Staged Lateral Lumbar Interbody Fusion Targeting Driver and Compensatory Structural Segments for Adult Degenerative Scoliosis: A Novel Strategy and Early Outcomes

ABSTRACT

Objective

Traditional treatments for adult degenerative scoliosis (ADS) often rely on highly morbid long‐segment fusions. While lateral lumbar interbody fusion (LLIF) provides a minimally invasive alternative, consensus on precise surgical targets is lacking. We propose a novel strategy targeting “driver” and “compensatory structural” segments to optimize surgical outcomes.

Methods

A retrospective review of 104 ADS patients (2023–2024) compared this targeted LLIF strategy (n = 64) to traditional posterior surgery (n = 40). The LLIF approach utilized staged procedures focusing exclusively on segments driving the primary deformity and rigid compensatory segments. We evaluated radiographic parameters and clinical outcomes (VAS, ODI, EQ‐5D).

Results

The LLIF group achieved significant deformity correction, with the coronal major Cobb angle decreasing from 24.73° to 10.76°, alongside marked improvements in sagittal alignment. Patients exhibited progressive self‐correction of coronal balance over the 1‐year follow‐up. Clinical scores (VAS, ODI, EQ‐5D) improved significantly. Compared to the traditional group, targeted LLIF resulted in significantly shorter operative times and less blood loss, with comparable overall complication rates (16.0% vs. 20.0%), although traditional surgery achieved superior immediate radiographic correction.

Conclusion

Targeting driver and compensatory structural segments via LLIF is an effective, minimally invasive strategy for ADS. It offers substantial deformity correction, symptom relief, and progressive postoperative self‐correction while significantly reducing surgical trauma compared to traditional long‐segment fusions.

Targeting driver and structural vertebrae via LLIF is an effective, minimally invasive strategy for ADS. It offers substantial deformity correction, symptom relief, and progressive postoperative self‐correction while significantly reducing surgical trauma compared to traditional long‐segment fusions.

1. Introduction

Adult degenerative scoliosis (ADS) is a progressive spinal deformity (Cobb angle > 10°) characterized by asymmetric disc and facet joint degeneration in skeletally mature individuals [1]. With a reported prevalence of 68% in adults over 50 years, ADS frequently leads to vertebral rotation, lateral listhesis, and spinal stenosis, resulting in debilitating back pain, radiculopathy, and neurogenic claudication [2].

While conservative management remains first‐line, surgical intervention is indicated for severe or progressive cases [3]. Traditional posterior long‐segment fusion [4], though historically the gold standard, is associated with significant morbidity, including muscle detachment, proximal junctional kyphosis (PJK), and high reoperation rates [4]. Classification systems (e.g., Aebi, Schwab, Lenke‐Silva, and Berjano) aim to standardize treatment by correlating radiographic parameters with surgical strategies [2], yet persistent controversies exist regarding optimal fusion levels and decompression extent [5].

The advent of lateral lumbar interbody fusion (LLIF) has transformed ADS management by combining minimally invasive access with robust deformity correction [6, 7]. The LLIF technique utilizes a retroperitoneal approach that preserves posterior spinal elements while providing three key advantages: (1) insertion of large interbody cages that achieve indirect decompression and improve both coronal and sagittal alignment; (2) targeted treatment of pathological discs with significantly reduced blood loss (38%–45% less compared to posterior approaches); and (3) superior clinical outcomes including shorter hospital stays (mean 4.2 days) and better lumbosacral fractional curve correction (71.3% vs. 52.7% with PLIF) [3, 6, 7].

Despite these advantages, consensus is lacking on precise surgical targets. We propose a novel strategy focusing on driver segments and compensatory structural segments to optimize outcomes. This study evaluates the efficacy of this segments‐targeted surgical strategy through radiographic and clinical metrics.

The aims of this study were: (i) to propose a staged surgical decision‐making framework targeting the critical intervertebral segments in degenerative scoliosis, namely the “driver segments” and “compensatory structural segments”; (ii) to validate the effectiveness of the staged surgical strategy based on the identification of driver and compensatory structural segments for the treatment of adult degenerative scoliosis; and (iii) to investigate the potential advantages of this framework compared with traditional posterior direct decompression and corrective surgery.

2. Materials and Methods

2.1. Demographics and Study Design

We retrospectively reviewed the clinical data of 104 patients with adult degenerative scoliosis (ADS) who underwent surgical treatment at the Chinese PLA General Hospital between January 2023 and December 2024. According to the surgical strategy, patients were divided into the targeted staged LLIF group (n = 64) and the traditional posterior approach surgery (TPAS) group (n = 40). The LLIF group consisted of 20 males and 44 females, with a mean age of 65.20 ± 6.80 years, whereas the TPAS group consisted of 25 males and 15 females, with a mean age of 65.84 ± 2.40 years.

