DOI: https://doi.org/10.21203/rs.3.rs-2415070/v1
We aimed to retrospectively analyze the clinical and surgical outcomes following posterior lumbar interbody fusion plus pedicle screw fixation compared to midline lumbar fusion in patients aged ≥ 80 years with degenerative lumbar spine disease.
The study group comprised 68 patients aged ≥ 80 who underwent degenerative lumbar spinal surgery at our spine center between January 2011 and December 2020. Among them, 24 underwent posterior lumbar interbody fusion plus pedicle screw fixation, and the remaining 44 underwent midline lumbar fusion.
No significant intergroup differences were found in age, sex ratio, follow-up duration, or surgical level. The Visual Analog Scale for lower back pain was significantly different between the two groups at 7 days after surgery (P = 0.049). The Oswestry Disability Index was significantly different between the two groups at 7 days after surgery (P = 0.05). The estimated blood loss and operative time differed significantly (P < 0.05). There was a statistically significant difference in the postoperative morbidities between the groups (P = 0.049).
Although the clinical outcomes were not significantly different between the two groups, the perioperative morbidity was better in the midline lumbar fusion group. Therefore, we conclude that midline lumbar fusion is not inferior to posterior lumbar interbody fusion plus pedicle screw fixation if there is a need for fusion in elderly patients over octogenarian.
The Institutional Review Board of National Health Insurance Service Ilsan Hospital approved this study (2022-01-027), and the requirement of informed consent was waived due to the study's retrospective nature.
With the development of modern medicine, the human lifespan has dramatically increased, and due to the resulting aging population, spine surgeons are increasingly dealing with elderly patients suffering from degenerative lumbar spine diseases. [1–3]. If the degenerative lumbar spine disease symptoms do not improve, even the conservative treatment, spinal surgery should be considered.
Recently, minimally invasive spine surgery has become popular due to the development of surgical techniques, and endoscopic decompression and fusion are being performed from midline lumbar fusion (MIDLF) with cortical bone trajectory (CBT) to minimally invasive surgery-transforaminal lumbar interbody fusion (MIS-TLIF). Therefore, considering the advantages and disadvantages of surgery, it is essential to perform different surgical procedures according to appropriate indications.
Due to the increase in the elderly population and the development of geriatric medicine, the elderly patient group is classified as a separate patient group in research and clinical trials [4]. Comparative studies of MIDLF and conventional fusion surgery in elderly patients are rare. In addition, in the previous study, the clinical results were compared by separating the 60–70 years old group. However, we hypothesized that the difference in operation time and blood loss during spinal fusion could act as a prognostic factor in the elderly patient over 80.
Therefore, we aimed to retrospectively analyze the clinical and surgical outcomes following posterior lumbar interbody fusion plus pedicle screw fixation (PLIF c PS) and MIDLF in elderly patients (≥ 80 years) with degenerative lumbar spine disease.
The study group consisted of 68 patients over 80 who underwent degenerative lumbar surgery at our spine center between January 2011 and December 2020. A total of 2,583 patients were included in this study. Four spine surgeons participated in this study.
Clinical indications for surgery were radiating leg pain with or without low back pain (LBP) and/or neurogenic intermittent claudication (NIC) and resistance to conservative therapy. Magnetic resonance imaging was utilized to confirm the presence of central, lateral, or intervertebral foraminal stenosis. The choice of surgical method depends on the clinical findings of each surgeon and may yield better results depending on the symptoms, general condition, patient history, and degree of osteoporosis. If necessary, subjective judgment based on imaging or dual-energy X-ray absorptiometry assessed the degree of osteoporosis.
Common indications for fusion were relatively severe back pain with suspected mechanical back pain due to degeneration without apparent segmental instability and successful fusion expected due to acceptable bone marrow density, which was a common condition for fusion surgery. Patients who did not undergo fusion surgery, such as those with apparent segmental instability [5] or severe spondylolisthesis (grade II or greater), were excluded.
The study included 29 men and 39 women with a mean age of 81.6 years. The mean follow-up was 27.4 months (12–114 months). A total of 68 patients underwent surgery, of which 38 were at one level, and 30 were at two levels.
Preoperative status was assessed using the American Society of Anesthesiologists (ASA) classification [6], and clinical outcomes were assessed using the Visual Analog Scale (VAS) for LBP, VAS for lower extremity pain, and the Oswestry Disability Index (ODI) [7]. The VAS score was determined using a 0-to-10 scale, where a score of 0 means the patient is asymptomatic, and a score of 10 indicates the patient presents with the most severe symptom(s). VAS and ODI were scored one week after surgery and one year after surgery.
