Oriented polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)) films by Langmuir-Blodgett deposition: a synchrotron X-ray diffraction study.

Langmuir-Blodgett films of polyvinylidene fluoride trifluoroethylene - P(VDF-TrFE)-copolymers possess substantially improved electrocaloric and pyroelectric properties, when compared with conventionally spin-cast films. In order to rationalize this, we prepared single-layered films of P(VDF-TrFE) (70 : 30) using both deposition techniques. Grazing incidence wide-angle X-ray scattering (GIWAXS), reveals that Langmuir-Blodgett deposited films have a higher concentration of the ferroelectric ß-phase crystals, and that these films are highly oriented with respect to the substrate. Based on these observations, we suggest alternative means of deposition, which may substantially enhance the electrocaloric effect in P(VDF-TrFE) films. This development has significant implications for the potential use of P(VDF-TrFE) in solid-state refrigeration.

[Treatment of a pregnant patient after multiple trauma: rare combination with thrombotic thrombocytopenic purpura]. / Versorgung einer schwangeren Patientin nach Polytrauma: Seltene Kombination mit thrombotisch-thrombozytopenischer Purpura.

Multiple trauma during pregnancy is a relatively rare situation which poses a great challenge for the team in charge of treatment. A concomitant disease, such as thrombotic thrombocytopenic purpura (TTP) with thrombocytic coagulopathy increases the complexity of the treatment problems. This article describes the case of a 36-year-old pregnant woman referred to this hospital suffering from multiple trauma with severe liver rupture. Stabilization was achieved after an emergency Caesarean section and packing of the liver. Recurrent massive bleeding from the liver occurred after depacking and was treated successfully with recombinant factor VIIa. The concomitant TTP was treated by transfusion of fresh frozen plasma and corticosteroids. Rapid initiation of therapy was the goal to achieve hemostasis and prevent aggravation of the coagulation disorder and an unfavourable outcome despite severe thrombocytopenia.

Identification of salt responsive genes using comparative microarray analysis in Upland cotton (Gossypium hirsutum L.).

Salinity negatively impacts plant growth and productivity, and little is known about salt responsive genes in cotton. In this study, an intra-specific backcross population of cotton (Gossypium hirsutum L.) was treated with 200 mM NaCl after which differentially expressed genes were identified by comparison between salt tolerant and susceptible segregant bulks using comparative microarray analysis. Microarray analysis identified 720 salt-responsive genes, of which 695 were down-regulated and only 25 were up-regulated in the salt tolerant bulk. Gene ontology of annotated genes revealed that at least some of the identified salt responsive transcripts belong to pathways known to be associated with salt stress including osmolyte and lipid metabolism, cell wall structure, and membrane synthesis. About 48% of all salt-responsive genes were functionally unknown. Quantitative RT-PCR was used to validate 17 selected salt responsive genes. This work represents the first study in employing microarray to investigate the possible mechanisms of the salt response in cotton. Further analysis of salt-responsive genes associated with salt tolerance in cotton will assist in laying a foundation for molecular manipulation in development of new cultivars with improved salt tolerance.

Triple-negative high-risk breast cancer derives particular benefit from dose intensification of adjuvant chemotherapy: results of WSG AM-01 trial.

BACKGROUND: This paper evaluates the prognostic and predictive impact of protein expression of various molecular markers in high-risk breast cancer (HRBC) patients with >9 involved lymph nodes, who received different chemotherapy dose-intensification strategies within a prospective randomized WSG AM-01 trial. MATERIALS AND METHODS: Paraffin-embedded tumors from 236 patients, who were randomly assigned to dose-dense conventional chemotherapy with four cycles of E(90)C(600) followed by three cycles of C(600)M(40)F(600) every 2 weeks (DD) or a rapidly cycled tandem high-dose regimen with two cycles of E(90)C(600) every 2 weeks followed by two cycles of E(90)C(3000)Thiotepa(400) every 3 weeks (HD), were available for retrospective central pathological review (116 HD/120 DD). Expression of estrogen receptor (ER), progesterone receptor (PR), MIB-1, epidermal growth factor receptor, and Her-2/neu was evaluated immunohistochemically using tissue microarrays. Results were correlated with follow-up data and treatment effects by proportional hazard Cox regression models (including interaction analysis). RESULTS: After a median follow-up of 61.7 months, 5-year event-free survival (EFS) as well as overall survival (OS) rates for the 236 patients were significantly better in the HD arm: EFS: 62% versus 41% [hazard ratio (HR) = 0.60, 95% CI 0.43-0.85, P = 0.004]; OS: 76% versus 61% (HR = 0.58, 95% CI 0.39-0.87, P = 0.007). In multivariate analysis, HD, tumor size <3 cm, positive PR, negative MIB-1 staining, and grade 1/2 were associated with favorable outcome. Interaction analysis showed that regarding predictive effects, triple negative (ER/PR/Her-2/neu) and G3 tumors derived most benefit from HD. CONCLUSION: Tandem HD improves both EFS and OS in HRBC. This therapy effect may be partly attributable to superior efficacy in the subgroup of triple-negative tumors and/or G3 with their poor prognostic marker profile.