The TPAS group comprised patients treated with conventional posterior surgery during the same study period. These patients fulfilled the same general diagnostic, age, radiographic, and data‐completeness criteria as those in the LLIF group, but underwent posterior direct decompression, deformity correction, and instrumented fusion rather than the staged LLIF‐based strategy targeting driver and compensatory structural segments. The TPAS cohort served as a contemporaneous comparison group for evaluating differences in perioperative characteristics, radiographic correction, clinical outcomes, and complications between the two surgical strategies.

2.2. Inclusion and Exclusion Criteria

2.2.1. Inclusion Criteria

Patients were included if they met the following conditions: (1) age > 45 years; (2) diagnosis of ADS with a Cobb angle ≥ 10° confirmed by preoperative imaging at our institution; (3) underwent multilevel lateral lumbar interbody fusion (LLIF) or traditional posterior approach surgery at our hospital; and (4) surgery was performed by a single experienced surgeon.

2.2.2. Exclusion Criteria

Patients were excluded if they presented with any of the following: (1) concomitant idiopathic scoliosis, congenital or secondary vertebral structural deformities identified on imaging; (2) history of neurological diseases, ankylosing spondylitis, spinal tumors, spinal tuberculosis, spinal trauma, or previous spinal surgery; (3) prior knee or hip arthroplasty; (4) preoperative leg length discrepancy > 20 mm; or (5) incomplete radiographic data (e.g., standing full‐spine anteroposterior and lateral X‐rays) or unclear vertebral exposure preventing accurate measurement.

2.3. Surgical Strategy: Focus on “Driver” and “Compensatory Structural” Segments

Based on the robust three‐dimensional corrective capacity of the lateral approach—addressing coronal deformity correction, sagittal lordosis restoration, and axial derotation—we established a comprehensive LLIF decision‐making system focused on driver segments and compensatory structural segments (Figure 1).

FIGURE 1.

LLIF surgical decision‐making flowchart based on driver and compensatory structural segments.

First, upon admission, patients underwent symptom evaluation, physical examination, and radiographic assessment. Exclusion criteria were strictly applied to filter out cases with concomitant AIS or congenital/secondary vertebral structural deformities, positional symptoms unrelieved by bed rest, or involvement of driver/compensatory structural segments extending proximal to the T12–L1 level.

Subsequently, standing full‐spine radiographs were utilized to define the major curve, compensatory curves, driver segments, and compensatory structural segments. The specific measurement protocol is detailed below:

A surgical strategy emphasizing both “driver” and “compensatory structural” segments was developed, leveraging the three‐dimensional correction capabilities of lateral lumbar interbody fusion (LLIF) in the coronal and sagittal planes, as well as its axial derotation effect. The following definitions were applied: Major Curve: The spinal segment on full‐length standing AP radiographs that is either responsible for coronal imbalance (C7 plumb line deviation ≥ 2 cm) or, if no imbalance exists, the one with the greatest Cobb angle. Compensatory Curve: A curvature in the opposite direction adjacent to the primary curve's proximal or distal end. It is typically a short‐segment fractional curve (e.g., lumbosacral curve) which helps maintain global spinal balance. Driver Segments: The intervertebral level(s) constituting the epicenter of severe degeneration and segmental wedging within the major curve that initiates and propagates degenerative lumbar scoliosis, characterized by: (1) disc wedging > 5°, (2) concave‐sided osteophytic overgrowth, (3) lateral translation > 3 mm, or (4) vertebral rotation > Nash‐Moe Grade II. Compensatory Structural Segments: The most degenerated and rigid level within the compensatory curve (often lumbosacral), characterized by: (1) > 50% disc asymmetry (often unilateral collapse), (2) severe concave osteophytes nearing bony bridging, and (3) rigid > 50% disc wedging on bending films (Figure 2).

FIGURE 2.

(a) This case presented with rightward coronal decompensation, with the L3–5 curve identified as the major curve responsible for the coronal imbalance. (b) The L3–5 segment was the major curveand T12–L3 the compensatory curve. In the major curve (blue dashed line), L3 showed rightward lateral listhesis (green dashed line), L4 leftward axial rotation, and concave‐sided lateral osteophytes at L4–5 (yellow dashed arc); thus, L3–4 and L4–5 were designated driver segments. In the compensatory curve(red dashed line), bridging osteophytes were present at L1–2 and L2–3(yellow dashed arc), with rightward rotation of L2 and > 50% asymmetric disc collapse at L1–2 (black dashed line); thus, L1–2 and L2–3 were designated compensatory structural segments.

2.4. Surgical Technique

A staged surgical protocol was adopted. The first stage involved lateral lumbar interbody fusion (LLIF) at the driver and compensatory structural segments. The second stage consisted of percutaneous, navigation‐assisted pedicle screw fixation. If neurological symptoms persisted, an open posterior approach with pedicle screw instrumentation and selective decompression was added. The posterior procedure was scheduled 3–5 days after LLIF to allow assessment of neurological recovery following indirect decompression.

