PSF to pelvis for Neuromuscular Scoliosis

Authors:

Planning

B

Preoperative Plan

1

Identifies components of spinal deformity on preoperative imaging

  • curve type and magnitude
  • pelvic obliquity
  • shoulder balance
  • curve flexibility
  • sagittal alignment

2

Template instrumentation and fusion levels on preoperative imaging studies

  • Determines upper and lower instrumented vertebra
  • Understands indications for including pelvis 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

P
P

1

Surgical instrumentation

  • pedicle screws, hooks and wires/cables
  • rods
  • allograft bone for fusion

2

Room setup and equipment

  • table
  • radiolucent Jackson spine flat top table
  • neuromonitoring
  • neuromonitoring leads to upper and lower extremities for SSEPs and MEPs
  • C-arm
  • c-arm perpendicular to table
  • Blood products available- typically 2 units PRBCs typed and crossed
  • consider use of TXA
  • consider use of cell saver

3

Patient positioning

  • prone with arms at 90° max shoulder abduction and elbow flexion to prevent axillary nerve injury
  • foam padding on chest at nipple level
  • pads over ASIS and padding (gel, foam or pillows) on knees
  • hips and knees flexed (may flex hips more in cases of severe lordosis)
  • foley in place
Pearls
  • Halofemoral traction may be helpful to passively correct curve and pelvic obliquity
  • When significant weight is being used for traction, blood pressure should be elevated
Pitfalls
  • the more the hips are flexed, the more hyperlordosis of the lumbar spine will be passively corrected
  • however, be careful not to flex hips so much that the pelvis cannot be imaged because the thighs limit position of C-arm

Technique

D

Posterior Approach

1

Identify upper instrumented vertebrae (UIV) with c-arm fluoroscopy

2

Make skin incision

  • make a midline incision starting from upper instrumented vertebrae all the way down to the sacrum
  • make the incision through the dermal layer only

3

Dissect subcutaneous tissue down to fascia

  • deepen the incision to the level of the spinous processes

4

Place retractors

  • use weitlaner retractors to retract the skin margins
  • identify the interspinous ligament between the spinous process
  • this has the appearance of a white line
  • as the incision is deepened, keep the retractors (weitlaner, cerebellar) tight to help with the exposure and to minimize the amount of bleeding

5

Preserve interspinous ligament at and above the level of the upper instrumented vertebrae (UIV)

6

Open the cartilaginous caps over the spinous processes at all levels below the UIV

  • incise the cartilaginous caps overlying the spinous processes and expose the spinous process staying in the subperiosteal plane
E

Deep Dissection

1

Perform subperiosteal dissection

  • perform dissection with Cobb and bovie electrocautery laterally out to the level of the transverse process

2

Reposition retractors as needed

  • while exposing, move the weitlaner retractors to a deeper position for retraction and hemostasis
  • it is easier to dissect from caudad to cephalad because of the oblique attachments of the short rotator muscles and ligaments of the spine
  • generally the primary surgeon works from caudad to cephalad while the assistant works from cephalad to caudad so that they can dissect simultaneously

3

Maintain hemostasis

  • coagulate the branch of the segmental vessel just lateral to each facet

4

Expose the sacrum

  • if placing SAI screws expose laterally to identify S1 and S2 foramen

5

If placing iliac screws or Galveston rods: expose the iliac wings

  • using the same skin incision, identify and incise the fascia just lateral to the posterior superior iliac spine (PSIS) on each side
  • subperiosteally dissect the lateral iliac wing down to the sciatic notch
  • use Taylor or Sofield retractors to facilitate the exposure
  • expose the bone of the PSIS by using a rongeur to remove the fibrocartilaginous tissue at the PSIS

6

Confirm that all desired levels are exposed

  • Confirm levels with C-arm
  • the T12 rib can also be used to aid in localizing the levels
F

1. Pelvic fixation with Sacral Alar Iliac (SAI) Screws 2. Pelvic fixation with Iliac Screws or 3. Galveston Rod Preparation

