Wearable sensor-based measures of step-up transfers are supplementary to patient-reported outcome measures following total joint arthroplasty

PURPOSE

This study investigated the longitudinal assessment of step-up performance in patients undergoing total joint arthroplasty (TJA) and correlation with subjective patient reported outcome measures (PROMs).

METHODS

In this sub-analysis of the ADAPT study, PROMs were assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Block step-up (BS) transfers were assessed by wearable-derived measures of time. 76 patients undergoing TJA were included. Subgroups were formed isolating the worst performing quartile (low functioning (LF)) from the high functioning (HF), and outcomes were compared.

RESULTS

One-year post-surgery, WOMAC function demonstrated strong correlations to WOMAC pain (Pearson's r = 0.67-0.84) and moderate correlations to BS performance (Pearson's r = 0.31-0.54). Both WOMAC and BS significantly improved with a larger effect size for the HF subgroup (0.62 vs. 0.43; p < 0.05). Patients designated to the LF subgroup at 3 months had increased odds of representing the LF subgroup at 12 months (WOMAC = 19; BS = 4). WOMAC defined 18 LF patients at 12 months follow-up. BS performance identified 9 additional LF patients.

CONCLUSIONS

WOMAC function scores seem pain dominated. Measures of BS performance allow assessment of otherwise hidden residual functional impairment. Lower functioning 3 months post-surgery is predictive of longer-term impairment.

Outcome of revised metal-on-metal hip arthroplasties: a Dutch arthroplasty register study

BACKGROUND

Preliminary results of metal-on-metal (MoM) hip arthroplasty were satisfactory, but since 2004 data showed high failure rates. National joint replacement registries are multi-centre databases comprised of thousands of subjects and implants which allow for identifying variables predictive of implant failure. The aim of the current study was to estimate re-revision rates after revision of a primary MoM hip arthroplasty in the Dutch Arthroplasty Register (LROI) and to assess potential predictor variables of re-revision of these MoM hip arthroplasties.

METHODS

Eligible procedures were those with a revision for any reason except infection, after an initial primary surgery with a hip resurfacing (HRA) or large-head MoM (LH-MoM) total hip arthroplasty (THA). The probability of re-revision for both types of MoM hip arthroplasty over time was estimated using the cumulative incidence function taking mortality as a competing risk into account. A proportional sub-distribution hazards regression model was used to assess potential predictor variables of re-revision of these MoM hip arthroplasties.

RESULTS

A total of 3476 records of revised implants were included, of which 873 (25.2%) were MoM implants. Over the course of follow-up, 101 (11.5%) MoM implants were re-revised. During follow-up 36 (4.3%) patients who received a MoM-implant at primary arthroplasty and a revision afterwards had died. The regression model showed that for primary MoM implants a MoM articulation after revision (HR 2.48; 95% CI 1.53-4.03, p < 0.001), femoral-only revisions (HR 3.20; 95% CI 2.06-4.99, p < 0.001) and periprosthetic fractures (HR 1.98; 95% CI 1.03-3.82, p = 0.042) as reason for the first revision were statistically significant risk factors for re-revision.

CONCLUSION

Both types of large-head MoM hip arthroplasties have shown high revision and re-revision rates; risk factors were identified. The outcome of this study can be helpful in managing expectations of patients and orthopaedic surgeons.

Prosthetic hip-associated cobalt toxicity: a systematic review of case series and case reports

Prosthetic hip-associated cobalt toxicity (PHACT) is caused by elevated blood cobalt concentrations after hip arthroplasty. The aim of this study is to determine which symptoms are reported most frequently and in what type of bearing. We also try to determine the blood level of cobalt concentrations associated with toxicological symptoms. A systematic review was conducted on the 10th of July according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A methodological quality assessment (risk of bias (RoB)) was performed. Primary outcomes were the reported symptoms of cobalt toxicity and the level of cobalt concentrations in blood. These levels were associated with toxicological symptoms. A total of 7645 references were found of which 67 relevant reports describing 79 patients. The two most used bearings in which PHACT was described were metal-on-metal (MoM) bearings (38 cases) and revised (fractured) ceramic-on-ceramic (CoC) bearings where the former ceramic head was replaced by a metal head (32 cases). Of all reported symptoms, most were seen in the neurological system, of which 24% were in the sensory system and 19.3% were in central/peripheral system, followed by the cardiovascular (22.1%) system. The mean cobalt concentration for MoM-bearings was 123.7 ± 96.8 ppb and 1078.2 ± 1267.5 ppb for the revised fractured CoC-bearings. We recommend not to use a metal-based articulation in the revision of a fractured CoC bearing and suggest close follow-up with yearly blood cobalt concentration controls in patients with a MoM bearing or a revised fractured CoC bearing. Level of Evidence: Level V, systematic review.

Satisfied patients after shoulder arthrodesis for brachial plexus lesions even after 20 years of follow-up

Purpose

Patients with an upper brachial plexus lesion can suffer from dysfunction, joint deformities and instability of the shoulder. The goal of this study was to determine pain, shoulder function, patient satisfaction and muscle strength in shoulder arthrodesis in patients with an upper brachial plexus lesion more than 15 years after surgery.

Methods

We retrospectively studied 12 patients with a brachial plexus lesion of mean age 46 years (27–61). At a mean of 19.8 years (15.4–30.3) after shoulder arthrodesis, patient-reported outcome measures (PROMs), range of motion (e.g., active and passive), patient satisfaction, strength of the affected and non-affected side (e.g., maximum isometric strength in Newton in forward and retroflexion, ab- and adduction, internal and external rotation) and position of fusion were obtained. PROMS consisted of the Visual Analogue Scale (VAS; 0–100, 0 being painless) for pain and the Disabilities of the Arm, Shoulder and Hand Score (DASH; 0–100, 0 being the best score) for function.

