Anterior Odontoid Screw Fixation: Current Advances in Indications and Techniques

Odontoid fractures (OFs) are one of the most common fractures of the upper cervical spine, estimated to represent 9-15% of all cervical fractures. Although their relative frequency, its optimal management is still debated. When surgery is required, anterior odontoid screw fixation (AOSF) offers several advantages, such as preservation of neck rotation, reduced surgical risk, and shorter hospital stay. However, only well-selected patients are eligible for this procedure, and an accurate interpretation of imaging as well as an optimal surgical timing should be taken into account to identify who may be the "best candidates".

The aim of this narrative review is to report the current advances in the treatment of OFs by AOSF. We will focus on surgical details, including minimally invasive surgery, as well as on pre- and postoperative critical aspects.

With regard to preoperative imaging, type II b OFs (with fracture line oriented from anterior superior to posterior inferior) typically present favourable configuration to be treated by AOSF. Furthermore, a fracture gap >2 mm, an angulation >11° and a displacement >2 mm as well as timing duration from injury to surgery >7 days are predictors of non-union after AOSF. With regard to surgical technique, compared to traditional open technique, MIS procedures are more and more reported. This approach can be performed percutaneously under fluoroscopy or navigation guidance. Finally, the use of a single, bicortical lag screw is strongly suggested to compress the fractured bone surfaces, to reduce the fracture gap and to obtain the best mechanical stability.

Our review suggests that AOSF is an effective option in the treatment of type II OFs. However, a meticulous assessment of preoperative images is mandatory, and particular attention has to be paid to fracture configuration, gap, angulation, displacement and ligament integrity. With regard to elderly population, the possibility of wearing rigid collar should be considered, and recent literature reports encouraging results even without any treatment. If a surgical intervention is required, the timing from injury to the operation represents a crucial parameter, making early decisions an important element in the management of type II OFs. Compared to the traditional open approach, minimally invasive AOSF is reliable, promotes faster recovery and in select cases can be performed even under sedation.