A comparison of polyethylene wear in hips with cobalt-chrome or zirconia heads. A prospective, randomised study.
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We have reviewed 70 patients with bilateral simultaneous total hip arthroplasties to determine the rate of failure and to compare polyethylene wear and osteolysis between an implant with a cobalt-chrome head and Hylamer liner with that of a zirconia head and Hylamer liner. The mean thickness of the polyethylene liner was 11.0 mm (8.8 to 12.2) in the hip with a zirconia head and 10.7 mm (8.8 to 12.2) in that with a cobalt-chrome head. At follow-up at 6.4 years no acetabular or femoral component had been revised for aseptic loosening and no acetabular or femoral component was loose according to radiological criteria in both the cemented and cementless groups. The mean rate of linear wear and annual wear rate were highest in the 22 mm zirconia femoral head (1.25 mm (SD 1.05) and 0.21 mm (SD 0.18), respectively) and lowest in the 22 mm cobalt-chrome femoral head (0.70 mm (SD 0.39) and 0.12 mm (SD 0.07), respectively). The mean volumetric wear was highest in the 28 mm zirconia femoral head (730.79 mm ) and lowest in the 22 mm cobalt-chrome femoral head (264.67 mm3), but if the results were compared by size of the femoral head and type of material there was no statistical difference (p > 0.05). Sequential measurements of annual wear showed that the zirconia femoral head had a relatively higher rate of penetration than the cobalt-chrome head over the first three years; thereafter the rate of wear was reduced and compared favourably with that of cobalt-chrome heads. There was a statistically significant relationship between the wear of the polyethylene liner and the age of the patient, male gender and the degree of abduction angle of the cup, but not diagnosis, weight, hip score, range of movement, or amount of anteversion. Osteolysis was identified on both sides of the acetabulum in six patients (9%). Of 12 hips with acetabular osteolysis, six had a 28 mm cobalt-chrome femoral head and the remaining six a 28 mm zirconia head. Osteolysis was observed in zones 1A and 7A of the femur in two hips (3%) with a 28 mm zirconia head (cemented hip) and in four (6%) with a 28 mm cobalt-chrome femoral head (cementless hip). Our findings suggest that although the performance of a zirconia femoral head with a Hylamer liner was not statistically different from that of a cobalt-chrome femoral head and Hylamer liner, there was a trend for the zirconia head to be worse than the cobalt-chrome femoral head. (+info)
Cobalt toxicity after McKee hip arthroplasty.
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The significance of cobalt as a cause of symptoms after McKee hip arthroplasty is discussed. Seven patients are described in whom such arthroplasties. became unsatisfactory after periods varying from nine months to four years. Six of these patients were cobalt-positive but nickel- and chrome-negative on patch testing. Macroscopic and histological necrosis of bone, muscle and joint capsule around the prostheses was found in five patients whose hips were explored. The symptoms were progressive pain, a feeling of instability, and in two cases spontaneous dislocation. Radiological features included acetabular fracture, bone resorption, loosening and dislocation of the prosthesis. Increased cobalt concentrations (determined by atomic absorption spectrophotometry) in the urine of four patients and in a variety of tissues in one patient are presented. Patch testing is recommended in the investigation of patients with troublesome McKee hip arthroplasties (+info)
A study on the effects of particulate metals of orthopaedic interest on murine macrophages in vitro.
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This is part of a larger study designed to investigate the action of particulate metals of orthopaedic interest on tissues. Damaging effects were determined by cytological examination and the assay of two enzymes. Lactic dehydrogenase (LDH) if released into the supernatant indicates a damaged cell membrane; decreased intracellular levels of glucose-6-phosphate dehydrogenase (G6PD) indicates a lowered phagocytic capacity of the cells. Soluble and wear products around implanted prostheses could facilitate late infections by impairing local reactions to bacteria. Particulate cobalt, nickel and cobalt-chromium alloy were found to damage the cells and to cause LDH release. G6PD was found to have a lower activity in the cells exposed to these materials. In contrast, titanium, chromium and molybdenum were well tolerated by macrophages and had no effect on the distribution and activity of either enzyme. The solubility of these metals in the culture medium was also measured. (+info)
An unusual reaction in muscle in association with Vitallium plate: a report of possible metal hypersensitivity.
