Wear of composite ceramics in mixed-material combinations in total hip replacement under adverse edge loading conditions

Edge-loading of a ceramic-on-ceramic total hip replacement can lead to reproducible squeaking and revision. A patient’s functional acetabular cup orientation, driven by their pelvic tilt, has been shown to be a significant factor in squeaking during hip flexion. The aim of this study was to investigate the effect of seated pelvic tilt on the contact mechanics at the ceramic bearing surface. A finite element model of a ceramic-on-ceramic total hip replacement was created. The cup was orientated at 40° inclination and 15° anteversion relative to the anterior pelvic plane. The stem was flexed 90° to replicate sitting in a chair. The model was loaded using data from in vivo measurements taken during a sit-to-stand activity. The pelvis was modelled in seven different sagittal positions, ranging from −30° to 30° of pelvic tilt, where a positive value denotes anterior pelvic tilt. Three different head sizes were investigated: 32, 36 and 40 mm. The maximum contact pressure and contact patch to rim distance were determined for each of the 21 simulations. Edge-loading (contact patch to rim distance < 0 mm) occurred with all head sizes when seated pelvic tilt was ≥10° and induced a large increase in contact pressure on the liner, with a maximum pressure exceeding 500 MPa. Edge-loading initiated at seated pelvic tilts of 7°, 9° and 5° for the 32, 36 and 40 mm heads, respectively. Patients with anterior pelvic tilts in the seated position are susceptible to posterior edge-loading. As the position of the pelvis when seated is patient specific, cup orientation should be adjusted on an individual basis to minimise edge-loading.

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The contact mechanics and occurrence of edge loading in modular metal-on-polyethylene total hip replacement during daily activities

Medical Engineering & Physics ◽

10.1016/j.medengphy.2016.03.004 ◽

2016 ◽

Vol 38 (6) ◽

pp. 518-525 ◽

Cited By ~ 20

Author(s):

Xijin Hua ◽

Junyan Li ◽

Zhongmin Jin ◽

John Fisher

Keyword(s):

Contact Mechanics ◽

Total Hip Replacement ◽

Hip Replacement ◽

Daily Activities ◽

Total Hip ◽

Edge Loading

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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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