Anatomic diameter femoral heads in total hip arthroplasty: a preliminary report.

Background: The stability of total hip replacements has been directly related to the diameter of the femoral head in several studies; however, durability has necessitated the use of femoral heads with a relatively small diameter. Recent developments in metal-on-metal technology have allowed for the use of femoral head bearings that are anatomic in diameter. In this case series, we report on the early results of patients who were at greater risk for dislocation because of anatomic deficiencies or increased range-of-motion activities and underwent hip arthroplasty with implants that had articulating surfaces approaching anatomic dimensions.

Methods: Thirty-four patients underwent forty total hip arthroplasties with use of a modular metal-on-metal articulation with an anatomic diameter femoral head and a press-fit stem. Thirty patients were active, and four patients were profoundly disabled and had bone or soft-tissue deficiencies that would increase the risk for dislocation. Dislocation precautions were maintained for six weeks, and patients were allowed extreme ranges of motion at three months.

Results: There were no dislocations. Active patients continued in extreme range-of-motion activities. Disabled patients improved but were limited by their comorbidities.

Conclusions: Anatomic diameter femoral heads offer distinct theoretical advantages in total hip arthroplasty. These short-term results are encouraging, and further study of this new technology in a larger series with a longer follow-up period is warranted.