Prevention and treatment of dislocation after total hip replacement using large diameter balls

The purpose of this study was to review safety and efficacy of total hip arthroplasty using large-diameter femoral heads in treatment and prevention of dislocation. One hundred forty hips in 135 patients were replaced using femoral heads at least 36 mm in diameter. The average age of the patients was 61.6 years. The patients were grouped into three categories depending on their diagnoses: recurrent dislocations from previous total hip replacements (Group 1; 29 hips); revision surgeries not including revisions for dislocations (Group 2; 54 hips); and primary surgeries (Group 3; 57 hips). The average followup was 5.5 years (range, 1-17 years). A total of 16 hips were revised: six for instability, four for fracture or disassociation of a conventional polyethylene liner, three for aseptic loosening of the socket, and three for sepsis. One hip from Group 1 dislocated at 12.5 years postoperatively, was treated with closed reduction, and since has been nonrecurring. UCLA hip scores all improved significantly. The prevalence of dislocation varied among the three groups, with 13.7% for Group 1, 1.8% for Group 2, and 3.5% for Group 3. The failure in the six cases that required revision for instability was attributable to poor socket orientation. All the hips became stable after revision without the use of a constrained acetabular liner. Large-diameter femoral heads provide additional stability not only for patients with recurrent dislocations, but also for patients having revision. The new, more wear-resistant bearings now enable the surgeon to extend the use of big femoral heads to primary total hip arthroplasty. Metal-on-metal seems to be the material of choice for a bone-conserving reconstruction with large femoral heads.