Investigation of contact behavior on a model of the dual-mobility artificial hip joint for Asians in different inner liner thicknesses.

BACKGROUND: The four components that make up the current dual-mobility artificial hip joint design are the femoral head, the inner liner, the outer liner as a metal cover to prevent wear, and the acetabular cup. The acetabular cup and the outer liner were constructed of 316L stainless steel. At the same time, the inner liner was made of ultra-high-molecular-weight polyethylene (UHMWPE). As this new dual-mobility artificial hip joint has not been researched extensively, more tribological research is needed to predict wear. The thickness of the inner liner is a significant component to consider when calculating the contact pressure. AIM: To make use of finite element analysis to gain a better understanding of the contact behavior in various inner liner thicknesses on a new model of a dual-mobility artificial hip joint, with the ultimate objective of determining the inner liner thickness that was most suitable for this particular type of dual-mobility artificial hip joint. METHODS: In this study, the size of the femoral head was compared between two diameters (28 mm and 36 mm) and eight inner liner thicknesses ranging from 5 mm to 12 mm. Using the finite element method, the contact parameters, including the maximum contact pressure and contact area, have been evaluated in light of the Hertzian contact theory. The simulation was performed statically with dissipated energy and asymmetric behavior. The types of interaction were surface-to-surface contact and normal contact behavior. RESULTS: The maximum contact pressures in the inner liner (UHMWPE) at a head diameter of 28 mm and 36 mm are between 3.7-13.5 MPa and 2.7-10.4 MPa, respectively. The maximum von Mises of the inner liner, outer liner, and acetabular cup are 2.4-11.4 MPa, 15.7-44.3 MPa, and 3.7-12.6 MPa, respectively, for 28 mm head. Then the maximum von Mises stresses of the 36 mm head are 1.9-8.9 MPa for the inner liner, 9.9-32.8 MPa for the outer liner, and 2.6-9.9 MPa for the acetabular cup. A head with a diameter of 28 mm should have an inner liner with a thickness of 12 mm. Whereas the head diameter was 36 mm, an inner liner thickness of 8 mm was suitable. CONCLUSION: The contact pressures and von Mises stresses generated during this research can potentially be exploited in estimating the wear of dual-mobility artificial hip joints in general. Contact pressure and von Mises stress reduce with an increasing head diameter and inner liner's thickness. Present findings would become one of the references for orthopedic surgery for choosing suitable bearing geometric parameter of hip implant.

Non-redundant implicational base of formal context with constraints using SAT.

An implicational base is knowledge extracted from a formal context. The implicational base of a formal context consists of attribute implications which are sound, complete, and non-redundant regarding to the formal context. Non-redundant means that each attribute implication in the implication base cannot be inferred from the others. However, sometimes some attribute implications in the implication base can be inferred from the others together with a prior knowledge. Regarding knowledge discovery, such attribute implications should be not considered as new knowledge and ignored from the implicational base. In other words, such attribute implications are redundant based on prior knowledge. One sort of prior knowledge is a set of constraints that restricts some attributes in data. In formal context, constraints restrict some attributes of objects in the formal context. This article proposes a method to generate non-redundant implication base of a formal context with some constraints which restricting the formal context. In this case, non-redundant implicational base means that the implicational base does not contain all attribute implications which can be inferred from the others together with information of the constraints. This article also proposes a formulation to check the redundant attribute implications and encoding the problem into satisfiability (SAT) problem such that the problem can be solved by SAT Solver, a software which can solve a SAT problem. After implementation, an experiment shows that the proposed method is able to check the redundant attribute implication and generates a non-redundant implicational base of formal context with constraints.

Running-in behavior of dual-mobility cup during the gait cycle: A finite element analysis.

The running-in process is considered an essential aspect of the comprehensive wear process. The phenomenon of running-in occurs during the initial stages of wear in the prosthetic hip joint. Within the field of tribology, the running-in phenomenon of the hip joint pertains to the mechanism by which the contact surfaces of the artificial hip joint components are adjusted and a suitable lubricating film is formed. During the process of hip joint running-in, there is an interaction between the metal surface of the ball and the joint cup, which results in adjustments being made until a steady state is achieved. The achievement of desirable wear existence and reliable performance of artificial hip joint components are reliant upon the tribological running-in of the hip joint. Despite the establishment of current modeling approaches, there remains a significant lack of understanding concerning running-in wear, particularly the metal-on-polyethylene (MoP) articulations in dual-mobility cups (DMC). An essential aspect to consider is the running-in phase of the dual mobility component. The present study employed finite element analysis to investigate the running-in behavior of dual mobility cups, wherein femoral head components were matched with polyethylene liners of varying thicknesses. The analysis of the running-in phase was conducted during the normal gait cycle. The results of this investigation may be utilized to design a dual-mobility prosthetic hip joint that exhibits minimal running-in wear.

SAX and Random Projection Algorithms for the Motif Discovery of Orbital Asteroid Resonance Using Big Data Platforms.

