Abstract
Purpose
To evaluate whether incorporating an anterior stage into adult spinal deformity (ASD) correction surgery with apical segment interbody fusion can reduce surgical invasiveness and enhance radiologic correction compared to a posterior-only approach.
Materials and Methods
A retrospective review was conducted using a prospectively collected database from a single institution. A total of 150 ASD patients who underwent surgery between January 2014 and May 2021 and were followed for at least 2 years were included. Among them, 108 underwent a posterior-only approach (P group), and 42 underwent a combined anterior-posterior approach (AP group). Radiologic outcomes, bone fusion rates, clinical outcomes, and complications were assessed at baseline, immediately postoperatively, and at 2 years postoperatively.
Results
The AP group received an average of 2.2±0.6 levels of interbody fusion at the deformity apex. Compared to the P group, the AP group had significantly lower Schwab grade of posterior osteotomy, reduced total blood loss, and shorter posterior operative time. The AP group demonstrated a significantly greater coronal correction of the major Cobb angle. Regarding sagittal balance, the AP group also achieved more harmonious alignment across most parameters throughout the 2-year follow-up, although the differences were not statistically significant. Clinical outcomes, complication rates, and fusion rates were comparable between the two groups.
Conclusion
Adding an anterior stage of apical segment interbody fusion to spinal deformity correction can achieve reduced surgical invasiveness and better spinal alignment without increasing the risk of major complications.
Keywords: Kyphosis, scoliosis, spinal fusion
Graphical Abstract
INTRODUCTION
Adult spinal deformity (ASD) can have a devastating effect on the quality of life of patients with chronic and intractable back pain, radiating pain, or a stooping figure, often leading to inevitable surgical correction.1,2 Traditionally, ASD has been treated posteriorly, which could directly decompress the neural compartment and effectively realign the spinal deformity. However, the posterior-only approach often requires invasive epidural space manipulation for interbody fusion and high-grade osteotomy to achieve ideal alignment. This can result in excessive intraoperative blood loss and serious medical complications, particularly in older patients.3,4
Since its first report, the use of the anterior approach in ASD correction surgery has gained considerable popularity due to several advantages, such as direct anterior release, the use of larger and more lordotic cages, and the provision of larger fusion beds.1,5,6 However, several disadvantages include psoas muscle violation, lumbosacral plexus injury, and various complications related to the manipulation of abdominal contents.7,8 Also, as it requires two surgical stages, it can increase hospital stay, total operative time, and hospital costs.
Various studies have compared the outcomes of combined anterior-posterior and posterior-only approaches for ASD.9,10,11,12,13,14,15,16 Haddad, et al.9 proposed that combined approaches achieved more harmonious correction of sagittal deformity. However, Theologis, et al.10 reported that while the addition of multilevel lateral interbody fusion may offer better correction of spinal deformity, those advantages come at the expense of higher rates of major complications, greater blood loss, and longer hospital stays. There is still debate regarding which approach is more favorable, and studies with larger sample sizes remain limited. Our hypothesis is that if the anterior approach is effectively combined at the apical segment, high-grade osteotomy and blood loss can be minimized while achieving superior spinal alignment. Here, we present a retrospective comparative analysis with a minimum 2-year follow-up comparing the anterior-posterior combined approach and the posterior-only approach.
MATERIALS AND METHODS
This retrospective analysis was conducted on a cohort of patients diagnosed with ASD, each with a minimum follow-up period of 2 years, treated exclusively at a single medical institution. This study was approved by our Gangnam Severance Institutional Review Board (IRB Number 3-2023-0392), which waived the requirement for informed consent.
Patients with ASD who underwent surgical correction between January 2014 and May 2021 were retrospectively collected. The inclusion criteria were as follows: age >18 years, coronal Cobb angle >20°, sagittal vertical axis (SVA) >5 cm, pelvic tilt >25°, or thoracic kyphosis >60°. For patients who received the combined approach, anterior-stage procedures were performed using either oblique lumbar interbody fusion (OLIF) or lateral lumbar interbody fusion (LLIF) around the level of the lumbar apex. These patients subsequently underwent a posterior approach for pedicle screw fixation, and some patients additionally underwent posterior interbody fusion (Fig. 1). There was usually a 7-day interval between the two stages of surgery. In all patients, demineralized bone matrix, allograft, and autograft were routinely used for posterolateral fusion or interbody fusion. Iliac crest autograft was harvested and used in patients requiring iliac screw fixation. Selection of the anterior–posterior combined approach versus the posterior-only approach was based on surgeon preference.
