Aims

Second-generation metal-on-metal (MoM) articulations in total hip arthroplasty (THA) were introduced in order to reduce wear-related complications. The current study reports on the serum cobalt levels and the clinical outcome at a minimum of 20 years following THA with a MoM (Metasul) or a ceramic-on-polyethylene (CoP) bearing.

Aims

The present study investigated the five-year interval changes in pseudotumours and measured serum metal ions at long-term follow-up of a previous report of 28 mm diameter metal-on-metal (MoM) total hip arthroplasty (THA).

Aims

There are limited published data detailing the volumetric material loss from tapers of conventional metal-on-polyethylene (MoP) total hip arthroplasties (THAs). Our aim was to address this by comparing the taper wear rates measured in an explanted cohort of the widely used Exeter THA with those measured in a group of metal-on-metal (MoM) THAs.

Aims

For this retrospective cohort study, patients aged ≤ 30 years (very young) who underwent total hip arthroplasty (THA) were compared with patients aged ≥ 60 years (elderly) to evaluate the rate of revision arthroplasty, implant survival, the indications for revision, the complications, and the patient-reported outcomes.

Aims

We sought to determine whether cobalt-chromium alloy (CoCr) femoral stem tapers (trunnions) wear more than titanium (Ti) alloy stem tapers (trunnions) when used in a large diameter (LD) metal-on-metal (MoM) hip arthroplasty system.

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

Introduction. The Metasul articulation was introduced in the early 1990's. It comprises a 28mm forged, cobalt-chrome head and a forged metal inlay, set into the polyethylene element of the acetabular component. During the 1990's and early 2000's anatomic sized MoM articulations were re-introduced for hip resurfacing and stemmed implant designs. Adverse tissue reactions to metal debris and corrosion products subsequently led to a decline in MoM usage. Materials & Methods. Between January 1995 and December 1998, 133 hips underwent primary THR using the Metasul 28mm bearing. Patients were routinely sent an annual postal Oxford Hip Score (OHS) and radiographs were obtained from the second post-operative year. We have retrospectively reviewed the clinical and radiographic dataset following the 15 year follow-up time point. Results. At a mean follow-up of 16.6 years (range 15.5–19.2 years), the median OHS score at 15 years was 42 (range 7–48). OHS showed statistically significant improvements at all post-operative time points when compared to pre-operative scores (p= <0.001; CI 4.42–6.69). No significant decline in OHS score was observed following the 15 year follow-up. Nine hips were revised at a mean duration of 6.11 years (range 1.09–17.49). Worst case scenario Kaplan-Meier analysis, when lost patients were presumed revised, demonstrated an 84% (CI 0.77–0.90) survivorship at 15 years when revision for any cause was the endpoint. Aseptic loosening as the end point demonstrated an 88% survivorship (CI 0.81–0.93). One hip demonstrated femoral component migration of 2.7mm's but no component loosening's were observed. Discussion. In contrast to the problems reported for other MoM articulations, our study suggests that the 28mm diameter Metasul bearing provides good survivorship and outcome at a minimum of 15 years. No long-term joint stability issues were identified. We have not assessed serum metal ion levels or quantified metal debris generation. Our patients remain under surveillance

The aim of this study was to assess the effect of frictional torque and bending moment on fretting corrosion at the taper interface of a modular femoral component and to investigate whether different combinations of material also had an effect. The combinations we examined were 1) cobalt–chromium (CoCr) heads on CoCr stems 2) CoCr heads on titanium alloy (Ti) stems and 3) ceramic heads on CoCr stems.

In test 1 increasing torque was imposed by offsetting the stem in the anteroposterior plane in increments of 0 mm, 4 mm, 6 mm and 8 mm when the torque generated was equivalent to 0 Nm, 9 Nm, 14 Nm and 18 Nm.

In test 2 we investigated the effect of increasing the bending moment by offsetting the application of axial load from the midline in the mediolateral plane. Increments of offset equivalent to head + 0 mm, head + 7 mm and head + 14 mm were used.

Significantly higher currents and amplitudes were seen with increasing torque for all combinations of material. However, Ti stems showed the highest corrosion currents. Increased bending moments associated with using larger offset heads produced more corrosion: Ti stems generally performed worse than CoCr stems. Using ceramic heads did not prevent corrosion, but reduced it significantly in all loading configurations.

Cite this article: Bone Joint J 2015;97-B:463–72.

We investigated the incidence of soft-tissue lesions after small head metal-on-metal total hip replacement (MoM THR). Between December 1993 and May 1999, 149 patients (195 hips) underwent primary cementless MoM THR.

During the follow-up period, three patients (five THRs) died and eight patients (14 THRs) were lost to follow-up. We requested that all patients undergo CT evaluation. After exclusion of five patients (six THRs) who had undergone a revision procedure, and 22 (28 THRs) who were unwilling to take part in this study, 111 patients (142 THRs) were evaluated. There were 63 men (88 THRs) and 48 women (54 THRs) with a mean age of 45.7 years (37 to 56) at the time of surgery. The mean follow-up was 15.4 years (13 to 19). A soft-tissue lesion was defined as an abnormal peri-prosthetic collection of fluid, solid lesion or asymmetrical soft-tissue mass.

At final follow-up, soft-tissue lesions were found in relation to 28 THRs (19.7%), including 25 solid and three cystic lesions. They were found in 20 men and eight women; 26 lesions were asymptomatic and two were symptomatic. The mean maximal diameter of the soft-tissue lesion was 42.3 mm (17 to 135). The relatively high rate of soft-tissue lesions observed with small head MoM THR remains a concern.

