Water jet cutting for bones and bone cement--parameter study of possibilities and limits of a new method]

Water jet techniques have been used in industrial cutting, drilling and cleaning applications for more than 30 years. Plain water is typically used for the cutting of non-metallic materials. The addition of abrasive substances to the stream allows almost any material to be cut. The first medical applications were reported in the early 1980s, when the water jet was used to cut organs. The present study investigates the use of water jet cutting technology for endoprosthesis revision surgery. Bone and PMMA (polymethylmethacrylate) samples were cut at different pressures using an industrial water jet cutting device. Using plain water at 400 bar, PMMA was cut selectively without damaging the bone; above 400 bar, bone was also cut, but the cutting depths in PMMA were significantly greater (p < 0.05). Adding a water-soluble abrasive disaccharide to the water results in a significantly higher removal rate for both materials (p < 0.05), but selectivity is lost, although the differences in cutting depth between the two materials was significant (p < 0.05). With an abrasive, the quality of the cut was better for both materials. The water jet technology--in particular the abrasive technique--can be used to cut biomaterials such as bone and bone cement. The diameter of the jet is a great advantage when working in the confined area at the prosthesis interface. The cutting process is essentially cold, thus eliminating a thermal effect, and the jet reaction forces are relatively low. Accurate manipulation of the hydro jet nozzle is possible both manually and by robot. The results obtained show that it is possible to remove prostheses with this cutting technique, rapidly and with little damage to the surrounding tissue. Problem areas are the development of sterile pumps and the "depth control" of the jet.     

Preparing Bone Sections for Radioautography

The method eliminates all contact of bone with aqueous solutions. One hundred to 200µ sections are first cut with a guided circular saw. These sections are simultaneously embedded and mounted on glass slides by means of a clear thermoplastic cement, Gelva. The mounted bone sections are then ground to 5-25µ on fine silicon carbide paper. The sections are finally polished with levigated alumina on a cloth pad. A procedure for preparing contact radioautograms of ground bone sections is given and the results obtained are illustrated.     

The pulsed water jet for selective removal of bone cement during revision arthroplasty]

Conventional tools used in prosthetic revision surgery have a limited range of action within the narrow cement mantle. Water jet cutting technology permits tiny and precisely controlled cuts, and may therefore be an alternative method of bone cement removal. Our study compares the cutting performance on bone cement (PMMA) and bone of a pulsed water jet and a continuous water jet. The aim of the study was to establish whether selective removal of PMMA is possible. 55 bone specimens (bovine femora) and 32 specimens of PMMA were cut with a continuous and a pulsed water jet at different pressures (40 MPa, 60 MPa) and pulse frequencies (0Hz, 50Hz, 250Hz). To ensure comparability of the results, the depths of cut were related to the hydraulic power of that part of the jet actually impinging on the material. While for PMMA the power-related depth of cut increased significantly with the pulse frequency, this did not apply to bone. The cuts produced in bone were sharp-edged. Since PMMA is more brittle than bone, the water jet caused cracks that enlarged further until particles of bone broke away. Although selective removal of PMMA without doing damage to the bone was not possible at the investigated settings of the jet parameters, the results do show that a pulsed water jet can cut bone cement much more effectively than bone. This is an important advantage over conventional non-selective tools for the removal of bone cement.     

Indirect effects of insect herbivory on leaf gas exchange in soybean

Herbivory can affect plant carbon gain directly by removing photosynthetic leaf tissue and indirectly by inducing the production of costly defensive compounds or disrupting the movement of water and nutrients. The indirect effects of herbivory on carbon and water fluxes of soybean leaves were investigated using gas exchange, chlorophyll fluorescence and thermal imaging. Herbivory by Popillia japonica and Helicoverpa zea (Boddie) caused a 20–90% increase in transpiration from soybean leaflets without affecting carbon assimilation rates or photosynthetic efficiency (Φ_PSII). Mechanical damage to interveinal tissue increased transpiration up to 150%. The spatial pattern of leaf temperature indicated that water loss occurred from injuries to the cuticle as well as from cut edges. A fluorescent tracer (sulforhodamine G) indicated that water evaporated from the apoplast approximately 100 µm away from the cut edges of damaged leaves. The rate of water loss from damaged leaves remained significantly higher than from control leaves for 6 d, during which time they lost 45% more water than control leaves (0.72 mol H₂O per cm of damaged perimeter). Profligate water loss through the perimeter of damaged tissue indicates that herbivory may exacerbate water stress of soybeans under field conditions.     

