Introduction: There are few reports on comparative study between anterior column realignment (ACR) through conventional approaches (pre-posterior release-anterior-posterior surgery, PAP) and minimal invasive surgery–lateral lumbar interbody fusion (MIS-LLIF) through hybrid approaches (anterior-posterior surgery, AP) for severe DSI. Therefore, this study was to investigate radiographic and clinical outcomes after surgical correction for adult spinal deformity (ASD) with degenerative sagittal imbalance (DSI) by 2 different surgical procedures.

Methods: This retrospective study included a total of 91 patients (average age 69.7 years) who had undergone two different surgical procedures for ASD with DSI between May 2012 and July 2019. Inclusion criteria were 1) age > 65 years, 2) ASD with DSI, 3) long-segment fusion from T10 to sacrum with sacropelvic fixation using bilateral iliac screws, 4) posterior 2-rod instrumentation, and 5) patients undergone LLIF on 3 or more segments from L1 to L5, and/or posterior lumbar interbody fusion (PLIF) or anterior lumbar interbody fusion (ALIF) for L5-S1. Hybrid MIS-LLIF was performed on 26 patients as AP group, and ACR was performed on 65 patients as PAP group. Clinical data collected from medical records included age at the index surgery, sex, body mass index, smoking history, bone mineral density, Charlson Comorbidity Index and previous spinal surgery. Spinopelvic parameters in whole spine standing radiographs were collected and compared at preoperative and regular postoperative follow-ups. After 1:1 propensity-score matching, 24 pairs of patients in each group were selected and analyzed again.

Results: Operative time was  longer and estimated blood loss was greater in PAP group than AP group (p<0.05). ICU care was needed in 15.4% of AP group and 23.1% of PAP group without statistical significance (p>0.05). Also, The incidences of other perioperative complications were not different between the two groups. Although preoperative LL and PI-LL were lower in PAP group, T1 pelvic angle and pelvic incidence minus lumbar lordosis were better in PAP group. However, proximal junctional angle was higher at postoperative 3-month and the last follow-up in PAP group than AP group (p=0.001 and 0.047, respectively). T1PA, PI-LL, and sagittal vertical axis were not different between the two groups at the last follow-up. Before matching, the incidence of PJK/PJFs was similar between these two groups (19.2% in AP and 26.2% in PAP, p>0.05). However, the incidences of sagittal imbalance without PJK/PJF (34.6% in AP and 3.1% in PAP, p=0.014) and rod fracture (3.8% in AP and 24.6% in PAP, p=0.008) were different between the two groups. After matching for age, BMI, and BMD, 24 patients in each group were included. The incidences of sagittal imbalance without PJK/PJF (37.5% in AP and 4.2% in PAP, p=0.036) and rod fracture (4.2% in AP and 33.3% in PAP, p=0.01) were also different between the two groups

Discussion: Although PAP group achieved more correction of sagittal malalignment, PAP group showed higher tendency of mechanical complications. However, the rate of revision surgery was not significantly different between the two groups. We suggest surgeons should choose each treatment with considering their own advantages and disadvantages.