USS Variable Axis Screw (VAS) System TGsynthes.vo.llnwd.net/o16/Mobile/Synthes North... · The Synthes USS VAS variable axis components consist of noncervical spinal fixation devices

Instruments and implants approved by the AO Foundation

USS Variable Axis Screw (VAS)System. For posterior fixation of thelumbar spine.

Technique Guide

Introduction

Surgical Technique

Product Information

Table of Contents

USS Variable Axis Screw (VAS) System 2

AO Principles 4

Indications 5

Prepare Pedicles 6

Insert Screws 7

Insert Rods 8

Place Collars and Nuts 9

Apply Distraction or Compression 10

Tighten Nuts 11

Optional Techniques 14

Instruments 16

Set List 21

Synthes Spine

USS Variable Axis Screw (VAS) System

Designed to restore lordosis– Variable axis head offers ±25° of angulation for minimal rod contouring

– Precontoured rods designed to mimicspinal curvature

– Permits sagittal and lateral screw off-set and reduces the need to contourthe rod precisely

– Technique permits posterior compression

Provides stable internal fixation – Dual core screw design creates rigid fixation by engagement of cortical threads within the pedicleand cancellous threads inside the vertebral body

– Rounded, blunt screw tip design allows bicortical fixation

2 Synthes Spine USS Variable Axis Screw (VAS) System

Provides optimal environment– Variable axis head offers ±25° of angulation to provide optimal rodplacement and simplify construct assembly

Uses atraumatic technique– Preassembled head reduces operativetime and minimizes trauma to patient

– Double-lead thread increases speedof screw insertion for 5.2 mm,6.2 mm, and 7.0 mm screws

Synthes Spine 3

AO Principles

In 1958, the AO formulated four basic principles, which have become the guidelines for internal fixation.1 They are:– Anatomical reduction

– Stable internal fixation

– Preservation of blood supply

– Early, active mobilization

The fundamental aims of fracture treatment in the limbs andfusion of the spine are the same. A specific goal in the spineis returning as much function as possible to the injured neural elements.2

AO Principles as Applied to the Spine3

Anatomic alignmentRestoration of normal spinal alignment to improve the biomechanics of the spine.

Stable internal fixationStabilization of the spinal segment to promote bony fusion.

Preservation of blood supplyCreation of an optimal environment for fusion.

Early, active mobilizationMinimization of damage to the spinal vasculature, dura, andneural elements, which may contribute to pain reduction andimproved function for the patient.


1. M.E. Müller, M. Allgöwer, R. Schneider, and H. Willenegger: Manual ofInternal Fixation, 3rd Edition. Berlin; Springer-Verlag. 1991.

2. Ibid.3. M. Aebi, J.S. Thalgott, and J.K. Webb. AO ASIF Principles in Spine

Surgery. Berlin; Springer-Verlag. 1998.

Indications

The Synthes USS VAS variable axis components consist ofnon cervical spinal fixation devices intended for use as a posterior pedicle screw fixation system (T1–S2) or as an anterolateral fixation system (T8–L5). Pedicle screw fixation is limited to skeletally mature patients, with the exception ofthe Small Stature USS.

These devices are indicated as an adjunct to fusion for all ofthe following indications regardless of the intended use:– Degenerative disc disease (defined as discogenic back painwith degeneration of the disc confirmed by history and radiographic studies)

– Spondylolisthesis

– Trauma (i.e., fracture or dislocation)

– Deformities or curvatures (i.e., scoliosis, kyphosis, and/orlordosis, Scheuermann’s disease)

– Tumor

– Stenosis

– Failed previous fusion (pseudoarthrosis)

When treating patients with degenerative disc disease (DDD),transverse bars are not cleared for use as part of a posteriorpedicle screw construct.

When used with the 3.5 mm/6.0 mm parallel connectors,the USS VAS variable axis components can be linked to theCerviFix system. In addition, when used with 5.0 mm/6.0 mm parallel connectors, the Synthes Small Stature USS canbe linked to the USS VAS variable axis components.

In addition, USS VAS variable axis components can be inter-changed with all USS 6.0 mm rods and transconnectors.

Please refer to product insert (GP0001) for complete systemdescription, indications, contraindications and warnings.

