Post-cam mechanics and tibiofemoral kinematics: a dynamic in vitro analysis of eight posterior-stabilized total knee designs

Posterior cruciate ligament (PCL)-substituting total knee arthroplasty (TKA) designs were introduced to avoid paradoxical roll forward of the femur and to optimize knee kinematics. The aim of this in vitro study was to investigate post-cam function and contact mechanics and relate it to knee kinematics during squatting in eight contemporary posterior-stabilized TKA designs. All prostheses were fixed on custom-designed metal fixtures and mounted in a knee rig and five sequential-loaded squats were performed between 30A degrees and 130A degrees of flexion. Contact pressure and contact area were measured using pressure-sensitive Tekscan sensors on the posterior face of the post. Kinematics was recorded with reflective markers and infrared light-capturing cameras. The post-cam mechanisms analyzed in this study are very variable in terms of design features. This leads to large variations in terms of the flexion angle at which the post and cam engage maximal contact force, contact pressure and contact area. We found that more functional post-cam mechanisms, which engage at lower flexion angle and have a similar behavior as normal PCL function, generally show more normal rollback and tibial rotation at the expense of higher contact forces and pressures. All designs show high contact forces. A positive correlation was found between contact force and initial contact angle. Post-cam contact mechanics and kinematics were documented in a standardized setting. Post-cam contact mechanics are correlated with post-cam function. Outcomes of this study can help to develop more functional designs in future. Nevertheless, a compromise will always be made between functional requirements and risk of failure. We assume that more normal knee kinematics leads to more patient satisfaction because of better mobility. Understanding of the post-cam mechanism, and knowing how this system really works, is maybe the clue in further development of new total knee designs

The Effect of Okra Mosaic Virus and Beetle Damage on Yield of Four Okra Cultivars

The effect of beetle damage and infection by okra mosaic virus (OMV) on pod yield, number of fruits, plant height and time of harvest for okra (Abelmoschus esculentus) was investigated. A preliminary greenhouse experiment was set-up in order to examine the effect of OMV in combination with the application of the pesticide Nuvacron 40 SCW on the cultivar Jockoson. The greenhouse experiment revealed that there was no interaction between the applied pesticide and the infection by OMV for the measured parameters (P=0.98). Virus infection in this greenhouse experiment significantly reduced yield by 26 % (P<0.0001) and delayed first harvest by 5 days (P<O.0001). Nitrogen pod content did not differ for the different treatment combinations. In the field experiments, an average yield reduction of 49% was caused by beetle damage on the four cultivars (P=0.017). The 16% yield reduction caused by the virus infection was not significant (P=0.467). The cultivar Awgu Early was low yielding, Jockoson and NHAe47-4 were the highest yielding cultivars, but were less resistant to beetle attack than V35. V35 consistently had a moderate yield.Nous examinons ici l'effet sur le gombo du rongement par les coleopteres et de l'infection par le virus de la mosaique du gombo (VMG). Les parametres examines sont: le rendement (poids), le nombre des fruits, le moment de la recolte et la taille des plants du gombo (Abelmoschus esculentus). Une experience en serre a permis de mettre en evidence l'effet conjugue du VMG avec application de l'insecticide Nuvacron 40 SCW sur la variete Jockoson. Cette experience en serre a montre que l'insecticide n'a d'effet ni sur le VMG ni sur les plantes (P=0.98). L'infection du virus en serre a cause une diminution significative de l'importance de la recolte de 26% (P{0.0001) et a retarde le moment de la recolte de 5 jours (P{0.0001). La mesure de la teneur en azote des fruits pour les quatre traitement (absence de l'insecticide et du virus; absence de l'insecticide et presence du virus, presence de l'insecticide et absence du virus; absence e l'insecticide et presence du virus) n'est pas significativement differente. Le rongement par les coleopteres a cause une reduction moyenne de 49 % du rendement a ciel ouvert pour les quatre varietes de gombo (Awgu Early, Jockoson, NHAe47-4 et V35) (P=0.017). Au cours de cette meme experience, l'effet du VMG (reduction de 16% de la recolte) n'a pas pu etre mis en evidence de maniere significative (P=0.467). L'effet sur les quatre varigres n'a pas ete le meme. Pour la variete Awgu Early, le rendement a ete faible. Les varietes Jockoson et NHAe47-4 ont genere une recolte plus importante mais ont fait preuve d'une resistance plus faible au rongement par les coleopteres que la variete V35. La variete V35 enfin, a donne des resultats moyenne

