Surfaces In Total Hip Arthroplasty Research Articles

Use of Cost-Effectiveness Analysis to Evaluate New Technologies in Orthopaedics: The Case of Alternative Bearing Surfaces in Total Hip Arthroplasty

Use of Cost-Effectiveness Analysis to Evaluate New Technologies in Orthopaedics: The Case of Alternative Bearing Surfaces in Total Hip Arthroplasty

Metal-on-Metal Hybrid Surface Arthroplasty

Following the reintroduction of metal-on-metal articulating surfaces for total hip arthroplasty in Europe in 1988, we developed a surface arthroplasty prosthetic system using a metal-on-metal articulation. The present study describes the clinical and radiographic results of the first 400 hips treated with metal-on-metal hybrid surface arthroplasties at an average follow-up of three and a half years. Between November 1996 and November 2000, 400 metal-on-metal hybrid surface arthroplasties were performed in 355 patients. All femoral head components were cemented, but only fifty-nine of the short metaphyseal stems were cemented. The patients had an average age of forty-eight years, 73% were men, and 66% had a diagnosis of osteoarthritis. Clinical and radiographic follow-up was performed at three months postoperatively and yearly thereafter. The majority of the patients returned to a high level of activity, including sports, and 54% had activity scores of >7 on the University of California at Los Angeles activity assessment system. Kaplan-Meier survivorship curves demonstrated that the rate of survival of the components at four years was 94.4%. For patients with a surface arthroplasty risk index score of >3, the rate of survival of the components at four years was 89% compared with a rate of 97% for those with a score of <or=3. The patients with a higher risk index were 4.2 times more likely to undergo revision to a total hip replacement at four years. Twelve hips (3%) had a revision to a total hip replacement. Seven of the twelve hips were revised because of loosening of the femoral component, and three were revised because of a femoral neck fracture. Substantial radiolucencies were seen around sixteen uncemented metaphyseal femoral stems. No femoral radiolucencies were observed among the hips in which the metaphyseal stem was cemented. The most important risk factors for femoral component loosening and substantial stem radiolucencies were large femoral head cysts (p = 0.029), patient height (p = 0.032), female gender (p = 0.005), and smaller component size in male patients (p = 0.005). The preliminary experience with this hybrid metal-on-metal bearing is encouraging. Optimal femoral bone preparation and component fixation are critical to improving durability. The metal-on-metal hybrid surface arthroplasty is easily revised to a standard femoral component if necessary.

Serum Metal Levels and Bearing Surfaces in Total Hip Arthroplasty

This study evaluates steady-state serum metal levels in patients with 4 different combinations of fixation modalities, materials, and bearing couples. Forty patients with a minimum of 5 years of follow-up and with well-functioning primary total hip arthroplasty were recruited to have serum metal levels measured. Serum chromium and cobalt levels in the metal-on-metal cohort were significantly higher ( P < .05) than the other 3 cohorts. The noncemented ceramic-polyethylene cohort had significantly lower ( P < .05) serum chromium levels compared to cemented and noncemented metal-polyethylene cohorts and significantly higher serum titanium levels compared to the cemented metal-polyethylene cohort which had no titanium-containing implants. Debris generated at the metal head/neck modular junction likely accounts for the significantly lower serum chromium concentration in ceramic-polyethylene bearing couples.

Metal-on-Metal Hybrid Surface Arthroplasty

BACKGROUND: Following the reintroduction of metal-on-metal articulating surfaces for total hip arthroplasty in Europe in 1988, we developed a surface arthroplasty prosthetic system using a metal-on-metal articulation. The present study describes the clinical and radiographic results of the first 400 hips treated with metal-on-metal hybrid surface arthroplasties at an average follow-up of three and a half years. METHODS: Between November 1996 and November 2000, 400 metal-on-metal hybrid surface arthroplasties were performed in 355 patients. All femoral head components were cemented, but only fifty-nine of the short metaphyseal stems were cemented. The patients had an average age of forty-eight years, 73% were men, and 66% had a diagnosis of osteoarthritis. Clinical and radiographic follow-up was performed at three months postoperatively and yearly thereafter. RESULTS: The majority of the patients returned to a high level of activity, including sports, and 54% had activity scores of >7 on the University of California at Los Angeles activity assessment system. Kaplan-Meier survivorship curves demonstrated that the rate of survival of the components at four years was 94.4%. For patients with a surface arthroplasty risk index score of >3, the rate of survival of the components at four years was 89% compared with a rate of 97% for those with a score of ≤3. The patients with a higher risk index were 4.2 times more likely to undergo revision to a total hip replacement at four years. Twelve hips (3%) had a revision to a total hip replacement. Seven of the twelve hips were revised because of loosening of the femoral component, and three were revised because of a femoral neck fracture. Substantial radiolucencies were seen around sixteen uncemented metaphyseal femoral stems. No femoral radiolucencies were observed among the hips in which the metaphyseal stem was cemented. The most important risk factors for femoral component loosening and substantial stem radiolucencies were large femoral head cysts (p = 0.029), patient height (p = 0.032), female gender (p = 0.005), and smaller component size in male patients (p = 0.005). CONCLUSIONS: The preliminary experience with this hybrid metal-on-metal bearing is encouraging. Optimal femoral bone preparation and component fixation are critical to improving durability. The metal-on-metal hybrid surface arthroplasty is easily revised to a standard femoral component if necessary.

