Trace element burdening of human tissues due to the corrosion of hip-joint prostheses made of cobalt-chromium alloys

Summary Using instrumental neutron activation analysis, the concentrations of 18 elements were studied in human articular capsule and fascia lata before and after application of total endoprostheses of the hip joint made of cobalt-chromium alloys. Tissues from the vicinity of the implant showed extreme burdening by corrosion products (Co, Cr, Ni), as well as by Zr, Hf, and Ba from the bone cements. Tissues more distant from the implants exhibited lower, but still significant burdening. Moreover, some essential trace elements not contained in the implant materials were changed in the tissues after implantation. In order to clarify the dissolution of alloy constituents in biological media, the passivation of cobalt-chromium alloy was investigated by tracer techniques using Ringer's solution as a simple model of the body fluids. The passivation process lasted for more than 1 month and was accompanied by a selective dissolution of the alloys constituents in the order Ni > Co Fe > Mo > Cr. A comparison of the tissue analyses with the corrosion experiments demonstrates that the distribution patterns of the corrosion products in the tissues are influenced by both the corrosion process and the biochemical properties of the corrosion products.

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Zusammenfassung Für 18 Elemente wurde die Spurenelementzusammensetzung menschlicher Gewebe (Gelenkkapsel des Hüftgelenks und Fascia lata) mit Hilfe instrumenteller Neutronenaktivierungsanalyse vor and nach Anwendung von Totalendoprothesen des Hüftgelenks aus Kobalt-Chrom-Legierungen untersucht. Die Gewebe aus der Umgebung der Implantate zeigten extreme Belastungen mit Korrosionsprodukten der Metalle (Co, Cr, Ni) sowie mit Zr, Hf und Ba aus den Knochenzementen. Die Gewebe aus größer Entfernung zum Implantat zeigten niedrigere, jedoch noch signifikante Belastung. Sogar nich in den Implantat-Materialen enthaltene essentielle Spurunelemente ware in ihrer Häufigkeit nach Implantation verändert. Um die korrosive Auflösung der Liegerungsbestandteile in biologischen Medien zu untersuchen, wurde die Passierung von Co-Cr-Legierungen mit Hilfe der Trace-Technik untersucht. Dabei wurde Ringer-Lösung als einfaches Modell für die Körperflüssigkeiten gewählt. Der Passivierungsprozeß dauerte mehr als 2 Monat und war von einer selektiven Auflösung der Legierungsbestandtiele in der Reihenfolge Ni > Co Fe > Mo > Cr begleitet. Ein Vergleich der Gewebeanalysen mit den Korrosionsexperimente zeigte, daß die Verteilung der Korrosionsprozeß, als auch durch die biochemischen Eigenschaften der Legierungsbestandteile bestimmt werden.

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Dedicated to Prof. Dr. Jörg Rehn on the occasion of his 66th birthday

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Supported in part by the Bundesminister für Forschung und Technologie, Bonn, project Radionuklidtechnik and by the Deutsche Forschungsgemeinschaft, Bonn     

Increased loosening of cemented straight stem prostheses made from titanium alloys. An analysis and comparison with prostheses made of cobalt-chromium-nickel alloy

We studied the rate of aseptic loosening of three different types of femoral stems in primary total hip replacement. After a median follow-up of 10.2 years 4/147 CoCrNi (SS77) straight stems (type M.E. Müller) were revised. After a median follow-up of 7.7 years 32/239 Ti-6A1-7Nb (SS77) were revised and after a median follow-up of 5.2 years 52/203 SLS Titanium alloy stems were revised. Whereas the first two stems are of identical design (smooth-blasted, anterior and posterior collar), the SLS stem design is different. Surgical procedure and cementing technique have remained unchanged. There is a significantly higher risk of failure for smaller titanium stem sizes and in males and patients who are physically active. This indicates that the greater elasticity of the Titanium alloy is one of the factors responsible for loosening.     

