Improvement of the long-term adhesive strength between bone cement and bone in cemented cup arthroplasty: ex-vivo study

Introduction

One of the main causes of cup loosening in cemented total hip replacement is the lack of a hydrolysis stable compound between the hydrophobic bone cement and the hydrophilic acetabular bone stock. Thus, the long-term adhesive strength between bone and bone cement is decreased resulting in premature aseptic loosening. Accordingly, an amphiphilic bonding system was developed to prevent hydrolytic debonding in the interface bone-to-bone cement.

Materials and methods

Polyethylene cups were cemented in cadaver sheep hips. The hips were prepared with (n = 10) a multilayer bonding system as well as with an improved monolayer bonding system with (n = 10) and without (n = 10) UV-light hardening. The hips were dynamically loaded (10⁶ cycles; 3 Hz; upper/lower load 1,500/200 N) and afterwards turned out with a defined strength to determine the interface compound strength. Dynamically loaded cemented cups without using the bonding system (n = 10) function as a control group.

Results

The interface adhesive strength improved significantly by a factor of 1.9 (using the multilayer bonding system) compared to the unconditioned ones (P ≤ 0.05); for the monolayer bonding system without (with) UV-light hardening the compound strength was 11.9-fold (≥22.2-fold) higher (P ≤ 0.001).

Conclusion

The bonding system significantly improves the adhesive strength between bone and bone cement in cemented cup arthroplasty.