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Prepare Pedicles

1Prepare pedicles

Instruments

388.532 Pedicle Reamer

388.539 Pedicle Probe, for 7.0 mm, 8.0 mm and 9.0 mm screws

or388.54 Probe

388.55 Awlor388.552 Awl, for 8.0 mm and 9.0 mm screws

Locate pedicles as described in AO ASIF Principles in SpineSurgery.4 Use the awl to open the cortex of the pedicles to adepth of 10 mm. Continue opening the pedicles using theprobe with markings at 30 mm, 40 mm, and 50 mm. Deter-mine the required lengths of the USS variable axis screws.

Note: For 8.0 mm or 9.0 mm screws, use the awl for 8.0 mmand 9.0 mm screws and the pedicle probe for 7.0 mm–9.0 mm screws.

To ensure mobility of the polyaxial screwhead, insert the tipof the pedicle reamer into the prepared pedicle. Use rotatingmovement to remove excess bone. Repeat this procedure foreach pedicle.


4. Ibid.

Insert Screws

2Insert screws

Instruments

314.132 3.0 mm Hexagonal Screwdriver with T-Handle

388.38 Holding Sleeve, for Screwdriver

388.61 Hook or Screw Holderor388.621 Handle for Hook or Screw Holder

Alternative Instruments

313.892 3.0 mm Hexagonal Screwdriver Shaft

388.652 Ratchet T-Handle, 6 mm hex coupling

Insert screws using the 3.0 mm hexagonal screwdriver withT-handle and holding sleeve or the ratchet T-handle, 3.0 mmhexagonal screwdriver shaft and holding sleeve.

Remove the selected self-tapping variable axis screw fromthe screw rack. Insert the screw into the prepared pediclesuntil the screwheads are well seated. Turn the T-handle counterclockwise one-half turn in order to ensure that thescrewhead is fully flexible. Align the side opening on thescrewhead to one side to receive the rod. Repeat for eachscrew.

Note: Before inserting the rod, make sure each of the screwheads is mobile.

To facilitate collar and nut placement, use the hook or screwholder. Insert one hook or screw holder into each screwheadand tighten in order to guide the collar and nut in Step 4.

Alternatively, use the handle for hook and screw holder toinsert the hook and screw holder.

Note: The knob on the handle can be turned to tighten orloosen the screw on the hook or screw holder, or it can bepressed down to release the hook or screw holder from thehandle.

Synthes Spine 7

Insert Rods

3Insert rods

Instruments

388.44 Rod Holding Forceps, for 6.0 mm rods

388.902 Coated Rod Template for 6.0 mm rod, 150 mm

388.961 Rod Bender, with bend radius adjustment

Determine the correct rod contour and length using thecoated rod template. The polyaxial mobility of the screwhead aids in compensation for a lateral screw offset. Select the appropriate length 6.0 mm titanium rod and, if necessary, bend the rods using the rod bender.


Insert the rods into the side-opening polyaxial screwheadsusing the rod holding forceps.

Place Collars and Nuts

4Place collars and nuts

Instrument

388.15 Socket Wrench with straight handle

Load a collar and a nut directly onto a loading post in the tray.Align the socket wrench with straight handle directly over theloading post and press down until the nut and collar are secured in the wrench. Place the loaded wrench over the hookor screw holder and onto the screwhead. Hand-tighten nuts to hold the rod, while allowing some movement for final adjustments.

Note: For constructs with more than two screws on eachside, start with the medial screwhead.

Repeat for all remaining screws. Although the rods are nowsecured in the side opening, the screwheads remain mobile.

Synthes Spine 9

Apply Distraction or Compression

5Apply distraction or compression (optional)

Instruments

388.410 Distraction Forceps, curved

388.422 Compression Forceps

Distraction or compression with variable axis screws is possible only before the nuts have been tightened.

To distract, use the distraction forceps and then tighten thenuts as described in Step 6.

To achieve compression, use the compression forceps andthen tighten the nuts as described in Step 6.


Tighten Nuts

Synthes Spine 11

6Tighten nuts

Instruments

388.13 Socket Wrench with L-Handle

388.261 10 Nm Torque Wrench

388.263 Internal Counter Torque

Alternative Instruments

388.14 Socket Wrench with straight handle

388.61 Hook or Screw Holder

Each nut can be tightened using the socket wrench with L-handle. Either the internal counter torque or the socketwrench with straight handle and a hook or screw holder canbe used for countertorque.

