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Item type:Publication, Access status: without files , Estimating the benefit of a collar on uncemented press-fit stems(British Editorial Society of Bone and Joint Surgery, 2026-03); ; ; ; A collar has been shown to be beneficial in reducing peri-prosthetic fractures (PPF) and revisions in uncemented total hip arthroplasty using tapered press-fit stems (revision rate at 15 years 4,8% compared to 6.1% for collarless)1. The purpose of this study was to develop a numerical model to estimate the benefit of adding a collar to an uncemented stem. Materials and Methods Two human cadaveric femurs were implanted with a collared re. collarless CORAIL stem (DePuy Synthes) until failure using a material testing machine (constant velocity 0.1 mm/s). Shear, axial compressive and tangential tensile strains as well as fracture load were recorded using Digital Image correlation and compared between with vs. without collar. A finite element model (FEM) based on a CT scan of one femur was used to numerically estimate the same parameters for three different stem types with vs. without collar (CORAIL, EMPHASIS, ACTIS all DePuy Synthes). Results The collar increased axial compressive strains instead of causing critical excessive tangential tensile strains (hoop strains) that can result in PPF during loading. This results in substantially higher loads required for a fracture. In the experimental part of the study the collar increased the fracture load for the CORAIL stem by nearly 100% (6824N vs. 3465N, ratio 1.96). The results of the FEM model yielded a similar tendency for the CORAIL stem but with a higher benefit ratio (3.37). The EMPHASYS stem showed very similar results (ratio: 3.47), whereas the ACTIS stem showed a smaller benefit (ratio: 1.69). Discussion The ACTIS stem benefits less from the collar due to its fit-and-fill design in the metaphyseal region associated with a larger width compared to the two other stem designs investigated. This approach can be used for any uncemented stem design. Acknowledgement. The study was financially supported by DePuy-SynthesPublicationtype: Conference Paper9 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Contamination of modular hip taper interfaces increases post-assembly interface seating(British Editorial Society of Bone and Joint Surgery, 2016-05-01); ; ; 10 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Telemetric assessment of bone healing with an instrumented internal fixator : a preliminary study(American Orthopaedic Association, 2011-11-01); ; ; ; In an interdisciplinary project involving electronic engineers and clinicians, a telemetric system was developed to measure the bending load in a titanium internal femoral fixator. As this was a new device, the main question posed was: what clinically relevant information could be drawn from its application? As a first clinical investigation, 27 patients (24 men, three women) with a mean age of 38.4 years (19 to 66) with femoral nonunions were treated using the system. The mean duration of the nonunion was 15.4 months (5 to 69). The elasticity of the plate-callus system was measured telemetrically until union. Conventional radiographs and a CT scan at 12 weeks were performed routinely, and healing was staged according to the CT scans. All nonunions healed at a mean of 21.5 weeks (13 to 37). Well before any radiological signs of healing could be detected, a substantial decrease in elasticity was recorded. The relative elasticity decreased to 50% at a mean of 7.8 weeks (3.5 to 13) and to 10% at a mean of 19.3 weeks (4.5 to 37). At 12 weeks the mean relative elasticity was 28.1% (0% to 56%). The relative elasticity was significantly different between the different healing stages as determined by the CT scans. Incorporating load measuring electronics into implants is a promising option for the assessment of bone healing. Future application might lead to a reduction in the need for exposure to ionising radiation to monitor fracture healing. ©2012 British Editorial Society of Bone and Joint Surgery.Publicationtype: Journal Article107 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Orientation of the acetabular component : a comparison of five navigation systems with conventional surgical technique(Ed. Soc. of Bone and Joint Surgery, 2006-10-01); ; ; We compared the orientation of the acetabular component obtained by a conventional manual technique with that using five different navigation systems. Three surgeons carried out five implantations of an acetabular component with each navigation system, as well as manually, using an anatomical model. The orientation of the acetabular component, including inclination and anteversion, and its position was determined using a co-ordinate measuring machine. The variation of the orientation of the acetabular component was higher in the conventional group compared with the navigated group. One experienced surgeon took significantly less time for the procedure. However, his placement of the component was no better than that of the less experienced surgeons. Significantly better inclination and anteversion (p < 0.001 for both) were obtained using navigation. These parameters were not significantly different between the surgeons when using the conventional technique (p = 0.966). The use of computer navigation helps a surgeon to orientate the acetabular component with less variation regarding inclination and anteversion. © 2006 British Editorial Society of Bone and Joint Surgery.Publicationtype: Journal Article6