Minimally Invasive Lumbar Fusion
Decompression and Placement of Interbody Spacer
On first look through the tube, a thin layer of muscle can been seen. After removing the muscle, the joints in the back, referred to as facet joints, can be seen. The nerve leaves under the facet joint, and the disc is right in front of it.
The facet joint is drilled away exposing the disc underneath and the exiting nerve root above. Note that the nerve root getting ready to exit from the level below does not need to be retracted much to have good exposure to the disc
While drilling the facet joing away, the bone drillings are saved for use as bone graft. This graft is combined with a special protein called BMP (stands for Bone Morphogenic Protein), which makes bone grow.
The spacer which goes between the vertebral bodies is pictured here. This spacer is shaped like a small brick with rounded edges, with a hollow center to contain the bone graft and BMP. The spacer is made of a special plastic that is invisible on X-ray, but has metallic markers in it. While the whole spacer cannot be seen, the position can be seen on X-ray due to these small markers.
This spacer, along with some additional bone graft, is placed between the vertebral bodies. This spacer helps keep the vertebral bodies from collapsing one on the other (which would lead to less room for the nerves), and creates an environment favorable to fusion between the bones.
Additional bone graft is placed behind the nerve roots as well for what is called a posterolateral fusion (not pictured).