Marker free model-based radiostereometric analysis for evaluation of hip joint kinematics: A validation study.

OBJECTIVES: To validate the precision of digitally reconstructed radiograph (DRR) radiostereometric analysis (RSA) and the model-based method (MBM) RSA with respect to benchmark marker-based (MM) RSA for evaluation of kinematics in the native hip joint. METHODS: Seven human cadaveric hemipelves were CT scanned and bone models were segmented. Tantalum beads were placed in the pelvis and proximal femoral bone. RSA recordings of the hips were performed during flexion, adduction and internal rotation. Stereoradiographic recordings were all analyzed with DRR, MBM and MM. Migration results for the MBM and DRR with respect to MM were compared. Precision was assessed as systematic bias (mean difference) and random variation (Pitman's test for equal variance). RESULTS: A total of 288 dynamic RSA images were analyzed. Systematic bias for DRR and MBM with respect to MM in translations (p < 0.018 mm) and rotations (p < 0.009°) were approximately 0. Pitman's test showed lower random variation in all degrees of freedom for DRR compared with MBM (p < 0.001). CONCLUSION: Systematic error was approximately 0 for both DRR or MBM. However, precision of DRR was statistically significantly better than MBM. Since DRR does not require marker insertion it can be used for investigation of preoperative hip kinematics in comparison with the postoperative results after joint preserving hip surgery. Cite this article: L. Hansen, S. De Raedt, P. B. Jørgensen, B. Mygind-Klavsen, B. Kaptein, M. Stilling. Marker free model-based radiostereometric analysis for evaluation of hip joint kinematics: A validation study. Bone Joint Res 2018;7:379-387. DOI: 10.1302/2046-3758.76.BJR-2017-0268.R1.

Validation of static and dynamic radiostereometric analysis of the knee joint using bone models from CT data.

OBJECTIVES: Static radiostereometric analysis (RSA) using implanted markers is considered the most accurate system for the evaluation of prosthesis migration. By using CT bone models instead of markers, combined with a dynamic RSA system, a non-invasive measurement of joint movement is enabled. This method is more accurate than current 3D skin marker-based tracking systems. The purpose of this study was to evaluate the accuracy of the CT model method for measuring knee joint kinematics in static and dynamic RSA using the marker method as the benchmark. METHODS: Bone models were created from CT scans, and tantalum beads were implanted into the tibia and femur of eight human cadaver knees. Each specimen was secured in a fixture, static and dynamic stereoradiographs were recorded, and the bone models and marker models were fitted to the stereoradiographs. RESULTS: Results showed a mean difference between the two methods in all six degrees of freedom for static RSA to be within -0.10 mm/° and 0.08 mm/° with a 95% limit of agreement (LoA) ranging from ± 0.49 to 1.26. Dynamic RSA had a slightly larger range in mean difference of -0.23 mm/° to 0.16 mm/° with LoA ranging from ± 0.75 to 1.50. CONCLUSIONS: In a laboratory-controlled setting, the CT model method combined with dynamic RSA may be an alternative to previous marker-based methods for kinematic analyses.Cite this article: K. Stentz-Olesen, E. T. Nielsen, S. De Raedt, P. B. Jørgensen, O. G. Sørensen, B. L. Kaptein, M. S. Andersen, M. Stilling. Validation of static and dynamic radiostereometric analysis of the knee joint using bone models from CT data. Bone Joint Res 2017;6:376-384. DOI: 10.1302/2046-3758.66.BJR-2016-0113.R3.

Long-term outcome and health-related quality of life in difficult-to-wean patients with and without ventilator dependency at ICU discharge: a retrospective cohort study.

