Study population
Patients receiving anterolateral lumbar short fusion, including ALIF and OLIF, for symptomatic lumbar disorders from 2018 to 2021 were identified as the study population from a tertiary medical center. The selection criteria for the patients were: (1) fusion levels less than 5 levels; (2) presence of symptomatic low back pain or sciatica which were unresponsive to conservative treatment for more than 6 months (3) spinal deformity defined as a Cobb angle >20˚, PT >25˚, or SVA >50mm (4) the pre-OP and post-OP clinical imaging data and follow-up records being complete (5) complete HRQOL assessment at one-year follow-up; (6) pre-OP HRQOL status should be met, including a Visual Analog Scale of Pain in Total (VASP-Total) >4, The European Quality of life in 5-dimensional scale (EQ-5D) >9, and ODI >20%. Exclusion criteria including: (1) Loss of follow-up; (2) Spinal deformity due to the presence of malignancy, and/or neuromuscular disease etiology; (3) Patients without full-length lateral spine radiographs at pre-OP and post-OP.
Radiographic Assessment
Full-length lateral spine radiographs for the kyphosis series (36 inch) at pre-OP visits and the post-OP full one-year follow-up period were analyzed by two well-trained doctors using validated Surgimap surgical planning software (Nemaris Inc., New York, NY, United States) [20]. All radiographic measurements were performed while positioned at a central location based upon standardized techniques, including the, Lumbar Lordosis (LL, lordotic angle from the superior endplate of L1 to the superior endplate of S1), Pelvic Incidence (PI), PI-LL, Pelvic Tilt (PT), Sacral Slope (SS), SVA, and Thoracic Kyphosis (TK) [5].
Outcome measurements
Standardized self-reported HRQOLs consisted of: (1) EQ-5D; (2) VASP measured in total (VASP-Total), in Back (VASP-Back); and (3) ODI were obtained at pre-OP baseline and one-year follow-up.
Subgroup analysis: the possible effect of pre-OP HRQOL severity
In the subgroup analysis, patients were stratified by the severity cut-off value of each HRQOL score prior to surgery, with EQ-5D ≥12, VASP ≥8, and ODI ≥60 considered as worse disabilities and will be stratify into the severe symptom groups [21-24].
Surgical techniques
ALIF procedure
The ALIF was performed with the patient in the supine position. A longitudinal incision was performed for appropriate spine level exposure. A blunt dissection for retroperitoneal exposure and securing of the inferior epigastric, left common iliac vessels, and genitofemoral nerves was performed. The iliac vessels were then exposed and retracted laterally to reveal the fixation level. After x-ray positioning, the target annulus fibrosus was resected and intervertebral disc tissue scraped. Curettage and serial distractors were used for efficient disc removal and disc height evaluation. A bone graft was prepared with an allograft or Actifuse. An Implant cage (TM-400 or the Depuy Synthes Syncage system) was inserted under sufficient exposure. Position of the implant was confirmed through x-ray fluoroscopy. The wound was then closed, and adequate hemostasis was performed.
OLIF procedure
The OLIF was performed with the patient positioned in the right-lateral position (Figure 1). A longitudinal incision on the front line of the iliac crest was made for appropriate spine level exposure before the psoas muscle was gently retracted posteriorly. After x-ray positioning, the target annulus fibrosus was resected and intervertebral disc tissue scraped. Serial trial was applied for optimal cage size. Endplate damage was avoided during the procedure. The Implant cage (Medtronic CLYDESDALE spine system) was inserted under sufficient exposure (Figure 2). Position of the implant was confirmed by x-ray fluoroscopy (Figure 3). The wound was then closed, and adequate hemostasis performed.
Patient Age-Adjustment Grouping
Age-specific sagittal parameters were calculated according to a previously published formula by Lafage et al. (Figure 4) [11]. After the operation, patients were divided into either the “Sufficient group” or “Under group” in accordance with the achievement or under treatment of the three age-adjusted parameters: SVA, PT, and PI-LL (Figure 5). Post-OP clinical outcomes were measured and compared to the pre-OP baseline between groups at one-year follow-up.
Statistical Analysis
Demographics factors and clinical data, including age, body mass index (BMI), gender, operation technique, and length of postoperative hospital stay were recorded. Normality of data was determined via the Shapiro-Wilk test. Continuous variables were described with the mean and standard deviation. Intra-group HRQOL means analyses were conducted via one-way analysis of variance (ANOVA), Kruskall-Wallis test, or Mann-Whitney u test according to appropriate models. Statistical analyses were two-sided and P <0.05 was considered statistically significant. All statistical analyses were performed using SPSS version 24 (IBM, Armonk, New York, USA).