Common peroneal nerve palsy complicating knee dislocation and bicruciate ligaments tears

SummaryIntroductionThe occurrence rate of common peroneal nerve (CPN) palsy associated with knee dislocation or bicruciate ligament injury ranges from 10 to 40%. The present study sought first to describe the anatomic lesions encountered and their associated prognoses and second to recommend adequate treatment strategy based on a prospective multicenter observational series of knee ligament trauma cases.Material and methodsTwelve out of 67 knees treated for dislocation or bicruciate lesion presented associated CPN palsy: two females, 10 males; mean age, 32 years. Four sports injuries, three traffic accidents and five other etiologies led to seven complete dislocations and five bicruciate ruptures. Four cases involved associated popliteal artery laceration ischemia; one of the dislocations was open. Paralysis was total in eight cases and partial in four. There were two complete ruptures, three contusions with CPN in continuity stretch lesions and three macroscopically normal aspects.ResultsAt a minimum 1 year's follow-up, regardless of the initial surgical technique performed, recovery was complete in six cases, partial (in terms of motor function) in one and absent in five. Without specific CPN surgery, spontaneous recovery was partial in one case, complete in two and absent in none. Following simple emergency or secondary neurolysis, remission was total in four cases and absent in one. Three nerve grafts were all associated with non-recovery.DiscussionThe present results agree with literature findings. Palsy rates varied with trauma circumstances and departmental recruitment. Neurologic impairment was commensurate to ligamentary damages. The anatomic status of the CPN, subjected to violent traction by dislocation, was the most significant prognostic factor for neurologic recovery. In about 25% of dislocations, contusion-elongation over several centimeters was associated with as poor a prognosis as total rupture. CPN neurolysis is recommended when early clinical and EMG recovery fails to progress and/or in case of lateral ligamentary reconstruction. Possible peripheral nerve impairment needs to be included in the overall functional assessment of treatment for severe ligaments injuries and knee dislocation.Level of evidenceLevel IV, prospective study

A new doubly discrete analogue of smoke ring flow and the real time simulation of fluid flow

Modelling incompressible ideal fluids as a finite collection of vortex filaments is important in physics (super-fluidity, models for the onset of turbulence) as well as for numerical algorithms used in computer graphics for the real time simulation of smoke. Here we introduce a time-discrete evolution equation for arbitrary closed polygons in 3-space that is a discretisation of the localised induction approximation of filament motion. This discretisation shares with its continuum limit the property that it is a completely integrable system. We apply this polygon evolution to a significant improvement of the numerical algorithms used in Computer Graphics.Comment: 15 pages, 3 figure

New pixelized Micromegas detector with low discharge rate for the COMPASS experiment

New Micromegas (Micro-mesh gaseous detectors) are being developed in view of the future physics projects planned by the COMPASS collaboration at CERN. Several major upgrades compared to present detectors are being studied: detectors standing five times higher luminosity with hadron beams, detection of beam particles (flux up to a few hundred of kHz/mm^{2}, 10 times larger than for the present Micromegas detectors) with pixelized read-out in the central part, light and integrated electronics, and improved robustness. Two solutions of reduction of discharge impact have been studied, with Micromegas detectors using resistive layers and using an additional GEM foil. Performance of such detectors has also been measured. A large size prototypes with nominal active area and pixelized read-out has been produced and installed at COMPASS in 2010. In 2011 prototypes featuring an additional GEM foil, as well as an resistive prototype, are installed at COMPASS and preliminary results from those detectors presented very good performance. We present here the project and report on its status, in particular the performance of large size prototypes with an additional GEM foil.Comment: 11 pages, 5 figures, proceedings to the Micro-Pattern Gaseous Detectors conference (MPGD2011), 29-31 August 2011, Kobe, Japa

Contributions of the anterolateral complex and the anterolateral ligament to rotatory knee stability in the setting of ACL Injury: a roundtable discussion

Persistent rotatory knee laxity is increasingly recognized as a common finding after anterior cruciate ligament (ACL) reconstruction. While the reasons behind rotator knee laxity are multifactorial, the impact of the anterolateral knee structures is significant. As such, substantial focus has been directed toward better understanding these structures, including their anatomy, biomechanics, in vivo function, injury patterns, and the ideal procedures with which to address any rotatory knee laxity that results from damage to these structures. However, the complexity of lateral knee anatomy, varying dissection techniques, differing specimen preparation methods, inconsistent sectioning techniques in biomechanical studies, and confusing terminology have led to discrepancies in published studies on the topic. Furthermore, anatomical and functional descriptions have varied widely. As such, we have assembled a panel of expert surgeons and scientists to discuss the roles of the anterolateral structures in rotatory knee laxity, the healing potential of these structures, the most appropriate procedures to address rotatory knee laxity, and the indications for these procedures. In this round table discussion, KSSTA Editor-in-Chief Professor Jón Karlsson poses a variety of relevant and timely questions, and experts from around the world provide answers based on their personal experiences, scientific study, and interpretations of the literature. Level of evidence V

