A total of 242 patients were finally enrolled in the study. CS was identified in 79 (32.6%) patients, including 48 (19.8%) in the MCS group and 31 (12.8%) in the SCS group. The remaining 163 (67.4%) patients were assigned to the NCS group. There were no significant differences in demographic parameters between the three groups (Table 1).
Table 1
Comparative analysis of demographics between three groups
|
NCS group
|
MCS group
|
SCS group
|
P
|
Patients (n)
|
163
|
48
|
31
|
-
|
Sex
(Male: female)
|
65:98
|
19:29
|
14:17
|
0.851
|
BMI (Kg/m²)
|
24.7 ± 3.4
|
25.4 ± 3.1
|
24.5 ± 3.1
|
0.342
|
Age (years)
|
64.5 ± 9.1
|
66.3 ± 10.7
|
69.1 ± 9.9
|
0.099
|
Diagnosed with DS (Yes: No)
|
55:108
|
22:26
|
11:20
|
0.308
|
Data presented as mean ± standard deviation. DS, degenerative spondylolisthesis. |
Characteristics Of Subsidence
The significant DH decrease of the subsidence segments occurred within 3 months postoperatively, from 11.0 ± 1.7 mm 1 day postoperatively to 8.5 ± 2.0 mm 1 month postoperatively (P < 0.001) and continued to 7.6 ± 1.9 mm at 3 months postoperatively (P = 0.003). Compared with 3 months postoperatively, the DH only slightly decreased to 7.3 ± 1.9 mm (P = 0.291) and 7.1 ± 1.8 mm (P = 0.084) at 6 and 12 months postoperatively (Fig. 2). At 1 month postoperatively, a total of 61 patients were identified with CS including 51 with MCS and 10 with SCS. This number increased to 79 at 3 months postoperatively, including 55 with MCS and 24 with SCS, indicating that significantly decreased in the ratio of MCS to SCS (P = 0.042). After 3 months postoperatively, no additional CS occurred. Only 5 and 2 segments developed from MCS to SCS at 6 and 12 months postoperatively, without no significantly changes in the ratio of MCS to SCS segments (P = 0.250, 0.156) compared to the 3 months postoperatively. (Fig. 3). A total of 44 CS occurred in the caudal endplate, 30 occurred in both caudal and cranial endplates, and the remaining 5 only occurred in the cranial endplate. Typical radiological datum is shown in Fig. 1.
Clinical And Radiological Results
The clinical outcomes of three groups are presented in Table 2 and Fig. 4. No significant differences in the clinical score between the three groups preoperatively (P = 0.069, 0.085, 0.094). At 1 month postoperatively, ODI and VAS scores of lower backs in MCS group were significantly higher than those in NCS group (P < 0.001), but significantly lower than those in SCS group (P < 0.001). There were no significant differences in VAS scores of legs between NCS and MCS groups 1 month postoperatively (P = 0.057), and both of them were significantly lower than those in SCS group (P < 0.001). At 3 months postoperatively, there were no significantly difference in all clinical results between NCS and MCS groups (P = 0.064, 0.836, 0.180), and both significantly lower than those in SCS group (P < 0.001). At 12 months postoperatively, ODI and VAS score of lower back in NCS and MCS groups were significantly lower than those of SCS groups (P < 0.001), while VAS score of leg were comparable between three groups (P(NCS−SCS) = 0.775, P(MCS−SCS) = 0.724).