Tightening method using the internal counter torqueInsert the internal counter torque into the socket wrench withL-handle. Hold the internal counter torque stationary andturn the socket wrench with L-handle to secure the nut. This reduces the torque on the bone while tightening the nut.

Tighten Nuts continued

6Tighten nuts continued

Tightening method using socket wrench with straighthandle for countertorquePlace the socket wrench with L-handle over the hook or screwholder and insert the socket wrench with straight handle.Hold the socket wrench with straight handle stationary andturn the socket wrench with L-handle to secure the nut. This reduces the torque on the bone while tightening the nut.

Note: Any distraction or compression maneuvers must be completed before tightening.


Synthes Spine 13

The 10 Nm torque wrench must be used for the finalconstruct tighteningBefore final tightening, check that the rod is properly positioned in the USS VAS screw. Place the 10 Nm torquewrench over the nut. Insert the internal counter torque intothe 10 Nm torque wrench. Hold the internal counter torquestationary while turning the 10 Nm torque wrench. Thewrench will “click” at the preset torque of 10 Nm.

Optional Techniques

Adding transconnectors

Instruments

388.31 Long Small Hexagonal Screwdriver

388.865 Measuring Template, for Low ProfileTransconnectors

The low profile transconnector is designed to be used as aconstruct stabilizer to reduce rotation.

Use the measuring template for low profile transconnectorsto measure the distance between the two rods.

Choose a transconnector of the appropriate length. With thetransconnector setscrews loosened, apply it to the rods. Usethe long small hexagonal screwdriver to secure the trans con -nector to the rods by tightening the setscrews on each end.

Note: For transconnectors with stargrind, tighten the stargrind setscrew to lock the angle between the rods.

When using an adjustable length transconnector, adjust thedistance between the rods, if desired, by compressing or distracting; then tighten the center setscrew on the rotatingshaft using the long small hexagonal screwdriver.

Note: If any part of the construct requires further adjust-ment, all transconnector setscrews must be loosened. Afterfinal adjustment, retighten the setscrews.


Remobilization

Instrument

388.357 Locking Ring Extractor

Remove the nut, collar, and rod from the construct. Prior toremobilization using the locking ring extractor, loosen thepusher by turning the T-handle counterclockwise to themarked thread and move the tube back.

Slide the slotted part of the extractor over the cam of thescrewhead’s locking ring and push the tube down.

Slowly turn the T-handle clockwise until resistance is encountered.

Continue turning until the screwhead is remobilized.

Caution: Further turning of the T-handle will cause removalof the locking ring from the construct. If the locking ring isremoved, the variable axis screw must be removed and replaced.

Synthes Spine 15

Instruments

Taps for Dual Core Screws311.602 5.2 mm311.603 6.2 mm311.604 7.0 mm311.605 8.0 mm311.606 9.0 mm

Cannulated Taps for Dual Core Screws311.612 5.2 mm 311.613 6.2 mm311.614 7.0 mm311.615 8.0 mm311.616 9.0 mm

388.274 Universal Spinal System Tap Handle

Taps for dual core screws penetrate the pedicle prior to screw insertion. They preparea pathway with the same pitch as the screwand smaller cancellous core diameter.

388.532 Pedicle Reamer

Removes excess bone around the pedicle toenable rotation of USS Variable Axis ScrewHead.

388.539 Pedicle Probe, for 7.0 mm, 8.0 mm and9.0 mm screws

Used to open the pedicle canal and determinethe proper screw length.

388.54 Probe

388.545 Straight Ball Tip Probe

Used to palpate the walls of the pedicle andto determine proper screw length using thedepth markings at 25 mm, 30 mm, 40 mm,50 mm, 60 mm, and 70 mm.


For pedicle preparation

388.546 Curved Ball Tip Probe

388.55 Awl

Used to perforate the posterior cortex of the pedicle.

388.552 Awl, for 8.0 mm and 9.0 mm screws

313.892 3.0 mm Hexagonal Screwdriver Shaft

314.132 3.0 mm Hexagonal Screwdriver with T-Handle

388.38 Holding Sleeve, for Screwdriver, for side-opening implants

388.652 Ratchet T-Handle, 6 mm hex coupling

Synthes Spine 17

For screw insertion

Instruments continued

388.44 Rod Holding Forceps, for 6.0 mm rods

Used to place the rod into the Variable AxisScrew. Ratchet-locking mechanism ensures aconsistent and stable grip on the 6.0 mm rod.Quick release permits one-handed applicationfor easy maneuvering and rod placement.

