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Comparison of posterolateral fusion and posterior lumbar interbody fusion for treatment of degenerative spondylolisthesis: Analysis of spino-pelvic sagittal balance and postoperative chronic low back pain
Clinical Neurology and Neurosurgery 171 (2018) 1–5
Contents lists available at ScienceDirect
Clinical Neurology and Neurosurgery journal homepage: www.elsevier.com/locate/clineuro
Comparison of posterolateral fusion and posterior lumbar interbody fusion for treatment of degenerative spondylolisthesis: Analysis of spino-pelvic sagittal balance and postoperative chronic low back pain
T
⁎
Yijian Zhang, Hao Liu, Huilin Yang, Bin Pi
Department of Orthopedic Surgery, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China
A R T I C LE I N FO
A B S T R A C T
Keywords: Degenerative spondylolisthesis Posterolateral fusion Posterior lumbar interbody fusion Spino-Pelvic sagittal balance Chronic low back pain
Objective: This study aims to compare the spino-pelvic sagittal balance and clinical outcomes of patients treated with posterolateral fusion (PLF) and posterior lumbar interbody fusion (PLIF) for degenerative spondylolisthesis. Patients and Methods: A total of 72 patients (28 patients treated with PLF and 44 patients treated with PLIF) were studied. The spino-pelvic sagittal balance, Numerical Rating Scale (NRS), and Oswestry Disability Index (ODI) of the PLF and PLIF groups were compared. The incidence of postoperative chronic low back pain (improvement of NRS less than 50%) in the two groups was also recorded. Results: Significant restoration of spino-pelvic sagittal balance was observed in the PLIF group after surgery. Both groups achieved significant improvements in NRS and ODI postoperatively. Significant differences in postoperative lumbar lordosis and pelvic tilt were found between the PLF and PLIF groups. Significant difference in the incidence of postoperative chronic low back pain was also detected between the two groups. Conclusion: PLF and PLIF can improve the clinical outcomes of patients with degenerative spondylolisthesis. PLIF can achieve better restoration of spino-pelvic sagittal balance parameters and less incidence of postoperative chronic low back pain than PLF.
1. Introduction Posterolateral fusion (PLF) and posterior lumbar interbody fusion (PLIF) are common procedures for treating patients with degenerative spondylolisthesis over the past decades. Both procedures can correct alignment of the lumbar spine, provide early stabilization, and improve functional scores effectively after surgery [1]. However, the better choice between these two procedures is still controversial. La Rosa et al. [2] reported that PLIF can provide superior mechanical strength upon the construct to increase fusion rate, clinical outcomes, and maintain correction of spinal deformity. Aygun et al. [3] found that PLF is accompanied with low blood loss, short operation time, and few complications after surgery. Nevertheless, some studies reported no significant difference in the clinical outcomes between the two procedures [4,5]. Restoration of spino-pelvic sagittal balance in patients undergoing lumbar fusion is an indicator of crucial importance. Previous studies reported that decreased pelvic tilt and increased lumbar lordosis (LL) could be achieved after PLIF, and sufficient restoration of spino-pelvic balance could improve clinical outcomes [6]. Musluman et al. [7]
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reported that PLIF rather than PLF can increase LL and segmental lordosis significantly. Meanwhile, postoperative clinical outcome is correlated with improvement of spino-pelvic sagittal balance. Feng et al. [8] showed that PLIF can achieve higher LL, height of intervertebral disc, and lumbosacral angle than PLF. In addition to common postoperative complications, postoperative chronic low back pain has gained increasing interest recently. Korovessis et al. [9] suggested that sagittal balance of the lumbar spine is related to chronic low back pain after surgery, although the exact etiology is unclear. In this study, we compared the spino-pelvic sagittal balance and clinical outcomes of patients undergoing PLF and PLIF to identify the superior procedure for the treatment of degenerative spondylolisthesis (Fig. 1). 2. Material and methods 2.1. Patients A total of 72 patients treated with PLF or PLIF for degenerative spondylolisthesis from January 2014 to December 2016 were enrolled
Corresponding author. E-mail addresses: [email protected] (Z. Yijian), [email protected] (L. Hao), [email protected] (Y. Huilin), [email protected] (P. Bin).
https://doi.org/10.1016/j.clineuro.2018.04.020 Received 20 February 2018; Received in revised form 9 April 2018; Accepted 21 April 2018 Available online 23 April 2018 0303-8467/ © 2018 Elsevier B.V. All rights reserved.
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anesthesia. A midline incision was made to expose the spinous processes, laminae, and transverse processes. Patients received posterior decompression, and pedicle screw instrumentation (Medtronic Sofamor Danek, Memphis, TN, USA) was used in all patients. In the PLF group, autologous bone harvested from the spinous process and laminae was placed on decorticated transverse processes and facet joints bilaterally. In the PLIF group, a nearly complete discectomy and endplate decortication was performed. Intervertebral disc space spreaders were then sequentially inserted and rotated to restore the normal disc space height. Before cage insertion, the bone from the lamina and spinous process was placed into the cage. Cages (Medtronic Sofamor Danek, Memphis, TN, USA) packed with laminectomy bone were inserted into the disc space (Fig. 3).
