An anatomical study of transpedicular vs. extrapedicular approach for kyphoplasty and vertebroplasty in the thoracic spine.

Introduction: Percutaneous vertebral augmentation is a common therapeutic approach for osteoporotic or osteolytic vertebral fractures. Due to the variable pedicle anatomy two different approaches, the transpedicular and the extrapedicular approach have been established. In particular, in the middle and upper thoracic spine, percutaneous procedures are challenging because of difficult visualisation of anatomical landmarks and a more unfavourable anatomy with smaller and differently orientated pedicles.

Material And Methods: In our cadaveric study we compared the transpedicular and the extrapedicular approach to the thoracic spine. In 26 cadaveric spine specimes, embalmed using Thiel's method, we placed a total of 486 trans- and extrapedicular K-wires through Jamshidi needles in the vertebral bodies T4 - T12 under fluoroscopy. A CT scan was then performed to verify the actual position of the K-wire. Malpositioning was defined as deviation from the planned approach or placement of the K-wire in the spinal canal or outside the vertebral body. Number and direction of malpositionings was recorded.

Results: Malpositioning occurred in 68 of 468 K-wires. It was more frequent in the transpedicular (54) than in the extrapedicular (14) approach. Intraspinal malposition was seen more often in the transpedicular approach (n=36) especially in the upper and middle thoracic spine.

Conclusion: In summary both approaches are relatively safe but in the upper and middle thoracic spine the risk of intraspinal malpositioning seems to be lower when using the extrapedicular approach.