THE EFFECT OF ASPHERICITY OF ACETABULAR BEARING SURFACE ON CONTACT MECHANICS OF UHMWPE TOTAL HIP IMPLANTS BY FINITE ELEMENT ANALYSIS

Asphericity and out-of-roundness are generally used to evaluate the manufacturing quality of ultra-high molecular weight polyethylene (UHMWPE) cup inner surfaces, which can potentially affect initial clinical wear and contribute to osteolysis of total hip arthroplasty. This study measured the location and magnitude of asphericity and the out-of-roundness value for four UHMWPE cups in a single set, and then investigated the effects of the asphericity on the contact mechanics of UHMWPE cups. A co-ordinate measuring machine (CMM) was used for the surface measurement and finite element analysis (FEA) was adopted for contact mechanics study. The results demonstrated that the asphericity varied between cups with the maximum value as 0.088[Formula: see text][Formula: see text][Formula: see text]0.004[Formula: see text]mm. Although such a value met the ISO specification, large difference of volume appeared for the asphericity above 0.060[Formula: see text]mm. Actual surface profile accounting for the asphericity was found to affect the value of contact pressure and contact area by around 12%. The inferior asphericity resulted in a nonsmoothly distributed contact pressure, which had a negative effect on the contact mechanics of UHMWPE cups and the edge loading was predicted to occur for the sample with a large asphericity. In conclusion, the asphericity of UHMWPE cup could affect the contact mechanics of the articular bearings and may subsequently contribute to initial wear during bedding-in phase.

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The effect of complete radial lateral meniscus posterior root tear on the knee contact mechanics: a finite element analysis

Journal of Orthopaedic Science ◽

10.1007/s00776-012-0334-5 ◽

2013 ◽

Vol 18 (2) ◽

pp. 256-263 ◽

Cited By ~ 35

Author(s):

H.R.C. Bao ◽

D. Zhu ◽

G.S. Gu ◽

H. Gong

Keyword(s):

Finite Element Analysis ◽

Finite Element ◽

Contact Mechanics ◽

Lateral Meniscus ◽

Posterior Root ◽

Root Tear ◽

Element Analysis ◽

Posterior Root Tear

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Axisymmetric Finite Element Analysis of a Debonded Total Hip Stem With an Unsupported Distal Tip

Journal of Biomechanical Engineering ◽

10.1115/1.2796023 ◽

1996 ◽

Vol 118 (3) ◽

pp. 399-404 ◽

Cited By ~ 12

Author(s):

T. L Norman ◽

V. C. Saligrama ◽

K. T. Hustosky ◽

T. A. Gruen ◽

J. D. Blaha

Keyword(s):

Finite Element Analysis ◽

Finite Element ◽

Stress Relaxation ◽

Bone Cement ◽

Cement Mantle ◽

Load Level ◽

Interface Conditions ◽

Element Analysis ◽

Cement Interface ◽

Total Hip

A tapered femoral total hip stem with a debonded stem-cement interface and an unsupported distal tip subjected to constant axial load was evaluated using two-dimensional (2D) axisymmetric finite element analysis. The analysis was performed to test if the mechanical condition suggest that a “taper-lock” with a debonded viscoelastic bone cement might be an alternative approach to cement fixation of stem type cemented hip prosthesis. Effect of stem-cement interface conditions (bonded, debonded with and without friction) and viscoelastic response (creep and relaxation) of acrylic bone cement on cement mantle stresses and axial displacement of the stem was also investigated. Stem debonding with friction increased maximum cement von Mises stress by approximately 50 percent when compared to the bonded stem. Of the stress components in the cement mantle, radial stresses were compressive and hoop stresses were tensile and were indicative of mechanical taper-lock. Cement mantle stress, creep and stress relaxation and stem displacement increased with increasing load level and with decreasing stem-cement interface friction. Stress relaxation occur predominately in tensile hoop stress and decreased from 1 to 46 percent over the conditions considered. Stem displacement due to cement mantle creep ranged from 614 μm to 1.3 μm in 24 hours depending upon interface conditions and load level.

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Effect of coronal plane acetabular correction on joint contact pressure in Periacetabular osteotomy: a finite-element analysis

BMC Musculoskeletal Disorders ◽

10.1186/s12891-022-05005-5 ◽

2022 ◽

Vol 23 (1) ◽

Author(s):

Kenji Kitamura ◽

Masanori Fujii ◽

Miho Iwamoto ◽

Satoshi Ikemura ◽

Satoshi Hamai ◽

...

Keyword(s):

Finite Element Analysis ◽

Finite Element ◽

Contact Pressure ◽

Periacetabular Osteotomy ◽

Anterior Wall ◽

Coronal Plane ◽

Patient Specific ◽

Element Analysis ◽

Joint Contact ◽

Joint Contact Pressure

Abstract Background The ideal acetabular position for optimizing hip joint biomechanics in periacetabular osteotomy (PAO) remains unclear. We aimed to determine the relationship between acetabular correction in the coronal plane and joint contact pressure (CP) and identify morphological factors associated with residual abnormal CP after correction. Methods Using CT images from 44 patients with hip dysplasia, we performed three patterns of virtual PAOs on patient-specific 3D hip models; the acetabulum was rotated laterally to the lateral center-edge angles (LCEA) of 30°, 35°, and 40°. Finite-element analysis was used to calculate the CP of the acetabular cartilage during a single-leg stance. Results Coronal correction to the LCEA of 30° decreased the median maximum CP 0.5-fold compared to preoperatively (p < 0.001). Additional correction to the LCEA of 40° further decreased CP in 15 hips (34%) but conversely increased CP in 29 hips (66%). The increase in CP was associated with greater preoperative extrusion index (p = 0.030) and roundness index (p = 0.038). Overall, virtual PAO failed to normalize CP in 11 hips (25%), and a small anterior wall index (p = 0.049) and a large roundness index (p = 0.003) were associated with residual abnormal CP. Conclusions The degree of acetabular correction in the coronal plane where CP is minimized varied among patients. Coronal plane correction alone failed to normalize CP in 25% of patients in this study. In patients with an anterior acetabular deficiency (anterior wall index < 0.21) and an aspherical femoral head (roundness index > 53.2%), coronal plane correction alone may not normalize CP. Further studies are needed to clarify the effectiveness of multiplanar correction, including in the sagittal and axial planes, in optimizing the hip joint’s contact mechanics.

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