2.3. Radiographic data All patients received anterior–posterior and lateral lumbar spine radiograph pre- and postoperatively. LL was defined as the angle between the superior endplate of L1 vertebrae and sacral plate by Cobb’s method. Segmental lordosis (SL) was defined as the angle between the upper endplate of the superior vertebral body and the lower endplate of the inferior vertebral body by Cobb’s method. Sacral slope (SS) was defined as the angle formed between the sacral plate and the horizontal line. Pelvic incidence (PI) was formed by the line perpendicular to the midpoint of sacral plate and the line between the midpoint of the sacral plate and the centroid of femoral heads. Pelvic tilt (PT) was formed by the angle between the line connecting the midpoint of the sacral plate with the centroid of femoral heads and the vertical line. Fig. 1. Spino-pelvic sagittal balance measurement. LL: Lumbar lordosis; SL: Segmental lordosis; SS: Sacral slope; PI: Pelvic incidence; PT: Pelvic tilt.
2.4. Clinical outcomes in this retrospective study. Twenty-eight patients (6 males and 22 females) underwent PLF, whereas 44 patients (14 males and 30 females) underwent PLIF. Inclusion criteria were as follows: (1) patients with single- or double-level degenerative spondylolisthesis; (2) specific nerve compression on computed tomography and magnetic resonance imaging; and (3) patients with neural symptoms resulting from compression. Exclusion criteria included (1) multilevel fusion, (2) spondylolisthesis with trauma, and (3) spondylolisthesis with tumors (Fig. 2).
Numeric Rating Scale (NRS) and Oswestry Disability Index (ODI) were used to evaluate the improvement of clinical outcomes before and after operation. The Macnab criteria was also used to evaluate the outcomes: Excellent, no pain and no restriction of activity; Good, occasional pain of sufficient severity to interfere with normal work; Fair: intermittent pain of sufficient severity to curtail normal work; Poor: unimproved symptoms and insufficient improvement to allow normal work. Patients who categorized as fair or poor and with reduction of NRS less than 50% at least 6 months were considered as chronic low back pain [10,11].
2.2. Surgical procedure All patients were placed in the prone position under general
Fig. 2. Preoperative sagittal lateral view (a), sagittal-computed tomographic scan (b), sagittal T2-weighted magnetic resonance image (c), and postoperative sagittal lateral view (d) of a 64-year-old female patient who suffered from degenerative spondylolisthesis at the L5 level and underwent posterolateral fusion. 2
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Fig. 3. Preoperative sagittal lateral view (a), sagittal computed tomographic scan (b), sagittal T2-weighted magnetic resonance image (c), and postoperative sagittal lateral view (d) of a 46-year-old female patient who suffered from degenerative spondylolisthesis at the L5 level and underwent posterior lumbar interbody fusion.
2.5. Statistical analysis
Table 2 Change of spino-pelvic sagittal balance parameters in PLF group.
In our study, we used SPSS (SPSS Inc., Chicago, IL, USA) to analyze the data. Continuous variables were measured as mean ± deviation. Independent t-test was employed to evaluate the difference of continuous variables. Chi-square test was used to analyze the categorical variables. P values less than 0.05 were considered to indicate significant difference.
LL SL SS PI PT NRS ODI
3. Results
Preoperative
Postoperative
P value
35.0 ± 14.1 21.6 ± 8.4 35.4 ± 11.2 49.6 ± 12.6 18.3 ± 8.8 7.2 ± 1.0 55.2 ± 7.6
33.2 ± 9.7 22.9 ± 8.1 34.9 ± 8.6 50.2 ± 10.5 19.3 ± 9.2 2.8 ± 1.3 22.1 ± 4.8
0.28 0.26 0.70 0.69 0.29 < 0.001* < 0.001*
Abbreviations: LL: lumbar lordosis, SL: segmental lordosis, SS: sacral slope, PI: pelvic incidence, PT: pelvic tilt. * P < 0.05.
All patients finished at least 12 months follow-up with 17.6 ± 1.6 months in the PLF group and 18.1 ± 2.1 months in the PLIF group. In the PLIF group, significant improvements were observed in LL, SL, and PT after surgery. Both two groups also achieved significant improvements in NRS and ODI after surgery. No significant differences in demographic parameters were found between the two groups (Table 1). LL, SL, and PT improved significantly after surgery in the PLIF group (Table 3), whereas no significant difference was observed in the spinopelvic sagittal balance parameters between pre- and postoperative in the PLF group (Table 2). LL and PT differed significantly between the PLF and PLIF groups postoperatively, although no significant differences were observed between the two groups preoperatively (Table 4). Moreover, 7/28 (25%) patients in the PLF group and 2/44 (4.5%) patients in the PLIF group suffered from postoperative chronic low back pain. A significant difference in the incidence of postoperative chronic low back pain was found between the PLF and PLIF groups (Table 5).
