# How to Prevent Aseptic Loosening in Cementless Arthroplasty: A Review
## 4 Implant Properties
### Bearing Surfaces  
The micromotion between the acetabular cup and inlay produces wear debris which generate a biologic host response responsible for a periprosthetic bone loss that further leads to aseptic loosening [22].  
Ceramic-on-highly cross-linked polyethylene (CoPx) has the best survivorship (0.54/100-component-years), followed by metal-on-polyethylene according to New Zealand Joint Registry study performed on 106,139 THAs [23]. This result is according to another study by [PERSON] et al. performed on 974 primary THAs [23]. Metal-on-metal bearings had the lowest survivorship (1.43/100-component-years) [23]. This statement is supported by a meta-analysis performed by [PERSON] et al. in which metal (MOM) was associated with a higher risk of revision compared to a ceramic-on-ceramic (COC) bearing [24]. When comparing ceramic-on-polyethylene and ceramic-on-ceramic, a meta-analysis by [PERSON] et al. on 2702 patients showed that the results are comparable in terms of revision rate at a long-term follow-up [25]. On the other hand, an analysis of the Dutch Registry on 33,454 patients pointed out a higher 2-year cup revision rate in the ceramic-on-ceramic group compared to ceramic-on-polyethylene (HR = 0.475) [26]. A study on 11,096 patients with primary THAs showed no difference at an 8.7-year follow-up in revision rates between ceramic-on-ceramic compared to metal-on-polyethylene [6]. On the contrary, on a follow-up of 20 years, ceramic-on-ceramic bearing had a lower rate of aseptic revision rate compared to metal-on-polyethylene [27; 28]. These studies suggest that the best bearing in terms of survivorship have the following order: ceramic-on-polyethylene, ceramic-on-ceramic, metal-on-polyethylene and metal-on-metal.  
Another bearing which is gaining increasing interest in recent years is the dual mobility construct. A review which included 448 primary dual mobility cups at a mean follow-up of 7.6 years showed that aseptic loosening rate was less compared to the unipolar group (OR = 1.21, \(p\) = 81) [29; 30]. Another study on 150 primary dual mobility THAs and 166 unipolar THAs at a mean follow-up of 31 months showed that dual mobility bearings had a lower rate of aseptic loosening (0.7% vs. 5%) [30]. An analysis of the Nordic Arthroplastyaty Register Association on over 2000 matched patients concluded that there was no difference in overall risk of revision between dual mobility cups and metal-on-polyethylene or ceramic-on-polyethylene bearings [31]. Another review on mid-term follow-up of more than 500 dual mobility cups showed that there was no statistically significant difference in aseptic loosening rates compared to unipolar cups [32]. A systematic review of [PERSON] et al. on more than 10,000 primary dual mobility cups resulted in an aseptic loosening incidence of 1.3% at a mean follow-up of 8.5 years [33]. The only long-term study we found included 85 dual-mobility total hip replacements performed on obese patients and no aseptic loosening was found at a follow-up of 15 years [29; 30]. More long-term follow-up studies are needed in order to properly assess the aseptic loosening rate.  
[PERSON] et al. tested three different locking mechanisms between the cup and inlay: Allofit(r)-S Alloclassic(r) with cross-linked Durasul(r)-PE liner (Zimmer Biomet); Pinnacle(r)-Multihole dominates with a cross-linked Marathon(r)-PE liner (DePuy Synthes) and Plasmafit(r)Plus7 with a conventional ultra-high-molecular-weight polyethylene (UHMWPE) liner (Aesculap) [20]. The micromotion was less in the Aesculap combination, followed by DePuy and Zimmer Biomet [22].  
Other UHMWPE have been recently introduced, with promising results, such as the X-linked UHMWPE, but further studies are needed in order to decide on the long-term effect on polyethylene wear and aseptic loosening.