MR Imaging of Hip Arthroplasty Implants

Abstract

Hip arthroplasty has become the standard treatment for end-stage hip disease, allowing pain relief and restoration of mobility in large numbers of patients; however, pain after hip arthroplasty occurs in as many as 40% of cases, and despite improved longevity, all implants eventually fail with time. Owing to the increasing numbers of hip arthroplasty procedures performed, the demographic factors, and the metal-on-metal arthroplasty systems with their associated risk for the development of adverse local tissue reactions to metal products, there is a growing demand for an accurate diagnosis of symptoms related to hip arthroplasty implants and for a way to monitor patients at risk. Magnetic resonance (MR) imaging has evolved into a powerful diagnostic tool for the evaluation of hip arthroplasty implants. Optimized conventional pulse sequences and metal artifact reduction techniques afford improved depiction of bone, implant-tissue interfaces, and periprosthetic soft tissue for the diagnosis of arthroplasty-related complications. Strategies for MR imaging of hip arthroplasty implants are presented, as well as the imaging appearances of common causes of painful and dysfunctional hip arthroplasty systems, including stress reactions and fractures; bone resorption and aseptic loosening; polyethylene wear-induced synovitis and osteolysis; adverse local tissue reactions to metal products; infection; heterotopic ossification; tendinopathy; neuropathy; and periprosthetic neoplasms. A checklist is provided for systematic evaluation of MR images of hip arthroplasty implants. MR imaging with optimized conventional pulse sequences and metal artifact reduction techniques is a comprehensive imaging modality for the evaluation of the hip after arthroplasty, contributing important information for diagnosis, prognosis, risk stratification, and surgical planning.

MR Imaging of Knee Arthroplasty Implants

“…As with hip arthroplasty (13), the projectional, two-dimensional nature of conventional radiography of total knee arthroplasty is often insensitive for accurate visualization of the three-dimensional extent of bone loss (31,32). CT with postprocessing by using metal-induced beamhardening suppression can be more accurate than radiography, as has been shown for pelvic osteolysis (33).…”

“…A 2007 study calculated that improving implant longevity, increasing patient life expectancy, implantation at younger patient age, and the functional demands of the elderly population would contribute to a projected 673% increase in knee arthroplasty from 450,000 annual procedures in 2005 to 3.48 million by 2030 (5). large differences in the magnetic susceptibility constant between the metallic implant components and the surrounding tissue (11). These field variations depend on the strength of the external magnetic field as well as on the size, shape, and type of metal being imaged (12).…”

“…These field variations depend on the strength of the external magnetic field as well as on the size, shape, and type of metal being imaged (12). Substantial reductions in artifacts with superior delineation of the surrounding soft-tissue envelope have been achieved at 1.5 T (13).…”

Early Lessons From a Worldwide, Multicenter, Followup Study of the Recalled Articular Surface Replacement Hip System

“…We theorized that the location of ALTRs would be related to the initial violation of the joint capsule and surrounding soft tissues and hence the focus on the surgical approach. Fritz and coworkers [7] suggested that disruption of the pseudocapsule in progressive ALTRs usually occurs at the posterolateral attachment. This becomes intuitive in light of the current findings when we consider that most hip arthroplasties are performed from the posterior approach.…”

“…Previous incision patterns into the hip may play a role by providing a path of least resistance for increased intracapsular pressure. Both anterior and posterior disruption of the pseudocapsule have been reported with posterior disruption possibly more common [7].…”