Cemented metal-on-metal total hip replacement with 28-mm head: prospective, long-term, clinical, radiological and metal ions data

Survival at 11 to 21 years for 779 Metasul® metal-on-metal total hip arthroplasties

BACKGROUND

Total hip arthroplasties (THAs) bearing is one of the most important factors for hip replacement because THA survival depends on it. Metal-on-metal (MoM) bearing has lower wear than metal-on-polyethylene but lot of aseptic loosening decrease utilization. We analyze the survival rate of 28 mm Metasul® bearings after a mean follow-up of 12.9 years.

METHODS

The main objective of this study was to evaluate the survival of the MoM. We evaluate 779 consecutive THAs performed between January 1995 and December 2005 for primary osteoarthritis, congenital dysplasia classified Crowe I, or rheumatoid arthritis. Survival rate was calculated by the Kaplan-Meir method. The association between survival and age, gender, body mass index (BMI), and surface coating was investigated with a proportional odds model. The clinical assessment included Oxford score.

RESULTS

Six hundred fifty-two THAs were reviewed. Sixty-two revisions (9.5%) were performed including 34 aseptic loosening and 11 deep infections. The survival for prosthesis with any reason at 20 years was 87% (confidence interval (CI) 83-90.2) for aseptic loosening at 20 years was 90.1% (CI 87-93.8). There was no association with age, BMI, and surface coating. Gender was significant with lower aseptic loosening for men, hazard ratio = 0.45, p value = 0.035. Oxford score was 57 ± 6.7 (19-60).

CONCLUSION

The survival rate of Metasul was well and seems to be like our clinical finding. However, radiographic aseptic loosening without surgery is not included in the survival rate. The Oxford score was very good with a lot of patients with asymptomatic hip.

LEVEL OF EVIDENCE

Level IV/Retrospective study.

Metasul vs Cerasul bearings: a prospective, randomized study at a mean eighteen years

BACKGROUND

The aims of our study were to compare the clinical, radiographic outcomes and survivals between second-generation metal-on-metal (Metasul) and ceramic-on-ceramic (Cerasul) bearings at a very long-term follow-up.

METHODS

A prospective, randomized study was originally performed on a consecutive series of 250 cementless, 28-mm head and primary total hip arthroplasties between 1999 and 2002. For each bearing (Metasul or Cerasul), 125 THAs were initially included. All cases were evaluated both clinically and radiographically, and survival was assessed, considering revisions for aseptic loosening or for any reason as the end points for failure.

RESULTS

At a mean 18-year follow-up, clinical and radiographic outcomes were similar. Harris Hip Score increased 30% in the Metasul group and 32% in the Cerasul group (p = 0.6). Survival free of aseptic loosening was higher for Cerasul (100%), than for Metasul (94% [CI 88-99.9]) (p = 0.04). Survival free of any revision was 91% ([CI 84-98%]) for Cerasul and 91% ([CI 84-98%]) for Metasul. Fractures of Cerasul insert occurred in four cases (3%) at a mean 12.5 ± 3.3 years (range, 6 to 17 years).

CONCLUSION

At 18 years, Cerasul demonstrated higher survivorship than Metasul considering aseptic loosening as an end point. However, Cerasul liners had high rate of fracture because of its sandwich design (thin ceramic liner into polyethylene). These implants are no more available on the market.

Serum cobalt concentrations remain at low levels at a minimum of 20 years following metal-on-metal total hip arthroplasty

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.

Methods

The present study provides an update of a previously published prospective randomized controlled study, evaluating the serum cobalt levels of a consecutive cohort of 100 patients following THA with a MoM or a CoP articulation. A total of 31 patients were available for clinical and radiological follow-up examination. After exclusion of 11 patients because of other cobalt-containing implants, 20 patients (MoM (n = 11); CoP (n = 9)) with a mean age of 69 years (42 to 97) were analyzed. Serum cobalt levels were compared to serum cobalt levels five years out of surgery.

Results

The median cobalt concentration in the MoM group was 1.04 μg/l (interquartile range (IQR) 0.64 to 1.70) at a mean of 21 years (20 to 24) postoperatively and these values were similar (p = 0.799) to cobalt levels at five years. In the CoP control group, the median cobalt levels were below the detection limit (< 0.3 μg/l; median 0.15 μg/l, IQR 0.15 to 0.75) at 20 years. The mean Harris Hip Score was 91.4 points (61 to 100) in the MoM group and 92.8 points (63 to 100) in the CoP group.

Conclusion

This study represents the longest follow-up series evaluating the serum cobalt levels after 28 mm head MoM bearing THA and shows that serum cobalt concentrations remain at low levels at a mean of 21 years (20 to 24) after implantation.

Cite this article:Bone Joint Res. 2020;9(3):145–150.

What Is the Long-term Survival for Primary THA With Small-head Metal-on-metal Bearings?