Stage 1 (LLIF): The procedure was performed under direct vision with the patient secured in the lateral decubitus position. The operating table was flexed to widen the intercostal–iliac crest corridor and tension the lateral soft tissues. A transpsoas approach was performed from the concavity of the curve. Bridging osteophytes and portions of the annulus fibrosus were resected using Cobb and pituitary rongeurs. Sequential dilators were then advanced along varying trajectories to bluntly release the contracted psoas and annular fibers contralateral to the target disc space. A polyetheretherketone (PEEK) interbody cage (Shanghai Sanyou Medical Device Co. Ltd.), measuring 18 mm in anterior–posterior diameter with 8° of lordosis, was inserted at each level. All levels were grafted with a mixture of allograft and bone morphogenetic protein (BMP).

Stage 2 (Posterior Fixation): All patients underwent supplemental posterior fixation and fusion via either percutaneous or mini‐open techniques. Those with persistent radicular symptoms or intermittent claudication underwent targeted decompressive laminectomy and foraminal decompression. When the L5–S1 level was involved, a posterior transforaminal lumbar interbody fusion (TLIF) was performed using local autologous bone graft.

2.5. Outcome Measures

Radiographic parameters assessed included: Global Alignment: Major and compensatory Cobb angles, coronal sacral vertical line (CSVL), lumbar lordosis (LL), pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), sagittal vertical axis (SVA), and coronal balance distance (CBD). Clinical outcomes were evaluated using the Visual analog scale (VAS), Oswestry Disability Index (ODI), and EQ‐5D scores.

2.6. Statistical Analysis

Data were analyzed and visualized using R version 4.3.3. The normality of continuous variables was assessed using the Shapiro–Wilk test. Parametrically distributed variables are presented as mean ± standard deviation and compared using independent samples t‐tests, with equality of variances verified by Levene's test. Categorical variables were compared using Pearson's chi‐squared test or Fisher's exact test for small cell frequencies. Missing longitudinal radiographic data were imputed using the last observation carried forward (LOCF) method. A two‐tailed p‐value of less than 0.05 was considered statistically significant (Tables S1–S3).

3. Results

3.1. Efficacy of LLIF Surgery Based on Driver Segments and Compensatory Structural Segments

3.1.1. Demographics and Baseline Characteristics

A total of 104 patients with adult degenerative scoliosis were included in this study, consisting of 64 patients who underwent the targeted staged LLIF strategy and 40 patients who underwent traditional posterior approach surgery (TPAS).

The mean age was 65.20 ± 6.80 years in the LLIF group and 65.84 ± 2.40 years in the TPAS group. No significant differences were observed in age, BMI, or preoperative clinical outcomes between the two groups.

The preoperative standing whole‐spine radiographs demonstrated comparable deformity characteristics between groups. In the LLIF group, the mean major curve Cobb angle was 24.73° ± 8.42°, CSVL was 24.76 ± 12.54 mm, lumbar lordosis (LL) was 27.84° ± 9.06°, pelvic tilt (PT) was 26.27° ± 7.16°, pelvic incidence (PI) was 51.37° ± 10.16°, and sagittal vertical axis (SVA) was 61.47 ± 38.16 mm.

Similarly, the TPAS group showed comparable preoperative deformity parameters, including Cobb angle (26.61° ± 9.06°), CSVL (26.18 ± 13.42 mm), LL (26.92° ± 10.24°), PT (27.04° ± 6.83°), PI (52.08° ± 9.74°), and SVA (67.72 ± 42.53 mm).

No significant differences were identified between groups regarding baseline radiographic parameters or patient‐reported outcomes, indicating satisfactory comparability between the two cohorts (Table 1).

TABLE 1.

Comparison of preoperative baseline characteristics between the LLIF and traditional posterior approach surgery groups.

	LLIF (n = 64)	TPAS (n = 40)	p
Age, years	65.20 ± 6.80	65.84 ± 2.40	0.876
Sex			0.003
Male, N (%)	20 (32%)	25 (62%)
Female, N (%)	44 (68%)	15 (38%)
BMI, kg/m2	26.50 ± 3.2	26.98 ± 1.57	0.460
Involved segments of driver
L1–2	2	—
L2–3	15	—
L3–4	48	—
L4–5	45	—
L5–S1	4	—
Standing whole‐spine radiograph
Coronal major curve Cobb angle, (Cobb, °)	24.73 ± 8.42	26.61 ± 9.06	0.266
Coronal balance distance (CBD, mm)	24.76 ± 12.54	26.18 ± 13.42	0.186
Lumbar lordosis, (LL, °)	27.84 ± 9.06	26.92 ± 10.24	0.561
Pelvic tilt, (PT, °)	26.27 ± 7.16	27.04 ± 6.83	0.662
Sacral slope, (SS, °)	25.18 ± 6.94	24.56 ± 6.47	0.141
Pelvic incidence, (PI, °)	51.37 ± 10.16	52.08 ± 9.74	0.297
Sagittal vertical axis, (SVA, mm)	61.47 ± 38.16	67.72 ± 42.53	0.060
Visual analogue scale (VAS)	7.08 ± 1.18	7.32 ± 1.12	0.301
Oswestry Disability Index (ODI)	54.08 ± 8.64	55.76 ± 9.18	0.356
EuroQol 5‐dimension 5‐level questionnaire (EQ‐5D‐5L)	0.46 ± 0.10	0.45 ± 0.11	0.642

Note: Bold values represent significant results.

