L Lindgren1, P B Jørgensen2, R M S Mørup3, M Jensen4, L Rømer5, B Kaptein6, M Stilling7. 1. Department of Radiology, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus, Denmark. Electronic address: larsli@rm.dk. 2. Orthopedic Research Unit, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus, Denmark. Electronic address: pbjr@clin.au.dk. 3. Orthopedic Research Unit, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus, Denmark. Electronic address: rikke.morup@clin.au.dk. 4. Department of Radiology, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus, Denmark. Electronic address: Mark.Jensen@rsyd.dk. 5. Department of Radiology, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus, Denmark. Electronic address: lone.roemer@dadlnet.dk. 6. Biomechanics and Imaging Group (BIG), Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, the Netherlands. Electronic address: B.L.Kaptein@lumc.nl. 7. Orthopedic Research Unit, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus, Denmark; Department of Clinical Medicine, Aarhus University, Palle Juul-Jensens Boulevard 99, 8200, Aarhus, Denmark. Electronic address: maiken.stilling@clin.au.dk.
Abstract
INTRODUCTION: Despite protocols, patients are not positioned exactly alike at radiostereometric (RSA) follow-up examinations, and it is unknown how much variation is tolerable. We report precision for optimal and extreme position differences from a phantom hip-study, and clinical precision of hip-RSA. METHODS: A femoral stem with 3 bead-towers was fixed in a saw bone with bone-markers (phantom), and series of RSA examinations within optimal (5 × 5 cm and 5°) and extreme (20 × 30 cm and 30°) phantom positions were obtained. Double-examination RSA of 12 patients with the same femoral stem type were analyzed. Both model-based (CAD) and marker-based (MM) analysis was used. Precision was reported as standard deviation of differences. RESULTS: Precision for translations in the optimal and extreme phantom position were below 0.06 mm and 0.02 mm for MM analysis, and below 0.05 mm and 0.18 mm for CAD analysis, respectively. Precision for rotations in the optimal and extreme phantom rotation were below 0.18° and 0.26° for MM analysis, and below 0.34° and 0.52° for CAD analysis, respectively. Clinical precision was 0.29 mm and 0.44° for MM analysis, and 0.40 mm and 1.59° for CAD analysis. CONCLUSION: Extreme differences in patient position during RSA examination negatively affects precision, and CAD model-analysis was more sensitive than MM analysis. Longitudinal translation and rotation about the long stem-axis are the effect parameters which are most affected by position and rotation changes, and also the best indicators of implant loosening. IMPLICATIONS FOR PRACTICE: Based on our research, we recommend that similar patient positioning between follow-up RSA examinations is debated and prioritized.
INTRODUCTION: Despite protocols, patients are not positioned exactly alike at radiostereometric (RSA) follow-up examinations, and it is unknown how much variation is tolerable. We report precision for optimal and extreme position differences from a phantom hip-study, and clinical precision of hip-RSA. METHODS: A femoral stem with 3 bead-towers was fixed in a saw bone with bone-markers (phantom), and series of RSA examinations within optimal (5 × 5 cm and 5°) and extreme (20 × 30 cm and 30°) phantom positions were obtained. Double-examination RSA of 12 patients with the same femoral stem type were analyzed. Both model-based (CAD) and marker-based (MM) analysis was used. Precision was reported as standard deviation of differences. RESULTS: Precision for translations in the optimal and extreme phantom position were below 0.06 mm and 0.02 mm for MM analysis, and below 0.05 mm and 0.18 mm for CAD analysis, respectively. Precision for rotations in the optimal and extreme phantom rotation were below 0.18° and 0.26° for MM analysis, and below 0.34° and 0.52° for CAD analysis, respectively. Clinical precision was 0.29 mm and 0.44° for MM analysis, and 0.40 mm and 1.59° for CAD analysis. CONCLUSION: Extreme differences in patient position during RSA examination negatively affects precision, and CAD model-analysis was more sensitive than MM analysis. Longitudinal translation and rotation about the long stem-axis are the effect parameters which are most affected by position and rotation changes, and also the best indicators of implant loosening. IMPLICATIONS FOR PRACTICE: Based on our research, we recommend that similar patient positioning between follow-up RSA examinations is debated and prioritized.
Authors: Maciej Okowinski; Mette Holm Hjorth; Sebastian Breddam Mosegaard; Jonathan Hugo Jürgens-Lahnstein; Stig Storgaard Jakobsen; Poul Hedevang Christensen; Søren Kold; Maiken Stilling Journal: Bone Jt Open Date: 2021-12