Biomechanical study of the Delta plate and the TriLock Delta condyle trauma plate.

PURPOSE: The aim of this study was to evaluate in mandibular condylar process fractures the biomechanical stability of osteosynthesis using the Delta plate and the TriLock Delta condyle trauma plate and to compare these with 2 4-hole miniplates. MATERIALS AND METHODS: The condyles of 120 porcine mandibles were fractured at a defined location. After anatomic reduction, the fractures were fixed with a Delta plate, a TriLock Delta condyle trauma plate, or 2 4-hole miniplates (40 per group). Each group was subjected to linear loadings in 4 different directions with a universal mechanical testing machine (TIRA Test 2720). Yield load and yield displacement were measured for the 2 Delta plates and the 2 miniplates. Means were derived and compared for statistical significance using the Kruskal-Wallis test with a confidence level of 95% (P < .05). RESULTS: None of the plates broke. In 4 cases using the double miniplate and in 2 cases using the Delta plate, osteosynthesis screw loosening was registered. In lateral-to-medial and anterior-to-posterior directions, the 2 miniplates tolerated the highest loads. From medial to lateral and from posterior to anterior, the TriLock Delta condyle trauma plate resisted the highest loads. However, there was a statistically significant difference among all osteosynthesis systems only for medial-to-lateral loads. Statistical analysis for displacement showed significant differences among all plates in the 4 directions. CONCLUSIONS: This biomechanical study indicates that for rigid internal fixation of condylar fractures of the mandible, similar to 2 miniplates, the 2 Delta plates (Delta plate with gliding holes and TriLock Delta plate) fulfill the principles of a functional and stable osteosynthesis. Both are able to resist physiologic strains. The locking plate (TriLock Delta condyle trauma plate) has the advantages of greater primary stability and decreased likelihood of screw loosening.

Stability of fixation of diacapitular fractures of the mandibular condylar process by ultrasound-aided resorbable pins (SonicWeld Rx® System) in pigs.

To assess the stability of osteosynthesis in diacapitular condylar fractures we compared fixation using ultrasound-aided resorbable pins with poly-(D,L)-lactide (SonicWeld® Rx, KLS Martin, Tuttlingen, Germany) with that of titanium screws in 20 pig mandibles, 10 in each group. Isolated diacapitular fractures were created using a surgical chisel. Ten fractures were each repositioned and fixed by two pins (17 and 11 mm long, 2.1mm in diameter), and 10 fractures were fixed by two titanium screws of equal length, 2.0mm in diameter. Shear tests were done immediately after treatment to measure the maximum force to disrupt the fixation. Fixation with pins resisted mean shear forces of 310N until the pins fractured, whereas fixation with titanium screws failed at 918N when the screws pulled out of the bone. Long-term stability and resorption of pins will have to be analysed in an in vivo study.

Bone block fixation by ultrasound activated resorbable pin osteosynthesis: a biomechanical in vitro analysis of stability.

OBJECTIVES: The aim of this study was to determine the compound strength of the fixation between 2 blocks of synthetic bone using ultrasound activated resorbable pins (regarding drill hole diameter) and compare them to fixation with titanium miniscrews. Resorbable pins were up to 17 mm long. STUDY DESIGN: Two synthetic bone blocks (Sawbone) were fixed by either a resorbable pin or miniscrew osteosynthesis. Maximum tensile forces were determined mechanically. Pin lengths of 7 mm, 11 mm, and 17 mm were analyzed in relation to different drill hole diameters. RESULTS: The ideal drill hole configuration was a combination of diameters of 2.1/1.6 mm (in a lag screw configuration). Mean maximum tensile force was 80 N for 7 mm pins (105 N/11 mm, 69 N/17 mm). In comparison, tensile forces of titanium screws were 20 N (7 mm), 97 N (11 mm), and 135 N (17 mm). CONCLUSIONS: Osteosynthesis by resorbable pins reached equal compound strength levels compared with titanium miniscrews. This in vitro study was the basis for a clinical trial of ultrasound-guided resorbable pin osteosynthesis.

Mechanical loading of orthodontic miniscrews - significance and problems: an experimental study.