3.1.2. Distribution of Driver Segments

According to the involved segments of driving, driver segments were predominantly located at L3–4 (n = 48) and L4–5 (n = 45). Additionally, four cases involved L5–S1. Of these, two patients underwent staged surgery for L5–S1, while the remaining two declined further intervention.

3.1.3. Radiographic Outcomes

Following the staged targeted LLIF procedure, significant improvements were observed in both coronal and sagittal alignment parameters. The mean major curve Cobb angle significantly decreased from 24.73° ± 8.42° preoperatively to 10.76° ± 5.06° postoperatively, with a mean correction of 13.97° ± 6.18° (p < 0.001). CSVL improved from 24.76 ± 12.54 mm to 12.43 ± 8.17 mm, representing a mean correction of 12.33 ± 7.72 mm (p < 0.001). Sagittal alignment was also significantly improved. Lumbar lordosis increased from 27.84° ± 9.06° to 38.57° ± 8.46°, with a mean improvement of 10.73° ± 7.14° (p < 0.001). Pelvic compensation improved after surgery, with PT decreasing by 3.53° ± 5.06° and SS increasing by 5.18° ± 5.76° (both p < 0.001). The SVA decreased from 61.47 ± 38.16 mm preoperatively to 39.74 ± 25.48 mm postoperatively, corresponding to an average improvement of 21.73 ± 20.36 mm (p < 0.001). These findings demonstrated that targeted treatment of driver and compensatory structural segments using LLIF effectively improved both coronal and sagittal spinal alignment (Table 2, Figures 3, 4, 5).

TABLE 2.

Immediate postoperative radiographic outcomes of deformity correction of LLIF group.

	Preoperation	Postoperation	Correction	p
Coronal major curve Cobb angle, (Cobb, °)	24.73 ± 8.42	10.76 ± 5.06	13.97 ± 6.18	< 0.001
Coronal balance distance (CBD, mm)	24.76 ± 12.54	12.43 ± 8.17	12.33 ± 7.72	< 0.001
Lumbar lordosis, (LL, °)	27.84 ± 9.06	38.57 ± 8.46	10.73 ± 7.14	< 0.001
Pelvic tilt, (PT, °)	26.27 ± 7.16	22.74 ± 6.08	3.53 ± 5.06	< 0.001
Sacral slope, (SS, °)	25.18 ± 6.94	30.36 ± 7.16	5.18 ± 5.76	< 0.001
Pelvic incidence, (PI, °)	51.37 ± 10.16	51.02 ± 10.04	0.35 ± 1.18	0.1451
Sagittal vertical axis, (SVA, mm)	61.47 ± 38.16	39.74 ± 25.48	21.73 ± 20.36	< 0.001

Note: Bold values represent significant results.

FIGURE 3.

A 68‐year‐old female patient was admitted to the hospital with a chief complaint of “lower back pain for 5 years.” The admission diagnosis was “degenerative scoliosis.” (A) Preoperative anteroposterior whole‐spine radiograph: The main curve Cobb angle was 18°, with the driver segment identified as L2–L5. Coronal imbalance was measured at 8 mm. (B) Immediate postoperative anteroposterior whole‐spine radiograph: The main curve Cobb angle was corrected to 10°. Coronal imbalance was 25 mm. (C) Anteroposterior whole‐spine radiograph at 6 months postoperatively: The main curve Cobb angle remained at 10°. Coronal imbalance was 26 mm. (D) Anteroposterior whole‐spine radiograph at 12 months postoperatively: The main curve Cobb angle was maintained at 10°. Coronal imbalance improved to 8 mm.

FIGURE 4.

A 62‐year‐old female patient was admitted to the hospital with a chief complaint of “lower back pain for 20 years accompanied by left lower limb pain for 2 years.” The admission diagnosis was “degenerative scoliosis with lumbar spinal stenosis.” (A) Preoperative anteroposterior whole‐spine radiograph: The main curve Cobb angle was 59°, with the driver segment identified as L1–L5. Coronal imbalance was measured at 8 mm. (B) Immediate postoperative anteroposterior whole‐spine radiograph: The main curve Cobb angle was corrected to 26°. Coronal imbalance was −11 mm. (C) Anteroposterior whole‐spine radiograph at 6 months postoperatively: The main curve Cobb angle was 25°. Coronal imbalance was −5 mm. (D) Anteroposterior whole‐spine radiograph at 12 months postoperatively: The main curve Cobb angle was 28°. Coronal imbalance improved to 3 mm.

