Surgical technique - University of Iceland · Surgical technique j 036.000.179.qxp 6.12.2004 14:03 Uhr Seite 25. Synthes Axon Surgical technique 1 Warning This description is not

Axon™. Top loading implant system forthe posterior stabilisation of the cervicaland upper thoracic spine.

Surgical technique

j

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1Synthes Axon Surgical technique

WarningThis description is not sufficient for immediate application of the instrumentation. Instruction by a surgeon experienced inhandling this instrumentation is highly recommended.

AO Principles of international fixation 4

Indications and contraindications 5

Implants 6

Instruments 8

Surgical technique 12

Additional techniques 18

Remobilising variable axis heads 19

Image intensifier control

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2 Synthes Surgical technique

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Axon™. Top loading implant system forthe posterior stabilisation of the cervicaland upper thoracic spine.

Flexible implant system

The Axon implants can accommodateindividual variations in patient anatomy.

Set screw for angularly stable locking andfixation of the rod

Simple top loading rod insertion

30° of angulation in all directions permits screw insertion according to the Magerl technique

Self-tapping screws for rapid insertion

Cancellous bone and cortex screws

30° 30°

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AO Principles of internal fixation

In 1958 the Association for the Study of Internal Fixation AO/ASIFformulated four basic principles1 which have become the guide-lines for internal fixation.

They are:– Anatomic reduction– Stable internal fixation– Preservation of blood supply– Early, active pain-free mobilisation

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

AO principles as applied to the spine3

Anatomical alignmentRestoration of normal spinal alignment to improve the bio-mechanics of the spine.

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

Preservation of blood supplyCreation of an optimal environment for fusion.

Early, pain-free mobilisationMinimisation of damage to the spinal vasculature, dura, andneural elements, which may contribute to pain reduction and im-proved function for the patient.

AO Principles of international fixation

1 Müller ME, Allgöwer M, Schneider R, Willenegger R (1991) AO Manual of Inter-nal Fixation. 3rd ed. Berlin: Springer

2 Ibid.3 Aebi M, Thalgott JS, Webb JK (1998) AO ASIF Principles in Spine Surgery. Berlin:

Springer

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Indications and contraindications

The Axon System is a comprehensive set of instruments and im-plants, including– top-loading variable axis screws,– hooks,– transverse bars and– rods.

It is designed for posterior stabilisation of the cervical spine andupper thoracic spine. The implants provide the flexibility requiredto accommodate variations in patient anatomy.

The Axon System uses the existing CerviFix® rods, allowing com-ponents from Axon and CerviFix to be interchanged. Thisallows a construct to extend from the occiput to the lower spineusing the Universal Spine System (USS).

Indications

Occipitocervical and upper cervical spine instabilities:– Rheumatoid arthritis– Congenital anomalies– Posttraumatic conditions– Tumours– Infections

Instabilities in the lower cervical and upper thoracic spine:– Posttraumatic conditions– Tumours– Iatrogenic instabilities following laminectomy etc.

Degenerative and painful posttraumatic conditions in the lowercervical and upper thoracic spine

Anterior cervical fusions requiring additional posterior stabilisa-tion

Contraindications

– Spinal destruction accompanied by a loss of ventral support(caused by tumours, fractures and infections) results inmajor instability of the cervical spine and upper thoracic spine.In this situation, stabilisation with Axon is not sufficient.Additional anterior stabilisation is crucial.

– Severe osteoporosis

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Implants

1. Axon Variable Axis Screws

1.1 Cancellous Screws– Offer up to 30° of angulation in all directions– Available as cancellous self-tapping screws with � 3.5 or

4.0 mm, coulour coded– Screws offer from 8 mm to 26 mm bone purchase

2. Axon Hooks, Titanium Alloy (TAN)

– For sublaminar insertion and stabilisation– Different offsets ease construct assembly– Easily placed and exchanged after Axon construct is in place

1.2 Cortex Screws

– Offer up to 30° of angulation in all directions– Available as cortex self-tapping screws with � 3.5 mm– Screws offer from 28 mm to 50 mm bone purchase

