An Anatomic, Radiographic, And Biomechanical Study Of Costotransverse Unit Approach For Thoracic Fixation Posteriorly

Pedicle screw constructs achieve superior correction for thoracic deformity when compared to conventional techniques of hook or wire fixation. A lot of anatomic studies have cautioned against imprudent use of pedicle screws because of the proximity to the spinal cord, the trajectory of the screws and the small margin for error. Concerns have been raised regarding the safety of pedicle screw instrumentation in those patients with idiopathic scoliosis who have more complex and varied thoracic pedicles. Use of the thoracic spine in those with scoliosis is not without danger. Given that many patients that will have pedicles too narrow or complex to accommodate transpedicular fixation, a safe alternative incorporating screw fixation in the thoracic spine allowing for application in this excluded population is sought.A new concept of extrapedicular fixation has been introduced recently. This new extrapedicular method would retain many of the benefits of the transpedicular construct including the properties of three column fixation with rigidity near transpedicular fixation, yet would diminish the risk of injury to surrounding structures. This technique utilizes costotransverse unit space fully, inserting the screw from costotransverse unit space and entering the bone of the vertebral body. However, recent researches focus on the width of costotransverse unit without considering its height. It is difficult to control screw direction in the course of placement of screw. There is no ideal solution to this question. Rigorous biomechanical examination of the extrapedicular screw technique is currently lacking. In the current study, we investigate costotransverse unit as a three-dimensional structure including width and height, study how to ascertain the direction of screw by anatomic, radiographic and biomechanical method to ascertain whether costotransverse unit screw...