PEEK versus Silicon Interspinous Spacer for Reduction of Supradjacent Segment Degeneration following Decompression and Short-Segment Instrumentation for Degenerative Lumbar Spinal Stenosis

Table 5

Pfirrmann classification in the supradjacent and subjacent segment preoperatively till the final follow-up.

2nd Supradjacent Group	Preoperatively		Postoperatively
	II	III	I	II	III
R (n=17)	16	1	15	2	0
S (n= 18)	17	1	16	2	0
C (n=20)	18	2	17	3	0
Subjacent Group	I	II	I	II	III
R (n=14/17)	11	3	10	4	0
S (n= 16/18)	12	4	11	3	2
C (n=17/20)	14	3	13	3	1

,, The segments per group with L5-S1 fusion that were excluded from ASD evaluation.