Metallurgical differentiation of cobalt-chromium alloys for implants

BACKGROUND: Cobalt Chromium alloys are used in cemented total hip or knee arthroplasty as well as in metal-on-metal bearings in total hip arthroplasty. An increasing number of publications report about (allergic) reactions to wear particles of Cobalt Chromium alloys. Reactions to nickel are more frequent in comparison to Cobalt or Chromium particles. It is well known that different kinds of Cobalt Chromium alloys contain different amounts of alloying elements; nevertheless. The aim of the current work was to compare the different Cobalt Chromium alloys according to ASTM F or ISO standards in respect to the different alloying elements. MATERIAL AND METHODS: Co28Cr6Mo casting alloys according to ASTM F 75 or ISO 5832-4 as well as forging alloy types according to ASTM F 799 and ISO 5832 such as Co20Cr15W10Ni, Co35Ni20Cr, Fe40Co20Cr10Ni, Co20Cr20Ni, and Co28Cr6Mo were analyzed in respect to their element content of Co, Cr, Ni, Mo, Fe, W, and Mn. RESULTS: In 1935 the Cobalt based alloy "Vitallium" Co30Cr5Mo basically used in the aircraft industry was introduced into medicine. The chemical composition of this alloy based on Cobalt showed 30 wt.% Chromium and 5 wt.% Molybdenum. The differentiation using alloy names showed no Nickel information in single alloy names. CONCLUSION: The information given about different alloys can lead to an unprecise evaluation of histopathological findings in respect to alloys or alloying constituents. Therefore, implant manufacturers should give the exact information about the alloys used and adhere to European law, Euronorm 93/42/EWG.     

An audit of implanted penile prostheses in the UK

OBJECTIVE: To assess whether the outcome of implanting penile prostheses is related to the number of prostheses implanted by surgeons, as several reports showed that the outcome of a urological procedure is directly related to the experience of the surgeon. METHODS: We conducted a retrospective audit of 413 penile prostheses implanted over a 2-year period in the UK by 76 surgeons. RESULTS: About 80% of the surgeons implanted only one or two prostheses per year, usually of the malleable type, and usually on patients in the private sector. Only four surgeons implanted >20 prostheses per year. The overall revision rate for implantation in the UK, at 24%, is far higher than the worldwide average. CONCLUSIONS: Guidelines are needed on the number of prostheses a surgeon should implant per year so that revision rates will decline to more acceptable levels and patients will be offered a genuine choice of product.     

Systemic effects of collagen-impregnated aortoiliac Dacron vascular prostheses on platelet activation and fibrin formation.

To minimize intraoperative blood loss a watertight knitted Dacron aortoiliac prosthesis has been developed by impregnation with bovine collagen. A potential disadvantage is that collagen may be associated with an increase in thrombus formation. We conducted a prospective randomized trial to study the systemic effects of collagen-impregnated prostheses and of aortoiliac operation as such on the coagulation mechanism during the first 10 days after operation. Forty-one patients randomly received either a collagen-impregnated (n = 20) or a nonimpregnated prosthesis (n = 21). Twelve patients who underwent cholecystectomies served as controls. Three markers of the coagulation mechanism were monitored: beta-thromboglobulin, fibrinopeptide A, and fibrin/fibrinogen degradation products. We found no significant differences in median beta-thromboglobulin, fibrinopeptide A, and fibrin/fibrinogen degradation product levels between patients in the collagen-impregnated prosthesis group and patients in the nonimpregnated prosthesis group. This indicates that collagen does not stimulate the coagulation cascade any more than conventional Dacron protheses do. In a comparison of patients who underwent aortoiliac reconstruction and patients who underwent cholecystectomies, the results indicated a significant increased platelet activation and fibrin metabolism in aortoiliac reconstruction group compared with the control group. Finally, we observed a significantly higher preoperative fibrin metabolism in patients with vascular disease than in control subjects. This difference is attributable to the high preoperative fibrin/fibrinogen degradation product values in patients with aortic aneurysms.     

Comparison of CAD-CAM and hand made sockets for PTB prostheses

The aim of the present study was to compare sockets for below-knee (BK) prostheses made by Computer Aided Design-Computer Aided Manufacture (CAD-CAM) to those made by hand. The patients in the study were provided with two prostheses each, which apart from the sockets, were identical. One socket was made by the CAD-CAM technique developed at the Bioengineering Centre, Roehampton, University College London and one was made by hand at the OT-Centre, Stockholm, Sweden. The results were based on investigation of eight unilateral below-knee amputees evaluating their own sockets by Visual Analogous Scale with respect to comfort, pressure, and pain. The sockets were evaluated on seven occasions, at two tests, on delivery, after use every second day for six days and every second week for two weeks. All CAD-CAM sockets except one had to be changed once as compared to the hand made of which only two had to be changed. As to comfort it could not be demonstrated that there was any significant difference between the two types of sockets and both types were well accepted by all patients. Differences in pressure and pain were rarely reported. There were obvious differences between the two types of socket with respect to height, width, and inner surface configuration. The authors feel that CAD-CAM will in the near future be an excellent tool for design and manufacture of prosthetic sockets.     

