Abstract
BackgroundDespite 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.MethodsIn 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.ResultsThe 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.ConclusionsThe 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.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2474-15-312) contains supplementary material, which is available to authorized users.
Highlights
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
This study aimed to investigate three subjects of hip arthroplasty: 1) the stem-induced stress-shielding effect on the proximal femur, 2) the biomechanical influence of preserving the femoral neck on the proximal femur, and 3) the micromotion difference between the balland neck-shaped cups at the bone-implant interfaces
Femoral model and hip prostheses The pelvis and femur of a 24-year-old male participant without any hip disease were scanned in vivo using computed tomography (CT)
Summary
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. The surgical method of the stemmed THR is to amputate the intact femoral neck entirely, rasp off the intramedullary canal, and evacuate the bone marrow for the stem insertion. Stem insertion into the intramedullary canal necessitates both blood transfusion and bone reaming; and might lead to infection [1,2,3,4,5]. The other is bone loss (osteoporosis) in response with the stress of the proximal femur shielded by the inserted stem [11,12,13,14]. The impingement of the stem end has been reported as the stress raiser that induces bone hypertrophy and even fractures [5]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
