Open Techniques for Pedicle Screw Placem ent Know Your Anatom y - - PowerPoint PPT Presentation

Open Techniques for Pedicle Screw Placem ent Know Your Anatom y

Alexander R. Vaccaro, MD, PhD, MBA Professor, Chairman Department of Orthopaedics and Neurosurgery Thomas Jefferson University President Rothman Institute Philadelphia, PA

Rothman Institute of Orthopaedics at Thomas Jefferson University

Disclosure

 Grant Support/ Royalties/ Stock

• ptions/ Consulting/ Editorial Board:

Depuy, Nuvasive, Medronics, Stryker, Globus, Stout Medical, Aesculap, Alphatec, Paradigm Spine, Replication Medica, Spinology, Bonovo Spine, Dimension Orthotics, Gamma Spine, IT, SBI, RI related holdings, Gerson Lehrman, Guidepoint Global, Medacorp, ISD, ASIP, PST, ICOM, Orthobullets, Vertiflex, Vexim, SpineWave, Atlas Spine, Avaz Surgical, AO Spine, Spine, ESJ, JNS, PSI

 Board Member: CSRS  Editor in Chief : Clinical Spine Surgery  President: Rothman Institute

“Every pedicle screw can be worth ten million dollars…”

Rothman Institute of Orthopaedics at Thomas Jefferson University

Understand Topical

Landmarks

Understand Pedicle anatomy Understand at risk Structures Understand Different

Insertion methods

BASICS

Basic Technique for Screw Placement

• Expose start point and relevant anatomy
• Burr/rongeur outer cortex
• Cannulate tract

– drill/curette/probe/etc.

• Check for breaches with ball-tip probe
• Tap?
• Check again for breaches
• Place screw

C2 Pedicle Screw

• Where is the pedicle?

– The cranial margin of the C2 lamina is the craniocaudal landmark – A nerve hook can be inserted into the spinal canal along the cranial margin of the C2 lamina to the medial surface

• f the C2 pedicle
• Where is it going?

– Preop imaging and intraop pedicle palpation help determine medial angulation (Black Arrow) – Fluoro for cephalocaudad angulation

Vertebral Artery Course in Upper Cervical Spine

Vertebral Artery Course in Upper Cervical Spine

FIA Fenestrated

Preop Imaging

Subaxial Cervical Pedicle Screws

C7 Pedicle Screw

• Where is the pedicle?

– Slightly lateral to the center of the articular mass – Close to the inferior margin of the inferior articular process of the cranially adjacent vertebra – Use laminotomy to find pedicle – The lateral margin of the articular mass of the cervical spine can have a notch approximately at the level of the pedicle

C7 Pedicle Screw

• Use preop imaging to determine

medial angulation

• If difficulty finding pedicle, use a

funnel technique

• Where is it going?

1 2 3 4

Thoracic Pedicle Screws

• Where is the pedicle?

– Medial-Lateral – Can use Superior Facet Rule – Removal of IAP aids with identifying SAP, avoid at upper instrumented vertebra to avoid destabilization

IAP SAP

Thoracic Pedicle Screws

• Where is the pedicle?

– Cephalocaudal

Thoracic Pedicle Screws

• Where is it going?

T1 T12

Thoracic Pedicle Screws

• Where is it going?

– Anatomic (AT) versus Straightforward (SF)

SF AT AT

Thoracic Pedicle Screw

• What is in my way?

Pearls for Improved Fixation

• Undertapping

– 1mm undertapping increases POS by 93%

• OD and ratio of OD/ID

– Larger screws with larger ratios increase POS – ID affects bending strength

• Length of screw

– ~75% of max POS achieved with engagement of neurocentric junction – Max POS with ~80% of way to anterior cortex

Pearls for Improved Fixation

• Screw convergence

– 30 degrees of convergence increased pullout 28.6% in the lumbar spine

• Try not to remove/replace screw

– Insertional torque decreased 34% by removing and replacing same size screw

• Avoid hubbing

– Decrease in POS by 43% with hubbing of screw

Thoracolumbar Pedicle Screws

• Where is the pedicle?

– Transitional surface anatomy – Use a funnel technique through the base of the SAP

• Place screws in a location to

facilitate rod placement crossing the TL spine T12 L1

Lumbar Pedicle Screws

• Where is the pedicle?

– Midpoint TP – Upslope of facet versus mamillary process versus 1-3mm lateral to MLP – “Inside-out” when needed

• Palpate pedicle directly through

decompression

Lumbar Pedicle Screws

• Where is it going?

L1 L5

Lumbar Pedicle Screws

• Where is it going?

– Remember the sagittal trajectory intraoperatively!

Pedicle Sizes

T1-L4 Pedicles size height > width

• use pedicle width to size

these pedicle screws L5 Pedicle size width > height

• still large enough to

accommodate most screws

Sacral

• Where is the “pedicle”

Sacral Pedicle Screw

• Where is it going?

– Approx 35-40 deg medial

• What is in the way?

– Prominent iliac wing/PSIS

Sacral Pedicle Screw

• Bicortical versus Promontory/Tricortical

– Sacral promontory screw improved maximum insertional torque by 99% versus bicortical screw

T/L Fluoroscopic Pedicle Screw

• Initial Imaging
• Commonly 4cm from midline
• Can be longer or shorter

depending on body habitus

How to Traverse the Pedicle

Starting point

• Left pedicles start at approximately 10 to 11 o’clock at lateral border of pedicle
• Right pedicles start at approximately 2 to 3 o’clock at lateral border of pedicle
• Ensure level appropriate medial angulation and proper sagittal trajectory

Traversing the Pedicle

• After advancing the wire approximately 15mm, check AP and lateral imaging
• When the guidewire is at the medial border of the pedicle on the AP, the

guidewire should be AT or BEYOND the neurocentric junction on the lateral view

T/L Fluoroscopic Pedicle Screw

• Technique

Start Point Traversing the Pedicle Tapping Screw

Thank You