Der Effekt eines neuen Knochenzementes (Palamed G) auf das Migrationsverhalten der NexGen Knieendoprothese. Eine radiostereometrische Studie.

Das Ziel dieser Arbeit ist der klinische Einsatz digitaler radiostereometrischer Analyse (RSA) als diagnostische Messmethode zur Erkennung früher postoperativer aseptischer Lockerungszeichen der tibialen Plateaus von Totalknieendoprothesen des Typs NexGen® LPS im Vergleich mit der Verwendung zweier verschiedener Zementtypen – dem niedrigviskösen Standardzement Palacos® R und dem hochviskösen Palamed® G Knochenzement (beide Merck, Darmstadt). Im Rahmen einer prospektiven Studie mit historischer Vergleichsgruppe wurden die Migrationseigenschaften beider Prothesen-Zement-Kombinationen überprüft. Zusätzlich wurde zur klinisch symptomatischen Beurteilung der Patienten und zur weiteren Evaluation zu allen Messzeitpunkten prä- und postoperativ der Knee Society Clinical Rating Score (Insall et al 1989) erhoben. Durch Einsatz von RSA können mit Hilfe zweidimensionaler Röntgenaufnahmen anhand Verknüpfung der Bildinformationen durch spezielle Computersoftware (UmRSA 4.0®), Implantatbewegungen im Zeitverlauf dreidimensional rekonstruiert werden. Die Studie wurde an einer Patientenpopulation von 34 Probanden durchgeführt, die im Rahmen eines Vorlaufprojektes zwischen Dezember 1999 und Oktober 2000 eine mit Palamed® G Knochenzement implantierte Vollprothese erhielten. Als historische Kontrollgruppe wurden Patientendaten aus einer zwischen 1995 und 1997 in unserem Haus durchgeführten RSA Studie genutzt, die den gleichen Prothesentyp erhielten, jedoch eine Zementierung mit Palacos ® R. Nach 2 Jahren konnten bei 18 Patienten der Versuchs- und 9 Patienten der Kontrollgruppe eine komplette Analyse durchgeführt werden. Dabei wurden die RSA Untersuchungen zum Vergleich herangezogen, die nach Erstellung der Referenzaufnahme zwischen dem 3. und 7. postoperativen Tag in einem Intervall von 3, 6 und 12 Monaten in einer vorhergehenden Studie, sowie nun nach 2 Jahren durchgeführt wurden. Die Endpunkte der RSA waren für die Longitudinalbewegung die Parameter MaxSub, Maxliftoff und MTPM und x-, y- und z-Rot für die Rotationsbewegungen, allerdings mit Betonung der MTPM als Summationsvektor der anderen Parameter. Im Vergleich beider Gruppen fanden sich unter Nutzung parametrischer und nichtparametrischer statistischer Tests nach zwei Jahren keine signifikanten Unterschiede für die Longitudinalbewegungen, obwohl die Palamed®-Gruppe zu allen Zeitpunkten eine geringere Mikrobewegung als die mit Palacos® R fixierten Designs aufwiesen. Im Gegensatz hierzu fanden sich für die Rotationsparameter in allen drei Ebenen signifikant geringere Bewegungen für die mit Palamed® G Zement fixierten Prothesen. Die klinischen Ergebnisse anhand des Knee Society Scores zeigten in einer Vorstudie für beide Gruppen eine deutlich Verbesserung von prä- nach postoperativ, wobei die größte Verbesserung in der Vorarbeit zwischen dem präoperativen und 3 Monate postoperativen Messzeitpunkt liegt, ohne einen statistisch signifikanten Unterschied zwischen beiden Zementen nachzuweisen. Im Verlauf über zwei Jahre zeigt sich in beiden Scores eine geringe Abnahme, ohne signifikante Unterschiede im Vergleich der beiden Gruppen. Die hier beschriebene Studie war bereits im Vorfeld als Pilotprojekt definiert, was die verhältnismäßig geringe Fallzahl insbesondere der Kontrollgruppe erklären kann. Dennoch sollten die Ergebnisse dieser Arbeit den Boden für eine Langzeitbeobachtung von Palamed® G Knochenzement mittels einer randomisierten klinischen Studie entsprechenden Designs ebnen, um die Migrationseigenschaften des Zementes deutlicher belegen zu können. Zusammenfassend kann dem hier klinisch mittels röntgenstereometrischer Analyse getesteten hochviskösem Palamed®-Knochenzement in Kombination mit einer NexGen® LPS Knieendoprothese eine vergleichsweise befriedigende Grenzflächenbeweglichkeit attestiert werden