Complications after transanal endoscopic microsurgical resection correlate with location of rectal neoplasms.

PURPOSE: Transanal endoscopic microsurgery (TEM) is a technique that has found its place in routine practice due to its minimal invasive character and associated low morbidity. The purpose of this study was to assess the influence of anatomical variables of rectal neoplasms as well as surgeon experience on postoperative complications in patients undergoing TEM at a tertiary care center. METHODS: Data from 288 patients undergoing TEM over a 16 year period were entered in a prospective data base. Anatomical data of rectal neoplasms, operative data, and early postoperative outcome were analyzed retrospectively. RESULTS: Overall surgical complications [OR 7.0 (1.5-45,5); p < 0.01] and bleeding [OR 222 (82 - 14316); p < 0.01] correlated with the localization of the neoplasm on the lateral wall of the rectum. Furthermore there was a trend for more surgical overall complications as well as bleeding in neoplasms with a diameter of >2 cm and neoplasms located >8 cm from the anal verge. Complications did not correlate with the number of TEM procedures performed. CONCLUSION: TEM resection of neoplasms located on the lateral rectal wall have a higher risk of bleeding. The learning curve for transanal endoscopic microsurgery appears to be negligible in surgeons with experience in minimal invasive surgery.

[Clinical pathways -- first results of a systematic IT-supported application at a surgical department of a university hospital]. / Klinische Behandlungspfade. Erste Ergebnisse des systematischen IT-gestützten Einsatzes an einer chirurgischen Universitätsklinik.

BACKGROUND AND OBJECTIVE: In analogy to industrial process management, clinical pathways have been introduced for operational process organisation in orthopedic and interventional procedures as well as for conservative treatments. Within this study, introduction and continuous, systematic application of clinical pathways at a surgical department of a university hospital was investigated. METHODS: Analysis was performed by IT-based (SAP/i. s. h.med) evaluation of the registered data regarding pathway violations. Additionally, patients' records were matched with the computerized data for quality assurance of pathway documentation. RESULTS: 501 patients were entered in 16 clinical pathways (31 +/- 39 patients per pathway). The mean period from the introduction of a distinct pathway to the data acquisition of the present study ranged from 2 to 14 months (mean 7+/-7.5 months). Pathway violations correlated with the complexity, but not with the period since the pathway was introduced. Organisational reasons next to medical reasons (i. e. delayed gastric function or wound healing) were the most frequent causes for pathway violations. CONCLUSION: Clinical pathways may not only be realised for operative procedures or conservative treatments, but represent a clinical and administrative management instrument at a surgical department of a university hospital for daily work routine. They are suitable as an instrument for clinical quality and risk management, as an economic control instrument in reorganisation phases as well as in the routine of surgical clinics.

Adjuvant therapy with edrecolomab versus observation in stage II colon cancer: a multicenter randomized phase III study.

BACKGROUND: In a phase III study recruiting patients with stage II colon cancer the effect of adjuvant therapy with edrecolomab, a murine monoclonal antibody to the cell-surface glycoprotein 17-1A, was compared to observation alone. PATIENTS AND METHODS: From January 1997 until July 2000 a total of 377 patients were postoperatively stratified according to tumor stage (T3 vs. T4) and center, and randomly allocated to either treatment with edrecolomab (cohort A, n = 183) or observation (cohort B, n = 194). Patients in cohort A received a total of 900 mg edrecolomab. The study was terminated prematurely because of discontinuation of drug supply in Germany. RESULTS: 305 patients were eligible for the primary endpoint of overall survival and 282 patients for disease-free survival. After a median follow-up of 42 months overall survival and disease-free survival were not significantly different. Toxicity was mild. CONCLUSIONS: In the present study, postoperative adjuvant treatment with edrecolomab in patients with resected stage II colon cancer did not improve overall or disease-free survival.