Immunohistochemical analysis of vascular prostheses implanted with the left ventricular assist system.

BACKGROUND: Dacron vascular prostheses are associated with thromboembolic complications and inflammatory responses; impregnation with bovine collagen reportedly stimulates additional inflammatory/immunologic complications. The Novacor (Baxter Healthcare Corp., Oakland, CA, USA) left ventricular assist system uses Dacron inflow and collagen-impregnated Dacron outflow prostheses. METHODS: Explanted inflow and outflow prostheses were evaluated for inflammatory/immunologic, hemostatic, anticoagulant, and fibrinolytic pathways. Non-implanted prostheses immersed in whole blood or plasma were used as controls. RESULTS: Immunoglobulins and complement components were observed in all prostheses with activated macrophages being present only in implanted prostheses. Antithrombin III was observed in all prostheses whereas fibrin, tissue plasminogen activator, and alpha-2 plasmin inhibitor were present only in implanted prostheses. Endothelial and smooth muscle cells associated with vascular structures containing collagen type IV and laminin were observed solely in implanted prostheses. CONCLUSION: An inflammatory response occurs and key components of hemostatic, anticoagulant, and fibrinolytic pathways are present within implanted prostheses. These processes are accompanied by endothelial and smooth muscle cell infiltration which appear to lay the foundation for neovessel development.     

Endothelialization of polyurethane vascular prostheses implanted in the dog carotid and femoral artery

A new type of vascular prosthesis made of polyurethane with a fibrous structure of the wall was implanted in the carotid and/or femoral artery of dogs. The healing process and neo-intima formation after implantation of this type of prosthesis was followed with light- and scanning electron microscopy. A total of 18 prostheses, which had been implanted for 1, 3, 6, 9 or 20 weeks were studied. Endothelial like cells invaded the prosthesis over the anastomoses, starting the first week after implantation. The growth zones advanced steadily, and prostheses measuring 3 cm in length were completely endothelialized by 20 weeks after implantation, a mean growth rate of the endothelial like cells of 0.09 mm/day. Subsequently, fibroblasts and smooth muscle cells grew between the neoendothelial layer and the prosthetic inner surface, forming a new multi-layered neo-intima. Cellular elements of the neo-intima were firmly anchored onto the inner wall of the prosthesis by cells with extending cytoplasmic protrusions between the fibers of the prosthetic wall. Since in this type of fibrous polyurethane prosthesis, endothelial like cells continually grew until a new lining was formed, apparently facilitated by the fibrous structure of the wall, further investigations are indicated for progression toward clinical implantation of this type of prosthesis.     

Systemic effects of hypernephroma

In a study of 30 patients with hypernephromas, 23 patients manifested systemic effects of the tumor, and in 5 of these, the systemic effects were the presenting feature that led to the diagnosis. In contrast to this, only 17 patients had urologic complaints, and no single patient in this study had the classic triad of hematuria, loin pain, and mass. Weight loss (52 per cent), pyrexia, and elevated sedimentation rate (36 per cent) were seen most frequently. Anemia was seen in 25 percent of patients. Other features seen in this group were abnormalities in liver function, elevated alkaline phosphatase, hypertension, erythrocytosis, and hypercalcemia. In the majority of instances, removal of tumor was associated with remission of these effects. The effects were classified as those of a general toxic nature, those due to normal or abnormal production of hormones, and those due to production of abnormal substances by tumor cells. The evaluation of these effects was useful in making an early diagnosis and in follow-up care.     

