Background: The evaluation of periprosthetic osteolysis in patients
who have had a total hip arthroplasty is challenging, and traditional imaging
techniques, including magnetic resonance imaging and computerized tomography,
are limited by metallic artifact. The purpose of the present study was to
investigate the use of modified magnetic resonance imaging techniques
involving commercially available software to visualize periprosthetic soft
tissues, to define the bone-implant interface, and to detect the location and
extent of osteolysis.
Methods: Twenty-eight hips in twenty-seven patients were examined to
assess the extent of osteolysis (nineteen hips), enigmatic pain (five),
heterotopic ossification (two), suspected tumor (one), or femoral nerve palsy
(one). The results were correlated with conventional radiographic findings as
well as with intraoperative findings (when available).
Results: Magnetic resonance imaging demonstrated the bone-implant
interface and the surrounding soft-tissue envelope in all hips. Radiographs
consistently underestimated the extent and location of acetabular osteolysis
when compared with magnetic resonance imaging. Magnetic resonance imaging also
disclosed radiographically occult extraosseous soft-tissue deposits that were
similar in signal intensity to areas of osteolysis, demonstrated the
relationship of these deposits to adjacent neurovascular structures, and
allowed further visualization of hypertrophic synovial deposits that
accompanied the bone resorption in twenty-five of the twenty-eight hips.
Conclusions: Magnetic resonance imaging is effective for the
assessment of the periprosthetic soft tissues in patients who have had a total
hip arthroplasty. While not indicated for every patient who has pain at the
site of an arthroplasty, these techniques can be effective for the evaluation
of the surrounding soft-tissue envelope as well as intracapsular synovial
deposits and are more effective than radiographs for the detection and
evaluation of osteolysis, thus aiding in clinical management.
Level of Evidence: Diagnostic study, Level III-1 (study
of nonconsecutive patients [no consistently applied reference
"gold" standard]). See Instructions to Authors for a complete
description of levels of evidence.