Table 1.

Demographic characteristics of the groups

	PS loosening (+)	PS loosening (−)	P
N	7	34
% female	14	55
age	69.8 ± 8.7	67.0 ± 10.9	0.23
Average N of fused segments of	5.5 ± 3.1	4.9 ± 4.1	0.51
Average of the examination period after surgery (weeks)	21.7	15.1	0.06
Displacement angle	5.7 ± 5.1	0.6 ± 0.5	< 0.00001
N of revision surgeries	2	0