Various techniques and tools for encoding and decoding (e.g., in a video encoder/decoder) binary information (e.g., skipped macroblock information) are described. In some embodiments, the binary information is arranged in a bit plane, and the bit plane is coded at the picture/frame layer. The encoder and decoder process the binary information and, in some embodiments, switch coding modes. For example, the encoder and decoder use normal, row-skip, column-skip, or differential modes, or other and/or additional modes. In some embodiments, the encoder and decoder define a skipped macroblock as a predicted macroblock whose motion is equal to its causally predicted motion and which has zero residual error. In some embodiments, the encoder and decoder use a raw coding mode to allow for low-latency applications.

Digital video consumes large amounts of storage and transmission capacity. A typical raw digital video sequence includes 15 or 30 frames per second. Each frame can include tens or hundreds of thousands of pixels (also called pels). Each pixel represents a tiny element of the picture. In raw form, a computer commonly represents a pixel with 24 bits. Thus, the number of bits per second, or bit rate, of a typical raw digital video sequence can be 5 million bits/second or more.
Most computers and computer networks lack the resources to process raw digital video. For this reason, engineers use compression (also called coding or encoding) to reduce the bit rate of digital video. Compression can be lossless, in which quality of the video does not suffer but decreases in bit rate are limited by the complexity of the video. Or, compression can be lossy, in which quality of the video suffers but decreases in bit rate are more dramatic. Decompression reverses compression.
In general, video compression techniques include intraframe compression and interframe compression. Intraframe compression techniques compress individual frames, typically called I-frames, or key frames. Interframe compression techniques compress frames with reference to preceding and/or following frames, and are called typically called predicted frames, P-frames, or B-frames.
Microsoft Corporation's Windows Media Video, Version 7 ["WMV7"] includes a video encoder and a video decoder. The WMV7 encoder uses intraframe and interframe compression, and the WMV7 decoder uses intraframe and interframe decompression.
A. Intraframe Compression in WMV7
FIG. 1 illustrates block-based intraframe compression (100) of a block (105) of pixels in a key frame in the WMV7 encoder. A block is a set of pixels, for example, an 8×8 arrangement of pixels. The WMV7 encoder splits a key video frame into 8×8 blocks of pixels and applies an 8×8 Discrete Cosine Transform ["DCT"] (110) to individual blocks such as the block (105). A DCT is a type of frequency transform that converts the 8×8 block of pixels (spatial information) into an 8×8 block of DCT coefficients (115), which are frequency information. The DCT operation itself is lossless or nearly lossless. Compared to the original pixel values, however, the DCT coefficients are more efficient for the encoder to compress since most of the significant information is concentrated in low frequency coefficients (conventionally, the upper left of the block (115)) and many of the high frequency coefficients (conventionally, the lower right of the block (115)) have values of zero or close to zero.
The encoder then quantizes (120) the DCT coefficients, resulting in an 8×8 block of quantized DCT coefficients (125). For example, the encoder applies a uniform, scalar quantization step size to each coefficient, which is analogous to dividing each coefficient by the same value and rounding. For example, if a DCT coefficient value is 163 and the step size is 10, the quantized DCT coefficient value is 16. Quantization is lossy. The reconstructed DCT coefficient value will be 160, not 163. Since low frequency DCT coefficients tend to have higher values, quantization results in loss of precision but not complete loss of the information for the coefficients. On the other hand, since high frequency DCT coefficients tend to have values of zero or close to zero, quantization of the high frequency coefficients typically results in contiguous regions of zero values. In addition, in some cases high frequency DCT coefficients are quantized more coarsely than low frequency DCT coefficients, resulting in greater loss of precision/information for the high frequency DCT coefficients.
The encoder then prepares the 8×8 block of quantized DCT coefficients (125) for entropy encoding, which is a form of lossless compression. The exact type of entropy encoding can vary depending on whether a coefficient is a DC coefficient (lowest frequency), an AC coefficient (other frequencies) in the top row or left column, or another AC coefficient.
The encoder encodes the DC coefficient (126) as a differential from the DC coefficient (136) of a neighboring 8×8 block, which is a previously encoded neighbor (e.g., top or left) of the block being encoded. (FIG. 1 shows a neighbor block (135) that is situated to the left of the block being encoded in the frame.) The encoder entropy encodes (140) the differential.
