Evaluation of a more ventral starting point for thoracic pedicle screws: higher maximal insertional arc and more medial and safer screw angulation

Restricted access

OBJECTIVE

To demonstrate that a more ventral starting point for thoracic pedicle screw insertion, produced by aggressively removing the dorsal transverse process bone down to the superior articular facet (SAF), results in a larger margin for error and more medial screw angulation compared to the traditional dorsal starting point (DSP). The margin for error will be quantified by the maximal insertional arc (MIA).

METHODS

The study population included 10 consecutive operative patients with adult idiopathic scoliosis who underwent primary surgery. All measurements were performed using 3D visualization software by an attending spine surgeon. The screw starting points were 2 mm lateral to the midline of the SAF in the mediolateral direction and in the center of the pedicle in the cephalocaudal direction. The DSP was on the dorsal cortex. The ventral starting point (VSP) was at the depth of the SAF. Measurements included distance to the pedicle isthmus, MIA, and screw trajectories.

RESULTS

Ten patients and 110 vertebral levels (T1–11) were measured. The patients’ average age was 41.4 years (range 18–64 years). The pedicle isthmus was largest at T1 (4.04 ± 1.09 mm), and smallest at T5 (1.05 ± 0.93 mm). The distance to the pedicle isthmus was 7.47 mm for the VSP and 11.92 mm for the DSP (p < 0.001). The MIA was 15.3° for the VSP and 10.1° for the DSP (p < 0.001). Screw angulation was 21.7° for the VSP and 16.8° for the DSP (p < 0.001).

CONCLUSIONS

A more ventral starting point for thoracic pedicle screws results in increased MIA and more medial screw angulation. The increased MIA represents an increased tolerance for error that should improve the safety of pedicle screw placement. More medial screw angulation allows improved triangulation of pedicle screws.

ABBREVIATIONS DSP = dorsal starting point; MIA = maximal insertional arc; SAF = superior articular facet; VSP = ventral starting point.

Article Information

Correspondence Lawrence G. Lenke: The Spine Hospital, NewYork-Presbyterian/Allen, New York, NY. ll2989@cumc.columbia.edu.

INCLUDE WHEN CITING Published online December 14, 2018; DOI: 10.3171/2018.8.SPINE18175.

J.D.L. and C.W. share first authorship of this work.

Disclosures Dr. Lenke receives research support from AOSpine, Scoliosis Research Society, EOS, and Setting Scoliosis Straight Foundation. Dr. Lenke is a paid consultant for and/or received royalties from Medtronic, DePuy, K2M, Quality Medical Pub. Dr. Lenke is on the editorial or governing board of Journal of Neurosurgery: Spine, Spine Deformity Journal, Spine, Scoliosis, Journal of Spinal Disorders & Techniques, www.iscoliosis.com, www.spineuniverse.com, Backtalk (Scoliosis Association), Global Spine Outreach, and Orthopaedic Research and Education Foundation. Dr. Lenke also reports having received reimbursement for airfare/hotel from Broadwater, the Seattle Science Foundation, Stryker Spine, and the Spinal Research Foundation; grant support from EOS; and philanthropic research funding from the Fox Family Foundation and Evans Family Donation; and serving as an expert witness in a patent infringement case for Fox Rothschild, LLC.

Dr. Lehman is on the editorial or governing board of Spine Deformity, The Spine Journal, AOSpine, Cervical Spine Research Society, North American Spine Society, and Scoliosis Research Society. Dr. Lehman is a paid presenter, consultant, or speaker for DePuy, a Johnson & Johnson Company; Medtronic; and Stryker. Dr. Lehman receives publishing royalties from Wolters Kluwer Health–Lippincott Williams & Wilkins.

© AANS, except where prohibited by US copyright law.

Headings

Figures

  • View in gallery

    Sawbones model demonstrating the area of dorsal transverse bone to be removed (circled in black with marking pen) to access the VSP. Figure is available in color online only.

