Verifying a C-arm-based roentgen stereophotogrammetric analysis protocol for assessing tibial implant movement in total knee arthroplasty.

Roentgen stereophotogrammetric analysis (RSA) is the "gold standard" technique for measuring sub-millimetric relative motion between implant and bone to quantify post-operative implant migration over time. The vast majority of RSA studies addressing implant motion in knee replacements, however, have been conducted using expensive biplanar radiography systems and commercial software that are not readily available at many institutions. In this study, we evaluated the feasibility of performing RSA using ordinary, readily available C-arm fluoroscopes and open-source software to assess tibial component migration.We developed an assessment protocol using a Siemens Arcadis Orbic C-arm and the open-source XROMM software and evaluated its accuracy and precision through a series of phantom-based verification tests. The results were highly promising: accuracies were in the range of - 39 to 11 μm for translations and - 0.025 to 0.029° for rotations, while system precisions ranged between 16 to 27 μm for translations and 0.041 to 0.059° for rotations. This performance is comparable to specialized RSA systems reported in the literature. The proposed RSA protocol is therefore capable of accurately measuring the relative motion of knee replacement implants in phantom scenarios, which justifies further the development of the protocol towards use in prospective clinical assessments of new implant designs and surgical techniques.