The entropy encoder can encode the left column or top row of AC coefficients as a differential from a corresponding column or row of the neighboring 8×8 block. FIG. 1 shows the left column (127) of AC coefficients encoded as a differential (147) from the left column (137) of the neighboring (to the left) block (135). The differential coding increases the chance that the differential coefficients have zero values. The remaining AC coefficients are from the block (125) of quantized DCT coefficients.
The encoder scans (150) the 8×8 block (145) of predicted, quantized AC DCT coefficients into a one-dimensional array (155) and then entropy encodes the scanned AC coefficients using a variation of run length coding (160). The encoder selects an entropy code from one or more run/level/last tables (165) and outputs the entropy code.
A key frame contributes much more to bit rate than a predicted frame. In low or mid-bit rate applications, key frames are often critical bottlenecks for performance, so efficient compression of key frames is critical.
FIG. 2 illustrates a disadvantage of intraframe compression such as shown in FIG. 1. In particular, exploitation of redundancy between blocks of the key frame is limited to prediction of a subset of frequency coefficients (e.g., the DC coefficient and the left column (or top row) of AC coefficients) from the left (220) or top (230) neighboring block of a block (210). The DC coefficient represents the average of the block, the left column of AC coefficients represents the averages of the rows of a block, and the top row represents the averages of the columns. In effect, prediction of DC and AC coefficients as in WMV7 limits extrapolation to the row-wise (or column-wise) average signals of the left (or top) neighboring block. For a particular row (221) in the left block (220), the AC coefficients in the left DCT coefficient column for the left block (220) are used to predict the entire corresponding row (211) of the block (210).
B. Interframe Compression in WMV7
Interframe compression in the WMV7 encoder uses block-based motion compensated prediction coding followed by transform coding of the residual error. FIGS. 3 and 4 illustrate the block-based interframe compression for a predicted frame in the WMV7 encoder. In particular, FIG. 3 illustrates motion estimation for a predicted frame (310) and FIG. 4 illustrates compression of a prediction residual for a motion-estimated block of a predicted frame.
The WMV7 encoder splits a predicted frame into 8×8 blocks of pixels. Groups of 4 8×8 blocks form macroblocks. For each macroblock, a motion estimation process is performed. The motion estimation approximates the motion of the macroblock of pixels relative to a reference frame, for example, a previously coded, preceding frame. In FIG. 3, the WMV7 encoder computes a motion vector for a macroblock (315) in the predicted frame (310). To compute the motion vector, the encoder searches in a search area (335) of a reference frame (330). Within the search area (335), the encoder compares the macroblock (315) from the predicted frame (310) to various candidate macroblocks in order to find a candidate macroblock that is a good match. The encoder can check candidate macroblocks every pixel or every ½ pixel in the search area (335), depending on the desired motion estimation resolution for the encoder. Other video encoders check at other increments, for example, every ¼ pixel. For a candidate macroblock, the encoder checks the difference between the macroblock (315) of the predicted frame (310) and the candidate macroblock and the cost of encoding the motion vector for that macroblock. After the encoder finds a good matching macroblock, the block matching process ends. The encoder outputs the motion vector (entropy coded) for the matching macroblock so the decoder can find the matching macroblock during decoding. When decoding the predicted frame (310), a decoder uses the motion vector to compute a prediction macroblock for the macroblock (315) using information from the reference frame (330). The prediction for the macroblock (315) is rarely perfect, so the encoder usually encodes 8×8 blocks of pixel differences (also called the error or residual blocks) between the prediction macroblock and the macroblock (315) itself.
FIG. 4 illustrates the computation and encoding of an error block (435) for a motion-estimated block in the WMV7 encoder. The error block (435) is the difference between the predicted block (415) and the original current block (425). The encoder applies a DCT (440) to error block (435), resulting in 8×8 block (445) of coefficients. Even more than was the case with DCT coefficients for pixel values, the significant information for the error block (435) is concentrated in low frequency coefficients (conventionally, the upper left of the block (445)) and many of the high frequency coefficients have values of zero or close to zero (conventionally, the lower right of the block (445)).
