Abstract
Modular dual mobility (MDM) prostheses in which a cobalt–chromium liner is inserted
into a titanium acetabular shell have the potential for corrosion. This has raised
concern. While these constructs have been shown to effectively reduce the risk of
dislocation in revision and high-risk primary total hip arthroplasty (THA), previous
studies have been limited by the length of follow-up. The purpose of the study is
to review the mid-term clinical outcomes of MDM implants with a minimum of 5-year
follow-up. A retrospective, observational study was conducted on all consecutive patients
who underwent THA with a MDM implant from June 2011 and March 2017 at an urban, tertiary
academic medical center. Descriptive statistics were used to describe baseline patient
characteristics. Primary endpoints included revision rates, dislocations rates, and
implant component survivorship. Implant survival was analyzed using the Kaplan–Meier
method. A total of 92 cases (61 primary, 31 revision) underwent THA with a MDM implant
at an average follow-up of 6.90 ± 1.48 years (range: 5.01–10.53 years). The mean patient
age at the time of surgery was 58.20 ± 11.85 years. Six patients were revised (6.5%,
6/92), two for periprosthetic joint infection (2.2%, 2/92), one due to aseptic loosening
(1.1%, 1/92), one due to periprosthetic fracture (1.1%, 1/92), and the remaining two
for metallosis (2.2%, 2/92). Kaplan–Meier survivorship analysis showed a 93.5% survival
rate for all-cause revisions and 98.9% survival for acetabular component revision.
MDM components reliably decrease the risk of dislocation after THA. However, the occurrence
of two revisions due to metallosis demonstrates the necessity for continued surveillance
in this cohort. Larger trials with long-term follow-up may be required to further
elucidate the long-term outcomes and performance of these bearings.
Keywords
modular dual mobility - metallosis - total hip arthroplasty
