Long-term clinical and radiographic outcomes of pedicle subtraction osteotomy for fixed sagittal imbalance: Does level of proximal fusion affect the outcome? Minimum 5-year follow-up

Study Design: Retrospective case series of surgically treated adult patients with fixed sagittal imbalance. Objective: To assess clinical and radiographic changes after pedicle subtraction osteotomy (PSO) to treat adult fixed sagittal imbalance. Background: Although recent reports have shown favorable clinical outcomes for PSO, few reports have published long-term follow-up outcomes. It is also unknown whether long-term outcomes are correlated with the level of proximal fusion and the radiographic changes that are observed after PSO. Materials and Methods: We reviewed the charts, X-rays, and postoperative SRS-22 and Oswestry Disability Index (ODI) scores of 32 adult patients who presented with fixed sagittal imbalance and were treated with lumbar PSO. Long fusions were defined as those proximal to T6, and short fusions were defined as those below T8. Measured radiographic parameters included thoracic kyphosis, lumbar lordosis (LL), sacral slope, pelvic incidence, and sagittal balance (SVA). Statistical analysis included Student t test and chi-square test. A p value of < .05 and a confidence interval of 95% were considered statistically significant. Results: Among the reviewed cases were 23 women and 9 men, with a mean age of 50.9 years (range, 33-76 years) and a mean follow-up 8.6 years (range, 5-16 years). The LL increased from -16.0° preoperatively to -52.1° postoperatively. This metric decreased to -51.0° at final follow-up. The SVA decreased from 10.4 cm preoperatively to 3.6 cm postoperatively. The SVA increased to 5.4 cm at the final follow-up visit. There were 17 long fusions and 15 short fusions. The SRS scores at the final follow-up time point were: total, 3.63; function, 3.59; pain, 3.68; self-image, 3.46; mental health, 3.56; satisfaction, 4.26.Atotal of 16 patients exhibited minimal disability, 11 exhibited moderate disability, and 2 exhibited severe disability in ODI scores at the final follow-up visit (average, 28.2%). The SRS and ODI scores were not significantly different between groups (p=.64 for SRS; p=.59 for ODI).We observed no significant differences between groups with respect to the LL, sacral slope, or pelvic incidence. The observed increase inSVAat the final follow-up visit was significantly larger in the short fusion group compared with the increase we observed in the long fusion group (p=.03). The thoracic kyphosis (T5-T12) and proximal junctional angle at the final follow-up visit also significantly increased in patients who underwent a short fusion (p<.001).A total of 14 major complications occurred in 12 patients (8 in the short fusion group and 6 in the long fusion group) (p = .43). Eight patients required additional surgery to treat these complications. Conclusions: In a group of adults presenting with fixed sagittal imbalance, PSO provided good sagittal balance and maintained favorable clinical outcomes in both the short and long fusion groups despite a slight decrease in the SVA and a high complication rate. The data suggest that the loss of sagittal balance may be attributed to increase global and junctional kyphosis in short fusion groups, and should be monitored for long-term outcomes. Particular attention should be paid to the long-term deterioration of the SVA in adults who present with fixed sagittal imbalance after PSO.