  • View in gallery

    Intraoperative images demonstrating key steps of freehand pedicle screw insertion using the VSP technique. A: Exposure of dorsal bony landmarks to the tips of the transverse process. B: A large Leksell rongeur is placed with one jaw on the superior articular facet to set the depth of bone removal. C: Removal of dorsal transverse process bone to the depth of the superior articular facet. D: Creation of pilot hole with a matchstick burr. E: Cannulation of the pedicle with a thoracic gearshift probe. F: Insertion of pedicle screw. Figure is available in color online only.

  • View in gallery

    Determination of starting point on the left pedicle of the T8 vertebra. Left: The mediolateral position of the starting point is 2 mm lateral to the midline of the SAF. Right: The cephalocaudal position is in the center of the pedicle. The VSP is marked by blue/green crosshairs. The DSP is marked by the tip of the white arrow. Figure is available in color online only.

  • View in gallery

    MIA from VSP (blue) and DSP (pink). degs = degrees. Figure is available in color online only.

  • View in gallery

    Mean pedicle isthmus. The y-axis values are mean endosteal diameter measurements in millimeters. Figure is available in color online only.

  • View in gallery

    Distance from starting point to isthmus. The y-axis values are mean distance measurements in millimeters. SP = starting point. Figure is available in color online only.

  • View in gallery

    Maximal insertional arc. The y-axis values are mean MIA measurements in degrees. Figure is available in color online only.

  • View in gallery

    Screw angles. The y-axis values are mean angle measurements in degrees. Figure is available in color online only.

References

1

Barber JWBoden SDGaney THutton WC: Biomechanical study of lumbar pedicle screws: does convergence affect axial pullout strength? J Spinal Disord 11:2152201998

2

Cho WCho SKWu C: The biomechanics of pedicle screw-based instrumentation. J Bone Joint Surg Br 92:106110652010

3

Davis CMGrant CAPearcy MJAskin GNLabrom RDIzatt MT: Is there asymmetry between the concave and convex pedicles in adolescent idiopathic scoliosis? A CT investigation. Clin Orthop Relat Res 475:8848932017

4

Dede OWard WTBosch PBowles AJRoach JW: Using the freehand pedicle screw placement technique in adolescent idiopathic scoliosis surgery: what is the incidence of neurological symptoms secondary to misplaced screws? Spine (Phila Pa 1976) 39:2862902014

5

Dhawan AKlemme WRPolly DW Jr: Thoracic pedicle screws: comparison of start points and trajectories. Spine (Phila Pa 1976) 33:267526812008

6

Di Silvestre MParisini PLolli FBakaloudis G: Complications of thoracic pedicle screws in scoliosis treatment. Spine (Phila Pa 1976) 32:165516612007

7

Diab MSmith ARKuklo TR: Neural complications in the surgical treatment of adolescent idiopathic scoliosis. Spine (Phila Pa 1976) 32:275927632007

8

Fennell VSPalejwala SSkoch JStidd DABaaj AA: Freehand thoracic pedicle screw technique using a uniform entry point and sagittal trajectory for all levels: preliminary clinical experience. J Neurosurg Spine 21:7787842014

9

Gaines RW Jr: The use of pedicle-screw internal fixation for the operative treatment of spinal disorders. J Bone Joint Surg Am 82-A:145814762000

10

Gautschi OPSchatlo BSchaller KTessitore E: Clinically relevant complications related to pedicle screw placement in thoracolumbar surgery and their management: a literature review of 35,630 pedicle screws. Neurosurg Focus 31(4):E82011

11

Kang DGLehman RA JrBevevino AJGaume REPurcell RLDmitriev AE: Pedicle screw “hubbing” in the immature thoracic spine: a biomechanical and micro-computed tomography evaluation. J Pediatr Orthop 34:7037092014

12

Kim YJLenke LGBridwell KHCho YSRiew KD: Free hand pedicle screw placement in the thoracic spine: is it safe? Spine (Phila Pa 1976) 29:3333422004