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A case is reported in which fractures of the radius and ulna were fixed with Vitallium plates and screws. Seven years later a painful swelling appeared over the extensor aspect of the forearm. After eight years sarcoma was suspected and a pale tumour infiltrating muscle was found at operation. However, the histology excluded neoplasia and showed massive fibrosis and patchy necrosis of muscle, with chronic inflammatory changes peripherally. After the removal of the metal the swelling disappeared. A sinus down to the ulna followed operation and was not cured two years later. At this stage standard patch testing showed skin sensitivity to cobalt. Metal sensitivity is proposed as the cause of this extraordinary reaction in muscle. (+info)
Comparison of polyethylene wear with femoral heads of 22 mm and 32 mm. A prospective, randomised study.
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In this prospective, randomised study, we have compared the wear rate of cemented, acetabular polyethylene cups articulating with either a 22 mm or a 32 mm cobalt-chromium head. We evaluated 89 patients who had a total of 484 radiographs. The mean follow-up period was 71.4 months (SD 29.1). All the radiographs were digitised and electronically measured. The linear wear rate was significantly higher during the first two years and decreased after this period to a constant value. We suggest that this is partly due to a 'run-in' process caused by irregularities between surfaces of the cup and head and an initial plastic deformation of the polyethylene. The mean volumetric wear was 120.3 mm/year for the 32 mm head, which was significantly higher than the 41.5 mm3/year for the 22 mm heads. The mean linear wear rate was not significantly different. We were, however, unable to find radiological signs of osteolysis in the patients who had higher wear rates. (+info)
Impaction bone grafting for total hip revision.
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We used impaction bone grafting for total hip revision on 26 hips in 25 patients. Average patient age was 68 (34-89) years, and average duration from last surgery was 9 years. In all cases morselized allograft bone was used for the graft, and the femoral component was a collarless, polished, tapered stem. Average duration of surgery was 2.4 h, intraoperative blood loss 600 cc, blood replacement 2.4 units, and acute-care hospital stay 5 days. Complications were varus placement of the stem in two patients and postoperative development of varus in one, one intraoperative and three postoperative femoral fractures, and one postoperative dislocation. Average subsidence was 0.6 cm. We believe that most, if not all, of these complications could have been prevented. (+info)
Surface treatment agent for dental metals using a thiirane monomer and a phosphoric acid monomer.
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To develop a new surface treatment agent which improves the bond strength of adhesive resin to both non-precious and precious metals, experimental treatment agents containing both an adhesive bonding promoter for precious metals and one for non-precious metals were prepared by dissolving epithioalkyl methacrylate (EP3MA or EP8MA) and 10-methacryloyloxydecyl dihydrogen phosphate (MDP) in acetone. The surfaces of dental metals were treated by the treatment agents and metal specimens were butt-jointed together with MMA-PMMA resins. After 2,000 thermal cyclings in water at temperatures of 4 and 60 degrees C, tensile bond strengths were measured. The effectiveness of surface treatments was evaluated by tensile bond strengths and microscopic failure mode analysis after the tensile test. The combined treatment of EP3MA-MDP or EP8MA-MDP was used effectively for non-precious metals as well as precious metals, and was shown to be extremely effective compared with the single treatment of EP3MA, EP8MA, or MDP. (+info)
Effects of Ga addition on the mechanical properties of 35Ag-30Pd-20Au-15Cu alloy.
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Ten 35Ag-30Pd-20Au-15Cu alloys containing 0.00, 0.25, 0.50, 0.75, 1.00, 1.25, 1.50, 2.00, 4.00, or 6.00% Ga were experimentally prepared to investigate the effect of Ga on their mechanical properties in addition to their use for denture frameworks, connectors and clasps. The effect of Ga addition on the mechanical properties was marked with a significant increase in the tensile strength, 0.2% off-set proof stress (proof stress) and Vickers hardness observed at low Ga contents (0.25-2.00%). On the other hand, the elongation significantly decreased with the addition of Ga at all contents used in this study. The tensile strength, proof stress and Vickers hardness of the 35Ag-30Pd-20Au-15Cu alloys containing 0.25-2.00% Ga were in the range of 809-957 MPa, 669-857 MPa and 260-301 MPa, respectively. These values are similar to those of Co-Cr alloys, suggesting that 0.25-2.00% Ga alloys can be used for denture frameworks, clasps and connectors. (+info)