Validation and interval scale transformation of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) in patients undergoing knee arthroplasty, using the Rasch model

OBJECTIVES: Interval scale reduce measurement bias compared to ordinal scale. We aimed to evaluate the fit of Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) to the Rasch model and derive the transformation table for interval scale measurement. METHODS: Data from osteoarthritis patients listed for knee arthroplasty (KA) pre-operatively, and at 6- and 12- months post-operative was used. WOMAC was calibrated for fit to the Rasch model for monotonicity, homogeneity, local item independence and absence of differential item functioning (DIF) in a randomly selected 900 patients, 300 from each time point; parameter estimates were then imported into the full data set. Responsiveness was reported through Standard Error of Measurement (SEM); Smallest Detectable Difference (SDD), %SDD and effect sizes (ES) between baseline and 6-months. WOMAC was transformed from ordinal to interval values. RESULTS: 1136 patients (mean age 65.9 years, 69.9% female) were included. WOMAC pain (0−20), function (0−68) and total scores (0−96) had adequate fit to Rasch model with good reliability (Person Separation Index: 0.76, 0.80 and 0.79). No item deletion was required. The SEM, SDD, %SDD and ES of WOMAC total were 4.4, 6.9, 10.1, and 1.97. No significant DIF was seen for age, sex, body mass index, type of KA, languages, and education level. WOMAC pain, function and total scores were transformed to interval scales. CONCLUSION: WOMAC total, pain and function scales had adequate fit to the Rasch model, providing unidimensional measure with good reliability and responsiveness. Transformation of WOMAC to interval scale measurement is applicable to other studies

Risk factors for a post-operative neutrally aligned total knee arthroplasty in the sagittal plane developing fixed flexion deformity at 2 years follow up study

Background: The incidence of fixed flexion deformity (FFD) following total knee arthroplasty (TKA) has been reported to be as high as 17%, increasing demand on the quadriceps and hindering mobility. The aim of this study is then to identify these predictors for the development of FFD.Methods: In this retrospective study, all patients who underwent primary TKA from January 2008 to June 2009 at a single institution were identified. All patients with neutral alignment in the sagittal place of the knee intra-operatively were identified and followed up. The knee motion was measured in both operated and contralateral knees and followed-up for a minimum of 24 months post-operatively.Results: Multivariate analysis demonstrated pre-operative FFD of the non-operated knee (p-value 0.03), pre-operative range of motion of the operated knee (p-value 0.01) and non-operated (p-value 0.01) knee and pre-operative maximum flexion of the operated knee (p-value 0.001) to be independent risk factors for development of FFD at 24 months.Conclusions: Independent risk factors for the development of post-operative FFD in TKA are pre-operative FFD of the operated knee, FFD of the non-operated knee and the maximum flexion of the operated knee. The relative risk of a male developing FFD is also as high as 1.34

Identification of Partial Discharge Through Cable-Specific Adaption and Neural Network Ensemble

[EN] This paper proposes to administer a multi-step artificial intelligence approach with an ensemble of adaptive neural networks (NNs) trained on 50000 samples to identify partial discharge (PD) diagnostic measurements for in-service medium voltage (MV) power cables. To evaluate the performance of the algorithm, a case study was performed on cables deliberately selected to contain both uncomplicated measurements and disruptive irregularities representative of conditions during field testing. The experimental test results prove that the proposed cable-specific adaptation improves PD identification accuracy, with further increment through the NN ensembles. The main contribution of the approach is in both the cable-specific adaption and the NN ensemble being applied to MV cable field measurements.Yeo, J.; Jin, H.; Rodrigo Mor, A.; Yuen, C.; Tushar, W.; Saha, TK.; Seng Ng, C. (2021). Identification of Partial Discharge Through Cable-Specific Adaption and Neural Network Ensemble. IEEE Transactions on Power Delivery. 1-10. https://doi.org/10.1109/TPWRD.2021.3093670S11

An Exploratory Study of Response Shift in Health-Related Quality of Life and Utility Assessment Among Patients with Osteoarthritis Undergoing Total Knee Replacement Surgery in a Tertiary Hospital in Singapore