1.1.1 Cancellous Bone Screws Axon � 3.5 mm, Titanium Alloy (TAN)

Art. No. Length

405.508 8 mm

405.510 10 mm

405.512 12 mm

405.514 14 mm

405.516 16 mm

405.518 18 mm

405.520 20 mm

405.522 22 mm

405.524 24 mm

405.526 26 mm

1.1.2 Cancellous Bone Screws Axon � 4.0 mm, Titanium Alloy (TAN)

Art. No. Length

405.458 8 mm

405.460 10 mm

405.462 12 mm

405.464 14 mm

405.466 16 mm

405.468 18 mm

405.470 20 mm

405.472 22 mm

405.474 24 mm

405.476 26 mm

1.2.1 Cortex Screws Axon � 3.5 mm, Titanium Alloy (TAN)

Art. No. Length

404.528 28 mm

404.530 30 mm

404.532 32 mm

404.534 34 mm

404.536 36 mm

404.538 38 mm

404.540 40 mm

404.542 42 mm

404.544 44 mm

404.546 46 mm

404.548 48 mm

404.550 50 mm

Art. No.

499.406 Right, small

499.407 Left, small

499.408 Right, large

499.409 Left, large

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3. Axon Transverse Bar, open, Titanium Alloy (TAN)

– Provides a lateral offset of up to 9 mm from the 3.5 mm rodto the Axon screw

– Eliminates the need for severe rod contouring– Can be placed onto the rod from the top after the Axon

construct is in position

Art. No.

406.105 Transverse Bar

4. Lamina Clamps, Titanium Alloy (TAN), gold

– For adding a laminar substitute (cross-link)

Art. No.

498.950 CerviFix Lamina Clamp,

right

498.951 CerviFix Lamina Clamp,

left

5. Rods

5.1 Rods � 3.5 mm

– Available in lengths 80 mm and 240 mm

Art. No. Length Material

498.120 80 mm TAN

498.957 240 mm TiCP

5.2 Occiput Rod � 3.5 mm, Pure Titanium, gold

– Available length 240 mm

Art. No.

498.865 CerviFix Occiput Rod

5.3 Connecting Rods, Pure Titanium

– Available in lengths 300 mm and 500 mm

Art. No. Length

498.936 300 mm � 3.5/5.0 mm

498.937 300 mm � 3.5/6.0 mm

498.938 500 mm � 3.5/5.0 mm

498.939 500 mm � 3.5/6.0 mm

6. Parallel Connectors, Titanium Alloy (TAN)

Art. No. Length

498.935 CerviFix ParallelConnector, � 3.5/3.5 mm

498.959 Parallel Connector for USS Paediatric Rods, � 3.5/5.0 mm, light blue

498.960 CerviFix Parallel Connector, � 3.5/6.0 mm

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Instruments

Screw site preparation instruments

388.397 Awl � 3.5 mm

388.396 Quick Coupling Handle, small

388.394 Drill Bit � 2.4 mm with Stop, for Quick Coupling

388.393 Drill Sleeve with Scale, for Drill Bit � 2.4 mm

Drilling depths can be set from 6 mm to 50 mm, in 2 mm increments.

Teeth at the tip of the drill sleeve reduce risk ofslippage during drilling process.

388.070 Tap sleeve

311.349 Tap for Cancellous Bone Screw � 3.5 mm, for Quick Coupling

389.477 Tap for Cortex Screw � 3.5 mm, for Quick Coupling

389.472 Pedicle Probe � 2.0 mm

388.549 Feeler, straight, with rounded tip

389.473 Pedicle Marker, small, with short markings389.474 Pedicle Marker, small, with long markings

– Used to radiographically confirm position– Beads indicate depth in 10 mm increments– Two bead styles can be used to distinguish

left and right pedicles

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389.476 Reamer for Axon Screws

Removes excess bone around the screw site toenable rotation of Axon variable axis screw head.

388.395 Screwdriver, hexagonal, � 2.5 mm, for Quick Coupling388.391 Holding Sleeve

319.009 Depth Gauge for Screws � 3.5 to 4.0 mm, measuring range up to 50 mm

Provides direct measurement for screw selection.

Screw insertion instruments

388.868 Trial Rod � 3.5 mm388.869 Occiput Trial Rod � 3.5 mm

388.407 Holding Forceps for Rods � 3.5 mm

Forceps provide a secure insertion of the rod intothe operative site. The instrument can also be used to insert and manipulate the hooks.

388.011 CerviFix Holding Forceps for Rods � 3.5 mm

391.990 Cutting Pliers for Plates and Rods

389.478 Bending Pliers for Rods � 3.5 mm

Allows 3-dimensional contouring. Dial setting determines bend radius of rod

Rod instruments

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389.479 Alignment Tool

Used for adjusting the orientation of the variable axis screw head prior to rod placement.