P

1

1. Pelvic fixation with Sacral Alar Iliac screws

  • make a burr hole at starting point
  • starting point between the S1 and S2 foramen, in line with S1 pedicle screw starting point
  • Insert pedicle probe/awl and advance until resistance from sacroiliac joint is in encountered
  • angle towards greater trochanter, approximately 40° laterally and 40° caudally, though this varies with pelvic obliquity/deformity
  • Use c-arm fluoroscopy to confirm that tract is just above the level of the sciatic notch
  • use orthogonal imaging perpendicular to the tract of the probe and parallel to the probe, i.e. teardrop view
  • Advance probe towards anterior inferior iliac spine
  • aim for just above the hip joint, but take care not to enter the hip joint
  • confirm position of probe with c-arm fluoroscopy in both orthogonal imaging perpendicular to the tract of the probe and parallel to the probe, i.e. teardrop view
  • remove pedicle probe/awl and probe tract with ball tip to confirm osseous channel and measure tract
  • length is generally 70-100 mm
  • for adults a minimum diameter of 8.5mm is typical and this may be appropriate for older teenagers, for younger children a smaller diameter may be necessary
  • place screw and confirm position with AP and teardrop fluoroscopic images
Pearls
  • if orientation of pelvis/imaging is unclear, one can dissect along outer table
  • then, place finger in depression of sciatic notch to confirm direction of tract

2

2. Pelvic fixation with Iliac screws

  • make a separate fascial incision over the PSIS. an alternative method is to dissect from midline and enter the medial wall of the iliac crest
  • expose the outer table to visualize trajectory (from PSIS to sciatic notch)
  • use a rongeur just lateral to the PSIS to expose cancellous bone
  • use a lenke probe/awl to create a tract between the inner and outer wall of the iliac wing aiming toward the anterior inferior iliac spine (AIIS) taking care to avoid the sciatic notch
  • probe tract with ball trip probe to confirm osseous channel and measure length of tract
  • place screw in tract and confirm position with c arm fluoroscopy

3

3. Galveston Rod preparation

  • create channel from the PSIS to the lateral ilium by using progressively larger probes
  • this channel should pass just superior to the sciatic notch
  • Insert trial rod
  • once the channel is made, insert a rod (5.5 mm in smaller children) to a depth of 6-7 cm
  • Remove the trial rod
  • Verify bony walls intact and measure depth of channel
  • probe the channel to ensure that the bony walls are intact and measure the depth of the channel for later Galveston Rod Placement
  • Obtain hemostasis
  • use bone wax to plug the hole at the PSIS to prevent blood from oozing before final rod placement
G

Placement of wires, hooks or pedicle screws

P

1

Remove the facets

  • remove the facets with a rongeur, osteotome, burr or bone scalpel
  • start at the L5-S1 articulation and proceed cephalad to the level below the planned upper instrumented vertebrae
  • remove a window of ligamentum flavum at each interspinous region if planning wire passage
  • use gelfoam soaked in thrombin when needed to control local bleeding
  • if needed for additional deformity correction a ponte osteotomy can be performed by removing the facet in its entirety with a combination of a Kerrison rongeur and burr

2

Pedicle screws

  • Identify the pedicle starting point and use a high speed cortical burr to mark starting point and penetrate cortical surface
  • Insert lenke pedicle probe into the pedicle with the tip pointing laterally at the identified starting point and advance to 20mm or alternatively a 2.0 mm drill bit can be used
  • Probe the tract using a flexible sounding probe (ball tip probe) to palpate the superior, inferior, medial and lateral walls and the endpoint (floor)
  • If no breeches are appreciated face Lenke probe medially and advance to anterior cortex or alternatively a 3.2 mm drill bit can be used
  • Probe the tract using a flexible sounding probe (ball tip probe) to palpate the superior, inferior, medial and lateral walls and the endpoint (floor)
  • Measure the depth of the tract
  • Place the pedicle screw slowly in the orientation of the tract that was created
  • Stimulate screws: if less than 6-8mA reevaluate screw position
  • Confirm position of screws with AP and lateral C-arm fluoroscopy
  • For additional details on pedicle screw placement see technique for idiopathic scoliosis

