Lateral Extrapedicular Screw Fixation in the Thoracic Spine

Pedicle instrumentation has become a preferred anchoring method for instrumentation systems utilizing rods and/or plates in the lower thoracic and lumbar spine. Such fixation in the thoracic spine has not been frequently used. The size of the thoracic pedicles and increased chance of neurological injury has not made such an often–used procedure. The use of three–point fixation in the thoracic spine provides for a more stable fixation than hook/wire techniques. Presented is our experience of using extrapedicular screw fixation throughout the thoracic spine. The screw insertion site is located at the transverse process tip at the transversocostal articulation. The transverse process is removed and a curette is directed medial to the transversocostal articulation. Following screw insertion, fluoroscopy is obtained to verify the screw locations. Screws ranging from 4.0–5.5mm diameter and 25–40mm length were used. Such fixation has been used for trauma, infection and neoplasm. The lateral extrapedicular technique offers several benefits over conventional techniques. The length of the construct is shortened and spares unaffected adjacent motion segments. The screw placement is lateral to the spinal canal and thus no encroachment into the canal or onto the dura, as with hooks and wires. This technique allows use of a screw diameter independent of the size of a pedicle. Extrapedicular screws course through several cortices. In conclusion, the lateral extrapedicular technique is safe, providing the surgeon understands the anatomy of the thoracic spine and preoperative CT scans are obtained to better understand the bony anatomy.