Loosening and Osteolysis Associated with Metal-on-Metal Bearings

Over the last several years, many orthopaedic surgeons have embraced so-called alternative bearing surfaces in total hip arthroplasty, largely on the basis of the hypothesis that a reduction in the volumetric wear rates afforded by these improved articulating couples will reduce the prevalence of osteolysis and aseptic loosening, which in turn will improve implant survivorship. The articles by Korovessis et al.1 and Milosev et al.2 in this issue of The Journal provide valuable new data on the intermediate-term performance of one metal-on-metal-bearing hip-replacement system. These studies show that this particular metal-on-metal system is not immune to osteolysis and aseptic loosening and further suggest that osteolysis and aseptic loosening may be mediated, at least in part, by an adaptive immune response (metal hypersensitivity) independent of, or in concert with, the relatively well-characterized innate immune response (particle-stimulated macrophage, fibroblast, and osteoblast-mediated inflammatory bone loss) typically associated with periprosthetic osteolysis3. Metal hypersensitivity-induced osteolysis and aseptic loosening represent underappreciated and incompletely understood mechanisms of implant failure. How strong is the evidence that the failures in these two cohorts at the time of intermediate-term follow-up (at a mean of seventy-seven months and eighty-five months) were due to metal hypersensitivity? It should be clearly understood that, at present, the evidence linking osteolysis and aseptic loosening with metal …

LOOSENING AND OSTEOLYSIS ASSOCIATED WITH METAL-ON-METAL BEARINGS

LOOSENING AND OSTEOLYSIS ASSOCIATED WITH METAL-ON-METAL BEARINGS

Use of Cost-Effectiveness Analysis to Evaluate New Technologies in Orthopaedics: The Case of Alternative Bearing Surfaces in Total Hip Arthroplasty

Alternative bearing surfaces offer the potential to reduce wear and improve implant longevity following total hip arthroplasty. However, these technologies are associated with higher costs, the potential for unintended consequences, and uncertain benefits in terms of long-term survival of the implants. The purpose of this study was to evaluate the cost-effectiveness of the use of alternative bearings in total hip arthroplasty. A decision-analysis model was constructed to estimate the cost-effectiveness of the use of alternative bearings for patients undergoing total hip arthroplasty. Model inputs, including costs, clinical outcome probabilities, and health utility values, were derived from a review of the literature. Sensitivity analyses were performed to evaluate the impact of patient age at the time of surgery, implant costs, and reductions in revision rates on the cost-effectiveness of alternate bearing surfaces. In a population of fifty-year-old patients, use of an alternative bearing with an incremental cost of 2000 dollars would be cost-saving over the individual's lifetime if it were associated with at least a 19% reduction in the twenty-year implant failure rate when compared with the failure rate for a conventional bearing. In a population of patients over the age of sixty-three years, the same implant would be associated with higher lifetime costs than would a conventional bearing, regardless of the presumed reduction in the revision rate. Conversely, an alternative bearing that adds only 500 dollars to the cost of a conventional total hip arthroplasty could be cost-saving in a population of patients over the age of sixty-five years, even if it were associated with only a modest reduction in the revision rate. In a population of patients over the age of seventy-five years, no alternative bearing would be associated with lifetime cost-savings, regardless of the cost or the presumed reduction in the revision rate. The cost-effectiveness of alternative bearings is highly dependent on the age of the patient at the time of surgery, the cost of the implant, and the associated reduction in the probability of revision relative to that associated with conventional bearings. Our findings provide a quantitative rationale for requiring greater evidence of effectiveness in reducing the probability of implant failure when more costly alternative bearings are being considered, particularly for older patients.

Serum Metal Ion Levels and Bearing Surfaces in Total Hip Arthroplasty

This study aims to evaluate steady-state serum metal ion levels in patients with 4 different bearing surfaces.

Alternative bearing surfaces in total hip arthroplasty

Total hip arthroplasty continues to be one of the most effective surgical procedures currently available. The longevity of this otherwise very successful procedure is compromised by the wear of the bearing surface. In recent years, great advances have been made in the design of bearing surfaces that poise to offer extended performance to these artificial joints. The purpose of this review is to discuss the recent technologic advances in bearing surfaces and offer an insight to the potential benefits and concerns with the alternative bearing surfaces.

