Metall/Metall—eine neue (alte) Gleitpaarung künstlicher Hüftgelenke in der klinischen Bewährungsprobe

The problems of wear debris of bearing systems containing polyethylene used in hip arthroplasty have led to an increased trend to hard on hard bearing surfaces. Based on our own good experiences with the cementless Zweymüller-Alloclassic system, we implanted the same system with metal-on-metal bearing surfaces (Metasul) in 100 cases between October 1993 and November 1994. In order to record potential side effects, specific questioning and a clinical and radiological survey were carried out before surgery and in regular intervals thereafter. Up to date almost all of the patients have had good and excellent results with an average of more than 90 points in the Harris hip score (47.8 before surgery). There were no cases of revision surgery as a result of aseptic loosening. Two revisions were performed for other reasons (change of the insert, deep infection). No disadvantageous phenomena related to Metasul in the surrounding tissue were found on macroscopic and histologic investigation. The radiological examination did not show any specific signs pertaining to the use of a metal-on-metal bearing system. We also have no grounds to suppose that there are systemic reactions due to chromium or cobalt ions. Up to now, the new metal-on-metal bearing system in connection with a proven hip arthroplasty system has lived up to clinical expectations. With regard to less wear debris, it is justified to implant it in younger patients as well. Other open questions, in particular the possibly improved long-term results, have to be answered by continuation of the study.     

Serum chromium levels before and after revision surgery for loosened metal-on-metal total hip arthroplasty

We investigated the changes of serum chromium levels before and after revision surgery in 10 patients (1 male and 9 females) who underwent exchange of a metal-on-metal articulation for a metal-on-polyethylene component because of aseptic loosening of a metal-on-metal total hip prosthesis. Of the 10 patients, 2 had bilateral metal-on-metal total hip arthroplasty. In the 8 patients who had no residual metal articulation, the mean serum chromium levels before and after revision surgery were 2.53 microg/L and 0.46 microg/L, respectively. In the 2 patients who still had a metal articulation on the contralateral side, the mean serum chromium levels before and after revision surgery were 2.85 microg/L and 1.90 microg/L, respectively. Moderate serum chromium levels in patients with metal-on-metal total hip arthroplasty show a decrease after removal of the metal-on-metal articulation.     

Long-term follow-up of metal-on-metal total hip replacement.

Metal-on-metal articulations were reintroduced to reduce polyethylene particle-induced osteolysis. Elevated serum metal levels have been detected at short- and intermediate-term follow-up. There is little knowledge about long-term effects of increased ionic metal generation. Our study was undertaken to provide information about long-term survival, clinical outcome, radiographic appearance, and serum metal concentrations after a minimum 10 years follow-up with a metal-on-metal hip prosthesis: 105 cementless primary total hip prostheses with metal-on-metal articulating surfaces were implanted in 98 patients with a mean age of 56 years. Clinical data, radiographs, and blood samples were obtained at a follow-up visit 10 years after implantation. Serum cobalt and chromium levels were determined with use of atomic absorption spectrometry. General laboratory analyses included a full blood count and kidney function parameters. The Harris score was 92 points and the UCLA score 6 points after 10 years. Small osteolytic lesions and radiolucent lines were found in Gruen's zones 1, 7, 8, and 14. The probability of survival was 98.6%. The median serum cobalt concentration of the 22 patients with their hip replacement as the only source of cobalt was 0.75 microg/L (range, 0.3-50.1 microg/L). No patient was diagnosed with renal insufficiency during the study period. Five patients were diagnosed with a malignancy between surgery and the follow-up. We do not have evidence of an increased rate of primary malignancies nor could we detect renal failure in our study group. Serum metal levels did not differ from short- and intermediate term follow-up values.     