388.902 Coated Rod Template for 6.0 mm rods,150 mm

Used to determine the length and contour of the rod.

388.94 Rod Pusher, for 6.0 mm rods

Assists rod placement into the side-openingimplants.

388.961 Rod Bender, with bend radius adjustment

Used to contour the rod. Knob is used to adjust the bend radius.

388.13 Socket Wrench with L-Handle, 11 mm widthacross flats

Used to tighten the nut once it has beenloaded onto the implant.

388.14 Socket Wrench with straight handle, 6 mmwidth across flats

Used with Hook or Screw Holder (388.61) forcountertorque during tightening.


For rod preparation and insertion

For construct assembly

388.261 10 Nm Torque Wrench, 11 mm width across flats

Important: For final tightening of the construct, this wrench must be used to apply the proper amount of torque.

388.262 Counter Torque Sleeve

This instrument is used in conjunction withthe Hook or Screw Holder to reduce torqueon the bone while tightening the nut.

388.263 Internal Counter Torque

Used with the 11 mm Hex Socket Wrench to reduce the torque on the bone while tightening the nut.

388.31 Long Small Hexagonal Screwdriver

Used to secure transconnector to the rods.

388.61 Hook or Screw Holder

Synthes Spine 19

388.15 Socket Wrench with straight handle, 11 mmwidth across flats

Used to load the collar and nut directly ontothe implant and secure them to the rod. Theinstrument retains both the collar and nut forease of construct assembly.

Instruments continued

388.410 Distraction Forceps, curved

388.422 Compression Forceps

388.357 Locking Ring Extractor, for USS Variable AxisScrews


For distraction and compression

For extraction

388.621 Handle for Hook or Screw Holder

Facilitates positioning of the USS VAS collar and nut, acting as an extension to the implants.

388.865 Measuring Template, for Low ProfileTransconnectors

Universal Spinal System Variable Axis Screw Instrument Set (145.252)

Synthes Spine 21

Graphic Case690.034 USS Variable Axis Screw Instrument Set

Graphic Case

InstrumentsTaps for Dual Core Screws311.602 5.2 mm311.603 6.2 mm311.604 7.0 mm311.605 8.0 mm311.606 9.0 mm

Cannulated Taps for Dual Core Screws311.612 5.2 mm311.613 6.2 mm311.614 7.0 mm311.615 8.0 mm311.616 9.0 mm

313.892 3.0 mm Hexagonal Screwdriver Shaft314.132 3.0 mm Hexagonal Screwdriver with

T-Handle, 2 ea.388.13 Socket Wrench with L-Handle, 11 mm width

across flats388.14 Socket Wrench with straight handle, 6 mm

width across flats388.15 Socket Wrench with straight handle, 11 mm

width across flats, 2 ea.388.261 10 Nm Torque Wrench, 11 mm width

across flats388.262 Counter Torque Sleeve388.263 Internal Counter Torque 388.274 Universal Spinal System Tap Handle388.31 Long Small Hexagonal Screwdriver388.357 Locking Ring Extractor, for USS Variable

Axis Screw388.38 Holding Sleeve, for Screwdriver, for

side-opening implants, 2 ea.388.410 Distraction Forceps, curved388.422 Compression Forceps 388.44 Rod Holding Forceps, for 6.0 mm Rods, 2 ea.388.532 Pedicle Reamer388.539 Pedicle Probe, for 7.0 mm, 8.0 mm and

9.0 mm screws388.54 Probe388.545 Straight Ball Tip Probe388.546 Curved Ball Tip Probe

388.55 Awl388.552 Awl, for 8.0 mm and 9.0 mm screws388.61 Hook or Screw Holder, 8 ea.388.621 Handle for Hook or Screw Holder, 2 ea.388.652 Ratchet T-Handle, 6 mm hex coupling388.865 Measuring Template, for Low Profile

Transconnectors388.902 Coated Rod Template for 6.0 mm rods388.94 Rod Pusher, for 6.0 mm rods388.961 Rod Bender, with bend radius adjustment

Titanium Universal Spinal System Variable Axis Screw Implant Set (145.251)


7.0 mm Titanium USS Variable Axis Screws*499.351 30 mm thread, 2 ea. 499.352 35 mm thread, 6 ea.499.353 40 mm thread, 8 ea. 499.354 45 mm thread, 8 ea. 499.355 50 mm thread, 6 ea. 499.356 55 mm thread, 2 ea. 499.357 60 mm thread, 2 ea. 499.358 65 mm thread, 2 ea.

