What is lumbar dynamic (flexible rod) stabilisation?

Lumbar dynamic stabilisation (sometimes called “flexible rods” in everyday language) refers to surgical systems that aim to provide stability in the lower back (lumbar spine) by restricting movement in a controlled way, without eliminating it completely. Their main difference from classic rigid (stiff) fusion systems is that, instead of locking the segment completely, they try to preserve a certain amount of movement.

How does dynamic stabilisation work?

In standard lumbar fusion, two vertebrae are fixed to each other with pedicle screws and rigid rods; the goal is for the bones to fuse together over time (fusion).

In dynamic systems:

• Pedicle screws are used (in most systems)
• Between the screws there is a flexible rod, an elastic spacer, a motion-controlled connector or a semi-rigid implant
• The aim is:
• To reduce pain
• To control micro-instability
• To avoid leaving the segment completely immobile
• To reduce the load on the adjacent segment

Example systems:

• Dynesys Dynamic Stabilization System
• Cosmic Dynamic System
• Graf Ligament System

In which patients is it considered?

Mostly in:

• Degenerative disc disease
• Mild to moderate lumbar instability
• Some cases of lumbar spinal stenosis
• Low-grade spondylolisthesis
• Selected patients for whom fusion may be too aggressive

It is generally:

• Advanced instability
• Severe deformity
• Marked scoliosis
• High-grade spondylolisthesis
• Severe osteoporosis

not preferred in patients with these conditions.

Theoretical advantages over rigid systems

Preservation of segment movement

Rigid fusion:

→ Movement ≈ none

Dynamic system:

→ Controlled movement is preserved👍👍👍

In theory, this provides more natural biomechanics.

Potential to reduce adjacent segment disease

The aim of dynamic systems:

• To distribute stress
• To reduce degeneration of the adjacent segment
• Fusion may not be needed

In some systems:

• A bone graft may not be needed
• The risk of pseudarthrosis (failed bone fusion) may be eliminated
• More physiological load transfer

Especially:

• Flexion
• Extension
• Axial loading

may be more natural.

For these reasons, in suitable patients, dynamic stabilisation is important for a comfortable recovery after surgery.