FIGURE 5.

A 62‐year‐old female patient was admitted with a chief complaint of “lower back pain for 2 years accompanied by intermittent claudication for 6 months.” The admission diagnosis was “degenerative scoliosis with lumbar spinal stenosis.” (A) Preoperative anteroposterior whole‐spine radiograph: The main curve Cobb angle was 24°, with the driver segment identified as L1–L5. Coronal imbalance was measured at 23 mm. (B) Immediate postoperative anteroposterior whole‐spine radiograph: The main curve Cobb angle was corrected to 8°. Coronal imbalance was 20 mm. (C) Anteroposterior whole‐spine radiograph at 6 months postoperatively: The main curve Cobb angle was 11°. Coronal imbalance was 4 mm. (D) Anteroposterior whole‐spine radiograph at 12 months postoperatively: The main curve Cobb angle was 8°. Coronal imbalance was 18 mm.

3.1.4. Follow‐Up Analysis of Coronal Balance

The changes in coronal balance were evaluated over a 1‐year follow‐up period. Standing whole‐spine anteroposterior radiographs were obtained at four time points: preoperatively, immediately postoperatively, 6 months postoperatively, and 1 year postoperatively. The coronal balance distance (CBD) values at each time point were plotted, and fitted curves were generated to illustrate the temporal trend of coronal alignment restoration. The fitted curves demonstrated a progressive reduction in CBD throughout the one‐year follow‐up period, suggesting continuous improvement in coronal balance after surgery. Although several patients showed limited correction or transient worsening of CBD immediately after surgery, CBD showed an overall decreasing trend during follow‐up (Figure 6).

FIGURE 6.

The coronal balance distance (CBD) was measured at four time points.

3.1.5. Clinical Outcomes and Quality of Life

Patients in the LLIF group demonstrated significant improvements in pain relief, functional recovery, and health‐related quality of life. The mean VAS score decreased from 7.08 ± 1.18 preoperatively to 2.04 ± 1.09 postoperatively (p < 0.001). The ODI score improved from 54.08% ± 8.64% to 24.63% ± 10.14% (p < 0.001). Similarly, the EQ‐5D‐5L index increased from 0.46 ± 0.10 to 0.75 ± 0.12 (p < 0.001). These results indicate that the targeted LLIF strategy provided substantial symptom relief and functional improvement in patients with adult degenerative scoliosis (Table 3).

TABLE 3.

Immediate postoperative functional improvement of LLIF group.

	Preoperation	Postoperation	p
Visual analogue scale (VAS)	7.08 ± 1.18	2.04 ± 1.09	< 0.001
Oswestry Disability Index (ODI)	54.08 ± 8.64	24.63 ± 10.14	< 0.001
EuroQol 5‐dimension 5‐level questionnaire (EQ‐5D‐5L)	0.46 ± 0.10	0.75 ± 0.12	< 0.001

Note: Bold values represent significant results.

3.2. Comparison of Efficacy Between LLIF Surgery Based on Driver Segments and Compensatory Structural Segments and Traditional Posterior Approach Surgery

The mean operative time was 278.00 ± 68.00 min in the LLIF group compared with 432.00 ± 108.00 min in the TPAS group (p < 0.001). Estimated blood loss was also significantly reduced in the LLIF group (382.00 ± 158.00 mL vs. 1358.00 ± 548.00 mL, p < 0.001). Regarding radiographic correction, both groups achieved significant postoperative improvement; however, the magnitude of correction differed between procedures. The TPAS group achieved greater improvements in major curve Cobb angle compared with LLIF (18.43° ± 7.02° vs. 13.97° ± 6.18°, p = 0.001). Similarly, greater improvements were observed in CBD correction (16.84 ± 8.31 mm vs. 12.33 ± 7.72 mm, p = 0.008) and lumbar lordosis restoration (16.26° ± 8.25° vs. 10.73° ± 7.14°, p < 0.001). The TPAS group also demonstrated greater improvements in PT and SS, suggesting stronger sagittal reconstruction capability (p < 0.01). Interestingly. The TPAS group also showed a greater reduction in SVA than the LLIF group (35.56 ± 24.18 mm vs. 21.73 ± 20.36 mm, p = 0.003). Despite differences in radiographic correction, both surgical strategies achieved comparable clinical improvements. The improvements in VAS were 5.04 ± 1.37 points in the LLIF group and 5.48 ± 1.28 points in the TPAS group (p = 0.140). ODI improvement was 29.45 ± 11.16 points versus 33.76 ± 12.42 points (p = 0.082), while EQ‐5D improvement was 0.29 ± 0.13 versus 0.34 ± 0.15 (p = 0.083). No significant difference was observed in overall complication rates between groups, with complications occurring in 10 patients (15.6%) in the LLIF group and eight patients (20.0%) in the TPAS group (p = 0.572) (Table 4).

