Reversed anisotropies and thermal contraction of FCC (110) surfaces

The observed anisotropies of surface vibrations for unreconstructed FCC metal (110) surfaces are often reversed from the "common sense" expectation. The source of these reversals is investigated by performing ab initio density functional theory calculations to obtain the surface force constant tensors for Ag(110), Cu(110) and Al(110). The most striking result is a large enhancement in the coupling between the first and third layers of the relaxed surface, which strongly reduces the amplitude of out-of-plane vibrations of atoms in the first layer. This also provides a simple explanation for the thermal contraction of interlayer distances. Both the anisotropies and the thermal contraction arise primarily as a result of the bond topology, with all three (110) surfaces showing similar behavior.Comment: 13 pages, in revtex format, plus 1 postscript figur

Acetabular reconstruction with impaction bone-grafting and a cemented cup in patients younger than fifty years old.

Contains fulltext : 57643.pdf (publisher's version ) (Open Access)BACKGROUND: Acetabular bone deficiency can present a challenge during total hip arthroplasty, especially in young patients. The purpose of the present study was to evaluate the long-term clinical and radiographic outcomes of primary and revision acetabular reconstruction with use of an impaction bone-grafting technique and a cemented polyethylene cup in young patients who had preexisting acetabular bone deficiency. METHODS: Forty-two consecutive acetabular reconstructions were performed in thirty-seven patients who were younger than fifty years old (average, 37.2 years old). The impaction bone-grafting technique was used for twenty-three primary and nineteen revision acetabular reconstructions. Twenty-eight patients (thirty-one hips) were available for review after a minimum duration of follow-up of fifteen years. Clinical and radiographic results were assessed, and survivorship analysis was performed with the Kaplan-Meier method. RESULTS: Eight hips were revised at a mean of twelve years (range, three to twenty-one years) after a primary reconstruction (four hips) or revision reconstruction (four hips). The revision was performed because of aseptic loosening of the acetabular component in four hips and because of culture-proven septic loosening in two. Two additional cups (both in hips that had had a revision reconstruction) were revised, during revision of the femoral stem, because of wear (one hip) or because of persistent intraoperative instability (one hip). Twenty-eight hips (in twenty-five patients) had retention of the acetabular component for a minimum of fifteen years. The mean Harris hip score for that group was 89 points. Twenty-six of these twenty-eight hips had no or slight pain. Kaplan-Meier analysis revealed a twenty-year survival rate of 80% (95% confidence interval, 67% to 94%) with acetabular revision for any reason as the end point and of 91% (95% confidence interval, 80% to 100%) with acetabular revision because of aseptic loosening as the end point. CONCLUSIONS: Acetabular reconstruction with use of impaction bone-grafting and a cemented polyethylene cup is a reliable and durable technique that is associated with good long-term results in young patients with acetabular bone-stock defects

[Choice of hip prosthesis in patients younger than 50 years]

There is no agreement about the most ideal type of hip prosthesis to be used in patients younger than 50 years. The most commonly used hip prostheses in patients younger than 50 years are uncemented or resurfacing prostheses and to a lesser extent cemented prostheses. A good result of a hip prosthesis can be defined as follows: 10 years after surgery more than 90% of the prostheses should be still in situ during endpoint revision for any reason. No trials are available comparing cemented, uncemented or resurfacing hip prostheses. Studies are available of cemented hip prostheses in patients younger than 50 years that prove that more than 90% of the hips are still in situ after 50 years. There are no studies available of uncemented or resurfacing hip prostheses in younger patients that prove that after to years of follow-up 90% or more of the prostheses are still in situ. The Scandinavian hip registers show that the highest rate of prostheses still in situ after 10 years is achieved by cemented hip prostheses

[Choice of hip prosthesis in patients younger than 50 years],Keuze van heupprothese voor patiënten jonger dan 50 jaar.

Item does not contain fulltextThere is no agreement about the most ideal type of hip prosthesis to be used in patients younger than 50 years. The most commonly used hip prostheses in patients younger than 50 years are uncemented or resurfacing prostheses and to a lesser extent cemented prostheses. A good result of a hip prosthesis can be defined as follows: 10 years after surgery more than 90% of the prostheses should be still in situ during endpoint revision for any reason. No trials are available comparing cemented, uncemented or resurfacing hip prostheses. Studies are available of cemented hip prostheses in patients younger than 50 years that prove that more than 90% of the hips are still in situ after 50 years. There are no studies available of uncemented or resurfacing hip prostheses in younger patients that prove that after to years of follow-up 90% or more of the prostheses are still in situ. The Scandinavian hip registers show that the highest rate of prostheses still in situ after 10 years is achieved by cemented hip prostheses

[Favourable long-term results from cemented total hip arthroplasty combined with acetabular bone impaction grafting in patients under the age of 50],Goede langetermijnresultaten van een gecementeerde totaleheupprothese in combinatie met een acetabulumreconstructie met geïmpacteerde botsnippers bij patïenten jonger dan 50 jaar.

