59: Posterior Instrumented Reduction and Fusion for Spondylolisthesis

Posterior Instrumented Reduction and Fusion for Spondylolisthesis

Eric W. Tan and Paul D. Sponseller

Indications

Back pain not relieved by 6–12 months of conservative treatment: nonsteroidal anti-inflammatory drugs (NSAIDs), activity modification, back brace, physical/occupational therapy

Radiculopathy of significant nature unrelieved by rest or analgesics

Neurologic signs or symptoms (e.g., significant leg pain, bowel/bladder changes, claudication)

Persistent postural/gait abnormalities

Grade III spondylolisthesis or higher

Pain or progression of spondylolisthesis of lower degree

Pitfalls

• Increased risk of progression in skeletally immature patients without surgery (this is mainly an increase if grade III or IV)

Controversies

• Risk of neurologic injury and disk degeneration with surgical correction

• Risk of slip progression with posterior fusion secondary to shear forces on the fusion mass

• Risk of disk degeneration in adjacent segments

• Risk of pseudoarthrosis

• Need for reduction of spondylolisthesis. Alternatives to in situ fusion/fixation include open/closed reduction plus fusion, combined anterior-posterior approaches or posterior plus anterior interbody fusion, and fixation with pedicle screw constructs. In situ fusion without reduction is a time-honored procedure that works for many patients. It does require fusion to L4 in grade III and higher slips, and does leave the patient with some residual deformity. This can be done with posterior, anterior, or posterior interbody grafts. The Bohlman procedure is one that has a high rate of success with minimal incision.

• The patient may choose in situ fusion with a higher rate of pseudarthrosis and progression and residual deformity, but lower L5 nerve root risk; versus reduction and fusion of the slip with more correction of deformity, avoidance of fusion to L4, higher fusion rate, and higher risk of L5 nerve palsy.

Examination/Imaging

Anteroposterior (AP) and lateral plain film radiographs are obtained. Figure 1 depicts a preoperative lateral view of grade IV spondylolisthesis (L5-S1).

FIGURE 1

Computed tomography (CT) scan of the lumbar spine is also obtained.

Magnetic resonance imaging (MRI) of the lumbar spine is used to assess spinal cord/nerve integrity and ligamentous structures. Figure 2 depicts a preoperative sagittal MRI of grade II spondylolisthesis (L5-S1).

FIGURE 2

Surgical Anatomy

Palpable stepoff of spinous processes is one level above vertebral body stepoff.

The posterior elements of the slipped vertebral body are hypermobile (“wobbly”).

L5 transverse processes are deeply recessed.

Posterior elements of L5 and S1 may be bifid.

Positioning

The patient is placed prone on a radiolucent table. The table should produce no imaging artifact for PA and lateral projections of L4-S2.

Spinal cord monitoring should include electromyography and nerve root monitoring and sphincter monitoring.

Pearls

• Minimize (flatten) lumbar lordosis.

• The abdomen should be free.

• The hips and knees should be gently flexed about 45°.

Pitfalls

• Be sure that AP and lateral radiographs clearly show L4-S1.

Equipment

• Radiolucent spine table

Portals/Exposures

A 4- to 6-cm midline posterior longitudinal exposure is made.

Exposure continues to the transverse processes of L5.

The ala of the sacrum is exposed.

Posterior elements of L5 are excised below the pars defect after exposure is complete.

Tags: Operative Techniques Pediatric Orthopaedic Surgery

Jun 7, 2016 | Posted by admin in ORTHOPEDIC | Comments Off

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