Outcome-Based Classification for Assessment of Thoracic Pedicular Screw Placement

Abstract

The literature shows consensus over high rates of pedicle screw misplacement, but low clinical complications, in the hands of the best of spine surgeons. The concept of acceptable screw placements and the outcome classification makes the pedicle screw assessment results correlate better with the clinical outcome.

Radiological and clinical outcome of screw placement in adolescent idiopathic scoliosis: evaluation with low-dose computed tomography

“…We believe that pedicle screws with ACP with the screw tip in the vicinity of aorta need to be followed up with a suitable imaging modality, for example CT-angiography, to exclude the development of pseudoaneurysm. We believe that adopting the new grading system (based on whether the cortical violation is partial or total rather than measuring the misplacement in millimeters and regarding the screw misplacement of less than half screw diameter as ''acceptable'') is more practical and easy to perform for research purposes as well as in clinical practice as: (1) pedicle perforation of B2 mm (almost half screw diameter) is considered harmless [3]. (2) The pedicular width in the thoracic spine may be as small as 2.6 mm [13], which means that many pedicle screws are inclined for misplacement regardless of the skilfulness of the operating surgeon as screw diameter varies between 4.5 and 5.5 mm, and (3) avoiding measurements in millimeter and submillimeter reduces the influence of individual variations and avoids the inherent error of measurements when these are performed in the Picture Archiving and Communication System (PACS).…”

“…The overall rate of misplacement reported in this study was 17%. Five of the studies dealing with assessment of pedicular screw placement in scoliosis showed a misplacement rate of 5.7, 50.7, 25, 29.1, and 18.5% [1,3,9,20,22].…”

“…The rate of screw misplacement in the thoracic region has been reported to vary from 5.7 to 50%, whereas the rate of neurovascular complications ranges from 0 to 1% [1,3,[9][10][11]. In almost all reports no complications have been reported when pedicle breach was less than 2 mm and a potential for neurological complication was believed to exist only when medial wall perforation exceeds 4 mm [3].…”

“…Assessment of misplacement of pedicle screws in patients with adolescent idiopathic scoliosis (AIS) has been reported in many studies [1][2][3]. Computed tomography (CT) is the best method of performing such an assessment and in one study showed ten times as many pedicle violations as did plain radiography [4].…”

“…In almost all reports no complications have been reported when pedicle breach was less than 2 mm and a potential for neurological complication was believed to exist only when medial wall perforation exceeds 4 mm [3]. Regarding grading systems for assessment of screw placement, up to 35 methods have been used for this purpose [12].…”