E I N L E I T U N G Das proximale Femur ist eine häufige Lokalisation von primären Knochentumoren und Metastasen. Die Implantation von Tumorspezialendoprothesen stellt bei der Rekonstruktion des Knochendefektes eines der wichtigsten Therapieverfahren dar. Als Alternative zu ablativen Verfahren wie der Amputation kann dabei die Extremität erhalten bleiben, Schmerz gelindert und eine adäquate Funktion erreicht werden. Auf Grund der kontinuierlich steigenden Überlebensraten der Patienten ist, neben der Dauerfestigkeit der hochbelasteten Implantatastiele, die aseptische Lockerung verstärkt in das Zentrum des Interesses gerückt. Ziel der Untersuchung war, den Einfluß verschiedener intramedullärer Stiellängen und -materialien auf die Dehnungsverteilung des Femurs nach proximalem Femurersatz zu bestimmen.

Skiboards are defined as skis between 70 and 130 cm in length. Until now they are typically not sold with release bindings. Several studies have shown that when using skiboards,tibia fractures and shoulder injuries occur at a significantly higher rate than with traditional length skis. This paper analyzes the effects the reduced length and the lack of a release binding may have on specific kinematic and dynamic parameters in a typical fall situation. This is done by both an experimental and a theoretical approach, the latter using a computer simulation. The results show that (1) a twist release seems to be necessary (2) a skier using a skiboard is prone to suffer highly dynamic forward falls, (3) a conventional release binding may not be able to prevent the skier from getting injured in this specific situation and (4) a new type of skibinding should be considered. As for the moment no appropriate technical solutions are available, it is concluded that the (novice) skiboarder has to be aware of the fact that there are some inherent risks due to the new equipment.

In a retrospective study the results of operatively treated ankle joints were critically discussed. In a period from January 1, 1977 to December 31, 1994, a total of 35 arthrodeses were carried out. Seventeen patients were followed up clinically, radiologically and with a gait analysis. Not only the radiological surgical result was of interest, but also the heel-toe movement of the stiffened foot in the individually adapted orthopedic footwear compared to standard footwear. A significantly improved heel-toe movement was found in orthopedic shoes, although there is a reduction of movement in the hindfoot in the sagittal plane.

Questions remain concerning the effect of variations in cholesterol intake on plasma cholesterol concentration, as well as on the role of factors modulating the metabolic impact of this dietary intervention. To define the impact of wide variations in dietary cholesterol intake on plasma total and low-density lipoprotein (LDL) cholesterol concentrations, as well as testing the hypothesis that resistance to insulin-mediated glucose disposal would accentuate the increase in plasma total and LDL cholesterol concentrations in response to a given increment in dietary cholesterol intake, we performed a prospective, randomized study comparing diets varying in cholesterol content in 65 healthy, postmenopausal women, 31 defined as insulin-resistant and 34 as insulin-sensitive. The changes in total and LDL cholesterol in response to increments in dietary cholesterol of up to approximately 800 mg/day were modest in magnitude, without evidence of a statistically significant diet-induced increase in cholesterol concentration, or of any difference in the responses of insulin-resistant as compared with insulin-sensitive women. These results indicate that relatively large increments in dietary cholesterol intake had little effect on total or LDL cholesterol concentrations in healthy, postmenopausal women, irrespective of whether they were insulin-resistant or insulin-sensitive.

Knee injuries in alpine skiing, especially the rupture of the anterior cruciate ligament (ACL), are still the leading indication for surgical treatment. The boot-induced anterior drawer (BIAD) caused by the backward fall is one of the possible injury mechanisms.We investigated the landing of approximately 250 jumps to collect data for a computer model of the BIAD. During our experiments one test subject suffered an ACL rupture of his right knee. This accidental event was recorded on video for later 2D motion analysis. Furthermore, the muscle activity of four muscles (vastus medialis and lateralis, biceps femoris and semitendinosus) was registered for both lower extremities during this event. Seven more subjects were analyzed under identical experimental conditions, thus representing an adequate reference group.The results of the 2D motion analysis will be presented and compared to the results of the reference group. Further, the registered EMG signal of the injured subject will be illustrated and discussed in relation to a reference subject.Our observations allow the conclusion that during landing situations different kinematics besides those described for the BIAD, in combination with certain muscular conditions, may lead to an ACL rupture.

The KT2000 knee ligament arthrometer manufactured by the MEDmetric©Corporation is used in the field of orthopedics to establish quantitatively the size of the anterior and posterior draw phenomena of the knee joint. The basis for the measurement is the Lachman test in which a force is applied to the tibia relative to the femur. The resulting displacement is limited by the cruciate ligaments. The measurements obtained for a potentially injured knee are compared with those of the healthy knee and empirical threshold values, and serve as a basis for deciding whether to operate on patients with cruciate ligament insufficiency. The subject of the present study is a design shortcoming of the KT2000 that may falsify the measured results when the device is not correctly employed. A simple mechanical modification of the KT2000 can reduce this error. In the present study, the error is quantified and we show how the modification can keep it within tolerable limits.