Contains fulltext : 53064.pdf (publisher's version ) (Closed access)OBJECTIVE: Determination of long-term results of hip replacements in patients who, at the time of operation, were under the age of 50. Procedures whereby an existing acetabulum defect was filled with bone chips that were impacted into a strong layer, after which a cemented total hip prosthesis was implanted. DESIGN: Descriptive. METHOD: Prospectively collected data from patients who were under the age of 50, and had undergone a hip replacement operation at our hospital between 1 July 1979 and 31 December 1987 were analysed. Data were collected up to 31 December 2002. The main outcome was time to revision. Survival was calculated by the Kaplan-Meier method. RESULTS: The study group consisted of 25 patients, 17 women and 8 men with 29 prosthetic hips. The average age at operation was 37.6 years (range: 20-49). Follow-up time was 15-23 years (median: 18.7 years). 1 patient (1 hip) was lost to follow-up. 3 patients (4 hips) died within 15 years after the operation; none of them had undergone revision. 4 revisions had been performed: I septic loosening (14 years p.o.) and 3 aseptic loosenings (6, 15, 20 years p.o.). The cumulative survival with the end-point 'revision for any reason' was 96% (95% CI: 88-100) at to years and 88% (95% CI: 74-100) at 20 years; after exclusion of the septic loosening the survival at 20 years was 92% (95% CI: 80-100). CONCLUSION: Hip replacement including a reconstruction technique for an acetabulum defect in patients under the age of 50 was regarded as successful if after 10 years, at least 90% of the prostheses were still in situ

Acetabular reconstruction with impaction bone-grafting and a cemented cup in patients younger than fifty years old: a concise follow-up, at twenty to twenty-eight years, of a previous report

Item does not contain fulltextIn a previous report, we presented our results of forty-two acetabular reconstructions, performed with use of impaction bone-grafting and a cemented polyethylene cup, in thirty-seven patients who were younger than fifty years and had a minimum of fifteen years of follow-up. The present update study shows the results after twenty to twenty-eight years. Eight additional cups had to be revised--four because of aseptic loosening, three because of wear, and one during a revision of the stem. Three additional cups were considered loose on radiographs. Survivorship of the acetabular reconstructions, with an end point of revision for any reason, was 73% after twenty years and 52% after twenty-five years. With revision for aseptic loosening as the end point, survival was 85% after twenty years and 77% after twenty-five years; for signs of loosening on radiographs, survival was 71% at twenty years and 62% at twenty-five years. In conclusion, our previous results have declined but the technique of using impacted morselized bone graft and a cemented cup is useful for the purpose of restoring bone stock in young patients whose acetabular defects require primary or revision total hip arthroplasty

[Favourable long-term results from cemented total hip arthroplasty combined with acetabular bone impaction grafting in patients under the age of 50]

OBJECTIVE: Determination of long-term results of hip replacements in patients who, at the time of operation, were under the age of 50. Procedures whereby an existing acetabulum defect was filled with bone chips that were impacted into a strong layer, after which a cemented total hip prosthesis was implanted. DESIGN: Descriptive. METHOD: Prospectively collected data from patients who were under the age of 50, and had undergone a hip replacement operation at our hospital between 1 July 1979 and 31 December 1987 were analysed. Data were collected up to 31 December 2002. The main outcome was time to revision. Survival was calculated by the Kaplan-Meier method. RESULTS: The study group consisted of 25 patients, 17 women and 8 men with 29 prosthetic hips. The average age at operation was 37.6 years (range: 20-49). Follow-up time was 15-23 years (median: 18.7 years). 1 patient (1 hip) was lost to follow-up. 3 patients (4 hips) died within 15 years after the operation; none of them had undergone revision. 4 revisions had been performed: I septic loosening (14 years p.o.) and 3 aseptic loosenings (6, 15, 20 years p.o.). The cumulative survival with the end-point 'revision for any reason' was 96% (95% CI: 88-100) at to years and 88% (95% CI: 74-100) at 20 years; after exclusion of the septic loosening the survival at 20 years was 92% (95% CI: 80-100). CONCLUSION: Hip replacement including a reconstruction technique for an acetabulum defect in patients under the age of 50 was regarded as successful if after 10 years, at least 90% of the prostheses were still in situ

A cemented cup with acetabular impaction bone grafting is more cost-effective than an uncemented cup in patients under 50 years

PURPOSE: Acetabular deficiencies in young patients can be restored in several ways during total hip arthroplasty. Currently, cementless cups are most frequently used. Impaction bone grafting of acetabular defects is a more biological approach, but is it cost-effective in young patients on the long term? METHODS: We designed a decision model for a cost-utility analysis of a cemented cup with acetabular impaction bone grafting versus an uncemented cup, in terms of cost per quality-adjusted life year (QALY) for the young adult with acetabular bone deficiency, in need for a primary total hip arthroplasty. Outcome probabilities and effectiveness were derived from the Radboud University Nijmegen Medical Centre and the Norwegian Hip Register. Multiple sensitivity analyses were used to assess the contribution of the included variables in the model's outcome. RESULTS: Cemented cups with impaction bone grafting were more cost-effective compared to the uncemented option in terms of costs per QALY. A scenario suggesting equal primary survival rates of both cemented and uncemented cups still showed an effect gain of the cemented cup with impaction bone grafting, but at higher costs. CONCLUSIONS: Based on this model, the first choice of treatment of the acetabular bone deficient osteoarthritic hip in a young patient is reconstruction with impaction bone grafting and a cemented cup