[Monitoring of plasma disappearance rate of indocyanine green in a patient with necrotizing fasciitis and septic shock]. / Uberwachung der Plasmaeliminationsrate von Indocyaningrün bei einem Patienten mit nekrotisierender Fasziitis und septischem Schock.

HISTORY AND ADMISSION FINDINGS: A 45-year old man with diabetes mellitus and arterial hypertension was transferred with fever of unknown origin, suspected diabetic angiopathy and sepsis. On admission the patient presented all signs of septic shock. Livid coloured injuries on his right hand and petechial bleeding in distal extremities were observed. INVESTIGATIONS: A different origin of sepsis was not found in transesophageal ultrasound cardiography and computed tomography of cranium, chest and abdomen. DIAGNOSIS, TREATMENT AND COURSE: Immediately after admission early goal-directed therapy was initiated. Apart from calculated antibiotic therapy intensive insulin therapy and hydrocortisone substitution was begun. The patient presented a multiple organ dysfunction syndrome. Plasma disappearance rate of indocyanine green (PDR (ICG)) on admission was 20,4 %/min (normal range > 18 %/min) and fell to 6,8 %/min within 12 hours, while central venous oxygen saturation remained normal. Despite therapy according to current guidelines for severe sepsis, the patient deteriorated. Surgical debridement was performed suspecting necrotizing fasciitis and application of recombinant human activated protein C (rhAPC) started. PDR (ICG) rapidly raised to normal values; the patient recovered and was discharged after 9 days. CONCLUSIONS: Monitoring of PDR (ICG) allows for improved bedside evaluation of liver perfusion of the critically ill and is not only able to predict prognosis but may help in decision making for supportive therapies.

[Stomach carcinoma as a surgical emergency]. / Das Magenkarzinom als chirurgischer Notfall.

Perforated or bleeding gastric cancer is a life threatening situation that occurs in less than 10% of all patients with gastric cancer in the Western world. Three quarters of these complicated gastric carcinomas show advanced stages (UICC stages III and IV). Diagnosis is made intraoperatively only in the majority of patients. Emergency gastrectomy is superior to any type of local excision and/or local repair regarding surgical mortality and long-term survival and should be the intervention of choice. Stage-related long term survival of patients with emergency gastrectomy is comparable to that of electively resected patients. Minimalism and nihilism are therefore not appropriate in the treatment of complicated gastric cancer and are often deleterious. Subtotal gastrectomy without D2 lymphadenectomy is regarded as the adeqauate procedure in most cases.

[Laparoscopy-assisted colorectal resections: morbidity, conversions, outcomes of a decade]. / Laparoskopisch assistierte kolorektale Resektionen. Morbidität, Konversionen, Komplikationen--Ergebnisse eines Jahrzehnts.

