Direct anterior fixation of odontoid fractures with a hollow spreading screw system

Direct fixation of odontoid fractures has the advantage of preserving rotation in the atlanto-axial motion segment. Early mobilisation of patients and minor intra-operative trauma increase the value of this technique. The original screw method of Nakanishi, Magerl, and Böhler, was improved by Knöringer who designed a double-threaded screw for direct fixation of dens axis fractures. He stated that double screwing is absolutely necessary in order to prevent rotation of fragments against each other. The purpose of the present study was to describe a new single screw for direct fixation of odontoid fractures, which is easy to place into the limited space of the dens axis and which offers enough rotational stability and sufficient compression of fracture fragments. The so-called hollow spreading screw system (HSS) consists of an outer hollow screw, a spreading insert, a toothed washer, an hexagonal nut, and a protective nut. Thirty-five patients with traumatic and arthritic odontoid fractures were treated using direct internal fixation with the HSS system. In 30 cases, there was a type-II-fracture, in 3 a shallow type-III-fracture, and in 2 a type-II-fracture with pseudarthrosis formation. Pre-operative neurological deficits were seen in 16 cases. No additional neurological deficits were caused by the surgical procedure. The bony fusion rate of fresh fractures in the presented series was 100%. With the HSS system, ca. 12% postoperative complications, such as slight reduction of head rotation or neck pain, were found. These results are virtually equal to the results of the double-screw technique. Since a relatively simple technical procedure is required for placement of the screw, the HSS system can be recommended in all cases of odontoid fractures suitable for direct anterior fixation.