Exposure to chromium, cobalt and molybdenum from metal-on-metal total hip replacement and hip resurfacing arthroplasty

BACKGROUND: All metal implants--and metal-on-metal bearings in particular--corrode and cause a release of metal ions. Because cobalt and chromium have been shown to be carcinogenic and mutagenic in human and animal models, systemic toxicity and cancer risk are considered to be possible disadvantages of the metal-on-metal articulation. This study was designed to investigate the serum concentration profiles of chromium, cobalt and molybdenum after implantation of a Birmingham hip resurfacing arthroplasty (BHR) and a cementless total hip replacement with a 28-mm Metasul articulation (MTHR), over the first 2 years after implantation. METHODS: We analyzed profiles of metal ion serum levels in 111 patients implanted with a BHR, in 74 patients implanted with an MTHR, and in 130 implant-free probands control subjects using atomic absorption spectrophotometry. RESULTS: Chromium and cobalt concentrations (in microg/L) of all BHR and MTHR patients differed significantly from those of control subjects (chromium: < 0.25; cobalt: 0.25). The median chromium and cobalt concentrations in BHR patients had increased to 5.1 and 4.3 microg/L 2 years after surgery. Concentrations in BHR patient exceeded those in the unilateral MTHR patients. Molybdenum serum concentrations hardly changed over time in either group and were not significantly different from the concentrations seen in the control subjects. INTERPRETATION: During the first 2 years after surgery, the Birmingham hip resurfacing arthroplasty leads to a significantly greater increase in serum chromium and cobalt levels than the 28-mm metal-on-metal MTHR. Observation of patients over a longer period will be necessary in order to evaluate any chronic adverse effects to the system due to elevated chromium and cobalt serum concentrations.     

Outcome and serum ion determination up to 11 years after implantation of a cemented metal-on-metal hip prosthesis

Background and purpose Little is known about the long-term outcome of cemented metal-on-metal hip arthroplasties. We evaluated a consecutive series of metal-on-metal polyethylene-backed cemented hip arthroplasties implanted in patients under 60 years of age.Methods 109 patients (134 joint replacements) were followed prospectively for mean 9 (7–11) years. The evaluation included clinical score, radiographic assessment, and blood sampling for ion level determination.Results At the final review, 12 hips had been revised, mainly because of aseptic loosening of the socket. Using revision for aseptic loosening as the endpoint, the survival rate at 9 years was 91% for the cup and 99% for the stem. In addition, 35 hips showed radiolucent lines at the bone-cement interface of the acetabulum and some were associated with osteolysis. The median serum cobalt and chromium levels were relatively constant over time, and were much higher than the detection level throughout the study period. The cobalt level was 1.5 μg/L 1 year after implantation, and 1.44 μg/L 9 years after implantation.Interpretation Revisions for aseptic loosening and radiographic findings in the sockets led us to halt metal-on-metal-backed polyethylene cemented hip arthroplasty procedures. If the rigidity of the cemented socket is a reason for loosening, excessive release of metal ions and particles may be involved. Further investigations are required to confirm this hypothesis and to determine whether subluxation, microseparation, and hypersensitivity also play a role.     

Breast Milk Metal Ion Levels in a Young and Active Patient With a Metal-On-Metal Hip Prosthesis

Metal-on-metal resurfacing arthroplasty of the hip has been used increasingly over the last 10 years in younger active patients. The dissolution of the metal wear particles results in measurable increases in cobalt and chromium ions in the serum and urine of patients with a metal-on-metal bearing. We measured the cobalt, chromium, and molybdenum ion levels in urine; serum; and breast milk in a young and active patient with a metal-on-metal hip prosthesis after a pathologic fracture of the femoral neck. Metal-on-metal hip prosthesis leads to increasing levels of molybdenum in breast milk in the short-term follow-up. There are no increasing levels of chromium and cobalt ions in breast milk. Besides the already known elevated concentrations in serum of chromium and cobalt after implantation of a metal-on-metal hip prosthesis, we found no increasing levels of chromium and cobalt in urine.     

Elevated serum concentrations of cobalt, chromium, nickel, and manganese after metal-on-metal alloarthroplasty of the hip: a prospective randomized study

In this prospective randomized study, we investigate metal ion concentrations and clinical outcome 2 years after metal-on-metal (28 patients) or metal-on-polyethylene (26 patients) hip arthroplasty with 28-mm modular heads. Metal ion concentrations in patient serum were analyzed by high-resolution plasma mass spectrometry. The clinical outcome was almost identical in both groups with respect to the Harris hip score and the Medical Outcome Study Short Form–36; and on plain radiography, no signs of loosening occurred in any group. In the metal-on-metal group, concentrations of all investigated ions increased significantly when compared with preoperative values: cobalt, 15.3-fold (95% confidence interval [CI], 9.4-21.2); chromium, 5.2-fold (CI, 3.5-7.0); nickel, 2.1-fold (CI, 1.2-3.0); and manganese, 1.6-fold (CI, 1.3-2.0). In the metal-on-polyethylene group, a smaller but significant increase in the concentrations of cobalt and nickel occurred, whereas concentrations of the other ions did not change significantly.     