The encoder then quantizes (450) the DCT coefficients, resulting in an 8×8 block of quantized DCT coefficients (455). The quantization step size is adjustable. Again, since low frequency DCT coefficients tend to have higher values, quantization results in loss of precision, but not complete loss of the information for the coefficients. On the other hand, since high frequency DCT coefficients tend to have values of zero or close to zero, quantization of the high frequency coefficients results in contiguous regions of zero values. In addition, in some cases high frequency DCT coefficients are quantized more coarsely than low frequency DCT coefficients, resulting in greater loss of precision/information for the high frequency DCT coefficients.
The encoder then prepares the 8×8 block (455) of quantized DCT coefficients for entropy encoding. The encoder scans (460) the 8×8 block (455) into a one dimensional array (465) with 64 elements, such that coefficients are generally ordered from lowest frequency to highest frequency, which typical creates long runs of zero values.
The encoder entropy encodes the scanned coefficients using a variation of run length coding (470). The encoder selects an entropy code from one or more run/level/last tables (475) and outputs the entropy code.
When the motion vector for a macroblock is zero (i.e., no motion) and no residual block information is transmitted for the macroblock, the encoder uses a 1-bit skip macroblock flag for the macroblock. For many kinds of video content (e.g., low motion and/or low bitrate video), this reduces bitrate by avoiding the transmission of motion vector and residual block information. The encoder puts the skip macroblock flag for a macroblock at the macroblock layer in the output bitstream, along with other information for the macroblock.
FIG. 5 shows the decoding process (500) for an inter-coded block. Due to the quantization of the DCT coefficients, the reconstructed block (575) is not identical to the corresponding original block. The compression is lossy.
In summary of FIG. 5, a decoder decodes (510, 520) entropy-coded information representing a prediction residual using variable length decoding and one or more run/level/last tables (515). The decoder inverse scans (530) a one-dimensional array (525) storing the entropy-decoded information into a two-dimensional block (535). The decoder inverse quantizes and inverse discrete cosine transforms (together, 540) the data, resulting in a reconstructed error block (545). In a separate path, the decoder computes a predicted block (565) using motion vector information (555) for displacement from a reference frame. The decoder combines (570) the predicted block (555) with the reconstructed error block (545) to form the reconstructed block (575).
When the decoder receives a skip macroblock flag for a macroblock, the decoder skips computing a prediction and decoding residual block information for the macroblock. Instead, the decoder uses corresponding pixel data from the location of the macroblock in the reference frame.
The amount of change between the original and reconstructed frame is termed the distortion and the number of bits required to code the frame is termed the rate. The amount of distortion is roughly inversely proportional to the rate. In other words, coding a frame with fewer bits (greater compression) will result in greater distortion and vice versa. One of the goals of a video compression scheme is to try to improve the rate-distortion—in other words to try to achieve the same distortion using fewer bits (or the same bits and lower distortion).
Although the use of skip macroblock flags in WMV7 typically reduces bitrate for many kinds of video content, it is less than optimal in some circumstances. In many cases, it fails to exploit redundancy in skip macroblock flags from macroblock to macroblock, for example, when skipped macroblocks occur in bunches in a picture. Also, WMV7 ignores motion prediction for macroblocks in predicted frames when the macroblocks are skipped, which hurts the efficiency of compression of predicted frames in some cases.
C. Standards for Video Compression and Decompression
Aside from WMV7, several international standards relate to video compression and decompression. These standards include the Motion Picture Experts Group ["MPEG"] 1, 2, and 4 standards and the H.261, H.262, and H.263 standards from the International Telecommunication Union ["ITU"]. Like WMV7, these standards use a combination of intraframe and interframe compression, although the standards typically differ from WMV7 in the details of the compression techniques used.
Some international standards recognize skipping coding of macroblocks as a tool to be used in video compression and decompression. For additional detail about skip macroblock coding in the standards, see the standards' specifications themselves.
The skipped macroblock coding in the above standards typically reduces bitrate for many kinds of video content, but is less than optimal in some circumstances. In many cases, it fails to exploit redundancy in skip macroblock flags from macroblock to macroblock, for example, when skipped macroblocks occur in bunches in a picture. Also, it ignores motion prediction for macroblocks in predicted macroblocks/pictures when the macroblocks are skipped, which hurts the efficiency of compression of predicted macroblocks/pictures in some cases.