Surgical methods compared expected blood loss (EBL), operation time, and hospitalization period. Postoperative morbidity (e.g., neurologic deterioration, cerebrospinal fluid leak, wound infection, pneumonia, cardiac problems, dysuria, epidural hematoma, screw position abnormality, deep vein thrombosis) was assessed. In addition, the occurrence of reoperation and postoperative degenerative changes (e.g., relapse, instability, depression, screw loosening, nonunion, and ASD) have been documented. The rate of union was evaluated using the Bridwell grading system, computed tomography (CT), and radiographic findings at one year after surgery (Table 1).
| Grade | Description |
|---|---|
| I | Fused with remodeling and trabeculae present |
| II | Graft intact, not fully remodeled and incorporated, but no lucency present |
| III | Graft intact, potential lucency present at top and bottom of graft |
| IV | Fusion absent with collapse/resorption of graft |
All operations were performed in the prone position. After decompression, discectomy, and posterior lumbar interbody fusion, a traditional pedicle screw was used, followed by transpedicular screw fixation or cortical bone trajectory by cortical screw fixation according to the stenotic levels (Fig. 1).
SPSS version 26.0 (SPSS Inc., Chicago, IL, USA) was used to analyze all data. One-way analysis of variance was used depending on the characteristics of the variables being compared, and a post-hoc Bonferroni analysis was performed. Fisher’s exact test was used to analyze contingency tables, which showed a tabular representation of categorical data. The Freeman–Halton extension was applied, and the test yield probability value was defined as the probability of the observed array of cell frequencies plus the sum of the probabilities of all other cell-frequency arrays (such as would be consistent with the observed marginal totals) that are smaller than the probability of the observed array. Statistical significance was set at P values < 0.05.
We collected data from the hospital records, including sex, date of birth, type of surgery, medical history, body mass index, EBL, and date of death. The date of death was verified using records from the National Health Insurance Corporation. The Institutional Review Board of the National Health Insurance Service Ilsan Hospital approved this study (2022-01-027), and the requirement for informed consent was waived owing to the retrospective nature of the study.
Patients were divided into two groups according to the surgical method used. Of the 68 patients, 44 (64.7%) were assigned to the MIDLF group and 24 to the PLIF c PS group (35.3%). No significant between-group differences were found in age, sex ratio, follow-up period, or surgical level (Table 2).
| MIDLF (N = 44) | PLIF c PS (N = 24) | P-value | |
|---|---|---|---|
| Male:Female | 17:27 | 12:12 | 0.373 |
| Age (years) | 81.8 ± 1.9 | 81.0 ± 1.4 | 0.070 |
| Height (cm) | 155.4 ± 9.5 | 157.1 ± 9.5 | 0.493 |
| Weight (kg) | 58.8 ± 9.0 | 59.9 ± 9.6 | 0.638 |
| BMI (kg/m2) | 24.4 ± 3.4 | 24.3 ± 3.4 | 0.926 |
| ASA classification | 2.0 ± 0.5 | 2.0 ± 0.6 | 0.628 |
| CCI | 4.8 ± 1.0 | 4.8 ± 1.2 | 0.945 |
| Follow up duration (month) | 25.6 ± 21.1 | 30.6 ± 32.8 | 0.507 |
| Interbody fusion levels (mean) | 1.41 ± 0.5 | 1.5 ± 0.5 | 0.478 |
| PT (%) | 0.402 | ||
| < 20° | 15 (34.1%) | 8 (33.3%) | |
| > 20° but ≤ 30° | 16 (36.4%) | 12 (50.0%) | |
| > 30° | 13 (29.5%) | 4 (16.7%) | |
| PI–LL mismatch (%) | 0.550 | ||
| < 10° | 16 (36.4%) | 7 (29.2%) | |
| > 10° but ≤ 20° | 12 (27.3%) | 5 (20.8%) | |
| > 20° | 16 (36.4%) | 12 (50.0%) |
Data are presented as mean ± standard deviation or number (%)
PLIF + PS: posterior lumbar interbody fusion + pedicle screw fixation
MIDLF: midline lumbar fusion
BMI: body mass index
ASA: American Society of Anesthesiologists
CCI: Charlson comorbidity index
There was no significant difference between the ASA classification and the Charlson comorbidity index (CCI) [8]. Also, preoperative ODI and VAS scores for back pain and leg pain were not significantly different between the two groups.
