Does Biolox Delta ceramic reduce the rate of component fractures in total hip replacement?

UNLABELLED: Biolox Delta ceramic has been optimized with nano-sized, yttria-stabilized tetragonal zirconium and strontium oxide to help limit cracking propagation. Although its mechanical properties are better than those of earlier generation ceramics, existing data on this material are limited, thus the goals of this study were to determine: 1) the remaining rate of implant fracture; 2) the ideal combination of head diameter and component position. Hypothesis. We hypothesized that the use of the ceramic composite Biolox Delta had reduced the risk of implant fracture. Materials and methods. The bibliographic search (in Pubmed database with the key words «ceramic fracture» and «total hip prosthesis ») identified 46 articles on fractures in third or fourth generation ceramic components, including 5 involving Biolox Delta. Manufacturer's data and ANSM (Agence nationale de sécurité du médicament et des produits de santé) (National Agency for Safety of Drugs and Medical Products) reports were compared with the few clinical cases published in the literature. Results. According to the manufacturer (CeramTec GmbH, Plochingen, Germany), the use of Biolox Delta ceramic has reduced the rate of femoral head fractures to 0.003% compared to 0.021% with alumina ceramic. The fracture rate of liners has remained stable, at approximately 0.03%. The number of ANSM reports confirmed these tendencies. The rate of head component fractures decreases as the head diameter increases. The quality of impaction on the morse taper (cleanliness of the taper, insertion along the axis) plays an important role. Although it is generally only available for cup sizes above 50mm, a 36-mm head diameter seems to be optimal because it prevents impingement between the cup rim and the neck of the stem, without increasing micro-separation with larger diameters. Conclusion. Although Biolox Delta ceramic is more resistant to fractures than alumina ceramic, it can be fractured under suboptimal implantation conditions including edge loading. Its use requires the same precautions as other hard-on-hard bearings and requires special attention to cup position, insertion on or in morse tapers and adjustment of leg length. LEVEL OF EVIDENCE: V expert's opinion.