Given the critical importance of video compression and decompression to digital video, it is not surprising that video compression and decompression are richly developed fields. Whatever the benefits of previous video compression and decompression techniques, however, they do not have the advantages of the following techniques and tools.

This patent is subject to a terminal disclaimer.


Flexographic printing plates are produced by exposing the photopolymer plates to a light source and washing out (developing) the masked out, non-exposed areas with a solvent. The invention provides methyl ester solvents suitable for use in the development of photopolymer printing plates. The solvents, which include methyl esters alone or mixed with co-solvents and/or non-solvents, are effective in developing a large number of different photopolymer printing plates and can produce images superior to those obtained with commercially available solvents currently used in such applications.

The present invention relates to an improved solvent and process for the production of flexographic printing plates crosslinked by photopolymerization. More specifically, the invention relates to a solvent system using methyl esters, alone or in combination with co-solvents and/or non-solvents, as washout solvents for the unpolymerized material in the printing plates to develop a relief image and a method for developing printing plates.
Washout processes for the development of photopolymerizable flexographic printing plates are well known and is described in detail in U.S. Pat. No. 5,240,815 which is incorporated herein by reference. Ordinarily, exposed plates are washed (developed) in a developing solvent that can remove the unpolymerized material while leaving the polymerized (cured) material intact. The solvent typically used in such processes include: (a) chlorohydrocarbons, such as trichloroethylene, perchloroethylene or trichloroethane, alone or in a mixture with a lower alcohol, such as n-butanol; (b) saturated cyclic or acyclic hydrocarbons, such as petroleum ether, hexane, heptane, octane, cyclohexane or methylcyclohexane; (c) aromatic hydrocarbons, such as benzene, toluene or xylene; (d) lower aliphatic ketones, such as acetone, methyl ethyl ketone or methyl isobutyl ketone; and (e) terpene hydrocarbons, such as d-limonene.
One important disadvantage of the known solvents and the procedures for their use is that the solvents being used as developers may act too slowly, cause swelling of the plates and/or cause damage to the fine detail in the plate by undercutting and/or pinholing. Moreover, when non-chlorinated solvents are used in the washout process, long drying times may be necessary. Furthermore, many of these solvents have flashpoints of less than 100xc2x0 F., so that the process can only be operated in special, explosion-protected plants. Many of the prior art solvents are considered Hazardous Air Pollutants (HAPS), and are subject to stringent reporting requirements. When chlorohydrocarbons and other toxic chemicals are used, their toxicity also gives rise to disposal problems and worker safety issues.
An essential step to any photopolymerizable relief printing process is the development of the printing plate after the image is formed through imagewise exposure of the photopolymerizable plate to light. The image is formed by polymerizing and crosslinking of the photopolimerizable material that is exposed while the unexposed portion remains unpolymerized. Ordinarily, development is accomplished by washing the exposed plate in a solvent which can remove the unpolymerized material while leaving the polymerized (cured) material intact. Since such plates can be formed from a variety of materials, it is necessary to match a specific plate with an appropriate solvent. For example, U.S. Pat. No. 4,323,636, U.S. Pat. No. 4,323,637, U.S. Pat. No. 4,423,135, and U.S. Pat. No. 4,369,246, the disclosures of which are incorporated herein by reference, disclose a variety of photopolymer printing plate compositions based on block copolymers of styrene and butadiene (SBS) or isoprene (SIS). These compositions can be utilized to produce printing plates which can be developed by a number of aliphatic and aromatic solvents, including methyl ethyl ketone, toluene, xylene, d-limonene, carbon tetrachloride, trichloroethane, methyl chloroform, and tetrachloroethylene. These solvents may be used alone or in a mixture with a xe2x80x9cnon-solventxe2x80x9d (i.e. a substance that cannot dissolve unpolymerized materials), for example, trichloroethane with ethanol. In any case, during the development step, the solvent can be applied in any convenient manner such as by pouring, immersing, spraying, or roller application. Brushing, which aids in the removal of the unpolymerized or uncrosslinked portions of the composition, can also be performed to facilitate the processing of the plate.