Tools for high tibial wedge osteotomy

Surgical instruments are described which have been developed for use in high tibial wedge osteotomy. This operation is a treatment for degenerative arthritis of the knee in which one compartment of the joint is predominantly affected resulting in a deformity. Realignment of the bones alters the load distribution on the joint which can relieve pain. Tools have been designed to facilitate the removal of a wedge of bone cut at a precise angle calculated from load bearing radiographs. The tools are a marker pin guide and a saw guide; their use has resulted in accurate bone realignment confirmed by postoperative radiographs.     

Measuring the resolution of uncompressed plastic sections cut using an oscillating knife ultramicrotome

Thin sections of biological tissue embedded in plastic and cut with an ultramicrotome do not generally display useful details smaller than approximately 50 A in the electron microscope. However, there is evidence that before sectioning the embedded tissue can be substantially better preserved, which suggests that cutting is when major damage and loss of resolution occurs. We show here a striking example of such damage in embedded insect flight muscle fibres. X-ray diffraction of the embedded muscle gave patterns extending to 13A, whereas sections cut from the same block showed only approximately 50 A resolution. A possible source of this damage is the substantial compression that was imposed on sections during cutting. An oscillating knife ultramicrotome eliminates the compression and it seemed possible that sections cut with such a knife would show substantially improved preservation. We used the oscillating knife to cut sections from the embedded muscle and from embedded catalase crystals. Preservation with and without oscillation was assessed in Fourier transforms of micrographs. Sections cut with the knife oscillating did not show improved preservation over those cut without. Thus compression during cutting does not appear to be the major source of damage in plastic sections, and leaves unexplained the 50 A versus 13A discrepancy between block and section preservation. The results nevertheless suggest that improvements in ultramicrotomy will be important for bringing thin-sectioning and tomography of plastic-embedded cells and tissues to the point where macromolecule shapes can be resolved.     

Sticky Wax Infiltration in the Preparation of Sawed Undecalcified Bone Sections

The undecalcified bone specimen was surfaced by an ordinary motor-driven circular saw. After thorough drying in air, the specimen was infiltrated with melted Caulk sticky wax (L. D. Caulk Co., Milford, Del., 19963) without casting in a block. The specimen was affixed to the Gillings-Hamco thin-sectioning machine with cut surface parallel to the circular diamond blade. Prior to sawing each section, the specimen surface was blown dry and coated with a thin supporting layer of stick wax. The section was then attached to an albumen-coated glass slide with the newly cut surface facing the slide. After drying in room temperature, the slide was soaked in xylene to partially dissolve the sticky wax, and the loosened residue was removed subsequently by gentle brushing. The section was mounted and covered with a coverglass. Sections 50-100 μ thick were prepared satisfactorily by this method. The advantages of using sticky wax as an infiltration medium depend on its physical properties: it is gluey when melted, and holds the bony trabeculae together; it becomes hard and nonsticky at room tempperature, and can be sawed together with bone tissue. Since a new layer of wax blends readily with the old wax surface, it allows the important supportive coating of wax to be added to the sawing surface for each section cutting     