BACKGROUND: After one decade of laparoscopic resections of the colon and rectum the parameters morbidity, conversion and complications were analyzed. The analysis of the literature comprises the results of operations performed for benign and malignant indications. METHODS: The analysis is based on the medline research of the past ten years. Publications in German language not listed were added. Results of multicenter studies were included if differentiation by indication and dignity could be achieved. Surveys of different operations of the colon and rectum not differentiated by the parameters to be analyzed were excluded. Publications of the early beginning of laparoscopic surgery were included even if not more than 10 cases were presented but the parameters described in detail. RESULTS: ADENOMAS OF THE COLON: The morbidity ranges from 0-17.4%, the conversion rate is 17.4 and 18.4% in 23 respectively 38 patients. SIGMOID DIVERTICULITIS: Mortality 0-1.8%. The morbidity was 16% in the early series and was later below 10% (8.7 and 7.3%). In the beginning the conversion rate was over 10% (12.0-38.9%) with one exception (0%). It dropped below 10% (4.6-9.2%) and was 0% in a recent study of 64 patients. The reasons for conversion are: inflammatory mass, fistula; perforation and obesity. Intraoperative complications are rare. The rate of postoperative complications did not change within 10 years (9.7 to 25.0% against 7.3 to 17.0%). CROHN'S DISEASE: The morbidity is around 10% (10.6-14.0%) and is lower in series with exclusively ileocoecal resections. The conversion rate is low or zero in ileocoecal resections and raises with the degree of inflammation and the spectrum of procedures. COLON CANCER: Mortality: 0-1.9%. The morbidity ranges from 6.8 to 30% and is especially high after conversions (up to 50%). The conversion rate reflects with the range of 4.2 to 21.0% in the beginning and 1.6 to 23.5% later the experience of the individual surgeon. RECTAL CANCER: Even in large series (n = 157) the mortality of laparoscopic rectal resections is zero. The conversion rate is 0-7.6%; the morbidity 11.5 to 26.4%. REVERSAL OF HARTMANN PROCEDURE: The number of cases is low, the conversion rate is around 20%. The morbidity ranges from 14.3-41.1% with one exception (0%). RECTOPEXY: Four different techniques are applied laparoscopically. The morbidity ranges from 0 to 16%. The conversion rate is 0-2.6%, except one (16.0%). CONCLUSION: After one decade of laparoscopic colorectal surgery there are advantages for benign indications (adenomas, Crohn's disease, rectopexy) when compared with open surgery. Disadvantages arise from conversions. Experience of the surgeon is a strong parameter for a successful outcome. Results of ongoing studies are awaited for malignant indications.

Double traumatic abdominal wall hernia and colon laceration due to a pelvic fracture.

A traumatic abdominal wall hernia was observed in association with a colonic laceration due to a pelvic fracture. The presence of this specific combination of injuries is a rare clinical entity. CT evaluation with intravenous and bowel contrast media identified the traumatic abdominal wall hernia and the bowel entrapment.

Granulocyte elastase and systemic cytokine response after laparoscopic-assisted and open resections in Crohn's disease.

PURPOSE: The aim of this study was to assess whether systemic proinflammatory cytokines (IL-6), anti-inflammatory cytokines (IL-4, IL-10), acute phase proteins (C-reactive protein), or granulocyte elastase are valuable indicators for determining the degree of surgical trauma after open vs. laparoscopic-assisted resections in Crohn's disease. METHOD: Eleven patients in each group (open and laparoscopic-assisted surgery) were matched for indication, surgical procedure, and Crohn's disease activity index. Serum IL-4, IL-6, and IL-10 were measured using enzyme-linked immunosorbent assay. Serum C-reactive protein was determined by immunoturbidimetric assay. Plasma granulocyte elastase was determined by immunoactivation immunoassay. Blood was sampled preoperatively, six hours after the operation, and at postoperative Days 1 to 5. RESULTS: IL-4 was not detectable in any sample analyzed. Serum IL-6 and IL-10 levels peaked postoperatively in both groups without significant differences between laparoscopic-assisted (185.6 +/-54.1 pg/ml and 112.1 +/- 19.4 pg/ml, respectively; mean +/-standard error of the mean) and open surgery (431.1 +/-240.4 pg/ml and 196.7 +/- 56.5 pg/ml, respectively). Serum C-reactive protein levels also rose postoperatively, with a peak on the second day, but showed similar values after laparoscopic-assisted (107.1 +/- 12.1 mg/l) and open (128.3 +/- 17.5 mg/l) surgery. Plasma granulocyte elastase levels peaked on the first and second postoperative day and were found elevated almost throughout the five-day observation period. Comparison between the groups revealed significantly (P < 0.02) lower values after laparoscopic-assisted (Day 1, 46.5 +/- 8.9 microg/l; Day 2, 41.9 +/- 5.9 microg/l) when compared with open surgery (Day 1, 89.7 +/- 13.8 microg/l; Day 2, 91.4 +/- 14). CONCLUSIONS: Serum IL-6 and IL-10 may not be ideal measures for evaluation of the degree of tissue trauma in laparoscopic-assisted and open resections in Crohn's disease, probably because of interference with disease-specific cytokine interactions. In contrast, granulocyte elastase has to be considered a strong marker discriminating the different severity of surgical trauma induced by laparoscopic-assisted vs. open resection in Crohn's disease.

[Thoracic actinomycosis--a case report]. / Thorakale Aktinomykose--Eine Fallbeschreibung.