Similarly, UK 1,358,062 discloses photosensitive compositions consisting of a nitrile rubber with an addition of photopolymerizable tri- or tetra-unsaturated ester derived from acrylic or methacrylic acid combined with an addition polymerization initiator activated by actinic radiation. Plates made from this composition can be developed by organic solvents including aliphatic esters such as ethyl acetate, aliphatic ketones such as acetone, methyl ethyl ketone, d-limonene, halogenated organic solvents, such as chloroform, methylene chloride, CFC 113 or blends of such solvents. Brushing or agitation can be used to facilitate the removal of the non-polymerized portion of the composition.
U.S. Pat. No. 4,177,074 discloses a photosensitive composition containing a high molecular weight butadiene/acrylonitrile copolymer which contains carboxyl groups, a low molecular weight butadiene polymer which may or may not contain carboxyl groups, and an ethylenically unsaturated monomer, combined with a free-radical generating system. This composition is also used as the polymer layer of a flexographic printing plate and requires processing with such organic solvents as methyl ethyl ketone, benzene, toluene, xylene, d-limonene, trichloroethane, trichlorethylene, methyl chloroform, tetrachloroethylene, or solvent/non-solvent mixtures, e.g., tetrachloroethylene and n-butanol. The composition may also be processed with water-soluble organic solvents in an aqueous basic solution, such as sodium hydroxide/isopropyl alcohol/water; sodium carbonate/isopropyl alcohol/water; sodium carbonate/2-butoxyethanol/water; sodium borate/2-butoxyethanol/water; sodium silicate/2-butoxyethanol/water; sodium borate/2-butoxyethanol/water; sodium silicate/2-butoxyethanol/glycerol/water; and sodium carbonate/2-(2-butoxyethoxy)ethanol/water.
U.S. Pat. No. 4,517,279, the disclosure of which is incorporated herein by reference, discloses a photosensitive composition containing a high molecular weight butadiene acrylonitrile copolymer which contains carboxyl groups, and a high molecular weight butadiene/acrylonitrile copolymer which does not contain carboxyl groups, combined with ethylenically unsaturated monomer and a free radical generating system. That composition, which is also used as the polymer layer of a flexographic printing plate, requires processing by blends of tetrachloroethylene and a non-solvent. The composition may also be processed in mixtures of sodium hydroxide/isopropyl alcohol/water; sodium carbonate/2-butoxyethanol/water; sodium silicate/2-butoxyethanol/water; sodium carbonate/2-butoxyethanol/glycerol/water; and sodium hydroxide/2-(2-butoxyethoxy)ethanol/water.
As can be seen from the foregoing examples of the prior art, the solvents needed for image development will vary depending on the composition of the polymer layer of the plate. The need for different solvent systems is particularly inconvenient, especially if different photopolymer systems are being processed at the same facility. Furthermore, many of the solvents used to develop the plates are toxic or suspected carcinogens. Thus, there exists a real need for solvent systems which can be used with a greater degree of safety. In addition, there exists a need for solvent systems which can be used in a variety of plates. U.S. Pat. No. 4,806,452 and U.S. Pat. No. 4,847,182, the disclosures of which are incorporated herein by reference, disclose solvent developers for flexographic plates containing terpene hydrocarbons such as d-limonene which are effective on a variety of plate types. These terpene hydrocarbon-based developers are also non-toxic. However, they have proven to be hazards in the workplace because of their tendency to spontaneously combust thereby causing fires.
Therefore, commonly assigned U.S. Pat. No. 6,248,502 solves the drawbacks of terpene by using terpene esters as a substitute developing solvent. Because terpene ester has a higher flash point, the fire risk is greatly decreased. However, terpene esters tends to breakdown through repeated distillation which limits the recyclability of the solvent.
The present invention relates to an environmentally friendly developing solvent that offers improvement over the prior art. The solvent comprises methyl esters which have higher flash points when compared to current solvents. For example, d-limonene (a terpene), terpene ester, and methyl ester have a flash points of 120xc2x0 F., 141xc2x0 F., and  greater than 250xc2x0 F., respectively. By having a high flash point, methyl esters offers superior safety in addition to low toxicity, reduced cost, and biodegradability. Furthermore, compared developing solvents of the prior art including terpene ester, methyl ester causes less plate swelling. Therefore, more methyl esters (up to 70% by volume) can be used in the developing solvent resulting in faster removal rate of the non-polymerized portion of the plate.
