How To Judge If The Pedicle Is Large Enough To Instrument?
1. Plain radiogaphs – check pedicles in proximal thoracic, lower thoracic, and upper lumbar Scoliosis – check all convex apical pedicles if they are at least 5 mm in diameter, the concave ones are probably large enough to place screws Kyphosis – check x-rays of proximal thoracic and lower thoracic spine, in particular, the frontal plane of the vertebra. Often, the true AP radiograph only profiles the apical 2 or 3 segments. It appears that there is definitely some plasticity to the pedicles such that one can often get a 1-2 mm larger screw diameter completely intraosseous than one could measure on x-ray or CT scan. 2. CT scans – not routinely done preop need to get perpendicular to the plane of vertebra O’Brien, Lenke et al study showed that main pedicle diameter is between 4-6 mm in thoracic scoliosis 3. MRI scan – Liljenqvist et al found the mean concave pedicle lift to be between 2.4-5.5 mm on the concavity, and between 2.3-6.0 mm on the convexity. IV. Pitfalls 1. Pedicle not large
