Osteoinduction and -conduction through absorbable bone substitute materials based on calcium sulfate: in vivo biological behavior in a rabbit model.

Calcium sulfate (CS) can be used as an antibiotically impregnated bone substitute in a variety of clinical constellations. Antibiotically loaded bone substitutes find specific application in orthopedic and trauma surgery to prevent or treat bone infections especially in relation to open bone defects. However, its use as a structural bone graft reveals some concerns due to its fast biodegradation. The addition of calcium carbonate and tripalmitin makes CS formulations more resistant to resorption leaving bone time to form during a prolonged degradation process. The aim of the present study was the evaluation of biocompatibility and degradation properties of newly formulated antibiotically impregnated CS preparations. Three different types of CS bone substitute beads were implanted into the tibial metaphysis of rabbits (CS dihydrate with tripalmitin, containing gentamicin (Group A) or vancomycin (Group B); Group C: tobramycin-loaded CS hemihydrate). Examinations were performed by means of x-ray, micro-computed tomography (micro-CT) and histology after 4, 6, 8 and 12 weeks. Regarding biocompatibility of the formulations, no adverse reactions were observed. Histology showed formation of vital bone cells attached directly to the implanted materials, while no cytotoxic effect in the surrounding of the beads was detected. All CS preparations showed osteogenesis associated to implanted material. Osteoblasts attached directly to the implant surface and revealed osteoid production, osteocytes were found in newly mineralized bone. Group C implants (Osteoset®) were subject to quick degradation within 4 weeks, after 6-8 weeks there were only minor remnants with little osteogenesis demonstrated by histological investigations. Group A implants (Herafill®-G) revealed similar degradation within atleast 12 weeks. In contrast, group B implants (CaSO4-V) were still detectable after 12 weeks with the presence of implant-associated osteogenesis atlatest follow-up. In all of these preparations, giant cells were found during implant degradation on surface and inside of resorption lacunae. None of the analyzed CS preparations triggered contact activation. All implants demonstrated excellent biocompatibility, with implants of Group A and B showing excellent features as osteoconductive and -inductive scaffolds able to improve mechanical stability.

Antimicrobial Formulations of Absorbable Bone Substitute Materials as Drug Carriers Based on Calcium Sulfate.

Substitution of bones is a well-established, necessary procedure to treat bone defects in trauma and orthopedic surgeries. For prevention or treatment of perioperative infection, the implantation of resorbable bone substitute materials carrying antibiotics is a necessary treatment. In this study, we investigated the newly formulated calcium-based resorbable bone substitute materials containing either gentamicin (CaSO4-G [Herafill-G]), vancomycin (CaSO4-V), or tobramycin (Osteoset). We characterized the released antibiotic concentration per unit. Bone substitute materials were implanted in bones of rabbits via a standardized surgical procedure. Clinical parameters and levels of the antibiotic-releasing materials in serum were determined. Local concentrations of antibiotics were measured using antimicrobial tests of bone tissue. Aminoglycoside release kinetics in vitro per square millimeter of bead surface showed the most prolonged release for gentamicin, followed by vancomycin and, with the fastest release, tobramycin. In vivo level in serum detected over 28 days was highest for gentamicin at 0.42 µg/ml, followed by vancomycin at 0.11 µg/ml and tobramycin at 0.04 µg/ml. The clinical parameters indicated high biocompatibility for materials used. None of the rabbits subjected to the procedure showed any adverse reaction. The highest availability of antibiotics at 14.8 µg/g on day 1 in the cortical tibia ex vivo was demonstrated for gentamicin, decreasing within 14 days. In the medulla, vancomycin showed a high level at 444 µg/g on day 1, decreasing continuously over 14 days, whereas gentamicin decreased faster within the initial 3 days. The compared antibiotic formulations varied significantly in release kinetics in serum as well as locally in medulla and cortex.

New Method for Monitoring Partial Weight Bearing (PWB) of Outpatients with an Independent Insole Sensor System.