Surveys undertaken at the evaluation center for skiing accidents run by a German sports insurance company show that approximately 80% of all skiing accidents are due to observation errors, perception errors or inattentiveness in conjunction with skiing errors. Therefore, the efficiency of the eyes plays a vital role in skiing. Between 1995 and 1996 the following investigations were carried out into aspects of visual and perceptive acuity on the ski slopes:Registration of the eyesight of leisure-time skiers.Tests on the influence of visual acuity on the ability to recognize potential danger spots on the slope.Tests on the influence of different color filters on eyesight (laboratory tests) and perceptive acuity on the ski runs (field tests).Results: In 28.8% of the skiers tested optical correction of visual acuity was needed. The skiers were tested under those conditions in which they are skiing. In stereoscopic depth perception, which is also of great importance, for example, in assessing distances, deficits were present in 19.7% of the skiers tested. Approximately 39.7% of the tested skiers wear either glasses or contact lenses in daily life. However, only about 65.5% of them wear these on the slopes, too. Visual acuity and depth perception have a crucial influence on the ability to recognize potential danger spots on a ski slope. With a reduction in visual acuity, recognition was found to undergo a clear-cut decrease, with potential danger spots being recognized less efficiently and at a later time, An improvement in visual power through filters of various colors was recorded only in unfavorable light conditions and poor visibility (dim light, shade, fog, etc.). On average, more danger spots were distinctly recognized with yellow goggles than with colorless filters.

Modular endoprostheses are a common method in the treatment of musculo-skeletal tumors. The assembled units of the highly loaded implants are linked by socket joints. During wear, the links have to resist multi-axial loads (axial compression, bending and torsion) necessarily. The loads can occur phase shifted and are usually not bulked. The conditions of assembling and disassembling during implantation and revision are neither defined nor reproducable. In order to evaluate various concepts of fitting and securing, the introduced computer-controlled hydraulic test bench allows any combination of axial, bending and torsion loads, also phase shifted.

The KT2000 knee ligament arthrometer manufactured by the MEDmetric Corporation is used in the field of orthopedics to establish quantitatively the size of the anterior and posterior draw phenomena of the knee joint. The basis for the measurement is the Lachman test in which a force is applied to the tibia relative to the femur. The resulting displacement is limited by the cruciate ligaments. The measurements obtained for a potentially injured knee are compared with those of the healthy knee and empirical threshold values, and serve as a basis for deciding whether to operate on patients with cruciate ligament insufficiency. The subject of the present study is a design shortcoming of the KT2000 that may falsify the measured results when the device is not correctly employed. A simple mechanical modification of the KT2000 can reduce this error. In the present study, the error is quantified and we show how the modification can keep it within tolerable limits.

The implantation of tumour-endoprostheses is one of the major concepts in the treatment of musculo-skeletal tumours. Aseptic loosening which is often due to stress shielding meanwhile has become the most common mode of implant failure. in this study the influence of stem length and material on the strains of the bone stock was investigated. It was found that stem length is the major factor and the material of the stem is secondarily influencing the strains in periprosthetic bone.

Observation and perception errors in combination with lack: of attention explain the majority of all falls in skiing. This associates vision and vision deficiencies with safety aspects in skiing. The purpose of this study was to determine the effect of reduced visual acuity on the reaction time of a skier in safety-critical skiing situations.For this purpose, field experiments were conducted in the 1995/96 winter season. The subjects had to pass over a prepared ledge in the terrain and react to simulated obstacles, which were partly blocking the course. All experiments were video recorded, in total more than 220 trials were conducted. We tested three different types of obstacles: ice patches, a standing skier, and a skier just starting to move. Two experimental conditions were examined, normal visual acuity and a reduced visual acuity. The acuity reduction to 20% of normal was achieved by the use of special goggles. From the videotape, the subjects' time for an evasive action was determined and statistically analyzed.No significant change of the reaction time with reduced visual acuity could be seen for the bigger obstacles i.e., the standing skier and the moving skier. However, with the simulated ice patches, the increase of the reaction time was significant (p = 0.01) with an average increase of 35%. From the obtained results it is concluded that skiers not wearing their corrective lenses may feel safer than they really are. They can perceive larger, stationary, or moving objects, however they might not be aware of the risk from low-contrast obstacles.

Article Entwicklung einer Konussteckverbindung für modular aufgebaute Prothesensysteme aus Kohlenstoffaserverbundwerkstoff was published on January 1, 1998 in the journal Biomedical Engineering / Biomedizinische Technik (volume 43, issue s1).

For the investigation of the boot-induced anterior cruciate ligament injury an experimental case study with a prototype ski boot was performed. The back spoiler of this boot was designed to yield by only a few degrees when a certain level of backward moment was reached. A mechanic switch was used to activate or to block this mechanism. Over a prepared hill, a single subject performed ten jumps with an activated mechanism and ten jumps with a blocked spoiler mechanism in randomized order. During the jump and landing, an electromyograph (EMG) of eight lower extremity muscles was recorded and synchronized to two S-VHS cameras that were located for two-dimensional kinematic analysis. The goal of these experiments was to quantify the muscular and kinematic effects caused by the new spoiler characteristics and also to establish a method for their judgment.For the quantification of the muscular effects, an activity quotient was defined and, for the analysis of the kinematics, the time history of three body angles and their variation between the trials were found to be appropriate. The results of this case study revealed clear differences between the two treatments. In particular, the activity quotient of the hamstring muscles showed a remarkable increase with the spoiler mechanism activated. The findings encourage further investigations in this direction, for example, a randomized field study using the derived method.