Adult Spinal Deformity

Adult spinal deformity is abnormal curvature or malalignment of the spine in skeletally mature adults, encompassing degenerative scoliosis (abnormal coronal curvature) and, importantly, sagittal-plane malalignment such as loss of lumbar lordosis or forward trunk imbalance. Modern understanding centres on spinal alignment, particularly sagittal balance and the relationship between the spine and pelvis, because malalignment correlates strongly with pain and disability.

Definition

Adult spinal deformity is structural malalignment of the mature spine in the coronal and/or sagittal plane, including degenerative scoliosis and sagittal imbalance, characterised radiographically by curve magnitude and by spinopelvic parameters that relate the spine to the pelvis.

Scope

This topic covers what adult spinal deformity is, why sagittal and spinopelvic alignment matter, how deformity is classified, and a recognised complication of its surgical correction. It is a reference description of the condition and its measurement, not individual clinical guidance.

Core questions

• Why does sagittal alignment, rather than coronal curve alone, drive disability in adults?
• How are spine and pelvis related through spinopelvic parameters?
• How is adult spinal deformity classified for description and comparison?
• What are the trade-offs and complications of correcting deformity?

Key concepts

• Sagittal balance and sagittal vertical axis
• Spinopelvic parameters (pelvic incidence, pelvic tilt, lumbar lordosis)
• Degenerative (de novo) scoliosis
• SRS-Schwab classification
• Pelvic compensation for malalignment
• Proximal junctional kyphosis

Mechanisms

In adults, deformity often arises from asymmetric degeneration and collapse of discs and facet joints, which can produce a coronal curve and, more critically, loss of lumbar lordosis. When the trunk drifts forward, the body compensates by tilting the pelvis backward and flexing the hips and knees to keep the head balanced over the pelvis, an effortful posture that contributes to pain and fatigue. Disability correlates with the degree of sagittal malalignment, which is why measures of sagittal balance and the match between pelvic incidence and lumbar lordosis are central (Glassman, 2005). The SRS-Schwab classification formalises these spinopelvic measurements to describe deformity and grade its severity (Schwab et al., 2012; Slattery & Verma, 2018).

Clinical relevance

Adult spinal deformity is a major source of pain and disability and one of the most demanding areas of reconstructive spine surgery, so understanding alignment-based reasoning is key to interpreting its literature. This entry is a reference description of the condition, its measurement, and a known complication of correction, and is not a basis for individual diagnosis or treatment decisions.

Epidemiology

Degenerative (de novo) adult deformity becomes more common with age as cumulative disc and facet degeneration distorts alignment, and its clinical impact tracks with the degree of sagittal malalignment more than with curve size alone (Glassman, 2005).

Evidence & guidelines

Observational work established that positive sagittal balance correlates with worse pain and function, shifting the field toward sagittal-alignment goals (Glassman, 2005). The validated SRS-Schwab classification provides a common framework for describing deformity by spinopelvic parameters (Schwab et al., 2012; Slattery & Verma, 2018). Surgical correction carries substantial complication rates, including proximal junctional kyphosis at the top of long instrumented constructs, which is well documented (Glattes et al., 2005).

History

The study of adult spinal deformity shifted in the 2000s from a focus on coronal curve magnitude toward sagittal and spinopelvic alignment, after evidence linked positive sagittal balance to pain and disability (Glassman, 2005). This led to validated alignment-based classification systems such as the SRS-Schwab scheme (Schwab et al., 2012) and to increased attention to complications of correction, including proximal junctional kyphosis (Glattes et al., 2005).

Debates

Coronal curve versus sagittal alignment as the driver of disability

Evidence indicating that sagittal malalignment correlates more strongly with pain and disability than coronal curve magnitude reoriented the field's classification and surgical goals toward restoring sagittal and spinopelvic balance.

Key figures

• Steven Glassman
• Frank Schwab
• Virginie Lafage
• Keith Bridwell

Seminal works

• glassman-2005
• schwab-2012

Frequently asked questions

Why is sagittal balance emphasised more than the size of the spinal curve in adults?

Evidence shows that forward sagittal malalignment correlates more strongly with pain and disability than the magnitude of a coronal curve, so modern assessment and correction focus on restoring sagittal and spinopelvic alignment.

What is proximal junctional kyphosis?

It is an abnormal forward angulation that can develop at the segment just above a long instrumented fusion used to correct deformity, and it is a recognised complication that may affect outcomes and sometimes require further surgery.