Orthodontic miniscrews are exposed to three mechanical loading phases during clinical use: torsional loading upon insertion, flexural loading during anchorage function, and torsional loading upon removal. The aim of this study was to simulate clinical loading conditions for different types of orthodontic miniscrews in vitro to quantify the effects of combined torsional and bending stress. Various orthodontic miniscrew systems (Lomas, Dual-top, Aarhus anchorage, Tomas-pin and T.I.T.A.N.-pin) comprising 10 samples each were subjected to the following loading sequences in vitro: a torsional load corresponding to manual insertion with limited torque; and flexural loading at two different insertion depths. For all screw systems with torsional pre-loading (simulating insertion), subsequent flexural loading (simulating anchorage) yielded permanent deformations of approximately 0.15-0.25 mm, depending on the insertion depth. Since EDX analysis revealed comparable elemental compositions for the different screw systems, the differences in mechanical properties are attributed to screw design. Torsional loading during screw insertion may cause premature mechanical weakening and needs to be minimized. Unless fully inserted, screws show pronounced plastic deformation and hence fracture risk under subsequent flexural loading.

[Physicians' responsibility: doctor-patient relationship]. / Arztliche Verantwortung: das Arzt-Patient-Verhältnis.

The physician-patient relationship is of fundamental importance not only for individual patients but for the health care system in general and thus also for bioethical reflections. We give an overview on current research and analyses regarding the physician-patient relationship. A comprehensive ethical analysis takes conditions (historical and societal influences, norms and principles), the action itself and its consequences on the individual level (patient, physician) and societal level (health care system) into consideration. At present, two models of the physician-patient relationship are predominantly discussed, especially in terms of care ethics: evidence-based patient choice and shared decision making. These forms of relationships seem to be promising for several reasons, but might not fit all situations, and suitable for all preferences of patients and physicians in the same way. We conclude with a summary of the current debate and point out some of its shortcomings.

Plate osteosynthesis of the mandibular condyle.

The aim of this study is to evaluate and compare the biomechanical stability of various osteosynthesis materials for mandible condylar-process fractures. On 160 porcine mandibles, four different monocortical plating techniques (40 per group) were investigated. Condyles were fractured at a defined location from the incisure to the posterior border. After correct anatomical reduction the fractures were plated, using four different techniques. Osteosynthesis materials used were the delta plate, the trapezoid plate, the dynamic compression plate and double mini-plates. Each group was subjected to linear loading in lateral to medial, medial to lateral, anterior to posterior and posterior to anterior directions by a universal mechanical testing machine TIRAtest 2720. Yield load, yield displacement were measured for the different plates. Statistically significant differences were noted between the fixation groups in all four directions. Rigid internal fixation with double mini plates showed the best stability in all directions except posterior to anterior. In this direction, the delta-plate resisted the highest loads. In the three other directions, the delta plate was second best with data similar to double miniplates but lower in magnitude.

[Desire for a child and desired children--possibilities and limits of reproductive biomedicine]. / Kinderwunsch und Wunschkinder: Moglichkeiten und Grenzen der In-vitro-Fertilisations-Behandlung.

UNLABELLED: Definition of problem: BACKGROUND: Reproductive Biomedicine and new reproductive technologies (ART) belong to the fields of medicine that initiated most of the discussion on enhancement and desire fulfilling medicine in bioethics during the last years. One of the crucial questions to be answered is the definition of the right to procreate/right for a genetically related child. Closely connected are controversial opinions in regard to the definition of sterility as a disease/illness, or a mere fate, or malfunction, which does not have to be medically cured. Arguments: After a cursory description of the national and international debate, we introduce some results of our 'bioethical field studies', exploring and comparing the views of experts (human geneticists, ethicists, pediatricians, obstetricians and midwifes) and couples/patients (IVF couples, high genetic risk couples and couples with no known risk for an inherited disease or infertility problem) on sterility, the right to procreate, possibilities and appropriate limits of IVF in Germany. CONCLUSION: According to the WHO, sterility has to be defined as an illness, if the respective couples have a desire for a child. IVF can be a means for a cure. Since 2004, Germany does no longer supply a thoroughly insurer financed IVF treatment. Our surveys indicate that this change, though supported by many experts, is hard to accept for couples concerned. Only obstetricians share the WHO's view that sterility should count as an illness. Many ethicists see a proclaimed human right to procreate as merely negative right, although many support free IVF treatment for poor couples. We challenge the expert majority view on the basis of the capability approach (Amartya Sen) and functional liberalism (Herlinde Pauer Studer) and with a view to the international state of the art in IVF. The desire to have children cannot be reduced to a non-authoritative preference whose fulfillment is optional, but has to be conceptualized as a normative need that ought to be met.

What is the preimplantation embryo?

