The incidence of dislocation after total hip arthroplasty is significantly higher after revision and in patients with neuromuscular or other complications. To prevent dislocation, 55 patients with multiply revised total hip arthroplasties, unstable hips, and neuromuscular and/or neurologic conditions associated with total hip arthroplasty received implants with the S-ROM constraining acetabular insert. With an average follow up of 30.2 months, 50 patients have not experienced redislocation after insertion. Before S-ROM, our dislocation rate in 176 revision total hip arthroplasties was 19%, but is now 4.5% (P less than .001).