Model-based RSA of a femoral hip stem using surface and geometrical shape models.
Roentgen stereophotogrammetry (RSA) is a highly accurate three-dimensional measuring technique for assessing micromotion of orthopaedic implants. A drawback is that markers have to be attached to the implant. Model-based techniques have been developed to prevent using special marked implants. We compared two model-based RSA methods with standard marker-based RSA techniques. The first model-based RSA method used surface models, and the second method used elementary geometrical shape (EGS) models. We used a commercially available stem to perform experiments with a phantom as well as reanalysis of patient RSA radiographs. The data from the phantom experiment indicated the accuracy and precision of the elementary geometrical shape model-based RSA method is equal to marker-based RSA. For model-based RSA using surface models, the accuracy is equal to the accuracy of marker-based RSA, but its precision is worse. We found no difference in accuracy and precision between the two model-based RSA techniques in clinical data. For this particular hip stem, EGS model-based RSA is a good alternative for marker-based RSA.
Kaptein
Bart L
BL
Department of Orthopaedics, Leiden University Medical Center, The Netherlands. B.L.Kaptein@lumc.nl
Valstar
Edward R
ER
Spoor
Cees W
CW
Stoel
Berend C
BC
Rozing
Piet M
PM
D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D005269:Femur / Q000601:surgery*; D006622:Hip Prosthesis / Q000592:standards*; D006801:Humans; D066298:In Vitro Techniques; D008962:Models, Theoretical; D010780:Photogrammetry; D011474:Prosthesis Design; D015203:Reproducibility of Results; D013499:Surface Properties