We present results from our 'bioethical field studies', which explore and compare the views of experts, patients and the general public on the beginning of human life and the status of the preimplantation embryo in Germany. Using a qualitative and quantitative multi-method approach, we found crucial differences in the categorization of the beginning of human life within the expert group (representative samples of human geneticists n=104, ethicists n=168, midwives n=294, obstetricians n=147, paediatricians n=166), and between expert and lay samples (IVF couples n=108, high genetic risk couples n=324, general population n=1017). The majority of lay respondents as well as paediatricians and obstetricians chose nidation, the moment when the implantation of the fertilized egg into the uterus takes place, as the crucial boundary that marks the beginning of human life, whereas the majority of (female) human geneticists, ethicists and midwives voted for conception as the decisive point in time. The views of all groups on the status of the preimplantation embryo differed from the assumptions underlying German legislation (Embryo Protection Act). Religiousness and religious affiliation, gender, attitudes towards disabled people, post-material values and a present desire for a child were identified as independent factors influencing attitudes towards the preimplantation embryo in the population sample. The results are discussed within a broader philosophical and social science perspective of constructivism versus essentialism, proposing a truly interdisciplinary approach to such bioethical core issues as new reproductive technologies and the status of the preimplantation embryo.

Public, expert and patients' opinions on preimplantation genetic diagnosis (PGD) in Germany.

The regulation of reproductive medicine technologies differs significantly among Western industrialized countries. In Germany, preimplantation genetic diagnosis (PGD) is prohibited due to the Embryo Protection Act, which came into force in 1991. In the last 5 years, this prohibition has been vigorously debated. In the present studies, which are part of the German research programme on ethical implications of the Human Genome Project, representative surveys were undertaken to assess the attitudes on PGD in the general population (n = 1017), five relevant expert groups (n = 879), high genetic risk couples (n = 324) and couples undergoing IVF (n = 108). All groups surveyed clearly favoured allowing PGD in Germany. Compared with the results of recently conducted population surveys in the UK and the USA, where PGD is already carried out, public approval of PGD does not differ significantly. The influence of restrictive biopolitics on the apparently liberal public opinion towards new reproductive technology seems to be marginal according to the present data, which should carefully be considered in the ongoing legislation process on human reproduction.

Preimplantation genetic diagnosis (PGD): European perspectives and the German situation.

This article gives an overview about the ethical dispute on preimplantation genetic diagnosis (PGD), its legal status and its practical usage in Europe. We provide a detailed description of the situation in Germany wherein prenatal diagnosis is routinely applied, but PGD is prohibited on the basis of the internationally unique embryo protection act (EPA) that was put into force in 1991. Both PGD and stem cell research were vigorously debated in Germany during the last four years. As regards the PGD debate specifically, the voices of the ones directly affected were not adequately taken into consideration. We describe the predominant lines of argumentation in this debate and some essential results of our "bioethical field study" of opinions on and usage of PGD in Germany and their implications for the German legislation and ethical theory.

Prospective evaluation of imaging procedures for the detection of pancreaticoduodenal endocrine tumors in patients with multiple endocrine neoplasia type 1.

Early identification of pancreaticoduodenal endocrine tumors (PETs) in multiple endocrine neoplasia type 1 (MEN-1) is mandatory, because these tumors represent the most common cause of death within the syndrome. The diagnostic value of imaging procedures has therefore been evaluated in a prospective observational study. Between December 1997 and June 2003 twenty-two MEN-1 patients with genetically confirmed disease were followed for PETs using a standardized screening program with serum hormone measurements, endoscopic ultrasonography (EUS), computed tomography (CT), and somatostatin-receptor scintigraphy (SRS). Results could be validated by surgery and histopathology in 13 patients during 18 operations. In 12 asymptomatic patients with tumors measuring 10 mm or less, who have not yet undergone operation, PETs were detected by EUS in 12/12, by CT in 1/12, and by SRS in 2/11 cases. In 13 patients who have undergone surgical exploration EUS, CT, and SRS were true positive in 12 of 16, 7 of 13, and 12 of 17 cases, respectively, although the number of tumors detected by each imaging procedure alone was lower than the number detected intraoperatively and histopathologically in almost every case. A solitary liver metastasis in one patient and a nonfunctioning PET recurrence in another were identified only by SRS. Endoscopic ultrasonography is the most sensitive imaging procedure for the detection of small (< or = 10 mm) PETs in MEN-1, whereas SRS is the procedure of choice for the identification of metastases of MEN-1 PETs-i.e., for staging. Detection of PETs at an early stage by an aggressive screening program using EUS may lead to prompt surgical intervention and improved prognosis of MEN-1 PETs.