TABLE 4.

Comparison of clinical outcomes between the LLIF and conventional surgery groups.

	LLIF (n = 64)	TPAS (n = 40)	p
Operation time, min	278.00 ± 68.00	432.00 ± 108.00	< 0.001
Estimated blood loss, mL	382.00 ± 158.00	1358.00 ± 548.00	< 0.001
Coronal major curve Cobb angle, (Cobb, °)	13.97 ± 6.18	18.43 ± 7.02	0.001
Coronal balance distance (CBD, mm)	12.33 ± 7.72	16.84 ± 8.31	0.008
Lumbar lordosis, (LL, °)	10.73 ± 7.14	16.26 ± 8.25	< 0.001
Pelvic tilt, (PT, °)	3.53 ± 5.06	6.72 ± 5.84	0.006
Sacral slope, (SS, °)	5.18 ± 5.76	8.64 ± 6.32	0.007
Pelvic incidence, (PI, °)	0.35 ± 1.18	1.02 ± 0.2	< 0.001
Sagittal vertical axis, (SVA, mm)	21.73 ± 20.36	35.56 ± 24.18	0.003
Visual analogue scale (VAS)	5.04 ± 1.37	5.48 ± 1.28	0.140
Oswestry Disability Index (ODI)	29.45 ± 11.16	33.76 ± 12.42	0.082
EuroQol 5‐dimension 5‐level questionnaire (EQ‐5D‐5L)	0.29 ± 0.13	0.34 ± 0.15	0.083
Complications			0.572
No, N (%)	54 (84%)	32 (80%)
Yes, N (%)	10 (16%)	8 (20%)

Note: Bold values represent significant results.

4. Discussion

In this study, we developed a staged surgical decision‐making framework for adult degenerative scoliosis by identifying the functional roles of key intervertebral segments, namely the “driver” and “compensatory structural segments.” The results indicated that patients treated according to this segment‐oriented strategy achieved significant improvements in spinal alignment parameters and clinical outcomes. Furthermore, compared with traditional posterior direct decompression and corrective surgery, this approach demonstrated comparable or favorable therapeutic efficacy with potentially reduced surgical burden. These findings provide preliminary evidence supporting a more individualized surgical strategy that considers the heterogeneous biomechanical contributions of different spinal segments in adult degenerative scoliosis.

4.1. Current Treatment Landscape of Adult Degenerative Scoliosis and the Clinical Implications of a Staged Surgical Strategy Based on Driver Segments and Compensatory Structural Segments

The conventional management of degenerative lumbar scoliosis has predominantly involved posterior corrective osteotomy, decompression, and long‐segment instrumented fusion to address spinal deformity and neurological symptoms. Numerous classification systems and surgical strategies are founded on this approach. However, the frequent necessity for long‐segment fusion to comprehensively correct deformity and relieve neural compression results in prolonged operative times, increased blood loss, and significantly higher complication rates. Furthermore, long‐term complications such as proximal junctional kyphosis (PJK), pseudarthrosis, and implant failure occur at rates as high as 30% to 40%, severely impacting functional recovery and quality of life [8, 9, 10, 11]. Additionally, patients with degenerative scoliosis are typically elderly, often presenting with osteoporosis and multiple medical comorbidities. The substantial trauma associated with traditional open long‐segment procedures, coupled with a slow recovery, elevates the risks of cardiovascular and cerebrovascular events [8]. Minimally invasive alternatives also present significant limitations: decompression alone may accelerate curve progression, with reported rates ranging from 23% to 37%, while short‐segment fusion carries risks of inadequate correction (residual Cobb angle > 15°) and adjacent segment degeneration, with a 28% reoperation rate within 5 years.

Lateral lumbar interbody fusion (LLIF) has evolved from a limited procedure for degenerative conditions to a pivotal technique for spinal deformity correction via multilevel interbody fusion. LLIF offers several technical advantages, including powerful segmental coronal correction and high fusion rates, attributable to its ability to release ligamentous structures and utilize large‐footprint cages. Moreover, compared to posterior osteotomy and fusion, LLIF is associated with markedly reduced intraoperative blood loss and less surgical trauma. The lateral approach involves a small incision, minimizes soft‐tissue injury, and preserves the anterior and posterior longitudinal ligaments, contributing to spinal stability and preventing cage migration. The large‐footprint cages provide support on the apophyseal ring, enhance anterior column support, indirectly enlarge the neural foramen, and facilitate nerve root decompression without the need for direct canal intrusion. Multiple studies have reported fusion rates of 88% to 96% with LLIF, along with significant improvements in both coronal and sagittal alignment, particularly in patients with degenerative lumbar scoliosis and lateral listhesis [12, 13].

