TY - JOUR
T1 - Pedicle Screw Safety
T2 - How Much Anterior Breach Is Safe?
AU - Sarwahi, Vishal
AU - Payares, Monica
AU - Wendolowski, Stephen
AU - Gecelter, Rachel
AU - Maguire, Kathleen
AU - Wang, Dan
AU - Thornhill, Beverly
AU - Amaral, Terry
N1 - Publisher Copyright:
© 2017 Wolters Kluwer Health, Inc. All rights reserved.
PY - 2017/11/15
Y1 - 2017/11/15
N2 - Study Design. Clinical retrospective chart review and basic science study. Objectives. To determine the safety limits of an anterior/anterorolateral misplaced pedicle screw on computed tomography (CT) scan in spinal deformity. Summary of Background Data. Although the limits of medial breaches (<4 mm) are known, the safe limits for anterior/anterolateral breaches in spine deformity are not yet defined. Methods. The present study had two parts. In part I, postoperative CT scans of 165 patients operated on for spine deformity were reviewed for screw misplacement (2800 screws). The amount of anterior/anterolateral breach was measured. Protrusions were also evaluated for proximity to vital structures. All scans were reviewed by musculoskeletal radiologist. In part II, eight cadavers were instrumented with 6×30 and 6×40 mm bilaterally from T1-S1. Screws were randomly inserted under navigation guidance either "IN" or "OUT-anterior/lateral." CT scan was performed, followed by gross dissection to determine screw position. Results. Part I: 116(4.2%) screws were misplaced anterior/anterolaterally. Thirty-one (26.7%) were adjacent to vital structures. Fisher exact test showed 4 mm or less breach has significantly lower likelihood of impingement (P<0.001). Screws adjacent/impinging the aorta protruded an average 5.7±0.6 mm, whereas screws not involving the aorta breached an average 3.9±0.2 mm, (P<0.001). Part II: 285 screws were inserted. On CT scan, 125 were misplaced anterior/anterolaterally. On gross dissection, 89 were visibly misplaced; 23 were covered entirely by soft tissue but were palpable; and 13 were contained in bone. All 23 screws did not endanger any structures and protruded less than 4mm on CT scan. Conclusion. Anterior/anterolateral breaches of 4 mm or less on CT poses no significant risk of impingement and therefore can be considered safe.
AB - Study Design. Clinical retrospective chart review and basic science study. Objectives. To determine the safety limits of an anterior/anterorolateral misplaced pedicle screw on computed tomography (CT) scan in spinal deformity. Summary of Background Data. Although the limits of medial breaches (<4 mm) are known, the safe limits for anterior/anterolateral breaches in spine deformity are not yet defined. Methods. The present study had two parts. In part I, postoperative CT scans of 165 patients operated on for spine deformity were reviewed for screw misplacement (2800 screws). The amount of anterior/anterolateral breach was measured. Protrusions were also evaluated for proximity to vital structures. All scans were reviewed by musculoskeletal radiologist. In part II, eight cadavers were instrumented with 6×30 and 6×40 mm bilaterally from T1-S1. Screws were randomly inserted under navigation guidance either "IN" or "OUT-anterior/lateral." CT scan was performed, followed by gross dissection to determine screw position. Results. Part I: 116(4.2%) screws were misplaced anterior/anterolaterally. Thirty-one (26.7%) were adjacent to vital structures. Fisher exact test showed 4 mm or less breach has significantly lower likelihood of impingement (P<0.001). Screws adjacent/impinging the aorta protruded an average 5.7±0.6 mm, whereas screws not involving the aorta breached an average 3.9±0.2 mm, (P<0.001). Part II: 285 screws were inserted. On CT scan, 125 were misplaced anterior/anterolaterally. On gross dissection, 89 were visibly misplaced; 23 were covered entirely by soft tissue but were palpable; and 13 were contained in bone. All 23 screws did not endanger any structures and protruded less than 4mm on CT scan. Conclusion. Anterior/anterolateral breaches of 4 mm or less on CT poses no significant risk of impingement and therefore can be considered safe.
KW - AIS
KW - adolescent idiopathic scoliosis
KW - anterior breach
KW - anterior breach safe zone
KW - aorta
KW - pedicle screw
KW - pedicle screw safety
KW - screw misplacement
KW - vital structures
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U2 - 10.1097/BRS.0000000000002153
DO - 10.1097/BRS.0000000000002153
M3 - Article
C2 - 28296814
AN - SCOPUS:85015159238
SN - 0362-2436
VL - 42
SP - E1305-E1310
JO - Spine
JF - Spine
IS - 22
ER -