Fig. 1. Representative case of an ASD patient who received an anterior-posterior combined approach surgery. (A and B) A 65-year-old female presented with severe coronal imbalance at the thoracolumbar junction. (C) We first performed oblique interbody fusion at the L2/3/4 level during the anterior stage. (D and E) Seven days later, we performed the posterior stage, which included T9-to-iliac screw fixation and additional transforaminal interbody fusion posteriorly at L4/5/S1.
Baseline demographic factors such as age, height, weight, American Society of Anesthesiologists score, body mass index (BMI), and bone mineral density (BMD) were measured. Surgery-related factors included the total number of fixated vertebrae, the number of interbody-fused vertebrae, osteotomy grade (Schwab classification), total operative time (from incision to closure), total estimated blood loss, transfusion amount, and total length of hospital stay. Various medical- and surgery-related complications, such as screw loosening, proximal junctional kyphosis, rod fracture, and surgical site infection, that occurred after surgery were recorded.
Standing radiographs were obtained before, immediately after, and 2 years after the operation. Immediate postoperative standing radiography was defined as the first standing radiograph obtained after surgery. Various radiological parameters and Global Alignment and Proportion (GAP) scores were measured and analyzed. Postoperative CT was taken between 1 and 2 years after the operation and analyzed for bone fusion grade. CT grading was performed for each level of the operated intervertebral segment as shown in Supplementary Table 1 (only online). Clinical outcomes were assessed using the visual analog scale, Oswestry Disability Index, 36-Item Short Form Health Survey, and Scoliosis Research Society-22, which were collected before surgery and at 2 years postoperative.
Statistical analyses were performed using the Python programming language (version 3.12.2; Python Software Foundation, https://www.python.org) and SAS (version 9.4; SAS Inc., Cary, NC, USA). Continuous variables are presented as means with standard deviations, and categorical variables are presented as counts and percentages. For comparisons of baseline demographic and clinical characteristics between groups, the Mann–Whitney U test was used for continuous variables, whereas Fisher’s exact test or the chi-square test was used for categorical variables, as appropriate. To appropriately account for repeated measurements obtained from the same individuals across multiple time points, longitudinal outcomes were analyzed using linear mixed-effects models (LMMs), with patient identity treated as a random effect. Fixed effects included group, time point, and their interaction. Baseline values were included as covariates when appropriate. Variables are presented as estimated marginal means with standard errors derived from the LMMs. The interaction term was used to assess differences in longitudinal changes between groups. A two-sided p-value<0.05 was considered statistically significant.
RESULTS
A total of 298 patients with ASD were initially enrolled. Among them, 86 patients with less than 2 years of follow-up were excluded. Patients with missing standing radiographs before and after surgery (n=62) were excluded. Among the 150 patients with more than 2 years of follow-up and appropriate radiographs, 108 underwent the posterior-only approach (P group), and 42 underwent the combined anterior-to-posterior approach (AP group). The average follow-up period was 42.1±26.7 months for the AP group and 48.2±27.5 months for the P group. A diagram of the data collection process is shown in Fig. 2.
Fig. 2. Illustrative flowchart of the data collection process. ASD, adult spinal deformity.
The basic demographic data and surgery-related factors are listed in Table 1. There were no significant differences in baseline demographic characteristics, including age, height, weight, BMI, or BMD, between the two groups. Although the total number of fixated vertebrae was not significantly different between the two groups (8.9 vs. 9.0, p=0.705), the AP group had a significantly larger number of interbody fusion (3.2 vs. 1.3, p<0.001) than the P group. The AP group required a less invasive osteotomy grade compared with the P group (1.7 vs. 2.3, p=0.001). The total surgery time was significantly longer in the AP group (445.7 min vs. 412.3 min, p=0.045). However, when only the posterior stage was considered, the AP group required significantly less operative time than the P group (301.4 min vs. 412.3 min, p<0.001). The total blood loss was significantly lower in the AP group (1629.0 cc vs. 2202.8 cc, p=0.049), and the length of hospital stay was significantly longer in the AP group (30.0 days vs. 24.8 days, p=0.013).
