 Introduction/Background It has been approximately 60 years since Sir John Charnley introduced the modern era of hip replacement surgery [1]. Approximately 370,000 primary total hip arthroplasties (THAs) were performed in the United States in 2014 [2]. Sloan et al [2] estimated that the volume of primary THAs would increase to 635,000 procedures annually by 2030. Over the years, modifications have been made to attempt to decrease complications such as loosening and wear with additional fixation techniques (eg, osseointegration) and articular surfaces (eg, metal on highly cross-linked polyethylene, antioxidant doped polyethylene liners, metal-on-metal [MoM], ceramic on polyethylene, and ceramic on ceramic articulations) [3-5]. The most common causes for surgical revision of THA from 2012 to 2019 as reported in the American Academy of Orthopaedic Surgeons American Joint Replacement Registry were infection and inflammatory reaction (19.3%), instability (17.4%), and aseptic loosening (15.8%) [15-17]. Wear or osteolysis was the cause for revision in 7.5%. The imaging studies used to follow uncomplicated primary hip prostheses and to assess several prosthesis-related complications are reviewed. Separate discussions pertinent to imaging of MoM prostheses are included. Special Imaging Considerations Ultrasound (US): US has been used for assessment of soft tissues adjacent to hip arthroplasties and, in contrast to MRI and CT, is not affected by prosthetic artifacts. US may be limited in its ability to assess deep soft tissues. Metal artifact reduction sequences (MARS)-MRI: MARS-MRI enable soft tissues around the prosthetic hip such as the pseudocapsule, tendons, and neurovascular structures to be assessed. Reviews of some MARS-MRI techniques are available in the literature [18-21]. Metal artifact reduction (MAR)-CT: Metallic hip prostheses, particularly cobalt chrome components, produce artifacts on CT scanning that can obscure adjacent structures.
Imaging after Total Hip Arthroplasty PCAs.  Introduction/Background It has been approximately 60 years since Sir John Charnley introduced the modern era of hip replacement surgery [1]. Approximately 370,000 primary total hip arthroplasties (THAs) were performed in the United States in 2014 [2]. Sloan et al [2] estimated that the volume of primary THAs would increase to 635,000 procedures annually by 2030. Over the years, modifications have been made to attempt to decrease complications such as loosening and wear with additional fixation techniques (eg, osseointegration) and articular surfaces (eg, metal on highly cross-linked polyethylene, antioxidant doped polyethylene liners, metal-on-metal [MoM], ceramic on polyethylene, and ceramic on ceramic articulations) [3-5]. The most common causes for surgical revision of THA from 2012 to 2019 as reported in the American Academy of Orthopaedic Surgeons American Joint Replacement Registry were infection and inflammatory reaction (19.3%), instability (17.4%), and aseptic loosening (15.8%) [15-17]. Wear or osteolysis was the cause for revision in 7.5%. The imaging studies used to follow uncomplicated primary hip prostheses and to assess several prosthesis-related complications are reviewed. Separate discussions pertinent to imaging of MoM prostheses are included. Special Imaging Considerations Ultrasound (US): US has been used for assessment of soft tissues adjacent to hip arthroplasties and, in contrast to MRI and CT, is not affected by prosthetic artifacts. US may be limited in its ability to assess deep soft tissues. Metal artifact reduction sequences (MARS)-MRI: MARS-MRI enable soft tissues around the prosthetic hip such as the pseudocapsule, tendons, and neurovascular structures to be assessed. Reviews of some MARS-MRI techniques are available in the literature [18-21]. Metal artifact reduction (MAR)-CT: Metallic hip prostheses, particularly cobalt chrome components, produce artifacts on CT scanning that can obscure adjacent structures.