BACKGROUND

Large-head metal-on-metal (MoM) bearing hip replacements have been shown to have a much higher rate of revision than other bearing surfaces. However, small-head (≤ 32 mm) MoM bearing surfaces have been in use for many years with several reports of satisfactory mid- to long-term survivorship. It is unclear whether the long-term survival of small-head MoM devices will continue to be satisfactory or whether the same concerns seen with the large-head MoM devices will ultimately become more prevalent.

QUESTIONS/PURPOSES

We analyzed a large national registry to ask: (1) What is the 15-year Kaplan-Meier survivorship of primary conventional THA using small-head (≤ 32 mm) MoM bearing surfaces compared with large-head MoM bearing surfaces in primary THA? (2) Is there an increased rate of revision for adverse reaction to metal debris (ARMD) in this group of patients over time?

METHODS

The Australian Orthopaedic Association National Joint Replacement Registry longitudinally maintains data on all primary and revision joint arthroplasties with nearly 100% capture. We analyzed all conventional primary THAs performed from Registry inception in September 1999 until December 31, 2015, in patients with a diagnosis of osteoarthritis and using MoM bearing surfaces ≤ 32 mm in diameter, defined as small-head MoM. The study group included 4838 primary THA with ≤ 32-mm MoM bearing surfaces. There were 2506 (51.8%) male patients and the median age of patients undergoing THA with a small-head MoM bearing surface was 64 years (range, 20-92 years of age). The outcome measure was the cumulative percent revision defined as the time to first revision using Kaplan-Meier estimates of survivorship at 15 years; reasons for revision and type of revision were also examined. We specifically investigated whether there was an increased risk of revision for ARMD in this MoM group compared with all other bearing surfaces. We compared these results with large-head MoM THAs (femoral head size > 32 mm).

RESULTS

The cumulative percent revision for small-head MoM designs at 15 years was 8.5% (95% confidence interval [CI], 7.3-9.9). The cumulative percent revision for large-head MoM at 14 years was 27.4% (95% CI, 24.8-30.2). Prostheses with a large-head MoM articulation have a higher rate of revision than small-head MoM bearing surfaces (hazard ratio after 6 years, 5.14; 95% CI, 4.1-6.5; p < 0.001). Over time, there was a gradual increase in the diagnosis of ARMD for small-head MoM and the cumulative incidence of revision for ARMD was 0.8% at 15 years.

CONCLUSIONS

Despite survival that is substantially greater than that of large-head MoM THAs, there has been a marked decrease in the use of small-head MoM designs in our registry. Although the reasons for this are likely multifactorial, the increasing incidence of revisions for ARMD among small-head MoM THAs is concerning.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Changes in serum chromium levels over 12 years after Metasul metal-on-metal total hip arthroplasty

We reported the longitudinal changes in serum chromium levels over a minimum of 7 years postoperatively in five men and 25 women with a mean age of 60.3 years after primary unilateral total hip arthroplasty with a Metasul metal-on-metal articulation. The serum chromium ion level showed little variation (0.6-1.2 μg/L) from 2 to 12 years postoperatively in 16/30 patients after unilateral primary Metasul metal-on-metal total hip arthroplasty. On the other hand, the serum chromium level stayed high or showed gradual elevation in 8/30 patients, even though they had well-fixed and well-functioning prostheses.

Comparison of metal ion concentrations and implant survival after total hip arthroplasty with metal-on-metal versus metal-on-polyethylene articulations

Background and purpose - Large metal-on-metal (MoM) articulations are associated with metal wear and corrosion, leading to increased metal ion concentrations and unacceptable revision rates. There are few comparative studies of 28-mm MoM articulations with conventional metal-on-polyethylene (MoP) couplings. We present a long-term follow-up of a randomized controlled trial comparing MoM versus MoP 28-mm articulations, focused on metal ions and implant survival. Patients and methods - 85 patients with a mean age of 65 years at surgery were randomized to a MoM (Metasul) or a MoP (Protasul) bearing. After 16 years, 38 patients had died and 4 had undergone revision surgery. 13 patients were unavailable for clinical follow-up, leaving 30 patients (n = 14 MoM and n = 16 MoP) for analysis of metal ion concentrations and clinical outcome. Results - 15-year implant survival was similar in both groups (MoM 96% [95% CI 88-100] versus MoP 97% [95% CI 91-100]). The mean serum cobalt concentration was 4-fold higher in the MoM (1.5 μg/L) compared with the MoP cohort (0.4 μg/L, p < 0.001) and the mean chromium concentration was double in the MoM (2.2 μg/L) compared with the MoP cohort (1.0 μg/L, p = 0.05). Mean creatinine levels were similar in both groups (MoM 93 μmol/L versus MoP 92 μmol/L). Harris hip scores differed only marginally between the MoM and MoP cohorts. Interpretation - This is the longest follow-up of a randomized trial on 28-mm MoM articulations, and although implant survival in the 2 groups was similar, metal ion concentrations remained elevated in the MoM cohort even in the long term.