Alternative bearing surface in total hip arthroplasty

Alternative bearing surface in total hip arthroplasty

Examination of surface and material properties of explanted zirconia femoral heads

The crystalline structure of Zirconia femoral heads provides for superior fracture toughness when compared with alumina. Transformation of the crystalline structure that takes place with time in service may produce changes in the surface and biomechanical properties of these implants. This study examines surface and mechanical property changes of Zirconia femoral heads that occur with time in situ. Eighteen retrieved Zirconia femoral heads were compared to 5 factory-sealed controls. The retrieved implants demonstrated significant transformation to a monoclinic phase. This phase transformation was associated with decreased surface hardness. There was evidence of increased surface roughness with increasing time of implantation. The phase transformation that takes place in Zirconia femoral heads may render these implants less desirable as a bearing surface in total hip arthroplasty.

Examination of surface and material properties of explanted zirconia femoral heads

The use of alternative bearing surfaces in total hip arthroplasty (THA) has been advocated as a way to prolong the life of implants by decreasing wear between components. Ceramics, such as Tetragonal Zirconia Polycrystal (TZP) and Alumina have been used as materials for femoral heads in THA because of their desirable mechanical properties (high fracture toughness, surface hardness and low coefficient of friction). TZP femoral heads were introduced in 1985 as an alternative to alumina, because of zirconia’s superior hardness and resistance to fracture; however; there have been recent reports of significant polyethylene wear with TZP ceramic femoral heads. TZP ceramic exists in three different phases of crystalline structure (monoclinic, tetragonal and cubic). TZP, as it is manufactured, is in a metastable tetragonal phase that has the advantage of possessing higher resistance to crack formation than the monoclinic phase, which is the stable phase at room temperature. TZP in a tetragonal phase can undergo transformation into the monoclinic phase under stress or with aging. The phase transformation from tetragonal to monoclinic involves a volume expansion of 3–4%. Because of this volume expansion, crack propagation is halted in the tetragonal phase as the crack is sealed. Once the material undergoes extensive transformation into a monoclinic phase, this advantage is lost, and the implant may be more susceptible to surface damage and to increasing surface roughness. It has been postulated that in an in-vivo environment, TZP ceramic femoral heads undergo aging with increasing conversion of their surface layers into monoclinic phase. Over time, this phase transformation could lead to increasing crack formation and decreased surface hardness, which in turn would leave the surface vulnerable to wear from increasing surface roughness. There have been two recent studies that have examined a limited number (2 in one case, 3 in the other) of explanted TZP femoral head samples for signs of increased wear, but no study has examined a large number of samples for signs of surface deterioration. The purpose of our study was to examine the surface and bulk mechanical properties of explanted TZP femoral heads compared to factory-sealed controls. The hypothesis is that degradation of surface and mechanical properties occurs with increasing time of implantation because of the surface material phase transformation from tetragonal to monoclinic phase. The aim is to compare the control specimens to explanted samples that have been subjected to the rigors of implantation and determine the extent of degradation, if any, which occurs over time in the human body.

Metal-on-Metal Hybrid Surface Arthroplasty: Two to Six-Year Follow-up Study

Following the reintroduction of metal-on-metal articulating surfaces for total hip arthroplasty in Europe in 1988, we developed a surface arthroplasty prosthetic system using a metal-on-metal articulation. The present study describes the clinical and radiographic results of the first 400 hips treated with metal-on-metal hybrid surface arthroplasties at an average follow-up of three and a half years. Between November 1996 and November 2000, 400 metal-on-metal hybrid surface arthroplasties were performed in 355 patients. All femoral head components were cemented, but only fifty-nine of the short metaphyseal stems were cemented. The patients had an average age of forty-eight years, 73% were men, and 66% had a diagnosis of osteoarthritis. Clinical and radiographic follow-up were performed at three months postoperatively and yearly thereafter. The majority of the patients returned to a high level of activity, including sports, and 54% had activity scores of >7 on the University of California at Los Angeles activity assessment system. Kaplan-Meier survivorship curves demonstrated that the rate of survival of the components at four years was 94.4%. For patients with a surface arthroplasty risk index score of >3, the rate of survival of the components at four years was 89% compared with a rate of 97% for those with a score of </=3. The patients with a higher risk index were 4.2 times more likely to undergo revision to a total hip replacement at four years. Twelve hips (3%) had a revision to a total hip replacement. Seven of the twelve hips were revised because of loosening of the femoral component, and three were revised because of a femoral neck fracture. Substantial radiolucencies were seen around sixteen uncemented metaphyseal femoral stems. No femoral radiolucencies were observed among the hips in which the metaphyseal stem was cemented. The most important risk factors for femoral component loosening and substantial stem radiolucencies were large femoral head cysts (p = 0.029), patient height (p = 0.032), female gender (p = 0.005), and smaller component size in male patients (p = 0.005). The preliminary experience with this hybrid metal-on-metal bearing is encouraging. Optimal femoral bone preparation and component fixation are critical to improving durability. The metal-on-metal hybrid surface arthroplasty is easily revised to a standard femoral component if necessary. Therapeutic study, Level IV (case series [no, or historical, control group]). See Instructions to Authors for a complete description of levels of evidence.