Table 3 Change of spino-pelvic sagittal balance parameters in PLIF group.
LL SL SS PI PT NRS ODI
Preoperative
Postoperative
P value
36.1 ± 16.6 19.0 ± 8.7 34.0 ± 12.4 48.8 ± 10.4 18.4 ± 9.6 7.1 ± 1.0 53.8 ± 6.1
39.0 ± 9.8 23.2 ± 7.4 36.5 ± 8.6 48.9 ± 9.9 15.1 ± 5.4 2.3 ± 0.8 22.7 ± 3.0
0.04* < 0.001* 0.075 0.94 0.009* < 0.001* < 0.001*
Abbreviations: LL: lumbar lordosis, SL: segmental lordosis, SS: sacral slope, PI: pelvic incidence, PT: pelvic tilt. * P < 0.05. Table 4 Comparison of spino-pelvic sagittal balance parameters between two groups.
Table 1 Comparison of demographic data between two groups.
Number of patients Sex (male/female) Age Operation segments L3∼L5 L4∼S1 L4∼L5 L5∼S1 Hospital stays (days) Follow-up (months)
PLF group
PLIF group
28 6/22 68.0 ± 9.4
44 14/30 66.1 ± 6.9
13 12 2 1 8.6 ± 1.6 17.6 ± 1.6
14 15 13 2 9.4 ± 2.1 18.1 ± 2.1
Pre-LL Post-LL Pre-SL Post-SL Pre-SS Post-SS Pre-PI Post-PI Pre-PT Post-PT
P value
0.34 0.34 0.09
0.08 0.36
PLF group (n = 28)
PLIF group (n = 44)
P value
35.0 33.2 21.6 22.9 35.4 34.9 49.6 50.2 18.3 19.3
36.1 39.0 19.0 23.2 34.0 36.5 48.8 48.9 18.4 15.1
0.86 0.02* 0.22 0.87 0.63 0.44 0.77 0.59 0.95 0.03*
± ± ± ± ± ± ± ± ± ±
14.1 9.7 8.4 8.1 11.2 8.6 12.6 10.5 8.8 9.2
± ± ± ± ± ± ± ± ± ±
16.6 9.8 8.7 7.4 12.4 8.6 10.4 9.9 9.6 5.4
Abbreviations: LL: lumbar lordosis, SL: segmental lordosis, SS: sacral slope, PI: pelvic incidence, PT: pelvic tilt. * P < 0.05.
*P < 0.05. 3
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degenerative spondylolisthesis is important. A previous study reported that restoration of spino-pelvic sagittal balance is correlated with improvement of postoperative clinical outcomes. Radovanovic et al. [24] revealed that restoration of spino-pelvic sagittal balance (sagittal vertical axis less than 50 mm) is along with good clinical outcomes postoperatively in degenerative spondylolisthesis. Kim et al. [25] found that patients with PT improvement show significantly better Visual Analog Score and ODI scores than those without improvement. Furthermore, in patients with PT improvement, the improvement of clinical outcomes is correlated with postoperative LL. Bourghli et al. [26] demonstrated that patients with poor postoperative clinical outcomes always show bad restoration of spino-pelvic sagittal balance. In the present study, LL, SL, and PT improved significantly in the PLIF group, whereas no significant improvement was observed in the PLF group. This result indicates that added cage or grafts in PLIF can restore the lumbar sagittal balance parameters and counteract the deterioration of pelvic sagittal balance with the improvement of PT. However, simple fusion without intervertebral cage in PLF cannot offer sufficient support to improve the abnormal sagittal balance parameters. Our results also revealed significant differences in postoperative LL and PT between the PLIF and PLF groups, taking a step further to demonstrate that PLIF can achieve better lumbar and pelvic sagittal balance parameters than PLF.
Table 5 Comparison of clinical outcomes between two groups.
Pre-NRS Post-NRS Pre-ODI Post-ODI CLBP
PLF group (n = 28)
PLIF group (n = 44)
P value
7.2 ± 1.0 2.8 ± 1.3 55.2 ± 7.6 22.1 ± 4.8 7 / 28
7.1 ± 1.0 2.3 ± 0.8 53.8 ± 6.1 22.7 ± 3.0 2 / 44
0.68 0.10 0.39 0.56 0.028*
Abbreviations: NRS: Numeric Rating Scale; ODI: Oswestry Disability Index; CLBP: chronic low back pain. * P < 0.05.