Table 1. Comparison of Basic Demographic and Surgical Data between the Two Surgical Groups (Combined Anterior-Posterior vs. Posterior-Only).
| Demographic variable | Total (n=150) | Combined (n=42) | Posterior (n=108) | p | |
|---|---|---|---|---|---|
| Follow-up period (month) | 44.6±29.1 | 42.1±26.7 | 48.2±27.5 | 0.124 | |
| Age (yr) | 69.0±5.1 | 69.1±5.5 | 69.0±5.0 | 0.678 | |
| Sex, female | 135 (90.0) | 38 (90.5) | 97 (89.8) | >0.999 | |
| Height (cm) | 154.2±6.8 | 155.3±7.1 | 153.7±6.7 | 0.307 | |
| Weight (kg) | 59.5±9.8 | 59.5±9.4 | 59.5±10.0 | 0.833 | |
| BMI (kg/m2) | 25.0±3.5 | 24.7±3.7 | 25.1±3.5 | 0.589 | |
| BMD (T-score) | -2.0±1.0 | -1.9±0.8 | -2.0±1.0 | 0.395 | |
| ASA classification | 2.4±0.7 | 2.3±0.7 | 2.4±0.7 | 0.397 | |
| Number of fixated vertebrae | 9.0±2.3 | 8.9±2.5 | 9.0±2.2 | 0.705 | |
| Number of interbody fusions | 1.8±1.5 | 3.2±1.1 | 1.3±1.3 | <0.001 | |
| Number of anterior interbody fusions | 2.2±0.6 | - | |||
| Osteotomy grade | 2.1±1.0 | 1.7±0.8 | 2.3±1.0 | 0.001 | |
| Total surgical time (min) | 421.6±111.3 | 445.7±111.8 | 412.3±110.2 | 0.045 | |
| Anterior surgical time | 117.3±49.0 | - | |||
| Posterior surgical time | 301.4±111.5 | 412.3±110.2 | <0.001 | ||
| Total blood loss (cc) | 2042.1±1271.7 | 1629.0±760.7 | 2202.8±1391.9 | 0.049 | |
| Hospital stay (days) | 26.2±20.5 | 30.0±26.7 | 24.8±17.5 | 0.013 | |
BMI, body mass index; BMD, bone mineral density; ASA, American Society of Anesthesiologists.
Continuous variables are presented as mean±SD, and categorical values are presented as n (%).
Radiological outcomes across all time points are summarized in Table 2. Regarding coronal correction, despite a larger baseline major Cobb angle in the AP group (21.0°±0.8 vs. 14.5°±0.5), the AP group demonstrated a significantly greater change over time (interaction p<0.001). The major Cobb angle decreased to 3.1°±0.8 in the AP group and 6.4°±0.5 in the P group immediately postoperatively and was maintained at 3.8°±0.8 and 7.1°±0.5, respectively, at the 2-year follow-up. No significant difference in longitudinal change was observed for C7PL to CSVL between the two groups (interaction p=0.219). Regarding sagittal alignment, baseline parameters were generally comparable between groups. Across most sagittal parameters, including global tilt, C7SVA, T1 pelvic angle, pelvic tilt, lumbar lordosis, and PI–LL mismatch, both groups showed postoperative improvement followed by partial loss of correction over time. At the 2-year follow-up, compared with the P group, the AP group demonstrated more harmonious values across most parameters, including global tilt (29.1°±2.0 vs. 34.3°±1.2), C7SVA (45.0±8.3 mm vs. 61.9±5.2 mm), T1 pelvic angle (22.3°±1.6 vs. 26.8°±1.0), pelvic tilt (25.0°±1.4 vs. 28.2°±0.9), PI–LL mismatch (19.5°±2.6 vs. 25.4°±1.6), lumbar lordosis (34.2°±2.2 vs. 29.3°±1.4), and total GAP score (8.8±0.5 vs. 10.0±0.3). However, no significant difference in longitudinal changes was observed between the two groups (all interaction p>0.05). A graphical illustration of temporal changes in the key radiologic parameters between the two groups is presented in Fig. 3.
