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Bearing choice and PJI risk: Evidence from a 10,602-patient THA cohort (Rothman Orthopaedics)

Periprosthetic joint infection (PJI) remains a devastating potential complication following total hip arthroplasty (THA). While bearing surface selection has traditionally been discussed in the context of wear and long-term survivorship, a growing body of research suggests that implant material may influence the local immune environment – and even pose the risk of infection.

CoP ceramic liner and MoP metal femoral head in polyethylene cups, illustrating bearing surface choice and PJI risk in primary THA.CoP ceramic liner and MoP metal femoral head in polyethylene cups, illustrating bearing surface choice and PJI risk in primary THA.
Bar chart: 2-year PJI incidence in THA — CoP 1.64% vs. MoP 2.40% (p = 0.007); single-center observational cohort 2015–2019.
THA outcome table: PJI and reinfection rates lower with CoP vs. MoP; aseptic revision rates comparable between bearing groups.

A study by Emanuele Chisari et al., published in the Journal of Orthopaedic Research, enriches the discussion with significant clinical evidence.

 

The authors reviewed a consecutive series of 10,602 primary THAs performed in 2015-2019 at a single high-volume orthopedic institution: 6,052 ceramic-on-polyethylene (CoP) and 4,550 metal-on-polyethylene (MoP). PJI was defined according to the 2018 ICM criteria, with a minimum one-year follow-up.

 

Key findings

  • At two years, PJI occurred in 2.40% of MoP patients versus 1.64% of CoP patients (p = 0.007).

  • After controlling for age, sex, BMI, and Charlson Comorbidity Index, MoP remained independently associated with a higher risk of PJI (OR 1.55; 95% CI 1.13–2.13).

  • Total revisions at two years were 3.19% (MoP) versus 2.41% (CoP) (p = 0.018), while aseptic revision rates were comparable between groups.

  • Reinfection rates within one year were similar; beyond that, MoP patients experienced reinfection at more than 3x the rate of CoP patients (12.6% vs. 3.6%; p = 0.031).

  • Kaplan-Meier analysis showed significantly better outcomes for CoP on both endpoints (p = 0.0055 and p = 0.017, respectively).

 

The authors revisit the “Trojan horse” hypothesis: metal debris and ions released from MoP bearings (particularly at the head-trunnion junction) may promote a pro-inflammatory local environment that recruits macrophages and neutrophils. These phagocytes can transport bacteria from remote sites to the periprosthetic space. While causality cannot be determined from an observational study, the findings are consistent with earlier basic science work.

 

As one of the largest adequately powered cohorts to directly compare MoP and CoP infection outcomes, this study adds meaningful data to the conversation around bearing selection in primary THA. The authors call for further investigation into whether similar effects may be observed at modular junctions in TKA and dual-mobility hip constructs.

 

📖 Chisari E, Magnuson JA, Ong CB, Parvizi J, & Krueger CA. Ceramic-on-polyethylene hip arthroplasty reduces the risk of postoperative periprosthetic joint infection. Journal of Orthopaedic Research, 40(9), 2133–2138. doi: 10.1002/jor.25230

 

Please check for regulatory approval in your country.

 

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