Influence of prosthesis design and implantation technique on implant stresses after cementless revision THR

BACKGROUND: Femoral offset influences the forces at the hip and the implant stresses after revision THR. For extended bone defects, these forces may cause considerable bending moments within the implant, possibly leading to implant failure. This study investigates the influences of femoral anteversion and offset on stresses in the Wagner SL revision stem implant under varying extents of bone defect conditions. METHODS: Wagner SL revision stems with standard (34 mm) and increased offset (44 mm) were virtually implanted in a model femur with bone defects of variable extent (Paprosky I to IIIb). Variations in surgical technique were simulated by implanting the stems each at 4 degrees or 14 degrees of anteversion. Muscle and joint contact forces were applied to the reconstruction and implant stresses were determined using finite element analyses. RESULTS: Whilst increasing the implant's offset by 10 mm led to increased implant stresses (16.7% in peak tensile stresses), altering anteversion played a lesser role (5%). Generally, larger stresses were observed with reduced bone support: implant stresses increased by as much as 59% for a type IIIb defect. With increased offset, the maximum tensile stress was 225 MPa. CONCLUSION: Although increased stresses were observed within the stem with larger offset and increased anteversion, these findings indicate that restoration of offset, key to restoring joint function, is unlikely to result in excessive implant stresses under routine activities if appropriate fixation can be achieved

Bone regeneration via novel macroporous CPC scaffolds in critical-sized cranial defects in rats

Objectives. Calcium phosphate cement (CPC) is promising for dental and craniofacial applications due to its ability to be injected or filled into complex-shaped bone defects and molded for esthetics, and its resorbability and replacement by new bone. The objective of this study was to investigate bone regeneration via novel macroporous CPC containing absorbable fibers, hydrogel microbeads and growth factors in critical-sized cranial defects in rats. Methods. Mannitol porogen and alginate hydrogel microbeads were incorporated into CPC. Absorbable fibers were used to provide mechanical reinforcement to CPC scaffolds. Six CPC groups were tested in rats: (1) control CPC without macropores and microbeads; (2) macroporous CPC + large fiber; (3) macroporous CPC + large fiber + nanofiber; (4) same as (3), but with rhBMP2 in CPC matrix; (5) same as (3), but with rhBMP2 in CPC matrix + rhTGF-beta 1 in microbeads; (6) same as (3), but with rhBMP2 in CPC matrix + VEGF in microbeads. Rats were sacrificed at 4 and 24 weeks for histological and micro-CT analyses. Results. The macroporous CPC scaffolds containing porogen, absorbable fibers and hydrogel microbeads had mechanical properties similar to cancellous bone. At 4 weeks, the new bone area fraction (mean +/- sd; n = 5) in CPC control group was the lowest at (14.8 +/- 3.3)%, and that of group 6 (rhBMP2 + VEGF) was (31.0 +/- 13.8)% (p < 0.05). At 24 weeks, group 4 (rhBMP2) had the most new bone of (38.8 +/- 15.6)%, higher than (12.7 +/- 5.3)% of CPC control (p < 0.05). Micro-CT revealed nearly complete bridging of the critical-sized defects with new bone for several macroporous CPC groups, compared to much less new bone formation for CPC control. Significance. Macroporous CPC scaffolds containing porogen, fibers and microbeads with growth factors were investigated in rat cranial defects for the first time. Macroporous CPCs had new bone up to 2-fold that of traditional CPC control at 4 weeks, and 3-fold that of traditional CPC at 24 weeks, and hence may be useful for dental, craniofacial and orthopedic applications. (C) 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved

Matrix elasticity of void-forming hydrogels controls transplanted-stem-cell-mediated bone formation

The effectiveness of stem cell therapies has been hampered by cell death and limited control over fate. These problems can be partially circumvented by using macroporous biomaterials that improve the survival of transplanted stem cells and provide molecular cues to direct cell phenotype. Stem cell behaviour can also be controlled in vitro by manipulating the elasticity of both porous and non-porous materials, yet translation to therapeutic processes in vivo remains elusive. Here, by developing injectable, void-forming hydrogels that decouple pore formation from elasticity, we show that mesenchymal stem cell (MSC) osteogenesis in vitro, and cell deployment in vitro and in vivo, can be controlled by modifying, respectively, the hydrogel’s elastic modulus or its chemistry. When the hydrogels were used to transplant MSCs, the hydrogel’s elasticity regulated bone regeneration, with optimal bone formation at 60 kPa. Our findings show that biophysical cues can be harnessed to direct therapeutic stem cell behaviours in situ

Matrix elasticity of void-forming hydrogels controls transplanted-stem-cell-mediated bone formation

