Authors of section

Author

Emiliano Vialle

General Editor

Luiz Vialle

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Posterior instrumentation with release

1. Introduction

Preoperative planning

  • Review patient's clinical data and blood exams.
  • Estimate the surgical blood loss and determine the need for blood transfusion or the use of cell saver.
  • Estimate the correction to be around 40-50° or 50% of the curve in deformities above 90°
  • Check X-rays for possible pedicle abnormalities and draw the surgical strategy on a template

Selection of upper instrumented level

There are currently two commonly used options for the upper instrumented level.

  • End vertebra of the deformity
  • The first lordotic vertebra cranial to the deformity

Using the first lordotic vertebra will reduce the risk of getting junctional kyphosis. However, insertion of pedicle screws at the cervico thoracic junction is technically demanding.

posterior instrumentation without release

In the case illustrated the end vertebra of the kyphosis is T3, while the optimal fixation point is at T1, the first lordotic vertebra cranial to the deformity.

posterior instrumentation without release

Selection of lower instrumented level

The distal point of fixation has traditionally been the vertebra below the first lordotic disc in the lumbar area, usually L1 or L2

posterior instrumentation without release

Another option is to use the most proximal vertebra touched by a line drawn vertically from the posterior superior corner of the sacrum on the lateral radiographs.

posterior instrumentation without release

Release

Curves more than 90° or smaller curves which do not correct more than 50% in hyperextension films will require a release. This may be an anterior release, a posterior osteotomy, or a combination of both.

Most cases can be managed with a posterior osteotomy and pedicle screw instrumentation. The main indications for anterior release is advanced disk degeneration and anterior osteophytes.

posterior instrumentation without release

2. Approach and positioning

The endoscopically assisted anterior release is performed through standard portals of the anterior thoracoscopic approach or video assisted mini open approach.

The anterior release is performed with the patient in lateral decubitus. Upon completion of the anterior release, the patient is positioned prone.

posterior instrumentation with release

The posterior instrumentation is performed through the standard posterior approach.

posterior instrumentation with release

3. Anterior release

The anterior release consists of a thorough discectomy resection of annulus of the apical intervertebral discs and release of the anterior longitudinal ligament within the proposed instrumented area of the spine.

Generally a minimum of 5 apical intervertebral discs are excised.

posterior instrumentation with release

Annulus removal

The annulus is incised from the lateral aspect of the spine with a scalpel. The disc is removed using curettes and rongeurs.

Removal of the posterior annulus is optional.

The ALL (anterior longitudinal ligament) is usually thickened at this region and cutting it increase the release and posterior correction of the deformity.

posterior instrumentation with release

End plate excision

The cartilaginous end plate is excised using a curette, a periosteal elevator or a chisel in order to reduce the risk of pseudoarthrosis.

posterior instrumentation with release

Grafting

Morselized rib graft supplemented with bone substitutes or iliac crest bone graft is placed in the interbody space.

posterior instrumentation with release

4. Pedicle screw insertion

Bilateral pedicle screws are inserted at the three cranial and caudal vertebrae. This is performed prior to any posterior osteotomies to reduce the risk of accidental injury to the spinal cord during screw insertion.

On the remaining vertebrae, unilateral pedicle screws may be used switching sides at each level.

Alternatively, either laminar or transverse hooks can be inserted at the upper end of the construct.

At the most caudal levels reduction screws may be inserted to facilitate rod insertion and deformity correction.

 
posterior instrumentation without release

5. Posterior release (posterior column osteotomy)

PCO in the thoracic spine is called Ponte osteotomy.

The inferior aspect of the spinous process is removed followed by the removal of the inter spinous ligament utilizing a standard rongeur.

posterior instrumentation with release

The ligamentum flavum is removed with a Kerrison rongeur, It is important not to penetrate deeply against the dura or tear the dura.

Removal of ligamentum flavum

Then bilateral facet joints are removed either with a Kerrison rongeur or a high speed burr.

Care should be taken not to tear the dura or the nerve roots so as not to compromise the neurological function.

posterior instrumentation with release

6. Reduction of the deformity

The rod curvature should approximate the planned correction (to achieve 40-50° of kyphosis).

Overcorrection will increase the risk of decompensation either proximal or caudal.

posterior instrumentation with release

After rod insertion is completed, gradual compression between the screws towards the apex of the deformity will provide further correction.

The goal of compression is to close the osteotomy sites and to reduce the posterior length of the spine.

posterior instrumentation with release

7. Spinal fusion

The laminae and the transverse processes are decorticated with an osteotome.

Care should be taken to always point the osteotome away from the spinal canal.

Alternatively, the decortication may be performed with a powered burr.

posterior instrumentation with release

Bone graft (allograft, autograft, or bone substitutes) is copiously placed over the entire decorticated area.

Optional: Vancomicin powder (1gram) is distributed over the surgically exposed area.

posterior instrumentation without release

Transverse connectors may be inserted one at each end of the construct at the surgeons discretion.

posterior instrumentation without release

8. Intraoperative imaging

Prior to wound closure intraoperative imaging should check:

  • Fusion levels
  • Screw position
  • Overall coronal and sagittal correction and alignment

9. Aftercare following correction of spinal deformity

Immediate postoperative medication

Intravenous antibiotics are administrated for at least 24 hours, depending on hospital protocol. The use of an epidural pain catheter vs. intravenous patient controlled analgesia (PCA) are utilized for acute pain management.

Mobilization

Early mobilization out of bed, is preferably started the day after surgery. Generally a postoperative brace/orthosis is not required.

Postoperative imaging

It is appropriate to obtain upright PA and Lateral xrays of the patient at some point early postoperative either before the patient is discharged from the hospital or at the 1st postoperative visit as an outpatient

Restriction of activities

To allow the bone to heal and form a solid arthrodesis, some restriction of sports activities, especially contact sports, is usually advised for 6 months.

Postoperative complications

Early postoperative complications include:

  • Postoperative wound infection
  • Urinary tract infection
  • Respiratory complications such as pneumonia

Late postoperative complications include:

  • Pseudarthrosis with loss of correction
  • Late deep wound infections
  • Proximal junctional failure may occur, and usually is more cosmetic (goose neck appearance) than clinical. Caution is needed specially if progressive kyphosis or fracture above the instrumentation is noted.
  • Distal junctional failure is less common if the guidelines are followed, but shorter fixations may need revision if a symptomatic thoracolumbar kyphosis develops bellow the instrumentation
  • Implant failure or other implant related complications

In the long term adjacent segment degenerations above and below the instrumented spine may occur.

Amount of drainage in the chest tube should be checked frequently. If there is more than 100 cc in the first postoperative hours vascular injury should be suspected and revision of the thoracic cavity might be necessary.

If the right thoracic approach was used, attention should be paid to the lymphatic drainage on the chest tube. This indicates that a thoracic duct injury happened and specialized care should be urgently started.

Chest tube removal should be ordered after drainage stops and control X-rays show adequate lung expansion.

Respiratory physical therapy should be initiated as soon as possible.