Anatomic considerations of costotransverse screw placement in the thoracic spine.

BACKGROUND Numerous techniques have been reported to restore spinal stability and to correct spinal deformities, including rods with wires/hooks, and rods or plates with pedicular screws. It was thought that posterior fixation of the thoracic spine through the costotransverse joint may be another alternative. METHODS Nine cadavers were obtained for study of screw fixation of the costotransverse joint for posterior thoracic instrumentation. The entrance point for screw insertion was designed to be at the posterior center of the clubbed extremity of the transverse process. From this point, a 3-mm drill bit was used to create the screw path penetrating the costotransverse joint and the ventral cortex of the rib. Under direct visualization of the costotransverse joint, the drill bit was directed parallel to the sagittal plane and toward the upper portion of the rib. Measurements included the screw path length and sagittal angulation. Also, the distance between the superior borders of the transverse process and the tubercle of the rib and the anatomic relationship of the drill bit exit to the intercostal vessels and nerves were evaluated. RESULTS The maximum length of the screw path was found at T1 (19.7 mm), whereas the minimum length was noted at T4-T5 (13.9 mm). This value decreased gradually from T1 to T4-T5, and slightly increased to T10. The larger sagittal angles of the screw path were found at the levels of T1-T4 (78-86 degrees ), whereas the smaller were noted at the levels below T5 (53-61 degrees ). The mean distance between the superior borders of the transverse process and the tubercle of the rib was smaller at T1-T5 (0.2-0.4 mm), and significantly increased to T8 (5. 1 mm), and then slightly decreased to T10. The variation of this parameter was remarkable. All of the exit points for the drill bit were located in the upper half of the rib, and away from the intercostal vessels. CONCLUSIONS The ideal screw orientation is parallel to the sagittal plane, and angled 80-90 degrees relative to the frontal plane for T1-T4 and 50-70 degrees for T5-T10 superiorly, starting at the posterior center of the transverse process. Costotransverse screw fixation in the thoracic spine may be an alternative to pre-existing methods.

[1]  R. Winter,et al.  Adult idiopathic scoliosis treated with Luque or Harrington rods and sublaminar wiring. , 1989, The Journal of bone and joint surgery. American volume.

[2]  R. Winter,et al.  Scheuermann's kyphosis. Results of surgical treatment by posterior spine arthrodesis in twenty-two patients. , 1975, The Journal of bone and joint surgery. American volume.

[3]  Bernice B. Capusten,et al.  Gray's Anatomy. 37th ed , 1990 .

[4]  D. Green,et al.  Scheuermann's kyphosis. , 1999, Current opinion in pediatrics.

[5]  C. K. Lee,et al.  Segmental Pedicle Screw Fixation in the Treatment of Thoracic Idiopathic Scoliosis , 1995, Spine.

[6]  J N Weinstein,et al.  Anatomic and technical considerations of pedicle screw fixation. , 1992, Clinical orthopaedics and related research.

[7]  Casey K. Lee,et al.  Surgical Treatment of Tumors of the Spine , 1986, Spine.

[8]  J W Frymoyer,et al.  An internal fixator for posterior application to short segments of the thoracic, lumbar, or lumbosacral spine. Design and testing. , 1986, Clinical orthopaedics and related research.

[9]  F. Denis.  Cotrel-Dubousset instrumentation in the treatment of idiopathic scoliosis. , 1988, The Orthopedic clinics of North America.

[10]  D. Bradford,et al.  Harrington instrumentation and spine fusion for unstable fractures and fracture-dislocations of the thoracic and lumbar spine. , 1977, The Journal of bone and joint surgery. American volume.

[11]  A. Nachemson,et al.  A locking hook spinal rod system for stabilization of fracture-dislocations and correction of deformities of the dorsolumbar spine. A biomechanic evaluation. , 1984, Clinical orthopaedics and related research.

[12]  Harrington Pr.  Technical details in relation to the successful use of instrumentation in scoliosis. , 1972 .

[13]  C. Dickman,et al.  A Historical Cohort Study of Pedicle Screw Fixation in Thoracic, Lumbar, and Sacral Spinal Fusions. , 1994, Spine.

[14]  B. Stener,et al.  Complete removal of three vertebrae for giant-cell tumour. , 1971, The Journal of bone and joint surgery. British volume.

[15]  J Dubousset,et al.  NEW UNIVERSAL INSTRUMENTATION IN SPINAL SURGERY , 1988, Clinical orthopaedics and related research.

[16]  W. Hutton,et al.  Pedicle and transverse process screws of the upper thoracic spine. Biomechanical comparison of loads to failure. , 1999, Spine.