Patient baseline characteristics
All patients were followed up for 15-37 months: the Isobar TTL group for an average of 22.00 months and the rigid group for an average of 25.18 months. Operation time for the Isobar TTL group ranged from 125 to 199 min (average time = 163.64 min) and that for the rigid group ranged from 145 to 222 min (average time = 185.67 min). Intraoperative blood loss was 245 mL for the Isobar TTL group and 300-1300 mL for the rigid group. There was no statistically significant difference between the two groups with respect to age, bleeding volume during surgery, follow-up period, total hospital stay, and operation time (Table 1).
Table 1 General data of the two study groupsa
General data
|
Isobar TTL (n = 20)
|
Rigid (n = 21)
|
P
|
Age (years)
|
64 ± 7.78
|
61 ± 6.50
|
0.338
|
Sex
|
|
|
|
Female
|
12 (60%)
|
10 (47.62%)
|
0.427
|
Male
|
8 (40%)
|
11 (52.38%)
|
Follow-up (months)
|
22.00 ± 7.01
|
25.18 ± 4.75
|
0.227
|
Operation time (min)
|
163.64 ± 42.42
|
185.67 ± 27.80
|
0.138
|
Intraoperative blood loss (mL)
|
245.45 ± 145.70
|
445.00 ± 305.00
|
0.067
|
Hospital stay (days)
|
20 ± 4.22
|
18.6 ± 1.92
|
0.187
|
aData are presented as mean ± standard deviation.
P values are based on the t test; P > 0.05 for the Isobar TTL group compared with the rigid fixation group.
Clinical efficacy
The ODI of the Isobar TTL group of patients was 81.84 ± 6.63 before surgery and 30.15 ± 4.38 at the last follow-up, a significant improvement from the preoperative value. The ODI of the rigid group of patients on admission was 82.21 ± 5.86 and 28.06 ± 5.39 at the last follow-up, a 65.87% improvement from the preoperative value. The VAS for the Isobar TTL group was 6.82 ± 1.77 points before surgery and 2.75 ± 0.86 points at the last follow-up. The VAS for the rigid group was 6.70 ± 1.51 points before surgery and 2.58 ± 0.86 points at the last follow-up. The ODI and VAS values for the Isobar TTL group and the rigid group at the last follow-up were not significantly different, but the P values of ODI and VAS of the Isobar TTL group were <0.05 before and after surgery. However, there was no significant difference in the improvement of ODI and VAS between the two groups (Table 2).
Table 2 ODI and VAS valuesa
|
Isobar TTL (n = 20)
|
Rigid (n = 21)
|
ODI
|
VAS
|
ODI
|
VAS
|
Before surgery
|
81.84 ± 6.63
|
6.82 ± 1.77
|
82.21 ± 5.86
|
6.70 ± 1.51
|
After surgery
|
30.15 ± 4.38
|
2.75 ± 0.86
|
28.06 ± 5.39
|
2.58 ± 0.86
|
P
|
0.000
|
0.000
|
0.000
|
0.000
|
P ¢
|
|
ODI (0.182)
|
|
VAS (0.530)
|
aData are presented as mean ± standard deviation.
P values are based on the paired t test. P is for postoperative values compared with preoperative values; P < 0.05. P¢ is for the Isobar TTL group compared with the rigid group; P > 0.05 indicates a statistically significant difference.
The Greenough judgment standard of the clinical curative effect showed that the Isobar TTL dynamic group at the last follow-up had an excellentgood rate of 85.0%, while the rigid group had an excellentgood rate of 71.4%. However, there was no significant difference between the Isobar TTL group and the rigid group (P > 0.05) (Table 3).
Table 3 Clinical assessment of the Greenough judgment of the clinical effect
Group
|
n
|
Excellent
|
Good
|
Fair
|
Poor
|
Excellent-Good rate
|
P
|
Isobar TTL
|
20
|
4
|
13
|
3
|
0
|
85.00%
|
1
|
Rigid
|
21
|
2
|
13
|
5
|
1
|
71.40%
|
|
P values are based on the χ2 test. P < 0.05 indicates a statistically significant difference.
Radiological outcomes of fusion rate
At the last follow-up, there were 20 fusion segments in the Isobar TTL group, where 19 were judged as strong fusion and 1 as possible fusion, for a fusion rate of 95.00%. There were 42 fusion segments in the rigid fixation group, where 40 were judged as strong fusion and 2 as possible fusion, for a fusion rate of 97.30%. There was no statistical difference in fusion rate between the two groups (P > 0.05) (Table 4).
Table 4 Fusion rate of the two groups
Grading
|
Isobar TTL (n = 20)
|
Rigid (n = 42)
|
P
|
Fusion
|
19
|
40
|
|
Possible fusion
|
1
|
2
|
|
Nonfusion
|
0
|
0
|
|
Fusion rate (%)
|
95.00
|
95.20
|
1.000
|
P values are based on the χ2 test, P < 0.05 indicates a statistically significant difference.
Radiological outcomes of lumbar mobility and height of intervertebral space
The preoperative and postoperative heights of the intervertebral space in the Isobar TTL and rigid groups are shown in Figure 1. The preoperative heights of the L2/3 and L3/4 intervertebral spaces for the two groups were similar (P > 0.05). In addition, the postoperative height of the L3/4 intervertebral space in the rigid group at the last follow-up was better than that in the Isobar TTL group, which shows that the intervertebral fusion cage helps the recovery of the intervertebral height. However, the height of the intervertebral space between the upper adjacent segment L2/3 in the rigid group was less than that in the Isobar TTL group at the last follow-up (P < 0.05), indicating that the Isobar TTL probably slows down the degeneration of adjacent segments to a certain extent (Fig. 1b).
The preoperative and postoperative radiological parameters, including total lumbar mobility and L2/3 and L3/4 ROM, in both groups are shown in Figure 1. The total lumbar ROM of the two groups at the last follow-up was significantly less than that before surgery (P < 0.05). There was no statistical difference in the total lumbar ROM between the two groups at the last follow-up (P > 0.05) (Fig. 1c).
The ROMs of the fixed segment L3/4 in the Isobar TTL group at the last follow-up were significantly less than those before surgery (P < 0.05), suggesting that the ROMs of the fixed segment in the Isobar TTL group were limited, but some spinal motion was retained. The fixed-segment L3/4 in the rigid group was immobile because it was fused (Fig. 1d).
The ROM of upper adjacent segment L2/3 in the last follow-up of the rigid group increased significantly (P < 0.05), while the ROM of L2/3 in the Isobar TTL group did not change from before surgery to the last follow-up. In addition, the ROM of the upper adjacent segments in the rigid group had increased significantly compared with that in the Isobar TTL group at the last follow-up (P < 0.05), indicating that the Isobar TTL was better than the rigid fixation system in retaining a certain ROM of the lumbar spine.
Radiological outcomes of degeneration in adjacent segments
According to the UCLA system, the incidence of ASD was 5.0% in the Isobar TTL group and 19.0% in the rigid group. Thus, ASD was significantly slower in the Isobar TTL group than in the rigid group (P < 0.05) (Table 6).
Table 5 UCLA system evaluation of intervertebral space (N = 41)
Segment
|
Isobar TTL (n = 20)
|
Rigid (n = 21)
|
L2/3
|
1 (5.0%)
|
4 (19.0%)
|
L3/4
|
1 (5.0%)
|
0 (0.0%)
|
P values are based on the χ2 test. P < 0.05 indicates a statistically significant difference.