Pyrolytic carbon MCP arthroplasty: a report of seven prostheses implanted in two patients

Abstract Rheumatoid arthritis most commonly affects the metacarpophalangeal (MCP) joints of the hand. Pyrolytic carbon MCP arthroplasty has lately provided a new alternative in the treatment of these patients, but reports in the literature are still few. Here, we report the mid-term results of seven such prostheses implanted in two elderly patients with rheumatoid arthritis. Pyrolytic carbon MCP arthroplasty was performed on three MCP joints in one patient and on four MCP joints in another patient. A specific postoperative mobilization protocol was applied. Range of motion, grip strength, and pinch strength were recorded, and radiographs were taken at three, six, and ten months postoperatively. Ten months after the operation, the operated joints were pain-free, and grip and pinch strengths had improved. On average, the passive range of motion had improved and the active range of motion had remained about the same. The joints were clinically stable. No adverse remodeling or bone resorption was observed radiographically. Ulnar deviation recurred in one of the two cases. These results suggest pyrolytic carbon MCP arthroplasty to be a noteworthy alternative in the treatment of MCP joints affected by rheumatoid arthritis. Early treatment, before the development of severe soft tissue destruction, seems to yield better results.     

Predicting the performance of mitral prostheses implanted in children under 5 years of age.

BACKGROUND: Mitral valve replacement (MVR) is occasionally indicated in infants and young children, necessitating the use of small prostheses. The performance of these small valves during somatic growth of the patient can lead to patient-prosthesis mismatch. This study examines performance of these valves over time to establish predicted performance and timing of replacement. METHODS: Records were reviewed of all patients under 5 years of who underwent small mechanical MVR between 1988 and 2004 (n=24). Valve sizes were between 17 and 23 mm (Bileaflet 91.6%, Tilting Disc 8.3%) with a median size of 19 mm. Mean age of patients was 1.4+/-1.3 years with a mean weight of 7.8+/-3.4 kg. RESULTS: Early deaths (n=5, 20.8%) were excluded. There were two late deaths and five patients required redo-MVR: four for outgrowth and one for acute thrombosis at 3 months. Age at redo for outgrowth was 8.6+/-6.6 years with mean body weight of 22.5+/-17.5 kg. Mean time between original operation and redo was 8.6+/-6.1 years in these four patients. Follow-up was a median of 7.5 years (range 0.1-15.7 years). Overall freedom from death or valve replacement was 82.6+/-9.1% at 5 years and 75.7+/-10.6% at 10 years. The performance of the original prostheses showed a peak blood flow velocity across the valves of 1.5+/-0.6 m/s at 5 years and 2.2+/-0.5 m/s at 10 years. Seventy-five percent of the survivors still have their original valve at a mean of 8.1+/-4.4 years postoperative with New York Heart Association status of I or II. Actuarial curves suggest that gradients across the valves reach a peak of >10 mmHg at a mean between 6.5 and 7 years postoperative. CONCLUSION: MVR in children under 5 years carries a high mortality. Nevertheless, small mechanical MVR perform remarkably well in young children with durable haemodynamics despite growth of the patients well beyond more than double the initial bodyweight. Valves can be expected to last over 8 years before requiring re-replacement.     

Longer-term effects of implanted vagal nerve stimulation

Vagal nerve stimulation (VNS) is a non-pharmacologic therapeutic intervention approved in adults and children with neuropsychiatric disorders. Studies conducted over the past 20 years have demonstrated that VNS results in immediate and longer-term changes in brain regions implicated in neuropsychiatric disorders, such as the thalamus, cerebellum, orbitofrontal cortex, limbic system, hypothalamus, and medulla with vagus innervations. This review summarizes the effects of longer-term implanted VNS and how the incorporation of this non-pharmacologic therapeutic management in the treatment regime can be beneficial to address the needs of patients who are unable to tolerate medications and/or undergo surgery and do not respond to pharmacologic therapies. We also highlight the therapeutic efficacy of longer-term implanted VNS, safety, tolerability, patient acceptance, adherence, and adverse events, if any, in adults and children in this modality of treatment.     

Postoperative alteration in the size of dacron vascular prostheses implanted in the infrarenal abdominal aorta

The degree and significance of postoperative alteration in the size of Dacron grafts in the infrarenal abdominal aorta was assessed by computed tomography. We studied a total of 41 knitted Dacron fabric grafts, comprising 28 Gelseal triaxial grafts and 13 Hemashield Microvel grafts, and 29 woven Dacron fabric (Veri-Soft Woven) grafts which were used to replace the infrarenal abdominal aneurysms. These three types of Dacron fabric dilated immediately after replacement to 1.4–1.5 times the manufactured size, but did not dilate further after the surgery.