Results

At latest follow-up, the median VAS pain score was 49 (0–96) and 0 for, respectively, the affected and unaffected side. The DASH was 15 (8–46), meaning a reasonable to good function of the upper extremity. Active and passive retroflexion was significantly different (p = 0.028). All subjects stated that in the same situation they would undergo a shoulder arthrodesis again. The unaffected side was significantly stronger in every direction. Arthrodesis showed position of fusion of 31° (12–70) abduction, 20° (10–50) forward flexion and 22° (− 14 to 58) internal rotation. The unaffected side was significantly (p ≤ 0.05) stronger in every movement direction.

Conclusion

At a mean of 20 years after shoulder arthrodesis, patients with an upper brachial plexus lesion are still satisfied with a good to moderate functional improvement.

Level of evidence III

A retrospective cohort study.

Physical activity after outpatient surgery and enhanced recovery for total knee arthroplasty

PURPOSE AND HYPOTHESIS

The purpose of this study was to 'objectively' measure improvement of physical activity with the use of an activity monitor between patients who followed an enhanced recovery- or outpatient surgery pathway after total knee arthroplasty (TKA). It was hypothesized that both pathways will have comparable physical activity after TKA at 6-week follow-up.

METHODS

This prospective observational comparative case study was designed to investigate activity parameters (e.g. physical activity, number of steps, sit-stand transfers) of two different pathways after 6 weeks with the use of a non-invasive triaxial accelerometer activity monitor. This study included 20 patients with a mean age of 65.5 years (SD 6.1) undergoing TKA who were allocated to follow one of the two pathways: enhanced recovery (n = 10) or outpatient surgery (n = 10). Patients were monitored for 4 days pre-, 4 days during and 4 days after 5 weeks postoperatively. Patient-reported outcome measures (PROMs) and range of knee motion were obtained pre- and 6 weeks postoperatively.

RESULTS

The activity parameters recovered steeply during the first 4 postoperative days and continued to improve within both pathways (n.s.). Preoperative and during the first 4 days and 5 weeks postoperative, activity parameters were comparable (n.s.) between both pathways but did not reach preoperative levels of physical activity and range of motion (n.s.). PROMs improved within each pathway, and no difference between both pathways was observed (n.s.).

CONCLUSIONS

This study demonstrates that the early physical activity parameters of patients after TKA, following the outpatient surgery pathway, were similar to patients who followed the standard enhanced recovery pathway. The activity monitor is an added value for a more detailed and objective analysis of the physical performance in patients after TKA.

LEVEL OF EVIDENCE

III.

Cemented versus cementless hemiarthroplasty for a displaced fracture of the femoral neck: a systematic review and meta-analysis of current generation hip stems

AIMS

Our aim was to prepare a systematic review and meta-analysis to compare the outcomes of cemented and cementless hemiarthroplasty of the hip, in elderly patients with a fracture of the femoral neck, to investigate the mortality, complications, length of stay in hospital, blood loss, operating time and functional results.

MATERIALS AND METHODS

A systematic review and meta-analysis was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines on randomised controlled trials (RCTs), studying current generation designs of stem only. The synthesis of results was done of pooled data, with a fixed effects or random effects model, based on heterogeneity.

RESULTS

A total of five RCTs including 950 patients (950 hips) were included. Cementless stems were found to be associated with more complications compared with cemented stems (odds ratio (OR) 1.61, 95% confidence interval (CI) 1.12 to 2.31, p = 0.01), especially implant-related complications (OR 3.15, 95% CI 1.55 to 6.41, p = 0.002). The operating time was shorter for cementless stems (weighted mean difference -9.96 mins, 95%CI -12.93 to -6.98, p < 0.001). The data on functional outcomes could not be pooled. There was no statistically significant difference for any other outcome between the two methods of fixation.

CONCLUSION

In hemiarthroplasty of the hip using current generation stems, cemented stems result in fewer implant-related complications and similar mortality compared with cementless stems. Cite this article: Bone Joint J 2017;99-B:421-31.

Roles of Tetratricopeptide Repeat Proteins in Biogenesis of the Photosynthetic Apparatus

Biosynthesis of the photosynthetic apparatus is a complex operation, which includes the concerted synthesis and assembly of lipids, pigments and metal cofactors, and dozens of proteins. Research conducted in recent years has shown that these processes, as well as the stabilization and repair of this molecular machinery, are facilitated by transiently acting regulatory proteins, many of which belong to the superfamily of helical repeat proteins. Here, we focus on one of its families in photoautotrophic model organisms, the tetratricopeptide repeat (TPR) proteins, which participate in almost all of these steps and are crucial for biogenesis of the thylakoid membrane.

Assessment of physical function following total hip arthroplasty: Inertial sensor based gait analysis is supplementary to patient-reported outcome measures

BACKGROUND

Functional outcome assessment after total hip arthroplasty often involves subjective patient-reported outcome measures whereas analysis of gait is more objective. The study's aims were to compare subjective and objective functional outcomes after total hip arthroplasty between patients with low and high self-reported levels of pre-operative physical function.

METHODS

Patients undergoing total hip arthroplasty (n=36; m/f=18/18; mean age=63.9; SD=9.8 years; BMI=26.3; SD=3.5) were divided into a low and high function subgroup, and prospective measures of WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) function score and gait were compared at baseline and 3 and 12 months post-operatively.

FINDINGS

WOMAC function scores significantly improved in both low and high function subgroups at 3 months post-operatively whereas gait parameters only improved in patients with a low pre-operative function. Between 3 and 12 months post-operatively, WOMAC function scores had not significantly further improved whereas several gait parameters significantly improved in the low function group. WOMAC function scores and gait parameters were only moderately correlated (Spearman's r=0.33-0.51).

