Editorial: Innovations to improve screw fixation in traumatology and orthopedic surgery

Although bony fixation with screws is a very common intervention and the technique has been refined in previous decades, insufficient screw hold and screw loosening still pose a relevant clinical problem with an incidence of about 10% in rigid fusion constructs. This rate is increased in motion-preserving instrumentations and in patients with low bone quality such as those with osteoporosis. In a recent study, the risk of screw loosening in vertebrae with low bone quality was found to be over 60% (Weiser et al., 2017). As a consequence, revision surgery is required in a substantial number of patients. Improving screw fixation is a challenging field of research because a fundamental understanding of screw fixation in bone is still lacking. Conventional in vitro testing of the implant-bone structure using cadaveric bones is usually employed to evaluate the mechanical fixation of screws. Yet, the precise interplay between the screw thread and the intricate microstructure of trabecular bone is difficult to capture experimentally, especially right at the interface. Furthermore, experimental tests have demonstrated and quantified bone damage due to the screw insertion (Steiner et al., 2016), and microstructural finite element models have demonstrated that this can affect screw stability dramatically (Steiner et al., 2017). It is therefore an interplay of various factors that ultimately determine screw resilience in the bone. Spine surgery is an area where screw fixation is particularly essential, but also particularly problematic. In the case of severe spinal deformity, a surgical instrumentation and fusion of the spine with implants anchored to the vertebrae and sometimes also to the pelvis is often OPEN ACCESS