The migration of osteoblasts

Summary The endocranial matrix surfaces of parietal bones of 2-week old Albino Wistar rats were partly denuded of osteoblasts and then cultured for various periods up to 24 h, in control or PTE-enriched medium. They were examined by scanning electron microscopy and evidence for cell locomotion was found. Osteoblasts traversed the denuded bone surface and cut edges of bone in either medium, and cells also migrated out from vascular channels.Glass spicules were placed on the otherwise undisturbed osteoblast layer in similar organ cultures for 2, 3 or 5 days. Osteoblasts migrated from the bone to populate the glass, negotiating any angle. The cells in PTE-enriched media were always aligned parallel to one another and elongated, tended to align with the edges of the glass and, in time, formed a substrate of aligned fibrils whose axes were parallel to those of the cells. Osteoblasts in control medium on glass showed variable degrees of alignment and elongation and were less influenced by the edges of the glass. Non-locomotory, nearly equidiametrical cells on glass in 5d control cultures had formed a substrate of randomly oriented fibrils.Migrating osteoblasts on bone matrix did not have leading edge ruffles; isolated, migrating ones on glass did.We thank Elaine Bailey for expert assistance; Dr. Martin Evans for the facilities of his laboratory; Dr. Nicholas Maroudas for his erudite interest in our work; and the M.R.C. for financial support.     

The prominent mandibular angle: preoperative management, operative technique, and results in 42 patients

A prominent mandibular angle is considered to be unattractive in the Orient because it gives the face a square and muscular appearance. While described infrequently in the United States, this entity is commonly encountered in the Orient owing to different facial characteristics and different aesthetic sensibilities. We present a retrospective study of 42 female patients who presented requesting the reduction of a prominent mandibular angle for cosmetic reasons. We describe our approach, which utilizes formal planimetry, cephalometric tracings, and Panorex mandibular radiographs. We utilize the intraoral approach and use an oscillating saw to resect the predetermined segment of bone. In 18 of the 42 patients, we resected muscle as well. We also describe using the preauricular incision in a patient undergoing a concomitant rhytidectomy. Our cosmetic results have been generally satisfactory, with only one inaccurate osteotomy. We had three infections which resolved without sequelae.     

Epoxy Resin Embedding in Contrast Radioautography of Bones and Teeth

Contrast, or low-resolution, radioautographs of teeth and large specimens of bone are made from plane, polished surfaces of such material embedded in plastic. The specimen is cut with a motor-driven circular saw, fixed, dehydrated, and defatted with anhydrous acetone and ether. It is then infiltrated with a mixture of epoxy resin and reactive hardener. The resin-infiltrated specimen is placed in an easily constructed mold of aluminum and Lucite. Polymerization is complete in 4-6 hr. The surface of the specimen is exposed by machining and/or abrading. The prepared surface is apposed to an X-ray type emulsion to produce a radioautograph. The resolution obtainable is estimated to be 100-200 β.     

Expression of vascular antigens by bone cells during bone regeneration in a membranous bone distraction system

An in vivo system of membranous bone formation during distraction has been investigated in order to follow cells that express vascular markers with the objective of understanding the neovascularization process. Concomitantly, sustained proliferation of preskeletal cells was achieved through the application of mechanical force. New capillaries and leading edges that arose by angiogenesis from the periosteal and mucosal surfaces and invaded the central zone of the regenerating distraction tissue temporally preceded the growth of delicate woven bone trabeculae from both edges of the cut bone. Concentrically arranged 'onion-like' configurations were abundant in paracentral zones and in association with mesenchymal condensations, suggesting their de novo formation in situ. Vascular specific markers, the angiopoietin receptor Tie-2 and factor VIII-related antigen (FVIIIrAg), were localized immunohistochemically in order to follow cells of vascular origin. Endothelial cells of the new capillaries, centrally located cells of the concentric configurations, pericytes, and most of the adjacent polygonal mesenchymal cells stained positively with specific antibodies to both antigens. Moreover, preosteoblasts and osteoblasts that lie adjacent to or already embedded in the osteiod of the newly formed trabeculae were also FVIIIrAg and Tie-2 immunopositive. As the source of the bone-forming cells in regenerating tissue during distraction is not yet fully understood, this observation might support the possibility of their vascular origin.     

