MRI after patellofemoral replacement: the component-bone interface and rotational alignment.

Abstract

In an earlier paper, it was shown that tailored magnetic resonance imaging (MRI) allows for reproducible analysis of the preserved knee joint structures after patellofemoral replacement (PFR). This pilot study investigates to what degree MRI could produce reliable assessment of the implant-bone interface of femoral and patellar components and rotational alignment following PFR. MRI tailored for reduction of metallic artefacts was performed in seven patients who had undergone PFR. Two independent investigators evaluated the implant-bone interface at femoral and patellar components and the rotational alignment of the femoral component. They also assessed their degree of confidence in evaluation using a five-point scale. The inter-observer reliability was determined. Implant-induced MRI artefact was barely observed and there was no interference with component-bone interface evaluation. There was excellent inter-observer reliability, inter-observer agreement, and confidence for the implant-bone interface at femoral and patellar components and for rotational alignment. The applied score for the interface was found to be reliable. Tailored MRI allows reproducible analysis of the implant-bone interface and of rotational alignment of the femoral component in patients who have had PFR. It might prove helpful in the assessment of painful PFR.