4. Discussion Both PLIF and PLF were effective methods for the treatment of degenerative spondylolisthesis. However, the superior one among them was still controversial. In terms of previous meta-analysis, PLIF can achieve better restoration of spinal alignment and higher fusion rate compared with PLF but with no significant difference in clinical outcomes, complication rate, blood loss, and operation time [12–14]. A long-term prospective study by Cunningham et al. [15] reported that PLIF can achieve equivalent or superior clinical outcomes measured by Roland Morris Disability Questionnaire and Low Back Outcome Score than PLF. However, Lee et al. [16] reported that PLIF shows a significantly high incidence of adjacent segment disease because the spinal fixation devices and intervertebral cage or graft can increase segmental rigidity and increase stress transfer to adjacent segments, subsequently accelerating the degenerative process of adjacent segments after surgery. In this study, no significant difference in demographic parameters was found between the PLIF and PLF groups. In both groups, clinical outcomes (NRS and ODI) improved significantly after surgery. No significant difference in pre- and postoperative functional scores was observed between the two groups. These results were consistent with previous studies, indicating that intervertebral fusion exerts no significant effect on global clinical outcomes postoperatively [17,18]. Although most patients had satisfied clinical outcomes after surgery, some patients would suffer from new-onset or recurrent low back pain, which is referred to as “failed back surgery syndrome” or “chronic low back pain” [19]. Unfortunately, the exact reason for postoperative low back pain remains unclear. Wang et al. [20] suggested that paraspinal muscle degeneration and preoperative low back pain are the risk factors for postoperative chronic low back pain. Mukai et al. [21] reported that postoperative intramuscular pressure may be related to low back pain. In the present study, two patients in the PLIF group and seven patients in the PLF group complained with chronic low back pain (improvement of NRS less than 50%). Chi-square test showed significant difference in the incidence of chronic low back pain between the two groups (P = 0.028), indicating that PLIF can lead to better outcomes than PLF. This result may attribute to the setting of the cages or grafts between the vertebral bodies in PLIF, which can increase the stability of segments [22] and maintain the normal lumbar and pelvic sagittal balance parameters. Furthermore, all nine patients with chronic low back pain in our study were accompanied with unchanged even deteriorated restoration of LL or PT. We speculated that insufficient restoration of sagittal balance parameters in PLF cannot defer the degeneration of spondylolisthesis, resulting in the progressive degeneration of lumbar and pelvis and cause chronic or new-onset low back pain. Spino-pelvic sagittal balance is an important factor, and it can worsen with the degenerative process. Patients with degenerative spondylolisthesis showed significantly higher PI and loss of LL and less SS than the normal group, reflecting pelvis back tilt in these patients. Given that PI is a fixed anatomical parameter, patients with degenerative spondylolisthesis are often accompanied with increased PT to compensate this PI increase [23]. Therefore, restoration of the abnormal spino-pelvic sagittal balance parameters for patients with
5. Limitation This study has some limitations. First, the number of patients was small, especially in the PLF group. Second, the follow-up time was not long enough, resulting in the lack of fusion rate data. Third, this study was a retrospective research and was not randomized. Finally, the exact reason of chronic low back pain after surgery was not investigated clearly. Further prospective and large cohort studies are needed in the future. 6. Conclusion Both PLIF and PLF can improve clinical outcomes for patients with degenerative spondylolisthesis. Compared with PLF, PLIF can achieve better restoration of spino-pelvic sagittal balance parameters and less incidence of postoperative chronic low back pain. Conflict of interest No. References [1] S. Madan, N.R. Boeree, Outcome of posterior lumbar interbody fusion versus posterolateral fusion for spondylolytic spondylolisthesis, Spine 27 (14) (2002) 1536–1542. [2] G. La Rosa, A. Conti, F. Cacciola, S. Cardali, D. La Torre, N.M. Gambadauro, F. Tomasello, Pedicle screw fixation for isthmic spondylolisthesis: does posterior lumbar interbody fusion improve outcome over posterolateral fusion? J. Neurosurg. 99 (Suppl. 2) (2003) 143–150. [3] H. Aygun, A. Cakar, N. Huseyinoglu, U. Huseyinoglu, R. Celik, Clinical and radiological comparison of posterolateral fusion and posterior interbody fusion techniques for multilevel lumbar spinal stabilization in manual workers, Asian Spine J. 8 (5) (2014) 571–580, http://dx.doi.org/10.4184/asj.2014.8.5.571. [4] P. Ekman, H. Moller, T. Tullberg, P. Neumann, R. Hedlund, Posterior lumbar interbody fusion versus posterolateral fusion in adult isthmic spondylolisthesis, Spine 32 (20) (2007) 2178–2183, http://dx.doi.org/10.1097/BRS.0b013e31814b1bd8. [5] Z. Lidar, A. Beaumont, J. Lifshutz, D.J. Maiman, Clinical and radiological relationship between posterior lumbar interbody fusion and posterolateral lumbar fusion, Surg. Neurol. 64 (4) (2005) 303–308, http://dx.doi.org/10.1016/j.surneu. 2005.03.025 Discussion 308. [6] Y. Feng, L. Chen, Y. Gu, Z.M. Zhang, H.L. Yang, T.S. Tang, Influence of the posterior lumbar interbody fusion on the sagittal spino-pelvic parameters in isthmic L5-S1 spondylolisthesis, J. Spinal Disord. Techn. 27 (1) (2014) E20–E25, http://dx.doi. org/10.1097/BSD.0b013e31828af6f0. [7] A.M. Musluman, A. Yilmaz, T. Cansever, H. Cavusoglu, I. Colak, H.A. Genc, Y. Aydin, Posterior lumbar interbody fusion versus posterolateral fusion with instrumentation in the treatment of low-grade isthmic spondylolisthesis: midterm