The effectiveness of stem cell therapies has been hampered by cell death and limited control over fate. These problems can be partially circumvented by using macroporous biomaterials that improve the survival of transplanted stem cells and provide molecular cues to direct cell phenotype. Stem cell behaviour can also be controlled in vitro by manipulating the elasticity of both porous and non-porous materials, yet translation to therapeutic processes in vivo remains elusive. Here, by developing injectable, void-forming hydrogels that decouple pore formation from elasticity, we show that mesenchymal stem cell (MSC) osteogenesis in vitro, and cell deployment in vitro and in vivo, can be controlled by modifying, respectively, the hydrogel's elastic modulus or its chemistry. When the hydrogels were used to transplant MSCs, the hydrogel's elasticity regulated bone regeneration, with optimal bone formation at 60 kPa. Our findings show that biophysical cues can be harnessed to direct therapeutic stem cell behaviours in situ

Fraktur Kalluskompetenz: Einflussfaktoren auf das Risiko einer sekundären Knochenheilung

Die Knochenheilung ist ein sehr komplexer Prozess des muskuloskeletalen Systems zur Wiederherstellung einer intakten skeletalen Struktur. Das Ergebnis der muskuloskeletalen Regeneration hängt sowohl von mechanischen, als auch von biologischen Faktoren ab. Normalerweise ist die Knochenheilung ein sehr schneller und effektiver Prozess. Dennoch kommt es bei einem kleinen aber doch signifikanten Prozentsatz von Patienten zu Abweichungen vom normalen Heilungsprozess und damit zu verzögerter Heilung oder zu sogenannten Pseudo-Arthrosen. Bisher ist noch unklar, wie sich physiologische Heilungs-Prozesse verändern und dann zu diesen Fehlbildungen führen. Weiterhin ist fraglich, wie die Eigenschaften des Kallus durch systemische und lokale Einflussfaktoren, die bekanntermaßen die Knochenheilung beeinflussen, verändert werden können. Daher war das Ziel dieser Arbeit, die mechanischen, geometrischen und mikrostrukturellen Zusammenhänge von mineralisiertem Kallus besser zu verstehen und die Möglichkeit der Einflussnahme darauf während der Knochenheilung durch systemische und lokale Faktoren zu untersuchen. Das Ergebnis dieser Arbeit ist die Etablierung eines Kleintiermodells der Knochenfixierung unter kontrollierten mechanischen Bedingungen. In diesem Tiermodell konnte nachgewiesen werden, dass Alter, Geschlecht und Defektgröße die Kallus Kompetenz und die Wiedererlangung der Knochenfestigkeit auf Organebene beeinflussen. Es wurde gezeigt, dass in älteren Tieren die Veränderung der Knochenheilung nicht auf eine Änderungen der Kallus-Struktur oder einen geringere Reaktion auf mechanische Reize zurückzuführen ist. Vielmehr ist es ein veränderter Prozess der Kallus-Reifung, sowohl in der Mikrostruktur, als auch im Ausmaß der Mineralisierung, aus dem verschiedene mechanische Eigenschaften bei alten und jungen Tieren resultieren. Unterschiedliche Fixateur-Konfigurationen veränderten bei alten Tieren im Gegensatz zu den jungen Tieren nicht die Kallusgewebe-Mineralisation. Es wurde außerdem gezeigt, dass ältere Tiere eine höhere osteoclastische Aktivität aufwiesen, wodurch evtl. die beeinträchtigte Kallus-Mikrostruktur erklärt werden kann. Die Stabilität der Fixation hatte einen Einfluss auf das Heilungsergebnis der jungen Tiere, bei denen eine verzögerte Heilung bei semi-rigider Fixation beobachtet wurde, viii trotz größerer Kallusbildung. Sowohl die Kallus-Überbrückung, als auch die biomechanische Eigenschaften waren schlechter als bei der rigiden Fixation. Es wurde auch beobachtet, dass die Stabilität der Fixation einen Einfluss auf die Vaskularisation hat. Die semi-rigide Fixation hatte eine geringere Neu-Bildung von vaskulären Netzwerken zur Folge. Weiterhin ist das Geschlecht der Versuchstiere ein Faktor für das Heilungsergebnis. Während die Auswirkungen bei jungen Tieren und kleinen Knochendefekten eher gering waren, wurde das Heilungsergebnis bei alten Tieren oder großen Knochendefekten stark vom Geschlecht beeinflusst. Im Detail lagen die Unterschiede beim Heilungsergebnis dabei in der Größe des Kallus und nicht in der Mineralisation der Mikrostuktur. Während der beeinträchtigten Heilung durch einen großen segmentalen Knochendefekt wurde gezeigt, dass die sich die Kallus-Kompetenz vom normalen Heilungsprozess unterscheidet. Besonders die Kallus-Morphologie und weniger die Mineralisation veränderte sich durch den Mangel an mechano-biologischen Stimuli innerhalb eines großen Knochendefektes. Nach Kenntnisstand der Autoren ist dies die erste Studie, die zeigt, auf welche Weise die Kalluskompetenz auf Weichgewebeniveau von verschiedenen Faktoren beeinflusst wird. Die Studie zeigt außerdem, dass zukünftige Knochenheilungstherapien eventuell an die beeinflussenden Faktoren angepasst werden sollten. Dies könnte in Form eines Vorhersage-Tools zur intraoperativen Diagnose von Risikofaktoren der Knochenheilung geschehen. Die Ergebnisse der Studie können genutzt werden, um rechtzeitig die Knochenheilung abhängig von den Risikofaktoren zu stimulieren.Bone healing is a highly complex regenerative process that the musculoskeletal system undergoes in order to restore skeletal integrity. Both mechanical and biological processes work together to determine the outcome of musculoskeletal regeneration. Although bone repair is a rapid and efficient process, failure to heal still occurs in a small but significant proportion of patients, and a delayed union or nonunion develops. It remains unclear how physiological healing processes are altered during bone healing, leading to delayed or non-union. Furthermore, it is unclear how regain of bone strength by means of callus competence is altered due to systemic and local factors that are known to influence bone healing. Therefore, the goal of this thesis was to understand mechanical, geometrical, micro-structural, and compositional components of mineralized callus tissue and how they maybe influenced due to systemic and local factors during bone healing. The results in this study show the establishment of a standardized means of bone defect fixation in a small animal model with controlled mechanical conditions. Using the animal model the influence of varying age, gender, fixation stability, and bone defect have been shown to influence callus competence, and the regain of bone strength at an organ level. It is shown in this study that bone healing in the aged seems to be compromised not by changes in callus patterning or a reduced influence of mechanical constrains. Rather, it is the altered process of callus maturation, both in microstructure and extent of mineralization that results in different mechanical competences in aged compared to younger subjects. Varying fixator configurations in older individuals did not alter the dominant effect of advanced age on callus tissue mineralization, unlike in their younger counterparts. It has also been shown that age individuals had a higher osteoclastic activity that might have caused the observed impaired callus microstructure. Stability was shown to influence healing outcome in the young individuals. A delayed healing was observed in younger individuals with semi rigid fixation. Although a larger callus was observed during semi rigid fixation, the callus bridging and biomechanical parameters were lower than their rigid counterparts. It was also obsrved that stability had an influence on vascularity at the bone defect site. Semi rigid fixation caused lower vascular network at the bone defect site. Sex of the individuals was observed to cause differences in healing outcome. In younger individuals or individuals with a small bone defect, although healing was influenced due to sex of the individual, it was not detrimental. However, in the older individual or during large bone defect healing, the outcome was influenced by sex and detrimental to the individuals healing outcome. It was shown that the difference in healing was dependent on callus volume and not due to mineralization or microstructure. During impaired bone healing due to a segmental bone defect, it was observed that callus competence deviated from normal behaviour. Callus morphology and volume, and not bone mineralization was shown to be strongly influenced due to lack of mechanobiological stimulus in a large bone defect. To the authors knowledge this is the first study to show that callus competence is influenced at a tissue level in varying ways depending on the factors influencing it. In the future, a development of a prognostic kit might be needed to intra-operatively diagnose factors that could risk healing outcome. The results could be used to specifically stimulate the bone healing depending on the risk factor and in a timely fashion