AbstractObjectiveTo investigate the influence of response shift (RS) on health-related quality of life (HRQOL) and utility assessment among patients undergoing total knee replacement.MethodsConsenting patients undergoing total knee replacement were interviewed to determine their HRQOL by using the six-dimensional health state short form, derived from SF-36, and the EuroQol five-dimensional questionnaire at baseline (pretest 1) and the six-dimensional health state short form, derived from SF-36, at 6 (pretest 2) and 18 months after surgery (post-test). RS was studied by using a “then-test” approach by contacting participants 18 months after surgery and asking them to evaluate their HRQOL at baseline (then-test 1) and at 6 (then-test 2) and 18 months after surgery. RS was calculated as the score difference between pretest and then-test scores for a given time point. Relationships between RS and external variables were explored by using univariate and multiple liner regression analyses.ResultsIn 74 subjects (63% response rate, median age 68 years), median (interquantile range) six-dimensional health state short form, derived from SF-36, scores for then-tests at baseline (0.48 [0.42–0.49]) and at 6 months (0.72 [0.66–0.79]) after surgery were significantly different from respective pretest scores (0.61 [0.58–0.68] at baseline, P = 0.000; 0.69 [0.63–0.72] at 6 months, P = 0.000), showing RS at both time points. RS at baseline (0.14 [0.08–0.20]) was significantly larger than that at 6 months (−0.05 [0.14 to 0.00], P = 0.000). EuroQol five-dimensional questionnaire pretest and then-test scores at baseline also differed significantly (0.69 [0.17–0.73] vs. −0.18 [−0.23 to 0.00], P = 0.000). RS at baseline was not affected by assessed demographic or medical variables. RS at 6 months was greater in subjects with more years of education (16% of variance in multiple liner regression, P < 0.01).ConclusionRS was present and impacted HRQOL and utility assessment among patients undergoing total knee replacement before and 6 months after surgery

Gap difference in navigated TKA: a measure of the imbalanced flexion-extension gap

Introduction: The success of Total Knee Arthroplasty (TKA) hinges on balanced flexion-extension gaps. This paper aims to evaluate the correlation between imbalanced gaps and clinical outcomes, and hence help quantify the imbalanced gap in navigation-assisted total knee arthroplasty. Methods: We studied 195 knees with an average follow-up of two years. Flexion-extension gaps were obtained from computer calculation upon cementation of implants in both flexion (90°) and extension. The gap difference (GD) was defined as the measured difference between the gaps in flexion and extension. Results: At 2 years after surgery, the mean ROM in the balanced group, with GD less than or equal to 2 mm, was 115.1° ± 16.6° and the mean ROM in the imbalanced group was 116.7° ± 12.1°. This was not statistically significant with p-value 0.589. Balanced flexion-extension gaps also did not show significant difference in terms of mechanical alignment, with 0.29 ± 0.89 in the balanced group at 2 years, and 0.65 ± 1.51 in the imbalanced group with p-value 0.123. Balanced gaps however, were associated with improved outcomes in terms of physical functioning, bodily pain, social functioning, Oxford and Knee scores at 6 months and improved social functioning scores at 2 years. Conclusions: Computer navigation is a useful tool for assessing the gap balance in TKA. Balanced flexion-extension gaps, with gap differences of less than or equal to 2 mm, is associated with improved clinical outcomes at 6 months

THINK surgical TSolution-One

THINK Surgical TSolution-One® is an active-autonomous, image-based, robotic milling system which enables the surgeon to attain a consistently accurate implant component positioning. The TSolution-One® system is capable of achieving this through an image-based preoperative planning system which allows the surgeon to create, view and analyse the surgical outcome in 3D. The accuracy and precision of component positioning have been attributed to the following factors: customized distal femoral resection, accurate determination of the femoral rotational alignment, minimization of errors and maintenance of bone temperature with robotic milling. Despite all these advantages, there is still a paucity of long-term, high-quality data that demonstrates the efficacy of robotic-assisted total knee arthroplasty (TKA). Questions regarding radiation risks, prolonged surgical duration and cost-effectiveness remain unanswered. This paper aims to describe: (1) TSolution-One® surgical technique; (2) limitations and complications; (3) clinical and radiological outcomes

Full-wave analysis of mixed-mode propagation in forest environment

Asia-Pacific Microwave Conference Proceedings, APMC3997-10000028