Post-cam mechanics and tibiofemoral kinematics: a dynamic in vitro analysis of eight posterior-stabilized total knee designs

Posterior cruciate ligament (PCL)-substituting total knee arthroplasty (TKA) designs were introduced to avoid paradoxical roll forward of the femur and to optimize knee kinematics. The aim of this in vitro study was to investigate post-cam function and contact mechanics and relate it to knee kinematics during squatting in eight contemporary posterior-stabilized TKA designs.status: publishe

Post-cam mechanics and tibiofemoral kinematics: a dynamic in vitro analysis of eight posterior-stabilized total knee designs

Purpose: Posterior cruciate ligament (PCL)-substituting total knee arthroplasty (TKA) designs were introduced to avoid paradoxical roll forward of the femur and to optimize knee kinematics. The aim of this in vitro study was to investigate post-cam function and contact mechanics and relate it to knee kinematics during squatting in eight contemporary posterior-stabilized TKA designs. Methods: All prostheses were fixed on custom-designed metal fixtures and mounted in a knee rig and five sequential-loaded squats were performed between 30° and 130° of flexion. Contact pressure and contact area were measured using pressure-sensitive Tekscan sensors on the posterior face of the post. Kinematics was recorded with reflective markers and infrared light-capturing cameras. Results: The post-cam mechanisms analyzed in this study are very variable in terms of design features. This leads to large variations in terms of the flexion angle at which the post and cam engage maximal contact force, contact pressure and contact area. We found that more functional post-cam mechanisms, which engage at lower flexion angle and have a similar behavior as normal PCL function, generally show more normal rollback and tibial rotation at the expense of higher contact forces and pressures. All designs show high contact forces. A positive correlation was found between contact force and initial contact angle. Conclusion: Post-cam contact mechanics and kinematics were documented in a standardized setting. Post-cam contact mechanics are correlated with post-cam function. Outcomes of this study can help to develop more functional designs in future. Nevertheless, a compromise will always be made between functional requirements and risk of failure. We assume that more normal knee kinematics leads to more patient satisfaction because of better mobility. Understanding of the post-cam mechanism, and knowing how this system really works, is maybe the clue in further development of new total knee designs.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Unraveling the effects of 1,25(OH)₂D₃ on global gene expression in pancreatic islets

Manuscrito. -- 3 h.; papel; folio. -- Fondo Universidad de Salamanca; sección Claustros; serie Borradores de claustros. -- Buena conservación. -- Fechas: 03/09/1825

Post-cam mechanics and tibiofemoral kinematics: a dynamic in vitro analysis of eight posterior-stabilized total knee designs

Purpose: Posterior cruciate ligament (PCL)-substituting total knee arthroplasty (TKA) designs were introduced to avoid paradoxical roll forward of the femur and to optimize knee kinematics. The aim of this in vitro study was to investigate post-cam function and contact mechanics and relate it to knee kinematics during squatting in eight contemporary posterior-stabilized TKA designs. Methods: All prostheses were fixed on custom-designed metal fixtures and mounted in a knee rig and five sequential-loaded squats were performed between 30° and 130° of flexion. Contact pressure and contact area were measured using pressure-sensitive Tekscan sensors on the posterior face of the post. Kinematics was recorded with reflective markers and infrared light-capturing cameras. Results: The post-cam mechanisms analyzed in this study are very variable in terms of design features. This leads to large variations in terms of the flexion angle at which the post and cam engage maximal contact force, contact pressure and contact area. We found that more functional post-cam mechanisms, which engage at lower flexion angle and have a similar behavior as normal PCL function, generally show more normal rollback and tibial rotation at the expense of higher contact forces and pressures. All designs show high contact forces. A positive correlation was found between contact force and initial contact angle. Conclusion: Post-cam contact mechanics and kinematics were documented in a standardized setting. Post-cam contact mechanics are correlated with post-cam function. Outcomes of this study can help to develop more functional designs in future. Nevertheless, a compromise will always be made between functional requirements and risk of failure. We assume that more normal knee kinematics leads to more patient satisfaction because of better mobility. Understanding of the post-cam mechanism, and knowing how this system really works, is maybe the clue in further development of new total knee designs.SCOPUS: ar.jinfo:eu-repo/semantics/publishe