Abstract
BackgroundRoentgen stereophotogrammetric analysis (RSA) is used to measure early prosthetic migration and to predict future implant failure. RSA has several disadvantages, such as the need for perioperatively inserted tantalum markers. Therefore, this study evaluates low-field MRI as an alternative to RSA. The use of traditional MRI with prostheses induces disturbing metal artifacts which are reduced by low-field MRI. The purpose of this study is to assess the feasibility to use low-field (0.25 Tesla) MRI for measuring the precision of zero motion. This was assessed by calculating the virtual prosthetic motion of a zero-motion prosthetic reconstruction in multiple scanning sessions. Furthermore, the effects of different registration methods on these virtual motions were tested.ResultsThe precision of zero motion for low-field MRI was between 0.584 mm and 1.974 mm for translation and 0.884° and 3.774° for rotation. The manual registration method seemed most accurate, with μ ≤ 0.13 mm (σ ≤ 0.931 mm) for translation and μ ≤ 0.15° (σ ≤ 1.63°) for rotation.ConclusionLow-field MRI is not yet as precise as today’s golden standard (marker based RSA) as reported in the literature. However, low-field MRI is feasible of measuring the relative position of bone and implant with comparable precision as obtained with marker-free RSA techniques. Of the three registration methods tested, manual registration was most accurate. Before starting clinical validation further research is necessary and should focus on improving scan sequences and registration algorithms.
Highlights
Roentgen stereophotogrammetric analysis (RSA) is used to measure early prosthetic migration and to predict future implant failure
The precision of zero motion for low-field MRI was between 0.584 mm and 1.974 mm for translation and 0. 884° and 3.774° for rotation
Low-field MRI is feasible of measuring the relative position of bone and implant with comparable precision as obtained with marker-free RSA techniques
Summary
Roentgen stereophotogrammetric analysis (RSA) is used to measure early prosthetic migration and to predict future implant failure. (Valstar et al 2002) Roentgen stereophotogrammetric analysis (RSA) is the golden standard in measuring early component migration.(Kärrholm et al 1997; Vrooman et al 1998; Kärrholm et al 2006) Currently, the clinically obtained accuracy of conventional RSA varies between 0.05 and 0.5 mm for translation and 0.15° to 1.15° for rotation (95% confidence intervals (CI)). MRI has some characteristics that make it less suitable for bone and prosthetic imaging: it provides lower bone contrast than CT; it suffers from spatial and geometric distortions, field inhomogeneity, and metal artefacts.(Doran et al 2005; Vandevenne et al 2007; Moro-oka et al 2007) (Fig. 1a) Disadvantages of MRI may be partly overcome by the use of low-field MRI. Low-field MRI (< 0.5 T) is rarely used in clinical practice, it is considered to be highly suitable for musculoskeletal imaging. (Ghazinoor et al 2007; Lee et al 2013)
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