Table 1.
Overview of terms related to spinopelvic mobility according to Ike et al., Attenello et al., and Lum et al. [15,16,17].
| Term | Definition |
|---|---|
| Sacral Slope (Tilt) (SS) | Angle Between A Horizontal Line and The Sacral Endplate. |
| Pelvic Incidence (PI) | Angle Centered at Midpoint of The S1 Endplate, Perpendicular to The Sacral Base and Center of The Femoral Heads. Intraindividual Constant Value That Does Not Change with Sitting and Standing. |
| (Spino)Pelvic Tilt ((s)PT) | Angle Between the Vertical Axis and A Line from The Center of The Femoral Heads to The Midpoint of The S1 Endplate. Term for Pelvic Tilt Used in Spine Literature Referring to The Position of The Sacrum Relative to The Femoral Heads. |
| Anterior Plane Pelvic Tilt (APPt) | Term for Pelvic Tilt Used in Arthroplasty Literature Referring to The Rotation of The Pelvis in The Sagittal Plane Defined by The Angle Between the Two Anterosuperior Iliac Spines and The Anterior Surface of The Pubic Symphysis and The Coronal Vertical Plane. |
| Pelvic Retroversion | Posterior Rotation of The Pelvic in The Sagittal Plane, Equivalent to Posterior Anterior Plane Pelvic Tilt. |
| Anteinclination (AI) | Angle Between A Line from Anterior to Posterior Acetabular Wall and a Horizontal Reference Line. Changing with Pelvis Motion. The Angle Is Affected by a Combination of Anteversion And Inclination of The Cup. |
| Sacroacetabular Angle (SAA) | Angle Between Sacral Slope (SS) And A Line from Anterior to Posterior Wall (AI). |
| Proximal Femoral Angle (PFA) | Angle from The Center of Femoral Heads, Between Midpoint of The S1 Endplate and The Anatomical Femoral Stem. |
| Combined Sagittal Index (CSI) | Angle of The Acetabular Cup in The Sagittal Plane That is the Sum of The Anteinclination (AI) And the Pelvic Femoral Angle (PFA). |
| Spinal Imbalance | Abnormal Spinal Mobility Defined by Pelvic Incidence (PI) And Lumbar Lordosis (LL) Mismatch (PI–LL) > 10° Or C7–SVA (Sagittal Vertical Axis) |
| Hypermobility | Spinopelvic Motion When Transitioning from Standing to Sitting. Defined as >30° ΔSS |
| Stiffness | Spinopelvic Motion When Transitioning from Standing to Sitting. Defined as <10° ΔSS |