UNLABELLED: PURPOSE OF THE STUDY Partial weight bearing (PWB) is commonly prescribed post operatively following lower limb fractures and compliance with the weight bearing protocol is an essential element of the rehabilitation. So far it is unknown to what extent patients do comply with PWB during the healing process as instructed by the surgeon. Our aim is to assess a new device for real-time feedback and long-term measurement of PWB of outpatients. The device offers the possibility to monitor the outpatient's activity. The applicability, reliability and validity of the new device should be evaluated. MATERIAL AND METHODS 20 young, healthy subjects complete a course of 500 m that contained several stairs, with a PWB of 15 kg. During the entire test, the axial load, the acceleration and the temperature were measured with a novel insole sensor system. The results were compared with reference measurements performed with a force plate. RESULTS Altogether, the 20 subjects performed 11,106 steps during the completion of the walking circuit. In 23.6% of the steps, the subjects applied a PWB of 10 to 20 kg. In 5.5% of all steps, PWB was superior to 60 kg. The mean bias of the insole was 11,58 N. Limits of agreement were +/- 125 N and the interclass correlation coefficient was r = 0.945. CONCLUSIONS The presented sensor sole might be a useful tool to obtain more precise insight of outpatients' activity and load to the injured limb during the healing process. Furthermore, these results demonstrate that even young and healthy subjects are not able to keep the prescribed PWB. This raises the question, if patients who have been recently operated are able to follow the instructions concerning the PWB. KEY WORDS: partial weight bearing (PWB), insole sensor system, sensor sole, monitoring, outpatients.

[Traumatic elbow dislocations in bouldering]. / Ellenbogenluxationsverletzungen beim Trendsport Bouldern.

Bouldering is a new trend sport which has become popular in recent years. From April 2011 to June 2012 a total of 5 patients with elbow dislocations from bouldering were admitted to our level 1 trauma center. The injuries varied from simple elbow dislocations to complex fracture dislocations. Elbow dislocations occurred during falling backwards when patients tried to protect themselves by retroversion of both arms. In all cases the falling height was less than 4 meters. The bouldering injury pattern, the diagnostic and therapeutic management as well as the rehabilitation program are described in detail in this article. To the best of our knowledge this is the first report on the special danger of bouldering for complex elbow injuries.

[Memento mori: what can be learned from early paintings and woodcuts about death and dying in former times?]. / Memento mori: Was lehren die alten Abbildungen über das Sterben in früheren Zeiten?

What was the impression on death and dying from people living in the 15th century? To answer this question written information is rare on this topic, as few people were able to read at that time, but paintings and early woodcuts may be helpful. Danses macabres (Totentänze) could be seen in Tallinn (formerly Reval), Lübeck, Bern and other places: parts of the original dance macabre still exist in Tallinn, but those in Bern and Lübeck are destroyed; copies however may give a decent impression of their former appearance. At all these dances macabre the death invites persons for a dance: the pope, the Kaiser, the king, the queen, various noblemen and citizens, even young women and small children; to dance with the death meant to die. The death does not dance with any old person. At the time of these dances macabre epidemics and famines were frequent causes of untimely early death.--A booklet Ars moriendi was published about 1470 and taught people how to behave at their hour of death; various devils appear at the deathbed haggling for the soul of the dying person. Thereafter an angel convinces him to trust in god and to resist those false promises of the devil.Nowadays dying is quite different. Usually persons die at very old age and are frequently demented, they die in hospitals, even in intensive care units and possibly without attendance of family members. They may have suffered for a long time and have spent years in nursing homes. Today dying may be just a release from very long suffering.

[Cases from the area between geriatrics and trauma surgery. Examples from the medical arbitration board]. / Fälle aus dem Grenzgebiet zwischen Geriatrie und Unfallchirurgie. Aus der Arbeit der Schlichtungsstelle.

Medical arbitration boards ("Schlichtungsstellen", expert panels for extrajudicial malpractice claim resolution) try to settle claims of suspected malpractice between patients and their physicians and to avoid court trials. Numerous studies found an increasing incidence of adverse events with rising age. Injuries that occur in the hospital are frequently beyond the specialty of the treating physician. Therefore, the physician has to broaden his diagnostic view beyond the borders of his own specialty to recognize injuries in his patients and to prevent malpractice claims.In this paper, we report on adverse events in elderly patients where the geriatrician/internist was accused of negligence for not having promptly recognized a fracture after a fall or having chosen an inadequate operative procedure. For example, the importance of weight bearing osteosynthesis, mandatory in hip fractures in the elderly population to prevent long-term immobilization, is discussed.Adverse events due to negligence are more frequent among the elderly; the reasons are discussed. They will never be entirely preventable. The data presented in this report may be helpful to recognize fractures in time and to ensure adequate treatment, in order to reduce the number of court claims.

