Micromotions between stem and neck adapter depend on prosthesis design and material coupling. Based on the results of this study, the amount of micromotion seems to reflect the risk of fretting-induced fatigue in vivo. Bimodular hip prostheses were developed to allow surgeons an individual reconstruction of the hip joint by varying length, offset and anteversion in the operation theatre. Despite these advantages, the use of these systems led to a high rate of postoperative complications resulting in revision rates of up to 11% ten years after surgical intervention. During daily activities taper connections of modular hip implants are highly stressed regions and contain the potential of micromotions between adjacent components, fretting and corrosion. This might explain why an elevated number of fretting-induced neck fractures occurred in clinics. However, some bi-modular prostheses (e.g. Metha, Aesculap, Ti-Ti) are more often affected by those complications than others (e.g. H-Max M, Limacorporate, Ti-Ti or Metha, Ti-CoCr) implying that the design and the material coupling have an impact on this failure pattern. Therefore, the purpose of this study was to clarify whether clinical successful prostheses offer lower micromotions than those with an elevated number of in vivo fractures.Summary
Introduction
From a mechanical point of view, the clinical use of pedicle screws in the atlas is a promising alternative to lateral mass screws due to an increased biomechanical fixation. The most established surgical technique for posterior screw fixation in the atlas (C1) is realised by screw placement through the lateral mass [1]. This surgical placement may lead to extended bleeding from the paravertebral venous plexus as well as a violation of the axis (C2) nerve roots [1]. Using pedicle screws is an emerging technique which utilises the canal passing through the posterior arch enabling the use of longer screws with a greater contact area while avoiding the venous plexus and axis nerve roots. The aim of this Summary Statement
Introduction