VAS scores for LBP and leg pain sequentially decreased with follow-up in each group (Table 3).
| MIDLF (N = 44) | PLIF c PS (N = 24) | P-value | ||||
|---|---|---|---|---|---|---|
| VAS for LBP | Preop | 3.7 ± 3.0 | 3.7 ± 2.8 | 0.980 | ||
| POD 7 | 1.1 ± 1.5 | 2.2 ± 2.4 | 0.049* | |||
| Final f/u | 1.0 ± 1.8 | 0.8 ± 1.3 | 0.589 | |||
| VAS for leg pain | Preop | 5.5 ± 2.3 | 5.3 ± 2.2 | 0.746 | ||
| POD 7 | 1.9 ± 2.5 | 1.7 ± 2.3 | 0.745 | |||
| Final f/u | 1.1 ± 2.2 | 0.9 ± 1.6 | 0.702 | |||
| ODI | Preop | 52.3 ± 16.5 | 51.9 ± 16.3 | 0.916 | ||
| POD 7 | 15.2 ± 15.7 | 25.1 ± 21.1 | 0.050* | |||
| Final f/u | 14.1 ± 16.1 | 13.9 ± 15.4 | 0.952 | |||
| Bridwell Grade one fusion | 1 year f/u | 79% | 82% | 0.188 | ||
Data are presented as mean ± standard deviation or percentage
PLIF + PS: posterior lumbar interbody fusion + pedicle screw fixation
MIDLF: midline lumbar fusion
VAS: visual analog scale
ODI: Oswestry disability index
POD: postoperative day
*P < 0.05
In the MIDLF group, the VAS score for LBP had improved from 3.7 to 1.0. In the PLIF c PS group, the VAS score for LBP improved from 3.7 to 0.8. At the last visit, the VAS score for leg pain decreased from 5.5 to 1.1 in the MIDLF group and from 5.3 to 0.9 in the PLIF c PS group. VAS scores were significantly different in each group after one week of follow-up. The VAS score for LBP on postoperative day (POD) 7 was significantly different between groups (P = 0.049) (Fig. 2A).
Functional aspects were assessed using Oswestry Disability Index (ODI) scores. The ODI score decreased during follow-up. The ODI scores were significantly different in each group after one week of follow-up (P = 0.05) (Fig. 2B). The Bridwell fusion rate was not significantly different in each group after one year of follow-up.
For sagittal balances between the two groups, pelvic tilt, pelvic incidence, sacral slope, and PI-LL were compared before and after surgery, and there were no significant differences (Table 4).
| MIDLF (N = 44) | PLIF c PS (N = 24) | P-value | |||
|---|---|---|---|---|---|
| Pelvic tilt (°) | Preop | 24.4 ± 9.9 | 23.1 ± 9.3 | 0.605 | |
| POD 7 | 23.0 ± 8.8 | 20.2 ± 8.0 | 0.201 | ||
| Final f/u | 23.2 ± 8.5 | 22.3 ± 9.1 | 0.659 | ||
| Pelvic incidence (°) | Preop | 55.7 ± 13.6 | 53.9 ± 13.6 | 0.590 | |
| POD 7 | 54.4 ± 11.8 | 49.8 ± 22.4 | 0.274 | ||
| Final f/u | 55.3 ± 12.9 | 53.6 ± 12.2 | 0.592 | ||
| Sacral slope (°) | Preop | 31.3 ± 11.1 | 30.7 ± 12.0 | 0.841 | |
| POD 7 | 31.4 ± 10.0 | 29.6 ± 18.5 | 0.604 | ||
| Final f/u | 32.1 ± 10.3 | 31.3 ± 13.4 | 0.797 | ||
| PI–LL mismatch (°) | Preop | 16.0 ± 13.0 | 15.7 ± 11.4 | 0.923 | |
| POD 7 | 14.0 ± 12.1 | 11.2 ± 8.3 | 0.311 | ||
| Final f/u | 15.4 ± 12.5 | 12.8 ± 11.8 | 0.395 | ||
| Data are presented as mean ± standard deviation | |||||
| PLIF + PS: posterior lumbar interbody fusion + pedicle screw fixation | |||||
| MIDLF: midline lumbar fusion | |||||
| POD: postoperative day | |||||
| PI-LL: pelvic incidence – lumbar lordosis | |||||
EBL and operative time differed significantly between groups (Table 5).