INTERPRETATION

In a cohort of patients undergoing total hip arthroplasty, pre-operative differences in mean WOMAC function scores and gait parameters between low and high function subgroups disappeared by 3 months post-operatively. Gait parameters only improved significantly during the first 3 post-operative months in patients with a low pre-operative function, highlighting the importance of investigating relative changes rather than the absolute changes and the need to consider patients with high and low functions separately.

Validity of an inertial measurement unit to assess pelvic orientation angles during gait, sit-stand transfers and step-up transfers: Comparison with an optoelectronic motion capture system

An inertial measurement unit (IMU) allows kinematic evaluation of human motion with fewer operational constraints than a gold standard optoelectronic motion capture (MOCAP) system. The study's aim was to compare IMU and MOCAP measurements of dynamic pelvic orientation angles during different activities of daily life (ADL): gait, sit-to-stand (STS) transfers and block step-up (BS) transfers. A single IMU was attached onto the lower back in seventeen healthy participants (8F/9 M, age 19-31 years; BMI < 25) and optical skin markers were attached onto anatomical pelvic landmarks for MOCAP measurements. Comparisons between IMU and MOCAP by Bland-Altman plots demonstrated that measurements were between 2SD of the absolute difference and Pearson's correlation coefficients were between 0.85 and 0.94. Frontal plane pelvic angle estimations achieved a RMSE in the range of [2.7°-4.5°] and sagittal plane measurements achieved a RMSE in the range of [2.7°-8.9°] which were both lowest in gait. Waveform peak detection times demonstrated ICCs between 0.96 and 1.00. These results are in accordance to other studies comparing IMU and MOCAP measurements with different applications and suggest that an IMU is a valid tool to measure dynamic pelvic angles during various activities of daily life which could be applied to monitor rehabilitation in a wide variety of musculoskeletal disorders.

Patient-reported outcome measures versus inertial performance-based outcome measures: A prospective study in patients undergoing primary total knee arthroplasty

BACKGROUND

Outcome assessment of total knee arthroplasty (TKA) by subjective patient reported outcome measures (PROMs) may not fully capture the functional (dis-)abilities of relevance. Objective performance-based outcome measures could provide distinct information. An ambulant inertial measurement unit (IMU) allows kinematic assessment of physical performance and could potentially be used for routine follow-up.

AIM

To investigate the responsiveness of IMU measures in patients following TKA and compare outcomes with conventional PROMs.

METHODS

Patients with end stage knee OA (n=20, m/f=7/13; age=67.4 standard deviation 7.7 years) were measured preoperatively and one year postoperatively. IMU measures were derived during gait, sit-stand transfers and block step-up transfers. PROMs were assessed by using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Knee Society Score (KSS). Responsiveness was calculated by the effect size, correlations were calculated with Spearman's rho correlation coefficient.

RESULTS

One year after TKA, patients performed significantly better at gait, sit-to-stand transfers and block step-up transfers. Measures of time and kinematic IMU measures demonstrated significant improvements postoperatively for each performance-based test. The largest improvement was found in block step-up transfers (effect size=0.56-1.20). WOMAC function score and KSS function score demonstrated moderate correlations (Spearman's rho=0.45-0.74) with some of the physical performance-based measures pre- and postoperatively.

CONCLUSION

To characterize the changes in physical function after TKA, PROMs could be supplemented by performance-based measures, assessing function during different activities and allowing kinematic characterization with an ambulant IMU.

Accelerometer-based Physical Activity Monitoring in Patients with Knee Osteoarthritis: Objective and Ambulatory Assessment of Actual Physical Activity During Daily Life Circumstances

Background:

It is important to assess physical activity objectively during daily life circumstances, to understand the association between physical activity and diseases and to determine the effectiveness of interventions. Accelerometer-based physical activity monitoring seems a promising method and could potentially capture all four FITT (i.e. Frequency, Intensity, Time, Type) components of physical activity considered by the World Health Organization (WHO).

Aim:

To assess the four FITT components of physical activity with an accelerometer during daily life circumstances and compare with self-reported levels of physical activity in patients with knee osteoarthritis (OA) and a healthy control group.

Methods:

Patients (n=30) with end-stage knee OA and age-matched healthy subjects (n=30) were measured. An ambulant tri-axial accelerometer was placed onto the lateral side of the upper leg. Physical activity was measured during four consecutive days. Using algorithm-based peak detection methods in Matlab, parameters covering the four FITT components were assessed. Self-reported physical activity was assessed using the Short questionnaire to assess health enhancing physical activity (SQUASH).

Results:

Knee OA patients demonstrated fewer walking bouts (154 ±79 versus 215 ±65 resp.; p=0.002), step counts (4402 ±2960 steps/day versus 6943 ±2581 steps/day; p=0.001) and sit-to-stand (STS) transfers (37 ±14 versus 44 ±12; p=0.031) compared to controls. Knee OA patients demonstrated more time sitting (65 ±15% versus 57 ±10% resp.; p=0.029), less time walking (8 ±4% versus 11 ±4% resp.; p=0.014) and lower walking cadence (87 ±11steps/min versus 99 ± 8steps/min resp.; p<0.001). Accelerometer-based parameters of physical activity were moderately-strong (Pearsons’s r= 0.28-0.49) correlated to self-reported SQUASH scores.

Conclusion:

A single ambulant accelerometer-based physical activity monitor feasibly captures the four FITT components of physical activity and provides more insight into the actual physical activity behavior and limitations of knee OA patients in their daily life.