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Contents lists available at ScienceDirect
Clinical Neurology and Neurosurgery journal homepage: www.elsevier.com/locate/clineuro
Comparison of posterolateral fusion and posterior lumbar interbody fusion for treatment of degenerative spondylolisthesis: Analysis of spino-pelvic sagittal balance and postoperative chronic low back pain
T
⁎
Yijian Zhang, Hao Liu, Huilin Yang, Bin Pi
Department of Orthopedic Surgery, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China
A R T I C LE I N FO
A B S T R A C T
Keywords: Degenerative spondylolisthesis Posterolateral fusion Posterior lumbar interbody fusion Spino-Pelvic sagittal balance Chronic low back pain
Objective: This study aims to compare the spino-pelvic sagittal balance and clinical outcomes of patients treated with posterolateral fusion (PLF) and posterior lumbar interbody fusion (PLIF) for degenerative spondylolisthesis. Patients and Methods: A total of 72 patients (28 patients treated with PLF and 44 patients treated with PLIF) were studied. The spino-pelvic sagittal balance, Numerical Rating Scale (NRS), and Oswestry Disability Index (ODI) of the PLF and PLIF groups were compared. The incidence of postoperative chronic low back pain (improvement of NRS less than 50%) in the two groups was also recorded. Results: Significant restoration of spino-pelvic sagittal balance was observed in the PLIF group after surgery. Both groups achieved significant improvements in NRS and ODI postoperatively. Significant differences in postoperative lumbar lordosis and pelvic tilt were found between the PLF and PLIF groups. Significant difference in the incidence of postoperative chronic low back pain was also detected between the two groups. Conclusion: PLF and PLIF can improve the clinical outcomes of patients with degenerative spondylolisthesis. PLIF can achieve better restoration of spino-pelvic sagittal balance parameters and less incidence of postoperative chronic low back pain than PLF.
1. Introduction Posterolateral fusion (PLF) and posterior lumbar interbody fusion (PLIF) are common procedures for treating patients with degenerative spondylolisthesis over the past decades. Both procedures can correct alignment of the lumbar spine, provide early stabilization, and improve functional scores effectively after surgery [1]. However, the better choice between these two procedures is still controversial. La Rosa et al. [2] reported that PLIF can provide superior mechanical strength upon the construct to increase fusion rate, clinical outcomes, and maintain correction of spinal deformity. Aygun et al. [3] found that PLF is accompanied with low blood loss, short operation time, and few complications after surgery. Nevertheless, some studies reported no significant difference in the clinical outcomes between the two procedures [4,5]. Restoration of spino-pelvic sagittal balance in patients undergoing lumbar fusion is an indicator of crucial importance. Previous studies reported that decreased pelvic tilt and increased lumbar lordosis (LL) could be achieved after PLIF, and sufficient restoration of spino-pelvic balance could improve clinical outcomes [6]. Musluman et al. [7]
⁎
reported that PLIF rather than PLF can increase LL and segmental lordosis significantly. Meanwhile, postoperative clinical outcome is correlated with improvement of spino-pelvic sagittal balance. Feng et al. [8] showed that PLIF can achieve higher LL, height of intervertebral disc, and lumbosacral angle than PLF. In addition to common postoperative complications, postoperative chronic low back pain has gained increasing interest recently. Korovessis et al. [9] suggested that sagittal balance of the lumbar spine is related to chronic low back pain after surgery, although the exact etiology is unclear. In this study, we compared the spino-pelvic sagittal balance and clinical outcomes of patients undergoing PLF and PLIF to identify the superior procedure for the treatment of degenerative spondylolisthesis (Fig. 1). 2. Material and methods 2.1. Patients A total of 72 patients treated with PLF or PLIF for degenerative spondylolisthesis from January 2014 to December 2016 were enrolled
Corresponding author. E-mail addresses: [email protected] (Z. Yijian), [email protected] (L. Hao), [email protected] (Y. Huilin), [email protected] (P. Bin).
https://doi.org/10.1016/j.clineuro.2018.04.020 Received 20 February 2018; Received in revised form 9 April 2018; Accepted 21 April 2018 Available online 23 April 2018 0303-8467/ © 2018 Elsevier B.V. All rights reserved.
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anesthesia. A midline incision was made to expose the spinous processes, laminae, and transverse processes. Patients received posterior decompression, and pedicle screw instrumentation (Medtronic Sofamor Danek, Memphis, TN, USA) was used in all patients. In the PLF group, autologous bone harvested from the spinous process and laminae was placed on decorticated transverse processes and facet joints bilaterally. In the PLIF group, a nearly complete discectomy and endplate decortication was performed. Intervertebral disc space spreaders were then sequentially inserted and rotated to restore the normal disc space height. Before cage insertion, the bone from the lamina and spinous process was placed into the cage. Cages (Medtronic Sofamor Danek, Memphis, TN, USA) packed with laminectomy bone were inserted into the disc space (Fig. 3).
