With increased use of alternative bearings, surgeons have moved from utilization of 22, 26, 28 and 32mm heads to larger head diameters in total hip arthroplasty (THA). Reported benefits of large heads are enhanced stability secondary to the increased range of motion prior to impingement and the increased jump distance required for subluxation from the acetabulum.

This study evaluates the use of large diameter heads in primary THA comparing the rate of dislocation to a published study from our practice as a historic control.

Between October of 2001 and October 2008, 2015 THA with large heads were performed in 1743 patients. Femoral head sizes ranged from 36 to 60mm, with articulations consisting of metal-on-poly, ceramic-on-poly, and metal-on-metal. Operative approach was 63% less invasive direct lateral, 10% anterior supine intermuscular, and 27% standard direct lateral. In 1999 (Mallory et al., Clin Orthop Relat Res) we reported a low incidence of 12 dislocations (0.8%) in 1518 primary THA done with smaller femoral heads via a standard direct lateral approach. In the current series with large heads, follow-up averaged 22 months. There has been one dislocation requiring revision (0.05%), representing a significant reduction from our earlier report (p=0.0003). Forty additional acetabular components have been revised (2.0%), with eight related to sepsis (0.4%), 23 aseptic loosening (1.1%), six metal sensitivity (0.2%), one pseudotumor (0.05%), one failure of ingrowth (0.05%), and one acute early migration (0.05%).

The use of larger diameter heads has significantly lowered our dislocation rate in primary THA with only one occurrence observed in 2015 cases, for a rate of 0.05% at two years average follow-up.