Table 2. Comparison of Radiologic Outcomes Over Time (Baseline, Immediate Postoperative, and 2-Year Follow-Up) between the Two Surgical Groups (Combined Anterior-Posterior vs. Posterior-Only).
| Combined (n=42) | Posterior (n=108) | Interaction p* | |||
|---|---|---|---|---|---|
| Coronal correction | |||||
| Major Cobb angle (°) | <0.001 | ||||
| Baseline | 21.0±0.8 | 14.5±0.5 | |||
| Immediate post-op | 3.1±0.8 | 6.4±0.5 | |||
| 2-year post-op | 3.8±0.8 | 7.1±0.5 | |||
| Coronal balance (C7PL to CSVL) (mm) | 0.219 | ||||
| Baseline | 24.7±2.8 | 19.3±1.8 | |||
| Immediate post-op | 21.4±1.7 | 13.6±1.0 | |||
| 2-year post-op | 18.2±1.8 | 14.4±1.1 | |||
| Sagittal correction | |||||
| Global tilt (°) | 0.605 | ||||
| Baseline | 42.5±2.4 | 45.6±1.5 | |||
| Immediate postop | 21.5±1.7 | 27.5±1.1 | |||
| 2-year postop | 29.1±2.0 | 34.3±1.2 | |||
| Sagittal balance (C7SVA) (mm) | 0.531 | ||||
| Baseline | 86.9±10.8 | 105.7±6.7 | |||
| Immediate post-op | 23.7±7.2 | 32.4±4.5 | |||
| 2-year post-op | 45.0±8.3 | 61.9±5.2 | |||
| T1 pelvic angle (°) | 0.807 | ||||
| Baseline | 33.3±2.0 | 36.3±1.3 | |||
| Immediate postop | 16.1±1.3 | 20.5±0.8 | |||
| 2-year postop | 22.3±1.6 | 26.8±1.0 | |||
| Pelvic tilt (°) | 0.123 | ||||
| Baseline | 32.7±1.7 | 33.2±1.0 | |||
| Immediate post-op | 20.1±1.3 | 24.1±0.8 | |||
| 2-year post-op | 25.0±1.4 | 28.2±0.9 | |||
| Pelvic incidence (°) | 0.829 | ||||
| Baseline | 50.0±1.6 | 51.0±1.0 | |||
| Immediate post-op | 47.7±1.5 | 49.4±0.9 | |||
| 2-year post-op | 49.0±1.5 | 50.4±1.0 | |||
| Lordosis L1-S1 (°) | 0.143 | ||||
| Baseline | 8.1±2.9 | 8.5±1.8 | |||
| Immediate post-op | 35.8±2.2 | 34.3±1.4 | |||
| 2-year post-op | 34.2±2.2 | 29.3±1.4 | |||
| PI-LL mismatch (°) | 0.745 | ||||
| Baseline | 41.9±2.9 | 45.1±1.8 | |||
| Immediate post-op | 11.3±2.0 | 17.2±1.3 | |||
| 2-year post-op | 19.5±2.6 | 25.4±1.6 | |||
| Total GAP score | 0.051 | ||||
| Baseline | 11.6±0.3 | 11.6±0.2 | |||
| Immediate post-op | 7.2±0.6 | 8.7±0.4 | |||
| 2-year post-op | 8.8±0.5 | 10.0±0.3 | |||
PI-LL, pelvic incidence-lumbar lordosis; GAP, Global Alignment and Proportion.
Values are presented as mean±SD. Longitudinal outcomes were analyzed using linear mixed-effects models, and p-values for the interaction between group (AP vs. P) and time (baseline, immediate postoperative, and 2-year follow-up) are presented.
*Baseline values were included as covariates when comparing coronal major Cobb angle.
Fig. 3. Graphical illustration of changes in radiologic parameters over time comparing the combined anterior-posterior (AP) group and the posterior-only (P) group. The AP group demonstrated a larger major coronal Cobb angle at baseline, followed by a more significant reduction in the postoperative period. Regarding sagittal parameters, the AP group achieved better postoperative alignment in global tilt, T1 pelvic angle, lumbar lordosis, PI-LL mismatch, and lower GAP scores compared with the P group, but without statistical significance. PI-LL, pelvic incidence-lumbar lordosis; GAP, Global Alignment and Proportion.
There were no significant differences in clinical outcomes between the two groups (Table 3). Complication rates are presented in Table 4. The AP group showed lower rates of rod fracture and screw loosening (11.9% vs. 19.4%), medical complications (4.8% vs. 12.0%), and wound infection (7.1% vs. 18.5%); however, these differences were not statistically significant. There was no significant difference in the average fusion grade or the number of segments with high-grade fusion between the two groups (Table 5). However, when the operated segments were divided into three regions (upper, middle, and lower) and analyzed separately, the upper segment showed a superior fusion grade in the AP group (1.3 vs. 1.0, p=0.016; 1.1 vs. 0.8, p=0.027).
