Prospective and longitudinal evolution of postoperative periprosthetic findings on metal artifact–reduced MR imaging in asymptomatic patients after uncemented total hip arthroplasty

OBJECTIVE: To prospectively assess the evolution of postoperative MRI findings in asymptomatic patients after total hip arthroplasty (THA) over 24 months (mo). METHODS: This prospective cohort study included 9 asymptomatic patients (56.7 ± 15.0 years) after THA. Metal artifact–reduced 1.5-T MRI was performed at 3, 6, 12, and 24 mo after surgery. The femoral stem and acetabular cup were assessed by two readers for bone marrow edema (BME), periprosthetic bone resorption, and periosteal edema in addition to periarticular soft tissue edema and joint effusion. RESULTS: BME was common around the femoral stem in all Gruen zones after 3 mo (range: 50–100%) and 6 mo (range: 33–100%) and in the acetabulum in DeLee and Charnley zone II after 3 mo (100%) and 6 mo (33%). BME decreased substantially after 12 mo (range: 0–78%) and 24 mo (range: 0–50%), may however persist in particular in Gruen zones 1 + 7. Periosteal edema along the stem was common 3 mo postoperatively (range: 63–75%) and rare after 24 mo: 13% only in Gruen zones 2 and 5. Twelve months and 24 mo postoperatively, periprosthetic bone resorption was occasionally present around the femoral stem (range: 11–33% and 13–38%, respectively). Soft tissue edema occurred exclusively along the surgical access route after 3 mo (100%) and 6 mo (89%) and never at 12 mo or 24 mo (0%). CONCLUSION: Around the femoral stem, BME (33–100%) and periosteal edema (0–75%) are common until 6 mo after THA, decreasing substantially in the following period, may however persist up to 24 mo (BME: 0–50%; periosteal edema: 0–13%) in few non-adjoining Gruen zones. Soft tissue edema along the surgical access route should have disappeared 12 mo after surgery.