Several studies have proposed innovations in the principles and surgical options for adult spinal deformity (ASD) based on the advantages of LLIF and other minimally invasive techniques. Among these, the MISDEF (Minimally Invasive Spinal Deformity Surgery) classification is one of the most systematic. It categorizes patients into four types (I–IV) based on spinopelvic parameters—such as sagittal vertical axis (SVA), pelvic tilt (PT), pelvic incidence‐lumbar lordosis mismatch (PI‐LL), and Cobb angle—to guide the choice between minimally invasive and open procedures. However, despite being updated to MISDEF 2, the algorithm remains ambiguous in intermediate cases, potentially leading to overtreatment. For instance, in patients with moderate PI‐LL mismatch (10° to 20°) combined with multilevel degeneration or listhesis, the algorithm does not explicitly recommend between limited fusion and long‐segment correction. Studies indicate that such patients undergoing full correction according to Type II criteria have a 2.6‐fold higher complication rate compared to those receiving limited surgery (43.7% vs. 16.7%). There is also a risk of overusing long‐segment fusion: patients classified as MISDEF 2 Type IV require fusion of more than five levels, yet the 5‐year mechanical complication rate remains high (30% to 40%), with disproportionally limited improvement in quality of life, particularly in patients over 75 years of age, who show only 15% to 20% improvement in ODI scores [14, 15].

4.2. Efficacy of LLIF Surgery Based on Driver Segments and Compensatory Structural Segments

Therefore, building on the core capability of LLIF to directly address and correct disc pathology, we propose the concepts of the driver and compensatory structural segments. Our surgical strategy focuses precisely on these elements, employing a staged approach to achieve the goals of traditional posterior surgery—correction, decompression, and stabilization. Results demonstrate a postoperative Cobb angle correction rate of 56.4% when both driver and compensatory structural segments are addressed, underscoring their critical role in deformity correction. By thoroughly addressing degenerative discs in the driver segments and reconstructing anterior column height, LLIF may directly correct the “hinge effect” responsible for curve progression. This aligns with the findings of Ohtori et al., who reported that LLIF significantly improves coronal imbalance (average correction 65% to 75%) by restoring disc height and lumbar lordosis [16]. Addressing the compensatory structural segments (e.g., L3/4 or L4/5) releases stiff segments and restores spinal flexibility, enabling spontaneous compensatory correction. This strategy resembles the “selective fusion” concept proposed by Schwab et al. [17], moreover, our preoperative precise targeting further reduces the number of fused segments (average 2.4 levels). We also emphasize the importance of coronal balance: in cases of truncal imbalance, the curve contributing most to the imbalance is identified as the major curve and prioritized for correction. This principle is supported by our findings, which show a 49.8% improvement in coronal balance. Furthermore, continued improvement in coronal balance was observed during subsequent follow‐up. For patients classified as MISDEF2 Grade III–IV, the traditional surgical strategy requires long‐segment posterior fixation extending to the pelvis, with the aim of achieving more optimal correction and simultaneously preventing the long‐term progression of coronal imbalance. It should be noted that in our cohort, seven patients demonstrated a postoperative coronal balance distance greater than the preoperative value, which was largely attributable to L5 tilt/obliquity, and a subset of patients exhibited residual undercorrection of the coronal deformity. Nevertheless, because the lateral approach minimizes disruption of the posterior musculoligamentous complex and paraspinal musculature relative to conventional posterior surgery, a substantial degree of the spine's intrinsic self‐balancing capacity is preserved. Consistent with this, progressive spontaneous correction of coronal alignment was observed over the course of the 1‐year follow‐up period in the majority of patients. However, longer‐term follow‐up is required to confirm the durability of this self‐correcting trend and to clarify its relationship with L5 tilt/obliquity in patients with residual imbalance.

The strategy of addressing both driver and compensatory structural segments, facilitated by LLIF, significantly enhances radiographic outcomes while leveraging minimally invasive and biomechanical advantages to reduce perioperative and long‐term complications. Compared to traditional posterior surgery, the LLIF approach utilizes a retroperitoneal natural corridor that preserves posterior elements, avoiding direct intraspinal nerve manipulation (reducing early neurological injury to 1.9% vs. 7.2% for posterior procedures) [18]. Incision length is reduced by approximately 60% (averaging 3 to 4 cm), resulting in a surgical site infection rate below 0.8% [19]. When treating the driver segments, precise placement of anterior support not only restores disc height but also, due to the cage's larger footprint (30% to 40% increase in endplate contact area), significantly improves fusion rates when combined with posterior instrumentation (98.1% at 1 year vs. 89.5% for posterior surgery) [20]. Furthermore, load distribution reduces endplate pressure (biomechanical studies show a 55% decrease), effectively preventing cage subsidence (3.8% in our series vs. 9.6% for traditional ALIF) [21].

