Fig. 1.

Schematic diagram showing the surgical technique. Panel A shows how the cord is compressed in fractured and displaced odontoid process. Arrows indicate the lines of force leading to displacement of dens and compression of the cord. The dens slips forward and is ‘wedged’ between the C2 body and C1 arch. Panel B shows the first step of surgery. Here first, the posterior arch of C1 is drilled. (C) This is followed by decompression of the cord dorsally. (D) Following this, the C1 lateral mass is drilled out completely. The author prefers to first separate the C1–2 joint using an instrument like a periosteal elevator. The drilling of the C1 lateral mass may be performed through the C1–2 joint by starting at the inferior surface of the C1 joint. (E) This is followed by the placement of a spacer (polyetheretherketone, PEEK) between the occiput and C2 joints. (F) The spacer now acts like a fulcrum of a type II pivot joint. Thus, a compressive force (converging arrows, F) now applied between the occiput and the C2 will lead to the forward movement of the C2 body. This forms the fundamental principle of distraction, compression extension, and reduction. (F) Next, a temporary screw is placed over the occiput. Compression is now provided by placing the arms of the calipers between the inferior surface of C2 and an offset placed over the occipital screw (converging arrows, F). Now acting like a fulcrum (F), the spacer moves the C2 body forwards and ‘slips it’ under the fractured dens. (G) Final fixation is now provided by connecting a rod between the occiput and C2 translaminar screw. In 1 case (case 3, Table 1), both laminar and pars screws were provided on C2. It should be noted that this technique is only advised for patients with chronic displaced odontoid fracture, which causes severe cord compression by becoming wedged between the C1 arch and the body of the C2. S, spinal cord; O, occiput; D, dens; C1, C1 anterior arch; PC1, posterior arch of C1.