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Crystalline and quasicrystalline allotropes of Pb are formed by evaporation on the fivefold surface of the icosahedral (i) Ag-In-Yb quasicrystal under ultra-high vacuum. Lead grows in three dimensional quasicrystalline order and subsequently forms fivefold-twinned islands with the fcc(111) surface orientation atop of the quasicrystalline Pb. The islands exhibit specific heights (magic heights), possibly due to the confinement of electrons in the islands. We also study the adsorption behavior of C60 on the two allotropes of Pb. Scanning tunneling microcopy reveals that a high corrugation of the quasicrystalline Pb limits the diffusion of the C60 molecules and thus produces a disordered film, similar to adsorption behavior of the same molecules on the clean substrate surface. However, the sticking coefficient of C60 molecules atop the Pb islands approaches zero, regardless of the overall C60 coverage.

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The structure of the twofold surface of the icosahedral (i-)Ag-In-Yb quasicrystal has been investigated using low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). The LEED confirms that the surface exhibits quasicrystalline long range order with the twofold rotational symmetry expected from the bulk. STM images reveal a step-terrace structure with terrace size comparable to that of the other high symmetry surfaces of the same quasicrystal. The distribution of step heights and high resolution STM images of terraces suggest that the surface terminates at bulk planes that intersect the center of rhombic triacontahedral clusters, the building blocks of the system, as in the case of the threefold and fivefold surfaces of the system. These planes are rich in Yb and In. No facets are observed on the surface, suggesting that the twofold surface is as stable as the other high symmetry surfaces.

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Quasicrystals, materials with aperiodic long-range order, have been found in intermetallics, soft materials such as colloids and supermolecules, and also in two-dimensional monolayer films. Here we present the first example of three-dimensional growth of a single-element quasicrystalline film. Using a hitherto unexplored template, the icosahedral Ag-In-Yb quasicrystal, and various experimental techniques combined with theoretical calculations of adsorption energies, we find that lead atoms deposited on the surface occupy the positions of atoms in the rhombic triacontahedral cluster, the building block of the substrate, and thus grow in layers with different heights and adsorption energies. We show that the adlayer-adlayer interaction is crucial for stabilizing this epitaxial quasicrystalline structure. The finding opens an avenue for further investigation of the impact of the aperiodic atomic order over periodic order on the physical and chemical properties of materials.

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We report a study of the atomic structure of the threefold icosahedral (i-)Ag-In-Yb quasicrystal surface using scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). The LEED confirms that the surface exhibits quasicrystalline long-range order with the threefold symmetry expected from the bulk. The STM reveals large atomically flat terraces separated by steps of different heights. A comparison of atomically resolved STM images for the terraces and the step-height distribution with the bulk structure of isostructural i-Cd-Yb shows that the terraces are formed at bulk planes intersecting the centers of the rhombic triacontahedral clusters that make up the bulk structure of the system. However, the stability of particular terraces may be influenced by the density of atoms in the interstices (glue atoms that bind the clusters) in the terraces and also by the chemical environment in the underlying atomic plane. The surface exhibits screw dislocations, which is explained in terms of a continuous atomic density along the threefold axis.

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Nine patients were treated with ten intertransverse process lumbar spine anthrodeses using fresh-frozen crushed corticocancellous allogeneic bone as graft material. No instrumentation was used. The clinical and roentgenographic follow-up period ranged from one to three years. Seven procedures showed successful arthrodesis and three demonstrated pseudarthroses. Increased age and systemic disease were associated with an increased risk of pseudarthrosis. Persistent back pain was associated with pseudarthrosis. Compared with 58 patients treated with intertransverse process lumbar fusion with autogeneic iliac bone as graft material, the overall fusion rate is inferior: 70% versus 92%, respectively.

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The case of a 33-year-old woman who presented with abdominal pain referable to the lower abdomen is discussed. She had had an uncomplicated intrauterine abortive procedure two weeks earlier. It was determined that a ruptured ectopic pregnancy was the etiology of her abdominal pain. The rare phenomenon of combined intrauterine and extrauterine pregnancy is discussed.

