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Should We Use the Largest Femoral Head With the Smallest Acetabular Component in Primary Total Hip Arthroplasty?
Mark Wu1, Brett R Bukowski1, Kristin M Fruth2
1Department of Orthopaedic Surgery, Mayo Clinic, Rochester, Minnesota.
Background:
There has been an increasing use of larger femoral head sizes to mitigate dislocation risk after total hip arthroplasty. Manufacturers have created thinner, highly cross-linked polyethylene (HXLPE) liners to maximize effective head size. We investigated whether there was a survivorship penalty if the largest head was chosen at the smallest compatible acetabular component size, and as a secondary aim, we analyzed whether there was a decreased dislocation risk.
Methods:
We reviewed 1,860 posterior approach primary total hip arthroplasties with HXLPE from 2005 to 2021. Subjects were divided into three groups based on acetabular component transition points at which a larger femoral head could be used: group 1 was 28-mm (N = 18) versus 32-mm (N = 89) heads, group 2 was 32-mm (N = 383) versus 36-mm (N = 429) heads, and group 3 was 36-mm (N = 806) versus 40-mm (N = 135) heads. The mean age was 66 years, 75% were women, and the mean body mass index was 30. There were 48% that had ceramic heads, and 52% had metal heads. The mean follow-up was 7 years.
Results:
There were two liner dissociations (0.1%) and no liner fractures. The 10-year survivorships free of dislocation, revision, and reoperation were 95, 95, and 93%, respectively. The 5-year survivorship free of dislocation for group 1 was 94% for 28-mm and 99% for 32-mm heads; for group 2, 96% for 32-mm and 99% for 36-mm heads; and for group 3, 96% for 36-mm and 95% for 40-mm heads. Cox regression demonstrated no difference in reoperation or revision rates between head sizes in any group.
Conclusions:
When using HXLPE liners, pairing the largest femoral head with the smallest compatible cup for 32-mm, 36-mm, and 40-mm heads did not increase risk for liner-related complications, revisions, or reoperations. There was no difference in dislocation risk when using the larger femoral head at transitional cup sizes, though this study was under-powered to detect this difference.
Level Of Evidence:
III, retrospective comparative cohort study.