Unusual presentation of firework injury causing intraoral burns

Fireworks are commonly used in celebrate festive occasions. We present a case of an unusual presentation of intraoral firework injury, which is a very rare case. A fifteen year old boy kept four explosive papercaps wrapped in a small polythene bags in between his left molars and crushed them. This resulted in a contused lacerated wound over the left buccal mucosa. Patient was treated conservatively with maintenance of intraoral hygiene, antibiotics, proteolytic enzymes and analgesics. It took 18 days for complete healing of the wound

Case Report- Unusual presentation of firework injury causing intraoral burns

Fireworks are commonly used in celebrate festive occasions. We present a case of an unusual presentation of intraoral firework injury, which is a very rare case. A fifteen year old boy kept four explosive papercaps wrapped in a small polythene bags in between his left molars and crushed them. This resulted in a contused lacerated wound over the left buccal mucosa. Patient was treated conservatively with maintenance of intraoral hygiene, antibiotics, proteolytic enzymes and analgesics. It took 18 days for complete healing of the wound

sj-docx-3-ejo-10.1177_11206721231185808 - Supplemental material for The effects of age-related macular degeneration on work productivity: A meta-analysis

Supplemental material, sj-docx-3-ejo-10.1177_11206721231185808 for The effects of age-related macular degeneration on work productivity: A meta-analysis by Edward Tran, Manav Nayeni, Nirmit Shah and Monali S Malvankar-Mehta in European Journal of Ophthalmology</p

sj-docx-2-ejo-10.1177_11206721231185808 - Supplemental material for The effects of age-related macular degeneration on work productivity: A meta-analysis

Supplemental material, sj-docx-2-ejo-10.1177_11206721231185808 for The effects of age-related macular degeneration on work productivity: A meta-analysis by Edward Tran, Manav Nayeni, Nirmit Shah and Monali S Malvankar-Mehta in European Journal of Ophthalmology</p