Serum-cobalt levels with metal-on-metal bearings in the cement-free total hip arthroplasty results covering two years; prospective study.

PURPOSE OF THE STUDY: Total hip arthroplasty increases the use of alternate bearings to prevent polyethylene wear as the number of younger and more active patients has drastically risen. We carried out a prospective randomized study, to assess and compare clinical results and radiological changes, serum-cobalt- and serum-aluminium-levels when metal-on-metal and ceramic-on-ceramic bearings are applicated. MATERIAL AND METHODS: After giving informed consent 80 consecutive patients were included in this prospective randomized study. They were randomly assigned to receive either a metal-on-metal or a ceramic-on-ceramic bearing in their total hip replacement. Eligible were patients with a primary coxarthrosis or an avascular necrosis of the head of femur. Of the 80 patients 54 were females and 26 males. 42 patients were randomized to a metal-on-metal bearing and 38 patients were randomized to a ceramic-on-ceramic bearing. The average patient-age was 65,8 years and the mean body mass index was 27,7 at the time of operation. Surgery was performed through a transgluteal approach in supine position under general or spinal anaesthesia. A forged conical threaded acetabular component made of titanium-aluminium-niobium alloy was used in all patients. The metal inlays and the 28 mm metal heads were made of Co-28Cr-6Mo alloy with a carbon content of 0,2%. The ceramic inlays and the 28 mm ceramic heads are Al2O3 implants. We used as femoral component a conical rectangular stem of a titanium-aluminium-niobium alloy. Cup and stem werde implanted cementfree. Clinical data werde obtained at a follow up at a minimum of two years after implantation. Patients were assessed with the Harris Hip Score and the University of California at Los Angeles activity scale. 72 of the 80 patients could be explored clinically and radiologically. RESULTS: The 2 year follow up check showed clinically and radiologically no difference between the two groups. The median Harris HipScore was above 90 points and the UCLA score was about 7 points. The medium serum-cobalt level was in the metal-on-metal group about 1.2µg/L and in the ceramic-on-ceramic group below the detection limit. The medium serum aluminium level showed values of 1.2 respectively 1.3 µg/L. The luminescencies in the metal-on-metal group were increased, but all components of the prosthesis could be regarded as stable. DISCUSSION: It was the goal of our prospective study to compare clinical and radiological results of hip arthroplasty in metal-on-metal and ceramic-on-ceramic bearings and assess the serum-cobalt and the serum-aluminium levels. The socalled "biocorrosion" is still a high risk element for loosening of implants because of aseptic osteolysis. A higher release of polyethylene and metal particles is triggered, which leads to a slow but continuous process of inflammation. Apart from the debris also metal ions in a higher concentration are released, so that we could detect after some years in patients with artificial implants a higher level of metal in blood and urine. So far we did not recognize any carcinogenity or the appearance of renal disorders, or other mutagene effects in our patients. We could also not observe any fractures in ceramic implants. We are convinced that short time and intermediate reports are necessary, although final judgement can only be based on long term data. CONCLUSION: Our prospective randomized study showed after two years no difference clinically between the two groups of metal-on-metal and ceramic-on-ceramic bearings with total endoprostheses of the hip. Although medium serum-cobalt level in the metal-on-metal group with 1,2u/L is a significant higher value, whereas it lies in the ceramic-on-ceramic group below the detectable limit.

Results covering 20 years use of the cement-free Zweymüller Alloclassic total endoprosthesis of the hip joint.

