A dual-mobility cup reduces risk of dislocation in isolated acetabular revisions.
BACKGROUND
Isolated acetabular revisions using standard cups are at risk of dislocation. The introduction of a nonconstrained dual-mobility cup was designed to improve prosthetic stability without increasing loosening rates, but it is unclear whether the risk of dislocation is reduced.


OBJECTIVE
We therefore determined: (1) if the rate of dislocation in isolated acetabular revisions is lower with a dual-mobility cup, (2) implant survival, (3) patient function, and (4) radiographic incidence of migration, loosening, and osteolysis.


METHODS
We prospectively followed 33 selected patients who underwent isolated acetabular revisions with a minimum of 2 years' followup (mean, 3 years; range, 2-5 years). In 24 patients a stainless steel dual-mobility cup was cemented into an antiprotrusio cage, whereas in nine we used a hyaluronan dual-mobility revision cup with a foramen hook and superior and posterior flanges screw fixations. We determined Harris hip (HHS) and WOMAC scores and examined radiographs for migration, loosening, and osteolysis.


RESULTS
There were no dislocations. Survivorship rates of the femoral and acetabular components were 97% at 5 years; the rerevision rate for any reason was 3%. At last followup, the mean HHS increased from 48 points preoperatively to 86 points. No patients had progressive osteolysis, component migration, or loosening on radiographs.


CONCLUSIONS
In this select group of isolated acetabular revisions, our data suggest the use of a dual-mobility cup reduced the risk of dislocation without increasing loosening from 2 to 5 years.


METHODS
Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.
First Orthopaedic Clinic, Department of Special Surgical Science, University of Florence, CTO-Largo Palagi 1, 50139 Florence, Italy. civi@mclink.it
Roberto
R
Civinini
Christian
C
Carulli
Fabrizio
F
Matassi
Lorenzo
L
Nistri
Massimo
M
Innocenti
D000077:Acetabulum / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D001863:Bone Screws; D005260:Female; D005548:Foreign-Body Migration / Q000209:etiology; D006617:Hip Dislocation / Q000209:etiology / Q000517:prevention & control*; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D006820:Hyaluronic Acid; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D010014:Osteolysis / Q000209:etiology; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D020127:Recovery of Function; D012086:Reoperation; D013997:Time Factors; D016896:Treatment Outcome
D006820:Hyaluronic Acid