<p>Loosening of implants is a frequent complication in orthopaedic surgery. The aim of this thesis was to evaluate hydroxyapatite coating of pedicle screws with mechanical and histological methods and to correlate the results with the radiological findings.</p><p>Hydroxyapatite (HA) coating of pedicle screws was investigated in experimental studies in sheep. Nine sheep were operated on with destabilising laminectomies at L2-L3 and L4-L5 and stabilised with pedicle screw instrumentations, where HA coated and uncoated screws were used in a randomised fashion. After both 6 and 12 weeks of implantation, the HA coated screws demonstrated a higher bone-to-implant contact and a higher amount of bone in the area close to the screw. The pull-out resistance, stiffness and total energy to failure was higher for the HA coated screws after 12 weeks of implantation.</p><p>HA coating of pedicle screws was examined in two clinical studies. In the first series, the patients were stabilised with pedicle screw instrumentations, where HA coated screws were used in either the upper or lower instrumented level in a randomised fashion. After 10-22 months of implantation, the extraction torque was markedly higher for the HA coated screws. In the second series, instrumentations with uncoated, partly HA coated or fully HA coated screws were used. After 11-16 months implantation, the extraction torques were recorded. There were significant differences between all three groups, with the lowest extraction torques for the uncoated screws and the highest torques for the fully HA coated screws. The frequency of radiolucent zones surrounding the screws was higher for the uncoated screws than for the HA coated screws.</p><p>Radiographs from both experimental and clinical studies were examined. Screws demonstrating radiolucent zones were compared to screws without zones with respect to pull-out resistance, extraction torque, bone-to-implant contact and amount of bone surrounding the screws. All these variables demonstrated higher values for the screws without radiolucent zones. The frequency of radiolucent zones surrounding uncoated screws in the clinical study was 53%.</p><p>Conclusions: Radiolucent zones are good predictors of screw loosening. The frequency of radiolucent zones is higher than previously described. Hydroxyapatite coating improves the purchase of pedicle screws and reduces the frequency of screw loosening.</p>

Loosening of implants is a frequent complication in orthopaedic surgery. The aim of this thesis was to evaluate hydroxyapatite coating of pedicle screws with mechanical and histological methods and to correlate the results with the radiological findings. Hydroxyapatite (HA) coating of pedicle screws was investigated in experimental studies in sheep. Nine sheep were operated on with destabilising laminectomies at L2-L3 and L4-L5 and stabilised with pedicle screw instrumentations, where HA coated and uncoated screws were used in a randomised fashion. After both 6 and 12 weeks of implantation, the HA coated screws demonstrated a higher bone-to-implant contact and a higher amount of bone in the area close to the screw. The pull-out resistance, stiffness and total energy to failure was higher for the HA coated screws after 12 weeks of implantation. HA coating of pedicle screws was examined in two clinical studies. In the first series, the patients were stabilised with pedicle screw instrumentations, where HA coated screws were used in either the upper or lower instrumented level in a randomised fashion. After 10-22 months of implantation, the extraction torque was markedly higher for the HA coated screws. In the second series, instrumentations with uncoated, partly HA coated or fully HA coated screws were used. After 11-16 months implantation, the extraction torques were recorded. There were significant differences between all three groups, with the lowest extraction torques for the uncoated screws and the highest torques for the fully HA coated screws. The frequency of radiolucent zones surrounding the screws was higher for the uncoated screws than for the HA coated screws. Radiographs from both experimental and clinical studies were examined. Screws demonstrating radiolucent zones were compared to screws without zones with respect to pull-out resistance, extraction torque, bone-to-implant contact and amount of bone surrounding the screws. All these variables demonstrated higher values for the screws without radiolucent zones. The frequency of radiolucent zones surrounding uncoated screws in the clinical study was 53%. Conclusions: Radiolucent zones are good predictors of screw loosening. The frequency of radiolucent zones is higher than previously described. Hydroxyapatite coating improves the purchase of pedicle screws and reduces the frequency of screw loosening.

>Magister Scientiae - MSc / Aim: The aim of this study was to report on the frequency of and radiographic features of non-odontogenic malignancies of the jaws as seen on panoramic images, stored in the radiological achieves over an eleven year period.