13

Kim YWLenke LGKim YJBridwell KHKim YBWatanabe K: Free-hand pedicle screw placement during revision spinal surgery: analysis of 552 screws. Spine (Phila Pa 1976) 33:114111482008

14

Kretzer RMChaput CSciubba DMGaronzik IMJallo GIMcAfee PC: A computed tomography–based morphometric study of thoracic pedicle anatomy in a random United States trauma population. J Neurosurg Spine 14:2352432011

15

Lehman RA JrKang DGLenke LGGaume REPaik H: The ventral lamina and superior facet rule: a morphometric analysis for an ideal thoracic pedicle screw starting point. Spine J 14:1371442014

16

Lehman RA JrLenke LGKeeler KAKim YJCheh G: Computed tomography evaluation of pedicle screws placed in the pediatric deformed spine over an 8-year period. Spine (Phila Pa 1976) 32:267926842007

17

Lehman RA JrPolly DW JrKuklo TRCunningham BKirk KLBelmont PJ Jr: Straight-forward versus anatomic trajectory technique of thoracic pedicle screw fixation: a biomechanical analysis. Spine (Phila Pa 1976) 28:205820652003

18

Liljenqvist URAllkemper THackenberg LLink TMSteinbeck JHalm HFH: Analysis of vertebral morphology in idiopathic scoliosis with use of magnetic resonance imaging and multiplanar reconstruction. J Bone Joint Surg Am 84-A:3593682002

19

Parker SLMcGirt MJFarber SHAmin AGRick AMSuk I: Accuracy of free-hand pedicle screws in the thoracic and lumbar spine: analysis of 6816 consecutive screws. Neurosurgery 68:1701782011

20

Rampersaud YRSimon DAFoley KT: Accuracy requirements for image-guided spinal pedicle screw placement. Spine (Phila Pa 1976) 26:3523592001

21

Şarlak AYBuluç LSarisoy HTMemişoğlu KTosun B: Placement of pedicle screws in thoracic idiopathic scoliosis: a magnetic resonance imaging analysis of screw placement relative to structures at risk. Eur Spine J 17:6576622008

22

Sarwahi VSugarman EPWollowick ALAmaral TDLo YThornhill B: Prevalence, distribution, and surgical relevance of abnormal pedicles in spines with adolescent idiopathic scoliosis vs. no deformity: a CT-based study. J Bone Joint Surg Am 96:e922014

23

Tan LAYerneni KTuchman ALi XJCerpa MLehman RA Jr: Utilization of the 3D-printed spine model for freehand pedicle screw placement in complex spinal deformity correction. J Spine Surg 4:3193272018

24

Vaccaro ARRizzolo SJBalderston RAAllardyce TJGarfin SRDolinskas C: Placement of pedicle screws in the thoracic spine. Part II: An anatomical and radiographic assessment. J Bone Joint Surg Am 77:120012061995

25

Watanabe KLenke LGMatsumoto MHarimaya KKim YJHensley M: A novel pedicle channel classification describing osseous anatomy: how many thoracic scoliotic pedicles have cancellous channels? Spine (Phila Pa 1976) 35:183618422010

26

Watanabe KMatsumoto MTsuji TIshii KTakaishi HNakamura M: Ball tip technique for thoracic pedicle screw placement in patients with adolescent idiopathic scoliosis. J Neurosurg Spine 13:2462522010

27

Zindrick MRWiltse LLDoornik AWidell EHKnight GWPatwardhan AG: Analysis of the morphometric characteristics of the thoracic and lumbar pedicles. Spine (Phila Pa 1976) 12:1601661987

TrendMD

Metrics

Metrics

All Time Past Year Past 30 Days
Abstract Views 316 316 316
Full Text Views 99 99 99
PDF Downloads 63 63 63
EPUB Downloads 0 0 0

PubMed

Google Scholar