Nonlinearity investigation of reliability-based topology optimization strategies with application to total hip replacement

In literature, the topology optimization can be divided into two main models. The first model is called Deterministic Topology Optimization (DTO) producing a single configuration for a given design space. The second one is called Reliability-Based Topology Optimization (RBTO) generating several layouts. In our previous work, two approaches considering the concept of Inverse Optimum Safety Factors (IOSF) were elaborated and only applied to the normal distribution being linear distribution. In this work, a nonlinearity investigation is presented to compare between the linear and nonlinear distribution. The RBTO developments are applied to the total hip replacement to provide suitable hollow stems at the conceptual design stage. The nonlinearity presented here, is related to the types of the random variable distributions. The most common distributions such as normal, lognormal, uniform and Weibull are considered here to perform the investigation. The results show the nonlinearity effect on the output parameter values, but lead to almost similar layouts of the resulting hollow stems in several cases. In certain types of distributions such as Weibull, the changes on the input parameters are very variant. At certain values of the reliability index, some input parameters of material properties exceeded their limits and the algorithm stopped.

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Integration of reliability-based topology optimization into biomechanics: Application on hollow stems used in cementless total hip arthroplasty

E3S Web of Conferences ◽

10.1051/e3sconf/202021006003 ◽

2020 ◽

Vol 210 ◽

pp. 06003

Author(s):

Ghais Kharmanda ◽

Imad Antypas ◽

Alexey Dyachenko

Keyword(s):

Topology Optimization ◽

Hip Replacement ◽

High Performance ◽

Design Space ◽

Design Stage ◽

Manufacturing Constraints ◽

Element Discretization ◽

Performance Levels ◽

Total Hip ◽

Alternative Approaches

The integration of topology optimization into biomechanical applications possesses an important key to increase the performance levels. In literature, two models can be found: Deterministic Topology Optimization (DTO) and Reliability-Based Topology Optimization (RBTO). The DTO leads to a single layout for a given design space. However, the RBTO generates several reliability-based topologies with high performance levels. Topology optimization has been already integrated into biomechanical applications such as prosthesis design. The filter-based approaches being tied to the element discretization, are previously used to control the resulting topologies or to prevent undesirable designs. These are expensive operations for fine meshes or complex domains and numerous numerical difficulties can be met. In this work, the RBTO is integrated at the conceptual design stage of the total hip replacement to control the resulting topologies to meet different constraints such as manufacturing constraints. This can provide several types of hollow stems considering the daily loading cases. Two alternative approaches based on the Optimum Safety Factors (OSF) are developed to provide two categories of solutions. The RBTO model can be integrated into the additive manufacturing technology as a topology generator satisfying several manufacturing constraints. The resulting different configurations can then be provided for various patients.

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Postoperative functioning, age, obesity, and social support influence where patients go after total hip replacement

PsycEXTRA Dataset ◽

10.1037/e556262006-011 ◽

2005 ◽

Keyword(s):

Social Support ◽

Total Hip Replacement ◽

Hip Replacement ◽

Total Hip

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The Hemodynamic and Fibrinolytic Response to Low Dose Epinephrine and Phenylephrine Infusions During Total Hip Replacement Under Epidural Anesthesia

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646293 ◽

1992 ◽

Vol 68 (04) ◽

pp. 436-441 ◽

Cited By ~ 23

Author(s):

Nigel E Sharrock ◽

George Go ◽

Robert Mineo ◽

Peter C Harpel

Keyword(s):

