Management of odontoid fractures by anterior odontoid screw may pose a challenge especially in an underequipped operating theatre. We reviewed the available literature for the management of odontoid fractures by odontoid screws. We tried to underline the main cornerstones for the success of this procedure. These fall into: selection of the patient with proper planning, proper reduction of the fracture and achieving a good trajectory for the placement of the screw. We tried to adopt all the mentioned tips and tricks as much as we could, or we made some modifications to overcome shortcomings due to the underequipped operating theatre, being in a developing country.
Anterior odontoid screw should be performed with fractures extending from the anterosuperior part to the posterosuperior part. In this fracture type the screw can be placed perpendicular to the fracture line. This is classified Grauer type IIb . All of our patients had this type of fracture. Other fracture types in which the line extends obliquely from the posterosuperior to the anterosuperior edge is not ideal for odontoid screw because reduction of the fractured segments cannot take place.
Good bone quality is vital for healing of fractures. Odontoid fractures are liable to poor healing due to lack of trabeculae at the cortical bone in the base of odontoid. Patients with osteoporosis comminuted fractures or pathological fractures are not candidates for surgery. Body shape may pose additional challenges to the operation (e.g. barrel chest, short neck, subaxial cervical canal stenosis, or severe thoracic kyphosis). It may be difficult for drilling and screw placement in these cases .
In our study we used a single screw in all patients. Placement of 2 screws yields a higher fusion rate in patients older than 70 years . However, no difference in outcome or stability in the rest of patients was found [7, 8]. In our situation, placing two screws is not feasible due to economic reasons. Moreover, placement of 2 screws may be more technically demanding .
The main tools we lack in our theatre were the O-arm or navigation, an angled retractor and specially designed instruments for this procedure. Here we describe how we overcame these problems. The usually used incision is made at the level of C5-6, which allows easier placement of the screw due to the more feasible trajectory. Due to the unavailability of a special angled retractor as previously described , we used the basic retractor system present in our theatre: Cloward retractor. At first, we used a hand retractor in the cranio-caudal plane. However, the assistant could not maintain the exact retraction and was rather tiring due to the presence of abundant soft tissues in the cranial direction. Therefore, 2 Cloward retractors are used to help in both the horizontal and vertical planes. Campos and colleagues described an approach with a higher incision opposite C2-3 in contrast the usual opposite C5-6. They claimed that this approach avoided excessive tissue damage by retraction or dissection and blind entry of the instruments. However, we found the trajectory through the high incision somewhat problematic with our non-angled instrument set . In spite of being less cosmetically accepted, we found that using a longitudinal incision had the advantages of both low and high incisions. The need for rostral traction to reach C2-3 disc is avoided as in the high incision and a good trajectory is achieved as in the low incision.
Anatomical identification of the midline is crucial in the determination of the entry point. This was done after equally dividing the distance between the two longus colli muscles on either side of the body of C2. An important anatomical landmark seldom mentioned in literature, but useful in our series is the palpable midline keel in the midpoint of the anterior surface of dens . Identification of the midline was confirmed with the help of fluoroscopy. The main use of the A/P view is the identification of the midline. During introduction of the K-wire we did alternating A/P and lateral views by the single plane image intensifier to ensure right trajectory (due to the unavailability of biplanar o-arm or 2 image intensifiers). The major disadvantage of this method we found was the prolonged fluoroscopy time, thus requiring more operative time, radiation exposure and patience. The repeated switching between A/P and lateral views may degrade the quality of A/P images and may also be a risk factor for surgical site infection . Therefore, proper knowledge of the anatomical landmarks may decrease the need for the use of fluoroscopy during the procedure and being dependent on it.
Drilling was done by using a hand-drill instead of the unavailable power drill. Hand drill allows for better control than a powered drill due to direct feedback between the user’s input and the sensation of the drill bit turning. During the procedure one can have intraosseous feeling then some release at the fracture line then intraosseous feeling again when the fracture segment is entered. We found that it is safer especially in the absence of a tube system which protects the adjacent tissues from the instruments rotating at high speed. However, drilling with a hand-drill remains more time consuming. Pressure on the k-wire may lead to breakage especially in the presence of metal fatigue, so we opted to use new never-used k-wires with sharp tip. This was to avoid the rare complication of k-wire breakage during the procedure .
The entry point of the screw is poorly described in literature. However, the ideal entry point mentioned is the middle part of the anteroinferior angle of C2 body . Lobo and colleagues tried different entry points in their series by either going millimetres above, millimetres below or exactly at the anteroinferior angle. They noted that for best fusion the screw must reach the apex of dens as it has the cortical highest bone density. They found out that placing the entry point above or anterior to the body had acceptable union rates . However, this anterior position was linked in literature to the rare incidence of pharyngeal extrusion of the screw . We prefer in our series to use of a short-headed screw. The entry point is a few millimetres deeper in the inferior surface of C2 to avoid breakdown of the body anterior to the screw trajectory. We aim at advancing the screw till it is impacted under the cover of the inferior endplate of C2. We found this step very useful in avoiding postoperative dysphagia which is not uncommon after this procedure and avoids screw pullout. This technique in fact is similar in its idea to the use of Herbert screw as described by Lee and colleagues (double threaded screw with no head) which is also buried beneath the edge of C2 and offers the same advantages . Going deeper in the inferior surface of C2 and following the exact trajectory towards the tip of dens maybe hindered by the anterosuperior portion of c3 which may need trimming. Dysphagia usually occurs in the early postoperative period and decreases gradually. It may be related to retraction of pharynx and esophagus or dissection of soft tissues . We tried to ameliorate this problem by loosening the retractor after introducing the k-wire. Another cause for dysphagia is the close relationship of the esophagus and pharynx to the anterior odontoid screw. This may even cause their perforation, which could be fatal if not treated carefully with help from other specialties .