Authors of section

Authors

Alex Vaccaro, Frank Kandziora, Michael Fehlings, Rajasekaran Shanmughanathan

Executive Editor

Luiz Vialle

General Editor

German Ochoa (in memoriam)

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MIS posterior short segment fixation with Schanz pins

1. Introduction

Preliminary remarks

A4 injuries are axial compression injuries and involve a fracture of the posterior wall of the vertebral body and both the superior and inferior end plates. Due to axial compression forces, vertical fracture of the lamina is usually present and does not indicate a tension band failure.

Thoracic and lumbar fractures: Posterior short segment fixation with pedicle screws

Minimally invasive surgery

MIS reduces the surgical trauma for the patient, potentially resulting in a quicker recovery while providing similar clinical mid to long term results.

Decompression

In cases where neurological deficit is observed and compression of the spinal canal is assumed, decompression has to be performed. It should be understood that this is a step that can also result in deterioration of neurology unless very meticulously performed.
Decompression can be performed anteriorly or posteriorly. Posteriorly decompression can be indirect or direct.
Indirect decompression may be tried before performing direct decompression.
Please refer to Decompression techniques for a detailed discussion of indications for the posterior decompression techniques. (Posterior decompression)

Repair of dural laceration

More details on repair of dural laceration can be found here.

2. Patient preparation and approach

3. Closed reduction

Primary reduction is performed by positioning of the patient onto a frame to create lordosis.

Thoracic and lumbar fractures: Posterior short segment fixation with Schanz pins

4. Reduction with Schanz pins

Preliminary remarks

Due to the fact that bilateral instrumentation is necessary in all cases, all steps described below are repeated on the opposite side, unless described otherwise.

Thoracic and lumbar fractures: Posterior short segment fixation with Schanz pins

Pitfall: Multisegmental fixation

In the thoracic spine, multisegmental stabilization is necessary in general.

If this is the case, pedicle screws have to be used instead of Schanz pins.

Schanz pin insertion

In patients with significant kyphosis, PSSF-SS can be used to achieve better fracture reduction and lordosis. However, additional anterior reconstruction may be needed to prevent implant failure.

Schanz pins are inserted into the vertebrae cephalad and caudal to the fracture level on both sides, using the starting point and trajectory as described in pedicle screws. ( Schanz pin insertion)

Thoracic and lumbar fractures: Posterior short segment fixation with Schanz pins

The fracture clamps are placed on the proximal and distal Schanz pins.

Thoracic and lumbar fractures: Posterior short segment fixation with Schanz pins

Rod insertion

The rod is inserted through both the clamps and the whole construct is pushed towards the spine.

Thoracic and lumbar fractures: Posterior short segment fixation with Schanz pins

The distance between the two Schanz pins is secured by tightening the rod to the fracture clamps.

Thoracic and lumbar fractures: Posterior short segment fixation with Schanz pins

Decompression

If it is decided to perform an indirect decompression, this is done at this stage. If indirect decompression proves to be insufficient, a direct decompreesion eg, posterior or transpedicular decompressions are undertaken. Refer to the Posterior Decompression techniques for detailed instructions. ( Posterior decompression)

Thoracic and lumbar fractures: Posterior short segment fixation with Schanz pins

Lordosis

The kyphosis is corrected using the Schanz pins restoring the normal lordosis.

Whenever there is a fracture of the posterior wall (A3/A4/B2), the lordotic correction needs to be supported by C-washers (placed 0.5 cm from the nuts). This will avoid retropulsion of the fractured fragment.
This transfers the center of rotation from the posterior wall to the rod.

Thoracic and lumbar fractures: Posterior short segment fixation with Schanz pins

Normal lordosis is restored.

Thoracic and lumbar fractures: Posterior short segment fixation with Schanz pins

The angle of the Schanz pins is fixed by tightening the Schanz pins to the fracture clamps.

Thoracic and lumbar fractures: Posterior short segment fixation with Schanz pins

Distraction

The rod fixation is released from the fracture clamp and distraction of the Schanz pins is performed using a distraction device or the C-washer. This restores the height of the vertebral body, especially in the posterior part.

Thoracic and lumbar fractures: Posterior short segment fixation with Schanz pins

The distance between the two Schanz pins is secured by tightening the rod to the fracture clamps.

Thoracic and lumbar fractures: Posterior short segment fixation with Schanz pins

When reduction is achieved, the Schanz pins are cut.

Thoracic and lumbar fractures: Posterior short segment fixation with Schanz pins

The final construct is shown from a lateral view.

Thoracic and lumbar fractures: Posterior short segment fixation with Schanz pins

5. Fusion

Decision

Although fusion was routinely performed for all spinal fractures, its indications are now being restricted to fractures that are highly unstable.

Nonfusion fixations can be performed for A3, A4, and B1 type injuries.
Fusion is routinely performed for A2, B2, B3, and all C injuries as they are unstable injuries with extensive soft tissue and ligamentous disruption.

Nonfusion

For nonfusion surgeries, the facet joint capsule is preserved during the entire procedure.

The screws can be removed after 9 months once the fracture has healed.

Thoracic and lumbar fractures: Posterior short segment fixation with Schanz pins

6. Intraoperative imaging

Prior to wound closure, intraoperative imaging is performed to check the adequacy of reduction, position, and length of pins and the overall coronal and sagittal spinal alignment.

mis posterior short segment fixation with schanz pins

7. Aftercare for posterior procedures

Patients are made to sit up in the bed on the first day after surgery. Bracing is optional. Patients with intact neurological status are made to stand and walk on the second day after surgery. Patients can be discharged when medically stable or sent to a rehabilitation center if further care is necessary. This depends on the comfort levels and presence of other associated injuries.

Thoracic and lumbar fractures: Aftercare for anterior procedures

Patients are generally followed with periodical x-rays at 6 weeks, 3 months, 6 months, and 1 year. Normally, 5-10 degrees of loss of kyphosis can be observed within the first 6 months, which does not affect the functional outcomes. For nonfusion surgeries, the implants can be removed once fusion is confirmed.

Thoracic and lumbar fractures: Aftercare for posterior procedures