Thermomagnetic convection in a ferrofluid layer exposed to a time-periodic magnetic field.

We have investigated the influence of a time-periodic and spatially homogeneous magnetic field on the linear stability properties and on the nonlinear response of a ferrofluid layer heated from below and from above. A competition between stabilizing thermal and viscous diffusion and destabilizing buoyancy and Kelvin forces occurs. Floquet theory is used to determine the stability boundaries of the motionless conductive state for a harmonic and subharmonic response. Full numerical simulations with a finite difference method were made to obtain nonlinear convective states. The effect of low- and high-frequency modulation on the stability boundaries as well as on the nonlinear oscillations that may occur is investigated.

Convection in binary fluid mixtures with modulated heating.

The response behavior of strongly nonlinear binary fluid convection to temporal modulation of the heating is investigated for the case of a negative Soret coupling between temperature and concentration gradients. Finite difference numerical simulations are performed for ethanol-water parameters subject to realistic boundary conditions. Traveling waves with modulated amplitudes and phase velocities, subharmonic standing waves, and synchronously modulated patterns with fixed spatial phase are found as stable solutions. The hysteretic transitions between subcritical traveling and standing waves that coexist bistably with the quiescent fluid state are investigated. Various diagnostic analysis tools are used to elucidate the complex spatiotemporal and bifurcation properties that are ultimately caused by nonlinear advection and mixing of concentration being very strong.

Stability of the circular Couette flow of a ferrofluid in an axial magnetic field: influence of polydispersity.

The gap between two concentric rotating cylinders is filled with a ferrofluid. A homogeneous magnetic field is applied parallel to the cylinder axis. The stability of the circular Couette flow is analyzed with different models that take into account the polydispersity of the ferrofluid to a varying degree. Their results are compared and their merits are discussed.

[Diagnosis and treatment of femural neck fractures from the beginning to operative treatment: a historical overview]. / Zur Geschichte von Diagnostik und Therapie hüftnaher Femurfrakturen bis zum Beginn der operativen Therapie : Ein historischer Uberblick.

Operative stabilisation of femural neck fractures is a routine procedure nowadays and is usually performed without delay. Treatment by osteosynthesis or endoprosthesis allows immediate mobilisation with at least partial weight bearing.Immobilisation for months, associated with high mortality as practiced in former times, is nearly forgotten. We present a review on 430 years of diagnosis and treatment of these fractures since the first description by Ambroise Paré. In fact, it took 150 years to recognise the different locations of various hip fractures; at the time, fractures close to the caput were felt to have no chance of healing. Impacted fractures of the femural neck were first described 250 years after the first publication by A. Paré.This article also presents an overview on the development of various treatments to stabilise hip fractures: closed reduction and repositioning by internal rotation of the external rotated leg, positioning of the leg on the double inclined splint, different types of extension treatment and finally early operative procedures, when asepsis was established and fractures could be imaged by x-rays.

Bifurcation of standing waves into a pair of oppositely traveling waves with oscillating amplitudes caused by a three-mode interaction.

A flow state consisting of two oppositely traveling waves (TWs) with oscillating amplitudes has been found in the counter-rotating Taylor-Couette system by full numerical simulations. This structure bifurcates out of axially standing waves that are nonlinear superpositions of left- and right-handed spiral vortex waves with equal time-independent amplitudes. Beyond a critical driving, the two spiral TW modes start to oscillate in counterphase due to a Hopf bifurcation. The trigger for this bifurcation is provided by a nonlinearly excited mode of different symmetry than the spiral TWs. A three-mode coupled amplitude equation model is presented that captures this bifurcation scenario. The mode-coupling between two symmetry degenerate critical modes and a nonlinearly excited one that is contained in the model can be expected to occur in other structure-forming systems as well.

Wave-number dependence of the transitions between traveling and standing vortex waves and their mixed states in the Taylor-Couette system.