388.392 Screwdriver Shaft Stardrive® 3.5, T15, self-holding,for Quick Coupling

Used with 2 Nm Torque Limiting Handle to pick upthe locking screws and tighten the construct to the appropriate torque.

389.471 Handle with Torque Limiter, 2.0 Nm, with Quick Coupling

388.349 Rod Pusher

To place the rod in the Axon screw head and to facili-tate locking screw introduction. Also providescountertorque for final tightening of the construct.

388.408 Compression Forceps

388.405 Distraction Forceps

388.504 Rod Insertion Instrument

The „Persuader“ can be used to reduce the screwonto the rod and to facilitate the locking screw intro-duction through the cannulated tube. Also providescounter torque for final tightening of the construct.

Construct assembly instruments

388.924 Bending Irons, for � 3.5 mm rods, right388.925 Bending Irons, for � 3.5 mm rods, left

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388.548 Instrument for Remobilisation of Axon Screw Heads

319.010 Depth Gauge for Screws � 2.7 to 4.0 mm, measuring range up to 60 mm

For depth measurement through the plate

312.860 Handle for Drill Guide Inserts, for Nos. 312.840,312.870 and 312.880

312.880 Drill Guide Insert 3.5, with Knurled Nut, for No. 312.860

388.017 Drill Guide Insert 2.7, calibrated, with Knurled Nut, for Nos. 312.860 and 315.630

388.020 Screwdriver, hexagonal, small, self-holding

311.440 T-Handle with Quick Coupling

315.630 Drill Bit � 2.5 mm, length 160/135 mm, 3-flute, for Quick Coupling

311.330 Tap for Cortex Screws � 3.5 mm, length 180/110 mm

Occiput Fixation Instruments

Remobilisation Instrument

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The following surgical technique is described using theexample of a C3–C5 screw insertion. For occiput fixation refer to the CerviFix Surgical Technique.

Surgical Technique

1Approach

Using the standard surgical approach, expose the spinousprocesses and laminae of the vertebrae to be fused.

2Start screw hole

Required instruments

Awl � 3.5 mm, length 179.5 mm 388.397

Determine the entry point and trajectory for the screw1.

Create a pilot hole with the awl. This helps prevent displace-ment of the drill bit during initial insertion.

3Set drill sleeve depth


Drill Sleeve with Scale, for Drill Bit � 2.4 mm (388.394) 388.393

Slide back the latch of the drill sleeve to release the inner tube.

Adjust position of inner tube in window so that the mark on theinner tube indicates the required depth.

Release the latch to lock the drill sleeve at the desired depth.

1 For correct screw placement see detailed information in:– CerviFix Surgical Technique (Art. No. 036.000.261)– Aebi M, Thalgott JS, Webb JK (1998) AO ASIF Principles in Spine Surgery.

Berlin: Springer

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4Drill hole


Drill Bit � 2.4 mm with Stop, length 171/65 mm, 2-flute, for Quick Coupling 388.394

Drill Sleeve with Scale, for Drill Bit � 2.4 mm (388.394) 388.393

Quick Coupling Handle, small 388.396

Drill to desired trajectory and depth using the drill bit and drillsleeve.

5Measure hole depth


Depth Gauge for Screws � 3.5 to 4.0 mm, measuring range up to 50 mm 319.009

Use the depth gauge to confirm hole depth and select theappropriate screw length.

Note: The Depth Gauge measures the working length, e.g. ifreading 14 mm on the depth gauge, select a 14 mm screw.

Option

Optional instruments

Pedicle Probe � 2.0 mm, length 220 mm 389.472

Feeler, straight, with rounded tip 388.549

Pedicle Marker, small, with short/long markings 389.473/474

Bone preparation may also be performed using the small probe.To confirm accurate screw placement within the bone, use thestraight feeler to palpate the screw channel walls.

The small pedicle markers may be used to radiographically con-firm position and orientation of screw sites.

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6Insert screws


Screwdriver, hexagonal, small, � 2.5 mm, length 293 mm 388.395

Holding Sleeve 388.391

Load the preassembled Axon screw from the screw rack: First engage the hexagonal screwdriver into the screw head andthen slide the holding sleeve into place.

Insert screw1. After insertion, disengage the screwdriver by firstpulling up the holding sleeve.