2.3. Radiographic data All patients received anterior–posterior and lateral lumbar spine radiograph pre- and postoperatively. LL was defined as the angle between the superior endplate of L1 vertebrae and sacral plate by Cobb’s method. Segmental lordosis (SL) was defined as the angle between the upper endplate of the superior vertebral body and the lower endplate of the inferior vertebral body by Cobb’s method. Sacral slope (SS) was defined as the angle formed between the sacral plate and the horizontal line. Pelvic incidence (PI) was formed by the line perpendicular to the midpoint of sacral plate and the line between the midpoint of the sacral plate and the centroid of femoral heads. Pelvic tilt (PT) was formed by the angle between the line connecting the midpoint of the sacral plate with the centroid of femoral heads and the vertical line. Fig. 1. Spino-pelvic sagittal balance measurement. LL: Lumbar lordosis; SL: Segmental lordosis; SS: Sacral slope; PI: Pelvic incidence; PT: Pelvic tilt.
2.4. Clinical outcomes in this retrospective study. Twenty-eight patients (6 males and 22 females) underwent PLF, whereas 44 patients (14 males and 30 females) underwent PLIF. Inclusion criteria were as follows: (1) patients with single- or double-level degenerative spondylolisthesis; (2) specific nerve compression on computed tomography and magnetic resonance imaging; and (3) patients with neural symptoms resulting from compression. Exclusion criteria included (1) multilevel fusion, (2) spondylolisthesis with trauma, and (3) spondylolisthesis with tumors (Fig. 2).
Numeric Rating Scale (NRS) and Oswestry Disability Index (ODI) were used to evaluate the improvement of clinical outcomes before and after operation. The Macnab criteria was also used to evaluate the outcomes: Excellent, no pain and no restriction of activity; Good, occasional pain of sufficient severity to interfere with normal work; Fair: intermittent pain of sufficient severity to curtail normal work; Poor: unimproved symptoms and insufficient improvement to allow normal work. Patients who categorized as fair or poor and with reduction of NRS less than 50% at least 6 months were considered as chronic low back pain [10,11].
2.2. Surgical procedure All patients were placed in the prone position under general
Fig. 2. Preoperative sagittal lateral view (a), sagittal-computed tomographic scan (b), sagittal T2-weighted magnetic resonance image (c), and postoperative sagittal lateral view (d) of a 64-year-old female patient who suffered from degenerative spondylolisthesis at the L5 level and underwent posterolateral fusion. 2
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Fig. 3. Preoperative sagittal lateral view (a), sagittal computed tomographic scan (b), sagittal T2-weighted magnetic resonance image (c), and postoperative sagittal lateral view (d) of a 46-year-old female patient who suffered from degenerative spondylolisthesis at the L5 level and underwent posterior lumbar interbody fusion.
2.5. Statistical analysis
Table 2 Change of spino-pelvic sagittal balance parameters in PLF group.
In our study, we used SPSS (SPSS Inc., Chicago, IL, USA) to analyze the data. Continuous variables were measured as mean ± deviation. Independent t-test was employed to evaluate the difference of continuous variables. Chi-square test was used to analyze the categorical variables. P values less than 0.05 were considered to indicate significant difference.
LL SL SS PI PT NRS ODI
3. Results
Preoperative
Postoperative
P value
35.0 ± 14.1 21.6 ± 8.4 35.4 ± 11.2 49.6 ± 12.6 18.3 ± 8.8 7.2 ± 1.0 55.2 ± 7.6
33.2 ± 9.7 22.9 ± 8.1 34.9 ± 8.6 50.2 ± 10.5 19.3 ± 9.2 2.8 ± 1.3 22.1 ± 4.8
0.28 0.26 0.70 0.69 0.29 < 0.001* < 0.001*
Abbreviations: LL: lumbar lordosis, SL: segmental lordosis, SS: sacral slope, PI: pelvic incidence, PT: pelvic tilt. * P < 0.05.
All patients finished at least 12 months follow-up with 17.6 ± 1.6 months in the PLF group and 18.1 ± 2.1 months in the PLIF group. In the PLIF group, significant improvements were observed in LL, SL, and PT after surgery. Both two groups also achieved significant improvements in NRS and ODI after surgery. No significant differences in demographic parameters were found between the two groups (Table 1). LL, SL, and PT improved significantly after surgery in the PLIF group (Table 3), whereas no significant difference was observed in the spinopelvic sagittal balance parameters between pre- and postoperative in the PLF group (Table 2). LL and PT differed significantly between the PLF and PLIF groups postoperatively, although no significant differences were observed between the two groups preoperatively (Table 4). Moreover, 7/28 (25%) patients in the PLF group and 2/44 (4.5%) patients in the PLIF group suffered from postoperative chronic low back pain. A significant difference in the incidence of postoperative chronic low back pain was found between the PLF and PLIF groups (Table 5).
Table 3 Change of spino-pelvic sagittal balance parameters in PLIF group.
