Inflammatory Pseudotumor After Total Hip Arthroplasty-An Increasingly Recognized Complication.

Inflammatory pseudotumor (IP) is an increasingly recognized etiological factor in the failure of total hip arthroplasty (THA). It is a non-neoplastic, non-infectious mass encircling a hip prosthesis following arthroplasty and may appear as cystic, solid, or mixed tissue. Although initially associated with metal-on-metal (MoM) bearing surfaces, IP formation can also occur with other bearing types. Recognized risk factors include female sex, specific genetic predispositions, MoM bearings, large femoral head size, modular femoral stem designs, elevated metal ion levels, and wear debris from polyethylene components. IP contributes to THA failure through both mechanical and inflammatory mechanisms, often leading to pain, instability, or implant loosening. Diagnosis relies heavily on imaging modalities, including plain radiographs, ultrasound, CT, and MRI with metal artifact reduction sequences (MARS-MRI), which help delineate the extent and characteristics of IP lesions. A multimodal imaging approach is essential for accurate assessment and surgical planning. Management strategies are guided by clinical presentation and radiographic findings, such as IP size and anatomical location, ranging from close observation in asymptomatic cases to revision surgery in symptomatic or progressive disease. IP is therefore an important, imaging-detectable cause of THA failure, and awareness of its presentation and diagnostic features is critical for timely intervention and improved patient outcomes.