis in antiperistaltic loops may lead to patient discomfort and pulmonary complications.

Effect of artificial valves on intestinal adaptation in the short-bowel syndrome: an integrated study of morphological and functional changes in rats.

Two-third-resections of the proximal or distal small bowel with and without artificial valves were performed in rats. Intestinal adaptation led to a significant increase in bowel diameter, villus height and villus diameter and consequently in absorptive mucosal surface area per unit of serosal area. Additional artificial valve construction did not affect the calculated mucosal surface area after proximal resection, while it significantly decreased the absorptive area by the occurrence of large, plump villi after distal resection. There was no change in small-intestinal absorption of water, glucose and electrolytes per unit mucosa with valve construction. DNA cytometry showed that artificial valves led to mucosal hyperplasia without hypertrophy. These morphological changes coincided with a significant increase in basal and stimulated gastrin release. The body weight was unchanged or even worse in the valve groups than after resection alone, despite a significantly prolonged transit time. Therefore, in our study, artificial valves did not result in functional improvements after small intestinal resections.

Electrophysiological and mechanical activity of the upper gastrointestinal tract after duodenoplasty or segmental resection of benign gastric outlet stenosis.

In an animal experimental study we examined the postoperative recovery of the motility of the upper gastrointestinal tract after operative treatment of a benign gastric outlet obstruction. At 45 Days after induction, a duodenal stenosis was resected in six dogs, and resolved by Finney's duodenoplasty in another six dogs. Fourteen days after segmental resection, the gastric emptying was faster [half evacuation time (T1/2) for semisolid food = 44.4 +/- 16.8 min] than following duodenoplasty [T1/2 = 56.8 +/- 25.3). Here motor migrating complexes (MMCs) started in the antrum and could be traced down to the jejunum. After segmental resection we recognized MMC only distal to the anastomosis. The duration of the whole MMC cycle (69.0 +/- 18.6 min) as well as of the single phases was significantly shorter in the resection group than after duodenoplasty (108.0 +/- 15.1 min). At 28 days after operation the differences in the electromyographic findings were smaller (82.0 +/- 15.1 min vs. 111.4 +/- 11.2 min), but still significant. Obviously humoral transmitters and the extrinsic neural system lead to good propagation of the MMC across the anastomosis, even before the intramural pathways are reestablished. Concerning the fast recovery of the motility of the upper gastrointestinal tract, duodenoplasty is superior to segmental duodenal resection.

Influence of suture material and suture technique on collagen fibril diameters in midline laparotomies.

BACKGROUND: Although laparotomy closure is associated with a cumulative 15% failure rate, the effect of different suture techniques and materials on the ultrastructural composition of the healing incision has not been investigated. METHOD: in 40 Wistar rats the collagen fibril diameters and the regenerative tissue were compared using electron microscopy 14 and 28 days after midline laparotomy. Wounds were closed with single and running sutures using either polypropylene or polyglactin 910. RESULTS: Closure with polypropylene led to significantly larger mean fibril diameters than closure with polyglactin. Regardless of time and suture material, running closure resulted in significantly smaller mean collagen fibril diameters than single sutures. Four weeks after laparotomy, inflammatory reactions, disorganization of collagen and irregularities of the vascular architecture were found after closure with absorbable suture material but not after closure with nonabsorbable material. CONCLUSION: Suture material and suture method significantly influence the ultrastructural composition of the healing incision. Persisting mechanical irritation around the suture threads after single sutures and severe persisting inflammatory reactions after the use of absorbable suture material are important influencing factors.

Influence of polyglactin-coating on functional and morphological parameters of polypropylene-mesh modifications for abdominal wall repair.