Table 3. Comparison of Clinical Outcomes Over Time (Baseline, and 2-Year Postoperative Follow-Up) between the Two Surgical Groups (Combined Anterior-Posterior vs. Posterior-Only).
| Combined (n=42) | Posterior (n=108) | Interaction p | ||
|---|---|---|---|---|
| VAS_Back | 0.718 | |||
| Baseline | 8.0±0.4 | 7.2±0.2 | ||
| 2-year post-op | 4.7±0.4 | 4.0±0.3 | ||
| VAS_Leg | 0.661 | |||
| Baseline | 6.9±0.5 | 6.6±0.3 | ||
| 2-year post-op | 4.5±0.9 | 4.7±0.5 | ||
| ODI | 0.447 | |||
| Baseline | 61.3±2.8 | 61.6±1.8 | ||
| 2-year post-op | 46.8±3.7 | 50.4±2.3 | ||
| SRS-22 subtotal | 0.548 | |||
| Baseline | 2.3±0.1 | 2.2±0.1 | ||
| 2-year post-op | 3.0±0.5 | 3.2±0.3 | ||
| SF-36_PCS | 0.601 | |||
| Baseline | 22.9±3.0 | 21.9±1.9 | ||
| 2-year post-op | 36.4±3.4 | 37.8±2.1 | ||
| SF-36_MCS | 0.523 | |||
| Baseline | 36.5±3.5 | 32.8±2.2 | ||
| 2-year post-op | 49.5±3.7 | 42.7±2.3 | ||
VAS, visual analogue scale; ODI, Oswestry Disability Index; SRS, Scoliosis Research Society; SF-36, 36-Item Short Form Health Survey; PCS, Physical Component Summary; MCS, Mental Component Summary.
Values are presented as mean±SD. Longitudinal outcomes were analyzed using linear mixed-effects models, and p-values for the interaction between group (AP vs. P) and time (baseline and 2-year follow-up) are presented.
Table 4. Comparison of Perioperative Complications between the Two Surgical Groups (Combined Anterior-Posterior vs. Posterior-Only).
| Combined (n=42) | Posterior (n=108) | p | ||
|---|---|---|---|---|
| Revision | 10 (23.8) | 25 (23.1) | >0.999 | |
| Readmission | 8 (19.0) | 19 (17.6) | 0.758 | |
| Mechanical complication | 14 (33.3) | 41 (38.0) | 0.734 | |
| PJK and ASD | 9 (21.4) | 24 (22.2) | >0.999 | |
| Rod fracture and screw loosening | 5 (11.9) | 21 (19.4) | 0.392 | |
| Screw or cage malpositioning | 3 (7.1) | 7 (6.5) | 0.386 | |
| Dural tear and hematoma | 2 (4.8) | 4 (3.7) | 0.673 | |
| Medical complication | 2 (4.8) | 13 (12.0) | 0.236 | |
| Wound infection | 3 (7.1) | 20 (18.5) | 0.138 | |
| Adjacent structure injury | 2 (4.8) | 4 (3.7) | 0.673 | |
| Neurologic deficit | 1 (2.4) | 7 (6.5) | 0.443 | |
PJK, proximal junctional kyphosis; ASD, adjacent segment degeneration.
Values are presented as n (%).
Table 5. Comparison of Fusion Rates Based on Postoperative CT between the Two Surgical Groups (Combined Anterior-Posterior vs. Posterior-Only).
| Combined (n=42) | Posterior (n=108) | p | ||
|---|---|---|---|---|
| Grade 2* fusion segment number | 2.1±1.7 | 1.6±1.2 | 0.351 | |
| Average fusion grade | 1.2±0.4 | 1.1±0.4 | 0.814 | |
| Highest fusion grade | ||||
| Upper segment | 1.3±0.6 | 1.0±0.5 | 0.016 | |
| Mid segment | 1.4±0.7 | 1.6±0.5 | 0.452 | |
| Lower segment | 1.6±0.5 | 1.4±0.7 | 0.319 | |
| Average fusion grade | ||||
| Upper segment | 1.1±0.6 | 0.8±0.5 | 0.027 | |
| Mid segment | 1.1±0.6 | 1.3±0.5 | 0.146 | |
| Lower segment | 1.3±0.5 | 1.2±0.6 | 0.685 | |
Values are presented as mean±SD.