The Measurement of Stomatal Responses to Stimuli in Leaves and Leaf Discs

A comparison has been made of stomatal responses in intact leaves,leaf discs supplied with water via their cut edges and leafdiscs floating on water. Xanthium pennsylvanicum leaf discswatered via their cut edges appeared to be more turgid thanintact leaves; this considerably slowed down the rate of stomatalopening but it slightly increased the final steady-state stomatalopening. When the water potential of such leaf discs was loweredby pre-treatment with mannitol solutions rates of stomatal openingincreased whereas maximum steady-state openings decreased. In tobacco leaf discs floating on water the stomata in contactwith water were wider open than those in contact with normalair and they did not respond to treatment with carbon dioxide-freeair. The rate of photosynthesis was severely reduced in tobaccoleaf discs floating with the lower epidermis on water, mostprobably owing to the slow rate of diffusion of carbon dioxidein water. By floating such discs on osmotica the degree of stomatalopening was increased, however, a response to treatment withcarbon dioxide-free air was still not measurable. It is postulatedthat, on account of the relative unavailability of carbon dioxidefrom the water, the carbon dioxide concentration in the substomatalcavities of the lower surface is abnormally low, irrespectiveof whether ordinary air or carbon dioxide-free air is availableto the upper surface. A comparison between porometer readings and measurements ofsiliconerubber impressions of stomatal pores taken from insidethe porometer cup confirmed that the silicone-rubber impressionmethod of assessing stomatal responses to stimuli has severelimitations, especially at small stomatal apertures.     

Improved Paraffin Sectioning with Etched Microtome Knife Edges

Carbon steel microtome knives etched with 0.1 N HNO₃ for 2 min display a very sharp cutting edge. Over a period of 3 yr no damage to the steel has been detected. The effect on paraffin sectioning was observed by comparing acid-treated knives with nonetched but well-sharpened ones. Sections of whole eyes cut with an etched blade showed approximately 15% less compression of the parffin matrix than those sectioned with an untreated knife. Tissues selected from routine autopsy material presented approximately 9% reduction in compression. As a result, excellent ribbons of sections could be cut from 5-7 μ and floated on water at 42—46 C with a minimum of folds or distortion. Etching improved sectioning when knife edges having bevel angles in a range of 31-39° were used, and also when the bevel was decreased to 20°, but the 20° edge gave impractically short service.     

Staining of Different Tissues in Thick Epoxy Resin-Impregnated Sections of Human Fetuses

Sections of undecalcified human fetuses, fixed in formaldehyde, embedded in the epoxy resin Biodur E 12 and cut on a diamond-wire saw were stained according to a slight modification of the method described by Laczko and Levai. The sections were immersed in a methylene blue/azure II solution at 90 C for at least 3 min and counterstained with a basic fuchsin solution at the same temperature. Differential staining was as follows: bone stained pinkish; cartilage, violet; collagen fibers, blue-violet; elastic fibers, red and muscle fibers, green-blue. Most other tissues were stained blue-violet against the transparent background of the embedding epoxy resin. Thanks to the distinct and differential staining of each tissue, contrast is sufficient for black and white as well as for color photography.     

Apparatus for Bone Sectioning

A new type of apparatus for cutting 100-200µ sections of bone is described. This apparatus consists of an especially designed bone vise and a mounted circular saw with three directional movement controls. The saw is driven by one D.C. motor and its vertical movement assembly is driven by another. Their speeds can be regulated individually. The bone sections may be made serially at intervals of 0.3 to 0.5 mm. and bones as large as 2 cm. in diameter or longitudinal slabs of larger bones may be sectioned.     

Staining of different tissues in thick epoxy resin-impregnated sections of human fetuses

Sections of undecalcified human fetuses, fixed in formaldehyde, embedded in the epoxy resin Biodur E 12 and cut on a diamond-wire saw were stained according to a slight modification of the method described by Laczkó and Lévai. The sections were immersed in a methylene blue/azure II solution at 90 C for at least 3 min and counterstained with a basic fuchsin solution at the same temperature. Differential staining was as follows: bone stained pinkish; cartilage, violet; collagen fibers, blue-violet; elastic fibers, red and muscle fibers, green-blue. Most other tissues were stained blue-violet against the transparent background of the embedding epoxy resin. Thanks to the distinct and differential staining of each tissue, contrast is sufficient for black and white as well as for color photography.     