Regarding oversized mechanical properties of most of the currently available materials a new mesh was developed (ETHICON, Norderstedt, Germany) and exactly adopted to the physiology of the human abdominal wall by reducing the amount of polypropylene (weight of <30 g/m2; mesh A). The consecutive increase of pores size as well as the use of multifilaments led to a pronounced increase of flexibility. To improve the handling during operation the initial stiffness of this low-weight large pores mesh was increased by strengthening with different amounts of absorbable polyglactin (combination of glycolide and lactide) in various forms: by coating (mesh B), adding multifilament polyglactin filaments (mesh C, Vypro) or both (mesh D), respectively. To test the consequences of the different supplementary techniques all mesh variants are implanted in a rat model. Over implantation intervals of 3, 7, 14, 21 and 90 days we measured the tensile strength, the resulting stiffness and surveyed the tissue response, particularly in regard to the extent of inflammation and to the induced fibrosis. The results proved a sufficient mechanical stability of the material reduced and pure polypropylene mesh A without restriction of the mobility of the abdominal wall compared with a group that had simple laparotomy and closure. The histological analysis of the interface showed a minor inflammatory reaction and a dense vascularisation. The addition of polyglactin multifilaments (mesh C) reduces the number of macrophages and granulocytes as indicators for acute inflammation, showing generally a scar formation limited merely to the perifilamentary region. The abdominal wall compliance remained unchanged compared with mesh A. The coating of the polypropylene with polyglactin (mesh B and D) appeared to change the tissue reaction remarkably, favouring the formation of a connective tissue capsule around the whole mesh. The mechanical testing revealed an apparent protrusion with an increase of curvature of the artificial abdominal wall at rising intraabdominal pressures. The entire coating of the polypropylene surface with polyglactin induces an all embedding scar plate, filling out the pores and forming a tissue capsule. The complex interaction of tissue and implanted biomaterials with their distinct alterations of the tissue response confirms the necessity of in vivo experiments even after 'minor' modifications. Whereas the addition of polyglactin filaments appears to be favourable, the coating of polypropylene with polyglactin seems to hinder the incorporation of the mesh.

Experimental studies on small intestinal pouch motility and evacuation.

UNLABELLED: The aim of the study was to investigate pouch motility and evacuation under standardised conditions with a minimum of external influence. METHODS: Ileal J-pouches had been constructed 30 cm proximal to the ileocecal valve in 10 dogs (6 pelvic/4 gastric configuration). After 8 weeks the following examinations were performed: (1) measurement of pouch compliance by balloon distension, (2) measurement of pouch contractions by strain gauge transducers, (3) radiological imaging of pouch contractions and evacuation, (4) evacuation scintigraphy and (5) radiological determination of small intestinal transit time. RESULTS: Compliance (2.3 +/- 1.1 mmHg/ml) and small intestinal transit time (31.6 +/- 7.5 h) were significantly higher in the pouch group than in controls (0.5 +/- 0.2 mmHg/ml, 8.0 +/- 2.8 h; p < 0.05). Scintigraphy and radiography showed delayed pouch evacuation (t(1/2) = 109 +/- 52 min). Strain gauge measurements revealed irregular pouch contractions without detectable propagation. Contraction amplitudes (40.4 +/- 22.9 g) and frequencies (10.4 +/- 1.0/min) were equal all over the pouch. There were no functional differences between gastric and pelvic pouch configuration. CONCLUSION: Small intestinal pouches act as reservoirs. Uncoordinated motility patterns contribute to this function. Other factors than pouch motility are responsible for evacuation.

Laparoscopy versus laparotomy: comparison of adhesion-formation after bowel resection in a canine model.

AIM: The purpose of the study was to compare adhesions following laparoscopic and conventional operations. METHODS: In 14 dogs cecal resection and a deserosation of the abdominal wall were performed laparoscopically (n = 7) or by laparotomy (n = 7). After 8 days all dogs were reexamined and the adhesions were quantified by computer-aided measurements. The significance of any differences were tested using Student's t test. RESULTS: The extent of adhesions after laparoscopy (630 +/- 360 mm2) and after laparotomy (3,300 +/- 1,007 mm2) differed significantly (p < 0.0001). Extensive adhesions to the abdominal incision and interenteric adhesions were found after conventional operations. Identical manipulations, such as cecal resection or deserosation of the lateral wall, led to the same frequency and extent of adhesions in both operation groups. CONCLUSION: Laparoscopic procedures are associated with significantly less adhesions in comparison to conventional operations. Therefore the risk of adhesion-related complications should be reduced after laparoscopic operations.