Pneumatic broaching may prevent massive stem subsidence in femoral revision hip replacement

Massive postoperative subsidence of the prosthesis is a major failure concern in revision hip replacement, as it can potentially provoke recurrent dislocation, secondary femoral fracture, and discrepancies in leg length. In this study, we aimed to evaluate whether the use of vibration-assisted broaching would offer the requisite control and reproducibility necessary to achieve axial stability for a tapered, rectangular revision stem in patients undergoing hip revision surgery. We evaluated the performance of the Zweymüller femoral revision stem implanted following pneumatic rasping in 61 patients (62 hips). There were 39 females and 22 males with a mean age of 72 years. Aseptic loosening was the indication for revision in most cases. According to the Paprosky classification, defects of the femur were grade 2 in 14 hips, grade 3 in 44 hips, and grade 4 in four hips. Ninety percent of the surgeries were first revisions. In the majority of procedures (58 procedures), we utilized anterolateral abductor splitting with the patient in the lateral position as our surgical approach. In six cases, we performed windowing of the femur diaphysis to facilitate cement removal. An extended trochanteric osteotomy was performed in two cases. In all cases, the femoral bed of the implant was modelled at the time of operation using progressively larger pneumatic broaches of 18–22 cm in length. The mean preoperative Postel Merle d’Aubigné (PMA) score was 9, which improved to 16.4 at the time of the last follow-up (mean: 4.8 years; range 3–7 years). No implant showed evidence of significant migration or loosening. During the operation, the specific use of the pneumatic hammer did not cause any complications. In conclusion, the use of the Zweymüller femoral revision stem implanted following pneumatic rasping potentially minimizes complications and maximizes benefits. An extended follow-up is required to better understand the potential long-term benefits of this approach.     

What advantage is there to be gained using large modular metal-on-metal bearings in routine primary hip replacement? A preliminary report of a prospective randomised controlled trial

The aim of this study was to investigate the possible benefit of large-head metal-on-metal bearing on a stem for primary hip replacement compared with a 28 mm diameter conventional metal-on-polyethylene bearing in a prospective randomised controlled trial. We investigated cemented stem behaviour between these two different bearings using Einzel-Bild-R?ntgen-Analyse, clinical and patient reported measures (Harris hip score, Western Ontario and McMaster Universities osteoarthritis index, Short Form-36 and satisfaction) and whole blood metal ion levels at two years. A power study indicated that 50?hips were needed in each group to detect subsidence of > 5 mm at two years with a p-value of < 0.05. Significant improvement (p < 0.001) was found in the mean clinical and patient reported outcomes at two years for both groups. Comparison of outcomes between the groups at two years showed no statistically significant difference for mean stem migration, clinical and patient reported outcomes; except overall patient satisfaction which was higher for metal-on-metal group (p = 0.05). Metal ion levels were raised above the Medicines and Healthcare products Regulatory Agency advised safety level (7 μg per litre) in 20% of the metal-on-metal group and in one patient in metal-on-polyethylene group (who had a metal-on-metal implant on the contralateral side). Two patients in the metal-on-metal group were revised, one for pseudotumour and one for peri-prosthetic fracture. Use of large modular heads is associated with a risk of raised whole blood metal ion levels despite using a proven bearing from resurfacing. The head-neck junction or excess stem micromotion are possibly the weak links warranting further research.     

