Perioperative data and complications
In the Dynesys group, the mean number of fixed segments was 3.3±0.8. Mean operating time was 258±71minutes, while intraoperative blood loss was was 771±494 ml. One testicular hydrocele case, one oral mucous ulcer case, one upper respiratory infection case, and one pulmonary infection case were resolved after medical treatment. Poor wound healing occurred in 3 cases which was cured by secondary suture. One patient developed transitory radiating pain after surgery, which was relieved by medication. One patient developed muscle weakness of lower extremity, which was recovered by neurotrophic therapy and functional exercise 1 month after surgery. The mean follow-up duration was 38 months (range, 24-76 months). Screw loosening was found on plain radiographs in one patient. There were no cases of incision infection, screw misplacement, screw breakage, or reoperation.
In the Fusion group, the mean number of fixed segments was 4.3±0.8. Mean operating time was 367±59 minutes, while intraoperative blood loss was was 1280±538 ml. One atrial fibrillation case and one Deep venous thrombosis case were resolved after medical treatment. Poor wound healing occurred in 2 cases which was cured by secondary suture. One patient developed surgical site infection, which was cured by antibiotics and debridement. Two patient developed transitory radiating pain after surgery, which was relieved by medication. One patient developed severe low back pain, which was alleviated by symptomatic treatment with non-steroidal anti-inflammatory drugs (NAIDs). The mean follow-up duration was 33 months (range, 23-68 months). There were 3 cases of screw loosening, 1 case of proximal junctional kyphosis, and no cases of implant breakage or pseudarthrosis.
The difference in operation time and blood loss between the two groups was statistically significant (P < 0.05). The Dynesys group had shorter operation time and less blood loss.
Clinical outcomes
In the Dynesys group, the mean VAS scores for low back pain obtained preoperatively, 6 months after surgery and in the last follow-up visit were 5.2±1.7, 2.3±1.4, and 2.1±1.1, respectively. The corresponding mean VAS scores for leg pain were 5.8±1.5, 1.6±0.4, and 1.8±0.9. The corresponding ODI scores were 66.9±17.8, 30.7±12.3, and 21.6±11.6. In the fusion group, the mean VAS scores for low back pain obtained preoperatively, 6 months after surgery and in the last follow-up visit were 5.5±2.0, 3.2±1.2, and 2.8±1.2, respectively. The corresponding mean VAS scores for leg pain were 6.0±2.9, 1.7±0.7, and 2.0 ± 0.8. The corresponding ODI scores were 63.7±19.1, 32.9±14.2, and 30.2±12.9. In both groups, VASback, leg and ODI scores decreased after surgery, and there was a statistically significant difference between preoperative and last follow-up scores (p < 0.05). There was no statistically significant difference in VASback, leg and ODI scores between the two groups preoperative. However, VAS scores for low back pain at 6 months after surgery and at the last follow-up, ODI scores at the last follow-up were lower in the Dynesys group than that in the fusion group, and the difference was statistically significant.
There was no statistically significant difference in LSDI between the two groups before surgery (21.2±10.4 versus 23.1±15.6). The LSDI was significantly less in the Dynesys group as compared to the fusion group at last follow-up (23.8±14.2 versus 40.1±16.4, P<0.05) ( Table 3 ).
Radiological outcomes
Scoliosis Cobb angle
In the Dynesys group, the mean scoliosis Cobb angle was 15.1°±4.4° before surgery, 6.9°±2.7° after surgery, and 6.5°±2.4° at the last follow-up. In the fusion group, the mean scoliosis Cobb angle was 16.9°±2.6° before surgery, 6.4°±3.7° after surgery, and 5.2°±3.3 °at the last follow-up. Compared with preoperative values, the scoliosis Cobb angle in both groups decreased significantly after surgery and at final follow-up (P < 0.05). In the Dynesys group, the difference between postoperative and last follow-up was not statistically significant (P > 0.05). There was no statistically significant difference between the two groups in preoperative, postoperative and at last follow-up (P > 0.05) (Table 4).
Lumbar lodorsis
In the Dynesys group, the mean lumbar lordosis was 31.6°±12.5° before surgery and 36.4°±14.8° after surgery, the difference was statistically significant (P < 0.05). At the last follow-up, the figure was 34.1°±15.3°, showing no statistical difference compared with that after surgery (P > 0.05). In the fusion group, the mean lumbar lordosis was 29.3°±7.7° before operation, and increased to 36.5°±11.1° after operation, with statistically significant difference (P < 0.05). At the last follow-up, the figure was 34.8°±8.9°, showing no statistical difference compared with that after surgery (P > 0.05). There was no statistically significant difference between the two groups in lumbar lordosis before operation, after operation and at the last follow-up (P > 0.05) (Table 4).
Range of motion
ROM values of the implanted segments and L1–S1 levels were measured preoperatively and in the final follow-up. There were no significant differences in the mean ROM values for the implanted segments and the L1–S1 levels between patients in the Dynesys group and fusion group preoperatively (21.9°±12.6° versus 27.3°±14.2°, P > 0.05; 36.0°±16.3° versus 28.4°±11.6°, P > 0.05). However, there were statistical differences in the mean ROM values of the implanted segments and L1–S1 levels between the two groups (10.7±5.1 versus 0.70±0.66, P < 0.05; 29.7±8.0 versus 8.1±1.5, P < 0.05) in the final follow-up (Table 4).