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Anterior Spinal Fusion

Planning

B

Preoperative Plan

1

Identifies level of deformity and plans levels of fusion to correct deformity on preoperative imaging

  • indications are thoracolumbar/lumbar curve which is less than 70 degrees and relatively flexible
  • if thoracic curve is structural (as determined by > 25 degrees on bending films) or has significant associated thoracic rotation on clinical exam this is a contraindication
  • prior thoracic or abdominal surgery is also a relative contraindication

2

Templates instrumentation on preoperative imaging studies

  • traditionally include Cobb angle- most commonly from T11 to L3
  • shorter fusion may be also be considered
  • if performing short fusion, first determine the apex of the curve
  • If the apex is a disc- then include 2 levels above and 2 levels below (=4 levels in fusion)
  • if the apex is a vertebral body- then include 1-2 level above and 1-2 level below (=3 or 5 levels in fusion)

3

Execute surgical walkthrough

  • describe the steps of the procedure to the attending prior to the start of the case
  • describe potential complications and steps to avoid them
C

Room Preparation

1

Surgical instrumentation

  • screws
  • rods (single or dual rod systems)
  • allograft bone for fusion

2

Room setup and equipment

  • table
  • radiolucent spine flat top table
  • neuromonitoring
  • neuromonitoring leads to upper and lower extremities for MEPs and SSEPs
  • C-arm
  • c-arm perpendicular to table

3

Patient positioning

  • foley in place
  • place the patient in the lateral decubitus position
  • position the convexity of the curve up
  • place an axillary roll
  • may also place bump under concavity of curve that can be removed at time of curve correction
  • secure the patient with a bean bag

4

Patient Prep

  • Prep should be wide from spine posteriorly to umbilicus anteriorly

Technique

D

Expose Rib

1

Mark and make the skin incision

  • in general the rib one level proximal to the most proximally instrumented vertebrae is removed (T10 rib for a T11 to L3 fusion)
  • confirm level with c-arm
  • make an incision directly over the rib: start over the rib insertion (just lateral to spine) and extend distally in line with the rib to the costochondral junction

2

Dissect through the muscle layers

  • carry the incision through the various muscle layers down to the rib periosteum
E

Rib Removal

1

Incise the rib periosteum

2

Perform subperiosteal dissection of the rib

  • perform a circumferential subperiosteal dissection of the rib
  • place a finger in the subperiosteal layer around the rib
  • then slide either a raytec sponge or retractor or Cobb in the subperiosteal layer along the length of the rib
  • pull distally
  • upward pull ruptures the costochondral junction

3

Rib Harvest

  • use a rib cutter to harvest the rib as far posteriorly as possible and remove rib

4

the posterior aspect of the rib periosteum is then incised and the chest cavity is entered

  • the posterior aspect of the rib periosteum is then incised and the chest cavity is entered
  • care is taken to avoid inadvertent damage to the lung parenchyma below
  • tag each side of the rib periosteum with heavy suture to mark for later reapproximation
F

Exposure of the Vertebra

P
P

1

Identify the retroperitoneal space

  • identify the retroperitoneal space by the retroperitoneal fat pad
  • the retroperitoneal fat pad is a critical landmark

2

Reflect the peritoneum

  • bluntly dissect the peritoneum off of the abdominal wall and the diaphragm with fingers, a lap sponge or a sponge on a stick

3

Incise the diaphragm

  • leave a 1 to 2 cm cuff of diaphragm on the thoracic wall
  • place marking stitches to allow reapproximation during closure
Pearls
  • When placing marking stitches to reapproximate diaphragm use alternating color pairs to make reapproximating easier

4

Identify the parietal pleura

  • continue to dissect the peritoneum off of the abdominal wall to visualize psoas

5

Reflect the psoas

  • use bovie electrocautery to partially elevate the psoas off at its insertion on L1 and retract posteriorly to improve visualization of the spine
Pitfalls
  • when reflecting psoas, avoid inadvertent injury to the segmental vessels which lie in the midportion of the vertebral body

6

Identify the segmental vessels

  • once the diaphragm is dissected down to the parietal pleura, incise the parietal pleura and identify the segmental vessels
  • place a chest spreader (finochietto retractor) and or Balfour retractor to allow visualization of the chest and the abdomen

7

Ligate the segmental vessels

  • elevate the segmental vessels by using a right angle hemostat, which can then be used to pass a silk suture around the vessel, alternatively ligate vessels with a harmonic scalpel
  • during this portion of the procedure MAPs should be elevated to 75 mm Hg (avoid hypotension)
  • tie the sutures to ligate the vessel

8

Cut the segmental vessels

  • cut between the silk ties and retract the segmental vessels anteriorly and posteriorly with blunt dissection
  • sharply free any soft tissue attachment to the vessels

9

Alternative technique: vessel clips are used instead of silk ties to clamp off vessels. Neuromonitoring signals are then checked after approximately 10 minutes. If there are changes then the clips are removed.

