Radiostereometric analysis (RSA) is an accurate and precise radiographic method that can be used to measure micromotion of implants and study joint kinematics in vivo. A calibration cage with... Show moreRadiostereometric analysis (RSA) is an accurate and precise radiographic method that can be used to measure micromotion of implants and study joint kinematics in vivo. A calibration cage with radiopaque markers is used to calibrate the RSA images; however, the thickness (250 mm) of the calibration cage restricts the available area for the patient and equipment during RSA recordings. A thinner calibration cage would increase the recording area, facilitate handling of the cage, and ease integration of the cage with the RSA system. We developed a thinner calibration cage without compromise of accuracy and precision. First, we performed numerical simulations of an RSA system, and showed that the calibration cage thickness could be decreased to 140 mm maintaining accuracy and precision using 40 fiducial and 30 control markers. Second, we constructed a new calibration cage (NRT cage) according to the simulation results. Third, we validated the new calibration cage against two state-of-the-art calibration cages (Umeaa cage and Leiden cage) in a phantom study. All cages performed similar for marker-based analysis, except for y-rotation, where the Umeaa cage (SD = 0.064 mm) was less precise compared to the NRT (SD = 0.038 mm) and Leiden cages (0.042 mm) (p = .01). For model-based analysis the NRT cage had superior precision for translations (SD <= 0.054 mm) over the Leiden cage (SD <= 0.118 mm) and Umeaa cage (SD <= 0.093 mm) (p < .01). The combined study confirmed that the new and thinner calibration cage maintained accuracy and precision at the level of existing thicker calibration cages. Show less
The primary aim of this work was to develop novel model-based mJSW measurement methods using a 3D reconstruction and compare the accuracy and precision of these methods to conventional mJSW... Show moreThe primary aim of this work was to develop novel model-based mJSW measurement methods using a 3D reconstruction and compare the accuracy and precision of these methods to conventional mJSW measurement. This thesis contributed to the development, validation and clinical application of model-based mJSW measurements for the natural knee and for total knee prostheses. The majority of this work focusses on measuring linear wear of the total knee protheses by estimating the remaining insert thickness with the mJSW. Both in vivo and in vitro research shows that the application of model-based techniques can give a large improvement in measurement accuracy and precision. This applies for measurements based on both Röntgen Stereogrammetric Analysis (RSA) and standard radiographs. Secondary, this work investigated volumetric wear measurement and the effect of patient positioning on the measurement outcome. In conclusion, this work presents convincing evidence that the mJSW measurement accuracy and precision is improved using model-based measurement techniques in RSA images as well as in standard AP radiographs. The next steps towards clinical application are to improve the measurement software and to conduct further research on the influence of knee flexion and implant design on the reliability of mJSW as surrogate for the insert thickness. Show less
Seehaus, F.; Schwarze, M.; Florkemeier, T.; Lewinski, G. von; Kaptein, B.L.; Jakubowitz, E.; Hurschler, C. 2016
In mijn proefschrift heb ik onderzocht wat de invloed is van het gebruik van navigatie bij het plaatsen van een knieprothese. Hiervoor zijn drie onderzoeksvragen opgesteld en beantwoord. Allereerst... Show moreIn mijn proefschrift heb ik onderzocht wat de invloed is van het gebruik van navigatie bij het plaatsen van een knieprothese. Hiervoor zijn drie onderzoeksvragen opgesteld en beantwoord. Allereerst: leidt CAOS tot het nauwkeuriger plaatsen van een TKP? Op basis van de door mij gedane studies en analyse van de huidige literatuur concludeer ik dat juiste registratie tijdens CAOS essentieel is voor het bereiken van een goede stand van de TKP. Zolang hier nog onnauwkeurigheden in zitten leidt CAOS (nog) niet tot het nauwkeuriger plaatsen van de TKP, met name wat betreft de rotatie van de femurcomponent. Daarnaast heb ik onderzocht of CAOS leidt tot een juiste maatvoering van de TKP en patella tracking. Ik kom tot de conclusie dat men uit moet kijken voor het plaatsen van met name een te grote femurcomponent. De data die verkregen zijn middels het gebruik van de patella tracking module worden significant be_nvloed door de snelheid van bewegen van de knie en de zichtbaarheid van een markertree. Tot slot is bekeken wat de klinische en radiologische uitkomst is van een TKP geplaatst met CAOS. Hoewel er aanwijzingen zijn dat het aantal outliers wat betreft het alignment van de TKP met CAOS afneemt, kan er geen relatie aangetoond worden met de klinische uitkomst van de prothese. Momenteel is CAOS een bruikbare techniek voor onderzoeksdoeleinden, zoals de chirurgische techniek en kinematische analyse, en als onderwijsinstrument. Verder onderzoek is nodig om de exacte plaats van CAOS bij het plaatsen van TKP te bepalen. Tot die tijd moet men kritisch blijven wat betreft de toepassing van nieuwe technieken in de Orthopaedische Chirurgie, deze gefaseerd invoeren en de vraag stellen of iets een __tool__ of een __toy__ is. Show less
The focus of this thesis was if the in vivo kinematics of total knee prostheses was consistent with the kinematics intended by design and to determine the additional value of insert mobility and... Show moreThe focus of this thesis was if the in vivo kinematics of total knee prostheses was consistent with the kinematics intended by design and to determine the additional value of insert mobility and thus __the sense or nonsense__ of mobile-bearing knee prostheses. The added value of this thesis to the current literature is the integration of different measurement techniques. Fluoroscopy is combined with RSA and motion analysis techniques to fully understand the in vivo knee kinematics beyond which can be obtained by either technique alone. Results demonstrate that the integration of different measurement techniques was indeed of great value to comprehend the in vivo knee kinematics. Show less
The aim of the thesis was to to assess with accurate and objective methods the function and fixation of total knee prostheses with special emphasis on mobile bearing total knee designs. The mobile... Show moreThe aim of the thesis was to to assess with accurate and objective methods the function and fixation of total knee prostheses with special emphasis on mobile bearing total knee designs. The mobile bearing of a rotating platform design showed limited motion or no motion during a step-up task thereby nullifying the theoretical advantages of a mobile bearing prosthesis. Apatite coated implants show excellent mid-term Roentgen Stereophotogrammetric Analysis (RSA) results and offer some clinical advantages above cemented total knee arthroplasty. A prospective RSA study also revealed that the studied mobile bearing design is more predictable and forgiving with respect to micromotion of the tibial component than a posterior stabilised prosthesis. However, mobile bearing prostheses showed to be more demanding for the soft tissue structures surrounding the knee joint. The techniques used in gait analysis and fluoroscopy are sensitive for measurement errors. This restricts the applicability and interpretation of the results acquired when using these methods. In general one needs to be aware of the limitations of measurement tools since one needs accurate and objective methods to assess evidence about the clinical performance of (new) total knee prostheses. Show less
