Postsurgical outcomes differ according to baseline sagittal alignment status even in patients achieving adequate correction relative to age-adjusted alignment target for adult spinal deformity.

Background context: Baseline severities of sagittal malalignment and degrees of pelvic compensation may affect postsurgical outcomes differently after adult spinal deformity (ASD) surgery, even if the patients achieved optimal correction of sagittal malalignment.

Purpose: To investigate whether postsurgical outcomes vary according to baseline sagittal alignment and pelvic compensation status in patients achieving adequate correction relative to age-adjusted alignment target in ASD surgery.

Study design/setting: Retrospective study PATIENT SAMPLE: Patients who underwent ≥ 5-level fusion to the pelvis for ASD; achieved matched correction relative to age-adjusted pelvic incidence (PI)-lumbar lordosis (LL); and completed ≥ 2-year follow-up.

Outcome measures: Radiographic results, mechanical failures, and clinical outcomes METHODS: Patients were divided into three groups based on baseline sagittal vertical axis (SVA) and pelvic tilt (PT)/PI ratio (median value of PT/PI ratio = 0.61): Group A (SVA < 5 cm), Group B (SVA ≥ 5 cm and PT/PI ratio <0.61, and Group C (SVA ≥ 5 cm and PT/PI ratio ≥ 0.61). Radiographic results, mechanical failures, and clinical outcomes were compared among the three groups.

Results: A total of 153 patients were included in the study. They were predominantly female (89.5%), with a mean age of 68.3 years. The mean follow-up duration was 49.0 months. There were 50 patients in group A (SVA < 5cm), 53 in group B (SVA ≥ 5cm and low PT/PI), and 50 in group C (SVA ≥ 5cm and high PT/PI). No significant differences were observed in all radiographic parameters at six weeks. At the last follow-up, the PI-LL was comparable among the three groups; however, the SVA was significantly greater in groups B and C than in group A (46.5mm and 46.9mm vs. 31.5mm, p=.039). The PT at the last follow-up was significantly lower in group B than in group A and C (22.4° vs. 26.0° and 28.2°, respectively, p=.001). The rates of mechanical failure and subsequent revision surgery and did not differ among the groups. The final clinical outcomes were comparable among the three groups.

Conclusions: This study revealed that patients in groups B and C were likely to have a suboptimal sagittal alignment status at the last follow-up compared with those in group A. Tailored approaches considering patient's baseline alignment and compensatory status are recommended to optimize the final sagittal alignment status.