Objective outcome evaluation using inertial sensors in subacromial impingement syndrome: a five-year follow-up study

Shoulder-related dysfunction is the second most common musculoskeletal disorder and is an increasing burden on health-care systems. Commonly used clinical questionnaires suffer from subjectivity, pain dominance and a ceiling effect. Objective functional measurement has been identified as a relevant issue in clinical rehabilitation. Inertia based motion analysis (IMA) is a new generation of objective outcome assessment tool; it can produce objective movement parameters while being fast, cheap and easy to operate. In this prospective study, an inertial sensor comprising a three-dimensional accelerometer and gyroscope is attached at the humerus to measure shoulder movements during two motion tasks in patients with subacromial impingement syndrome at baseline and at five-year after treatment. One hundred healthy subjects served as healthy reference database and 15 patients were measured pre- and post-treatment. IMA was better able to detect improvement in shoulder movements compared to the clinical questionnaires (Disability of Arm, Shoulder and Hand (DASH) and Simple Shoulder Test (SST); p < 0.05) and was hardly correlated with the clinical questionnaires (Pearson R = 0.39). It may therefore add an objective functional dimension to outcome assessment. The fast assessment (t < 5 min) of a simple motion test makes it suitable for routine clinical follow-up.

Inertia based functional scoring of the shoulder in clinical practice

Shoulder-related dysfunction is the second most common musculoskeletal disorder and is responsible for an increasing burden on health-care systems. Commonly used clinical outcome scores suffer from subjectivity, pain dominance and a ceiling effect. Objective functional measurement has been identified as a relevant issue in clinical rehabilitation. In recognition of this goal simple techniques for routine clinical application have been investigated with some success. Inertia based motion analysis (IMA) is a new generation of objective outcome assessment tool; it can produce objective movement parameters while being fast, cheap and easy to operate. This study investigates if a simple IMA shoulder test is suitable as a functional outcome measure for routine clinical follow-up. We measured 100 healthy subjects and 50 patients with confirmed unilateral shoulder pathology. Two motion tasks were performed on both shoulders and two simple motion parameters based on angular rate and acceleration were calculated. Patients were also assessed by the disability of arm, shoulder and hand (DASH) and the simple shoulder test. IMA produced high intra- (ICC = 0.94) and inter-assessor reliability (ICC = 0.90). Asymmetry was >3 times higher in patients than in healthy controls (p < 0.01). Healthy and pathological subjects could be distinguished with high diagnostic sensitivity (>84.0%) and specificity (>81.0%). There was a weak correlation between the IMA shoulder score and the clinical questionnaires (Pearson R < 0.25), as it may add an objective functional dimension to outcome assessment. The fast assessment (t < 5 min) of a simple motion task makes it workable for routine clinical follow-up. The IMA shoulder test adds objective information on functional capacity to the clinical scores and may help the physician in his decision-making, follow-up of treatment, effect of training and possibly lead to the development of new therapeutic interventions.

The influence of age, muscle strength and speed of information processing on recovery responses to external perturbations in gait

Dynamic imbalance caused by external perturbations to gait can successfully be counteracted by adequate recovery responses. The current study investigated how the recovery response is moderated by age, walking speed, muscle strength and speed of information processing. The gait pattern of 50 young and 45 elderly subjects was repeatedly perturbed at 20% and 80% of the first half of the swing phase using the Timed Rapid impact Perturbation (TRiP) set-up. Recovery responses were identified using 2D cameras. Muscular factors (dynamometer) and speed of information processing parameters (computer-based reaction time task) were determined. The stronger, faster reacting and faster walking young subjects recovered more often by an elevating strategy than elderly subjects. Twenty three per cent of the differences in recovery responses were explained by a combination of walking speed (B=-13.85), reaction time (B=-0.82), maximum extension strength (B=0.01) and rate of extension moment development (B=0.19). The recovery response that subjects employed when gait was perturbed by the TRiP set-up was modified by several factors; the individual contribution of walking speed, muscle strength and speed of information processing was small. Insight into remaining modifying factors is needed to assist and optimise fall prevention programmes.

Accelerometry-based gait analysis, an additional objective approach to screen subjects at risk for falling

This study investigated whether the Tinetti scale, as a subjective measure for fall risk, is associated with objectively measured gait characteristics. It is studied whether gait parameters are different for groups that are stratified for fall risk using the Tinetti scale. Moreover, the discriminative power of gait parameters to classify elderly according to the Tinetti scale is investigated. Gait of 50 elderly with a Tinneti>24 and 50 elderly with a Tinetti≤24 was analyzed using acceleration-based gait analysis. Validated algorithms were used to derive spatio-temporal gait parameters, harmonic ratio, inter-stride amplitude variability and root mean square (RMS) from the accelerometer data. Clear differences in gait were found between the groups. All gait parameters correlated with the Tinetti scale (r-range: 0.20-0.73). Only walking speed, step length and RMS showed moderate to strong correlations and high discriminative power to classify elderly according to the Tinetti scale. It is concluded that subtle gait changes that have previously been related to fall risk are not captured by the subjective assessment. It is therefore worthwhile to include objective gait assessment in fall risk screening.

Comparative functional analysis of two hypothetical chloroplast open reading frames (ycf) involved in chlorophyll biosynthesis from Synechocystis sp. PCC6803 and plants

Hypothetical chloroplast open reading frames (ycfs) are highly conserved and interspecifically occurring genes in plastomes of plants and algae with significant functions in gene expression and photosynthesis. However, the function of many ycfs is still in vain so that attention is directed to other chloroplast functions such as metabolism of co-factors, protein translocation and protection against abiotic stress. We provide a comprehensive functional description of ycf53 and ycf59, two genes involved in chlorophyll biosynthesis. While ycf59 encodes an essential enzymatic component of Mg protoporphyrin monomethylester cyclase, ycf53 encodes a posttranslational regulator of chlorophyll biosynthesis. Their roles in tetrapyrrole biosynthesis were compared by using cyanobacterial and plant mutants with modulated expression of these two genes. Our work provides indications for diverse effects of these homologous gene products in plants and cyanobacteria on tetrapyrrole biosynthesis and photosynthesis.