G

Disc Removal and Endplate Preparation

P

1

Identify the discs

  • complete exposure of the disc to its posterior edge and anteriorly around to the contralateral side of the spine
  • palpate the annulus on the contralateral side to confirm adequate exposure

2

Incise the annulus with a scalpel (long handle usually needed)

  • this makes the annulus easier to remove with a rongeur
  • cut with scalpel from anterior to posterior to avoid inadvertent injury to vessels if scalpel slips
  • incise the disc with a large rectangular cut; going along the edge of the endplate

3

Remove the disc

  • complete disc removal is critical for fusion
  • remove the incised annulus fibrosis and nucleus pulposis with a Lexel rongeur and/or disc shaver
  • avoid removing PLL and/or in most cases, this helps protect against neurologic injury and reduces bleeding
  • begin disk excision at the apex of the deformity
  • this allows some collapse of the spine and greater access to the proximal and distal disks

4

Remove bone down to the endplates or remove the endplates (some surgeons leave endplates in place for strength)

  • if removing endplate: separate the endplate from the vertebral body using a Cobb elevator
  • turn the elevator so that it slides down the endplate
  • remove each endplate with a rongeur after it is completely freed with a Cobb
  • remove additional endplate and disc using ring curettes, regular curettes, pituitary rongeurs or Kerrison rongeurs
Pearls
  • place gelfoam or surgicell in the disc space to minimize endplate bleeding
H

Screw Placement

P

1

Choose the implants

  • there are both single rod and double rod systems
  • if using a single rod- screw system the rod diameter should be ΒΌ inch (6.35) in diameter with large diameter screws (6.5 mm-7.5mm)
  • when placing the screws, fully visualize the endplates of the vertebra to allow for parallel placement of screws to the endplates

2

Identify position on the vertebra

  • identify the anterior and posterior margins of the vertebral body
  • when a single screw is used it is placed in the midposterior aspect of the vertebral body

3

Create tracts for screws

  • if using a staple, place the staple at the posterior edge of the vertebrae
  • the screws enter towards the posterior portion of the vertebral body to avoid creating kyphosis during compression
  • create a tract for the screw or screws through the staple with an awl or lenke probe; advance across the vertebral body to the contralateral cortex
  • when developing tract consider the amount of rotation; apex screws may need to have a trajectory that is aimed more anteriorly

4

Place the large diameter screws

  • use a ball tip probe to measure the length of the tract through the vertebral body
  • when using the 2 screw system, place the posterior screw first then the anterior screw
  • place the screws in a convergent manner to increase pullout strength
  • it is very important to place the most proximal and distal screws parallel to the endplate
  • Screw tips may be bi-cortical for additional purchase, with 4mm or less of prominence
Pearls
  • it is best to err on directing the screws slightly towards the apex of the deformity to account for screw plow
I

Rod Placement and Spine Correction

P

1

Place autograft

  • divide the harvested rib into small segments
  • place the pieces into the disc space
  • place these pieces as posterior and as lateral on the concave side as possible

2

Correct the spinal deformity

  • use rod rotation to perform the primary corrective maneuver
  • this works very well with correcting coronal plane deformities as well as maintaining sagittal plane lordosis

3

Check that the degree of correction is sufficient

  • if minimal adjustments need to be made, perform the correction with in situ bending of the rods
  • take an AP to ensure that overall correction is achieved
  • take a true lateral to ensure that the screws are not placed in the vertebral canal
Pitfalls
  • wait to perform compression for correction until after anterior structure support is placed
  • this will help to avoid losing lordosis or creating kyphosis

4

If using cages, position them for anterior structural support

  • this is usually done after rod rotation primarily because of the concern of the stiffening the intervertebral segments
  • place the anterior structural support in the levels distal to T12 to maintain lordosis, to correct the curve and increase the overall sagittal plane stiffness of the construct
  • at each segment perform distraction to seat the anterior structural support

