Manufacturers affect clinical results of THA with zirconia heads: a systematic review

Abstract

In the 1980s, zirconia was introduced for THA with the expectation of lower polyethylene wear and better clinical results. However, several studies have reported poor survivorship of zirconia-polyethylene THA. We performed a systematic review and meta-analysis of zirconia-polyethylene THA to confirm or refute the theoretical advantages of this combination. Of 163 studies identified by a comprehensive search, seven met our selection criteria. These involved 769 hips of 586 patients with a mean age of 56.8 years and a minimum followup of 60 months (mean, 89.2 months; range, 60-155 months). The consolidated revision rate of zirconia-polyethylene THA at 89.2 months was higher than that of nonzirconia-polyethylene THA by 5% (risk difference, 0.05; 95% confidence interval, 0.02-0.08). Subgroup meta-analysis suggested THAs with zirconia heads from Ceraver had more revision surgery than nonzirconia heads (risk difference, 0.08; 95% confidence interval, 0.03-0.14), whereas zirconia heads from DePuy did not (risk difference, 0.02; 95% confidence interval, -0.01-0.06). The meta-analysis for annual linear polyethylene wear (which did not involve zirconia heads from Ceraver because of insufficient descriptions) showed no difference between zirconia and control groups. Collectively, THAs with high-quality zirconia heads appear to have prosthesis survivorship and polyethylene wear equivalent to those of THAs with traditional materials, but differing quality among zirconia heads could lead to poor survivorship of prostheses.

Fig. 1

A flowchart illustrates how we selected the seven studies included in our meta-analysis according to our inclusion and exclusion criteria.

Fig. 2

When seven studies were pooled in a fixed-effects model, the risk difference (RD) of revision surgery between zirconia-polyethylene and nonzirconia-polyethylene THAs was 0.05 (95% CI, 0.02–0.08).

Fig. 3

When five studies providing the means and standard deviations of polyethylene wear rate were pooled in a random-effects model, the difference in annual linear polyethylene wear between zirconia-polyethylene and nonzirconia-polyethylene THAs was −0.023 mm per year (95% CI, −0.120–0.074).