[Registration procedure for incidents with implants]. / Meldeverfahren bei Vorkommnissen mit Implantaten.

Incidents involving implants, whether there is a break in the osteosynthesis plate or a synthetic inlay of an endoprosthesis, are incidents with mostly severe repercussions for the patient with immediate and delayed effects for the clinic involved and the manufacturer.

[Medical innovations in the area of conflict between certification and allowance]. / Medizintechnische Innovationen im Spannungsfeld zwischen Zertifizierung und Vergütung.

The medical technology industry is one of the most innovative industries in Germany. Once a medical product is developed, it will be certificated according to European harmonized guidelines and norms. The respective national regulations in Germany are stipulated in the Medical Devices Act (MPG). Part of the certification process is a clinical assessment with the aim to prove that the medical device complies with the so-called essential requirements concerning safety, performance and suitability for the intended use as defined by the manufacturer. A clinical trial may be necessary to establish compliance with these requirements. During this clinical trial the devices are being assessed in patients according to strict requirements by law. The main criticism by the funding agencies is that these trials do not sufficiently apply methods of evidence-based medicine. Thereby they are not useful for assessing the medical benefit of the devices. The manufacturers' counter-argument is that the products are bearing the CE mark, that they comply with the uniform European standards and that their quality therefore has been appropriately assessed. This discussion relates to the question about payment for the products, as according to the Fifth Social Act the funding agencies are only permitted to finance products with a scientifically proven medical benefit. The present article discusses both positions in the context of national and international legislation for the certification of medical devices and presents possible solutions.

[Cartilage damage caused by a dislocated resorbable interference screw of poly(L-lactide) 46 months after anterior cruciate ligament reconstruction]. / Knorpelschaden, verursacht durch eine dislozierte resorbierbare Interferenzschraube aus Poly(L-Lactid), 46 Monate nach vorderer Kreuzbandplastik.

The case of a 44-year-old male patient is reported, who was operated 4 years after a cruciate ligament replacement. A nearly completely intact biodegradable screw was removed arthroscopically. The screw dislocated from the tibial canal into the joint and caused damage to the retropatellar cartilage which was treated by debridement and lateral release. A material analysis was done on the explanted screw which showed no material fault. A review of the literature reporting adverse events connected to biodegradable implants was carried out. Nine papers reporting about adverse event are cited. There seem to be three main problems: delayed degradation, foreign body reaction and the filling of graft tunnels with non-ossified tissue. Instructions for the use of biodegradable interference screws were requested from seven manufacturers to compare the given information about the degradation behaviour. The information given on the period of time until the screws would be completely resorbed were heterogeneous, ranging from no specific information about the time span at all up to 24 months. More research is needed to identify the degradation behaviour more precisely and clarify the potential risks connected to biodegradable implants. Their use should be reconsidered critically.

[Computer-assisted navigated cup placement in primary and secondary dysplastic hips]. / Computerassistierte Hüftpfannennavigation bei primär- und sekundär dysplastischen Ausgangssituationen.

AIM: The positioning of an acetabular implant has great influence on the range of motion as well as the charger of dislocation of total hip arthroplasty. Using modern CAS systems the reproduction of the cup position after three-dimensional planning based on computed tomography is possible. We investigated the reliability of the position of the acetabular implant in primary and secondary dysplastic cases. METHOD: Within a prospective randomised study in a total of 100 hip replacements with postoperatively controlled cup position using a computed tomography, we reinvestigated especially the 18 dysplastic and two secondary dysplastic cases. RESULTS: In the dysplastic cases we could realise nearly the same anteversion angles (22.4 degrees to 21.5 degrees) with a bigger standard deviation (+/- 7.68 degrees to +/- 7.29) than in the normal collective. Even the inclination angles (44.5 degrees +/- 5.47 degrees) could be realized nearly the same as in the normal cases (42.3 degrees +/- 4.31 degrees). The depth of the cup implantation could be realised in 15 of 18 cases. CONCLUSION: The CAS system is helpful even in dysplastic cases. The advantage of three-dimensional preoperative CT-based planning is apparent. The surgeon is not able to plan and realise the ideal cup position in some individual.

[Empirical studies of the reliability of surgical navigation systems]. / Empirische Studien zur Zuverlässigkeit von chirurgischen Navigationssystemen.

A number of studies demonstrate the clinical relevance of systems for computer assisted surgery (CAS systems). As however studies on human error in medicine indicate, reliability of the results strongly depends on aspects of usability and error tolerance of the system. This paper presents studies which aim to assess these aspects of reliability of CAS systems. In a clinical study, interaction with a CAS system by 16 expert and novice surgeons was observed and assessed. From 133 recorded incidents 41% were rated to have significant impact on the clinical result or to inhibit successful completion of the task, which indicates a low degree of error tolerance of the system. These findings are supported by the results obtained from questionnaire, were learnability and error tolerance were judged to be not sufficient.

Registration of bone surfaces, extracted from CT-datasets, with 3D ultrasound.

