This prospective radiographic study asked whether tailoring acetabular cup inclination and anteversion to each patient's spinopelvic mobility keeps the cup in a safe sagittal position. It measured 160 hips with standing and sitting lateral spinopelvic radiographs. The work helped formalize the hip-spine relationship behind individualized cup planning.
When you plan a THA, get a standing and sitting lateral spinopelvic radiograph before settling on a cup target.
The key mental model: sitting normally tilts the pelvis posteriorly and opens the acetabulum. A stiff or fused spine cannot do this, so the cup must be opened mechanically with higher inclination (near 45°) and anteversion. A hypermobile spine does the opposite, so back the angles down to avoid a vertical cup and dropout dislocation.
Identify the five patterns: normal, hypermobile, stuck standing, stuck sitting, and kyphotic. ΔST < 10° flags stiffness, ≤ 5° defines fusion, and > 30° defines hypermobility. The highest-risk patient is the one with a fused or flat kyphotic spine. No static cup position fully compensates for lost acetabular motion, which is why these patients are candidates for dual mobility or added constraint.
This paper is foundational to the hip-spine syndrome concept and individualized cup positioning. Remember its limit: outcomes here are radiographic surrogates for impingement, not proven dislocation reduction.
This prospective radiographic study asked whether tailoring acetabular cup inclination and anteversion to each patient's spinopelvic mobility keeps the cup in a safe sagittal position. It measured 160 hips with standing and sitting lateral spinopelvic radiographs. The work helped formalize the hip-spine relationship behind individualized cup planning.
When you plan a THA, get a standing and sitting lateral spinopelvic radiograph before settling on a cup target.
The key mental model: sitting normally tilts the pelvis posteriorly and opens the acetabulum. A stiff or fused spine cannot do this, so the cup must be opened mechanically with higher inclination (near 45°) and anteversion. A hypermobile spine does the opposite, so back the angles down to avoid a vertical cup and dropout dislocation.
Identify the five patterns: normal, hypermobile, stuck standing, stuck sitting, and kyphotic. ΔST < 10° flags stiffness, ≤ 5° defines fusion, and > 30° defines hypermobility. The highest-risk patient is the one with a fused or flat kyphotic spine. No static cup position fully compensates for lost acetabular motion, which is why these patients are candidates for dual mobility or added constraint.
This paper is foundational to the hip-spine syndrome concept and individualized cup positioning. Remember its limit: outcomes here are radiographic surrogates for impingement, not proven dislocation reduction.