BACKGROUND: Long-term outcome and quality of life (QOL) in patients requiring prolonged mechanical ventilation after failure to wean in the ICU is scarcely documented. We aimed to evaluate long-term survival and QOL in patients discharged from the ICU with a tracheostomy for difficult weaning, and with or without ventilator dependency at ICU discharge. METHODS: We retrospectively investigated post-ICU trajectories and survival in patients requiring tracheostomy for difficult weaning admitted to the medical ICU of a tertiary center between 1999 and 2013, discriminating between patients who were ventilator dependent or were weaned at ICU discharge. In 2014, a QOL assessment was done in survivors with the use of the Short Form Health Survey (SF-36) and the Severe Respiratory Insufficiency questionnaire. RESULTS: A total of 114 patients was included, of whom 59 were ventilator dependent and 55 were weaned at ICU discharge. One-year survival rates were 73 % and 69 %, respectively. Overall QOL scores for physical functioning were low, and not significantly different between patients ventilated and those weaned at ICU discharge; scores for social functioning and mental health were less below norm and similar between both groups. CONCLUSIONS: Long-term survival in patients discharged from the ICU with tracheostomy and ventilator dependency after failure to wean was not significantly different from that of patients with tracheostomy and weaned at ICU discharge. Despite the physical QOL scores being low in both groups, mental QOL was acceptable. Given the intrinsic limitations of this retrospective study, prospective and preferentially multicenter studies are required to confirm these preliminary results.

The sNIHSS-4 predicts outcome in right and left anterior circulation strokes.

BACKGROUND AND PURPOSE: Stroke severity measured by the National Institutes of Health Stroke Scale (NIHSS) is a strong predictor of functional outcome. A short version, the sNIHSS-5, scoring only strength in right and left leg, gaze, visual fields and language, was developed for use in the prehospital setting. Because scoring both legs in anterior circulation strokes is not contributive, we assessed the value of a 4-item score (the sNIHSS-4), omitting the item 'strength in the unaffected leg', in predicting stroke outcome. METHODS: The study population consisted of anterior circulation ischemic stroke patients who participated in the LUB-INT-9 trial. We included all patients in whom the following data were available: NIHSS within 6h after stroke onset and daily between days 2 and 5, and the 12-week modified Rankin Scale (mRS) score. Poor outcome was defined as a mRS score>3. RESULTS: There was an excellent correlation between the NIHSS and sNIHSS-4 at all time points for both left and right-sided strokes. Scores at day 2 were a good predictor of poor outcome. Cutoff scores for NIHSS and sNIHSS-4 at day 2 were 15 and 5 in left hemispheric strokes, and 12 and 4 in right hemispheric strokes. CONCLUSION: The sNIHSS-4 is as good as the NIHSS at predicting stroke outcome in both right and left anterior circulation strokes.

A three-dimensional analysis of osteoarthritic changes in the thumb carpometacarpal joint.

The purpose of this study is to gain a better understanding of the changes due to osteoarthritis (OA) occurring in the thumb carpometacarpal (CMC) joint by comparing quantitative geometrical measurements in computed tomography scans of healthy and pathological joints in various stages of OA. The measurements were (1) the subluxation of the metacarpal on the trapezium, (2) distance from the scaphoid centre to the metacarpal base, and (3) distance from the metacarpal base to the articulating surface of the trapezium. The three-dimensional position of three characteristic points on the metacarpal, trapezium, and scaphoid were detected in each of the 90 wrists we scanned. The distances between the points were compared by statistical analysis. With high accuracy, we have been able to confirm and quantify that subluxation occurs in the dorso-radial direction. A significant difference in trapezium height and joint space width was found between the OA and control groups. The results indicate how to restore the centre of rotation in surgical treatment of OA with total joint arthroplasty, but the clinical relevance of these findings has to be tested in further clinical studies.

Superior accuracy of model-based radiostereometric analysis for measurement of polyethylene wear: A phantom study.

