Prisca Noble

CT analysis of defects of the cement mantle and alignment of the stem IN VITRO COMPARISON OF CHARNLEY-KERBOUL FEMORAL HIP IMPLANTS INSERTED LINE-TO-LINE AND UNDERSIZED IN PAIRED FEMORA

Using a modern cementing technique, we implanted 22 stereolithographic polymeric replicas of the Charnley-Kerboul stem in 11 pairs of human cadaver femora. On one side, the replicas were cemented line-to-line with the largest broach. On the other, one-size undersized replicas were used (radial difference, 0.89 mm sd 0.13).CT analysis showed that the line-to-line stems without distal centralisers were at least as well aligned and centered as undersized stems with a centraliser, but were surrounded by less cement and presented more areas of thin (< 2 mm) or deficient (< 1 mm) cement. These areas were located predominantly at the corners and in the middle and distal thirds of the stem. Nevertheless, in line-to-line stems, penetration of cement into cancellous bone resulted in a mean thickness of cement of 3.1 mm (sd 0.6) and only 6.2% of deficient and 26.4% of thin cement. In over 90% of these areas, the cement was directly supported by cortical bone or cortical bone with less than 1 mm of cancellous bone interposed. When Charnley-Kerboul stems are cemented line-to-line, good clinical results are observed because cement-deficient areas are limited and are frequently supported by cortical bone.

An equine joint friction test model using a cartilage-on-cartilage arrangement.

This study describes an equine joint friction test using a cartilage-on-cartilage arrangement and investigates the influence of age and load on the frictional response. Osteochondral plugs were extracted from equine shoulder joints (2-5 years, n=12; 10-14 years, n=15), and mounted in a pin-on-disc tribometer. The frictional response was then measured under constant conditions (2N; 20 degrees C; 5 mm/s), and with increasing load (2N, 5N, 10N). In all experiments, the friction coefficient of young cartilage was significantly (P<0.001) smaller than obtained from old cartilage, while the application of a greater load resulted in a significant (P<0.001) decrease in friction coefficient only in old cartilage. It was concluded that cartilage ageing was responsible for an increase in friction coefficient under these experimental conditions. Moreover, where young cartilage lubrication remained stable, cartilage ageing may have been responsible for lubrication regime change. The cartilage-on-cartilage model could be used to better understand lubrication regime disturbances in healthy and diseased equine joints, and to test the efficacy of various bio-lubricant treatments.

A pendulum test as a tool to evaluate viscous friction parameters in the equine fetlock joint

An equine fetlock joint pendulum test was studied and the influence of post mortem time and intra-articular lipid solvent on the viscous frictional response examined. Fresh equine digits (group 1, n=6 controls; group 2, n=6 lipid solvent) were mounted on a pendulum tribometer. Assuming that pendular joint damping could be modelled by a harmonic oscillator fluid damping (HOFD), damping time (τ), viscous damping coefficient (c) and friction coefficient (μ) were monitored for 5h under experimental conditions (400N; 20°C). In all experiments, pendular joint damping was found to follow an exponential decay function (R(2)=0.99714), which confirmed that joint damping was fluid. The evolution of τ, c and μ was found to be significantly (P<0.05) different in the two groups, with a decrease in τ and an increase in c and μ that was faster and more prominent in digits from group 2. It was concluded that pendular joint damping could be modelled by a HOFD model. The influence of post mortem time on results suggested that, ideally, joint mechanical properties should only be tested on fresh cadavers at the same post mortem time. Moreover, the addition of lipid solvent was found to be responsible for upper viscous friction parameters and for a reduced damping time, which suggested that articular lubricating ability was compromised. This equine pendulum test could be used to test the efficacy of various bio-lubricant treatments.

Heel effects on joint contact force components in the equine digit: a sensitivity analysis

REASONS FOR PERFORMING STUDY Whereas the effect of heel configuration on the tension of the suspensory apparatus is well documented in the literature, there are few reports of joint contact force components in the equine distal forelimb. OBJECTIVES To improve understanding of the effect of heel configuration on equine digit joint loading, a sensitivity analysis was performed to compare the effect of a raised heel on joint contact force components in the coffin and fetlock joints during the stance phase of the trot. MATERIALS AND METHODS Four Warmblood horses were used. An inverse dynamic analysis was carried out using kinematic and kinetic data. Taking into account the tendon wrapping forces (WF) around the sesamoid bones in the calculations, the joint contact forces (CF) were estimated for the coffin and fetlock joints during the trot stance phase (4 m/s). To test the sensitivity of the results to heel configuration changes, calculations were performed repeatedly for different heel configurations (raised by 0, 6 and 12°). A one-way ANOVA with repeated measures was used to test the effect of heel configuration (at the 3 levels) (α = 0.05; P < 0.05; post hoc testing: Bonferroni). RESULTS For heel configurations raised from 0-12°: whereas the tension of the deep digital flexor tendon decreased and the tension of the superficial digital flexor tendon increased, for the coffin joint the peak WF (1.4 ± 0.25 bwt; 1.2 ± 0.2 bwt; 0.95 ± 0.1 bwt) and the peak CF (2.45 ± 0.25 bwt; 2.2 ± 0.2 bwt; 2 ± 0.1 bwt) decreased significantly (P < 0.05). For the fetlock joint, the peak WF (3.8 ± 0.7 bwt; 4.1 ± 0.3 bwt; 4.4 ± 0.25 bwt) and the peak CF (4.35 ± 0.7 bwt; 4.7 ± 0.35 bwt; 5 ± 0.3 bwt) increased, but not significantly. CONCLUSION This analysis suggests that the coffin joint loading and fetlock joint loading are strongly connected. The heel configuration may influence both coffin joint and fetlock joint contact force components.

