Background: The intraoperative occurrence of an acetabular fracture
is a rare complication of primary total hip arthroplasty. Previous reports
have lacked a sufficiently large number of subjects to allow for an analysis
of the causes and appropriate treatment of this problem.
Methods: Between 1990 and 2000, 7121 primary total hip
arthroplasties were performed at our institution. We retrospectively reviewed
the records in our Total Joint Registry and found that twenty-one patients
(twenty-one hips) had sustained an intraoperative acetabular fracture.
Nineteen of these patients (nineteen hips) had been followed until revision or
for a minimum of two years (mean duration of follow-up, forty-four months). We
evaluated the anatomic location, cause, treatment, and outcome of the
fractures. Acetabular component designs were categorized as modular,
nonmodular (monoblock), true hemispherical, or elliptical, and then each
design was analyzed for fracture risk.
Results: No fractures occurred in association with cemented
acetabular components. The fracture rate associated with uncemented components
was 0.4%. In seventeen hips, the acetabular component was judged to be stable
despite the detection of a fracture and the cup was retained. In four hips,
the original cup was not stable and therefore was replaced with a design that
allowed for supplemental screw fixation. All fractures united, and all cups
demonstrated osseous ingrowth at the time of the most recent follow-up.
Elliptical monoblock cups were associated with a significantly higher fracture
rate than were elliptical modular cups (p < 0.0001) and hemispherical
modular cups (p < 0.0001). There was no significant difference between
elliptical modular and hemispherical modular components with regard to the
Conclusions: Acetabular fracture during primary total hip
arthroplasty is a rare complication of acetabular fixation without cement. In
the present series, retention of a stable cup was associated with uneventful
osseous ingrowth and excellent early-term outcomes. We found a high rate of
fracture in association with the use of monoblock elliptical components.
Level of Evidence: Therapeutic Level III. See
Instructions to Authors for a complete description of levels of evidence.