Extensive Periprosthetic Lucencies and Acetabular Protrusio in a Hip Hemiarthroplasty: A Case Report.

Primary hip arthroplasties are common orthopedic procedures performed to replace a damaged or arthritic hip joint using prosthetic units. In the past several decades, the incidence of primary hip arthroplasty procedures has increased significantly. For many, the procedure provides long-term relief. However, a variety of complications can also arise, such as neurovascular injury, leg length discrepancy, infection, osteolysis, loosening, heterotopic ossification, and pseudobursa formation. Of these, several can result in failed hip arthroplasty, including aseptic loosening with osteolysis, infection, and instability. Imaging aids in differentiation between these causes of failed hip arthroplasty, which is crucial as there can be significant overlap in their clinical presentation. This case report demonstrates a 74-year-old patient who had a remote history of left hip hemiarthroplasty that presented with severe periprosthetic lucencies and acetabular protrusio after a fall. The top of the differential diagnosis included aseptic loosening with periprosthetic osteolysis secondary to particle disease, periprosthetic joint infection, and traumatic fracture. Imaging played a vital role in achieving an accurate diagnosis and guiding management. Modalities commonly utilized in the workup of arthroplasty complications include conventional radiography, computed tomography (CT), magnetic resonance imaging (MRI), and nuclear medicine techniques such as three-phase bone scans, white blood cell (WBC) scans, and fluorodeoxyglucose-positron emission tomography (FDG-PET). This article will discuss the importance of these modalities as part of a multifaceted approach to accurately diagnose arthroplasty complications.