PIP: In Ohio, a 33-year old woman who had never had an ectopic pregnancy presented at an emergency facility not physically attached to a hospital with abdominal pain over 24 hours which had become more intense during the preceding 4 hours. She did not have vaginal bleeding, diarrhea, vomiting, or pain while urinating. 2 weeks earlier she had a voluntary intrauterine abortion at 8 weeks' gestation. She had intercourse 1 week before coming to the emergency facility. She had widespread tenderness in her abdomen, especially in the lower areas. Blood cell studies suggested an infection. The attending physician presumed her to have pelvic inflammatory disease (PID) as a result of either sexual intercourse or the elective abortion. The physician called for a urinary beta human chorionic gonadotropin test to determine whether placental tissue remained in the uterus. It was positive. 60 minutes after admission, the supine patient's pain increased and her blood pressure dropped to 80/50 mm Hg from 100/60 mm Hg at admission. After administering Ringer's solution, the health team sat her up and she fainted. A repeat cell count indicated sepsis. Her blood pressure decreased to 60 by Doppler and the physician continued to give her fluids and began dopamine. After the team stabilized her, they transferred her to a hospital. Her private physician examined her and then began surgery. The physician found a tubal pregnancy and removed the affected tube and ovary. She recuperated completely. Combined intrauterine and extrauterine pregnancy occurs once in every 30,000 cases. Previous PID, use of ovulation inducing medication, and in vitro fertilization with embryo transfer increases the likelihood of this type of pregnancy occurring. Physicians should consider this possibility if a woman has any of these histories and a combination of abdominal pain, adnexal mass with pain and tenderness, peritoneal irritation, and an enlarged uterus.

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Retained hardware embedded deep in soft tissues or overgrown with bone poses a challenge to the surgeon assigned to its removal. A prototype of a hand-held electromagnetic metal detector-locater was used to localize retained hardware. Stainless-steel pins, screws, plates, and staples were located in 21 consecutive hardware removal procedures in 19 pediatric patients. Time to find the hardware, length of incision, blood loss, tissue maceration, and operative time were minimized. This preliminary study suggests that a metal locater may be a valuable tool when retained hardware is not palpable or readily apparent.

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Cementless fixation in total hip arthroplasty is increasingly popular because of the failure rates of cemented components, particularly in younger patients. The reported European studies with cementless acetabular implants and the relatively short-term American studies suggest that loosening is not a problem with any of the designs in clinical use. This point of view is reminiscent of that regarding cemented acetabular components prior to the realization that cemented acetabular failure was a delayed long-term phenomenon. Cementless acetabular components are principally of two types, threaded and porous coated. Prior to this study, there was little clinical or experimental evidence to indicate which design gains superior fixation and which is most likely to maintain long-term fixation and durability. Fixation of threaded and porous-coated components was evaluated mechanically and histologically in dogs after weight-bearing periods of two and six months. The threaded specimens were significantly looser than the porous-coated specimens at both two and six months. There was a trend toward loosening of both types of components with time. Fibrous tissue alone appeared to invest all of the threaded components, whereas bone and fibrous-tissue ingrowth appeared to incorporate the porous components. The mineral apposition rate for the components was not significantly different between the two components or between different regions in the specimens.

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The progression of femoral head osteonecrosis (FHON) culminates in destruction of the hip joint, a devastating consequence for young people who are predominantly affected. Core decompression, as a means of ameliorating the disease, was evaluated in 45 hips in 33 patients with nontraumatic FHON. The mean clinical and roentgenographic follow-up period was three years (range, 1-7 years). None of the ten Ficat Stage I hips progressed, 11 of 26 Stage II hips progressed, and five of nine Stage III hips progressed to coxarthrosis. In those hips in which there was an association with steroid therapy, there was 50% progression when steroids were continued, compared with 22% progression when steroids had been discontinued. Core decompression is prescribed for Ficat Stage I and II. Patients on continuous post-operative treatment with steroids for associated conditions should be advised of the high risk of progression.

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