Quantification of interfacial motions following primary and revision total knee arthroplasty: A verification study versus experimental data

Motion at the bone–implant interface, following primary or revision knee arthroplasty, can be detrimental to the long‐term survival of the implant. This study employs experimentally verified computational models of the distal femur to characterize the relative motion at the bone–implant interface for three different implant types; a posterior stabilizing implant (PS), a total stabilizing implant (TS) with short stem (12 mm × 50 mm), and a total stabilizing implant (TS) with long offset stem (19 mm × 150 mm with a 4 mm lateral offset). Relative motion was investigated for both cemented and uncemented interface conditions. Monitoring relative motion about a single reference point, though useful for discerning global differences between implant types, was found to not be representative of the true pattern and distribution of motions which occur at the interface. The contribution of elastic deformation to apparent reference point motion varied based on implant type, with the PS and TSSS implanted femurs experiencing larger deformations (43 and 39 μm, respectively) than the TSLS implanted femur (22 μm). Furthermore, the pattern of applied loading was observed to greatly influence location and magnitude of peak motions, as well as the surface area under increased motion. Interestingly, the influence was not uniform across all implant types, with motions at the interface of long stemmed prosthesis found to be less susceptible to changes in pattern of loading. These findings have important implications for the optimization and testing of orthopedic implants in vitro and in silico. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:387–396, 2018.     

Repair of composite zygomatico-maxillary defects with free bone grafts and free vascularized tissue transfer

INTRODUCTION: Three-dimensional repair of the zygomatico-maxillary defect calls for an elaborate technique to achieve facial symmetry and correct globe position. We present a technique, which combines the use of a free vascularized soft tissue flap and free bone grafts for repair of composite zygomatico-maxillary defects. PATIENTS: Three patients that underwent radical resection of the maxilla and the zygoma have undergone facial reconstruction using this technique. The mean follow up was 9 months. METHODS: The key points of this technique are: (1) precise reconstruction of the zygomatico-maxillary complex including the orbit; (2) creation of a skeletal framework for canthopexy and suspension of the free flap; (3) repair of through-and-through soft tissue defects with a folded musculocutaneous free flap; and (4) simultaneous harvesting and reconstruction using two surgical teams to reduce the duration of surgery. RESULTS: Reconstruction of the zygomatico-maxillary complex could be successfully accomplished in a single surgical procedure. CONCLUSION: This paper presents a method of repairing zygomatico-maxillary defects with free bone grafts and vascularized soft tissue. However, this concept has yet to be reviewed in the long term.     

Considerable differences exist between prevalent and incident myocardial infarction cohorts derived from the same population

ObjectiveBoth prevalent and incident cohorts have been used in epidemiological and prognostic studies of ischemic heart disease (IHD). This study considers the differences between the cohort types.Study Design and SettingUsing linked primary care, secondary care, and death certification data, prevalent and incident cohorts of people with a first acute myocardial infarction (AMI) were formed from the same population. They were analyzed independently in terms of baseline characteristics and survival to revascularization, another AMI, or death.Results55.7% of the prevalent cohort members were males, with a mean age of 71.0 years (standard deviation [SD]: 12.0). 59.0% of the incident cohort members were males, with a mean age of 64.7 years (SD: 13.3). Over 5 years, a greater proportion of prevalent cases died from any cause (31.4% [95% confidence interval(CI): 28.6–34.3]) and IHD (18.5% [95% CI: 16.2–21.0]) than incident cases (18.0% [95% CI: 15.0–21.4] and 12.2% [95% CI: 9.7–15.2], respectively). Mean time to death was shorter in prevalent cases. There was a small difference in the numbers of subsequent AMIs between cohorts. In the incident cohort, mean time to AMI was shorter. Fewer prevalent cases underwent coronary artery bypass grafting or percutaneous transluminal coronary angioplasty.ConclusionConsiderable differences existed between the two cohorts in terms of baseline characteristics and prognosis. Incident cohorts derived from whole populations should be sought for estimation of survival.     

Construction of a stereotaxic DTI atlas with full diffusion tensor information for studying white matter maturation from childhood to adolescence using tractography‐based segmentations

Reconstruction of white matter (WM) fiber tracts based on diffusion tensor imaging (DTI) is increasingly being used in clinical and research settings to study normal and pathological WM tissue as well as the maturation of this WM tissue. Such fiber tracking (FT) methodology, however, is highly dependent on the manual delineation of anatomical landmarks and the algorithm settings, often rendering the reproducibility and reliability questionable. Predefining these regions of interest on a fractional anisotropy (FA) atlas in standard space has already been shown to improve the reliability of FT results. In this paper, we constructed a new DTI atlas, which contains the complete diffusion tensor information in ICBM152 coordinates. From this high‐dimensional DTI atlas, and using robust FT protocols, we reconstructed a large number of WM tracts. Subsequently, we created tract masks from these fiber tract bundles and evaluated the atlas framework by comparing the reproducibility of the results obtained from our standardized tract masks with regions‐of‐interest labels from the conventional FA‐based WM atlas. Finally, we assessed laterality and age‐related WM changes in 42 normal subjects aged 0 to 18 years using these tractography‐derived tract segmentations. In agreement with previous literature, we observed an FA increase with age, which was mainly due to the decrease of perpendicular diffusivity. In addition, major functional pathways in the language, motor, and limbic system, showed a significant asymmetry in terms of the observed diffusion metrics. Hum Brain Mapp, 2010. © 2009 Wiley‐Liss, Inc.