PURPOSE OF THE STUDY: From an initial group of 206 hips in 190 patients we carried out a retrospective clinical and radiological control of 74 hips in 72 patients covering a period of 20 years. MATERIAL AND METHOD: Indications in 74 operated hips evidenced 48x(64.9%) primary and 26x(35.1%) secondary coxarthrosis. The average age at the time of operation was 53 years (37 years-68 years). All 72 patients with 74 hips received cement-free self- cutting Alloclassic screw cups of pure Titanium together with a cement-free square Alloclassic stem consisting of Titan- Aluminium-Niob alloy according to Zweymüller. Regarding the technique of operation we used the approach after Watson-Jones in the supine position. As prophylaxis against thrombosis 40% of the patients received derivates of heparine and 60% had anticoagulant therapy with cumarine. Prophylaxis against heterotopic ossifications were not carried out at this juncture in our department. RESULTS: After an average post-operational examination lapse of 20 years we were able to examine 72 patients (37.9%) with 74 hips (35.9%) clinically and radiologically. Further classification of the 72 patients records 47 females and 25 males. The average age at the time of operation was 53 years and at the time of post-operational check-up to 74 years. For the clinical post-operational check-up (n=74) we used the Harris Hip Score. Further evaluation shows 12x(16.2%) excellent results, 26x(35.1%) good and 29x(39.2%) fair results. In 7 patients (9.5%) we had to observe poor results because of multimorbidity, although also in these cases stability of TEP had been achieved. The radiological post-operational check-up of the 74 stable hips (35.9%) shows an average excentric position of the head of 1.4 mm (0 mm up until 4 mm) compared with 1 mm after 10 years. Over an average of about 20 years we carried out an exchange of the inlay and the head because of excentric position of the head, which correlates to a rate of reoperation of 6.8%. DISCUSSION: In 2000 and 2001 we published our 10 year results with cement-free Alloclassic screw cup and cement-free stem in 133 hips in 123 patients and compared our findings with those of other authors. After 10 years we saw only 3 % complications with cups and an overall re-operation rate of 6.7%. The 20-year-results show in all cases stable components of both cups and stems. 5 patients (6.8%) had to undergo re-operation with an exchange of inlay and head, whereby the components of the prosthesis themselves turned out to be stable. An average polyethylene abrasion of 1 mm after 10 years compares with a value of abrasion of 1,4 mm after 20 years. The 6.8% rate of re-operation after 20 years indicates the excellent results of the use of cement-free Alloclassic total endoprosthesis system of the hip according to Zweymüller. CONCLUSIONS: The biocompatible qualities of modern prosthesis material lead to a quicker and optimal bony incorporation of the pros- thesis components. The excellent 20-year-results show a broad indicative spectrum, component stability of the prosthesis in all patients and therefore encourage the further use of cement-free hip implants in the future.

[Periprosthetic fractures of the hip]. / Periprotetické zlomeniny v oblasti kycelního kloubu.

PURPOSE OF THE STUDY: It is the aim of our study to present the results of our way of treatment of the periprosthetic fractures, with the cemented as well as the cement-free stems. MATERIAL: From 1.1.1988 until 31.3.2005 we operated 42 periprosthetic fractures of the hip in 41 patients. 31 of our patients were females, 10 of them males. In 22 cases we operated the right side, 18 times the left side and once we had to operate both sides, but at different times. We used the Vancouver classification scale for the grading of the fractures. In our study we excluded type A fractures; we registered 41 type B fractures and one only type C fracture. The reason for periprosthetic fracture in all these 42 cases was definitely a trauma. In 6 cases we found pre-existing loosening of the stem. We have grouped our patients under two headings: 1. Primary cemented stems (n=13) 2. Primary cement-free stems (n=29) The average age at the time of primary operation was 63.6 years in the group of cemented stems and 67.2 years with the cement-free implants. METHODS: The principle of this operation lies in a stable technique of osteosynthesis. If one operates on a stable stem one uses a one and only technique of osteosynthesis. Patients who also suffer from a loosening of the stem, are treated by replacement of the stem combined with a particular form of osteosynthesis. We generally use a transgluteal access with an L-shaped detachment of the Musc. vastus lateralis. In the group of cemented stems (n=13) we carried out a replacement of the stem 6 times and in the group of cement-free stems (n=29) we had to replace the implant on 7 occasions. Analysing the osteosynthesis technique we find the use of titanium cerclages and titanium elements on 35 occasions, in both groups taken together. As implant for the stem we preferred the modulated revision stem according to Zweymüller. Clinical post-operational examination of our patients was carried out according to the Merle d'Aubigne score and two x-rays at different levels. RESULTS: After an average post-operational check-up time of 3 years and 2 months, we were able to examine 8 patients with cemented stems (61.5%), 4 of whom had replacement of the stem by a cement-free implant. In the cement-free group we evaluated 24 patients after an average time of 4 years and 11 months. In this group we had 5x a replacement of the stem, 3x of these we could operate cement-free. The post-operational radiological check showed an excellent building-up of bone structure without any dislocation of the implant in all 32 cases. DISCUSSION: The average age of our patients shows 77 years with those with cemented stems and 74.5 years in the ones with cementfree implants. Analysis of the cemented stems shows a loosening rate of more than 50%, which coincides with the findings of many other authors. After a couple of years using cups of polyethylene we were confronted with the problem of the so-called Polyethylene disease. These alterations may finally lead to a loss of bone quality, to mechanical loosening of the implant and an increase in danger of fracture. When we discuss the group of patients with cement-free stems and compare them to those with cemented ones, we find a number of quite different characteristics. B2 fractures appear in a quite higher number of patients with cemented and loosened stems. In this regard, our own study is congruent with the studies of other authors. In the cement-free group we had 75% B1 fractures with a stable stem. The explanation for these figures is, that the cement-free implants were well incorporated in the bone structure. CONCLUSIONS: The choice of operative procedure when treating periprosthetic hip fractures depends on the type of fracture and the stability of the prosthesis. Our own very positive experiences and the then emerging results lead to a certain strategy in procedure. That means, for us, the use of a cement-free modulated revision stem according to Zweymüller combined with a particular technique of osteosynthesis, using titanium cerclages and titanium elements.

