Cannulated Double-Threaded Compression Screw (Herbert-Type) Fixation for Displaced Odontoid Fracture

Abstract

Direct anterior screw fixation of a displaced odontoid fracture (OF) has been indicated for reasonable method of treatment. We have experienced three cases of displaced OF, in which fractured dens were fixed by one cannulated double-threaded compression screw. We present cases, operative techniques and advantages of this type of screw in comparison with the cancellous bone screw used in our early cases. Two cases showed posterior-displaced Anderson Type II OF and one case showed anteriorly displaced shallow Type III OF. The head was retracted to be positioned with fracture-fragment alignment in the best possible reduction. Small part the antero-inferior portion of the dens body was drilled out. Under simultaneous antero-posterior and lateral fluoroscopic control, a guide pin was introduced to penetrate the cortex of distal end of the dens. Following the trajectory of the guide pin, drilling, tapping and then a screw implantation were manipulated. The double-threaded screw with pitch difference between the front and back threads produced compression force across the fracture line and thus rigid internal fixation. All cases showed excellent placement of screws and no nonunion during following period of 12 months. The present surgical method seems to be optimal for displaced OF rather than the anterior fixation method using conventional type of screw or posterior arthrodesis.