From: Risk factors for upper adjacent segment degeneration after multi-level posterior lumbar spinal fusion surgery
Interbody fusion levels
Group A (nā=ā22)
Group B (nā=ā49)
Not fused
7
6
L2ā4
0
2
L2ā5
10
L3ā5
9
13
L3ā5 to S1
8
L4ā5
3
5
L4ā5 to S1
4
L5āS1
1