The Viking viewer for connectomics: scalable multi-user annotation and summarization of large volume data sets

Modern microscope automation permits the collection of vast amounts of continuous anatomical imagery in both two and three dimensions. These large data sets present significant challenges for data storage, access, viewing, annotation and analysis. The cost and overhead of collecting and storing the data can be extremely high. Large data sets quickly exceed an individual's capability for timely analysis and present challenges in efficiently applying transforms, if needed. Finally annotated anatomical data sets can represent a significant investment of resources and should be easily accessible to the scientific community. The Viking application was our solution created to view and annotate a 16.5 TB ultrastructural retinal connectome volume and we demonstrate its utility in reconstructing neural networks for a distinctive retinal amacrine cell class. Viking has several key features. (1) It works over the internet using HTTP and supports many concurrent users limited only by hardware. (2) It supports a multi-user, collaborative annotation strategy. (3) It cleanly demarcates viewing and analysis from data collection and hosting. (4) It is capable of applying transformations in real-time. (5) It has an easily extensible user interface, allowing addition of specialized modules without rewriting the viewer.

Towards unobtrusive in vivo monitoring of patients prone to falling

Falling is a serious health problem for many elderly. To investigate whether the higher fall incidence in elderly is due to a higher probability of experiencing near falls in daily life, it is necessary to evaluate the stumble incidence of elderly in daily life. Accelerometers are already frequently used for in vivo activity monitoring. The current study investigates whether an ambulant and unobtrusive accelerometer can identify stumbles from treadmill walking using a wavelet based detection approach. Seventy nine healthy subjects walked on a treadmill with a triaxial accelerometer attached at the level of the sacrum. Stumbles were induced using a specially designed braking system (The TRiP). The TRiP evoked 30 stumbles at different phases of the swing phase. A wavelet-based detection algorithm is used to isolate the stumbles from treadmill walking, with a specificity of 99.9% and a sensitivity of 98.4%.

A comparison of four systems for calibration when templating for total hip replacement with digital radiography

We have investigated the accuracy of the templating of digital radiographs in planning total hip replacement using two common object-based calibration methods with the ball placed laterally (method 1) or medially (method 2) and compared them with two non-object-based methods. The latter comprised the application of a fixed magnification of 121% (method 3) and calculation of magnification based on the object-film-distance (method 4). We studied the post-operative radiographs of 57 patients (19 men, 38 women, mean age 73 years (53 to 89)) using the measured diameter of the prosthetic femoral head and comparing it with the true value. Both object-based methods (1 and 2) produced large errors (mean/maximum: 2.55%/17.4% and 2.04%/6.46%, respectively). Method 3 applying a fixed magnification and method 4 (object-film-distance) produced smaller errors (mean/maximum 1.42%/5.22% and 1.57%/4.24%, respectively; p < 0.01). The latter results were clinically relevant and acceptable when planning was allowed to within one implant size. Object-based calibration (methods 1 and 2) has fundamental problems with the correct placement of the calibration ball. The accuracy of the fixed magnification (method 3) matched that of object-film-distance (method 4) and was the most reliable and efficient calibration method in digital templating.

Acceleration-based gait test for healthy subjects: reliability and reference data

Accelerometers enable us to analyse gait outside conventional gait laboratories. Before these devices can be used in large scale studies and in clinical settings a thorough evaluation of their performance in different populations is required. The aim of this study was to present an acceleration-based reference database for healthy gait. The repeatability and inter-observer reliability of acceleration-based gait analysis was investigated. The sensitivity was tested on different age groups and the effect of gender was studied. A comprehensive set of gait parameters (i.e. cadence, speed, asymmetry and irregularity) were studied in 60 women and 60 men. Basic gait parameters showed high repeatability (VC(cadence) 1.51%, ICC(cadence) 0.996) and inter-observer reliability (ICC(cadence) 0.916), while asymmetry and irregularity showed lower repeatability (VC(asym) 47.88%, ICC(asym) 0.787) and inter-observer reliability (ICC(asym) 0.449). The effects of age and gender on gait parameters were found to be consistent with those reported in studies using other methodologies. These findings and the advantages of the device support the application of AGA for routine clinical use and in daily life.

Inoculation of sugarcane with Pantoea sp. increases amino acid contents in shoot tissues; serine, alanine, glutamine and asparagine permit concomitantly ammonium excretion and nitrogenase activity of the bacterium

Pantoea sp. is an endophytic nitrogen-fixing bacterium isolated from sugarcane tissues. The aim of the present study was to determine the contents of amino acids in sugarcane as a result of inoculation of nodes and nodal roots with Pantoea sp. strain 9C and to evaluate the effects of amino acids on growth, nitrogenase activity and ammonium excretion of the bacterium. Content of almost all amino acids increased in 30-day-old plantlets by root inoculation. The most abundant amino acids in shoot tissues were asparagine and proline, and those in nodal roots were asparagine, proline, aspartic acid, glutamic acid and serine. The bacterium was able to grow on all tested amino acids except histidine, isoleucine and leucine. Nitrogenase Pantoea sp. was partially inhibited by 1, 2 or 5mmolL(-1) and completely inhibited by 10mmolL(-1) of NH(4)(+) in the media. Pantoea sp. showed nitrogenase activity in 5mmolL(-1) of serine, asparagine, threonine, alanine, proline, tyrosine, valine, methionine, lysine, phenylalanine, cysteine, tryptophan, citrulline and ornithine. Pantoea sp. did not excrete ammonium when it grew in vivo conditions favoring nitrogen fixation; however, ammonium was detected in the supernatant when 5mmolL(-1) asparagine, aspartic acid, alanine, serine or glutamine was added to the medium. The highest ammonium concentration in the supernatant was detected, when Pantoea grew on serine. Ammonium in the supernatant and nitrogenase activity were only detectable concomitantly when the medium was supplemented with serine, alanine, glutamine or asparagine. We discuss roles of amino acids on plant-bacteria interaction during the colonization of sugarcane plants.

