Pedicle Screw Safety

How Much Anterior Breach Is Safe? A Cadaveric and CT-Based Study

Vishal Sarwahi, Monica Payares, Rachel Gecelter, Stephen Wendolowski, Kathleen Maguire, Dan Wang, Beverly Ann Thornhill, Terry Amaral

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

STUDY DESIGN.: Clinical retrospective chart review and basic science study OBJECTIVES.: To determine the safety limits of an anterior/anterorolateral misplaced pedicle screw on CT scan in spinal deformity. SUMMARY OF BACKGROUND DATA.: While the limits of medial breaches (<4?mm) are known, the safe limits for anterior/anterolateral breaches in spine deformity are not yet defined. METHODS.: This study had two parts. In part I, post-operative 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, 8 cadavers were instrumented with 6?×?30?mm 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. 31(26.7%) were adjacent to vital structures. Fisherʼs exact test showed ≤4?mm breach has significantly lower likelihood of impingement (p?<?0.001). Screws adjacent/impinging the aorta protruded an average 5.7?±?0.6?mm, while 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; 13 were contained in bone. All 23 screws did not endanger any structures and protruded?<?4?mm on CT scan. CONCLUSION.: Anterior/anterolateral breaches ≤4?mm on CT poses no significant risk of impingement and therefore can be considered safe.Level of Evidence: 3

Original languageEnglish (US)
JournalSpine
DOIs
StateAccepted/In press - Mar 14 2017

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Aorta
Dissection
Spine
Safety
Cadaver
Bone and Bones
Pedicle Screws
Radiologists

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Clinical Neurology

Cite this

Sarwahi, V., Payares, M., Gecelter, R., Wendolowski, S., Maguire, K., Wang, D., ... Amaral, T. (Accepted/In press). Pedicle Screw Safety: How Much Anterior Breach Is Safe? A Cadaveric and CT-Based Study. Spine. https://doi.org/10.1097/BRS.0000000000002153

Pedicle Screw Safety : How Much Anterior Breach Is Safe? A Cadaveric and CT-Based Study. / Sarwahi, Vishal; Payares, Monica; Gecelter, Rachel; Wendolowski, Stephen; Maguire, Kathleen; Wang, Dan; Thornhill, Beverly Ann; Amaral, Terry.

In: Spine, 14.03.2017.

Research output: Contribution to journalArticle

Sarwahi V, Payares M, Gecelter R, Wendolowski S, Maguire K, Wang D et al. Pedicle Screw Safety: How Much Anterior Breach Is Safe? A Cadaveric and CT-Based Study. Spine. 2017 Mar 14. https://doi.org/10.1097/BRS.0000000000002153
Sarwahi, Vishal ; Payares, Monica ; Gecelter, Rachel ; Wendolowski, Stephen ; Maguire, Kathleen ; Wang, Dan ; Thornhill, Beverly Ann ; Amaral, Terry. / Pedicle Screw Safety : How Much Anterior Breach Is Safe? A Cadaveric and CT-Based Study. In: Spine. 2017.
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abstract = "STUDY DESIGN.: Clinical retrospective chart review and basic science study OBJECTIVES.: To determine the safety limits of an anterior/anterorolateral misplaced pedicle screw on CT scan in spinal deformity. SUMMARY OF BACKGROUND DATA.: While the limits of medial breaches (<4?mm) are known, the safe limits for anterior/anterolateral breaches in spine deformity are not yet defined. METHODS.: This study had two parts. In part I, post-operative 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, 8 cadavers were instrumented with 6?×?30?mm 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. 31(26.7{\%}) were adjacent to vital structures. Fisherʼs exact test showed ≤4?mm breach has significantly lower likelihood of impingement (p?<?0.001). Screws adjacent/impinging the aorta protruded an average 5.7?±?0.6?mm, while 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; 13 were contained in bone. All 23 screws did not endanger any structures and protruded?<?4?mm on CT scan. CONCLUSION.: Anterior/anterolateral breaches ≤4?mm on CT poses no significant risk of impingement and therefore can be considered safe.Level of Evidence: 3",
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AU - Sarwahi, Vishal

AU - Payares, Monica

AU - Gecelter, Rachel

AU - Wendolowski, Stephen

AU - Maguire, Kathleen

AU - Wang, Dan

AU - Thornhill, Beverly Ann

AU - Amaral, Terry

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