BACKGROUND: Actinomycosis is caused by a variety of gram-positive anaerobic or microaerophilic rods belonging to the genus Actinomyces or Propionibacterium. The production of suppurative abscesses or granulomas that eventually develop draining sinuses are hallmarks of the disease. We describe the case of a 55 year old smoker who presented himself 4 months ago with right thoracic pain and an unproductive cough. He developed a warm, red mass in the lower part of the right thorax. We performed an ultrasound guided needle aspiration and the pathologic examination revealed typical sulfur granules and masses of neutrophils in the aspirate. After surgical resection of the abscess and under high-dose therapy with penicillin G the further course of disease was uneventful. CONCLUSIONS: Although uncommon, thoracic actinomycosis should always taken into account in the differential diagnosis of chronic inflammatory processes that involve the pulmonary parenchyma or pleural space.

[Symptomatic abdominal aortic aneurysm and left-sided infrarenal vena cava]. / Symptomatisches Bauchaortenaneurysma und linksseitige infrarenale Vena cava.

Coincidence of an abdominal aortic aneurysm and abnormalities of the inferior vena cava is a rare condition but has significance for surgical therapy. By the preoperative use of various imaging techniques and adapted surgical procedure the risk of the operation is decreasing to a minimal level. A case of symptomatic abdominal aneurysm and left-sided infrarenal vena cava is presented and the importance of preoperative examinations and operative strategy is discussed.

Effectiveness of a hands-on training course for laparoscopic spine surgery in a porcine model.

BACKGROUND: Although it is widely proposed that surgeons, before introducing a novel laparoscopic technique in man, should practice in an appropriate animal model for acquisition of the necessary technical skills, the effectiveness of those hands-on training courses are rarely documented. METHODS: In 1995 we have organized eight hands-on training courses for laparoscopic anterior interbody spine fusion in an in vivo porcine model. A total of 72 colleagues from 50 different centers of 12 countries participated, including orthopedic, trauma, visceral, neuro-, and vascular surgeons. Quality and effectiveness of the course were evaluated by a questionnaire after a 1.5- to 2.5-year period. RESULTS: During this time, 42.2% of the participating centers had applied the new technique successfully in man. Centers which participated in the course with a team that included a skilled laparoscopic surgeon and an orthopedic or trauma surgeon introduced the technique more frequently to clinical practice (57.9%) than those represented by only one participant (30. 8%). Moreover, there was a tendency toward a more frequent introduction of the technique to clinical practice in centers associated with university hospitals (57.1% vs. 29.2%), indicating the requirement of a particular infrastructure for this complex interdisciplinary procedure. Almost all participants (98.3%) agreed that for novel surgical techniques requiring advanced technical skills, there should first be training in a large animal model before the technique is applied in man. CONCLUSIONS: Complex laparoscopic procedures (i.e., laparoscopic spine surgery) can be successfully learned by in vivo hands-on training courses. We propose that for refinements and modifications of the technique (e.g. , the lumboscopic approach), there should also first be training in a large animal model before these are applied in man.

[Surgical treatment of Crohn disease based on the inflammatory pattern]. / Chirurgische Behandlung des M. Crohn auf der Basis des entzündlichen Befallsmusters.

