• Hip & pelvis
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• 제34권2호
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• pp.106-114
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• 2022

Purpose: While initial fixation using a press-fit of the acetabular cup is critical for the durability of the component, restoration of the hip center is regarded as an attributable factor for implant survival and successful outcome. In protrusio acetabuli (PA), obtaining both restoration of the hip center and the press-fit of the acetabular cup simultaneously might be difficult during total hip arthroplasty (THA). We tested the hypothesis that use of a medialized cup, if press-fitted, will not result in compromise of the implant stability and outcome after cementless THA of PA. Materials and Methods: A total of 26 cementless THAs of 22 patients with PA were reviewed. During THA, press-fit of the cup was prioritized rather than hip center restoration. A press-fit was obtained in 24 hips. A pressfit could not be obtained in the two remaining hips; therefore, reinforcement acetabular components were used. Restoration of the hip center was achieved in 17 cups; 15 primary cups and two reinforcement components; it was medialized in nine cups. Implant stability and modified Harris hip score (mHHS) between the two groups were compared at a mean follow-up of 5.1 years (range, 2-16 years). Results: Twenty-six cups; 17 restored cups and nine medialized press-fitted cups, remained stable at the latest follow-up. A similar final mHHS was observed between the restored group and the medialized group (83.6±12.1 vs 83.8±10.4, P=0.786). Conclusion: Implant stability and favorable results were obtained by press-fitted cups, irrespective of hip center restoration. THA in PA patients showed promising clinical and radiological results.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1995년도 추계학술대회
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• pp.34-38
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• 1995

Using a 3-D finite element method (FEM), the biomechanical characteristics of a threaded truncated acetabular component and a porous coated hemispherical acetabular component were studied. The Von-Mises stress/strain patterns in the acetabulum reconstructed with these two different types of cementless acetabular cups were investigated. The geometry and dimensions of human hemi-pelvis used in the present shape modeling for finite element analysis were scanned with a 3-D laser scanner(TDS-9000, Cyberware, USA). The scanned data was numerically handled with a shape modelling software 'Pro-Engineer'. Using 19836, 16853 tetrahedral elements, respectively, the stress and displacement field of the acetabulum reconstructed with the two different types of the acetabular components were computed. While the hemi-sphere component was found to show a relatively similar stress/strain patterns to those in the normal hip, the results with the threaded cup showed a considerably different patterns from those in the normal condition. Several regions in cancellous bone near the threads and the edge of the truncated cup was found to be overstressed, especially in the superior-lateral part of the acetabulum. It was postulated that the excessive reaming-out of subchondral bone layer when the truncated cup was used can cause the presence of these overstressed regions of cancellous bone. This theoretical prediction for the implanted acetabulum appeared to consistent with the pathological observation of proximal/medial migration of the threaded truncated acetabular prostheses in the previous publications.