Second-generation metal-on-metal bearings have been used since the late 1980s as alternative bearings to eliminate aseptic loosening due to polyethylene wear. This study is the first with a long term follow-up for Meteasul, (Zimmer GmbH, Winterthur, Switzerland) metal on metal (MoM) hip replacement; in literature most of the studies have a mean follow-up of 7 years. Metasul showed better performances than other MoM couplings, with a low failure rate at long term follow-up and low revision rate for aspetic loosening. The aim of the present study was to evaluate the long-term results of a series of Metasul implanted between January 1993 and July 1997. 145 cementless THAs with a 28 mm Metasul articulation were performed in 114 consecutive patients. Implant survivorship was calculated and clinical and radiographic evaluations were performed on 93 hips still available for follow-up at a mean of 19 years postoperatively (43 hips are dead or lost to FU, 29, 6%). Nine hips (6.2%) were revised. The cumulative probability of survival of the overall implant at 19 years postoperatively with revision for any reason as the end point, was 0.937 (95% confidence interval, 0.888 to 0.985). The cumulative probability of survival of Metasul with revision for any reason as the end point, was 0.956 (95% confidence interval, 0.916 to 0.997). Clinical outcome has been evaluated with modified Harris Hip Score for 93 hips with an average of 88.8 points. Various degrees of radiolucencies and osteolysis were found proximally around the femoral components of 25 hips (20%). Most of the patients has normal serum levels of metal ions (Co and Cr), and no cases of systemic toxicity has been reported. Cementless Metasul THAs showed high probability of survival at 19 years postoperatively

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). Between January 1993 and September 1996, 149 cementless THAs with a 28 mm Metasul articulation were performed in 111 consecutive patients. Implant survivorship was calculated and clinical and radiographic evaluations were performed on 82 hips still available for follow-up at a mean of 18 years postoperatively. Nine hips (6.0%) were revised. The cumulative probability of survival of the overall implant at 18 years postoperatively with revision for any reason as the end point, was 0.937 (95% confidence interval, 0.888 to 0.985). The cumulative probability of survival of Metasul with revision for any reason as the end point, was 0.956 (95% confidence interval, 0.916 to 0.997). Various degrees of radiolucencies and osteolysis were found proximally around the femoral components of 25 hips (20%). Cementless Metasul THA showed high survival at 18 years postoperatively

Introduction. There has been much discussion in the literature concerning the possible detrimental effects of metal ion circulating in the body after MOM THR. This study seeks to evaluate the differences in observed Co and Cr levels in blood after TKR and several popular THR options. Method. We compared chromium (Cr) and cobalt (Co) levels between three different hip replacement bearings and total knee replacements (TKR) over time. Blood samples were taken from patients who received metasul 28 mm (n=25), metasul 32 mm (n=25) and Durom (n=50) hip bearings and TKR (n=100), pre- operatively and post operatively at six, twelve and twenty-four month intervals. Blood samples were analysed for Co and Cr levels using ICPMS (Inductively coupled mass spectrometry) and reported as parts per billion. Results were compared using Kruskal-Wallis Test (nonparametric ANOVA). Results. No increase was seen in serum Co and Cr levels in TKR patients over time. There were statistically significant differences in Co levels between the TKR group and all bearing surfaces of THR (28, 32 mm and Durom), p<0.001 at two years. Cr levels were significantly higher (p<0.001) in Durom bearings vs TKR only at one year decreasing to p<0.01 at two years. Comparing ion levels over time in the hip group, only in the Durom cohort did serum Cr levels preop vs 12 and 24 months reach a statistical significance of p<0.001. For Co, all three bearings showed a statistically significant increment over time (p<0.01). Highest levels of ions were seen with the 28 mm bearings but comparison between the three THR bearings at two years showed no statistical difference in Cr or Co levels. Median blood Cr concentration did not exceed 1.6 ppb in any subgroup. All median Co concentrations were below 0.8ppb. Conclusions. Over a two-year period Co and Cr levels for TKR did not differ appreciably from preoperative levels. Both Cr and Co levels were only mildly elevated post THR for all bearings. Metasul 28 mm bearings require further follow-up as the Co levels were not seen to plateau at two years