LL SL SS PI PT NRS ODI
Preoperative
Postoperative
P value
36.1 ± 16.6 19.0 ± 8.7 34.0 ± 12.4 48.8 ± 10.4 18.4 ± 9.6 7.1 ± 1.0 53.8 ± 6.1
39.0 ± 9.8 23.2 ± 7.4 36.5 ± 8.6 48.9 ± 9.9 15.1 ± 5.4 2.3 ± 0.8 22.7 ± 3.0
0.04* < 0.001* 0.075 0.94 0.009* < 0.001* < 0.001*
Abbreviations: LL: lumbar lordosis, SL: segmental lordosis, SS: sacral slope, PI: pelvic incidence, PT: pelvic tilt. * P < 0.05. Table 4 Comparison of spino-pelvic sagittal balance parameters between two groups.
Table 1 Comparison of demographic data between two groups.
Number of patients Sex (male/female) Age Operation segments L3∼L5 L4∼S1 L4∼L5 L5∼S1 Hospital stays (days) Follow-up (months)
PLF group
PLIF group
28 6/22 68.0 ± 9.4
44 14/30 66.1 ± 6.9
13 12 2 1 8.6 ± 1.6 17.6 ± 1.6
14 15 13 2 9.4 ± 2.1 18.1 ± 2.1
Pre-LL Post-LL Pre-SL Post-SL Pre-SS Post-SS Pre-PI Post-PI Pre-PT Post-PT
P value
0.34 0.34 0.09
0.08 0.36
PLF group (n = 28)
PLIF group (n = 44)
P value
35.0 33.2 21.6 22.9 35.4 34.9 49.6 50.2 18.3 19.3
36.1 39.0 19.0 23.2 34.0 36.5 48.8 48.9 18.4 15.1
0.86 0.02* 0.22 0.87 0.63 0.44 0.77 0.59 0.95 0.03*
± ± ± ± ± ± ± ± ± ±
14.1 9.7 8.4 8.1 11.2 8.6 12.6 10.5 8.8 9.2
± ± ± ± ± ± ± ± ± ±
16.6 9.8 8.7 7.4 12.4 8.6 10.4 9.9 9.6 5.4
Abbreviations: LL: lumbar lordosis, SL: segmental lordosis, SS: sacral slope, PI: pelvic incidence, PT: pelvic tilt. * P < 0.05.
*P < 0.05. 3
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degenerative spondylolisthesis is important. A previous study reported that restoration of spino-pelvic sagittal balance is correlated with improvement of postoperative clinical outcomes. Radovanovic et al. [24] revealed that restoration of spino-pelvic sagittal balance (sagittal vertical axis less than 50 mm) is along with good clinical outcomes postoperatively in degenerative spondylolisthesis. Kim et al. [25] found that patients with PT improvement show significantly better Visual Analog Score and ODI scores than those without improvement. Furthermore, in patients with PT improvement, the improvement of clinical outcomes is correlated with postoperative LL. Bourghli et al. [26] demonstrated that patients with poor postoperative clinical outcomes always show bad restoration of spino-pelvic sagittal balance. In the present study, LL, SL, and PT improved significantly in the PLIF group, whereas no significant improvement was observed in the PLF group. This result indicates that added cage or grafts in PLIF can restore the lumbar sagittal balance parameters and counteract the deterioration of pelvic sagittal balance with the improvement of PT. However, simple fusion without intervertebral cage in PLF cannot offer sufficient support to improve the abnormal sagittal balance parameters. Our results also revealed significant differences in postoperative LL and PT between the PLIF and PLF groups, taking a step further to demonstrate that PLIF can achieve better lumbar and pelvic sagittal balance parameters than PLF.
Table 5 Comparison of clinical outcomes between two groups.
Pre-NRS Post-NRS Pre-ODI Post-ODI CLBP
PLF group (n = 28)
PLIF group (n = 44)
P value
7.2 ± 1.0 2.8 ± 1.3 55.2 ± 7.6 22.1 ± 4.8 7 / 28
7.1 ± 1.0 2.3 ± 0.8 53.8 ± 6.1 22.7 ± 3.0 2 / 44
0.68 0.10 0.39 0.56 0.028*
Abbreviations: NRS: Numeric Rating Scale; ODI: Oswestry Disability Index; CLBP: chronic low back pain. * P < 0.05.