Correlation between early and late wear rates in total hip arthroplasty with application to the performance of marathon cross-linked polyethylene liners

Laboratory simulations are typically used to assess the performance of new bearing surfaces for total hip arthroplasty. However, the ability of in vitro studies to accurately predict clinical wear performance remains uncertain. Using computer-assisted radiographic measurement techniques, this study found that the average wear rate based on early (2–3 years) clinical follow-up is representative of the average long-term wear rate for a population. Based on early wear data, Marathon polyethylene liners, cross-linked with 5.0 Mrad of gamma irradiation, are wearing at a mean rate of 0.08 mm/yr. This rate is about half that of non-cross-linked polyethylene but represents a more modest wear reduction than in vitro studies have predicted. If 5 to 10-year Marathon wear data corroborate our short-term results, early clinical wear data should be used to validate hip simulator studies.

Better Choice of Articulating Surface for Total Hip Arthroplasty: The Present and Future of Highly Crosslinked Polyethylene

Better Choice of Articulating Surface for Total Hip Arthroplasty: The Present and Future of Highly Crosslinked Polyethylene

The sphericity of the bearing surface in total hip arthroplasty

This study evaluated the sphericity of bearing surfaces in total hip arthroplasty. The out-of-roundness of metal femoral heads, the inner surface of polyethylene liners, and commercially available ball bearings was measured. The hip prostheses were obtained directly from the manufacturers. The sphericity of the bearing surfaces was significantly inferior to that of the ball bearings. The sphericity of the femoral head on the sagittal plane was inferior to that on the transverse plane. Several significant differences were found among different manufacturers. The sphericity of the femoral head on the sagittal plane and that of polyethylene significantly improved in 1999 and 2000 compared with those in 1995. Further improvement is desirable, however, because good sphericity is expected to prolong the functional performance of the prosthesis after total hip arthroplasty.

Ceramic-on-polyethylene bearing surfaces in total hip arthroplasty. Seventeen to twenty-one-year results.

Polyethylene wear debris, and the resulting inflammatory response leading to osteolysis and loosening, is the primary mode of failure limiting the longevity of total hip replacements. Alternative bearing surfaces, including ceramic-on-polyethylene, have been investigated in an effort to decrease the amount of polyethylene wear debris. The purpose of this study was to evaluate the seventeen to twenty-one-year results of the use of ceramic-on-polyethylene total hip prostheses. Sixty-four total hip prostheses were implanted with cement, by one surgeon, in fifty-six patients from 1978 to 1981. The average age at the index arthroplasty was sixty-nine years (range, fifty-one to eighty-four years). The components consisted of a cemented Charnley-Müller stem with a 32-mm modular alumina femoral head and a cemented all-polyethylene acetabular component. All patients who retained the index prosthesis were assessed clinically with use of Harris hip scores and were evaluated radiographically at the time of the latest follow-up. At the time of this latest follow-up, of the original sixty-four implants, eighteen (28%) were still in place and five (8%) had been revised. The remaining forty-one implants were in patients who had died and were functioning well until the patient's death. No patient was lost to follow-up. Of the eighteen hips with an intact prosthesis in the surviving patients, seven had an excellent clinical result; nine, a good result; and two, a fair result. One asymptomatic hip had definite radiographic evidence of femoral loosening. No hip had definite signs of acetabular loosening or evidence of osteolysis. Survivorship analysis revealed that the probability of survival of the prostheses without revision was 95% at five years, 95% at ten years, 89% at fifteen years, and 79% at twenty years. The mean linear and volumetric polyethylene wear rates were 0.034 mm/yr and 28 mm(3)/yr, respectively. There were no fractures of the ceramic heads. Outstanding long-term clinical and radiographic results were attained despite the use of what are now considered substandard techniques (an inferior stem design, a 32-mm head, and first-generation cementing techniques). The wear rates in this study are lower than previously reported metal-on-polyethylene wear rates and are consistent with the lowest reported in vivo ceramic-on-polyethylene wear rates. These findings support the consideration of ceramic-on-polyethylene bearing surfaces in total hip arthroplasty.