The determination of linear and angular penetration of the femoral head into the acetabular component as an assessment of wear in total hip replacement

We have compared four computer-assisted methods to measure penetration of the femoral head into the acetabular component in total hip replacement. These were the Martell Hip Analysis suite 7.14, Rogan HyperOrtho, Rogan View Pro-X and Roman v1.70. The images used for the investigation comprised 24 anteroposterior digital radiographs and 24 conventional acetate radiographs which were scanned to provide digital images. These radiographs were acquired from 24 patients with an uncemented total hip replacement with a follow-up of approximately eight years (mean 8.1; 6.3 to 9.1). Each image was measured twice by two blinded observers. The mean annual rates of penetration of the femoral head measured in the eight-year single image analysis were: Martell, 0.24 (SD 0.19); HyperOrtho, 0.12 (SD 0.08); View Pro-X, 0.12 (SD 0.06); Roman, 0.12 (SD 0.07). In paired analysis of the six-month and eight-year radiographs: Martell, 0.35 (SD 0.22); HyperOrtho, 0.15 (SD 0.13); View Pro-X, 0.11 (SD 0.06); Roman, 0.11 (SD 0.07). The intra- and inter-observer variability for the paired analysis was best for View Pro-X and Roman software, with intraclass correlations of 0.97, 0.87 and 0.96, 0.87, respectively, and worst for HyperOrtho and Martell, with intraclass correlations of 0.46, 0.13 and 0.33, 0.39, respectively.

The Roman method proved the most precise and the most easy to use in clinical practice and the software is available free of charge. The Martell method showed the lowest precision, indicating a problem with its edge detection algorithm on digital images.

The development of a model for in vitro testing of femoral stems in impaction bone grafting

Comprehension of the biomechanical behaviour of orthopaedic implants is essential. This paper describes the development of an in vitro model to investigate the behaviour of femoral implants in the revision setting.

The development of a femoral model and a bone graft substitute is described. The properties of human, bovine, ovine morselized bone graft, and a graft substitute were compared. On measuring hoop strain after impaction bone grafting there was no significant difference between the ovine bone graft and graft substitute with the size 1 Exeter stem. The results suggest that this bone graft substitute is a viable alternative for in vitro testing. The authors recommend the use of the graft substitute and the femoral model to predict femoral stem biomechanics.

The influence of implant design on periprosthetic bone remodelling of two types of uncemented HA-coated hip stems. A two-year follow-up study using DEXA

Proximal bone resorption and an increased fracture rate in the ABG-I stem has been shown. For these reasons the ABG-I stem design was changed to the ABG-II. In this study periprosthetic bone loss around the ABG-I vs ABG-II is compared to verify if the design changes resulted in improved proximal bone preservation.

METHODS

51 patients were randomised to either the ABG-I or ABG-II hip prosthesis. Periprosthetic BMD change at various time points was measured using DEXA. Between the two groups (age, gender, weight etc.) no statistical difference was encountered. Compared to the baseline at two years the ABG-II preserved bone better proximally (e.g. zone 7: ABG-II: -3.7%, ABG-I: -11.9%, p=0.05) than the ABG-I. Distally, the trend was opposite and less bone loss was measured for the ABG-I than the ABG-II in zones 3, 4 and 5 (n.s.).

CONCLUSION

this study confirms the philosophy behind the design changes from the ABG-I to ABG-II stem where increased elasticity, more proximal HA-coating, a shorter and distally polished stem, were meant to reduce proximal bone resorption. In future this may lead to fewer periprosthetic fractures and to less complicated revision surgery.

Periprosthetic fractures around cementless hydroxyapatite-coated femoral stems

We studied 14 periprosthetic femoral fractures out of a series of 619 hydroxyapatite coated hip implants and compared the outcome to published treatment algorithms using the Vancouver classification. There were five type A fractures, six B1, two B2, and one type B3 fracture. All but one type A fractures were treated conservatively. Compared with the Vancouver classification, we observed a different fracture type in the type B fractures. No fractures at the tip of the stem were seen, as in cemented implants. Three B1 fractures were treated operatively due to fracture displacement, and three were treated conservatively. The B2 and B3 fractures were managed with long, uncemented, revision stems because of a disrupted bone-prosthesis interface. All fractures healed well. This study confirms that the modified algorithm of management of periprosthetic fractures, using the Vancouver classification, is a simple, reproducible, classification system for uncemented prostheses. Conservative treatment is a valid option if the implant is stable whilst surgical intervention is mandatory if the implant is loose.

Fetal MCG and fetal MEG measurements with a 3-channel SQUID system

Since the high costs of common large array SQUID system may hinder widespread application of fetal magnetoencephalography (fMEG) and magnetocardiography (fMCG), we intended to investigate a small non-commercial 3-channel SQUID system. The system comprises 3 axial first order gradiometers with 7 cm base length, 2 cm diameter and 2x2 windings of niobium wire, dc-SQUIDs (UJ-111), and current locked mode SQUID electronics that form an equal length triangle (22.5 mm). The system is mounted in a Cryostat BFH-7 model 16 with 5 mm "warm"-"cold" distance. System noise is about 10 fT/Hz1/2. The fMEG and fMCG were recorded between 29 - 40 weeks of gestation after sonographic localization of the fetal head and heart using a 31-channel biomagnetometer (Philips) and the 3-channel-system, both in the same magnetically shielded room. The fMEG was recorded continuously over 500 sec (500 auditory stimuli, 100 dB SPL, 500 Hz, 50 ms, ISI 0.8-1.2/1.6-2.4 sec, trigger channel, maternal ECG lead, sampling rate 1 kHz). The fMCG was recorded over a period of 5 minutes after dewar readjustment. The detection rates of cortical auditory evoked responses (CAER) reached 100 % for both systems. Cross confirmation of the components was difficult and may have uncovered false positive component detection. The fMCG was characterized by a systematic increase in SNR under application of the smaller device. The small size array provides a profitable alternative for the fetal applications.

