Novel Approach Toward Pedicle Screw Placement in the Thoracic Spine

International Spinal Development & Research Foundation, Las Vegas, Nevada, USA

PURPOSE: Due to the smaller size of the thoracic pedicle, primarily in the coronal plane, most surgeons have opted to avoid the used of transpedicular screws in the thoracic spine. A new technique for placement of screws through thoracic pedicles with and without lateral wall violation is described.

MATERIALS & METHODS: From April 1992 through February 1999, 1064 pedicle screws per placed within the thoracic spine of 137 patients. Primary diagnoses included: scoliosis (59), fracture (41), kyphosis (16), tumor (12), pseudarthrosis (6), ankylosing spondylitis (2), and infection (1). Small posterior laminotomies were made at each level. A ball probe was utilized to identify the medial and inferior wall of the pedicle at each location. In general, 5 mm diameter screws of 30-35 mm in length were placed utilizing a two-man technique. Screws were placed in a lateral to medial direction with the entry site being just lateral to the boundaries of the pedicle over the posterior laminar ridge. Through the laminotomies performed at each level, all walls of the pedicle with the exception of the lateral walls, were directly inspected and ensured not to be violated by instrumentation.

RESULTS: Mean follow-up was 64 months (range 24-106 months). Construct failure included 4 misplaced screws, 5 loose screws, 3 broken rods and 2 loose nuts for a total implant complication rate of 1.3% (12/1064). There was 1 transient thoracic radiculopathy with complete resolution; 1 transient posterior cord syndrome with subsequent resolution and retention of instrumentation; and 1 transient partial cord injury following attempted reduction of complex scoliosis due to probable traction and vascular insult. With the exception of 1 transient thoracic radiculopathy, there were no identified neurologic deficits directly due to screw placement within the thoracic spine. The Transient Neurologic complication rate was 2.2% (3/137).

CONCLUSIONS: A new technique for placement of transpedicular screws through a posterior approach in the thoracic spine is described. It is a safe and reliable technique with low morbidity. Screws can be placed larger than the size of the width of the pedicle without neurologic or vascular injury while generally maintaining adequate purchase and construct stability. Use of screws placed posteriorly in the thoracic spine is attractive in that improved segmental control can be obtained over that of the standard hook or wire construct.