Livermore et al. developed a standardized radiographic technique to measure polyethylene wear in THA and applied it to 385 hips followed at least 9.5 years. The study directly compared linear and volumetric wear across 22mm, 28mm, and 32mm femoral heads in comparable patient populations. This was the first long-term clinical study to quantify how head diameter determines both the pattern and magnitude of acetabular polyethylene wear.
Head size selection in THA was historically guided by stability and frictional torque theory — not clinical wear data. Before this paper, no long-term clinical study had compared all three head sizes head-to-head in comparable patients.
The key insight is that linear wear and volumetric wear tell different stories. A radiograph showing acceptable linear penetration with a 32mm head can mask a debris burden nearly twice that of a 28mm head, because volume scales with the square of radius. It is debris volume, not linear penetration alone, that drives osteolysis and loosening.
When you see widening of the Zone 1 acetabular radiolucent line on follow-up imaging, think about the patient's head size: 32mm heads in this cohort showed median Zone 1 lucency of 2.4mm vs under 1mm for smaller heads.
This paper is the clinical foundation for why 28mm became the default head size for cemented metal-on-conventional-polyethylene THA. The subsequent shift to highly cross-linked polyethylene and larger heads for dislocation reduction required new bearing surface data before it could be safely adopted. A direct consequence of what Livermore established here.
Livermore et al. developed a standardized radiographic technique to measure polyethylene wear in THA and applied it to 385 hips followed at least 9.5 years. The study directly compared linear and volumetric wear across 22mm, 28mm, and 32mm femoral heads in comparable patient populations. This was the first long-term clinical study to quantify how head diameter determines both the pattern and magnitude of acetabular polyethylene wear.
Head size selection in THA was historically guided by stability and frictional torque theory — not clinical wear data. Before this paper, no long-term clinical study had compared all three head sizes head-to-head in comparable patients.
The key insight is that linear wear and volumetric wear tell different stories. A radiograph showing acceptable linear penetration with a 32mm head can mask a debris burden nearly twice that of a 28mm head, because volume scales with the square of radius. It is debris volume, not linear penetration alone, that drives osteolysis and loosening.
When you see widening of the Zone 1 acetabular radiolucent line on follow-up imaging, think about the patient's head size: 32mm heads in this cohort showed median Zone 1 lucency of 2.4mm vs under 1mm for smaller heads.
This paper is the clinical foundation for why 28mm became the default head size for cemented metal-on-conventional-polyethylene THA. The subsequent shift to highly cross-linked polyethylene and larger heads for dislocation reduction required new bearing surface data before it could be safely adopted. A direct consequence of what Livermore established here.