Background and aim. Arthroplasty registries and consecutive series indicate significantly worse results of conventional metal-on-polyethylene total hip arthroplasty (THA) in patients younger than 50 years compared to older patients, with inferior clinical outcomes and 10-year survivorship ranging between 70 and 90%. At our institution, patients under 50 needing a THA receive either a metal-on-metal hip resurfacing (MoMHRA) or a ceramic-on-ceramic (CoC)THA. In order to evaluate the outcome of these options at minimum 10 years, we conducted a retrospective review of all MoMHRA and CoCTHA with more than 10 years follow-up implanted in patients under 50. Methods. From a single surgeon patients’ prospective database, we identified all consecutive THA performed before May 2005 in patients under 50. All patients are contacted by phone and asked to present for a clinical exam and patient reported outcome questionnaires, standard radiographs and metal ion measurements unless the hip arthroplasty has been revised. Complications and reasons for revision are noted. Kaplan-Meier survivorship is analysed for the whole cohort and sub-analysis is performed by type hip arthroplasty, gender, diagnosis and component size. Results. We identified 773 hip arthroplasties in 684 patients under 50 years performed by a single surgeon between 1997 and May 2005. There are 626 MoMHRA, all Birmingham Hip Resurfacings (BHR) in 561 patients (65 bilateral BHR), 135 CoCTHA in 111 patients (24 bilateral CoC) and 12 Metasul MoMTHA in 12 patients. In the BHR group, there are 392 males (70%) (42 bilateral) and 169 females (30%) (23 bilateral). Mean age at surgery was 40.8 years (median 42 years; range 16–50 years). In 33 cases, a BHR dysplasia cup was used (23 in females). Mean follow-up is 11.5 years (median 11 years; range 10–17 years). In the Metasul MoMTHA, there are 8 males and 4 females. Mean age at surgery was 40.4 years (range 20–50 years). All THA were non-cemented and head size was 28mm in all cases. Mean follow-up is 16.8 years (median 17.5 years; range 12–19 years). In the CoCTHA group, there are 71 males (64%) (17 bilateral) and 40 females (36%) (7 bilateral). Mean age at surgery was 38.2 years (median 39 years; range 16–50 years). In 21 cases, the CoCTHA was a revision of a former hip replacement: 15 THA revisions and 6 hip resurfacing revisions. Three types non-cemented acetabular components were used and 7 types femoral stems (5 non-cemented; 2 cemented). Ceramic heads and inlays were Biolox forte in 128 cases and Biolox delta in 7. Head size was 28mm in 125, 32mm in 7 and 36mm in 3. Mean follow-up is 14.9 years (median 15 years; range 10–18 years). Discussion. Patients under 50 needing a hip arthroplasty often present with more complex anatomic abnormalities or bone damage as in congenital dysplasia, avascular necrosis, traumatic osteoarthritis or rheumatic diseases. Besides, the worse results with conventional THA in young patients may be related to a higher activity level. We present the outcome and survivorship of MoMHRA and CoCTHA in patients under 50 at more than 10 years postop