The present invention comprises solvents for use in the processing of a wide variety of photopolymeric materials used to form photopolymer printing plates. These solvents, which comprise methyl esters either alone or in the presence of other organic materials (co-solvents and non-solvents), can be used with a variety of polymeric systems. The methyl esters are natural products with low toxicity and are relatively safe to use compared with other solvent systems. Methyl esters, it has been discovered, provide a unique combination of reduced cost, improved plate quality, low volatility, improved regulatory compliance, low toxicity, reduced washout time, and biodegradability.
It is, therefore, an object of the present invention to provide a solvent system and a process for the preparation of relief plates crosslinked by photopolymerization, in which the washout time and the drying time are substantially shorter compared with the conventional process solvents, and wherein the relief plates suffer neither excessive surface swelling nor under-washing and are characterized by improved relief depths and sidewall structure.
Another object of the present invention is to provide a process for the preparation of relief plates crosslinked by photopolymerization which is capable of operation without expensive explosion protection.
It is another object of the present invention to provide solvent systems for use with photopolymeric printing plates which overcome the spontaneous combustion problems of the prior art solvent systems.
It is another object of the present invention is to provide solvent systems which minimizes workplace hazards and requires minimal regulatory reporting.
The present invention comprises methyl ester solvents for use in photopolymer printing plate processing. The methyl esters, which can be used either alone or in a blended form with co-solvents or non-solvents, can be used to develop a number of different photopolymer printing plates. As used herein, co-solvents are non-methyl ester compounds that can also dissolve the non-polymerized material; and non-solvents are compounds that cannot dissolve the non-polymerized material. Methyl esters has the general formula RCOOCH3, where R can be any organic moiety. A wide variety of methyl esters are suitable for use in the solvents of this invention including, but not limited to, methyl esters of fatty acids with 8-18 carbons.
Mixtures of methyl esters can also be used and may show synergistic effects when compared with a methyl ester used alone. When a combination of two or more methyl esters is used, the resulting blend is often more effective as a solvent than the individual methyl esters. This blend is referred to herein as a MME (Methyl Mixed Ester) solvent.
Various co-solvents (non-methyl ester compounds that can also, by themselves, dissolve the non-polymerized material) and non-solvents (compounds that cannot, by themselves, dissolve the non-polymerized material) can also be employed with the methyl esters and MME according to the invention. Suitable co-solvents include, but is not limited to, n-butanol, 2-ethoxyethanol, benzyl alcohol, ethanol, methanol, propanol, isopropanol, alpha terpineol, dipropylene glycol methyl ether, 2-butoxyethanol, isopropyl alcohol, and 2-(2-butoxyethoxy) ethanol, cyclopentanol, cyclohexanol, cycloheptanol, substituted cyclopentanol, substituted cyclohexanol, substituted cycloheptanol, cyclopentyl substituted alcohol, cyclohexyl substituted alcohol, and cycloheptyl substituted alcohol.
The co-solvent should be soluble in the methyl ester or MME, should have suitable dissolving properties towards the non-photolysed (non-polymerized) portions of the plate that are to be dissolved, should have low toxicity and acceptable safety profiles, and should be readily disposable. The co-solvents are used to modify the properties of the solvent blend. This includes, for example, the addition of co-solvents to aid in the removal of the top protective cover skin on the flexographic plate. In addition, several of the co-solvents, such as terpene alcohols, in particular alpha terpineol, serve as stabilizers to prevent the separation of the solvent blend, which can occur at reduced temperatures. This stabilizer property of the co-solvent becomes important when isoparaffinic hydrocarbons are used as the non-solvent and benzyl alcohol is used as a co-solvent to remove the outer layer of the photopolymerizable printing plate since the benzyl alcohol may separate from the methyl esters and paraffinic hydrocarbon mixture. Further, the mixture of methyl esters and co-solvent is often more effective as a solvent than the individual methyl esters by itself.
The non-solvent should be miscible with the methyl ester or methyl esters and the co-solvents, should have acceptable toxicity and safety profiles, and should be readily disposable or recyclable. The non-solvent are typically used as a filler to reduce cost, therefore, recyclability of the non-solvent material is highly desirable. Suitable non-solvents include, but is not limited to, petroleum distillates, such as aliphatic petroleum distillates, naphthas, paraffinic solvents, hydrotreated petroleum distillates, mineral oil, mineral spirits, ligroin, decane, octane, hexane and other similar materials. Isoparaffinic solvents are commercially available in a wide range of volatility and corresponding flash points. The developing solvent of the invention can made with a wide range of commercially available isoparaffinic solvents as its non-solvent base. The following table shows volatilities and properties of commercially available isoparaffinic solvents suitable for use with the invention.
