Risks and advantages in standardization of bores and cones for heads in modular hip prostheses.

Standardization of bores and cones for modular hip prosthesis heads has been addressed by both the International Standard Organisation (ISO) and the American Society for Testing and Materials (ASTM) in response to the need to control the conditions of head-trunnion fit that thereby improves implant safety. Standardization of these conditions could help the surgeon avoid fit mismatch, especially during revision surgery. Instituting a system of standardization without taking all critical parameters into consideration, however, could be more dangerous than no system at all. The current article discusses the main taper parameters that directly influence the performance of ceramic head-metallic trunnion assemblies and argue for standardization that integrates all these parameters. Several examples, based on experimental mechanical tests and finite element analysis, are given to support the argument.