4. Discussion Both PLIF and PLF were effective methods for the treatment of degenerative spondylolisthesis. However, the superior one among them was still controversial. In terms of previous meta-analysis, PLIF can achieve better restoration of spinal alignment and higher fusion rate compared with PLF but with no significant difference in clinical outcomes, complication rate, blood loss, and operation time [12–14]. A long-term prospective study by Cunningham et al. [15] reported that PLIF can achieve equivalent or superior clinical outcomes measured by Roland Morris Disability Questionnaire and Low Back Outcome Score than PLF. However, Lee et al. [16] reported that PLIF shows a significantly high incidence of adjacent segment disease because the spinal fixation devices and intervertebral cage or graft can increase segmental rigidity and increase stress transfer to adjacent segments, subsequently accelerating the degenerative process of adjacent segments after surgery. In this study, no significant difference in demographic parameters was found between the PLIF and PLF groups. In both groups, clinical outcomes (NRS and ODI) improved significantly after surgery. No significant difference in pre- and postoperative functional scores was observed between the two groups. These results were consistent with previous studies, indicating that intervertebral fusion exerts no significant effect on global clinical outcomes postoperatively [17,18]. Although most patients had satisfied clinical outcomes after surgery, some patients would suffer from new-onset or recurrent low back pain, which is referred to as “failed back surgery syndrome” or “chronic low back pain” [19]. Unfortunately, the exact reason for postoperative low back pain remains unclear. Wang et al. [20] suggested that paraspinal muscle degeneration and preoperative low back pain are the risk factors for postoperative chronic low back pain. Mukai et al. [21] reported that postoperative intramuscular pressure may be related to low back pain. In the present study, two patients in the PLIF group and seven patients in the PLF group complained with chronic low back pain (improvement of NRS less than 50%). Chi-square test showed significant difference in the incidence of chronic low back pain between the two groups (P = 0.028), indicating that PLIF can lead to better outcomes than PLF. This result may attribute to the setting of the cages or grafts between the vertebral bodies in PLIF, which can increase the stability of segments [22] and maintain the normal lumbar and pelvic sagittal balance parameters. Furthermore, all nine patients with chronic low back pain in our study were accompanied with unchanged even deteriorated restoration of LL or PT. We speculated that insufficient restoration of sagittal balance parameters in PLF cannot defer the degeneration of spondylolisthesis, resulting in the progressive degeneration of lumbar and pelvis and cause chronic or new-onset low back pain. Spino-pelvic sagittal balance is an important factor, and it can worsen with the degenerative process. Patients with degenerative spondylolisthesis showed significantly higher PI and loss of LL and less SS than the normal group, reflecting pelvis back tilt in these patients. Given that PI is a fixed anatomical parameter, patients with degenerative spondylolisthesis are often accompanied with increased PT to compensate this PI increase [23]. Therefore, restoration of the abnormal spino-pelvic sagittal balance parameters for patients with
5. Limitation This study has some limitations. First, the number of patients was small, especially in the PLF group. Second, the follow-up time was not long enough, resulting in the lack of fusion rate data. Third, this study was a retrospective research and was not randomized. Finally, the exact reason of chronic low back pain after surgery was not investigated clearly. Further prospective and large cohort studies are needed in the future. 6. Conclusion Both PLIF and PLF can improve clinical outcomes for patients with degenerative spondylolisthesis. Compared with PLF, PLIF can achieve better restoration of spino-pelvic sagittal balance parameters and less incidence of postoperative chronic low back pain. Conflict of interest No. References [1] S. Madan, N.R. Boeree, Outcome of posterior lumbar interbody fusion versus posterolateral fusion for spondylolytic spondylolisthesis, Spine 27 (14) (2002) 1536–1542. [2] G. La Rosa, A. Conti, F. Cacciola, S. Cardali, D. La Torre, N.M. Gambadauro, F. Tomasello, Pedicle screw fixation for isthmic spondylolisthesis: does posterior lumbar interbody fusion improve outcome over posterolateral fusion? J. Neurosurg. 99 (Suppl. 2) (2003) 143–150. [3] H. Aygun, A. Cakar, N. Huseyinoglu, U. Huseyinoglu, R. Celik, Clinical and radiological comparison of posterolateral fusion and posterior interbody fusion techniques for multilevel lumbar spinal stabilization in manual workers, Asian Spine J. 8 (5) (2014) 571–580, http://dx.doi.org/10.4184/asj.2014.8.5.571. [4] P. Ekman, H. Moller, T. Tullberg, P. Neumann, R. Hedlund, Posterior lumbar interbody fusion versus posterolateral fusion in adult isthmic spondylolisthesis, Spine 32 (20) (2007) 2178–2183, http://dx.doi.org/10.1097/BRS.0b013e31814b1bd8. [5] Z. Lidar, A. Beaumont, J. Lifshutz, D.J. Maiman, Clinical and radiological relationship between posterior lumbar interbody fusion and posterolateral lumbar fusion, Surg. Neurol. 64 (4) (2005) 303–308, http://dx.doi.org/10.1016/j.surneu. 2005.03.025 Discussion 308. [6] Y. Feng, L. Chen, Y. Gu, Z.M. Zhang, H.L. Yang, T.S. Tang, Influence of the posterior lumbar interbody fusion on the sagittal spino-pelvic parameters in isthmic L5-S1 spondylolisthesis, J. Spinal Disord. Techn. 27 (1) (2014) E20–E25, http://dx.doi. org/10.1097/BSD.0b013e31828af6f0. [7] A.M. Musluman, A. Yilmaz, T. Cansever, H. Cavusoglu, I. Colak, H.A. Genc, Y. Aydin, Posterior lumbar interbody fusion versus posterolateral fusion with instrumentation in the treatment of low-grade isthmic spondylolisthesis: midterm
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