Multilevel use of image repository in the field of veterinary imaging and dissemination of training tools

Purpose At our institute we organized a teaching environment enabling radiology and radioanatomy courses with today’s advanced 2D image reviewing and 3D image postprocessing to offer a state of the art environment to our Radiological Technologists in training, providing tools like MPR and VR [1]. Enabling students to handle large image sets remotely at home and during hands on courses. The advent of CT volume scanning did dramatically change our habit of image viewing and image postprocessing for our Radiological Technologists in training. Methods The original setup was created to support the teaching of the students at the medical faculty of the Vrije Universiteit Brussel. We agreed to share infrastructure of the teaching environment to the Hogeschool-Universiteit Brussel in order to enhance the skillslab setup. The vast amount of datasets originating from a clinical PACS are the building blocks for the educational anatomy and radiopathology training sets [2]. The image repository consists out of sufficient blinded image material. Native DICOM sets can be processed into MPR and VR sets. Teaching the Radiological Technologists takes place in skillslab at Hogeschool-Universiteit Brussel. The general purpose computers available in the skillslab are used as reviewing and processing stations. The courses on radiology and radioanatomy need to compete with other courses regarding the software installation. To avoid technical issues around compatibility of certain competing software and releases of products, we decided to apply a virtual environment. In this way we can freeze the correct software computer setting for our application without compromising the functionality of the other competing courses and vice versa. In the skillslab the students were dedicated to an individual client workstation during the practical lessons. On this client the student need to load and startup the prepared virtual machine from the server to start his learning session. At the Vrije Universiteit Brussel the general purpose thin clients classrooms were connected to a VMware server environment based on VMware Vsphere and VMware View software. The infrastructure is managed by the medical informatics department at the University College. Secondly the advanced setup was secured in order to provide teaching sets in reach over the internet for use at home [3]. Since hosting takes place on a central server, the hardware requirements of the remote client are minimal. The student had to install the VMWare client which runs on all latest versions of Windows, Mac and Linux platforms. This provides the students with a remote view on the virtual desktop; the communication between the client and the virtual desktops is based upon a secure remote desktop viewing protocol. With this approach the student is free to utilize his preferred computer system. By means of a standard internet connection the cases are available for analysis and processing at any time and at any place during their training. Results The teaching methods of the past where merely based on static presentation of images in text books and X-ray film based illustrations presented on lightboxes. In the interim period between film based, atlas viewing and the full digital system we did hand over the educational cases to the students on CD-R or DVD-R media, pointless to say that the production of those media were time-consuming and the access of these media was not very user friendly for the student. The profound change of teaching methods from plain atlas and hardcopy viewing to 3D sets was a difficult transition for some lecturers. After that transition period the lecturers were all convinced of the broader possibilities of the tools which enhanced the knowledge acquirements and improved abilities of image handling. Students embrace the possibilities of image processing and the possibilities to study their cases at their own speed and time. The 3D visualization did improve the understanding of complex anatomy training. The grades improved in field of anatomy and radiopathology Conclusions Without changing the infrastructure of our skillslab we were able to offer multiple applications such as advanced radiological viewing and image postprocessing. Once the infrastructure was tested and fully functional, the main job of the support team was on the server side. An upgrade of the iSite enterprise software will take place in the near future, which implies building a new virtual machine. When the virtual machine is fully tested, this environment can be redistributed in the computer classrooms. In an educational environment where possibly conflicting requirements in setup exist, this approach is highly appreciated by the teachers of different disciplines. The quality of our education program by means of the enhanced visualization is not only superior to the use of books and distributed CD-R, but is also more appreciated by the students. The ease of installation at the remote site and the possibility of use at home is certainly an added value for the students. The proposed system is nowadays an added value for students and lecturers. It will be part of the future teaching platform. We aim to extent its content and develop it into a base for our e-learning program. References [1] Silén, C., Wirell, S., Kvist, J., Nylander, E., & Smedby, O. (2008, Jun 30). Advanced 3D visualisation in student-centered medical education. Med Teach, pp. 115–124. [2] Turmezei, T., Tam, M., & Loughna, S. (2009, Sept 22). A survey of medical students on the impact of a new digital imaging library in the dissection room. Clin Anat, pp. 761–769. [3] Petersson, H., Sinkvist, D., Wang, C., & Smedby, O. (2009, Mar-Apr 2). Web-based interactive 3D visualization as a tool for improved anatomy learning. Anat Sci Educ, pp. 61– 68.