Spine Journal: Article on Safe Thoracic Pedicle screw placedment

Thoracic pedicle screw placements especially the upper thoracic levels do not have specific  muscle innervation making it difficult to test pedicle screws, in other words it is not as discrete as you can do a test on for example Deltoid (Cervical) or Tibialis anterior (lumbar). The following article though

Spine (Phila Pa 1976). 2012 

Safe pedicle screw placement in thoracic scoliotic curves using t-EMG: stimulation threshold variability at concavity and convexity in apex segments.

de Blas G, Barrios C, Regidor I, Montes E, Burgos J, Pizá-Vallespir G, Hevia E.

Source

Department of Clinical Neurophysiology, Hospital Ramón y Cajal, Madrid, Spain.

Abstract

STUDY DESIGN:

A cross-sectional study of nonconsecutive cases (level III evidence).

OBJECTIVE:

In a series of young patients with thoracic scoliosis who were treated with pedicle screw constructs, data obtained from triggered electromyography (t-EMG) screw stimulation and postoperative computed tomographic scans were matched to find different threshold limits for the safe placement of pedicle screws at the concavity (CC) and convexity (CV) of the scoliotic curves. The influence of the distance from the medial pedicle cortex to the spinal cord on t-EMG threshold intensity was also investigated at the apex segment.

SUMMARY OF BACKGROUND DATA:

Whether the t-EMG stimulation threshold depends on pedicle bony integrity or on the distance to neural tissue remains elusive. Studying pedicle screws at the CC and CV at the apex segments of scoliotic curves is a good model to address this issue because the spinal cord is displaced to the CC in these patients.

Mar 15;37(6):E387-95. doi: 10.1097/BRS.0b013e31823b077b.