Design and calibration of load sensing orthopaedic implants

Contact forces and moments act on orthopaedic implants such as joint replacements. The three forces and three moment components can be measured by six internal strain gauges and wireless telemetric data transmission. The accuracy of instrumented implants is restricted by their small size, varying modes of load transfer, and the accuracy of calibration. Aims of this study were to test with finite element studies design features to improve the accuracy, to develop simple but accurate calibration arrangements, and to select the best mathematical method for calculating the calibration constants. Several instrumented implants, and commercial and test transducers were calibrated using different loading setups and mathematical methods. It was found that the arrangement of flexible elements such as bellows or notches between the areas of load transfer and the central sensor locations is most effective to improve the accuracy. Increasing the rigidity of the implant areas, which are fixed in bones or articulate against joint surfaces, is less effective. Simple but accurate calibration of the six force and moment components can be achieved by applying eccentric forces instead of central forces and pure moments. Three different methods for calculating the measuring constants proved to be equally well suited. Employing these improvements makes it possible to keep the average measuring errors of many instrumented implants below 1-2% of the calibration ranges, including cross talk. Additional errors caused by noise of the transmitted signals can be reduced by filtering if this is permitted by the sampling rate and the required frequency content of the loads.

[Loads acting on orthopaedic implants. Measurements and practical applications]

The loads measured at instrumented joint replacements and other orthopaedic implants allow the optimization of their stability, wear properties, fixation stability and kinematic properties prior to clinical applications. The data obtained also indicate which activities cause very high loads and should be avoided by the patients in order not to endanger the long-term success of the implant. In addition, physiotherapy after joint arthroplasty and fractures can be further improved on the basis of these data. The technical principles for such measurements are summarized and examples for the design of load measuring instrumented implants are presented. The most important results are presented based on the measurements taken at the hip and shoulder joints, internal spinal fixation devices, vertebral body replacements and knee joints. Using this data, many practical conclusions are drawn. Due to the huge amount of data obtained from the hip, most practical advise can be provided to patients with replacement or disorders involving this joint.

Creatine improves health and survival of mice

The supplementation of creatine (Cr) has a marked neuroprotective effect in mouse models of neurodegenerative diseases. This has been assigned to the known bioenergetic, anti-apoptotic, anti-excitotoxic, and anti-oxidant properties of Cr. As aging and neurodegeneration share pathophysiological pathways, we investigated the effect of oral Cr supplementation on aging in 162 aged C57Bl/6J mice. Outcome variables included "healthy" life span, neurobehavioral phenotyping, as well as morphology, biochemistry, and expression profiling from brain. The median healthy life span of Cr-fed mice was 9% higher than in control mice, and they performed significantly better in neurobehavioral tests. In brains of Cr-treated mice, there was a trend towards a reduction of reactive oxygen species and significantly lower accumulation of the "aging pigment" lipofuscin. Expression profiling showed an upregulation of genes implicated in neuronal growth, neuroprotection, and learning. These data show that Cr improves health and longevity in mice. Cr may be a promising food supplement to promote healthy human aging.

In vivo glenohumeral contact forces—Measurements in the first patient 7 months postoperatively

Knowledge of forces in the glenohumeral joint is essential for understanding normal and pathologic shoulder function. It forms the basis for performing fracture treatment or joint replacement surgery, for optimizing implant design and fixation and for improving and verifying analytical biomechanical models of the shoulder. An instrumented shoulder implant with telemetric data transmission was developed to measure six components of joint contact forces and moments. A patient with humeral head arthrosis achieved good joint function after its implantation. During the first 7 postoperative months, the contact force remained below 100% BW (percent body weight) for most activities of daily living. It ranged up to 130% BW for arm positions close to the limits of motion or when acting against external resistance. When the patient tried to turn a blocked steering wheel with maximum effort, the force rose to about 150% BW, the highest level observed thus far. Of great interest were the force directions relative to the humerus, especially those in the sagittal plane, which were not greatly influenced by the type of exercise, the arm position or the external resistance. The moments due to friction in the joint reached 5.2 Nm. The friction-induced shift of contact forces relative to the implant head centre ranged up to 6.3mm. These first worldwide in vivo measurements of glenohumeral contact forces are being continued in more patients and for longer postoperative times.

Creatine supplementation in Parkinson disease: a placebo-controlled randomized pilot trial

Mitochondrial dysfunction plays a major role in the pathogenesis of Parkinson disease (PD). Creatine (Cr) is an ergogenic compound that exerts neuroprotective effects in animal models of PD. We conducted a 2-year placebo-controlled randomized clinical trial on the effect of Cr in 60 patients with PD. Cr improved patient mood and led to a smaller dose increase of dopaminergic therapy but had no effect on overall Unified Parkinson's Disease Rating Scale scores or dopamine transporter SPECT.

Acetic acid-guided biopsies after magnifying endoscopy compared with random biopsies in the detection of Barrett's esophagus: a prospective randomized trial with crossover design

BACKGROUND

In contrast to standard video endoscopy, magnifying endoscopy after local acetic acid application enables recognition of mucosal surface architecture.

