Impact of Obesity on Alignment and Outcomes in Adult Spinal Deformity: A 3-year Category-based Analysis

Introduction: The impact of obesity on global spinopelvic alignment is poorly understood.

Methods: Inclusion criteria were operative ASD patients(Cobb≥20°, SVA≥50mm, PT≥25°, and/or TK>60°) who underwent ASD corrective surgery, >18yrs with complete baseline(BL) and 3-year(3Y) radiographic and HRQL data. Patients were stratified by body mass index into normal BMI, overweight, and obese groups( < 25, 25–30, and >30). Means comparison tests assessed differences in baseline demographics, surgical details, compensatory mechanisms, alignment, and perioperative outcomes between cohorts. Additionally, multivariable logistic regression and ANCOVA assessed differences in outcomes.

Results: 340 ASD patients met inclusion criteria(Age: 59.0±15.0;F=78%;CCI:1.6±1.7). 91 patient were obese. 126 were overweight. 123 has a normal BMI. In terms of demographics, O has significantly higher CCI, m-ASD-FI, age, less female.(all;p < 0.004). At 3Y, obese patients exhibited the most pronounced thoracic kyphosis in the unfused region compared to the overweight group and normal BMI respectively(-27°vs-24°vs-19°; p=0.009). They also experienced the greatest loss of correction in unfused thoracic kyphosis over 3Y(-9.1°vs-7.7°vs -6.2°;p=0.045). At 3Y, the obesity group demonstrated the highest prevalence of mismatched PT sagittal modifier(60.4%vs57.1%vs43.1%; p=0.021) and mismatched SVA modifier(52.7%vs40.0%vs26.8%;p < 0.001), lowest Roussely match rate at 1Y(37.2% vs 52.1% vs 56.3%; p=0.023), 2Y(37.5% vs 39.6% vs 55.1%; p=0.35)

At 3Y, obese patient has the highest NRS-leg scores, the highest ODI, the lowest PCS, lowest SRS activity, lowest SRS appearance(all;p < 0.05). In terms of opioid usage, obese has the highest SRS-22r-q11 at 6W(31.6%vs8.2%vs18.2%;p=0.02). In terms of complication, obese group has a significant higher rate of major medical complication before 90D(11.7% vs 6.1%;p=0.048), reoperation before discharged(6.7% vs 1.7%;p=0.007), reoperation before discharged due to surgical complication(5.0%vs1.5%;p=0.028), after 90D before 2Y major complication (11.% vs 6.1%;p=0.048), major surgical complication after 90D before 2Y(11.7%vs6.1%;p=0.048), higher rate of PJF at 6W(6.6%vs1.2%;p=0.006).

Conclusion : At 3Y, Obesity significantly impacts both spinopelvic alignment and clinical outcomes in adult spinal deformity correction. These findings highlight the challenges in achieving and maintaining optimal alignment in obese patients undergoing ASD corrective surgery, underscoring the need for tailored surgical strategies and intensive postoperative management in this population.