Option


Tap for Cancellous Bone Screw � 3.5 mm, length 185/46 mm, for Quick Coupling 311.349

Tap for Cortex Screw � 3.5 mm, length 185 mm, for Quick Coupling 389.477

Tap Sleeve 388.070

Quick Coupling Handle, small 388.396

Reamer for Axon Screws 389.476

Dense bone may be tapped using the tap for 3.5 mm cancellousbone screws or the tap for 3.5 mm cortex screws. To ease screwplacement, excess bone may be removed using the reamer.A 4.0 mm screw may be used if the primary screw has less thanoptimal fixation.

Insert remaining screws using the same technique.

1 For correct screw placement see detailed information in:– CerviFix Surgical Technique (Art. No. 036.000.261)– Aebi M, Thalgott JS, Webb JK (1998) AO ASIF Principles in Spine Surgery.

Berlin: Springer

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7Contour trial rod


Trial Rod � 3.5 mm 388.868

Contour the trial rod to fit the anatomy.

8Bend and cut rod


Bending Pliers for Rods � 3.5 mm 389.478

Cutting Pliers for Plates and Rods 391.990

Contour the rod using the bending pliers. It must match thecurve of the trial rod.

Cut the rod with the cutting pliers to the appropriate length.

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9Insert rod


Holding Forceps for Rods � 3.5 mm, length 181 mm 388.407

Alignment Tool, length 209 mm 389.479

Screwdriver Shaft Stardrive® 3.5, T15, self-holding, length 245 mm, for Quick Coupling 388.392

Handle with Torque Limiter, 2.0 Nm, with Quick Coupling 389.471

Rod Pusher 388.349

Rod Insertion Instrument 388.504

Insert the rod into the variable axis heads of the screws usingthe holding forceps. The alignment tool may be used to helporient the heads to the correct position.

Use the rod pusher/rod insertion instrument to facilitate rodplacement and locking screw insertion.

Insert and loosely fasten the Axon Locking Screws using thescrewdriver shaft with the torque limiter.


Bending Irons, right/left 388.924/388.925

The bending irons may help to adjust the curve of the rod.

Note: When disengaging the locking screwdriver, provide coun-terforce by using the rod pusher/rod insertion instrument.

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10Lock construct




Rod Pusher 388.349

Rod Insertion Instrument 388.504

Firmly tighten all locking screws using the screwdriver shaft withthe torque limiter to the preset torque of 2 Nm.

To provide countertorque, the rod pusher/rod insertion instru-ment may be used.

The construct is now rigidly locked.

11Compression/Distraction


Compression Forceps 388.408

Distraction Forceps 388.405



Loosen the locking screw of the level to be adjusted.

Use the compression forceps to achieve compression, or thedistraction forceps to achieve distraction.

After compression/distraction is achieved, tighten the lockingscrews, as described in step 10.

Repeat for each segment as required.

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Adding Transverse Bars


Screwdriver, hexagonal, small, � 2.5 mm, length 293 mm 388.395



Place the opening of the 3.5 mm Axon transverse bar over the3.5 mm rod and introduce the transverse bar into the variableaxis head of the screw.

Loosely fasten the set-screw of the transverse bar.

Insert the locking screw in the variable axis head as described insteps 9 and 10.

Tighten the set-screw of the transverse bar with the hexagonalscrewdriver.

Adding laminar substitute


Holding Forceps for Rods � 3.5 mm, length 181 mm 388.407

Screwdriver, hexagonal, small � 2.5 mm, length 293 mm 388.395

To increase rotational stability, protect the dura after laminec-tomies and to suture the musculature, add a laminar substitute(laminar clamps and rod). There are two methods:

a Preassembly of construct before insertionInsert a rod of the appropriate length in a left and a right lami-nar clamp.

Place the laminar substitute with the holding forceps on theAxon construct and lock the set-screws of the lamina clamps us-ing the hexagonal screwdriver.

b Assembly in situFirst mount the left and right laminar clamp on the Axon construct, then insert the rod into the clamps and tighten theset-screws.

Additional techniques

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Adding Transverse Bars


Instrument for Remobilisation of Axon Screws Heads 388.548



Holding Forceps for Rods � 3.5 mm 388.407

Remove the locking screws and the rod.

Push the instrument for removal over the variable axis head untilthe prongs snap over the ring at the bottom of the variable axishead.

Squeeze the handle to release the lock.

Remobilising variable axis heads

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Documents

Surgical technique - University of Iceland · Surgical technique j 036.000.179.qxp 6.12.2004 14:03 Uhr Seite 25. Synthes Axon Surgical technique 1 Warning This description is not