4.3. Comparison of Efficacy Between LLIF Surgery Based on Driver Segments and Compensatory Structural Segments and Traditional Posterior Approach Surgery

To further validate the advantages of LLIF surgery based on driver segments and compensatory structural segments for treating ADS, we compared the surgical outcomes of the LLIF group with those of the traditional posterior approach surgery groups. To ensure comparability of the data, we compared the preoperative profiles of the two groups. The results showed no significant differences in baseline characteristics or preoperative deformity severity between the groups, indicating that the preoperative data were basically balanced and comparable [22, 23, 24, 25].

Comparison of efficacy showed that the LLIF group had significant advantages in operative time and estimated blood loss, which aligned with our expectations and previous literature reports. In contrast, the traditional posterior approach surgery groups demonstrated more significant immediate postoperative deformity correction and functional improvement, attributable to the capability for direct posterior decompression and osteotomy.

There are some key distinctions between our decision‐making framework and traditional classification, such as Lenke‐Silva Classification.

The Lenke‐Silva classification stratifies patients by global spinopelvic parameters—Cobb angle, listhesis, lumbar kyphosis, and sagittal balance—matched to symptom severity. Because the causative segment is not anatomically defined within a given treatment level, decision‐making in intermediate cases remains ambiguous and prone to overtreatment, with fusion extent tending to expand alongside treatment level rather than target the actual pathology. Our strategy instead relies on segment‐specific radiographic criteria that are readily quantifiable—disc wedging, lateral translation, and rotation—each independently associated with curve progression in degenerative lumbar scoliosis. Anchoring level selection to these criteria aligns fusion extent with the anatomical driver of deformity, yielding an average of only 2.4 fused levels, markedly fewer than the long‐segment constructs typical of higher Lenke‐Silva levels.

Lenke‐Silva Classification relies chiefly on global sagittal parameters and symptoms, with limited characterization of local pathology such as disc wedging, osteophyte formation, and vertebral rotation—despite evidence that degenerative scoliosis progresses through a self‐perpetuating cycle of asymmetric disc/facet degeneration and segmental load imbalance, driven principally by apical wedging, rotation, and translation. The driver/compensatory structural segments concept is defined directly from this mechanism: driver segments capture the levels initiating and propagating the deformity, while compensatory structural segments capture the rigid levels anchoring the compensatory curve, consistent with data linking asymmetric apical degeneration to deformity severity.

This locally causative‐segment‐oriented philosophy shares conceptual common ground with the earlier classification proposed by Aebi and Berjano based on the distribution of degenerated segments (apical vs. nonapical regions)—which likewise advocates that apex‐limited disease can be managed with selective fusion, that fusion must span the apex only when apical pathology is present, and that only extensive multisegment disease or globally imbalanced curves warrant more extensive correction. In this sense, the driver/structural segment concept can be viewed as a quantitative extension of this “locally causative‐segment‐oriented” line of thinking and represents the first framework to systematically integrate it with the three‐dimensional corrective capability of LLIF and a staged surgical workflow.

4.4. Limitations

This study was a single‐center retrospective analysis, which carries inherent biases. Additionally, the sample size was relatively small, resulting in limited statistical power, and the concepts of driver Segments and compensatory structural Segments have not been validated by large‐scale clinical samples. The follow‐up duration was short; further long‐term follow‐up is required to determine the incidence of long‐term complications and the status of coronal imbalance after limited correction, specifically whether further progression or spontaneous correction occurs.

5. Conclusion

This study proposes a minimally invasive surgical strategy using LLIF based on driver segments and compensatory structural segments to correct adult degenerative scoliosis. Early results demonstrate satisfactory immediate postoperative correction and functional improvement, with observed progressive self‐correction of deformity during the 1‐year follow‐up. Compared with traditional posterior surgery, this strategy offers advantages including shorter operative time, less intraoperative blood loss, and comparable overall complication rates. This provides new insights for personalized and minimally invasive treatment of adult degenerative scoliosis. Further long‐term follow‐up is needed to observe the long‐term corrective effects and complication rates.

Author Contributions

Tianyong Wen: conceptualization, methodology, data curation, writing – original draft. Liukun Xu: methodology, conceptualization, investigation, data curation, software, validation, writing – original draft. Peng Lu: investigation, data curation. Yang Zhang: data curation, investigation. Wei Ji: investigation, data curation. Yang Zheng: data curation, investigation. Zhicheng Zhang: conceptualization, methodology, writing – review and editing, project administration. Tiansheng Sun: conceptualization, methodology, writing – review and editing, project administration.

Funding

This work was supported by the National Key Research and Development Program of China (2022YFC2407200).

Ethics Statement

The study was conducted in accordance with the Declaration of Helsinki and was approved by the Ethics Committee of Chinese PLA General Hospital with the need for written informed consent waived.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Table S1: Results of normality tests for continuous variables in preoperative data of the LLIF and traditional posterior approach surgery groups.

Table S2: Results of normality tests for continuous variables in preoperative and postoperation data of the LLIF group.

Table S3: Intraclass correlation coefficient (ICC) analysis of pre‐ and postoperative imaging parameters.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.