| MIDLF (N = 44) | PLIF c PS (N = 24) | P-value | |
|---|---|---|---|
| Estimation of blood loss | 488.6 ± 570.3 | 908.5 ± 707.0 | 0.017* |
| Operation time (min) | 158.9 ± 46.3 | 253.1 ± 76.0 | 0.000*** |
| Hospital stay (day) | 14.8 ± 12.8 | 16.8 ± 7.8 | 0.505 |
Data are presented as mean ± standard deviation or number (%)
PLIF c PS: posterior lumbar interbody fusion + pedicle screw fixation
MIDLF: midline lumbar fusion
*P < 0.05
***P < 0.001
EBL and operation time increased in the order of PLIF, c PS, and MIDLF. EBL was significantly different between the MIDLF and PLIF c PS groups (P = 0.017). There was a significant difference in operation time between the MIDLF group and the PLIF c PS group (P = 0.000).
There was a statistically significant difference in postoperative morbidity (P = 0.049)(Table 6).
| MIDLF (N = 44) | PLIF c PS (N = 24) | P-value | |
|---|---|---|---|
| Postoperative complications | 1 (6.8%) | 4 (16.7%) | 0.049* |
| Pulmonary complications | 0 | 1 (4.2%) | |
| Cerebral infarction | 0 | 1 (4.2%) | |
| Angina | 0 | 1 (4.2%) | |
| Hematoma | 0 | 1 (4.2%) | |
| Infection | 1 (6.8%) | 0 | |
| Late complications | 4 (9.1%) | 4 (16.7%) | 0.439 |
| ASD | 3 (6.8%) | 1 (4.2%) | |
| Fusion or hardware failure | 1 (2.3%) | 3 (12.5%) |
Data are presented as mean ± standard deviation or number (%)
PLIF c PS: posterior lumbar interbody fusion + pedicle screw fixation
MIDLF: midline lumbar fusion
ASD: adjacent segmental degeneration
*P < 0.05
Postoperative morbidity was observed in 1 patient (6.8%) in the MIDLF group and 4 patients (16.7%) in the PLIF c PS group. An infectious intervertebral disc was observed in one patient in the MIDLF group. In the PLIF c PS group, angina (n = 1), pneumonia (n = 1), postoperative hematoma (n = 1), and cerebral infarction (n = 1) were reported.
There were no statistically significant differences in late complications between groups. As for morbidity, ASD occurred in 3 patients (6.8%) in the MIDLF group, of which 2 patients underwent revision surgery and 1 patient (2.3%) had screw loosening. In the PLIF c PS group, ASD occurred in 1 patient (4.2%), screw loosening occurred in 2 patients, and cage subsidence occurred in 1 patient.
This study investigated 68 consecutive cases of fusion surgery for degenerative lumbar spine disease in patients over 80 years of age and demonstrated favorable outcomes in this patient population. The goal of minimally invasive surgery (MIS) is to limit tissue damage. This is particularly advantageous for elderly patients where intraoperative EBL, postoperative mobilization, and wound healing have profound implications [9].
MIDLF is an MIS fusion technique consisting of posterior lumbar interbody arthroplasty and posterior instrumentation using CBT screws [10]. Insertion with a divergent trajectory is advantageous for small cuts and tight screw fixation. First, CBT does not require an incision in the facet joint for insertion [10, 11]. Second, a biomechanical study was performed and reported a higher insertion torque of CBT screws than conventional pedicle screws [12]. This can be particularly important when performing lumbar fusion in elderly patients with low bone density. In addition, CBT requires less EBL than conventional pedicle screw insertion and requires only an interarticular incision without an enlarged incision of the mammary gland. Thus, the operating time is reduced.
Increased blood loss during lumbar spinal fusion correlates with increased muscle damage and dissection boundaries [13]. Another theoretical benefit of reducing blood loss is a reduced risk of blood transfusion and other complications in patients with comorbidities who are more sensitive to low postoperative hemoglobin levels. Since fusion may have a difference in operation time compared to decompression alone, we believe that side effects such as cerebral infarction and pulmonary complications are more likely to occur. Similarly, this study showed that lengthy surgery leads to a greater amount of blood loss, increasing the risk of postoperative complications and delaying functional pain relief.
The difference in EBL was still significant. This was expected since traditional PS implantation requires extensive exposure of the facet joints. We believe that the difference in the screw insertion method of fusion is the reason for the difference between the groups in the ODI and VAS scores of low back pain on the 7th day after fusion.
Complications were divided into postoperative complications and late complications, and there was a significant difference in late complications between the two groups. According to a study by Kobayashi et al., the risk factors for major complications (cerebral infarction, pulmonary embolism, coronary heart disease, and angina pectoris) after degenerative lumbar spine surgery were preoperative movement disorders, operation time, EBL, and instrument-assisted fusion in patients over 90 years of age [14]. In this study, postoperative pulmonary complications were found in the PLIF c PS group.
