[Oedipus, a traumatological - orthopaedic case? - Essay on an unfortunate figure from antiquity]. / Ödipus, ein traumatologisch - orthopädischer Fall?

This essay studies the physical shape, character and fate of Oedipus, applying relevant and current medical scientific criteria. The abuses he suffered during childhood play an important role in this context. The name Oedipus is usually translated as "swollen foot", but according to various etymological sources, the name can be interpreted in different ways. One of these interpretations alludes to fact that it was easy for the hero to solve the riddle of the sphinx because its key message addressed an orthopedic issue as it was dealing with the function of the feet. During Oedipus' life, he suffered many injuries and disorders, which can be classified using the current ICD code. There is, for example, his blindness after he had blinded himself. In addition, we can assume that Oedipus suffered from a post-traumatic stress disorder and a borderline personality disorder following the child abuse caused by his parents who intended to kill him. Thus, the discussion about his own responsibility for his actions is again being put into question. Oedipus`s life story is once again proof that Greek mythology can reflect the reality of life.

Tribometer for measuring coefficients of friction of uneven surfaces like articular cartilage.

To examine coefficients of friction (COFs) of articular cartilage, it is necessary to use cartilage as a friction partner. Irregularities of surfaces require special tribometers and calculation methods. The aim of this study was to establish a tribometer system for measuring a low COF of cartilage and to develop and validate an algorithm that takes the irregularities into consideration. We used a pin-on-plate tribometer that allows a vertical displacement of the pin to follow the surface of the plate and developed an algorithm that takes these irregularities into account. We were, thus, able to take into consideration a forward and backward movement, an upward and downward movement, and different force ratios. The algorithm was validated using a spherical POM (polyoxymethylene) pin against a stainless steel plate at slope angles up to 24°. First examinations with articular cartilage against articular cartilage samples of a stifle joint of a pig were then performed. The newly developed tribometer worked well when POM against a stainless steel hump was examined. The COF increased for slope angles steeper than ±15°. There was an interaction between the COF and the slope angle, but not for the range within ±15°. Cartilage examinations revealed COFs as published in the literature. The tribometer and the algorithm were suitable for the detection of low COF of irregular surfaces of the plate within a range of ±15°. The COF resulting from the forward and backward movements should be averaged.

Analysis of the osseointegrative force of a hyperhydrophilic and nanostructured surface refinement for TPS surfaces in a gap healing model with the Göttingen minipig.

BACKGROUND: A lot of advantages can result in a high wettability as well as a nanostructure at a titanium surface on bone implants. Thus, the aim of this study was to evaluate the osseointegrative potential of a titan plasma-sprayed (TPS) surface refinement by acid-etching with chromosulfuric acid. This results in a hyperhydrophilic surface with a nanostructure and an extreme high wetting rate. METHODS: In total, 72 dumbbell shape titan implants were inserted in the spongy bone of the femora of 18 Göttingen minipigs in a conservative gap model. Thirty-six titan implants were coated with a standard TPS surface and 36 with the hyperhydrophilic chromosulfuric acid (CSA) surface. After a healing period of 4, 8, and 12 weeks, the animals were killed. The chronological healing process was histomorphometrically analyzed. RESULTS: The de novo bone formation, represented by the bone area (BA), is increased by approximately 1.5 times after 12 weeks with little additional benefit by use of the CSA surface. The bone-to-implant contact (BIC), which represents osseoconductive forces, shows results with a highly increased osteoid production in the CSA implants beginning at 8 and 12 weeks compared to TPS. This culminates in a 17-fold increase in BIC after a healing period of 12 weeks. After 4 weeks, significantly more osteoid was seen in the gap as de novo formation in the CSA group (p = 0.0062). Osteoid was also found more frequently after 12 weeks at the CSA-treated surface (p = 0.0355). The site of implantation, intertrochanteric or intercondylar, may influence on the de novo bone formation in the gap. CONCLUSIONS: There is a benefit by the CSA surface treatment of the TPS layer for osseointegration over an observation time up to 12 weeks. Significant differences were able to be shown in two direct comparisons between the CSA and the TPS surface for osteoid formation in the gap model. Further trials may reveal the benefit of the CSA treatment of the TPS layer involving mechanical tests if possible.

Mechanical properties of mesh materials used for hernia repair and soft tissue augmentation.