Subsidence in impaction grafting: the effect of adding a ceramic bone graft extender to bone

The incidence of revision total hip arthroplasty is increasing dramatically and the associated demand for allograft bone is likely to exceed the available supply. In addition, allograft presents potential problems with regard to infection, antigenicity, availability, reproducibility and cost. It is therefore desirable to develop an alternative to allograft. This study investigated BoneSave, a porous tricalcium phosphate-hydroxyapatite ceramic for use in impaction grafting of the femur at revision total hip arthroplasty. The findings of an in vitro mechanical study comparing the initial stability of pure allograft, a volume mixture of 50 per cent allograft and 50 per cent BoneSave, and a volume mixture of 10 per cent allograft and 90 per cent BoneSave are reported. The BoneSave-allograft mixtures exhibit both much greater mechanical stability and reproducibility than the pure allograft (p < 0.05) at all tested loads (200-800 N). At high peak loads the high volume (90%, v/v) BoneSave mix also provided higher mechanical stability than the medium volume (50 per cent BoneSave-50 per cent allograft) mix (p < 0.05). These results demonstrate thatfrom a mechanical standpoint the tested ceramic provides adequate initial stability to be used as a bone graft extender with allograft in impaction grafting of the femur.

The effect of preparatory technique on the compressive properties of morsellised bone graft

none.

Administration of recombinant rhesus interleukin-12 during acute simian immunodeficiency virus (SIV) infection leads to decreased viral loads associated with prolonged survival in SIVmac251-infected rhesus macaques

The ability of recombinant rhesus interleukin-12 (rMamu-IL-12) administration during acute simian immunodeficiency virus SIVmac251 infection to influence the quality of the antiviral immune responses was assessed in rhesus macaques. Group I (n = 4) was the virus-only control group. Group II and III received a conditioning regimen of rMamu-IL-12 (10 and 20 microg/kg, respectively, subcutaneously [s.c.]) on days -2 and 0. Thereafter, group II received 2 microg of IL-12 per kg and group III received 10 microg/kg s.c. twice a week for 8 weeks. On day 0 all animals were infected with SIVmac251 intravenously. While all four group I animals and three of four group II animals died by 8 and 10 months post infection (p.i.), all four group III animals remained alive for >20 months p.i. The higher IL-12 dose led to lower plasma viral loads and markedly lower peripheral blood mononuclear cell and lymph node proviral DNA loads. During the acute viremia phase, the high-IL-12-dose monkeys showed an increase in CD3(-) CD8 alpha/alpha(+) and CD3(+) CD8 alpha/alpha(+) cells and, unlike the control and low-IL-12-dose animals, did not demonstrate an increase in CD4(+) CD45RA(+) CD62L(+) naive cells. The high-IL-12-dose animals also demonstrated that both CD8 alpha/alpha(+) and CD8 alpha/beta(+) cells produced antiviral factors early p.i., whereas only CD8 alpha/beta(+) cells retained this function late p.i. Long-term survival correlated with sustained high levels of SIV gag/pol and SIV env cytotoxic T lymphocytes and retention of high memory responses against nominal antigens. This is the first study to demonstrate the capacity of IL-12 to significantly protect macaques from SIV-induced disease, and it provides a useful model to more precisely identify correlates of virus-specific disease-protective responses.

Crystal structure and substrate binding modeling of the uroporphyrinogen-III decarboxylase from Nicotiana tabacum. Implications for the catalytic mechanism

The enzymatic catalysis of many biological processes of life is supported by the presence of cofactors and prosthetic groups originating from the common tetrapyrrole precursor uroporphyrinogen-III. Uroporphyrinogen-III decarboxylase catalyzes its conversion into coproporphyrinogen-III, leading in plants to chlorophyll and heme biosynthesis. Here we report the first crystal structure of a plant (Nicotiana tabacum) uroporphyrinogen-III decarboxylase, together with the molecular modeling of substrate binding in tobacco and human enzymes. Its structural comparison with the homologous human protein reveals a similar catalytic cleft with six invariant polar residues, Arg(32), Arg(36), Asp(82), Ser(214) (Thr in Escherichia coli), Tyr(159), and His(329) (tobacco numbering). The functional relationships obtained from the structural and modeling analyses of both enzymes allowed the proposal for a refined catalytic mechanism. Asp(82) and Tyr(159) seem to be the catalytic functional groups, whereas the other residues may serve in substrate recognition and binding, with Arg(32) steering its insertion. The crystallographic dimer appears to represent the protein dimer under physiological conditions. The dimeric arrangement offers a plausible mechanism at least for the first two (out of four) decarboxylation steps.

Characterization of Chlamydomonas mutants defective in the H subunit of Mg-chelatase

Two chlorophyll-deficient mutants of Chlamydomonas reinhardtii, chl1 and brs-1, are light sensitive and, when grown heterotrophically in the dark, accumulate protoporphyrin IX and exhibit yellow/orange pigmentation. The lesions in both mutants were mapped to the gene (CHLH) for the plastid-localized H subunit of the heterotrimeric magnesium chelatase that catalyzes the insertion of magnesium into protoporphyrin IX. The genetic defects in the mutants could be assigned to +1 frameshift mutations in exon 9 (chl1) and exon 10 (brs-1) of the CHLH gene. In both mutants, the H subunit of magnesium chelatase was undetectable, but, as shown for chl1, the steady-state levels of the I and D subunits were unaltered in comparison to wild type. The CHLH gene exhibits marked light inducibility: levels of both the mRNA and the protein product are strongly increased when cultures are shifted from from the dark into the light, suggesting that this protein may play a crucial role in the light regulation of chlorophyll biosynthesis.