Previous numerical investigations of the stability and bifurcation properties of different nonlinear combination structures of spiral vortices in a counter-rotating Taylor-Couette system that were done for fixed axial wavelengths are supplemented by exploring the dependence of the vortex phenomena waves on their wavelength. This yields information about the experimental and numerical accessibility of the various bifurcation scenarios. Also backward bifurcating standing waves with oscillating amplitudes of the constituent traveling waves are found.

Thermal convection in mixtures with an inversion of the separation ratio.

We have numerically investigated Rayleigh-Bénard convection in binary mixtures assuming a thermal diffusion ratio that depends on the local temperature and changes its sign within the cell. The stationary instability has been found to precede the oscillatory one for a wide range of negative mean psi values. The bifurcation diagram for stationary rolls turns out to be qualitatively different from that for constant Soret effect. Nevertheless, it can be mapped onto this special case by using a scaling argument, taking into account the fact that for small convection amplitudes the rolls are restricted to parts of the cell where the sign of the Soret coefficient favors instability.

Convection patterns in colloidal solutions.

We investigate the bifurcation properties and pattern selection in Rayleigh-Bénard convecting binary mixtures for parameter combinations that are typical for colloidal fluids using the Galerkin method. In such fluids the typical Lewis numbers and separation ratios differ by orders of magnitude from the values found in molecular mixtures like alcohol/water. We study stationary rolls, square and crossroll patterns for positive separation ratios, and traveling waves for negative separation ratios. Results are compared to those for molecular mixtures.

Controlling the stability transfer between oppositely traveling waves and standing waves by inversion-symmetry-breaking perturbations.

The effect of an externally applied flow on symmetry degenerated waves propagating into opposite directions and standing waves that exchange stability with the traveling waves via mixed states is analyzed. Wave structures that consist of spiral vortices in the counter rotating Taylor-Couette system are investigated by full numerical simulations and explained quantitatively by amplitude equations containing quintic coupling terms. The latter are appropriate to describe the influence of inversion-symmetry-breaking perturbations on many oscillatory instabilities with O(2) symmetry.

Computer tomographically determined design parameters for optimized fit of an acetabular reconstruction cage.

PURPOSE OF THE STUDY: Reinforcement rings are widely used for treatment of large acetabular defects but significant migration due to a lack of implant integration into the bone is a common problem. Although insufficient congruence between implant and acetabular bone has been identified main factor in early implant loosening, there are no reconstruction ring design parameters based upon anatomical data of the pelvis available. MATERIAL: In this study such parameters were calculated on the basis of standardized computer tomograms of the hip region of 10 male and 10 female patients (40 data sets). METHODS: The center of rotation, the acetabular entrance plane and the geometry of a simulated cranial and caudal flange of a reconstruction ring were determined. The flanges geometry was defined by the angles between the flanges and the entrance plane, the angle between the flange projections onto the entrance plane, the torsion and the width of each flange depending on the distance to the center of rotation, and the flanges torsion and width at their origin at the acetabular circumference. RESULTS: An optimal alignment between reconstruction ring and the periacetabular bone could be achieved with a medial angulation of 19.9 degrees +/- 19.4 degrees of the cranial and 14.7 degrees +/- 7.1 degrees of the caudal flange against the entrance plane. The angle between the flanges projections onto the entrance plane was calculated to be 162.2 degrees +/- 6.4 degrees . At its origin from the acetabular circumference the cranial flange is twisted 28.5 degrees , the caudal flange -0.8 degrees against the entrance plane. The maximal flanges widths were calculated to 21-54 mm for the cranial and 22-25 mm for the caudal flange depending on the distance from the acetabular circumference. DISCUSSION & CONCLUSION: The given design parameters may result in optimized implants respecting the pelvic anatomy and possibly providing improved fixation.

Driving convection in a fluid layer by a temperature gradient or a heat current.

Bifurcation properties, stability behavior, dynamics, and the heat transfer of convection in a horizontal fluid layer that is driven away from thermal equilibrium by imposing a vertical temperature difference are compared with those resulting from imposing a heat current. Similarities and differences are elucidated. In particular various paradigmatic backwards bifurcating convection structures that occur, e.g., in binary fluid mixtures are determined numerically for the two different driving mechanisms. Conditions are given under which current driven convection is stable when temperature driven convection is unstable.

