Unconstrained tripolar hip implants provide an additional bearing using a mobile polyethylene component between the prosthetic
head and the outer metal shell. Such a design increases the effective head diameter and therefore is an attractive option
in challenging situations of unstable total hip arthroplasties. We report our experience with 54 patients treated using this
dual mobility implant in such situations. We ascertained its ability to restore and maintain stability, and examined component
loosening and component failure. At a minimum followup of 2.2 years (mean, 4 years; range, 2.2–6.8 years), one hip had redislocated
2 months postoperatively and was managed successfully without reoperation by closed reduction with no additional dislocation.
Two patients required revision of the implant because of dislocation at the inner bearing. Technical errors were responsible
for these failures. Three patients had reoperations for deep infections. The postoperative radiographs at latest followup
showed very satisfactory osseointegration of the acetabular component because no radiolucent line or osteolysis was reported.
Use of this unconstrained tripolar design was successful in restoring and maintaining hip stability. We observed encouraging
results at short-term followup regarding potential for loosening or mechanical failures.
Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.
One or more of the authors (OG, VP, JBH) certifies that he has or may receive payments or benefits from a commercial entity
(Amplitude, 01707 Neyron, France) related to this work.
Each author certifies that his institution either has waived or does not require approval for the human protocol for this
investigation and that all investigations were conducted in conformity with ethical principles of research.