Tobacco uroporphyrinogen-III decarboxylase: characterization, crystallization and preliminary X-ray analysis

Uroporphyrinogen-III decarboxylase from Nicotiana tabacum is a plastidial enzyme involved in the biosynthesis of chlorophyll and haem. Sedimentation equilibrium with protein producing diffracting crystals clearly indicates that the enzyme is a homodimer under similar ionic strength conditions to those found in the chloroplast stroma. Additionally, dynamic light scattering reveals an ionic strength dependence for this oligomerization state. Crystals were obtained in the hexagonal space group P622 with one molecule per asymmetric unit and diffracted to 2.3 A resolution using synchrotron radiation.

Impaired expression of the plastidic ferrochelatase by antisense RNA synthesis leads to a necrotic phenotype of transformed tobacco plants

Protoporphyrin IX is the last common intermediate of tetrapyrrole biosynthesis. The chelation of a Mg2+ ion by magnesium chelatase and of a ferrous ion by ferrochelatase directs protoporphyrin IX towards the formation of chlorophyll and heme, respectively. A full length cDNA clone encoding a ferrochelatase was identified from a Nicotiana tabacum cDNA library. The encoded protein consists of 497 amino acid residues with a molecular weight of 55.4 kDa. In vitro import of the protein into chloroplasts and its location in stroma and thylakoids confirm its close relationship to the previously described Arabidopsis thaliana plastid-located ferrochelatase (FeChII). A 1700-bp tobacco FeCh cDNA sequence was expressed in Nicotiana tabacum cv. Samsun NN under the control of the CaMV 35S promoter in antisense orientation allowing investigation into the consequences of selective reduction of the plastidic ferrochelatase activity for protoporphyrin IX channeling in chloroplasts and for interactions between plastidic and mitochondrial heme synthesis. Leaves of several transformants showed a reduced chlorophyll content and, during development, a light intensity-dependent formation of necrotic leaf lesions. In comparison with wild-type plants the total ferrochelatase activity was decreased in transgenic lines leading to an accumulation of photosensitizing protoporphyrin IX. Ferrochelatase activity was reduced only in plastids but not in mitochondria of transgenic plants. By means of the specifically diminished ferrochelatase activity consequences of the selective inhibition of protoheme formation for the intracellular supply of heme can be investigated in the future.

Optimizing a hydroxyapatite/tricalcium-phosphate ceramic as a bone graft extender for impaction grafting

The mechanical properties of morsellized bone allografts and synthetic hydroxapatite/tricalcium-phosphate (HA/TCP) ceramic extender materials for the use in impaction grafting revision hip surgery were investigated using two test methods: a basic compression test and an endurance test in an in-vitro model of an impaction grafted femur. Formalin fixed ovine bone graft was identified as mechanically similar to fresh human bone and thus suitable as an experimental material for in-vitro testing. For 1 : 1 volumetric mixes of bone allograft and synthetic extender, the granular ceramic's properties were varied in porosity, chemical composition, sintering temperature and particle size. Initial mechanical stability, a crucial prerequisite for clinical success in impaction grafting, was increased for all bone/extender mixes. A high porosity, tricalcium-phosphate rich ceramic of medium particle size and sintered at high temperatures was recognized as an optimized extender material for impaction grafting balancing the mechanical and biological demands. Using the extender without bone graft as a pure replacement is not recommended.

Chronic immune stimulation accelerates SIV-induced disease progression

The contribution of chronic immune stimulation on the progression of lentivirus-induced disease was evaluated in the SIVmac251 macaque model of AIDS. Following SIV inoculation, seroconversion and control of the acute viral replication phase, repeated immune stimulations with tetanus toxoid (TT), keyhole limpet hemocyanin (KLH) and allogeneic peripheral blood mononuclear cells (PBMC) were initiated in four monkeys. These animals showed a significant shortening of survival when compared with eight non-immune-stimulated control animals inoculated with the same route, dose and stock of SIVmac251 (median survival 9.5 months versus 17 months, P = 0.010). In addition, when the comparison was extended to another 22 control animals of different origin but inoculated by the same route with similar doses and stocks of SIVmac251, the difference in survival was still significant (9.5 versus 18 months, P = 0.003). This accelerated progression of symptomatic disease was not accompanied with significant increases in plasma viral loads, but suboptimal antibody responses to the immunizing antigens were noted, correlating with the length of survival. These findings may have implications for HIV-infected humans suffering from chronic infectious diseases.

[Collection of Arabidopsis thaliana mutants with altered sensitivity to oxidative stress inductors]

Selective systems for screening Arabidopsis thaliana (L.) Heynh. mutants with altered sensitivity to the oxidative stress (OS) inductors norflurazon (NF), acifluorfen (AF), and plumbagin (PB) were developed and a collection of 28 mutants was obtained. Dwarf and necrotic forms predominated among the NF-tolerant mutants, while pigment mutants and those with changed root morphology prevailed among the AF-tolerant and PB-sensitive mutants, respectively. Genetic and biochemical analysis of certain mutants was performed; quantitative and qualitative changes in the content of superoxide dismutase and peroxidase isoforms have been revealed. These data, complemented by the data on the cross-tolerance (sensitivity) of the mutants to paraquat, indicate a correlation between tolerance to the OS inductors and the functions of antioxidant systems.