*Graded as illustrated in Supplementary Table 1 (only online).
DISCUSSION
In this study, we demonstrated that the AP group achieved more harmonious spinal alignment with less surgical invasiveness by incorporating additional interbody fusion during the anterior stage at an average of approximately two levels (2.2±0.6) (Table 1). Despite the requirement for a two-stage procedure, the AP combined approach mitigated surgical invasiveness by reducing blood loss (1629.0 cc vs. 2202.8 cc, p=0.049) (Table 1) and requiring less surgical time during the posterior stage (301.4 min vs. 412.3 min, p<0.001) (Table 1). Furthermore, the AP group required a lower osteotomy grade (1.7 vs. 2.3, p=0.001) (Table 1) while achieving a significantly higher number of interbody fusion segments (3.2 vs. 1.3, p<0.001) (Table 1). The harmonious spinopelvic alignment was observed to be maintained throughout a minimum follow-up period of 2 years (Table 2). Thus, despite the longer hospital stay (30.0 days vs. 24.8 days, p=0.013) (Table 1), the AP combined approach may offer a viable surgical strategy for achieving stable correction with reduced posterior-stage burden, particularly in elderly or frail patients with severe spinal deformities.
The importance of restoring the physiological apex of lumbar lordosis and its effect on achieving global harmonious alignment is emphasized in many other studies.17,18 Since the apex in degenerative lumbar scoliosis is usually located between L1 and L4, performing anterior interbody fusion around these levels could effectively restore lumbar lordosis at the physiological apex. Many previous studies have provided strong evidence for the efficacy of anterior surgery in restoring sagittal alignment by providing lumbar lordosis at the physiologic apex using larger lordotic cages.19,20,21 In the AP group, interbody fusion during the anterior stage was primarily performed around the lumbar apex, which was most commonly located at the L2/3/4 level (Supplementary Table 2, only online). However, whether the combined approach is more advantageous than the posterior-only approach for correcting sagittal imbalance remains controversial in the literature. In a systematic meta-analysis, Zhu, et al.22 reported that multilevel OLIF achieved sagittal imbalance correction comparable to that of multilevel posterior osteotomies. Some studies have reported that LLIF does not result in significant correction of sagittal imbalance.23,24 In our study, sagittal correction parameters did not differ significantly between the AP and P groups across various measures, including PI–LL mismatch, global tilt, pelvic tilt, T1 pelvic angle, and GAP scores.
While baseline demographic and radiologic parameters were generally similar between the two groups, the AP group showed greater coronal imbalance at baseline compared to the P group (21.0° vs. 14.5°). This implies that surgeons tend to perform staged operations when patients initially present with greater coronal imbalance. Previous studies have demonstrated that the anterior approach can effectively restore coronal imbalance, which may explain why many surgeons additionally perform anterior-stage procedures in patients with severe scoliosis.10,22,25,26,27 Despite these baseline differences, longitudinal analysis adjusted for baseline imbalance demonstrated significantly greater coronal correction over time in the AP group compared with the P group. The effectiveness of the anterior approach in restoring coronal imbalance has been demonstrated in multiple previous studies,10,22,25,26,27 and our findings are consistent with those reports.
The lower surgical invasiveness of the AP combined approach was demonstrated by reduced blood loss and shorter surgical time for the posterior stage. Most blood loss during spinal surgery occurs during epidural space manipulation.28 As the AP group required less manipulation of the epidural space with less posterior interbody fusion and less invasive bone osteotomies, it is natural that the AP group showed less blood loss and required less surgical time during the posterior stage. The anterior stage generally does not induce significant blood loss, unless there is severe injury to the major vessels.29,30,31 Less blood loss and less surgical time for each stage of the surgery are crucial for the outcome and complication rates of the patients. It is well-known that longer surgery time required for each general anesthesia is potentially more harmful to the patients.32,33 Kim, et al.33 reported that an operation duration of 5 hours or more in lumbar fusion surgery was associated with an increased risk of various complications such as reoperation, surgical site infection, and sepsis/septic shock. Hersey, et al.34 also reported that longer operative time was associated with a greater risk of numerous complications for patients aged 65 and older undergoing posterior lumbar fusion. Thus, combined with significantly less blood loss and shorter surgery time required in the posterior stage of deformity correction surgery, a staged operation may contribute to less stress related to general anesthesia and operation, especially in older patients.