Rein tension in harness trotters during on-track exercise

Horseracing is under public scrutiny with increasing demands to safeguard horse welfare. It is accepted that, as a result of bit pressure and/or equipment, mouth lesions accompany many types of horse use, including racing. However, there are currently no data available on the range of bit pressures in driven trotters. Our aim was to investigate whether rein tension (RT, proxy for bit pressures) differs among gaits, between tempo within gait, between horses and drivers, and between left/right reins. Standardbreds (n = 9), driven by experienced drivers (n = 11), performed exercise tests on a racetrack (cross-over design; total 31 tests, data available from 26 tests). Horses' motion symmetry was measured before tests (trotting in hand). Rein tension, speed and heart rate were measured during exercise. A moving-window filter was applied to RT raw data. Median, maximum and interquartile range for the estimated stride median RT were determined for each rein (left/right) and segment: walk; circling in slow trot followed by transition to faster trot; fast (racing) trot; and slowing down to walk. Mixed models were used for statistical analysis. Least square means for segment median RT ranged between 17-19 N in walk, 34-40 N during circling-accelerating, 51-62 N in fast trot, and 53-71 N for slowing down. Segment maximum RT was between 60-81 N in walk, 104-106 N during circling-accelerating, 72-86 N in fast trot, and 86-129 N during slowing down. Interquartile ranges were between 7-9 N in walk, 28-31 N during circling-accelerating, 8-10 N in fast trot, and 12-18 N for slowing down. Hind limb asymmetry exceeded the recommended threshold in three horses and was associated with higher median (48 N) and maximum (106 N) RT than symmetric horses (29 N and 73 N, respectively, p < 0.01). Consistent left-right asymmetry in RT was more common among horses than among drivers. Rein tension increased with increasing heart rate (p <= 0.0006). Rein tensions were higher than those reported during riding or in horses worked from the ground. The findings of high RT, taken together with the high reported prevalence of oral injuries in harness trotters, call for further research into RT, motion symmetry and use of equipment

Rein tension in harness trotters during on-track exercise

Horseracing is under public scrutiny with increasing demands to safeguard horse welfare. It is accepted that, as a result of bit pressure and/or equipment, mouth lesions accompany many types of horse use, including racing. However, there are currently no data available on the range of bit pressures in driven trotters. Our aim was to investigate whether rein tension (RT, proxy for bit pressures) differs among gaits, between tempo within gait, between horses and drivers, and between left/right reins. Standardbreds (n = 9), driven by experienced drivers (n = 11), performed exercise tests on a racetrack (cross-over design; total 31 tests, data available from 26 tests). Horses\u27 motion symmetry was measured before tests (trotting in hand). Rein tension, speed and heart rate were measured during exercise. A moving-window filter was applied to RT raw data. Median, maximum and interquartile range for the estimated stride median RT were determined for each rein (left/right) and segment: walk; circling in slow trot followed by transition to faster trot; fast (racing) trot; and slowing down to walk. Mixed models were used for statistical analysis. Least square means for segment median RT ranged between 17–19 N in walk, 34–40 N during circling-accelerating, 51–62 N in fast trot, and 53–71 N for slowing down. Segment maximum RT was between 60–81 N in walk, 104–106 N during circling-accelerating, 72–86 N in fast trot, and 86–129 N during slowing down. Interquartile ranges were between 7–9 N in walk, 28–31 N during circling-accelerating, 8–10 N in fast trot, and 12–18 N for slowing down. Hind limb asymmetry exceeded the recommended threshold in three horses and was associated with higher median (48 N) and maximum (106 N) RT than symmetric horses (29 N and 73 N, respectively, p &lt; 0.01). Consistent left-right asymmetry in RT was more common among horses than among drivers. Rein tension increased with increasing heart rate (p ≤ 0.0006). Rein tensions were higher than those reported during riding or in horses worked from the ground. The findings of high RT, taken together with the high reported prevalence of oral injuries in harness trotters, call for further research into RT, motion symmetry and use of equipment

