Thoracic Pedicle Screw Fixation Research Articles

Technique of thoracic pedicle screw fixation for trauma

Thoracic fractures after trauma can lead to devastating neurological injury because of the close relationship among spinal cord, nerve roots, and their bony surroundings. Transpedicular fixation using pedicle screws in the thoracic spine is technically challenging but can be done safely and effectively if surgeons understand the complex anatomy of the region and adhere to biomechanical principles. This article discusses different approaches for placing pedicle screws in the thoracic spine and presents some case examples that demonstrate the technique. Surgeons involved with the operative management of spine trauma should become familiar with the placement of thoracic pedicle screws. The technique requires a thorough understanding of the anatomy of the region and the techniques used for placing instrumentation.

Use of the Anatomic Trajectory for Thoracic Pedicle Screw Salvage After Failure/Violation Using the Straight-Forward Technique: A Biomechanical Analysis

A biomechanical study of cadaver vertebrae to determine the feasibility of obtaining adequate thoracic pedicle screw fixation in a salvage situation. OBJECTIVE To investigate the ability to safely place a thoracic pedicle screw with adequate maximal insertional torque (MIT) using the anatomic trajectory (AT) (directed along the true anatomic axis of the pedicle) after purposeful failure/medial violation of the pedicle using the straight-forward trajectory (ST) (paralleling the vertebral endplate). Failure to place a pedicle screw at an intended segment of the thoracic spine may theoretically render the level uninstrumented, because pedicle hook placement may be unsafe and the transverse process may be fractured. An alternative pedicle screw insertion technique, if biomechanically sound in this situation, may present an excellent alternative for critical instrumentation levels. Fixed-head 5.0 mm stainless steel pedicle screws were placed using the ST and MIT was recorded after determination of bone mineral density (BMD) with dual-energy radiograph absorptiometry (DEXA) scanning. Purposeful screw malposition and critical pedicle wall failure were performed, followed by salvage placement of the screw using the AT. Insertional torque was recorded for each screw revolution with a digital torque wrench and MIT was again recorded to compare the MIT obtainable in the salvage situation. BMD for the vertebrae averaged 732 g/cm2 (620-884 g/cm2). The MIT for the straight-forward technique without pedicle violation was 2.61 +/- 0.19 (SE) inches per pound, whereas that of the salvage procedure after medial wall violation (AT) averaged 1.62 +/- 0.12 (SE) inches per pound. Therefore, the AT achieved 62% (P = 0.027) of the fixation strength (in terms of MIT) during salvage after failure/medial violation of the pedicle. MIT for both the ST* and AT trajectories correlated with both global BMD of the vertebrae (*P = 0.008; P = 0.004) and regional BMD of the vertebral body (*P = 0.044; P = 0.023). The AT achieved 62% (P = 0.027) of the MIT during salvage of a failed/violated pedicle. BMD correlated with both the initial and salvage techniques. The AT provides adequate fixation in a salvage situation and may be safely used to provide segmental fixation at critical levels.

Thoracic pedicle screw fixation for spinal deformity

Techniques to improve segmental fixation have advanced the ability to correct complex spinal deformity. The purpose of instrumentation is to correct spinal deformity or to stabilize the spine to enhance the long-term biological fusion. The ultimate goal of spinal deformity surgery is the creation of a stable, balanced, pain-free spine centered over the pelvis in the coronal and sagittal planes. The minimum number of segments should be fused. These concepts remain challenging in the setting of deformity and instability. Successful results can be obtained if the surgeon understands the technology available, its capabilities, biological limitations, and the desired solution. The authors prefer to use thoracic pedicle screws when treating patients with spinal deformity because they provide greater corrective forces for realignment. This allows shorter-segment constructs and the possibility of true derotation in correction. In this article the authors focus on the use of thoracic transpedicular screw fixation in the management of complex spinal disorders and deformity.