Desalineación rotacional del implante tibial en artroplastia total de rodilla: estudio con navegación

Objetivo: Estudiar la rotación del implante tibial y el desajuste rotacional de los implantes femoral y tibial en los 19 casos intervenidos de artroplastia total de rodilla modelo Natural II, con sistema de navegación Navitrack® (Zimmer®). Material y Métodos: Estudio prospectivo en una serie consecutiva de 19 casos de artrosis de rodilla. Se analizaron las medidas realizadas con un sistema de navegación: 1- el ángulo entre la línea que va desde la inserción del Ligamento Cruzado Posterior al tercio medio de la tuberosidad tibial anterior y la línea anteroposterior del implante tibial para determinar la rotación del mismo; 2- el ángulo de la línea femoral epicondílea con el bloque de corte que nos dará la rotación del implante femoral. Resultados: La rotación media del implante tibial ha sido - 0,011º ± 0,533 (r: -0,800 / 1,000). La rotación del implante femoral con relación a la línea epicondílea ha sido -3,174º ± 4,733 (r: -12,300 / 7,700). El ajuste rotacional femorotibial ha sido -2,963º ± 4,649 (r: -11,500/ 6,700). Encontramos una alineación rotacional femorotibial en el 63% de los casos. Conclusiones: El sistema de navegación utilizado permite colocar el implante tibial con una rotación adecuada así como evitar un desajuste rotacional entre los implantes femoral y tibial. Actualmente se consideran de forma combinada las rotaciones de los implantes, lo que tiene gran importancia para evitar los problemas rotulianos así como el desgaste del polietileno.To study the rotational alignment of the tibial implant in 19 patients who underwent total knee arthroplasty by surgical navigation system. Material and Methods: Prospective analysis of 19 consecutive patients with knee osteoarthritis. References obtained by the computerized navigation were: 1- the angle between the line from the insertion of the posterior cruciate ligament to the medial tibial tuberosity and the anteroposterior tibial implant line to study the tibial rotation; 2- the angle between the epicondyle line and the cut piece to study the femoral rotation. Results: The media tibial implant rotation was - 0,011º ± 0,533 (r: -0,800/ 1,000). The femoral implant rotation was -3,174º ± 4,733 (r: -12,300 / 7,700). The mean angle of the rotational mismatch of the components was -2,963º ± 4,649 (r: -11,500/ 6,700). There was a good femorotibial mismatch in 63%. Conclusions: The navigation system helps us to put the tibial implant in a good rotation and so a good femorotibial mismatch. Actually we study the combined rotation of the implants to decrease the patelofemoral problems and the polyethylene damage

Habitat selection in terrestrial snails and its applications to heliciculture

Snails are employed as experimental animals in different scientific fields and their growth is a good biological indicator. Growth is mainly determined at a genetic level, although many factors biotic and abiotic may alter growth rates. One of these factors is habitat selection. Nevertheless the knowledge about the cha-racteristics that determines habitat selection are not considered in the design of installations, management of farms or raising snails. In this way, the aim of this paper is synthesize the different components of habitat that influence habitat choice of terrestrial snails. On the other hand, it proposes premises that would be considered in design of installations.El crecimiento de los caracoles terrestres que, además de como animales productivos, se utilizan como animales de experimentación es considerado un buen indicador biológico. Aunque el crecimiento está genéticamente determinado, muchos factores pueden modificarlo, uno de ellos es la selección de hábitat. Sin embargo, los conocimientos sobre las condiciones que la determinan no se suelen incorporar al diseño de instalaciones, manejo de los criaderos o la producción helicícola. En este trabajo se revisan aquellas condiciones que determinan la selección de microhábitat en caracoles terrestres y se proponen medidas que deberían ser consideradas en el diseño de instalaciones

Deep sub-threshold Ξ−\Xi^- production in Ar+KCl reactions at 1.76A GeV

We report first results on a deep sub-threshold production of the doubly strange hyperon $\Xi^-$ in a heavy-ion reaction. At a beam energy of 1.76A GeV the reaction Ar+KCl was studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18/GSI. A high-statistics and high-purity $\Lambda$ sample was collected, allowing for the investigation of the decay channel $\Xi^- \to \Lambda \pi^-$. The deduced $\Xi^-/(\Lambda+\Sigma^0)$ production ratio of $(5.6 \pm 1.2 ^{+1.8}_{-1.7})\cdot 10^{-3}$ is significantly larger than available model predictions.Comment: 4 pages, including 4 figure