In addition, in the case of PLIF c PS, patients with cerebral infarction and postoperative hematoma required rehabilitation treatment due to motor weakness. Therefore, for elderly patients requiring fusion, selecting MIDLF, which has advantages in terms of EBL and operative time, would be a way to reduce major complications. Previous studies have also found that the amount of bleeding and operation time are related to the occurrence of complications [15].
In previous studies, the authors suggested performing decompression or fusion as needed without significant differences in complications [16, 17]. However, very old people over 80 years of age may have biological differences. Oldridge et al. reported an overall mortality rate of 0.5% in 34,418 Medicare patients who underwent lumbar spine surgery. For patients older than 80, the mortality rate of spinal fusion was greater than 10%. They concluded that the 80–85 years age group had the highest risk of a significant increase in morbidity and mortality for spinal fusion [18]. Therefore, MIDLF with less bleeding is advantageous when considering complications.
Average ASA and CCI values tended to increase with age, which was confirmed to increase the possibility of perioperative complications [19]. However, in this study, the MIDLF group had relatively few surgical scars, low blood loss, and short operation time, reducing the risk of complications and securing sufficient fixation. No statistically significant differences were observed in complications according to ASA and CCI values. We believe that a significant difference can be found if the number of cases is high.
The limitations of this study are: First, there are limitations in retrospective observation and analysis of a 10-year study conducted at a single institution. In addition, the indications for surgery in the two study groups were not exactly the same, and the preoperative status of patients differed between groups. Considering these limitations, we performed a statistical comparison of the basal conditions of the two groups before the operation and found no significant differences. Two spine surgeons participated in this study, and differences in surgical technique may have influenced the results. Additionally, due to the small number of cases, it is difficult to compare the results for each level, so the average of all levels of surgery was compared. The lack of long-term clinical follow-up is a final limitation, as the risk of recurrence is usually assessed over 5 years postoperatively in older patients [20]. In the case of octogenarians, from 80 to 85 years of age, natural death can occur. Considering these points, further studies may provide evidence that supports improved patient survival after MIDLF or PLIF c PS.
Older age did not increase morbidity associated with spinal fusion surgery and did not decrease patient satisfaction or return to activity compared to previous studies. Clinical outcomes were not significantly different between the MIDLF and PLIF c PS groups, but postoperative morbidity and late complications were better in the MIDLF group. MIDLF is recommended rather than PLIF c PS when lumbar interbody fusion is required in octogenarians or older who have a high risk of postoperative complications.
ASA: American Society of Anesthesiologists; ASD: adjacent segment degeneration; BMI: body mass index; CBT: cortical bone trajectory; CCI: Charlson Comorbidity Index; EBL: estimated blood loss; LBP: low back pain; MIDLF: midline lumbar fusion; MIS: minimally invasive surgery; MIS-TLIF: minimally invasive surgery-transforaminal lumbar interbody fusion; NIC: neurogenic intermittent claudication; ODI: Oswestry Disability Index; PLIF c PS: posterior lumbar interbody fusion plus pedicle screw fixation; VAS: Visual Analog Scale;
Ethics approval and consent to participate: The Institutional Review Board of National Health Insurance Service Ilsan Hospital approved this study (2022-01-027), and the requirement of informed consent was waived by the IRB staff Insoon Kim due to the retrospective nature of the study. This study was conducted in compliance with the IRB research guidelines of the National Health Insurance Service Ilsan Hospital.
Consent for publication: Not applicable.
Availability of data and materials: Data and materials may be provided on request via Giwuk Jang’s email: [email protected].
Competing interests: The authors declare that they have no competing interests.
Funding: The authors declare no sources of funding.
Authors’ contributions: Study concept: GJ and SR; Study design: GJ and SR; Data acquisition: HZ, SL, and JP; Quality control of data and algorithms: GJ and SR; Data analysis and interpretation: GJ and SR; Manuscript preparation: GJ; Manuscript editing: GJ and SR; Manuscript review: GJ and SR; All the authors have read and approved the final version of the manuscript.
Acknowledgments: Not applicable.
Authors’ information: 1Department of Neurosurgery, Spine and Spinal Cord Institute, Gangnam Severance Spine Hospital, Seoul, Republic of Korea; 2Department of Neurosurgery, National Health Insurance Service Ilsan Hospital, Goyang, Republic of Korea;