Update on Imaging of Knee Arthroplasties: Normal Findings and Hardware Complications

Abstract

Total knee arthroplasty (TKA) is the most common joint replacement performed. This article reviews the normal appearance of TKA including the most common types of arthroplasties as well as complications. Common complications at the present time are infection, aseptic loosening, and instability. Rarer complications such as polyethylene wear, periprosthetic fracture, and soft tissue pathology are also discussed. Although the mainstay of imaging is radiographs, newer techniques in TKA imaging such as computed tomography and magnetic resonance imaging are also reviewed.

Clinics in diagnostic imaging (208)

“…(6) One of the most common causes of late TKR failure is aseptic loosening, which is postulated to result from cumulative mechanical stresses, osteolysis secondary to particle disease, poor bone stock or varying combinations of these factors. (7,8) Radiographic and CT findings of loosening include wide (> 2 mm) or progressively enlarging periprosthetic lucency, component migration and subsidence (Figs. 2 & 3).…”

“…from each other on radiography, and hence infection should always be considered when loosening is present. (7,8) Subsidence following TKR usually refers to 'sinking' or 'settling' of the tibial tray into the tibial plateau due to loss of bone substance beneath the tibial tray. This is more commonly observed in the medial tibial plateau, with subsequent varus malalignment of the knee joint ( Fig.…”

“…(7) Polyethylene liner wear is a frequent late complication of TKR, especially in patients with prostheses that have metal backing and non-congruent articular surfaces, although there have been improvements in polyethylene liner durability over the years. (7,8) Moderate to severe wear appears as obvious joint space narrowing, with progressive worsening varus or valgus deformity on knee radiographs during follow-up (Figs. 2 & 3).…”

“…This usually begins as a proliferative synovitis and progresses into a geographic osteolysis, which causes loosening of the implants. (6)(7)(8) Non-contrast CT may be considered for imaging evaluation when osteolysis is suspected, as it has greater sensitivity than radiography, allowing for accurate quantification of disease extent (Fig. 6).…”

“…This may be secondary to various factors, including improper prosthesis selection, ligament tears, imbalance of the stabilising soft tissue structures at surgery, polyethylene wear and implant migration. (6)(7)(8) Dislocation is the most serious manifestation (Fig. 7), but its prevalence has decreased to 0.15%-0.50% due to newer implant technology.…”