Adult spinal deformity (ASD) is a heterogeneous group of conditions including: degenerative (de novo) scoliosis from asymmetric disc and facet degeneration in adults; adult idiopathic scoliosis representing progression of adolescent idiopathic scoliosis; iatrogenic deformity post-surgery (flatback syndrome); and adjacent segment deformity. Prevalence increases with age, affecting 30-60% of adults over 60.
Pathophysiology involves age-related disc degeneration, facet joint arthrosis, ligamentous insufficiency, and osteoporosis, leading to progressive loss of lumbar lordosis (sagittal imbalance), coronal scoliosis, and rotational deformity. Sagittal vertical axis (SVA), pelvic incidence-lumbar lordosis mismatch (PI-LL), and pelvic tilt (PT) are critical radiographic parameters predicting disability.
Symptomatic ASD presents with axial back pain, radicular pain from foraminal stenosis, neurogenic claudication from canal stenosis, and progressive postural abnormalities (forward stooping requiring hip and knee flexion to compensate). Non-operative treatment includes physical therapy, NSAIDs, weight management, bracing, and selective injections. Surgical indications include disabling pain, neurologic deficit, progressive deformity, and failure of conservative care. Modern surgical strategies range from minimally invasive lateral lumbar interbody fusion (LLIF) and transforaminal lumbar interbody fusion (TLIF) for milder deformity to extensive open posterior column osteotomies (PSO, SPO, VCR) and combined anterior-posterior approaches for severe rigid deformity. Major complications include pseudarthrosis, proximal junctional kyphosis (PJK), hardware failure, and neurologic injury.