286 patients with Crohn's disease were classified on the basis of the inflammatory pattern at their first operation as type 1 (Ileitis: n = 116), type 2a (segmental colitis: n = 60), and type 2b (total colitis: n = 108); 2 patients remained unclassified. At the same age at operation of 31.9 +/- 10.7 yrs symptoms were known in type 1 for 3.4 +/- 3.9 yrs, but for 7.5 +/- 5.7 yrs in type 2b. Main indication in type 1 was stenosis (56.9%), whereas in type 2b intractabilitiy (68.5%) predominated. Type 2a was intermediate concerning duration of symptoms and relationship of indications including fistulas. Standard-procedures were ileocecal resection (92.2%) in type 1, and colectomy (90.7%) in type 2b. In type 2a ileocolic resections and partial colectomies were mostly done. During the following 3.9 +/- 3.8 yrs reoperation rate due to disease progression was 13.6% in type 1, 25.5% in type 2a and 18.5% in type 2b. The cumulative risk of ileal resection at ten years due to new inflammation was significantly (p < 0.01) higher in the case of ileocolic/ileorectal anastomosis than of ileostomy (38% vs. 11%). In contrast, cumulative probability of a colorectal resection was significantly (p < 0.05) higher in type 2 (16%) when compared to type 1 (1.5%). Primary ileal loss was significantly (p < 0.01) higher in type 1 (37 +/- 23 cm) compared with type 2a (25 +/- 28 cm) and type 2b (17 +/- 21 cm). Loss of continence occurred in 0%, 3.3% and 53.7% respectively. With reoperations additional loss of ileum decreased in all types, whereas in type 2 loss of anorectal function increased. Including reoperations the rate of major complications was 9.8% and lethality was 0.8% (3/386). Resections in Crohn's disease are unavoidable due to shrinking therapeutical alternatives in the course of the disease. Owing to limited resections, loss of bowel may not exceed ileum in type 1, whereas the same resectional policy cannot avoid the total loss of the colorectum eventually in type 2. Both limited surgery and repeated resections help to maintain function as long as possible. Due to the high safety-standard the number of operations does not impair the success of the surgical concept.

[Laparoscopically assisted surgery in Crohn disease]. / Laparoskopisch assistierte Chirurgie bei M. Crohn.

UNLABELLED: From Jan. 1993 to Apr. 1997 intestinal resections in Crohn's disease have been performed in 275 patients. 89 patients have been operated on laparoscopic assisted. The following parameters were analyzed: previous laparotomies, extent of resection, steroid medication, conversionrate, complications, operative time and postoperative stay. Endpoints were: conversionrate, complications, reconvalescence and overall satisfaction with the laparoscopic technique. RESULTS: The duration of the disease ranged from 1 to 16 years (x = 6). 47 patients were under steroid medication at the time of surgery. 30 patients had undergone previous laparotomies. In 10 patients the operation had to be converted into open surgery. The following procedures have been performed: ileocaecal resections (45), anastomotic resections (14), small bowel resections (4), hemicolectomies (12), colectomies (9), loopileostomies (4), adhesiolysis (1). Minor complications occurred in 6.7% of patients, major complications in 5.6%. Operative time ranged from 70 to 420 minutes (x = 173.7). The postoperative hospital stay was 13.3 days in the average. CONCLUSION: The morbidity of 12.3% is not higher than in open surgery. When complications do not occur the patients benefit from early convalescence, better cosmetics and shorter hospital stay.

[Laparoscopically-assisted proctocolectomy with ileoanal pouch in ulcerative colitis]. / Die laparoskopisch assistierte Proktokolektomie mit ileoanalem Pouch bei Colitis ulcerosa.

Laparoscopic assisted proctocolectomy with ileoanal pouch is a technical alternative to the conventional open procedure. The aim of this technique are better cosmetics. Mobilisation of the colon is achieved laparoscopically. Rectal resection, J-pouch creation, and pouchanal anastomosis are performed via a Pfannenstiel incision. Laparoscopic assisted proctocolectomy has been performed in five selected patients, three female and two male aged 17 to 36 years. Operative time ranged from 305 to 420 minutes. Intra- and postoperative complications were not encountered. Postoperative hospital stay ranged from 13 to 16 days. On a scale from 1 to 10 the average quality of life was graded 9 and the overall satisfaction level with the results of surgery scored 10. Function was identical to open surgery in not selected patients.

[Laparoscopic 2-level fusion of the lumbar spine with Bagby and Kuslich implants]. / Laparoskopische 2-Etagenfusion der lumbalen Wirbelsäule mit Bagby-and-Kuslich(BAK)-Implantaten.

In a 50-year-old female patient, presenting with permanent low lumbar back pain and intermittent neurological alterations due to degenerative disc disease L4-5 and L5-/S1 we demonstrate that two-level anterior interbody fusion can be performed via laparoscopic transabdominal instrumentation using BAK interbody implants. Intervertebral disc space L5-/S1 was stabilized approaching the spine caudally of the aortic bifurcation, while disc space L4-L5 required an approach from the left lateral aspect, mobilizing the aorta and vena cava to the right. The postoperative course was without complications and allowed discharge from the hospital on day 8. X-ray control 4 months later demonstrated restoration of adequate disc space at L4-L5 and L5-/S1 and appropriate positioning of the implants.