Controversy exists over the role of fretting-corrosion in modular junctions of large-diameter metal-on-metal (MOM) heads given the many design plus alloy mix-and-match variations. Overall data was also scant regarding a) fitting stem trunnions to head tapers, b) role of taper angles, c) role of smooth vs threaded trunnion junctions, d) role of head neck-lengths and e) role of head diameters. While the “12: 14” taper has been used with small CoCr heads for 40 years, we could not find retrieval analyses on this European ‘gold-standard’. We therefore selected 10 femoral stems with 28 mm modular heads for analysis (3–8 years follow-up). Unique to this study were the threaded taper profiles on both stems and heads (Fig. 1). Six stems were cemented Ti6Al4V (Alize, FH-Orthopedics, France) with 12/14 taper angle defined as 5° 42′. These represented Ti64: CoCr combinations from 2 vendors. The other four were CoCr stems including the CoCrMo (Protasul-2) and CoNiCrMo (Protasul-10) alloys (cemented and HA-coated; Sulzer, Switzerland). These CoCr: CoCr combinations from one vendor had “12/14” stem-taper defined as 5° 38′. Anatomical positioning of Metasul heads (Sulzer, Switzerland) was identified by main-wear zone maps. Femoral heads were then bi-valved in horizontal plane for direct imaging by interferometry (WLI) and SEM. Visual corrosion mapping (3) was recorded digitally in 4 anatomical views. Quantitative analysis used 1 to 5 taper zones with 6-replicate measurements per zone (Fig. 1). The WLI and SEM studies showed that non-contacting taper zones inside CoCr heads (Fig. 2) were threaded with pitch of 70 μm (PV: peak-valley depth = 5–7 μm). The non-contact zones on Sulzer stems had 130 μm pitch (PV = 4–8 μm) whereas Alize stems had 210 μm pitch (PV = 10–12 μm). Threads on both stem types were much coarser than CoCr heads; Ti64 stem threads were much coarser than CoCr stems. In contact zones, the Metasul threads had flattened (avg. roughness = 0.45 μm Ra). With CoCr stems there was little difference. Difference in pitch of stem-threads vs head-threads indicated there was no imprinting onto head tapers. Nor were there statistically significant differences evident in the contact zones along CoCr or Ti64 tapers. Small damaged areas (Fig. 3: arrows) may have been due to alternatively; initial machining, surgical impaction, in-vivo cold-welds, fretting, corrosion, or from surgical-removal. The as labeled “corrosion damage” was well within the “mild” grade for all implants.(3) Thus even with this considerable variety of design and material parameters, we were satisfied that these gold-standard taper junctions with threaded interfaces had performed very well with 28 mm MOM at 3–8 years follow-up

Surface arthroplasty or resurfacing represents a significant development in the evolution of hip replacement. A hip resurfacing arthroplasty (HRA) is a bone conserving alternative to total hip arthroplasty (THA) that restores normal joint biomechanics and load transfer and ensures joint stability. Metal-on-metal (MoM) bearings have been preferred for these large diameter articulations because of their lower volumetric wear and smaller particulate debris compared to metal-on-poly-ethylene bearings. Of the many engineering factors which have contributed to the success of the MoM bearing, the metallurgy, diametral clearance, sphericity and surface finish were thought to be most important. More recently, adverse reactions to metal particles and ions generated by wear and corrosion of the metal surfaces have focused the attention on the importance of coverage angle and cup positioning. Currently, the scientific consensus is that cup coverage angle, diametral clearance and metallurgy have their importance in that order. Precise understanding of manufacturing variables is imperative in obtaining clinical consistency and safety in the patient. It is important to examine femoral fixation, bone remodelling, and wear of MoM implants. For the second and third generation MoM HRA various designs and biomaterials have been used. We have conducted a randomised, controlled trial comparing 9 different hip resurfacing prostheses. Clinical and radiographic outcome and whole blood, serum and urine metal ion levels are evaluated at 6 months, 1 year and 2 years in 180 patients with 9 different HRA designs and the differences are analyzed. Besides, the design quality of the 9 different metal-on-metal prostheses and their accessory instruments have been judged during the operation. The Durom with its Metasul history may claim a metallurgic advantage, and in combination with the highest coverage angle of all cups, it may be the best wear couple, as suggested by low ion measurements. However, as discussed above, an optimal bearing alone is not sufficient to achieve a successful hip resurfacing

