Long-Term Loss of Alignment Following ASD Surgery in the Absence of Mechanical Complications: Aging Spine?

Study design: Retrospective analysis of a prospective multicenter adult spinal deformity (ASD) registry.

Objective: Assess whether spinal alignment deteriorates postsurgery in the absence of mechanical complications and evaluate the long-term outcomes of ASD surgery over a 5-year period.

Summary of background data: ASD is prevalent among older adults, leading to significant pain and disability. Surgical intervention, although increasingly popular, is associated with complications, high costs, and uncertain long-term outcomes beyond 2 years. Mechanical failure and alignment loss often necessitate revision surgeries, but the natural progression of spinal alignment postsurgery without complications remains unclear.

Methods: Clinical and radiological data were analyzed from surgical patients in a multicenter ASD registry who maintained alignment within the instrumented region and completed a 5-year follow-up. The study evaluated patient demographics, surgical details, radiological parameters, and quality of life (QoL) outcomes. Subanalyses were conducted to compare patients with different initial postoperative alignments and fixation levels.

Results: The study included 79 patients (83.5% women, average age 61.9 y) with a mean of 10.7 fused levels. Of these, 29.1% underwent 3-column osteotomies (3CO), and 88.6% had a posterior-only approach. Although 65% showed favorable alignment at 6 weeks postsurgery, there was a progressive deterioration in global sagittal alignment (Global Tilt/RSA) and thoracic kyphosis over 5 years ( P <0.05), along with increased pelvic compensation (PT SS/RPV). These changes did not correlate with worsening health-related quality-of-life outcomes ( P >0.05). Older age was linked to greater progression in T2-T12 kyphosis, and osteoporosis was associated with increased SVA and RPV. Optimal immediate postoperative sagittal alignment did not prevent this "aging effect."

Conclusions: ASD surgery and achieving ideal postoperative alignment do not prevent the ongoing "aging" of the noninstrumented spine. Both thoracic and global sagittal alignments deteriorate over time. Although no functional decline has been observed, the implications of these changes for surgical planning remain uncertain.