It is noteworthy that the patients in the AP group in our study did not show a higher prevalence of any other major complications, as reported in many other studies.7,8,9,10 Rather, it presented with relatively less complications in terms of medical complication (4.8% vs. 12.0%) or wound infection (7.1% vs. 18.5%), although not statistically significant. Other than the fact that the AP approach achieved a less invasive technique with decreased blood loss and less surgical time for the posterior stage as mentioned above, this should also be because we had mostly performed the OLIF technique in the anterior stage. The trans- or lateral-psoas approaches in the lower lumbar area are reported to have a higher risk for lumbar plexus injury.7,8,35 Since most of the interbody fusion techniques of the anterior stage in our study were performed in an oblique fashion, which passes anteriorly to the psoas muscle rather than penetrating through it, these complications could have been avoided. We also rarely performed interbody fusion higher than the L1/2 level during the anterior stage. When performing interbody fusion higher than the L1-2 level anteriorly, the kidneys and main vessels, such as the renal vein or artery, are located nearby, and injury to these structures can induce major complications.36
The total in-hospital stay was significantly longer in the AP group (30.0 vs. 24.8, p=0.013). This is as expected, as there was usually a 7-day interval between the two stages, and it is the major disadvantage of the AP combined approach that could increase the medical cost for the patients. Many previous studies report the downside of the AP combined approach for deformity patients by increasing hospital stay and medical costs.15 However, the authors think that the safety of the patients and effective correction of the deformed spine should be considered prior to reducing the medical costs.
Although there are no clearly established guidelines on how to accurately assess the fusion state of multi-level deformity correction, the CT-based analysis of the fusion rate in our study indicated that there was no overall significant difference between the two groups. Previous studies reported that combined anteroposterior fusion can provide higher fusion rates.37,38 Our study also showed that the AP group had a higher average grade of fusion, although this difference was not statistically significant. Interestingly, the upper-third segment showed a significantly higher fusion rate in the AP group; however, further studies are needed to accurately evaluate its impact on the fusion rate.
Our study has some limitations. First, the data were retrospectively collected, and various biases could not be ruled out. Also, since the surgeons generally tend to select the combined approach for patients with greater coronal imbalance and for those requiring multiple interbody fusion procedures, the surgeon’s preference for selection of surgical technique should have influenced the results. Additionally, the heterogeneous nature of the patients may have affected the accuracy of our results. However, a large cohort of patients (n=150) was included, and an adequate amount of data was collected over a sufficient period; therefore, many of the biases that could affect radiological and clinical outcomes could have been minimized. In addition, the similarities between the basic demographic characteristics (Table 1) indicate that the heterogeneity between the two groups was not clinically significant. All patients were recruited from a single institution so that variations in the surgical procedures between each institution could be minimized. Further prospective and long-term follow-up studies are required to accurately assess the impact of the combined approach on ASD correction.
In conclusion, a combination of lumbar interbody fusion using the anterior approach for approximately two levels at the apex can achieve satisfactory radiologic outcomes, while minimizing surgery-related complications. To achieve harmonic realignment, we might not need a multi-level anterior approach interbody fusion that could increase anterior-related complications, or a posterior-only approach using high-grade osteotomy that could result in vigorous surgical invasiveness. Further prospective studies on fusion rate and clinical outcomes are needed.
Footnotes
The authors have no potential conflicts of interest to disclose.
- Conceptualization: Jae Keun Oh and Kyung Hyun Kim.
- Data curation: Hyun Jun Jang, Bong Ju Moon, Jeong Yoon Park, Yoon Ha, Sung Uk Kuh, Dong Kyu Chin, Keun Su Kim, Jae Keun Oh, and Kyung Hyun Kim.
- Formal analysis: Dongkyu Kim.
- Methodology: Dongkyu Kim.
- Supervision: Kyung Hyun Kim.
- Visualization: Dongkyu Kim.
- Writing—original draft: Dongkyu Kim.
- Writing—review & editing: Dongkyu Kim and Kyung Hyun Kim.
- Approval of final manuscript: all authors.
SUPPLEMENTARY MATERIALS
Classification system for posterolateral and/or interbody fusion
Location and type of interbody fusion during the anterior stage in the AP group
References
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Classification system for posterolateral and/or interbody fusion
Location and type of interbody fusion during the anterior stage in the AP group