Table 1.

In- and exclusion criteria

Inclusion criteria	Exclusion criteria
Clinical und radiographic criteria of a symptomatic lumbar spinal stenosis	Isthmic spondylolisthesis
Failed conservative treatment >3 month	De novo scoliosis >15°
One or two level stenosis	Previous surgery lumbar spine
No signs of segmental instability	Signs of instability > Meyerding I
Age between 45 and 80	Stenosis >2 Level