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At least 451 records · Page 25Linked to original sources

PubMed1997

[Experimental protocol for mechanical characterization of a femoral implant of carbon-Peek composite hip prosthesis in fatigue].

This study concerns the fatigue behavior of a C/Peek hip implant. It is now well-established that the extent of bone loss around a total hip arthroplasty stem is related to stress shielding process. Due to a modulus mismatch between the bone and the implant material, the load transfer to the stem decreases the mechanical stimulus needed by the bone to maintain its structure. Because of its low modulus of elasticity and its good resistance to fatigue in aeronautical applications, the Fiber Carbon/Peek composite could potentially replace some of the metal alloys used in hip stem implant. After a literature survey on biomechanical performances of some fiber carbon composites, including AS4/Peek, experimental quasi-static and fatigue compression tests have been performed on AS4/Peek hip implants. The structural and mechanical characterization of the injection moulded composite material has been realized. The prosthesis compression and fatigue behaviour have been studied with a joint-stimulating apparatus immersed in a physiological solution temperature controlled. Instead of the low specimen homogeneity, no fatigue damage has been revealed either by X-ray observations of stiffness measurements, till ten millions of cycles. The quasi-static compressive fracture morphology has been analyzed by S.E.M. and have shown a good fiber matrix bonding. This mechanical results would suggest that AS4/Peek hip stem are worthy of further investigation as implantable prostheses.

Biomechanical Phenomena↗

PubMed1976

Evaluation of a bioglass-coated Al2O3 total hip prosthesis in sheep.

A bioglass-coated fully dense alumina total hip was evaluated in sheep without using polymer bone "cement." After 3 months following surgery, both the acetabular cup and femoral stem component were firmly attached to bone. Histologic and radiographic analysis of the bone-implant interface showed regions of woven and even lamellar bone formation where high load transmission occurred. In regions of low loading or poor fit, a pseudosynovial fibrous lining was present.

Acetabulum↗

PubMed1997

[Radiological evaluation of integration of bone grafts and bone substitutes after implantation to replace acetabular substance losses in reoperation of total hip prosthesis].

Plain radiograms are insufficient to evaluate the integrity of a graft used to replace acetabular tissue loss in reoperations for total hip replacement. The aim of this work was to compare radiographic, computed tomographic and magnetic resonance imaging findings. Two groups of patients including 12 hip joints in each were evaluated 5 years after undergoing reoperation for annular support. Allografts (5 cases) or xenografts (7 cases) were used in one group. Plain radiograms. CT-scan and MRI were performed in each patient. The graft-receiver bone borders were visible on the CT-scans but were not distinguishable on the radiograms. Bone and graft density and structure in contact with the implant could be determined on the CT-scan. MRI was difficult to interpret in most cases due to implant-induced artefacts and is not recommended in this type of reconstruction.

Adult↗

PubMed1997

[Reoperations of total hip prosthesis with acetabular reconstruction using bone allografts].

Detachment of the acetabular segment is the most important long-term problem with total hip prostheses. We analyzed long-term outcome in our first 48 acetabular reconstructions with cryopreserved allografts. Among the 48 hips operated on with this technique, 38 were reassessed after a mean follow-up of 7 years 3 months (range 5 years-9 years 6 months). Mean age of the population at surgery was 63 years. There were two predominant etiologies: sequelae of chronic hip luxation and primary osteoarthrosis of the hip. In 10 cases with massive destruction, the Müller ring was used to stabilize the allograft. Results were assessed at 6 months, 2 years, 4 years and at longest follow-up using the Merle d'Aubigné clinical assessment scale. For the radiographic assessment, the Ranawat criteria were used to evaluate the alignment of the reconstruction. Clinically, patient comfort was improved in all cases with significant pain relief. Radiologically, mean acetabular ascention was 5 mm and mean medialization was 3.5 mm. A rim was observed in 24 cases including 19 measuring less than 2 cm. Acetabular loosening was evidenced in the 5 other cases where the rim measured more than 2 mm. In 4 of these 5 cases, the acetabulum had migrated to a new setting. The radiographic image then remained unchanged. Analysis of our 38 first cases showed that bone allografts with cimented acetabulum, sometimes with a stabilizing ring, is one of the possible solutions for difficult acetabular reconstructions. However, after a 7 years 3 months follow-up, we have had five (13%) aseptic displacements including one case requiring reoperation. In the 33 stable joints (87%) with good results reconstruction has achieved a nearly perfect anatomic position, similar to first intention arthroplasty with the use of perfectly stabilized bone grafts with a maximal acetabular surface. Our follow-up is longer than most published in the literature. However, the migration rate of 13% it is still too short to draw any conclusion concerning the long-term outcome in our patients, despite their older age and reduced physical activity compared with primary hip arthroplasty patients.

Adult↗

PubMed1980