Fast readout of the COMPASS RICH CsI-MWPC photon chambers

Abstract A new readout system for CsI-coated MWPCs, used in the COMPASS RICH detector, has been proposed and tested in nominal high-rate conditions. It is based on the APV25-S1 analog sampling chip, and will replace the Gassiplex chip readout used up to now. The APV chip, originally designed for silicon microstrip detectors, is shown to perform well even with "slow" signals from a MWPC, keeping a signal-to-noise ratio of 9. For every trigger the system reads three consecutive in-time samples, thus allowing to extract information on the signal shape and its timing. The effective time window is reduced from ∼3 μs for the Gassiplex to below 400 ns for the APV25-S1 chip, reducing pile-up events at high particle rate. A significant improvement of the signal-to-background ratio by a factor 5–6 with respect to the original readout has been measured in the central region of the RICH detector. Due to its pipelined architecture, the new readout system also considerably reduces the dead time per event, allowing efficient data taking at higher trigger rate

A Cryogenic High-Reynolds Turbulence Experiment at CERN

The potential of cryogenic helium flows for studying high-Reynolds number turbulence in the laboratory has been recognised for a long time and implemented in several small-scale hydrodynamic experiments. With its large superconducting particle accelerators and detector magnets, CERN, the European Laboratory for Particle Physics, has become a major world center in helium cryogenics, with several large helium refrigerators having capacities up to 18 kW @ 4.5 K. Combining a small fraction of these resources with the expertise of three laboratories at the forefront of turbulence research, has led to the design, swift implementation, and successful operation of GReC (Grands Reynolds Cryogéniques) a large axisymmetric turbulent-jet experiment. With flow-rates up to 260 g/s of gaseous helium at ~ 5 K and atmospheric pressure, Reynolds numbers up to 107 have been achieved in a 4.6 m high, 1.4 m diameter cryostat. This paper presents the results of the first runs and describes the experimental set-up comprehensively equipped with "hot" wire micro-anemometers, acoustic scattering vorticity measurements and a large-bandwidth data acquisition system

Fast Photon Detection for Particle Identification with COMPASS RICH-1

Particle identification at high rates is an important challenge for many current and future high-energy physics experiments. The upgrade of the COMPASS RICH-1 detector requires a new technique for Cherenkov photon detection at count rates of several $10^6$ per channel in the central detector region, and a read-out system allowing for trigger rates of up to 100 kHz. To cope with these requirements, the photon detectors in the central region have been replaced with the detection system described in this paper. In the peripheral regions, the existing multi-wire proportional chambers with CsI photocathode are now read out via a new system employing APV pre-amplifiers and flash ADC chips. The new detection system consists of multi-anode photomultiplier tubes (MAPMT) and fast read-out electronics based on the MAD4 discriminator and the F1-TDC chip. The RICH-1 is in operation in its upgraded version for the 2006 CERN SPS run. We present the photon detection design, constructive aspects and the first Cherenkov light in the detector.Comment: Proceedings of the Imaging 2006 conference, Stockholm, Sweden, 27-30 June 2006, 5 pages, 6 figures, to appear in NIM A; corrected typo in caption of Fig.

Fast photon detection for the COMPASS RICH detector

The COMPASS experiment at the SPS accelerator at CERN uses a large scale Ring Imaging CHerenkov detector (RICH) to identify pions, kaons and protons in a wide momentum range. For the data taking in 2006, the COMPASS RICH has been upgraded in the central photon detection area (25% of the surface) with a new technology to detect Cherenkov photons at very high count rates of several 10^6 per second and channel and a new dead-time free read-out system, which allows trigger rates up to 100 kHz. The Cherenkov photons are detected by an array of 576 visible and ultra-violet sensitive multi-anode photomultipliers with 16 channels each. The upgraded detector showed an excellent performance during the 2006 data taking.Comment: Proceeding of the IPRD06 conference (Siena, Okt. 06

The Fast Read-out System for the MAPMTs of COMPASS RICH-1

A fast readout system for the upgrade of the COMPASS RICH detector has been developed and successfully used for data taking in 2006 and 2007. The new readout system for the multi-anode PMTs in the central part of the photon detector of the RICH is based on the high-sensitivity MAD4 preamplifier-discriminator and the dead-time free F1-TDC chip characterized by high-resolution. The readout electronics has been designed taking into account the high photon flux in the central part of the detector and the requirement to run at high trigger rates of up to 100 kHz with negligible dead-time. The system is designed as a very compact setup and is mounted directly behind the multi-anode photomultipliers. The data are digitized on the frontend boards and transferred via optical links to the readout system. The read-out electronics system is described in detail together with its measured performances.Comment: Proceeding of RICH2007 Conference, Trieste, Oct. 2007. v2: minor change

A FABRY-PEROT CAVITY FOR COMPTON POLARIMETRY

A new kind of Compton polarimeter using a resonant Fabry—Pe« rot cavity as a power buildup for the photon beam is proposed. A prototype of such a cavity is described, along with the results obtained in terms of source to be used in a Compton scattering polarimeter. ( 1998 Elsevier Science B.V. All rights reserved