Bilateral Moore hemiarthroplasty: 36 years of good tolerance without loosening or osteolysis

We report an illustrative case of bilateral Moore arthroplasty with the clinical and radiographic results at 36 years follow-up. The femoral prostheses were implanted for necrosis of the femoral head when the patient was 46 years old. At implantation the patient's physical activity level was high (Devane 4) and remained so until retirement at age 65 years. His activity level remained high (Devane 3) to the age of 82 years when the patient suffered a Vancouver B1 periprosthetic fracture on the left. At this date, both arthroplasties were free of loosening an osteolysis. Plate fixation with wiring led to fracture healing. The Postel Merle d'Aubigné score was 17 before the fracture and 16 at healing (with a pain score of 6 both before and after). Radiographically, acetabular cartilage tolerance was excellent. This case illustrates the excellent clinical outcome obtained with the Moore hemiarthroplasty at more than 35 years despite less than satisfactory initial fixation and the absence of resurfacing. The fact that this prosthesis does not have a polyethylene element prevented the development of osteolysis which could have been expected with such a long postoperative period in this a highly active patient. Favorable factors (good abductor lever arm, adapted head diameter, resistance of the acetabular cartilage in a young subject with femoral head necrosis) may have played a role in this particular case since the excellent and sustained outcome was observed on both sides. This exceptional longevity provides useful information for better determining precise indications for head cups for the treatment of necrosis of the femoral head.     

Chromium and cobalt ion release following the Durom high carbon content, forged metal-on-metal surface replacement of the hip

We evaluated the concentrations of chromium and cobalt ions in blood after metal-on-metal surface replacement arthroplasty using a wrought-forged, high carbon content chromium-cobalt alloy implant in 64 patients. At one year, mean whole blood ion levels were 1.61 microg/L (0.4 to 5.5) for chromium and 0.67 microg/L (0.23 to 2.09) for cobalt. The pre-operative ion levels, component size, female gender and the inclination of the acetabular component were inversely proportional to the values of chromium and/or cobalt ions at one year postoperatively. Other factors, such as age and level of activity, did not correlate with the levels of metal ions. We found that the levels of the ions in the serum were 1.39 and 1.37 times higher for chromium and cobalt respectively than those in the whole blood. The levels of metal ions obtained may be specific to the hip resurfacing implant and reflect its manufacturing process.     

Large head metal-on-metal cementless total hip arthroplasty versus 28mm metal-on-polyethylene cementless total hip arthroplasty: design of a randomized controlled trial

Background  

Osteoarthritis of the hip is successfully treated by total hip arthroplasty with metal-on-polyethylene articulation. Polyethylene wear debris can however lead to osteolysis, aseptic loosening and failure of the implant. Large head metal-on-metal total hip arthroplasty may overcome polyethylene wear induced prosthetic failure, but can increase systemic cobalt and chromium ion concentrations. The objective of this study is to compare two cementless total hip arthroplasties: a conventional 28 mm metal-on-polyethylene articulation and a large head metal-on-metal articulation. We hypothesize that the latter arthroplasties show less bone density loss and higher serum metal ion concentrations. We expect equal functional scores, greater range of motion, fewer dislocations, fewer periprosthetic radiolucencies and increased prosthetic survival with the metal-on-metal articulation.     

Long-term survival of McKee-Farrar total hip prostheses

Because of the recent resurgence of interest in metal-on-metal bearing components for total hip arthroplasties, the long-term results of 153 consecutive McKee-Farrar total hip arthroplasties done in 129 patients by one surgeon between 1969 and 1973 were evaluated. A retrospective chart review provided patient demographics (age, gender, weight, primary diagnosis), revision dates, indications, and implant survival data. The average age of the patients at implantation surgery was 61 years (range, 28-85 years) and these patients were observed as many as 28 years. Primary diagnoses included osteoarthritis (49% of implants), rheumatoid arthritis (38%), and other conditions (13%). During the 28 years of followup, five implants were revised for infection and 14 implants were revised for aseptic loosening. Survivorship analysis of the McKee-Farrar prostheses had a 20-year probability of implant survivorship of 84%, and a 28-year implant survivorship of 74%. Excellent long-term results of the McKee-Farrar prosthesis were seen. Given the inherent problems associated with implant wear debris, especially polyethylene wear particles, second generation metal-on-metal bearing implants may offer a viable alternative to current designs. Their excellent long-term survival may infer particular suitability for use in younger patients.     

