When a dorsal fusion is done in combination with a ALIF, TLIF or PLIF, it is called a 360 fusion. 360 fusions offer more stability than a simple fusion alone and hence a greater chance of a successful bone fusion. The major difference between the TLIF and PLIF is that the TLIF entry is about 1 cm more medial. In the ALIV TLIF and PLIF a cage is put into the intervertabral disc space. The ALIF, TLIF and PLIF bear the load of the intervertebral disc space.
360 fusion with an ALIF is the strongest of the 360 fusions, because the cages are larger and there is less possibility of movement after surgery, therefore give more opportunity for bones to grow together. Fusions rely on bone growth to be successful, not the instrumentation.
A dorsal fusion is made by creating a bony bridge in the facet joint or it can be done with a pedicle screw system like Dynamic Spine Stabilization (DSS). In facet joint type of dorsal fusion cartilage and synovial sac of the facet joint are removed and the bone on the inside surfaces of the facet joint is roughed up to encourage osteophyte growth. A small piece of bone or other material in place inside the facet joint after the pedicle screws are implanted. The connecting rods to the screws are used to compress the facets and their contents together encouraging bone to fuse.
Once the fusion is complete, the screws and rods can be removed, but this would be rare case. Except for unusual circumstance, the screws are never removed. The DSS system offers pedicle screws and connectors, which allow for connections between the fused segments and the motion segment. This is quite unique in the spine world and is preferred by Dr. Bertagnoli. If you one needs something else at an adjacent level in the future and you had the dorsal fusion using DSS, the screws and connectors of the DSS could allow for inter-connectivity between the motion and fused sections, yielding greater stability and less trauma from surgery.