Vertebral Bone Quality and Prediction of Screw Loosening in Spine Fusion

Screw loosening is a real problem in degenerative spine surgery because of the morbidity of secondary surgery sometimes needed for elderly patients. Today, there is no real possibility to know before surgery if cemented screws are needed or not. The use of cemented screws has its morbidity. In fact, bone densitometry is not a good exam to predict the bone quality in degenerative spine because of the arthritis. T-score in degenerative spine can be overestimated. The goal of our study is analyze the bone-implant interface after spine fusion using dual-energy CT scan technology which can provide pictures without artifact compared to standard CT scan. This is a prospective observational monocentric study. Patients over 18 years old and have undergone at least two primary spine fusion levels will be enrolled. The exclusion criteria are the use of cemented screws, secondary surgery and neurodegenerative disease. The primary outcome will be the change in the bone-implant interface at six months post-surgery compared to the interface after surgery. The change will be assessed by calibrated dual CT scan. The interface bone density will be assessed using calibrated scans, and correlate to the true vertebral bone density measured before surgery with a QCT. We hope that this study can provide a simple and reproducible help for surgeons to choose between uncommented and cemented screws for their spine fusions surgeries.