Heart Rate ◽

Deep Vein Thrombosis ◽

Cardiac Index ◽

Total Hip Replacement ◽

Epidural Anesthesia ◽

Hip Replacement ◽

Low Dose ◽

Total Hip ◽

Vein Thrombosis ◽

Deep Vein

SummaryLower rates of deep vein thrombosis have been noted following total hip replacement under epidural anesthesia in patients receiving exogenous epinephrine throughout surgery. To determine whether this is due to enhanced fibrinolysis or to circulatory effects of epinephrine, 30 patients scheduled for primary total hip replacement under epidural anesthesia were randomly assigned to receive intravenous infusions of either low dose epinephrine or phenylephrine intraoperatively. All patients received lumbar epidural anesthesia with induced hypotension and were monitored with radial artery and pulmonary artery catheters.Patients receiving low dose epinephrine infusion had maintenance of heart rate and cardiac index whereas both heart rate and cardiac index declined significantly throughout surgery in patients receiving phenylephrine (p = 0.0001 and p = 0.0001, respectively). Tissue plasminogen activator (t-PA) activity increased significantly during surgery (p <0.0005) and declined below baseline postoperatively (p <0.005) in both groups. Low dose epinephrine was not associated with any additional augmentation of fibrinolytic activity perioperatively. There were no significant differences in changes in D-Dimer, t-PA antigen, α2-plasmin inhibitor-plasmin complexes or thrombin-antithrombin III complexes perioperatively between groups receiving low dose epinephrine or phenylephrine. The reduction in deep vein thrombosis rate with low dose epinephrine is more likely mediated by a circulatory mechanism than by augmentation of fibrinolysis.

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Effects on Coagulation and Fibrinolysis of Desmopressin in Patients Undergoing Total Hip Replacement

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646480 ◽

1991 ◽

Vol 66 (06) ◽

pp. 652-656 ◽

Cited By ~ 7

Author(s):

Per Anders Flordal ◽

Karl-Gösta Ljungström ◽

Jan Svensson ◽

Brenda Ekman ◽

Gustaf Neander

Keyword(s):

Total Hip Replacement ◽

Hip Replacement ◽

Bleeding Time ◽

Antithrombin Iii ◽

Postoperative Bleeding ◽

Double Blind ◽

Total Hip ◽

Von Willebrand ◽

Willebrand Factor ◽

Coagulation And Fibrinolysis

SummaryTwelve patients undergoing total hip replacement, with regional anaesthesia and with dextran infusion for plasma expansion and thromboprophylaxis, were given the vasopressin analogue desmopressin (DDAVP) or placebo in a randomized, double-blind prospective study. In controls (n = 6) we found a prolongation of the bleeding time, low factor VIII (FVIII) and von Willebrand factor (vWF) and a decrease in antithrombin III to levels known to be at risk for venous thrombosis. Desmopressin shortened postoperative bleeding time, gave an early FVIII/vWF complex increase, prevented antithrombin III from falling to critically low values and appeared to activate the fibrinolytic system, both by tPA increase and PAI-1 decrease.Thus in the controls we found changes in both coagulation and fibrinolysis indicating a haemorrhagic diathesis as well as a risk for thromboembolism. Desmopressin induced factor changes that possibly reduce both risks.

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Low-Dose Heparin and Deep-Vein Thrombosis after Total Hip Replacement

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648020 ◽

1976 ◽

Vol 36 (01) ◽

pp. 157-164 ◽

Cited By ~ 34

Author(s):

P. M Mannucci ◽

Luisa E. Citterio ◽

N Panajotopoulos

Keyword(s):

Deep Vein Thrombosis ◽

Total Hip Replacement ◽

Hip Replacement ◽

Low Dose ◽

Control Group ◽

Total Hip ◽

Vein Thrombosis ◽

Dose Heparin ◽

Deep Vein ◽

Low Dose Heparin

SummaryThe effect of subcutaneous low-dose heparin on postoperative deep-vein thrombosis (D. V. T.) (diagnosed by the 125I-labelled fibrinogen test) has been investigated in a trial of 143 patients undergoing the operation of total hip replacement. Two randomized studies were carried out: in one the scanning for D.V.T. was carried out daily for 7 days post operatively and in the other for 15 days. In both, the incidence of D.V.T. was significantly lower in the heparin-treated patients (P<0.005). Bilateral D.V.T. was also prevented (P<0.05), through the extension of D.V.T. to the distal veins of the thigh was not significantly reduced. Heparin treatment was, however, followed by a higher incidence of severe postoperative bleeding (P< 0.02) and wound haematoma formation (P< 0.005), and the postoperative haemoglobin was significantly lower than in the control group (P<0.005). A higher number of transfused blood units was also needed by the heparin treated patients (P<0.001).

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