Open pore titanium foams via metal injection molding of metal powder with a space holder

Powder methods are highly applicable for the processing of more challenging metals and forms. Examples of materials that encompass both of these are metallic foams, which are advanced materials that consist of a network of interconnected or randomly spaced macropores separated by dense or microporous cell walls. These macropores can be either open or closed, or mix of those two, depending on the manufacturing process. One popular metal foam that has received a huge amount of interest in the last decade is Ti foam, due to it offering a unique combination of properties, such as high strength to weight ratio and high permeability combined with excellent biocompatibility. In this study the use of metal injection molding of titanium powder in combination with a space holder (to create large pore spaces) is examined for the production of open pore Ti foams for biomedical applications. Potassium chloride with two different particle shapes (spherical and cubic) was used as a space holder. It was found that feedstocks prepared with spherical KCl particles had a lower viscosity and better flowability compared to those made using cubic particles. Ti foams with a total porosity of 61.25% ± 0.29 were successfully produced. The structure of the foams produced was characterized using SEM and X-ray micro-computed tomography

Clinical value of SPECT/CT for evaluation of patients with painful knees after total knee arthroplasty- a new dimension of diagnostics?

<p>Abstract</p> <p>Background</p> <p>The purpose of our study was to evaluate the clinical value of hybrid SPECT/CT for the assessment of patients with painful total knee arthroplasty (TKA).</p> <p>Methods</p> <p>Twenty-three painful knees in patients following primary TKA were assessed using Tc-99m-HDP-SPECT/CT. Rotational, sagittal and coronal position of the TKA was assessed on 3D-CT reconstructions. The level of the SPECT-tracer uptake (0-10) and its anatomical distribution was mapped using a validated localization scheme. Univariate analysis (Wilcoxon-Mann-Whitney, Spearmean`s-rho test, p < 0.05) was performed to identify any correlations between component position, tracer uptake and diagnosis.</p> <p>Results</p> <p>SPECT/CT imaging changed the suspected diagnosis and the proposed treatment in 19/23 (83%) knees. Progression of patellofemoral OA (n = 11), loosening of the tibial (n = 3) and loosening of the femoral component (n = 2) were identified as the leading causes of pain after TKA.</p> <p>Patients with externally rotated tibial trays showed higher tracer uptake in the medial patellar facet (p = 0.049) and in the femur (p = 0.051). Patients with knee pain due to patellofemoral OA showed significantly higher tracer uptake in the patella than others (p < 0.001).</p> <p>Conclusions</p> <p>SPECT/CT was very helpful in establishing the diagnosis and guiding subsequent management in patients with painful knees after TKA, particularly in patients with patellofemoral problems and malpositioned or loose TKA.</p

Local Application of BMP-2 Specific Plasmids in Fibrin Glue does not Promote Implant Fixation

