The effect of CT scanning and metal artefact reduction strategies on measuring knee implant displacement: iMAR - helpful or harmful?

Background: A recent development in diagnosing total knee arthroplasty (TKA) tibial component loosening uses Computed Tomography (CT) images of loaded knees to assess implant micro-motion, but metal artefacts can affect reliability. This study investigates the impact of increased exposure and tube voltage, iterative metal artefact reduction reconstruction (iMAR), Sn-filtering and an extended CT scale (ECTS), compared to a standard knee CT protocol on load-induced implant displacement measurement.

Method: CT scans of a fresh frozen cadaver leg with a TKA were acquired using a standard protocol and four metal artefact reduction strategies: Increased exposure/tube voltage, iMAR, Sn-filtering, and ECTS reconstruction.

Operator variation in applying a knee loading device for evaluation of tibial component loosening in total knee arthroplasty.

Background: A CT-based method has been developed to aid diagnosis of aseptic loosening of the tibial component by scanning the knee in a loading device, and subsequent 3D-image analysis to quantify component displacement. This study evaluated the effect of operator differences in applying the loading device on the component displacement variables, using two image analysis protocols.

Methods: Sixteen subjects underwent repeated CT examinations with valgus and varus loading.

Non-invasive quantitative assessment of induced component displacement can safely and accurately diagnose tibial component loosening in patients: A prospective diagnostic study.

Purpose: Aseptic loosening often requires major, expensive and invasive revision surgery. Current diagnostic modalities merely show indirect signs of loosening. A recent proof of concept study proposed a non-invasive technique for the quantitative and visual assessment of implant movement as a diagnostic aid for tibial component loosening.