OBJECTIVES: The accuracy and precision of two new methods of model-based radiostereometric analysis (RSA) were hypothesised to be superior to a plain radiograph method in the assessment of polyethylene (PE) wear. METHODS: A phantom device was constructed to simulate three-dimensional (3D) PE wear. Images were obtained consecutively for each simulated wear position for each modality. Three commercially available packages were evaluated: model-based RSA using laser-scanned cup models (MB-RSA), model-based RSA using computer-generated elementary geometrical shape models (EGS-RSA), and PolyWare. Precision (95% repeatability limits) and accuracy (Root Mean Square Errors) for two-dimensional (2D) and 3D wear measurements were assessed. RESULTS: The precision for 2D wear measures was 0.078 mm, 0.102 mm, and 0.076 mm for EGS-RSA, MB-RSA, and PolyWare, respectively. For the 3D wear measures the precision was 0.185 mm, 0.189 mm, and 0.244 mm for EGS-RSA, MB-RSA, and PolyWare respectively. Repeatability was similar for all methods within the same dimension, when compared between 2D and 3D (all p > 0.28). For the 2D RSA methods, accuracy was below 0.055 mm and at least 0.335 mm for PolyWare. For 3D measurements, accuracy was 0.1 mm, 0.2 mm, and 0.3 mm for EGS-RSA, MB-RSA and PolyWare respectively. PolyWare was less accurate compared with RSA methods (p = 0.036). No difference was observed between the RSA methods (p = 0.10). CONCLUSIONS: For all methods, precision and accuracy were better in 2D, with RSA methods being superior in accuracy. Although less accurate and precise, 3D RSA defines the clinically relevant wear pattern (multidirectional). PolyWare is a good and low-cost alternative to RSA, despite being less accurate and requiring a larger sample size.

Pre-stroke use of beta-blockers does not affect ischaemic stroke severity and outcome.

BACKGROUND AND PURPOSE: It is unclear whether pre-stroke beta-blockers use may influence stroke outcome. This study evaluates the independent effect of pre-stroke use of beta-blockers on ischaemic stroke severity and 3 months functional outcome. METHODS: Pre-stroke use of beta-blockers was investigated in 1375 ischaemic stroke patients who had been included in two placebo-controlled trials with lubeluzole. Stroke severity was assessed by either the National Institute of Health Stroke Scale (NIHSS) or the European Stroke Scale (ESS). A modified Rankin scale (mRS) score of >3 at 3 months was used as measure for the poor functional outcome. RESULTS: Two hundred and sixty four patients were on beta-blockers prior to stroke onset, and 105 patients continued treatment after their stroke. Pretreatment with beta-blockers did not influence baseline stroke severity. There was no difference in stroke severity between nonusers and those on either a selective beta(1)-blocker or a non-selective beta-blocker. The likelihood of a poor outcome at 3 months was not influenced by pre-stroke beta-blocker use or beta-blocker use before and continued after stroke onset. CONCLUSIONS: Pre-stroke use of beta-blockers does not appear to influence stroke severity and functional outcome at 3 months.

Suspected "t-cell-mediated" hypereosinophilic syndrome presenting with cerebral watershed infarcts.

We describe a case of suspected "T-cell-mediated" hypereosinophilic syndrome presenting with cerebral watershed infarcts. An extensive search for potential embolic sources was negative, supporting the hypothesis that cerebrovascular endothelial dysfunction could have caused the infarcts.

Organisation of inhospital acute stroke care and minimum criteria for stroke care units. Recommendations of the Belgian Stroke Council.

There is ample evidence from randomized trials that for patients with stroke, stroke unit care is superior to care in general medical or neurological wards. This evidence, which has been adopted by international guidelines has to be implemented into daily stroke care. This consensus document prepared by the Belgian Stroke Council provides a set of minimum criteria to meet international standards for stroke care. It is intended to provide help in the creation of stroke units in centers who do not currently have one and to provide a benchmark for centres already having organised stroke care.

Streptococcus pyogenes bacteremia: a retrospective study in a Belgian university hospital.

We retrospectively studied 29 cases of S.pyogenes bacteremia, treated from September 1985 through September 1993, in order to define the clinical pattern, predisposing factors and the outcome of S.pyogenes bacteremia in our region. The number of infections, the clinical picture and mortality rate of S.pyogenes bacteremia did not change during the study period and only 2 of 29 cases presented with a fulminant clinical course, meeting the criteria of streptococcal toxic shock syndrome. In many patients, predisposing factors such as skin abnormalities (n = 14) and airway diseases (n = 10) could be identified. Patients with underlying skin disease were mostly characterized by a clinically benign bacteremia with good prognosis. We suspect that the recently reported so-called rising incidence of severe S.pyogenes infections might be due to epidemiologic clustering and selection bias in certain regions.