Cementless Metasul metal-on-metal total hip arthroplasties at 13 years

Second-generation metal-on-metal bearings have been used since the late 1980s as alternative bearings to eliminate aseptic loosening due to polyethylene wear. The aim of the present study was to evaluate the long-term results of a series of Metasul (Zimmer GmbH, Winterthur, Switzerland) metal-on-metal total hip arthroplasty (THA). One hundred forty-nine cementless THAs with a 28-mm Metasul articulation were performed in 111 consecutive patients. The results were retrospectively reviewed at 13 years postoperatively. Clinical and radiographic evaluations and implant survivorship were performed. Seven hips (4.7%) were revised. The overall survivorship with revision for any reason as the end point was 0.94. The average Harris hip score was 91.4. Expansive osteolysis was found adjacent to the stem in 4 hips. Metal wear-related aseptic loosening was not the major reason for failure in our Metasul metal-on-metal THAs. Recurrent dislocation was the main reason for revision in our series.     

Metallosis after contemporary metal-on-metal total hip arthroplasty. Five to nine-year follow-up

BACKGROUND: Authors of recent studies have reported early periprosthetic osteolysis in patients who have been treated with a contemporary metal-on-metal total hip arthroplasty and have suggested that metal hypersensitivity associated with an immunologic response to metal may be of etiologic importance. We evaluated the results and histologic findings in patients who had undergone revision of a failed contemporary metal-on-metal total hip arthroplasty. METHODS: Two hundred and seventeen total hip arthroplasties (SL-Plus stem and Bicon-Plus cup) with a Sikomet metal-on-metal articulation were implanted in 194 consecutive patients, and the results were retrospectively reviewed at a mean of seventy-seven months postoperatively. Clinical follow-up with the Harris hip score and plain radiographic evaluation were performed. Periprosthetic tissues from fourteen hips that had undergone revision arthroplasty were subjected to histologic analysis. RESULTS: The mean Harris hip score improved from 45 points preoperatively to 88 points at the final evaluation. Fourteen hips (6.5%) were revised: nine because of aseptic loosening, two because of technical failure, and three because of septic failure. Histologic examination of the retrieved periprosthetic tissues from the eleven patients who had undergone revision because of aseptic loosening or technical failure showed metallosis and extensive lymphocytic and plasma-cell infiltration around the metal debris. With removal of the component because of aseptic loosening as the end point, survivorship was 93% for the stem and 98% for the cup. CONCLUSIONS: Our findings are in agreement with those in recent publications and support the possibility that periprosthetic osteolysis and aseptic loosening in hips with a metal-on-metal articulation are possibly associated with hypersensitivity to metal debris. Prospective, comparative, randomized long-term studies are necessary to determine the cause(s) of loosening of prostheses with this particular articulation.     

Hip artroplasty: A transient reason not to be pregnant

Metal implants corrode and release metal ions, cobalt and chromium, which, in turn, may cause systemic toxicity, mostly in the first few months from implantation of metal-on-metal hip arthroplasty. At the time of delivery, the placenta reduces the passage of cobalt and chromium ions released from metal-on-metal prosthesis. From a biomechanical view point, hip replacement should not be considered a contraindication for pregnancy or for spontaneous delivery, and does not seem to have any negative effects in terms of risk of dislocation, loosening, fracture, or revision surgery, neither negative effects on clinical and functional outcomes. The long-term biological consequences of exposure to Co–Cr particles and ions remain largely unknown.     

Serum cobalt levels after metal-on-metal total hip arthroplasty

BACKGROUND: Systemic cobalt dissemination from the Metasul Co-28Cr-6Mo-0.2C metal-on-metal total hip prosthesis has been demonstrated in the first year after implantation. The aim of this prospective study was to monitor the serum cobalt concentrations in patients during the first five years after total hip arthroplasty with a metal-on-metal articulation. METHODS: A total hip arthroplasty was performed without cement in 100 consecutive patients who had either unilateral osteoarthritis or unilateral osteonecrosis. Fifty patients were randomized to be treated with a metal-on-metal articulation, and fifty patients, with a ceramic-on-polyethylene bearing. The femoral stem was made of a Ti-6Al-7Nb alloy, and the threaded acetabular cup was made of commercially pure titanium. Blood samples were taken before the operation and at multiple time-points for five years after the operation. Serum cobalt concentrations were measured with use of atomic absorption spectrometry. RESULTS: In the metal-on-metal group, the median serum cobalt concentration was 1 micro g/L at one year after surgery and 0.7 micro g/L at five years. The median of the serum cobalt concentrations measured from three to twelve months did not differ from the median of subsequent measurements, with the numbers available. The median serum cobalt level in the control group of patients treated with the ceramic-on-polyethylene articulation was below the detection limit at all time-points. CONCLUSIONS: Systemic cobalt release from Metasul metal-on-metal articulations was demonstrated throughout the five-year study period. The median serum cobalt concentrations were found to be slightly above the detection limit and remained in a constant range. The serum cobalt concentrations did not reflect a so-called run-in wear period of the metal-on-metal articulations.     

