Sagittal vertical axis

Principle and interpretation

The usual sacral landmark is the posterosuperior corner of S1. Offset depends on posture and compensation; arm and knee position can influence the examination.

Indications, limitations and precautions

Sagittal vertical axis is useful for deformity assessment but cannot be reduced to one universal threshold. Age, symptoms, pelvis and compensatory mechanisms inform management.

Points to consider

These parameters describe geometric relationships on standardized images. Standing position, framing and landmark selection can influence values. Interpretation considers age, compensation and the overall sagittal profile; one number is not a surgical indication.

Role of TAGMED care

At TAGMED, assessment aims to understand symptoms, history and functional limitations. Manual care and osteopathy, motorized spinal decompression, laser and shockwave have different indications. The term described in this entry is not enough to select any of these modalities. Their relevance, limitations and possible contraindications should be discussed in relation to diagnosis and individual goals.

Related concepts and distinctions

These concepts belong to the same field, but are not synonyms.

• Sacral slope — Angle between the upper sacral endplate and horizontal, used to describe sagittal sacral orientation.
• Pelvic incidence–lumbar lordosis mismatch — Difference between pelvic incidence and lumbar lordosis, used to assess their relationship in sagittal alignment analysis.
• Pelvic tilt — Angle describing pelvic orientation relative to vertical, measured using the sacral endplate and femoral-head axis.

Medical references

1. Legaye et al., original research indexed in PubMed. Pelvic incidence: a fundamental pelvic parameter for three-dimensional regulation of spinal sagittal curves.
2. Original research indexed in PubMed. Pelvic parameters: origin and significance.

References document the topic; their inclusion does not imply endorsement of TAGMED services by those organizations.