Press-fit acetabular cup fixation: Principles and testing

Macdonald, Warren; Carlsson, Lars; Charnley, G.J.; Jacobsson, Catharina

doi:10.1243/0954411991534780

Cited by 49 publications

(52 citation statements)

References 11 publications

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“…Moreover, the primary stability was evaluated using a tangential pull-out test, which has the advantage of being adapted to the configuration of this cadaveric study [10, 15, 29]. The values of stability were obtained in the range [0–140 N] which is in agreement with the range found in the literature [1, 30, 31]. The implant stability also depends on the sinking relative to the edges of the cup because a cup in a coxa profunda is different from a cup implanted in hip dysplasia, where a part of the wall may be discovered [32].…”

Section: Discussionsupporting

confidence: 75%

Assessing the Acetabular Cup Implant Primary Stability by Impact Analyses: A Cadaveric Study

et al. 2016

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BackgroundThe primary stability of the acetabular cup (AC) implant is an important determinant for the long term success of cementless hip surgery. However, it remains difficult to assess the AC implant stability due to the complex nature of the bone-implant interface. A compromise should be found when inserting the AC implant in order to obtain a sufficient implant stability without risking bone fracture. The aim of this study is to evaluate the potential of impact signals analyses to assess the primary stability of AC implants inserted in cadaveric specimens.MethodsAC implants with various sizes were inserted in 12 cadaveric hips following the same protocol as the one employed in the clinic, leading to 86 different configurations. A hammer instrumented with a piezoelectric force sensor was then used to measure the variation of the force as a function of time produced during the impact between the hammer and the ancillary. Then, an indicator I was determined for each impact based on the impact momentum. For each configuration, twelve impacts were realized with the hammer, the value of the maximum amplitude being comprised between 2500 and 4500 N, which allows to determine an averaged value IM of the indicator for each configuration. The pull-out force F was measured using a tangential pull-out biomechanical test.ResultsA significant correlation (R2 = 0.69) was found between IM and F when pooling all data, which indicates that information related to the AC implant biomechanical stability can be retrieved from the analysis of impact signals obtained in cadavers.ConclusionThese results open new paths in the development of a medical device that could be used in the future in the operative room to help orthopedic surgeons adapt the surgical protocol in a patient specific manner.

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Section: Discussionsupporting

confidence: 75%

Assessing the Acetabular Cup Implant Primary Stability by Impact Analyses: A Cadaveric Study

et al. 2016

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“…Second, these foam blocks are commonly used to model the acetabulum in similar studies. [13][14][15][16][17] Two different acetabular cavity geometries were machined using foam blocks comprising both densities. The first geometry was a 1-mm under-reamed hemispherical cavity (high-density spherical and low-density spherical).…”

Section: Acetabular Modelmentioning

confidence: 99%

A novel method to assess primary stability of press-fit acetabular cups

Crosnier

Keogh

Miles

2014

Proc Inst Mech Eng H

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Initial stability is an essential prerequisite to achieve osseointegration of press-fit acetabular cups in total hip replacements. Most in vitro methods that assess cup stability do not reproduce physiological loading conditions and use simplified acetabular models with a spherical cavity. The aim of this study was to investigate the effect of bone density and acetabular geometry on cup stability using a novel method for measuring acetabular cup micromotion. A press-fit cup was inserted into Sawbones(®) foam blocks having different densities to simulate normal and osteoporotic bone variations and different acetabular geometries. The stability of the cup was assessed in two ways: (a) measurement of micromotion of the cup in 6 degrees of freedom under physiological loading and (b) uniaxial push-out tests. The results indicate that changes in bone substrate density and acetabular geometry affect the stability of press-fit acetabular cups. They also suggest that cups implanted into weaker, for example, osteoporotic, bone are subjected to higher levels of micromotion and are therefore more prone to loosening. The decrease in stability of the cup in the physiological model suggests that using simplified spherical cavities to model the acetabulum over-estimates the initial stability of press-fit cups. This novel testing method should provide the basis for a more representative protocol for future pre-clinical evaluation of new acetabular cup designs.

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“…The dual geometry is inherently stable under all loading modes (Macdonald et al 1999a) and, in combination with specially developed reamers, enables more accurate cavity reaming (Macdonald et al 1999b) and intimate contact on implantation. The modified thread form enables progressive tightening of the fixation and enhanced torsional resistance and avoids stress protection at the dome and stress concentration at the thread edges.…”

Section: Rotation (°)mentioning

confidence: 99%