BACKGROUND: Hernia repair is the most common surgical procedure in the world. Augmentation with synthetic meshes has gained importance in recent decades. Most of the published work about hernia meshes focuses on the surgical technique, outcome in terms of mortality and morbidity and the recurrence rate. Appropriate biomechanical and engineering terminology is frequently absent. Meshes are under continuous development but there is little knowledge in the public domain about their mechanical properties. In the presented experimental study we investigated the mechanical properties of several widely available meshes according to German Industrial Standards (DIN ISO). METHODOLOGY/PRINCIPAL FINDINGS: Six different meshes were assessed considering longitudinal and transverse direction in a uni-axial tensile test. Based on the force/displacement curve, the maximum force, breaking strain, and stiffness were computed. According to the maximum force the values were assigned to the groups weak and strong to determine a base for comparison. We discovered differences in the maximum force (11.1±6.4 to 100.9±9.4 N/cm), stiffness (0.3±0.1 to 4.6±0.5 N/mm), and breaking strain (150±6% to 340±20%) considering the direction of tension. CONCLUSIONS/SIGNIFICANCE: The measured stiffness and breaking strength vary widely among available mesh materials for hernia repair, and most of the materials show significant anisotropy in their mechanical behavior. Considering the forces present in the abdominal wall, our results suggest that some meshes should be implanted in an appropriate orientation, and that information regarding the directionality of their mechanical properties should be provided by the manufacturers.

An MR-compatible device for automated and safe application of laser stimuli in experiments employing nociceptive stimulation.

In this paper the establishment of an automatic laser application device that reproducibly delivers laser stimuli in a safe, controlled, and reliable manner is presented. Nociceptive stimulation is widely used in functional magnetic resonance imaging (fMRI) experiments and a number of different methods are employed. One major advantage of laser stimulation as a method to administer painful stimuli is that it selectively activates nociceptors. To avoid damage to the subject's skin, which might occur if the same skin area were stimulated too often, the laser focal spot needs to be repositioned after each stimulus. Here, we describe the design of the mechanical set-up, the functionality, the computation of laser stimulus intensity, the materials used, the monitoring system, and the interface to the control software. Additionally, MR-compatibility and functionality of the device were evaluated and assessed in a 3T MR scanner. Finally, the reliability and validity of the device were tested and demonstrated. It permits easy and investigator-independent use of laser stimulation in the MR scanner.

Effect of surface roughness, porosity, and a resorbable calcium phosphate coating on osseointegration of titanium in a minipig model.

The aim of this study was to compare the osseointegration of four different implant surfaces in the Göttingen minipig femur model. They were prepared by glasspearlblasting (A), sandblasting (B) and titaniumplasma spraying (C and D). Surface D received additionally an electrochemically deposited layer of a resorbable calcium phosphate (CaP) layer, made mainly of brushite. Sample size was n = 20 per group. Implants were placed in the intertrochanteric and intercondylar sites of both femora. After 12 weeks, implant anchorage was measured by the pull-out test and histomorphometry measurements were carried out at the bone-implant interface. Implant anchorage was 0.7 +/- 0.3 MPa for surface A, 3.2 +/- 0.6 MPa for surface B, 6.5 +/- 1.5 MPa for surface C and 7.3 +/- 1.9 MPa for surface D. The differences between surfaces were statistically significant, with exception of C and D. The stiffness of the bone-implant interface showed no statistically significant difference between surfaces. After pull-out, surface A and B showed nearly no bone spots, while on surfaces C and D bone remains were found. Bone-implant contact was 1.9 +/- 1.1% for surface A, 10.5 +/- 3.6% for surface B, 22.4 +/- 4.5% for surface C and 48.8 +/- 4.5% for surface D. The differences were statistically significant. Implant location, intertrochanteric and intercondylar, did not affect the data. In this minipig model, rougher surfaces showed better osseointegration. After 12 weeks of healing, the resorbable CaP layer enhanced significantly the bone-implant contact but not the level of anchorage. The findings also suggest that the pull-out test should be critically evaluated to determine the shear strength between bone and porous surfaces.

[The relation of workspace and installation space of epicyclic kinematics with six degrees of freedom]. / Das Verhältnis von Arbeitsraum zu Bauraum epizyklischer Kinematiken mit sechs Freiheitsgraden.