An essential task of computer assisted surgery is the registration of preoperative image data with the coordinate system of the operating room. This can be reached by using intraoperative imaging and registrating preoperative and intraoperative datasets. For intraoperative imaging ultrasound is a powerful tool due to the lack of ionizing radiation and because of its fast, inexpensive and easy data acquisition. We propose a surface volume matching algorithm for the registration of bone surfaces and ultrasound volume data. The bone surface is estimated from the preoperative CT data by taking into account that ultrasound only shows parts of the bone surface. By our method reliable matching results are obtained. They are shown with data of the lumbar spine.

Registration of 3D CT and ultrasound datasets of the spine using bone structures.

OBJECTIVE: In navigated orthopedic surgery, accurate registration of bones is of major interest. Usually, this registration is performed using landmarks positioned directly on the bone surface. These landmarks must be exposed during surgery. Our goal is to avoid the exposure of bone surface for the sole purpose of registration by using an intraoperative ultrasound device that can localize the bone through tissue. METHOD: We propose an algorithm for the registration of CT and ultrasound datasets that takes into account the fact that ultrasound produces very noisy images (speckle) and shows only parts of the bone surface. This part is made from the CT dataset. Next, a surface volume registration is performed by searching for a position of the estimated surface that maximizes the average gray value of the voxels in the ultrasound dataset covered by the surface. RESULTS: The algorithm was implemented and validated using an ex vivo preparation of a human lumbar spine with surrounding muscle tissue. On the basis of this data, the method has a large radius of convergence and a repeatability of 0.5 mm for displacement and 0.5 degrees for rotation. CONCLUSIONS: A robust algorithm for the registration of 3D CT and ultrasound datasets is presented. The computation time seems sufficiently short to permit intraoperative use.

[Relevant predictors of the 5 year outcome of patients with schizophrenic or similar paranoid psychoses (author's transl)]. / Relevante Merkmale für die 5-Jahres-Prognose von Patienten mit schizophrenen und verwandten paranoiden Psychosen.

In a 5 year follow-up study of 81 patients suffering from schizophrenic or similar psychoses many of the predictors known from the literature concerning the outcome of schizophrenia were confirmed. In accordance with the results of the follow-up study on patients from the International Pilot Study of Schizophrenia (IPSS), long lasting professional disintegration and psychiatric hospitalisation preceding index-admission were of special prognostic importance. However in contrast to this follow-up study, other psychopathological data, especially minus symptoms proved to be of considerable prognostic significance. As a result of stepwise multiple regression analyses, combinations of the 5 best characteristics for each outcome-criterion have been found which explain a significantly greater part of the variance than single characteristics.

Outcome in schizophrenic and similar paranoid psychoses.

A 5-year followup study of patients with schizophrenic or paranoid psychoses was performed using standardized instruments. Less than half of the patients had a poor global outcome. Several findings from other recent outcome studies were replicated. Besides data on occupational history and psychiatric hospitalization, psychopathological characteristics assessed at discharge by psychiatrists' ratings and patients' self-ratings proved to have predictive value.

[The prognostic value of psychopathometric data about the psychopathological state of schizophrenic patients on admission and discharge (author's transl)]. / Die prognostische Bedeutung psychopathometrischer Aufnahme- und Entlassungsbefunddaten schizophrener Patienten.

A psychopathometric study on the course of schizophrenic patients was carried out in order to analyse the long-term prognostic value of the psychopathological state on clinical admission and discharge. Eighty-one patients with schizophrenic or similar psychoses were rate three times using well-validated psychopathological scales ("Inpatient Multidimensional Psychiatric Scale", "Clinical Selfrating Scales"): in the beginning, at the end of clinical treatment and 5-6 years after discharge. As for differentiated or global outcome-criteria, the psychopathological state on discharge was of more prognostic importance than the psychopathological state on admission. There existed syndrome-specific relationships between discharge and follow-up, i.e., in general each syndrome correlated most closely with itself between the two times of measurement. As for global outcome criteria, depressive-apathetic symptoms were of more special importance than productive schizophrenic symptoms indicating a poor outcome. The stepwise multiple regression analysis gave prognostically optimal combinations of IMPS-syndromes at admission and discharge which were different for each outcome criterium. Nevertheless, some syndromes were repeatedly among the best predictors. The combination of best predictors explained a greater part of outcome-variance than one predictor alone. The prognostic value of the combination could be optimated by including the factors of the self-rating scales.

[Psychopathometric examinations on patients with schizophrenia and related psychoses (author's transl)]. / Psychopathometrische Verlaufsuntersuchungen an Patienten mit Schizophrenien und verwandten Psychosen.

Eighty one patients with schizophrenic or similar psychoses were tested three times using different psychopathological scales: at the beginning and at the end of clinical treatment, and 5-6 years after discharge. The psychopathometrical description showed an improvement in productive-psychotic and depressive-apathetic symptoms during clinical treatment and the deterioration at follow-up. For example 67% of the patients suffered from marked paranoid symptoms at admission, only 14% at discharge, but 30% at follow-up. The configuration-frequency-analysis on syndrome-intensities allowed a more differentiated insight into the frequency of improvement and deterioration in particular cases. As to paranoid symptoms for example, 26% of the patients showed deterioration at follow-up. The majority of the depressive states seen on discharge were already in existence on admission. The results of the self-rating and the rating by the psychiatrist was not in complete concordance.