Background: Investigation of polyethylene liner movement in total hip arthroplasty requires bead-marking for radiographic visibility of the liner. However, occlusion of markers poses a challenge... Show moreBackground: Investigation of polyethylene liner movement in total hip arthroplasty requires bead-marking for radiographic visibility of the liner. However, occlusion of markers poses a challenge for marker registration in radiographs.Methods: The polyethylene of a dual mobility acetabular system was marked with twelve 1-mm tantalum markers (four groups of three markers) using a custom-made drill guide. Liner motion in a phantom and a patient was investigated with dynamic radiostereometry analysis (dRSA) at 1-year follow-up and static radiostereometry analysis (sRSA) postoperatively and at 1- and 2-year follow-up. A combined marker configuration (CMC) model was calculated from the registered positions of the liner markers and the femoral head in several images. Furthermore, the CMC model and the theoretic marker positions from computer-assisted models of the drill guide were combined in a hybrid model.Results: The CMC model included eleven markers in the phantom and nine markers in the patient, which was sufficient for dRSA. Liner movement in the phantom followed liner contact with the femoral neck, while liner movement in the patient was independent. The hybrid model was necessary to determine liner orientation in sRSA recordings, which clearly changed from postoperative to 1- and 2-year follow-up even though the patient was positioned similarly.Conclusion: Polyethylene liner motion in dual mobility hip prosthesis can be assessed with CMC models in dRSA recordings. In sRSA, the liner position between follow-ups is unpredictable and analysis requires inclusion of all markers in the model, accomplished with a hybrid marker model. Show less
The research in this thesis comprises two separate topics: single-molecule spectroscopy and resonant Raman spectroscopy. The first part concerns single-molecule (SM) spectroscopy on polyethylene ... Show moreThe research in this thesis comprises two separate topics: single-molecule spectroscopy and resonant Raman spectroscopy. The first part concerns single-molecule (SM) spectroscopy on polyethylene (PE) films. Ultra thin (200 nm) films of pure high density PE were produced by spincoating. By determining the position (accuracy 10 nm) and in-plane orientation (acc. 5 deg.) of single 2.3,8.9-dibenzanthanthrene (DBATT) guest molecules, by means of SM microscopy and spectroscopy respectively, we demonstrated that these thin PE films have a shish-kebab morphology, instead of the spherulitic morphology common in thicker PE films. We have also investigated the alignment process of individual quest chromophores by stretching thicker (50 um), low density PE films. Using SM spectroscopy, we have shown that individual guest chromophores are not better aligned along the stretch direction, as draw ratio increases. Instead alignment occurs suddenly, due to the destruction and (oriented) reformation of local crystalline regions and subsequent adsorption of chromophores. Each chromophore's orientation is determined by specific interactions with the oriented PE crystal surface. The second part of this thesis concerns a quantum-chemical analysis of the resonant Raman spectrum of the carotenoid spheroidene reconstituted in the photosynthetic reaction center (RC) of Rhodobacter sphaeroides. Our analysis demonstrates that spheroidene can adopt at least two cis forms in the RC. One of these has been conclusively shown to be the 15,15'-cis structure. Show less