3

Placement of sublaminar wires

  • contour 16 gauge double wires to allow sublaminar passage
  • wire should be bent with a radius of curvature that approximates the width of the lamina
  • roll wires under lamina
  • keep gentle pressure anteriorly to make sure you are not to deep and inadvertently damaging the cord
  • conversely do not push so hard on the undersurface of the lamina that the tip is caught and the wire is levered into the spinal cord
  • pull tip through until ends are of similar lengths, then can cut to separate the double wire
  • separate the wires placing one wire on each side of the spine
Pitfalls
  • it is important to roll rather than push when placing sublaminar wires

4

Placement of Hooks

5

Confirm position of anchors with C-arm fluoroscopy images (not needed for wires or hooks in most cases)

H

Rod contouring

P
P

1

Measure length of rods with rod template

  • add 5-10cm depending upon size and flexibility of the curve
  • cut to appropriate length

2

Contour rods with french or plate benders

Pearls
  • If using SAI screws, the rod will need a sharp bend at lumbosacral junction (around 70 degrees)

3

If placing Galveston Rods:

  • Place hand benders
  • use hand benders to bend the rod at 90 degrees at the marked location
  • place the short end of the rod in the slot at the end of the Galveston Rod benders
  • have an assistant hold the long end of the rod parallel to the operating room table top
  • Place the rod plate benders
  • this should be held vertical to this plane
  • place a rod bender on the short end of the rod to bend the end 90 degrees to a position perpendicular to the operating room table
  • Bend the rods
  • bend the lordosis into the lower rod
  • bend the kyphosis into the upper rod for appropriate sagittal plane alignment
  • bend the second rod so that it mirrors the shape of the first rod
  • Place rod
  • insert the rod on either side of the scoliosis
  • Spread the sublaminar wire apart usually with the distal wire limb passing laterally
  • place a surgical towel over the wires of the second side to prevent confusion
  • Insert the Galveston rod
  • after the wires have been spread insert the initial Galveston rod into the iliac wing and tamp into place at the PSIS
  • Prepare the rods for insertion add the depth of the iliac crest channel and the offset distance from the PSIS to the midpoint of the L5 lamina make a mark at the distance from the end of the straight rod
Pitfalls
  • After placement examine the lateral iliac wing to ensure that the rod didn't penetrate laterally during insertion
I

Rod placement and correction maneuvers

P
P

1

Reduction technique depends on deformity

Pitfalls
  • It is better to use a softer/more flexible rod or do additional contouring for less correction than to pull out anchors
  • After rod is seated additional bending with in situ or L-benders can be performed to optimize correction

2

Attach rods to pelvic anchors and up to the apex of the deformity

  • If using SAI screws can align rods with SAI screws and pedicle screws directly
  • If using iliac screws then will need a connector to attach to rods
  • can consider connecting the concave and convex rods via a connector for added rigidity

3

Use rod holders to push rods over spine

4

Then secure to proximal anchors

  • Can use serial reducers for this step
Pearls
  • especially with weak bone, use serial reducers to load share on multiple fixation points

5

Perform additional compression and distraction as needed

6

Evaluate correction in sagittal and coronal plane

  • The T square of Tolo can be very helpful in intraoperatively assessing that pelvic obliquity is improved and sitting balance has been achieved

7

Torque set screws to maintain correction once optimized

8

If using sublaminar wires:

  • Tighten the wires
  • tighten the sublaminar wires starting at L5
  • sequentially tighten the wires on the side to L1 or L2
  • place downward pressure with rod pusher on the rod as a counterforce to the wire tightening to minimize the chance of wire pull through
  • Contour rods
  • contour the upper end of the rod in the kyphotic position to minimize the risk of pullout of the upper Implants
  • hold manually in place with a rod pusher while the 2 most cephalad sublaminar wires are tightened
  • Tighten remaining wires on convex side
  • Insert the concave side rod into the upper spinal implants
  • Hold the rod into place while the upper two sublaminar wires on the side are tightened
  • tighten the remaining sublaminar wires on the concave side
  • Cut the wire
  • once all the have been tightened cut the twisted wire at a level that leaves them about 1 to 1.5 cm in length
  • consider placement of one additional cross link to stabilize the upper end of the instrumentation at the midthoracic level
  • bend the wire ends and tamp down to prevent dorsal protrusion
Pearls
  • Sublaminar wires or bands can also be used to supplement screws especially with weak bone to avoid screw pullout
  • The wires or bands can be used to do provisional reduction and then rod can be seated in screws