Table 2
The clinical outcomes between three groups
|
NCS group
|
MCS group
|
SCS group
|
VAS-lower back
|
Pre-
|
6.0 ± 1.0
|
6.2 ± 0.9
|
6.3 ± 1.1
|
1m post-
|
3.0 ± 0.9*
|
4.1 ± 1.0*…
|
5.3 ± 1.2*…^
|
3m post-
|
2.6 ± 0.9#
|
3.0 ± 1.1#
|
4.5 ± 1.3#…^
|
12m post-
|
1.9 ± 0.8&
|
2.1 ± 1.0&
|
3.2 ± 1.1&…^
|
VAS-leg
|
Pre-
|
5.3 ± 1.1
|
5.6 ± 1.2
|
5.7 ± 1.2
|
1m post-
|
2.7 ± 0.8*
|
3.0 ± 0.8*
|
3.8 ± 0.9*…^
|
3m post-
|
2.3 ± 1.0#
|
2.4 ± 0.9#
|
3.1 ± 1.0#…^
|
12m post-
|
2.0 ± 1.0&
|
2.1 ± 0.9&
|
2.3 ± 1.0&
|
ODI
|
Pre-
|
35.9 ± 5.2
|
37.7 ± 4.9
|
36.9 ± 5.1
|
1m post-
|
20.7 ± 4.8*
|
24.9 ± 6.4*…
|
30.3 ± 5.9*…^
|
3m post-
|
14.7 ± 4.8#
|
16.1 ± 4.9#
|
23.1 ± 6.1#…^
|
12m post-
|
10.8 ± 4.4&
|
12.2 ± 5.0&
|
17.6 ± 6.3&…^
|
Data presented as mean ± standard deviation. Pre-, preoperative; post-, postoperative. |
*, P < 0.01, compared to pre-; #, P < 0.01, compared to 1m post-; &, P < 0.05, compared to 3m post-.…, P < 0.01, compared to NCS group; ^, P < 0.01, compared to MCS group. |
The fusion rates were 92.6% (151/163), 83.3% (40/48) and 64.5% (20/31) in NCS, MCS and SCS groups, respectively. No significant differences in fusion rates between NCS and MCS groups (P = 0.053) or MCS and SCS groups were observed (P = 0.056). However, fusion rate in the SCS group was significantly lower than that in NCS group (P < 0.001)
Risk Factors
In UBLR analysis, BMD (P < 0.001), distraction of DH (P = 0.019), disc space morphology (P = 0.044), endplate sclerosis (P = 0.075), and endplate injury (P = 0.001) were significantly associated with CS, while age, sex, BMI, diagnosis, and cage position were not (Table 3). In the further MBLR analysis (Fig. 5), osteoporosis and endplate injury showed as significant risk factor for CS (P < 0.001), the adjusted odds ratio (OR) were 5.976 (2.636–13.548) and 6.135 (2.337–16.105), respectively. In addition, the flat disk space and the DH overdistraction were also significantly correlated with the increased probability of CS (P < 0.01), the adjusted OR were presented as 3.309 (1.670–6.558) and 1.775 (1.360–2.316), respectively. In contrast, endplate sclerosis showed as a significant protective factor for CS (P = 0.019), with the adjusted OR of 0.120 (0.020–0.703).
Table 3
Outcomes of univariate binary logistic regression analysis for risk factors
Factors
|
CS group
|
NCS group
|
Rough OR (95% CI)
|
P
|
Sex (male: female)
|
34:45
|
65:98
|
1.082:1(0.626–1.867)
|
0.778
|
Age (years)
|
67.1 ± 10.4
|
64.5 ± 9.1
|
1.437:1(0.833–2.479)
|
0.192
|
BMI (Kg/m²)
|
25.0 ± 3.1
|
24.7 ± 3.4
|
1.213:1(0.692–2.128)
|
0.500
|
Diagnosed with DS (Yes: No)
|
33:46
|
55:108
|
1.409:1(0.811–2.448)
|
0.224
|
BMD (≤-2.5: >-2.5)
|
24:51
|
22:142
|
3.935:1(2.020–7.668)
|
< 0.001*
|
DH distraction (mm)
|
3.3 ± 1.4
|
2.9 ± 1.3
|
1.267 (1.039–1.544)
|
0.019*
|
Disk space morphology
|
|
|
(Flat: Concave)
|
42:29
|
59:83
|
2.037:1(1.142–3.635)
|
0.016*
|
(Irregular: Concave)
|
8:29
|
21:83
|
1.090:1(0.436–2.729)
|
0.835
|
Endplate injury
(Yes: No)
|
18:61
|
11:152
|
4.077:1(1.820–9.136)
|
0.001*
|
Endplate sclerosis
(Yes: No)
|
2:77
|
15:148
|
3.902:1(0.870-17.503)
|
0.075*
|
Cage position
|
22.8 ± 7.4%
|
22.4 ± 7.0%
|
2.735(0.060-124.657)
|
0.606
|
Data presented as mean ± standard deviation. DS, degenerative spondylolisthesis. *: P<0.15, statisticalsignificance for univariate binary logistic regression analysis. |