Serum aluminium and cobalt levels after ceramic-on-ceramic and metal-on-metal total hip replacement.

In a randomised study, 28 patients with a mean age of 62.2 years (32 to 81) with osteoarthritis or avascular necrosis of the hip received either a ceramic-on-ceramic or a metal-on-metal total hip replacement. Apart from the liners the acetabular and femoral components were made of Ti-Al-Nb alloy. The serum aluminium and cobalt levels were measured before, and at one year after surgery. The 15 patients in the ceramic-on-ceramic group had a median pre-operative aluminium level of 1.3 microg/l (0.25 to 8.4) and a cobalt level below the detection limit. At one year the aluminium level was 1.1 microg/l (0.25 to 2.3) and the cobalt level was 0.4 microg/l (0.15 to 0.7). The 13 patients in the metal-on-metal group had a median pre-operative aluminium level of 1.9 microg/l (0.25 to 4.4) and a cobalt level below the detection limit. At one year the median aluminium level was 0.9 microg/l (0.25 to 3.9) whereas the cobalt level was 1.4 microg/l (0.5 to 10.5). This increase in the cobalt level at one year was significant (p < 0.001). Our findings indicate that ceramic-on-ceramic bearings do not cause elevated levels of serum aluminium in the first post-operative year.

A versatile flow cytometry-based immunofluorescence inhibition assay for the detection of bovine viral diarrhea virus-specific antibodies.

A fast, sensitive and reliable flow cytometry-based (FACS = fluorescence activated cell sorting) immunofluorescence inhibition assay (FACS-IFI) for the detection of virus-specific antibodies in sera is described. The method was evaluated using sera from cattle experimentally infected with bovine viral diarrhea virus (BVDV). Virus-infected cells, which were fixed and permeabilized, were incubated with diluted sera from immunized or control animals. Monoclonal antibodies (mabs) against different viral proteins were added, and detected with ALEXA488-conjugated goat-antimouse antibodies. The fluorescence signals were detected by flow cytometry and determined as mean channel values. Results were expressed as percent fluorescence inhibition compared to standardized negative sera. The FACS-IFI test with sera from experimentally infected animals was highly sensitive and specific. Comparison of the FACS-IFI results with a commercially available blocking ELISA, an indirect ELISA and the standard serum neutralization test showed a strong correlation. Furthermore, the detection of protein-specific antibodies was possible using the FACS-IFI test.

A new inactivated BVDV genotype I and II vaccine. An immunisation and challenge study with BVDV genotype I.

An inactivated vaccine containing BVDV I and II strains (PT810; BVDV I, and 890; BVDV II) and using different adjuvants and antigen dosages was tested in a cattle challenge model. Groups of six healthy, seronegative cattle were vaccinated twice with a low dose (10(6.6) TCID(50) PT810 and 10(7.2) TCID(50) 890) vaccine with the adjuvant Bay R1005 or a high dose (10(7.8) TCID(50) PT810 and 10(8. 2) TCID(50) 890) vaccine with two different adjuvants (Bay R1005 or Polygen). Thirty-eight days after the second vaccination, immunised animals (n=18) and non-vaccinated control animals (n=3) were challenged intranasally with 10(6) TCID(50) BVDV strain PT810. For a period of 16 days, virus was isolated from blood leukocytes and nasal swabs, and neutralising antibody titres were determined.The induction of antibodies following immunisation was strongly dependent on the antigen dosage in the vaccine. The high dose formulation induced high serum neutralising antibody titres against both genotypes of up to 32000 after the second immunisation. Animals with neutralising antibody titres >512 (n=14) did not show any marked leukopenia after challenge and only very little or no virus could be isolated from blood leukocytes and/or nasal swabs when compared to control cattle. Furthermore, some of these animals did not show any boost of neutralising or even NS3-specific antibodies, which renders viral replication unlikely and thus would prevent infection of the fetus. Both adjuvants (Bay R1005 or Polygen) were similarly efficient and induced nearly identical antibody responses. In contrast, four of the six low dosage vaccinates had a marked leukopenia and viraemia as well as detectable nasal virus shedding for several days. We conclude that the selected strains and the system of vaccine preparation with high BVDV antigen dosages and highly efficient new adjuvants provide an effective means of protection against BVDV I infections. Investigations to demonstrate the protection against BVDV II infections, the duration of immunity and the ability of fetal protection by using the high dose vaccine in a fetal challenge model will follow.