Roussouly Classification in Adult Spinal Deformity Surgery: Is Preoperative Roussouly Type Associated with Outcomes?

Introduction: The Roussouly classification is a framework to describe normal spinopelvic alignment that has been expanded to patients with adult spinal deformity (ASD). In a cohort of ASD patients undergoing surgery, we sought to apply the Roussouly classification through the following objectives: 1) determine demographic differences in preoperative Roussouly classification, 2) compare what surgical procedures are performed on each Roussouly type, and 3) identify which preoperative Roussouly type is associated with suboptimal outcomes.

Methods: A single-institution retrospective cohort study was performed for patients undergoing ASD surgery from 2009-2021. Inclusion criteria were: ≥5-level fusion, sagittal/coronal deformity, and 2-year follow-up. The primary exposure variable was the preoperative Roussouly type. Outcomes included mechanical complications and minimal clinically important difference (MCID) 30% of patient-reported outcomes measures (PROMs), which included Oswestry Disability Index (ODI), Numeric Rating Scale (NRS)-Back/Leg pain, and EQ-5D.

Results: Of 219 patients undergoing ASD surgery, Roussouly Type 4 patients were younger compared to Types 1-3 (54.8±18.4 vs. range of means 65.6-67.3, p=0.014), with no significant difference in other demographics, comorbidities, or preoperative PROMs. The preoperative Roussouly types were not associated with the surgical parameters of total instrumented levels (p=0.257), combined anterior-posterior vs. posterior approach (p=0.643), number of interbodies (p=0.334), procedure time (p=0.416), or estimated blood loss (p=0.052). However, types 2 and 4 were most likely to have a shorter length of stay vs. types 1 and 3 (5.6±1.9 and 5.2±1.9 vs. 8.5±17.9 and 8.6±6.6, p=0.004), with no difference in discharge disposition, mechanical complications, reoperations, or MCID of PROMs across the four preoperative Roussouly types.

Conclusion : Type 4 Roussouly patients undergoing ASD surgery were younger, indicating earlier symptomatic degeneration requiring surgery than Types 1-3. Types 2 and 4 had a shorter length of stay. No other intraoperative and postoperative differences were seen, perhaps due to similar procedures being performed on very different spinopelvic malalignments.