9

Perform decortication

  • decorticate the exposed bony areas through the region of intended fusion with rongeurs and a power burr
J

Wound Closure

P

1

Irrigation and Hemostasis

  • irrigate spine with saline (author's preference is to use a 3L bag of irrigation with castile soap)

2

Place autograft +/- allograft

  • author's preference is to add vancomycin powder- mixing half of it with the bone graft and sprinkling half of it above the fascia once closed
  • place hemovac drain under fascia if there is enough bleeding/multiple osteotomies to raise concern for hematoma formation

3

Close Muscle

  • close muscle layer with 1- vicryl

4

Close Fascia

  • close fascia with 1-vicryl
  • need water tight closure and need to decrease dead space for hematoma

5

Superficial closure

  • subcutaneous with 2-0 vicryl
  • skin closure with buried 3-0 monocryl
  • can also reinforce with surgical glue
Pitfalls
  • many of these children have conditions associated with slow or poor wound healing
  • if risk of dehiscence is high, consider reinforcing with use of additional nonabsorbable suture (3-0 nylon)

6

Dressing

  • soft dressing over incision
  • Author's preference is to use waterproof layer at base to prevent soiling reaching the incision in patients who are developmentally delayed or have impaired sensation/inability to communicate when they have soiled the dressing

Patient Care

K

Preoperative H & P

1

Obtain history and perform basic physical exam

  • need to carefully document neurological status of bilateral lower extremities
  • strength, sensation, reflexes, and primary symptoms

2

Order basic imaging studies

  • PA and lateral radiographic films of the entire spine

3

Screen medical studies to identify and contraindications for surgery

  • confirms no recent infection contraindicating surgery (UTI)
  • consider cardiology evaluation
  • consider pulmonology evaluation
  • consider nutritional evaluation

4

Perform operative consent

  • describe complications of surgery including
  • pseudarthrosis
  • implant misplacement, migration or failure
  • neurologic injury: loss of motor, sensation or bowel/bladder function
  • superficial or deep wound infection
  • dural tear
  • need for reoperation
L

Perioperative Inpatient Management

1

Writes appropriate admission orders

  • IV fluids
  • advance diet when return of flatus
  • pain meds
  • antibiotics
  • continue for 24-48 hours
  • wound care
  • changes dressing when soiled or based on attending preference
  • foley catheter out POD #1 in most cases

2

Inpatient physical therapy

  • start sitting 1-2 days postoperatively
  • increase the periods of siting each day
  • sitting is allowed as much as possible
  • serial neurovascular exams
  • check appropriate labs

3

Appropriately orders and interprets basic imaging studies

  • review postoperative radiographs and identifies mal-positioned pedicle screws, loss of fixation and overall correction

4

Appropriate medical management and medical consultation

5

Discharges patient appropriately

  • pain meds
  • wound care
  • schedule follow up in 1-2 weeks
M

Intermediate Evaluation and Management

1

Obtain focused history and performs focused exam

  • interpret neurological exam

2

Appropriately orders and interprets advanced imaging studies

  • MRI for very atypical curves or if there are other concerns

3

Makes informed decision to proceed with operative treatment

  • describes accepted indications and contraindications for surgical intervention

4

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

  • postop: 1-2 week postoperative visit
  • wound check
  • diagnose and management of early complications
  • check spinal radiographs in 3 months, 6 months and annually postoperatively to look for evidence of any implant complications
  • postop: ~ 3 month postoperative visit
  • repeat xrays of entire spine (PA/lateral sitting)
  • advance spine restrictions and activity levels
  • diagnosis and management of late complications
N

Advanced Evaluation and Management

1

Provides complex non-operative treatment

2

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

3

Capable of surgically treating some complications

  • drainage of hematoma
  • debridement of infection
  • has at least 2 units of blood typed and crossed for I and D or hardware removal
 

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