The effect of bearing type on the outcome of total hip arthroplasty Analysis of 209,912 primary total hip arthroplasties registered in the Dutch Arthroplasty Register
- Peters I. M., Van Steenbergen L. N., Stevens M., Paul C Rijk P. C., Bulstra S.K., Zijlstra W. P.
- Acta Orthopaedica 2017; 88 (x): x–x DOI: 10.1080/17453674.2017.1405669
- Level of Evidence:
- Level III (Retrospective comparative study)
The authors extracted from the Dutch Arthroplasty Register (LROI) the nationwide data of all patients (209,912) that underwent primary THA with a non-Metal-on-Metal bearing (MoM; 5,359) in the Netherlands from 2007 to 2016. The objective of the study was to calculate the revision rates of THAs by bearing type: Metal-on-Polyethylene (MoP; 37,351), Metal-on-Cross Linked Polyethyene (MoXPE; 32,867), Ceramic-on-Polyethylene (CoP; 40,109), Ceramic-on-Cross Linked Polyethyene (CoXPE; 70,175), Ceramic-on-Ceramic (CoC; 17,625), Oxidized Zirconium-on-Polyethyene (OxZroP), Oxidized Zirconium-on-Cross Linked Polyethyene (OxZroXPE). Patients with unknown implant components or patients with at least one of the components were not registered have been excluded (11,836).
For the purpose, multivariable Cox proportional hazard regression ratios (HRs) adjusted for age, sex, ASA score, diagnosis, previous operation to the affected hip joint, fixation technique, femoral head diameter, surgical approach, and period of surgery, were used. MoP was set as reference bearing. OxZroP and OxZroXPE were merged (11,785), because of the small sample size. The revision rate by bearing type of a sub-group of 34,204 patients with less than 60 years was also calculated.
CoXPE, CoC and OxZroXPE in patients younger than 60 years were found to be statistically significantly better than MoP.
The analysis showed that CoXPE, CoC and OxZroXPE lower risk of revision compared to MoP. CoP and CoXPE had statistically significant lower revision rate in comparison with MoP when 22-28 mm ball heads were considered. CoC showed a statistical lower HR compared to MoXPE (0.7 Vs. 1.0) with large ball heads (i.e. 36mm). The overall risk of revision with 22-28mm heads was 18 % higher than 32mm heads and that of 36 mm heads 11% higher when compared to 32 mm heads.
In conclusion, CoXPE, CoC and OxZroXPE bearings offered significantly better survival rates in mid-term compared with MoP according to the Dutch Arthroplasty Register data-set analysis.
- The study has limited follow-up with a mean follow-up of 3.9 years and a maximum of 9.9 years.
- The national registry studies are based on observational data and therefore cannot infer causality.
- The data limit the ability to comment on the effect of THA components, which may be an unknown confounder.
- Bearings with ceramic components, both in hard-on-hard and hard-on-soft are showing a significant better survival when compared with metal bearings.
- Ceramic-on-ceramic offers the best survivorship, when large bearings (i.e. 36mm) are used.