Measuring the transverse magnetization of rotating ferrofluids.

We report on measurements of the transverse magnetization of a ferrofluid rotating as a rigid body in a constant magnetic field, H0, applied perpendicular to the axis of rotation. The rotation of the fluid leads to a nonequilibrium situation, where the ferrofluid magnetization M and the magnetic field within the sample, H, are no longer parallel to each other. The off-axis magnetization perpendicular to H0 is measured as a function of both the applied magnetic field H0 and the angular frequency Omega. The latter ranges from a few hertz to frequencies well above a characteristic inverse Brownian relaxation time. Our experimental results strongly indicate that the transverse magnetization is caused only by a small fraction of the colloidal ferromagnetic particles. The effect of the polydispersity of the ferrofluid is discussed. Experimental results are compared to predictions based on several theoretical models. A single-time relaxation approach for the so-called effective field and a field-dependent Debye relaxation of M yield reasonably good shapes of the curves of transverse magnetization vs Omega. However, like the other models, they overestimate their magnitudes.

In vivo quantification of gentamicin released from an implant coating.

Drug-releasing implants are gaining increasing interest. The present study reports a detailed physicochemical analysis of a polymeric coating based on poly(D,L-lactide) and the incorporated gentamicin combined with an in vitro and in vivo study of the gentamicin release. Differential scanning calorimeter, Fourier transform infrared spectroscopy, gel permeation chromatography and high-performance liquid chromatography showed no effect of the gamma sterilisation on the coating components or an interaction of the polymer and the gentamicin. Microbiological analysis revealed an inhibition of bacterial growth on the implant surface. For the in vivo study, gentamicin-coated wires were implanted into the tibiae of rats and harvested at different time points up to day 42. To monitor the release in vivo, gentamicin was quantified in serum, bone, endosteum, kidney, and on the explanted wires. Gentamicin was detectable over a time period of 42 days in the endosteum, up to seven days in the kidney, up to 4 h in the bone and at the end of the experiment on one of eight wires. The locally released gentamicin caused no histological changes of the kidney. Microbiologically active concentrations of released gentamicin were found in the endosteum up to 4 h after implantation. The combination of different methods supports the individual results, where quantification is complemented by visualisation or antimicrobial activity. This work demonstrates that the coating procedure results in no substantial alteration of the incorporated drug and that the in vitro burst release occurs also in vivo.

Systemic versus local application of gentamicin in prophylaxis of implant-related osteomyelitis in a rat model.

Administration of perioperative antibiotic prophylaxis is a routine procedure in orthopedic surgery. Besides systemic prophylaxis, only few techniques are established for local application of antibiotics to reduce infection related to orthopedic implants. The aim of this study was to evaluate the efficacy of locally versus systemically applied gentamicin in a rat model (n = 60). For local application, the antibiotic was delivered from a biodegradable poly(D,L-lactide) (PDLLA) coating of titanium implants. The efficacy of local prophylaxis was compared to a systemic single shot application of gentamicin as well as a combination of both administrations. Half of the animals received a weight-adopted single shot application of gentamicin 30 min prior to surgery. At surgery, the medullary cavities of the tibiae were contaminated with Staphylococcus aureus (10(2) colony forming units /CFU) and titanium Kirschner wires were implanted into the medullary canals. The implants were either uncoated, PDLLA coated, or coated with PDLLA + 10% w/w gentamicin. The animals were followed up for 42 days. X-ray examinations were performed; body weight, temperature, and the clinical condition were determined. After sacrifice, infection was evaluated by histological and microbiological analysis. All animals treated with uncoated or PDLLA-coated Kirschner wires without systemic application of the antibiotic developed osteomyelitis and all cultures of implants were tested positive on S. aureus. Implant-related osteomyelitis could be prevented by prophylaxis of systemically applied gentamicin in 15% of animals. In contrast, local application of gentamicin delivered from a PDLLA coating was more effective. Onset of infection could be prevented in 90% of animals treated with gentamicin coated Kirschner wires, and in 80% of the animals that were treated with a combination of local and systemic application. The local application from PDLLA-coated implants might support systemic antibiotic prophylaxis in preventing implant-associated osteomyelitis.