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Background <p>This study aimed to compare the long-term polyethylene wear in total hip arthroplasty (THA) using ceramic-on-polyethylene (CoP) bearings with monolithic zirconia femoral heads versus metal-on-polyethylene (MoP) bearings with cobalt-chromium heads. A secondary objective was to assess the in vivo impact of zirconia low-temperature degradation (LTD) on polyethylene wear.</p> Methods <p>Sixty-two hips were assigned to two demographically matched cohorts receiving polyethylene liners paired with either 28-mm monolithic zirconia or cobalt-chromium heads. All patients received the same implant design and were followed for a minimum of 20 years. Linear head penetration was evaluated over a 25-year period. A zirconia head retrieved after 25 years was analyzed via Raman spectroscopy to investigate phase transformation and residual stress.</p> Results <p>During the first 10 years post-THA, no significant differences were observed in cumulative polyethylene wear or linear wear rates between the MoP and CoP groups. However, beyond 10 years, these groups demonstrated differing wear patterns, with wear tending to increase in the CoP group and decrease in the MoP group. Between 10 and 25 years, the wear rate in the CoP group was approximately 2.4 times higher than that in the MoP group. Analysis of the retrieved zirconia head revealed extensive monoclinic phase transformation (92.3%), high compressive residual stress (−&#xa0;1.9 GPa), and notable grain uplift, correlating with an elevated wear rate of 0.212&#xa0;mm/year during the second decade.</p> Conclusions <p>MoP and CoP bearings demonstrated similar polyethylene wear characteristics during the first decade after THA. However, a marked divergence emerged in the second decade, with significantly higher wear rates observed in the CoP group, likely attributable to the accelerated progression of zirconia LTD. These findings highlight the long-term implications of ceramic degradation and emphasize the need for careful evaluation of zirconia-based components in THA regarding their durability over time.</p>

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Progressive wear divergence beyond 10 years in ceramic- vs. metal-on-polyethylene bearings: the 25-year impact of zirconia degradation in total hip arthroplasty

  • 期刊论文

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  • 发表日期：

    2026年1月29日

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  • Tsunehito Ishida,
  • Yasuhito Takahashi,
  • Toshiyuki Tateiwa,
  • Toshinori Masaoka,
  • Takaaki Shishido,
  • Takeshi Seki,
  • Kengo Yamamoto

摘要

Background

This study aimed to compare the long-term polyethylene wear in total hip arthroplasty (THA) using ceramic-on-polyethylene (CoP) bearings with monolithic zirconia femoral heads versus metal-on-polyethylene (MoP) bearings with cobalt-chromium heads. A secondary objective was to assess the in vivo impact of zirconia low-temperature degradation (LTD) on polyethylene wear.

Methods

Sixty-two hips were assigned to two demographically matched cohorts receiving polyethylene liners paired with either 28-mm monolithic zirconia or cobalt-chromium heads. All patients received the same implant design and were followed for a minimum of 20 years. Linear head penetration was evaluated over a 25-year period. A zirconia head retrieved after 25 years was analyzed via Raman spectroscopy to investigate phase transformation and residual stress.

Results

During the first 10 years post-THA, no significant differences were observed in cumulative polyethylene wear or linear wear rates between the MoP and CoP groups. However, beyond 10 years, these groups demonstrated differing wear patterns, with wear tending to increase in the CoP group and decrease in the MoP group. Between 10 and 25 years, the wear rate in the CoP group was approximately 2.4 times higher than that in the MoP group. Analysis of the retrieved zirconia head revealed extensive monoclinic phase transformation (92.3%), high compressive residual stress (− 1.9 GPa), and notable grain uplift, correlating with an elevated wear rate of 0.212 mm/year during the second decade.

Conclusions

MoP and CoP bearings demonstrated similar polyethylene wear characteristics during the first decade after THA. However, a marked divergence emerged in the second decade, with significantly higher wear rates observed in the CoP group, likely attributable to the accelerated progression of zirconia LTD. These findings highlight the long-term implications of ceramic degradation and emphasize the need for careful evaluation of zirconia-based components in THA regarding their durability over time.