Model‐based RSA is suitable for clinical trials on the glenoid component of reverse total shoulder arthroplasty

Abstract

This study aims to validate model-based radiostereometric analysis (RSA) on the glenoid component of reversed total shoulder arthroplasty. We compared two different modalities of model-based RSA, elementary geometrical shapes and reversed engineering. We also explored two different ways to position the patient to obtain different projections of the implant, the hip-position (transversal) and shoulder-position (sagittal). Phantom accuracy was determined by performing nine translations (x, y, z) and five rotations (x, y, z), and expressed as the mean difference between RSA measurements and micrometer values. Precision was measured using 12 double examinations of the phantom and 19 in patients, and expressed as1.96 × standard deviations of the paired differences between double examinations. The accuracy was high for both modalities, but rotation around the symmetrical axis of the implant could not be measured using reversed engineering. Clinical precision ranged from 0.13 to 0.25 mm for translations, and 0.4° to 0.7° for rotations, using reversed engineering. For elementary geometrical shapes, the precision ranged from 0.18 to 0.34 mm for translations, and 0.8° to 1.8° for rotations. The hip-position was abandoned due to poor implant visualization. Model-based RSA on the glenoid component of reversed total shoulder arthroplasty has a high precision and accuracy, comparable to RSA results on hips and knees. Patient positioning is vital for obtaining adequate results. We found that reversed engineering was the more reliable method, and recommend reversed engineering as the method of choice for further clinical RSA investigation of the glenoid component of reversed total shoulder arthroplasty. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Stable glenoid component of reverse total shoulder arthroplasty at 2 years as measured with model-based radiostereometric analysis (RSA)

“…Little RSA research has been published on this implant. Apart from a methodological study including precision measurements in patients (Fraser et al 2018), our study seems to be the only clinical RSA stability study on reverse shoulder arthroplasty. Other shoulder RSA studies have involved a phantom glenoid component (Van de Kleut et al 2018), ana-tomic shoulder arthroplasties or resurfacing implants (Nagels et al 2002, Rahme et al 2004, 2006, Nuttall et al 2009, Sköldenberg and Odquist 2011, Stilling et al 2012, Mechlenburg et al 2014, Streit et al 2015.…”

“…In this clinical RSA study of the glenoid component of reverse TSA we have used model-based RSA technology, and specifically the reversed engineering (RE) RSA modality. A published method study (Fraser et al 2018) supplied the framework, particularly with regard to how patients were positioned for RSA examinations, which RSA software modality was used, and the clinical precision of the RE model-based RSA on this implant, obtained by double examinations of 15 patients included in the current study.…”

“…A published method study (Fraser et al. 2018 ) supplied the framework, particularly with regard to how patients were positioned for RSA examinations, which RSA software modality was used, and the clinical precision of the RE model-based RSA on this implant, obtained by double examinations of 15 patients included in the current study.…”

“…Model-based RSA has the advantage over traditional marker-based RSA of not having to alter implants by attaching markers, and the clinical precision of model-based RSA on the glenoid component is known (Fraser et al. 2018 ). With increased use, sparse long-term evidence, and with “notching” as the backdrop, we performed a stability analysis of the glenoid component of reversed TSA, using model-based RSA.…”

Model-Based Roentgen Stereophotogrammetric Analysis Using Elementary Geometrical Shape Models: Reliability of Migration Measurements for an Anatomically Shaped Femoral Stem Component

“…However, when applying RE models to a large number of implants with different sizes or variants (which is a common situation in clinical studies), it can result in a considerable expense. EGS model is a potential alternative when CAD/RE model is not available [51].…”