Thrust plate prosthesis (TPP) is a bone conserving prosthesis in use for over thirty years. TPP is a stemless and uncemented femoral prosthesis fixed at the lateral femoral cortex with a bolt, plate and screw. This has a metal-on-metal articulation with a 28mm Metasul head and Allofit press fit acetabular cup. Our study aimed to assess the survival of this prosthesis. At Oswestry 234 TTP's were implanted between 1995 and 2005. All patients completed a self-assessed questionnaire of Harris Hip Score pre-operatively and post-operatively at 2 months, 1 year, and then yearly. Only those who had a follow up was within the last two years were included in the analysis. 76 patients who had failed to satisfy the criteria were excluded. Of the 158 hips in the study 75 hips were in male patients and 83 were in female patients. The median age of patients was 52 years (range 15 to 82). 75 hips were on the right side and 83 on the left. All patients were operated by the senior author or a senior trainee under his supervision (seven hips). Revision of the implant or decision to revise was taken as the end point of our study. The median time to follow up was 7 years (range 1 to 15). The median pre-operative hip score was 43 (range 3 to 77) which rose to 83 points (range 11 to 100) at the latest follow up. Median hip score in females improved from 39 to 82 points and in males from 52 to 85 points. Twelve patients (5.1%) underwent revision surgery either for infection or aseptic loosening. The Thrust Plate Prosthesis had a good outcome with an increase in hip score of 40 points and 94.9 % survival at a median of 7 years

This study of retrieved 28 mm Metasul™ (cemented) revealed for the first time adverse wear effects created by impingement-subluxation in MOM. The 10 cases selected (with femoral stems) had annual follow-up 3–11 years. (1) Unequivocal evidence here shows that all heads routinely subluxed from the Metasul liners. Femoral stems revealed well-demarcated notches (DN) on necks and trunnions (Fig. 1a: n = 6), shallow cosmetic blemishes (Fig. 1b CB: n = 4), and abrasion by cement (Fig. 1b: PMMA). As demonstrated by EOS radiographs, impingement locations varied with implant positioning, pelvic mobility and patient functionality – both anterior and posterior notching (Fig. 1). The first impingement notch occurred with head located (Fig. 2a), whereas the head had subluxed from the cup at 2. nd. notch (Fig. 2b). The model demonstrated that patients gained 20° motion by such head-subluxation manoeuvres. It was surprising that there was no collateral damage evident on the liners. Even with severe notching of Ti6Al4V and CoCr stems, the cup rims generally appeared well-polished. Femoral heads revealed macro-stripe damage on articular surfaces (Fig. 3), as did cups. Basal and polar macro-stripes on heads were always located at hip impingement positions. The equatorial stripes were formed at main-wear zone boundaries. Thus equatorial stripes were likely created by some form of rim-impact damage (micro-separation) or by local ingress of 3. rd. -body wear particles under the cup rim. Micro-grooving was evident within these macro-size stripes and frequently featured large raised lips (Fig. 3), interpreted as signs of adverse 3. rd. -body wear mechanisms, and rarely described.(2) It would appear that large metal particulates were released during MOM impingement-subluxation manoeuvres and circulated the hip joint to producing severe 3. rd. -body abrasion. Gradual decomposition of such large debris to nano-sized particulates under joint loading would then produce the often-referenced ‘self polishing’ effect of CoCr. EDS studies revealed metal smears on the CoCr surfaces containing the elements of titanium alloy (Ti, Al, V). This was further evidence of impingement-subluxation manoeuvres.(1, 3). In-vivo cup wear patterns also appeared much larger than those produced in MOM simulators. Such differences likely reflected head-subluxation in vivo, whereby heads unconstrained by the subluxation maneuver were free to orbit up and even cross cup rims, i.e. “edge wear”. This appears to be the first study detailing the adverse wear mechanisms in MOM bearings. There are two limitations to our retrieval study, a) these wear results may not be representative for all MOM designs, and b) it is unknown whether such results have relevance to MOM cases continuing successfully