Risk factors for failure of the 36 mm metal-on-metal Pinnacle total hip arthroplasty system:a retrospective single-centre cohort study

Aims: To determine 10-year failure rates following 36mm metal-on-metal (MoM) Pinnacle total hip replacement (THR), and identify predictors of failure. Methods: We retrospectively assessed a single-centre cohort of 569 primary 36mm MoM Pinnacle THRs (all Corail stems) followed up since 2012 according to MHRA recommendations. Allcause failure rates (all-cause revision, and non-revised cross-sectional imaging failures) were calculated, with predictors for failure identified using multivariable Cox regression. Results: Failure occurred in 97 hips (17.0%). The 10-year cumulative failure rate was 27.1% (95% CI=21.6%-33.7%). Primary implantation from 2006 onwards (Hazard Ratio (HR)=4.30; CI=1.82-10.1; p=0.001) and bilateral MoM hip arthroplasty (HR=1.59; CI=1.03-2.46; p=0.037) predicted failure. The effect of implantation year on failure varied over time. From 4-years onwards following surgery, hips implanted since 2006 had significantly higher failure rates (8-years=28.3%; CI=23.1%-34.5%) compared to hips implanted before 2006 (8- years=6.3%; CI=2.4%-15.8%) (HR=15.2; CI=2.11-110.4; p=0.007). Conclusion: We observed that 36mm MoM Pinnacle THRs have an unacceptably high 10-year failure rate, especially if implanted from 2006 onwards or in bilateral MoM patients. Our findings regarding implantation year and failure support recent concerns about the device manufacturing process. We recommend all patients undergoing implantation since 2006 and those with bilateral MoM hips undergo regular investigation, regardless of symptoms

CANDELS : constraining the AGN-merger connection with host morphologies at z ~ 2

Using Hubble Space Telescope/WFC3 imaging taken as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we examine the role that major galaxy mergers play in triggering active galactic nucleus (AGN) activity at z ~ 2. Our sample consists of 72 moderate-luminosity (L X ~ 1042-44 erg s-1) AGNs at 1.5 < z < 2.5 that are selected using the 4 Ms Chandra observations in the Chandra Deep Field South, the deepest X-ray observations to date. Employing visual classifications, we have analyzed the rest-frame optical morphologies of the AGN host galaxies and compared them to a mass-matched control sample of 216 non-active galaxies at the same redshift. We find that most of the AGNs reside in disk galaxies (51.4+5.8 - 5.9%), while a smaller percentage are found in spheroids (27.8+5.8 - 4.6%). Roughly 16.7+5.3 - 3.5% of the AGN hosts have highly disturbed morphologies and appear to be involved in a major merger or interaction, while most of the hosts (55.6+5.6 - 5.9%) appear relatively relaxed and undisturbed. These fractions are statistically consistent with the fraction of control galaxies that show similar morphological disturbances. These results suggest that the hosts of moderate-luminosity AGNs are no more likely to be involved in an ongoing merger or interaction relative to non-active galaxies of similar mass at z ~ 2. The high disk fraction observed among the AGN hosts also appears to be at odds with predictions that merger-driven accretion should be the dominant AGN fueling mode at z ~ 2, even at moderate X-ray luminosities. Although we cannot rule out that minor mergers are responsible for triggering these systems, the presence of a large population of relatively undisturbed disk-like hosts suggests that the stochastic accretion of gas plays a greater role in fueling AGN activity at z ~ 2 than previously thought

Observing Supermassive Black Holes across cosmic time: from phenomenology to physics

In the last decade, a combination of high sensitivity, high spatial resolution observations and of coordinated multi-wavelength surveys has revolutionized our view of extra-galactic black hole (BH) astrophysics. We now know that supermassive black holes reside in the nuclei of almost every galaxy, grow over cosmological times by accreting matter, interact and merge with each other, and in the process liberate enormous amounts of energy that influence dramatically the evolution of the surrounding gas and stars, providing a powerful self-regulatory mechanism for galaxy formation. The different energetic phenomena associated to growing black holes and Active Galactic Nuclei (AGN), their cosmological evolution and the observational techniques used to unveil them, are the subject of this chapter. In particular, I will focus my attention on the connection between the theory of high-energy astrophysical processes giving rise to the observed emission in AGN, the observable imprints they leave at different wavelengths, and the methods used to uncover them in a statistically robust way. I will show how such a combined effort of theorists and observers have led us to unveil most of the SMBH growth over a large fraction of the age of the Universe, but that nagging uncertainties remain, preventing us from fully understating the exact role of black holes in the complex process of galaxy and large-scale structure formation, assembly and evolution.Comment: 46 pages, 21 figures. This review article appears as a chapter in the book: "Astrophysical Black Holes", Haardt, F., Gorini, V., Moschella, U and Treves A. (Eds), 2015, Springer International Publishing AG, Cha