33. Comparative clinical outcomes of minimally invasive decompression alone for patients with degenerative scoliosis: a focus on severe cases over 20°

BACKGROUND CONTEXT

Degenerative scoliosis (DS) is a prevalent condition in the elderly population. Minimally invasive (MI) decompression, preserving posterior soft tissues and posterior ligamentous complex, is one of the treatment options for lumbar canal stenosis with DS. While MI decompression is a recognized treatment for lumbar canal stenosis in DS patients, its efficacy specifically in severe DS (Cobb angle >20°) is not well-documented.

PURPOSE

This study aimed to evaluate the clinical outcomes of MI decompression with severe. degenerative scoliosis and identify predictors of poor outcomes.

STUDY DESIGN/SETTING

Retrospective review of a prospectively collected multi-surgeon registry.

PATIENT SAMPLE

Patients who underwent MI lumbar decompression alone were included and divided into DS and control groups based on a Cobb angle threshold of 20°.

OUTCOME MEASURES

We compared Patient-Reported Outcomes and Measures (PROMs), including ODI, VAS back, VAS leg, SF-12 PCS and MCS, and PROMIS-PF between groups at the postoperative ≤3 months and ≥1 year postoperatively, focusing on MCID achievement at ≥1 year time point.

METHODS

Data on demographics, comorbidities, spinal alignment, normalized total psoas area (NTPA), and surgical levels were collected. Decompression locations were labeled "scoliosis-related" when the decompression levels included the range of end vertebrae of the Cobb angle, and "outside" when the decompression operative levels did not include the end vertebrae. Matched cohorts were created by variable-ratio greedy matching for comparison, and multivariable regression analysis identified factors impending MCID achievement in ODI for DS patients.

RESULTS

A total of 253 patients were included in the study, with 41 patients in the DS group and 212 in the control group, all of whom underwent MI decompression. After matching for age, gender, osteoporosis status, NTPA, and preoperative ODI, the final matched cohort included 33 DS and 58 control patients. At ≥1 year time point, the DS groups exhibited a significantly lower rate of MCID achievement in ODI (DS: 45.5% vs control 69.0%, P=0.047) and SF-12 PCS (DS: 41.4% vs control 70.6%, P=0.020). The multivariable analysis conducted in the DS group revealed that scoliosis-related decompression (Odds ratio: 9.9, P=0.028) was an independent factor associated with failure to achieve MCID in ODI at the ≥1-year postoperative time point.

CONCLUSIONS

Our findings suggest that in DS patients with a Cobb angle >20 degrees, MI lumbar decompression may yield suboptimal disability and physical function improvements. These results underscore the need for careful surgical planning, particularly regarding decompression at the end vertebrae of the Cobb angle.

FDA Device/Drug Status

This abstract does not discuss or include any applicable devices or drugs.