INTRODUCTION: The kinematics of a robotic device significantly determines its installation space when it comes to technical realisation. With regard to the deployment of robotic manipulators in surgery, manipulators with a preferably small installation space are needed. MATERIALS AND METHODS: This study describes six versions of novel epicyclic kinematics with six degrees of freedom (DOF). At first, the kinematics functionality was analysed using Gruebler's formula. Subsequently, the quantitative determination of the relation of workspace and installation space was performed using Matlab algorithms. To qualitatively describe the shape of the workspace, the Matlab visualisation features were utilised. For comparison, the well-known Hexapod was used. RESULTS: The assessed kinematics had 6-DOF-functionality. It became apparent that one version of the epicyclic kinematics having two 3-DOF disk systems mounted in a parallel way featured a particularly good relation of workspace and installation space. Compared to the Hexapod, this is approximately four times better. The shape of the workspaces of all epicyclic kinematics assessed was convex and compact. CONCLUSION: It could be shown that a novel epicyclic kinematics has a notably advantageous relation of workspace and installation space. Apparently, it seems to be well suited for the deployment in robotic machines for surgical procedures.

Accuracy of Ein Bild Röntgen Analyse in determining wear in total hip arthroplasty in vitro.

The Ein Bild Röntgen Analyse system is used to radiographically measure femoral head penetration in total hip replacement components. Because determining the accuracy of any wear analysis system is more precise and comparable under in vitro conditions, we used a femoral head migration simulator to assess the accuracy of Ein Bild Röntgen Analyse and determine the effect of magnification factors on accuracy. We used onscreen magnifications of 100% and 200% to measure anteroposterior radiographs, which improved the accuracy of determining femoral head penetration. Improvements averaged 0.056 mm (95% CI +/- 0.013 mm) in the X direction and 0.024 mm (95% CI +/- 0.027 mm) in the Y direction. Femoral head penetration was simulated in 0.25-mm steps from 0-1 mm. Accuracy ranged from 0-0.029 mm (95% CI, 0.035-0.067 mm) for the X direction and from 0.001-0.013 mm (95% CI, 0.046-0.079 mm) for the Y direction. Assuming the worst accuracy combined for the X and Y directions, Ein Bild Röntgen Analyse can accurately detect femoral head penetration greater than 0.128 mm. These results are comparable with reported accuracy values for different systems and suggest that magnification tools should be considered with Ein Bild Röntgen Analyse when measuring wear radiographically.

Today's state of the art in surgical robotics*.

OBJECTIVE: This paper describes the current level of development of robots for surgery. MATERIAL AND METHODS: This paper is based on a literature search in Pubmed, IEEExplore, CiteSeer and the abstract volumes of the MICCAI 2002, 2003 and 2004, CARS 2003 and 2004, CAOS 2003 and 2004, CURAC 2003 and 2004 and MRNV 2004 meetings. RESULTS: Divided into different disciplines (imaging, abdominal and thoracic surgery, ENT, OMS, neurosurgery, orthopaedic surgery, radiosurgery, trauma surgery, urology), 159 robot systems are introduced. Their functionality, deployment, origin and mechanical set-up are described. Additional contacts and internet links are listed. CONCLUSIONS: The systems perform diverse tasks such as milling cavities in bone, harvesting skin, screwing pedicles or irradiating tumors. From a technical perspective the strong specialization of the systems stands out. Most of the systems are being developed in Germany, the United States, Japan or France.

Validation of a diffusion chamber as in vitro system for the analysis of compound diffusibility through cartilage tissue.

The validation of a diffusion chamber comprising a donor and a receptor side separated by a cartilage membrane was undertaken according to the basic principles described by Peng et al. (1998). The study had three targets: first to evaluate the chamber as in vitro system by the examination of the diffusibility of compound through bovine cartilage samples; second the analysis of the affinity of compound (RS-130830) to cartilage; third to test the influence of two pre-incubation periods (one or three nights) of the cartilage samples. The validation of the chamber as in vitro system for the analysis of compound diffusibility and affinity to cartilage was performed using membrane slices of fresh bovine cartilage and a hydroxamic acid derivative (RS-130830) known as matrix metalloproteinase inhibitor (MMPI). The influence of the pre-incubation of cartilage was also examined. Compound concentrations in donor, receptor and membrane were determined by high performance liquid chromatography-mass spectrometry (HPLC-MS). Diffusion could be demonstrated after 6 h and finally 24 h incubation: the compound concentration in the receptor increased from 0 to 35 microM (mean) while it decreased in the donor from 200 to 144 microM (mean). We also found compound in the cartilage membrane (approximately 1.2 nmol (mean)). Pre-incubation of cartilage samples in culture buffer is suitable as a storage procedure, since the results on the donor side only were influenced significantly but not for the receptor and the cartilage affinity. Thus, the system could clearly reflect relevant properties of the tested compound with regard to its diffusibility and affinity to cartilage tissue.