8.0 mm Titanium USS Variable Axis Screws499.361 30 mm thread, 2 ea. 499.362 35 mm thread, 6 ea. 499.363 40 mm thread, 8 ea. 499.364 45 mm thread, 8 ea. 499.365 50 mm thread, 6 ea. 499.366 55 mm thread, 2 ea. 499.367 60 mm thread, 2 ea. 499.368 65 mm thread, 2 ea.

Graphic Case690.064 Titanium USS Variable Axis Screw Implant Set

Graphic CaseImplants497.140 Titanium Collar, for USS Variable Axis Screws,

16 ea.498.003 Titanium Nut, 11 mm across flats, 16 ea.

Titanium Low Profile Transconnectors497.796 31.5 mm–34 mm, 2 ea.497.797 35 mm–41 mm, 2 ea.497.798 42 mm–55 mm, 2 ea.497.799 56 mm–83 mm, 2 ea.

6.0 mm Titanium Curved Rod498.139 45 mm, 2 ea.498.140 55 mm, 2 ea.498.141 65 mm, 4 ea.498.142 75 mm, 4 ea.498.143 85 mm, 4 ea.

6.0 mm Titanium Soft Rod498.150 50 mm, 4 ea.498.151 75 mm, 4 ea.498.152 100 mm, 4 ea.498.153 125 mm, 4 ea.498.154 150 mm, 4 ea.

5.2 mm Titanium USS Variable Axis Screws*499.331 30 mm thread, 2 ea. 499.332 35 mm thread, 6 ea.499.333 40 mm thread, 6 ea.499.334 45 mm thread, 4 ea.499.335 50 mm thread, 2 ea.499.336 55 mm thread, 2 ea.

6.2 mm Titanium USS Variable Axis Screws*499.341 30 mm thread, 2 ea.499.342 35 mm thread, 6 ea.499.343 40 mm thread, 8 ea. 499.344 45 mm thread, 8 ea.499.345 50 mm thread, 6 ea. 499.346 55 mm thread, 2 ea.499.347 60 mm thread, 2 ea.499.348 65 mm thread, 2 ea.

*Double lead thread

Synthes Spine 23

Also Available

Implants

4.2 mm Titanium USS Variable Axis Screws*

499.640 25 mm thread499.641 30 mm thread499.642 35 mm thread499.643 40 mm thread

5.2 mm Titanium, USS Variable Axis Screw*

499.644 25 mm thread

6.2 mm Titanium USS Variable Axis Screw*

499.645 25 mm thread

7.0 mm Titanium USS Variable Axis Screws*

499.650 25 mm thread499.651 70 mm thread499.652 75 mm thread499.653 80 mm thread499.654 90 mm thread499.655 100 mm thread

8.0 mm Titanium USS Variable Axis Screws

499.660 25 mm thread499.661 70 mm thread499.662 75 mm thread499.663 80 mm thread499.664 90 mm thread499.665 100 mm thread

9.0 mm Titanium USS Variable Axis Screws

499.371 30 mm thread499.372 35 mm thread499.373 40 mm thread499.374 45 mm thread499.375 50 mm thread499.376 55 mm thread499.377 60 mm thread499.378 65 mm thread499.670 70 mm thread499.671 75 mm thread499.672 80 mm thread499.673 90 mm thread499.674 100 mm thread

*Double lead thread

Synthes Spine1302 Wrights Lane EastWest Chester, PA 19380Telephone: (610) 719-5000To order: (800) 523-0322Fax: (610) 251-9056

Synthes (Canada) Ltd.2566 Meadowpine BoulevardMississauga, Ontario L5N 6P9Telephone: (905) 567-0440To order: (800) 668-1119Fax: (905) 567-3185

© 2002 Synthes, Inc. or its affiliates. All rights reserved. CerviFix and Synthes are trademarks of Synthes, Inc. or its affiliates. Printed in U.S.A. 1/10 J3911-F

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Documents

USS Variable Axis Screw (VAS) System TGsynthes.vo.llnwd.net/o16/Mobile/Synthes North... · The Synthes USS VAS variable axis components consist of noncervical spinal fixation devices