Imaging of Joint Replacements

It is an honor to serve as the guest editor of this issue of Seminars dedicated to joint replacements, a topic I truly enjoy, and the imaging of which I encounter every day at my institution on radiographs, MRI, computed tomography (CT), and sonography.

We open the issue with a chapter on the design and fixation of implants, which is key to understanding their imaging appearances in both normal and abnormal states. This is naturally followed by an article on the radiographic appearances of hip replacements. In addition, the field of biomechanics and materials science has created many combinations of bearing surfaces and modular components with the unintended consequences of man-made diseases such as adverse reactions to metal debris, polymeric wear, and osteolysis that are discussed in articles on MR imaging of the hip and knee.

I view this current issue as a sequel to a similar one I edited in 2006, but that previous issue seems almost primitive now. In the early 2000s, advanced imaging of joint replacements was just starting to be investigated, and that issue of Seminars had individual articles on MRI, CT, and ultrasound. Today, these modalities have become so integral to the evaluation of joint replacements that each of these imaging techniques has been incorporated into each article of the current issue as routine practice. The development of MRI metal artifact reduction sequences like multiacquisition variable-resonance image combination (MAVRIC) and slice encoding for metal artifact correction (SEMAC) have revolutionized the field. In fact, the use of MRI for the evaluation of joint replacements has become an everyday event at our institution, driven by the field-leading work of Dr. Hollis Potter, who coauthors the article on MRI of knee replacements.

This multimodality approach is nicely demonstrated in the article on shoulder replacements, in which we see the radiographic, sonographic, CT, and MRI appearances of various types of these replacements.

In the previous issue we did not have dedicated articles on elbow or ankle replacements, but these fields have advanced to the point that radiologists are often seeing replacements of these joints. We need to know how they are supposed to look normally, how they fail, and what the appearances of failure are.

What a difference a decade makes!