11.3.3\ Implantable Bone Stimulators

11.3.3.1\ Discussion

Implantable (internal) bone stimulators are devices that deliver electrical currents to promote bone growth and healing and to expedite fusion. This device consists of electrodes that are positioned in contact with the site of spinal fusion and a small power source that is implanted in the subcutaneous tissues (Fig. 11.31). The role of imaging is to confirm proper positioning of the electrodes and assess progression of bony fusion or healing.

Fig. 11.31  Bone stimulator. Lateral radiograph shows the leads in contact with the fusion masses and the battery pack (arrow) implanted in the subcutaneous tissues

11.3.4\ Odontoid Screw Fixation

11.3.4.1\ Discussion

Anterior fixation of odontoid fractures consists of securing the fracture fragment with one or two lag or cortical screws depending on the diameter of the dens. A lag screw is used in order to help reduce the fracture. Complications of this ­procedure include hematomas, dysphagia, hoarseness, and vascular, spinal cord, or nerve root injuries. Radiographs and/or CT may be obtained for follow-­up, especially in order to assess for union (Fig. 11.32). The tip of the screw can often safely project beyond the posterosuperior edge of the dens by several millimeters. Other options for treating odontoid fractures include posterior spinal fusion or halo-vest immobilization.

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