General Editor: Luiz Vialle

Authors: Jean Ouellet

Spondylolisthesis Type 1

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Glossary

1 Comment on approach top

Fluoroscopy is used to confirm the correct level of L5 and S1.


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A midline skin incision is performed to access the L5-S1 joint.

The subperiosteal dissection is taken down onto the lamina of L5 exposing the L5-S1 joint

Care must be taken not to violate neither the L5-S1 joint nor the L4-L5 joint.

Dissection is carried laterally onto the transverse process of L5.

2 Decortication top

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Using a high speed burr the defect in the pars articularis must be decorticated and the pseudoarthrosis excised down to bleeding bone.


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Decortication is also taken to the transverse process of L5 along the lamina of L5.

3 Instrumentation top

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The screw entry point is at the trailing edge of the lamina just medial to the inferior facet of L5.


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The screw trajectory runs along the part articularis into the base of the pedicle of L5 in a superolateral direction.

A too anterior screw trajectory may cause the screw to breach into the spinal canal.

A too inferior screw trajector may cause the screw to breach the foramen.


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Use of cannulated screws may facilitate correct screw insertion.

The K-wire is inserted under fluoroscopic control.

To reduce the risk of nerve root entanglement an oscillating gear is used.


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Once the correct trajectory of the K-wire is verified under fluoroscopical control, a self-tapping 4.5mm cortical screw is inserted over the K-wire and the K-wire removed.


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The drill hole is prepared using an oscillating mode to reduce the risk of nerve root entanglement.

A 4.5mm cortical screw is then inserted.

4 Bone grafting top

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A separate incision is made over the posterior superior iliac crest.


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Muscle attached to the outer iliac crest is reflected in a blunt fashion exposing the outer iliac crest.


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Using an osteotome or a gouge, corticocancellous strips are harvested in 4-5 cm length and 1 cm wide.


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Smaller cancellous bone graft is also harvested from the iliac crest and impacted into the pars defect.


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Cortico cancellous strips are laid across the lamina and transverse process.

v1.0 2016-12-01