Contact mechanics of modular metal-on-polyethylene 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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Anatomical modelling and simplified modelling in total hip replacement: difference in contact mechanics perspective

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/834/1/012064 ◽

2020 ◽

Vol 834 ◽

pp. 012064

Author(s):

M F A Manap ◽

S Shuib ◽

A F M Yamin ◽

A A Shokri

Keyword(s):

Contact Mechanics ◽

Total Hip Replacement ◽

Hip Replacement ◽

Total Hip

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Comparison of Contact Mechanics between a Total Hip Replacement and a Hip Resurfacing with a Metal-On-Metal Articulation

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1243/095440605x31490 ◽

2005 ◽

Vol 219 (7) ◽

pp. 727-732 ◽

Cited By ~ 23

Author(s):

F Liu ◽

I. J. Udofia ◽

Z. M. Jin ◽

F Hirt ◽

C Rieker ◽

...

Keyword(s):

Contact Mechanics ◽

Contact Pressure ◽

Total Hip Replacement ◽

Contact Area ◽

Hip Replacement ◽

Clinical Success ◽

Three Dimensional ◽

Hip Resurfacing ◽

Total Hip ◽

Metal On Metal

The finite element method was employed in this study to compare the contact mechanics at the bearing surfaces between a metal-on-metal hip resurfacing prosthesis and a total hip replacement with a similar bearing combination. The hip resurfacing prosthesis was implanted and modelled in a full three-dimensional pelvic and femoral bone. A significant reduction in the predicted contact pressure by over 53 per cent as well as a corresponding increase in the contact area by approximately 220 per cent was found in the hip resurfacing prosthesis, in comparison to the total hip replacement. The reduced contact pressure and increased contact area in the hip resurfacing system were due to the combination of the larger bearing size and increased elasticity from the metallic cup and the underlying bone support. The hip resurfacing prosthesis may therefore offer a significant improvement in the tribology at the metallic bearing surfaces, thus offering a potential advantage in terms of long-term clinical success over current total hip replacements with reported survivorships over 20 years.

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