Extended Analysis of 5-Year Durability of Approaches for Adult Spinal Deformity

Introduction: The benefits of interbody fusion can be conferred via different approaches: lateral lumbar interbody fusion (LLIF), posterior transverse lumbar interbody fusion (TLIF), or anterior lumbar interbody fusion (ALIF). Currently, there has been little known about the sustainability of realignment and durability associated with each approach beyond 2 years.

Methods: Operative ASD patients with preoperative baseline (BL) and 5 year (5Y) data were included. Descriptive statistics and ANOVA testing compared the likelihood of mechanical complications and maintaining optimal alignment by approach. Predictors of mechanical complications at 2Y and 5Y derived via multivariable regression analysis were compared to determine if there was concordance amongst the two.

Results: 330 patients met inclusion criteria (mean BL age: 64.2 ± 9.6 years, 79.4% female, mean BL BMI: 27.9 ± 5.6kg/m2, mean BL CCI 1.9 ± 1.7). In terms of surgical parameters, mean operative time was 435.1 minutes, mean EBL 1,686 mL, and mean levels fused 2.39 ± 1.7. 216 (65.5%) underwent ALIF, 201 (60.9%) underwent TLIF, and 157 (47.6%) underwent LLIF. 41 (19.0%) patients who received ALIFs, 30 (14.9%) patients who underwent TLIFs, and 30 (14.9%) who approached as LLIF experienced PJK or PJF necessitating reoperation, but the difference across groups was not significant (p>.05). By 5 years, 54 patients (17.1%) demonstrated improvement in radiographic parameters SVA, PT, and PI-LL. Upon logistic regression while controlling for prior history of fusion, none of the approaches appeared to be significant predictors of reoperation, pseudoarthrosis, or improvements in radiographic alignment at 5 years. Meanwhile, at 2 years, LLIF appeared to be a predictor of alignment improvement (OR 3.562 [95% CI 1.076-11.791], p<.038).

Conclusion : This study did not identify any significant associations between approach and durability of outcomes at 5 years. As such, further analysis should focus on identifying the optimal patient population for there may be equipoise amongst approaches yet nuances to their applications. Outcomes at 2 years and 5 years may have different etiologies and driving forces, and approach may be more relevant for earlier complications versus those that develop later.