Do all symptomatic adjacent segment diseases (ASD) require surgery? a prognostic classification and predictors of surgical treatment of lumbar ASD.

Introduction: Symptomatic Adjacent segment disease presents in myriad ways with varying clinic-radiological presentation but the optimal management and the factors that predict need for revision surgery are unclear.

Methodology: Consecutive patients (n = 132) who experienced significant back or leg pain after an asymptomatic period (minimum 1 year) following a lumbar fusion were evaluated with dynamic radiographs and MRI. ASD was classified anatomically as proximal (86.3%), distal (12.1%, or combined (1.5%) and, sub-classified pathologically into six sub-types: Type 1: Disc prolapse (17.4%), Type 2: Disc degeneration with intra-discal instability (15.1%), Type 3: Anterolisthesis and facet instability (6.8%), Type 4: Retrolisthesis (25%), Type 5: Stenosis (21.9%) and Type 6: Combined types (13.6%).

Results: The mean duration between the index surgery and ASD was 5.9 ± 4.1 years. Surgery was required in 40.9% (54/132). Six factors were highly predictive of surgical treatment for ASD, viz., Diabetes mellitus (OR-4.3, p = 0.007), ASD- disc prolapse (OR 6.3, p = 0.018), ASD intra-discal instability (OR-16.8206, p = 0.003), ASD - anterolisthesis (OR - 8.2998, p = 0.043), Facet angle > 75° (OR 37.6, p = 0.02) and radiculopathy (OR 48.0, p = 0.002). Retrolisthesis was the most benign type as 84.8% patients were managed conservatively (p = 0.016). Among proximal ASD, retrolisthesis was the most common subtype (28.9%) while disc prolapse was the most common subtype in distal ASD 37.5% (p = 0.032).

Conclusion: The study classifies the versatile clinic-radiological presentation of ASD, and identifies factors that predicted the development of the different sub-types of ASD. Knowledge about the six clinic-radiological factors that predict the need for surgical treatment in ASD is beneficial.