OBJECTIVE

To investigate the diagnostic yield of magnifying endoscopy with acetic acid-targeted biopsies compared to random, 4-quadrant biopsies.

DESIGN

Prospective randomized trial (ratio 1:1) with crossover design.

SETTING

Two referral hospitals in Germany.

PATIENTS

Thirty-one patients with Barrett's esophagus or visible columnar-lined lower esophagus.

INTERVENTIONS

Patients were randomized to undergo either standard video endoscopy with 4-quadrant biopsies or magnifying endoscopy in conjunction with acetic acid application. All patients were re-examined 14 days after the initial endoscopy with the corresponding procedure.

MAIN OUTCOME MEASUREMENTS

Primary outcome analysis (per protocol and per biopsy) was the histological proof of Barrett's epithelium. Secondary outcome analysis was the correlation between the surface architecture and the presence of Barrett's epithelium and the needed number of biopsies to confirm Barrett's epithelium for the 2 different procedures.

RESULTS

Magnifying endoscopy enabled the prediction of Barrett's epithelium with a sensitivity of 100% and a specificity of 66%, respectively (accuracy 83.8%). Acetic acid-guided biopsies obtained a significantly higher percentage of tissues containing SCE (78%; 188/241) compared to random biopsies (57%; 159/280).

LIMITATIONS

No data on the diagnosis of Barrett's dysplasia.

CONCLUSION

Magnifying endoscopy with acetic acid-guided biopsies is superior to standard video endoscopy with random biopsies, and the number of biopsies needed to confirm Barrett's epithelium is half as much when compared to random biopsies.

Diversity oriented synthesis: a challenge for synthetic chemists

This article covers the diversity-oriented synthesis (DOS) of small molecules in order to generate a collection of pure compounds that are attractive for lead generation in a phenotypic, high-throughput screening approach useful for chemical genetics and drug discovery programmes. Nature synthesizes a rich structural diversity of small molecules, however, unfortunately, there are some disadvantages with using natural product sources for diverse small-molecule discovery. Nevertheless we have a lot to learn from nature. The efficient chemical synthesis of structural diversity (and complexity) is the aim of DOS. Highlights of this article include a discussion of nature's and synthetic chemists' strategies to obtain structural diversity and an analysis of molecular descriptors used to classify compounds. The assessment of how successful one diversity-oriented synthesis is vs another is subjective; therefore we use freely available software (www.cheminformatics.org/diversity) to assess structural diversity in any combinatorial synthesis.

Die Trainierbarkeit von propriozeptiven und koordinativen Parametern bei der chronisch-funktionellen Sprunggelenkinstabilität

AIM

This study was aimed at assessing the outcome of physical therapy based on both subjective patient's satisfaction and objective measurement of peroneal reaction time in patients with chronic ankle instability.

METHOD

25 patients with chronic ankle instability based on functional deficits were included. Physical therapy consisted in a 6 weeklong program with muscle strengthening and coordination exercises for one hour, three times a week. Before starting physical therapy as well as two weeks after finishing the program, patients underwent both a clinical exam as well as measurement of their peroneal reaction time.

RESULTS

Following physical therapy peroneal reaction time of the long (p = 0.0001) and short (p = 0.0003) peroneal muscles significantly decreased. Prior to physical therapy the Kitaoka score was calculated to be 72.2 (+/- 18.7), the post treatment value was 93.3 (+/- 11.7) with a p-value of < 0.001. As for subjective patient's assessment on a scale of 1-10 with 1 being the least and 10 the most satisfied with therapeutical outcome, patients gave an average post treatment score of 8.3 (+/- 1.9).

CONCLUSION

Measurement of PRT can be used as a helpful diagnostic parameter, as a parameter for quality control and for verification of therapy results. Specific physiotherapy leads to good clinical results and increased PRT.

Severe tick borne encephalitis with simultaneous brain stem, bithalamic, and spinal cord involvement documented by MRI

A case of tick borne encephalitis (TBE) is reported, with simultaneous brain stem, spinal cord, and bilateral thalamic involvement confirmed by magnetic resonance imaging (MRI). After exposure to a TBE endemic region, the patient developed a biphasic clinical course with initial flu-like symptoms followed by a severe brain stem syndrome. The diagnosis of TBE was confirmed serologically. Repeated MRI scans showed brain stem, bithalamic, and spinal cord involvement. The outcome was favourable. TBE cases with concomitant myelitis tend to have a more severe clinical course and more likelihood of needing intensive care support. They should therefore be identified early in order to be prepared for life threatening respiratory complications.

Changes in cognitive function after neuronal cell transplantation for basal ganglia stroke

Reported is the change in cognitive function after neuronal cell transplantation as a treatment for basal ganglia stroke. Nine subjects (two controls, seven transplants), all over 2 years post stroke, completed a comprehensive neuropsychological test battery prior to and 6 months after treatment. Four transplanted subjects who had strokes in the nondominant hemisphere showed marked improvement on the Rey Complex Figure, a test of visuospatial/constructional ability and nonverbal memory.