Cite this article: Bone Joint J 2014;96-B:1594–9.

Large-head metal-on-metal (MoM) total hip replacements (THR) have given rise to concern. Comparative studies of small-head MoM THRs over a longer follow-up period are lacking. Our objective was to compare the incidence of complications such as infection, dislocation, revision, adverse local tissue reactions, mortality and radiological and clinical outcomes in small-head (28 mm) MoM and ceramic-on-polyethylene (CoP) THRs up to 12 years post-operatively.

A prospective cohort study included 3341 THRs in 2714 patients. The mean age was 69.1 years (range 24 to 98) and 1848 (55.3%) were performed in women, with a mean follow-up of 115 months (18 to 201). There were 883 MoM and 2458 CoP bearings. Crude incidence rates (cases/1000 person-years) were: infection 1.3 vs 0.8; dislocation 3.3 vs 3.1 and all-cause revision 4.3 vs 2.2, respectively. There was a significantly higher revision rate after ten years (adjusted hazard ratio 9.4; 95% CI 2.6 to 33.6) in the MoM group, and ten of 26 patients presented with an adverse local tissue reaction at revision. No differences in mortality, osteolysis or clinical outcome were seen.

In conclusion, we found similar results for small-head MoM and CoP bearings up to ten years post-operatively, but after ten years MoM THRs had a higher risk of all-cause revision. Furthermore, the presence of an adverse response to metal debris seen in the small-head MOM group at revision is a cause for concern.

Cite this article: Bone Joint J 2014; 96-B:868–75.

We reviewed the literature on the currently available choices of bearing surface in total hip replacement (THR). We present a detailed description of the properties of articulating surfaces review the understanding of the advantages and disadvantages of existing bearing couples. Recent technological developments in the field of polyethylene and ceramics have altered the risk of fracture and the rate of wear, although the use of metal-on-metal bearings has largely fallen out of favour, owing to concerns about reactions to metal debris. As expected, all bearing surface combinations have advantages and disadvantages. A patient-based approach is recommended, balancing the risks of different options against an individual’s functional demands.

Cite this article: Bone Joint J 2014;96-B:147–56.

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

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

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

A total of 219 hips in 192 patients aged between 18 and 65 years were randomised to 28-mm metal-on-metal uncemented total hip replacements (THRs, 107 hips) or hybrid hip resurfacing (HR, 112 hips). At a mean follow-up of eight years (6.6 to 9.3) there was no significant difference between the THR and HR groups regarding rate of revision (4.0% (4 of 99) vs 5.8% (6 of 104), p = 0.569) or re-operation rates without revision (5.1% (5 of 99) vs 2.9% (3 of 104), p = 0.428). In the THR group one recurrent dislocation, two late deep infections and one peri-prosthetic fracture required revision, whereas in the HR group five patients underwent revision for femoral head loosening and one for adverse reaction to metal debris. The mean University of California, Los Angeles activity scores were significantly higher in HR (7.5 (sd 1.7) vs 6.9 (sd 1.7), p = 0.035), but similar mean Western Ontario and McMaster Universities Osteoarthritis Index scores were obtained (5.8 (sd 9.5) in HR vs 5.1 (sd 8.9) in THR, p = 0.615) at the last follow-up. Osteolysis was found in 30 of 81 THR patients (37.4%), mostly in the proximal femur, compared with two of 83 HR patients (2.4%) (p < 0.001). At five years the mean metal ion levels were < 2.5 μg/l for cobalt and chromium in both groups; only titanium was significantly higher in the HR group (p = 0.001). Although revision rates and functional scores were similar in both groups at mid-term, long-term survival analysis is necessary to determine whether one procedure is more advantageous than the other.

Cite this article: Bone Joint J 2013;95-B:1464–73.

A total of 397 hips were randomised to receive Metasul metal-on-metal (MoM), metal-on-conventional polyethylene (MoP) or ceramic-on-polyethylene (CoP) bearings using a cemented triple-tapered polished femoral component (MS-30). There were 129 MoM hips in 123 patients (39 male and 84 female, mean age 63.3 years (40.7 to 72.9)), 137 MoP hips in 127 patients (39 male and 88 female, mean age 62.8 years (24.5 to 72.7)) and 131 CoP hips in 124 patients (51 male and 73 female, mean age 63.9 years (30.6 to 73.8)). All acetabular components were cemented Weber polyethylene components with the appropriate inlay for the MoM articulation. Clinical evaluation was undertaken using the Harris hip score (HHS) and radiological assessments were made at two, five and seven years. The HHS and radiological analysis were available for 341 hips after seven years. The MoM group had the lowest mean HHS (p = 0.124), a higher rate of revision (p < 0.001) and a higher incidence of radiolucent lines in unrevised hips (p < 0.001). In all, 12 revisions had been performed in 12 patients: eight in the MoM group (four for infection, four for aseptic loosening, three in the MoP group (one each of infection, dislocation and pain) and one in the CoP group (infection). Our findings reveal no advantage to the MoM bearing and identified a higher revision rate and a greater incidence of radiolucent lines than with the other articulations. We recommend that patients with a 28 mm Metasul MoM bearing be followed carefully. Cite this article: Bone Joint J 2013;95-B:881–6

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

In this paper, we will consider the current role of metal-on-metal bearings by looking at three subtypes of MoM hip arthroplasty separately: Hip resurfacing, large head (> 36 mm) MoM THA and MoM THA with traditional femoral head sizes.