An upper limit on hypertriton production in collisions of Ar(1.76 AGeV)+KCl

A high-statistic data sample of Ar(1.76 AGeV)+KCl events recorded with HADES is used to search for a hypertriton signal. An upper production limit per centrality-triggered event of $1.04$ x $10^{-3}$ on the $3\sigma$ level is derived. Comparing this value with the number of successfully reconstructed $\Lambda$ hyperons allows to determine an upper limit on the ratio $N_{_{\Lambda}^3H}/N_{\Lambda}$, which is confronted with statistical and coalescence-type model calculations

In-Medium Effects on K0 Mesons in Relativistic Heavy-Ion Collisions

We present the transverse momentum spectra and rapidity distributions of $\pi^{-}$ and K$^0_S$ in Ar+KCl reactions at a beam kinetic energy of 1.756 A GeV measured with the spectrometer HADES. The reconstructed K$^0_S$ sample is characterized by good event statistics for a wide range in momentum and rapidity. We compare the experimental $\pi^{-}$ and K$^0_S$ distributions to predictions by the IQMD model. The model calculations show that K$^0_S$ at low tranverse momenta constitute a particularly well suited tool to investigate the kaon in-medium potential. Our K$^0_S$ data suggest a strong repulsive in-medium K$^0$ potential of about 40 MeV strength.Comment: 10 pages, 10 figures, accepted by Phys. Rev.

Baryonic resonances close to the Kbar-N threshold: the case of Sigma(1385)^+ in pp collisions

We present results of an exclusive measurement of the first excited state of the Sigma hyperon, Sigma(1385)^+, produced in p+p -> Sigma^+ + K^+ + n at 3.5 GeV beam energy. The extracted data allow to study in detail the invariant mass distribution of the Sigma(1385)^+. The mass distribution is well described by a relativistic Breit-Wigner function with a maximum at m_0 = 1383.2 +- 0.9 MeV/c^2 and a width of 40.2 +- 2.1 MeV/c^2. The exclusive production cross-section comes out to be 22.27 +- 0.89 +- 1.56 +3.07 -2.10 mu b. Angular distributions of the Sigma(1385)^+ in different reference frames are found to be compatible with the hypothesis that 33 % of Sigma(1385)^+ result from the decay of an intermediate Delta^{++} resonance.Comment: 12 pages; 12 figures; submitted to PR

Meson and di-electron production with HADES

The HADES experiment, installed at GSI, Darmstadt, measures di-electron production in A+A, p/pi+N and p/pi+A collisions. Here, the pi0 and eta Dalitz decays have been reconstructed in the exclusive p+p reaction at 2.2 GeV to form a reference cocktail for long-lived di-electron sources. In the C+C reaction at 1 and 2 GeV/u, these long-lived sources have been subtracted from the measured inclusive e+e- yield to exhibit the signal from the early phase of the collision. The results suggest that resonances play an important role in dense nuclear matter.Comment: Invited plenary talk at the 10th International Workshop On Meson Production, Properties And Interaction (MESON 2008) 6-10 Jun 2008, Cracow, Polan

Study of dielectron production in C+C collisions at 1 AGeV

The emission of e+e- pairs from C+C collisions at an incident energy of 1 GeV per nucleon has been investigated. The measured production probabilities, spanning from the pi0-Dalitz to the rho/omega! invariant-mass region, display a strong excess above the cocktail of standard hadronic sources. The bombarding-energy dependence of this excess is found to scale like pion production, rather than like eta production. The data are in good agreement with results obtained in the former DLS experiment.Comment: submitted to Physics Letters

Dilepton production in pp and CC collisions with HADES

Dilepton production has been measured with HADES, the "High Acceptance DiElectron Spectrometer". In pp collisions at 2.2GeV kinetic beam energy, exclusive eta production and the Dalitz decay eta -> gamma e+e- has been reconstructed. The electromagnetic form factor is well in agreement with existing data. In addition, an inclusive e+e- spectrum from the C+C reaction at 2AGeV is presented and compared with a thermal model.Comment: 11 pages, 3 figures, proceedings of the IVth International Conference on Quarks and Nuclear Physics, Madrid, June 5th-10th, submitted to Eur.Phys.J.