<p>Abstract</p> <p>Background</p> <p>BMP-2 is known to accelerate fracture healing and might also enhance osseointegration and implant fixation. Application of recombinant BMP-2 has a time-limited effect. Therefore, a gene transfer approach with a steady production of BMP-2 appears to be attractive. The aim of this study was to examine the effect of locally applied BMP-2 plasmids on the bone-implant integration in a non-weight bearing rabbit tibia model using a comparatively new non-viral copolymer-protected gene vector (COPROG).</p> <p>Methods</p> <p>Sixty rabbits were divided into 4 groups. All of them received nailing of both tibiae. The verum group had the nails inserted with the COPROG vector and BMP-2 plasmids using fibrin glue as a carrier. Controls were a group with fibrin glue only and a blank group. After 28 and 56 days, these three groups were sacrificed and one tibia was randomly chosen for biomechanical testing, while the other tibia underwent histomorphometrical examination. In a fourth group, a reporter-gene was incorporated in the fibrin glue instead of the BMP-2 formula to prove that transfection was successful.</p> <p>Results</p> <p>Implant fixation strength was significantly lower after 28 and 56 days in the verum group. Histomorphometry supported the findings after 28 days, showing less bone-implant contact.</p> <p>In the fourth group, successful transfection could be confirmed by detection of the reporter-gene in 20 of 22 tibiae. But, also systemic reporter-gene expression was found in heterotopic locations, showing an undesired spreading of the locally applied gene formula.</p> <p>Conclusion</p> <p>Our results underline the transfecting capability of this vector and support the idea that BMP-2 might diminish osseointegration. Further studies are necessary to specify the exact mechanisms and the systemic effects.</p

Assessment of bone ingrowth potential of biomimetic hydroxyapatite and brushite coated porous E-beam structures

The bone ingrowth potential of biomimetic hydroxyapatite and brushite coatings applied on porous E-beam structure was examined in goats and compared to a similar uncoated porous structure and a conventional titanium plasma spray coating. Specimens were implanted in the iliac crest of goats for a period of 3 (4 goats) or 15 weeks (8 goats). Mechanical implant fixation generated by bone ingrowth was analyzed by a push out test. Histomorphometry was performed to assess the bone ingrowth depth and bone implant contact. The uncoated and hydroxyapatite-coated cubic structure had significantly higher mechanical strength at the interface compared to the Ti plasma spray coating at 15 weeks of implantation. Bone ingrowth depth was significantly larger for the hydroxyapatite- and brushite-coated structures compared to the uncoated structure. In conclusion, the porous E-beam surface structure showed higher bone ingrowth potential compared to a conventional implant surface after 15 weeks of implantation. Addition of a calcium phosphate coating to the E-beam structure enhanced bone ingrowth significantly. Furthermore, the calcium phosphate coating appears to work as an accelerator for bone ingrowth

Combining 3D human in vitro methods for a 3Rs evaluation of novel titanium surfaces in orthopaedic applications.

In this study we report on a group of complementary human osteoblast in vitro test methods for the preclinical evaluation of 3D porous titanium surfaces. The surfaces were prepared by additive manufacturing (electron beam melting, EBM) and plasma spraying, allowing the creation of complex lattice surface geometries. Physical properties of the surfaces were characterised by SEM and profilometry and 3D in vitro cell culture using human osteoblasts. Primary human osteoblast cells were found to elicit greater differences between titanium sample surfaces than an MG63 osteoblast-like cell line, particularly in terms of cell survival. Surface morphology was associated with higher osteoblast metabolic activity and mineralisation on rougher titanium plasma spray coated surfaces than smoother surfaces. Differences in osteoblast survival and metabolic activity on titanium lattice structures were also found, despite analogous surface morphology at the cellular level. 3D confocal microscopy identified osteoblast organisation within complex titanium surface geometries, adhesion, spreading and alignment to the biomaterial strut geometries. Mineralised nodule formation throughout the lattice structures was also observed, and indicative of early markers of bone in-growth on such materials. Testing methods such as those presented are not traditionally considered by medical device manufacturers, but we suggest have value as an increasingly vital tool in efficiently translating pre-clinical studies, especially in balance with current regulatory practice, commercial demands, the 3Rs and the relative merits of in vitro and in vivo studies. This article is protected by copyright. All rights reserved