A comparative study on medium-term results of cementless acetabular components with metal-on-metal and metal-on-polyethylene articulations

The purpose of this study was to evaluate the medium-term clinical and radiological outcomes of two metal-backed acetabular cups with metal-on-metal and metal-on-polyethylene joint couples, in patients unselected for age. Seventy-five metal-on-polyethylene CLS expansion cups were implanted in 70 patients and 66 metal-on-metal Fitek cups were implanted in 65 patients. The average age at surgery in the two groups was 63 years (range, 25 to 72 years) and 58 years (range, 32 to 68 years), respectively. Data regarding 64 of 75 CLS cups (85%) and 58 of 66 Fitek cups (88%) were collected at a minimum 36-month and maximum 144-month follow-up. The Harris hip score showed excellent results in 86% of the CLS cups, good results in 7%, and fair results in 7%. No poor results were recorded. For metal-on-metal acetabular components, excellent results were recorded in 84% of the cups, good results in 8%, fair results in 5%, and poor results in 3%. Fifty-five patients with 57 of 64 CLS cups (89%) and 50 patients with 51 of 58 Fitek cups (88%) were fully satisfied with their prosthesis. No acetabular reconstructions were revised for aseptic loosening. No radiolucent lines greater than 2 mm were observed, either about CLS or Fitek cups, and low incidence of osteolysis and polyethylene wear was noted in metal-on-polyethylene articulations. Post-operative three-phase bone scanning was obtained in 51 patients and this examination did not show increased uptake in blood pool or bone phase indicating aseptic loosening of CLS and Fitek cups. In conclusion, we found similar rates of excellent and good results using two acetabular components with different bearing surfaces, in patients of unselected age. Therefore, the less expensive implant should be selected for total hip arthroplasty in elderly or low-demand patients. Received: 25 January 2002/Accepted: 18 February 2002     

The relationship between activity and ions in patients with metal-on-metal bearing hip prostheses

BACKGROUND: Total hip replacements with metal-on-metal bearings are frequently implanted in young, active patients. The relationship between patient activity and cobalt and chromium ion levels has not been investigated, to our knowledge. METHODS: Seven patients with well-functioning metal-on-metal bearing hip prostheses and one control subject (no implants), all with normal renal function, were monitored during a two-week-long activity protocol. Lower-extremity activity was continuously assessed with use of a computerized, two-dimensional accelerometer. During the first week, the subjects were requested to limit physical activity. The subjects then completed an hour-long treadmill test followed by a week in which they were encouraged to be as physically active as practically possible. Serum levels of cobalt and chromium ions and urine levels of chromium were assessed at ten time-points during these two weeks. RESULTS: Regardless of activity, the serum ion levels for a given patient were essentially constant and no correlation was found between patient activity and serum levels of cobalt or chromium, or urine levels of chromium. A mean increase in activity of 28% during the week of high-intensity activity was associated with a mean decrease of 2.7% in the serum cobalt level and a mean increase of 2.0% in the serum chromium level. During the treadmill test, a mean increase in activity of 1621% was associated with a mean increase of 3.0% in the serum cobalt level and a mean increase of 0.8% in the serum chromium level. These results fall within the variability for the measurement accuracy of these tests. CONCLUSIONS: For these patients, serum cobalt and chromium ion levels were not acutely affected by patient activity. Periodic measurements of serum ion levels could be used to monitor the tribologic (lubrication, friction, and wear) performance of a metal-on-metal bearing without adjusting for patient activity. Additional research is needed into the kinetics of ion production, transport, and excretion.