5

Perform compression

  • perform compression to secure the anterior structural support or bone graft
  • perform the compression in sequential levels from proximal to distal

6

Place additional bone graft (autograft or allograft) to completely fill the disc space

7

Close the parietal pleura

  • perform closure by initially closing the parietal pleura over the implant with running vicryl suture
J

Wound Closure

1

Close the diaphragm

  • close the diaphragm with interrupted sutures with pop off needles

2

Place a chest tube if chest was entered, usually not needed in lumbar only fusions

  • usually a 24 french
  • tunnel over one of the more cephalad ribs

3

Close the chest

  • reapproximate the chest with the rib approximator and multiple large 1-0 vicryl sutures
  • oversew the periosteum with a 2-0 stitch
  • close the muscle layers sequentially

4

Close Fascia

  • close fascia with 0-vicryl

5

Superficial closure

  • subcutaneous with 2-0 vicryl
  • skin closure with buried 3-0 monocryl

6

Dressing

  • soft dressings over incision

Patient Care

K

Preoperative H & P

1

Obtain history and perform basic physical exam

  • evaluate for any symptoms that would be an indication for an MRI (pain that is daily or severe, night pain, radiating pain, weakness, bowel or bladder issues)
  • need to carefully document neurological status of bilateral lower extremities
  • strength, sensation, reflexes

2

Order basic imaging studies

  • PA and lateral radiographic films of the entire spine
  • bending films to evaluate curve flexibility and if thoracic curve is structural
  • MRI if indicated

3

Screen patient to identify and contraindications for surgery

  • confirms no recent infection contraindicating surgery (UTI, pneumonia)
  • prior abdominal or thoracic surgery is a relative contraindication for this technique
  • if the minor curves are structural, a more satisfactory result may be achieved with a posterior approach

4

Perform operative consent

  • describe potential complications of surgery including
  • pneumothorax or hemothorax
  • failure of fusion
  • implant failure
  • neurologic injury (from screw penetration into canal, compromised perfusion when segmentals are ligated, or during deformity correction maneuvers)
  • vascular injury
  • superficial or deep wound infection
  • injury to ureters
  • anticipated temperature asymmetry ( leg will feel warmer on the side of surgery due to dissection of sympathetic chain- often resolves in 6 to 12 months)
L

Perioperative Inpatient Management

1

Writes appropriate admission orders

  • Chest radiograph is obtained at the conclusion of the procedure on the PACU area to evaluate for any pneumothorax
  • IV fluids
  • clear liquids until bowel sounds present
  • once bowel sounds present start on soft diet and ADAT
  • POD 1 begin mobilizing with physical therapy
  • aggressive pulmonary toilet to prevent atelectasis and pneumonia
  • take an xray 1 hour after removal of the chest tube
  • pain meds
  • antibiotics
  • continue for 24-48 hours (surgeon preference)
  • wound care
  • changes dressing on POD #2 or prior to discharge (surgeon preference)
  • foley catheter out when ambulating
  • serial neurovascular exams
  • CBC in AM

2

Appropriately orders and interprets basic imaging studies

  • review postoperative radiographs and evaluates implant position

3

Discharges patient appropriately

  • pain meds
  • wound care instructions
  • schedule follow up in 2 weeks
M

Postoperative Management

P

1

Provides, modifies and adjusts procedure and patient specific post-operative management and rehabilitation

  • postop: 4 week postoperative visit
  • generally off narcotics at this point and resuming school and normal daily activities
  • postop: ~ 3 month postoperative visit
  • repeat xrays of thoracolumbar spine (PA/lat)
  • advance activities and resume sports as tolerated
Pearls
  • if single rod without anterior support or limited purchase with screws consider bracing for 3 months during activities
N

Advanced Evaluation and Management

1

Provides complex non-operative treatment

  • shared decision making
  • comprehensive informed consent

2

Recommends appropriate surgical procedures considering indications and contraindications, risks and benefits for complex cases

3

Completes comprehensive pre-operative planning with alternatives and criteria for acceptable intraoperative result for complex cases

4

Capable of surgically treating simple complications

O

Complex Patient Care

1

Completes comprehensive pre-operative planning with alternatives and criteria for acceptable intraoperative result for highly complex cases

2

Develops unique complex postoperative management plans when indicated

 

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