Die vorliegende Studie befasste sich mit zwei Fragestellungen. Im ersten Teil wurde die Projektionsabhängigkeit von radiologischen Landmarken im konventionellen Röntgenbild der Schulter und damit deren klinische Anwendbarkeit untersucht. Im zweiten Teil wurde das Auftreten von sog. röntgenhellen Linien (RLL) bei Glenoidersatz im konventionellen Röntgen und im CT untersucht. Beide Fragestelllungen sind in der Beurteilung von Landmarken von Glenoidkomponenten in der Endoprothetik der Schulter von Bedeutung. Zur Beantwortung der ersten Frage wurden 6 mit Markierungen versehene humane Scapula-Leichenpräparate in 25 Projektionen geröntgt und der Einfluss der Projektionen auf gängige Landmarken gemessen. Die Landmarken wurden an der Margo lateralis, Margo medialis, knöchernen Glenoid, Coracoidbasis, Fossa supraspinata und oberen Linie der Spina scapulae festgelegt. Zur Beantwortung der zweiten Frage wurden 10 humane Glenoid-Leichenpräparate mit einzementierter Glenoidkomponente im konventionellen Röntgen und im CT untersucht. Alle gewonnenen radiologischen Bilder wurden von zwei Untersuchern vermessen und die Interobserverreliabilität errechnet. Die Ergebnisse des ersten Teiles sowohl der Messwerte der Landmarken als auch der Interobserverreliabilität zeigten, dass die Margo medialis des Schulterblattes die zuverlässigsten Ergebnisse bei der Robustheit gegen Verkippung zur Beurteilung des Kunststoff Glenoids aufwiesen. Im klinischen Alltag ist diese Landmarke jedoch auf vielen Röntgenbildern der Schulter nicht mit abgebildet. Es zeigte sich, dass die am wenigsten projektionsabhängige Landmarke, die regelmässig auf Schulteraufnahmen abgebildet ist, die Margo lateralis scapulae ist. Als Ergebnis des zweiten Teiles zeigte sich, dass im konventionellen Röntgen sichtbare RLL im CT nicht alle zur Darstellung kamen und somit als Artefakte zu werten waren. Aufgrund der klinisch schwierig durchzuführenden Röntgentechnik kann nicht immer eine exakte AP Aufnahme im konventionellen Röntgen gewonnen werden, wodurch auch projektionsbedingt Doppellinien erscheinen können. Diese wurden vermutlich durch die konvexe Form des PE Glenoids und Zementfehlern verursacht. Zur Beurteilung einer Lockerung sollte also eine Computertomografie angefertigt werden. Weiterhin zeigte sich aber auch im CT, dass frisch implantierte Glenoidkomponenten trotz optimaler Bedingungen RLL aufweisen. Dies zeigte deutlich, dass die Zementiertechnik auch in ihrer modernen Form noch nicht voll ausgereift war und deshalb weiterhin nach Verbesserungsmöglichkeiten gesucht werden sollte. / The aim of this study was to evaluate the reliability of different bony landmarks on radiographs after implantation of a total shoulder arthroplasty when the scapula is tilted compared with the ideal ap view. To assess loosening of the glenoid component, serial evaluation of ap radiographs of the scapula has been established as the 'gold standard. This study also verified the incidence of radiolucent lines (RLL) in radiographs and on CTscans to show different measurements of localization and appearance of the RLL. For the first aim of this study glenoid components were implanted into 6 human cadaveric scapulae. Radiographs were taken exactly anterior-posterior in the frontal plane, as well as craniocaudal tilted (±15° and ±30°) and mediolateral tilted (±10° and ±20°). The following landmarks were evaluated: lateral margin of the scapula, medial margin of the scapula, floor of the fossa supraspinatus line, spine of the scapula line, glenoid fossa line, and coracoid base line. In the second part of this study, 10 glenoid components were implanted into human cadaveric glenoids and a CT-scan as well as radiographs were made in an exact anteriorposterior view. The images were compared to evaluate the localization, incidence and form of the RLL. Every X-ray was measured by two different examiners to show the interobserver reliability. Regarding robustness against glenoid tilt, the medial margin of the scapula had the best intraobserver and interobserver reliability, whereas the lateral margin of the scapula had an acceptable intraobserver and interobserver reliability. In measuring medial migration, the glenoid fossa line had a significantly lower intraobserver and interobserver reliability than the coracoid base line. Because conventional radiographs were hardly done in exact ap direction despite the laboratory within, RLL were seen on X-ray although no RLL actually existed. The CT-scans highlighted the existence of artefacts, which looked like RLL on conventional radiography. The curved form of the glenoid component can cause double lines, which look like RLL on X-rays. However, the conventional radiography can still be used to detect an increase of RLL in postoperativ control X-rays. To be absolutely sure whether RLL do exist a CT-scan has to be done. This study shows that, even under best conditions for an implantation of glenoid components RLL can be viewed due to false cementation technique. The results underline that the cement implantation can still be improved to minimize the incidence of RLL.