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Effects of stemmed and nonstemmed hip replacement on stress distribution of proximal femur and implant.

Chen CM, Tsai WC, Lin SC, Tseng CS - BMC Musculoskelet Disord (2014)

Bottom Line: The results showed that stress distributions of the two nonstemmed femora are consistently more similar to the intact femur than the stemmed one.The fitting system with the anatomy-shaped cup can make intimate contact with the neck cortex and reduce the bone-cup micromotion and the implant stress.The reserved femoral neck could act as the load-transferring medium from the acetabular cup, femoral neck, to the diaphysial bone, thus depressing the stress-shielding effect below the neck region.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Biomedical Engineering, National Taiwan University of Science and Technology, No, 43, Sec, 4, Keelung Rd, Taipei 106, Taiwan. orthodent.cax@gmail.com.

ABSTRACT

Background: Despite improvements in shape, material, and coating for hip stem, both stress shielding and aseptic loosening have been the major drawbacks of stemmed hip arthroplasty. Some nonstemmed systems were developed to avoid rasping off the intramedullary canal and evacuating the bone marrow due to stem insertion.

Methods: In this study, the finite-element models of one intact, one stemmed, and two nonstemmed femora with minimal removal of the healthy neck were investigated to evaluate their biomechanical effects. The resurfacing (ball-shaped) and fitting (neck-shaped) systems were respectively selected as the representative of the ready- and custom-made nonstemmed implants. The stress distribution and interface micromotion were selected as the comparison indices.

Results: The results showed that stress distributions of the two nonstemmed femora are consistently more similar to the intact femur than the stemmed one. Around the proximal femur, the stem definitely induces the stress-shielding phenomenon of its counterparts. The fitting system with the anatomy-shaped cup can make intimate contact with the neck cortex and reduce the bone-cup micromotion and the implant stress. Comparatively, the reamed femoral head provides weaker support to the resurfacing cup causing higher interfacial micromotion.

Conclusions: The reserved femoral neck could act as the load-transferring medium from the acetabular cup, femoral neck, to the diaphysial bone, thus depressing the stress-shielding effect below the neck region. If the hip-cup construct can be definitely stabilized, the nonstemmed design could be an alternative of hip arthroplasty for the younger or the specific patients with the disease limited only to the femoral head.

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Related in: MedlinePlus

Interfacial micromotion of the two nonstemmed systems along the two interface lines. The cup and bone surfaces denoted as the line on the cup interior and bone exterior, respectively. (A) Resurfacing system. (B) Fitting system.
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Fig4: Interfacial micromotion of the two nonstemmed systems along the two interface lines. The cup and bone surfaces denoted as the line on the cup interior and bone exterior, respectively. (A) Resurfacing system. (B) Fitting system.

Mentions: Upon loading, the interfacial micromotion results in the gap between the resurfacing cup and reamed femur, except for the plateau (Figure 4A). Above the central bar, the micromotion along line ii was on average 0.06 mm. Comparatively, the fitting system seems to be more stable in response to the result that the interfacial micromotion is mostly exhibited along the upper line hh (Figure 4B). For the two nonstemmed systems, the interfacial micromotion always occurs along the inferior portion of the two interface lines. Below the plateau, the micromotion value of the fitting system was somewhat smaller than that of the resurfacing system.Figure 4


Effects of stemmed and nonstemmed hip replacement on stress distribution of proximal femur and implant.

Chen CM, Tsai WC, Lin SC, Tseng CS - BMC Musculoskelet Disord (2014)

Interfacial micromotion of the two nonstemmed systems along the two interface lines. The cup and bone surfaces denoted as the line on the cup interior and bone exterior, respectively. (A) Resurfacing system. (B) Fitting system.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4197382&req=5

Fig4: Interfacial micromotion of the two nonstemmed systems along the two interface lines. The cup and bone surfaces denoted as the line on the cup interior and bone exterior, respectively. (A) Resurfacing system. (B) Fitting system.
Mentions: Upon loading, the interfacial micromotion results in the gap between the resurfacing cup and reamed femur, except for the plateau (Figure 4A). Above the central bar, the micromotion along line ii was on average 0.06 mm. Comparatively, the fitting system seems to be more stable in response to the result that the interfacial micromotion is mostly exhibited along the upper line hh (Figure 4B). For the two nonstemmed systems, the interfacial micromotion always occurs along the inferior portion of the two interface lines. Below the plateau, the micromotion value of the fitting system was somewhat smaller than that of the resurfacing system.Figure 4

Bottom Line: The results showed that stress distributions of the two nonstemmed femora are consistently more similar to the intact femur than the stemmed one.The fitting system with the anatomy-shaped cup can make intimate contact with the neck cortex and reduce the bone-cup micromotion and the implant stress.The reserved femoral neck could act as the load-transferring medium from the acetabular cup, femoral neck, to the diaphysial bone, thus depressing the stress-shielding effect below the neck region.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Biomedical Engineering, National Taiwan University of Science and Technology, No, 43, Sec, 4, Keelung Rd, Taipei 106, Taiwan. orthodent.cax@gmail.com.

ABSTRACT

Background: Despite improvements in shape, material, and coating for hip stem, both stress shielding and aseptic loosening have been the major drawbacks of stemmed hip arthroplasty. Some nonstemmed systems were developed to avoid rasping off the intramedullary canal and evacuating the bone marrow due to stem insertion.

Methods: In this study, the finite-element models of one intact, one stemmed, and two nonstemmed femora with minimal removal of the healthy neck were investigated to evaluate their biomechanical effects. The resurfacing (ball-shaped) and fitting (neck-shaped) systems were respectively selected as the representative of the ready- and custom-made nonstemmed implants. The stress distribution and interface micromotion were selected as the comparison indices.

Results: The results showed that stress distributions of the two nonstemmed femora are consistently more similar to the intact femur than the stemmed one. Around the proximal femur, the stem definitely induces the stress-shielding phenomenon of its counterparts. The fitting system with the anatomy-shaped cup can make intimate contact with the neck cortex and reduce the bone-cup micromotion and the implant stress. Comparatively, the reamed femoral head provides weaker support to the resurfacing cup causing higher interfacial micromotion.

Conclusions: The reserved femoral neck could act as the load-transferring medium from the acetabular cup, femoral neck, to the diaphysial bone, thus depressing the stress-shielding effect below the neck region. If the hip-cup construct can be definitely stabilized, the nonstemmed design could be an alternative of hip arthroplasty for the younger or the specific patients with the disease limited only to the femoral head.

Show MeSH
Related in: MedlinePlus