Recent advances in bone marrow biopsy pathology

The second quarter of 2009 saw steady advances in bone marrow biopsy (BMB) pathology. The following publications are a personal selection of the highlights. Quality issues in diagnostic immunohistochemistry for BMB have largely been ignored in external quality assurance programmes, and this issue is highlighted. In other areas, publications reflecting advances in flow cytometry and aspirate morphology are discussed where translation to the BMB is possible. Classifications undergo constant change, and several publications address the redefinition of the cut off points between malignancy, benign, and normal. Lastly, current scientific research is presented where it is relevant to the understanding of BMB pathobiology.     

Preparation of large temporomandibular joint specimens for pathological study

Ten fresh temporomandibular joint (TMJ) specimens about 5 X 4.5 X 3.5 cm in size were removed at autopsy by 5 cuts according to appropriate anatomical landmarks. After routine formalin fixation, the whole-TMJ specimens were wrapped with a thin layer of self-curing resin and then cut with a low speed bone saw along the parasagittal plane predetermined by x-ray guidance. Each specimen was serially cut into 4 to 5 parallel slices of 3 mm thickness, which were then decalcified with 14% EDTA and embedded in paraffin. Histological sections of 5 microns were stained with hematoxylin and eosin. The procedures were accomplished within 20 to 24 days after autopsy. With this technique, the anatomical interrelationships among the various joint components could be maintained and the macroscopic and microscopic topography of the TMJ could be studied in the desired reference plane. Therefore, the corresponding changes among the joint components in a diseased TMJ could be thoroughly examined. This technique was also applicable for the study of large specimens containing both hard and soft tissues.     

Large area sectioning for morphologic studies of nonhuman primate nasal cavities

The nasal region is important for studies in inhalation toxicology but is difficult to prepare for histological examination, especially in species as large as primates. A method for the histologic preparation of undecalcified, complete transverse sections of the nonhuman primate nasal cavity is summarized as follows. After removal of excess soft tissue, mandible and calvaria, the head is fixed in 10% neutral buffered formalin. The nasal region is transversely sectioned into serial 3-mm-thick blocks from the nares to the posterior aspect of the soft palate using a low speed saw with a water-cooled diamond-coated blade. The blocks are embedded in a mixture of glycol and methyl methacrylates, with polyethylene glycol-1500 and dibutylphthalate as plasticizers. The plastic blocks average 5.0 x 5.0 x 1.5 cm; 2-4 microns sections are cut on an automated sliding microtome. In spite of the size of the blocks, this technique yields complete transverse sections of the nasal cavities with excellent morphologic detail. The sections are amenable to a wide range of staining procedures. The procedure lends itself to autoradiographic studies. The embedding mixture is ideally suited for studies of undecalcified bone and teeth.     

Time-dependent deformations in bone cells exposed to fluid flow in vitro: investigating the role of cellular deformation in fluid flow-induced signaling

Numerous experiments have shown fluid flow to be a potent stimulator of bone cells in vitro, suggesting that fluid flow is an important physical signal in bone mechanotransduction. In fluid flow experiments, bone cells are exposed to both time-dependent (e.g., oscillating or pulsing) and time-independent (e.g., steady) flow profiles. Interestingly, the signaling response of bone cells shows dependence on loading frequency and/or rate that has been postulated to be due to viscoelastic behavior. Thus, the objective of this study was to investigate the time-dependent deformations of bone cells exposed to fluid flow in vitro. Specifically, our goal was to characterize the mechanical response of bone cells exposed to oscillatory flow from 0.5 to 2.0 Hz and steady flow, since these flow profiles have previously been shown to induce different morphological and biochemical responses in vitro. By tracking cell-bound sulfate and collagen coated fluorescent beads of varying sizes, we quantified the normalized peak deformation (peak displacement normalized by the maximum peak displacement observed for all frequencies) and phase lag in bone cells exposed to 1.0 Pa oscillating flow at frequencies of 0.5-2.0 Hz. The phase lag was small (3-10 degrees ) and frequency dependent, while the normalized peak displacements decreased as a weak power law of frequency ( approximately f(-0.2)). During steady flow, the cells exhibited a nearly instantaneous deformation, followed by creep. Our results suggest that while substantial viscous deformation may occur during steady flow (compared to oscillating flow at approximately 1 Hz), bone cells behave primarily as elastic bodies when exposed to flow at frequencies associated with habitual loading.