The phenomenon of big data has occurred in many fields of knowledge, one of which is astronomy. One example of a large dataset in astronomy is that of numerically integrated time series asteroid orbital elements from a time span of millions to billions of years. For example, the mean motion resonance (MMR) data of an asteroid are used to find out the duration that the asteroid was in a resonance state with a particular planet. For this reason, this research designs a computational model to obtain the mean motion resonance quickly and effectively by modifying and implementing the Symbolic Aggregate Approximation (SAX) algorithm and the motif discovery random projection algorithm on big data platforms (i.e., Apache Hadoop and Apache Spark). There are five following steps on the model: (i) saving data into the Hadoop Distributed File System (HDFS); (ii) importing files to the Resilient Distributed Datasets (RDD); (iii) preprocessing the data; (iv) calculating the motif discovery by executing the User-Defined Function (UDF) program; and (v) gathering the results from the UDF to the HDFS and the .csv file. The results indicated a very significant reduction in computational time between the use of the standalone method and the use of the big data platform. The proposed computational model obtained an average accuracy of 83%, compared with the SwiftVis software.

Short communication: Running-in behavior on single-mobility total hip arthroplasty.

Total hip arthroplasty is a short-term solution for replacing a damaged hip joint with synthetic biomaterials. Total hip arthroplasty comes in two flavors: single and dual mobility. Mechanical and biological factors may degrade the quality of biomaterials over time. This may lead to implant failure and second surgical treatment. Wear is the crucial element leading to damaged bone and debris release throughout the body over time. Running-in is the initial wear phase between two surfaces before the steady-state phase. The stage of running-in is critical for understanding hip joint wear. Running-in and wear behavior have been extensively studied in single-mobility total hip arthroplasty, but aseptic loosening is the leading reason for restoration in arthroplasty registries. This paper seeks to summarize running-in behavior on single mobility hip implants, emphasizing its key aspects and recent developments.

Transcatheter Closure of Perimembranous Ventricular Septal Defect Using the Lifetech Konar-Multi Functional Occluder: Early to Midterm Results of the Indonesian Multicenter Study.

Background: The alternative device to close perimembranous ventricular septal defect (pmVSD) has been searched for better result, less complications and applicable for infants. However, the ideal device is still unavailable. We aimed to evaluate the effectiveness and outcome of transcatheter pmVSD closure using the KONAR-multi functional occluder (MFO). Methods: Clinical, procedural, follow-up data of pmVSD patients with symptom of heart failure or evidence of significant left to right shunt, growth failure, recurrent respiratory tract infection, and history of endocarditis who underwent transcatheter closure using the MFO were prospectively evaluated. Results: Between January 2016 and December 2017, there were complete records of 132 pmVSD children closed using MFO from eleven centers in Indonesia. The median of age was 4.5 (0.3-17.4) years; weight 14.8 (3.5-57) kg, defect size at the smallest part 3.4 (1.0-8.1) mm, flow ratio 1.6 (1.3-4.9), mean pulmonary artery pressure 18 (7-79) mmHg, fluoroscopy time 18 (3.8-91) and procedural time 75 (26-290) minutes. A retrograde approach was done in 41 (31%) patients. Procedures succeeded in first attempt in 126 (95.4%), failed in three and migration in three patients. Six of eight infants with congestive heart failure were closed successfully. Of 126 patients with successful VSD closure, 12 months follow-up were completed in all patients. The rate of complete occlusion at 1 month, 3 months, 6 months and 12 months after intervention were 95.2%, 97.6%, 99.2%, and 99.2%, respectively. New-onset aortic regurgitation and moderate tricuspid regurgitation developed only in five and three patients. Neither complete atrioventricular block, nor other complications occurred. Conclusion: Transcatheter closure of pmVSD using the MFO is safe, effective, and feasible in infants and children.

Risk Factors of Daunorubicine Induced Early Cardiotoxicity in Childhood Acute Lymphoblastic Leukemia: A Retrospective Study.

BACKGROUND: Daunorubicine, a type of anthracycline, is a drug commonly used in cancer chemotherapy that increases survival rate but consequently compromises with cardiovascular outcomes in some patients. Thus, preventing the early progression of cardiotoxicity is important to improve the treatment outcome in childhood acute lymhoblastic leukemia (ALL). OBJECTIVE: The present study aimed to identify the risk factors in anthracycline-induced early cardiotoxicity in childhood ALL. METHODS: This retrospective study was conducted by observing ALL-diagnosed children from 2014 to 2019 in Dr. Soetomo General Hospital. There were 49 patients who met the inclusion criteria and were treated with chemotherapy using Indonesian Childhood ALL Protocol 2013. Echocardiography was performed by pediatric cardiologists to compare before and at any given time after anthracycline therapy. Early cardiotoxicity was defined as a decline of left ventricle ejection fraction (LVEF) greater than 10% with a final LVEF < 53% during the first year of anthracycline administration.  Risk factors such as sex, age, risk stratification group, and cumulative dose were identified by using multiple logistic regression. Diagnostic performance of cumulative anthracycline dose was evaluated by receiver operating characteristic (ROC) curve. RESULTS: Early anthracycline-induced cardiotoxicity was observed in 5 out of 49 patients. The median cumulative dose of anthracycline was 143.69±72.68 mg/m2. Thirty-three patients experienced a decreasing LVEF. The factors associated with early cardiomyopathy were age of ≥ 4 years (PR= 1.128; 95% CI: 1.015-1.254; p= 0.001), high risk group (PR= 1.135; 95% CI: 1.016-1.269; p= 0.001), and cumulative dose of ≥120 mg / m2 (CI= 1.161; 95% CI:1.019-1.332). CONCLUSION: Age of ≥ 4 years, risk group, and cumulative dose of ≥120 mg/m2 are significant risk factors for early cardiomyopathy in childhood ALL.