Parameters such as drying rates, fire risk, workplace air quality and volatile organic compound emissions will also play a role in the selected non-solvent choice.
In addition, in a commercially acceptable product, odor masking materials or perfumes are often added. Such odor masking materials or perfumes can include terpenes to impart a clean, fresh odor.
The developing solvent components can be varied but a suitable composition would be about 30-75% by volume of at least one methyl ester and preferably a mixture of methyl esters, about 20-60% by volume of a first co-solvent capable of dissolving the top protective cover layer of the flexographic plate, about 5-35% by volume of a second co-solvent. Optionally less than about 2% by volume of a perfume or odor masking material can be added to the solvent; however, it is important that the perfume must not adversely affect the function of the solvent. A non-solvent can also be included in the solvent in an amount up to about 45% by volume. A preferred composition would be about 50-70% by volume of at least one methyl ester and preferably a mixture of methyl esters, about 20-50% by volume of a first co-solvent capable of dissolving the top protective cover layer of the flexographic plate, about 10-30% by volume of a second co-solvent. A non-solvent can also be included in the preferred mixture in an amount up to about 20% by volume. The preferred co-solvents are 2-ethylhexanol and cyclohexanol; and the preferred non-solvent is an isoparaffinic hydrocarbon. An especially preferred developing solvent comprises 70% methyl hexadecanoate, 20% 2-ethylhexanol, and 10% cyclohexanol.
The methyl ester-based solvents may be substituted for the synthetic hydrocarbon, oxygenated solvents or halogenated hydrocarbon solvents used for processing photopolymer printing plates. For example, the methyl ester solvents are suitable in the processing of photopolymer printing plates based on block copolymers of styrene and butadiene (SBS) or styrene and isoprene (SIS), copolymers of butadiene and acrylonitrile, terpolymers of butadiene, acrylonitrile and acrylic acid and other similar photopolymers. The methyl ester-based solvents can be applied to the plates by any conventional application means including spraying, brushing, rolling, dipping (immersing) or any combination thereof. The methyl ester solvents also produce photopolymer plates with less cured polymer image swelling than those processed in conventional hydrocarbon or chlorinated hydrocarbon solvents. Since swelling tends to distort the image formed, this surprising result permits clear, sharp images to be formed at much lower exposure times than those resulting from the use of conventional solvents. Additionally, the solvents of the invention have fairly low volatility which reduces worker exposure during plate processing. Furthermore, because methyl esters are natural products, they are much less toxic and are more readily biodegradable than synthetic hydrocarbon or chlorinated hydrocarbon solvents.

Developing solvent for photopolymerizable printing plates


An improved networked computer communications system handles arbitrary streams of data, and transports at varying speeds those streams where intermediate updates can be dropped if they are obsoleted by later arriving data updates, optimizing the utilization of network and node resources. Complex buffering by system server software allows distributed, parallel, or redundant processing, transmission, and storage for performance, reliability, and robustness. Various parameters of the system can be monitored, and the system can be reconfigured automatically based on the observations. Varied techniques reduce the perceived end-to-end latency and take advantage of software and hardware capabilities that assets connected to the system may possess. One conferencing system allows conference participants to share all or a portion of the display seen on their computer screens. The conferees may be at sites removed from each other, or may view a recorded presentation or archived conference at different times. Conference participants are either “presenters” who can modify the display or “attendees” who cannot modify the display. A pointer icon, which can be labeled to identify the conferee, is displayed on the shared image area. Each conferee can modify the position of his or her own pointer, even when not presenting, so that every participant can see what each conferee is pointing to, should a conferee choose to point to an element of the display. These and other features apply to other data streams shared in the conference or in meetings where there is no shared-image data stream.

The present invention relates generally to the field of shared computer communications and computer conferencing. In particular, one embodiment of a conferencing system according to the present invention facilitates the conferencing of two or more persons, each with a computer at one or more locations with a shared visual display and additional communication capabilities such as video, shared drawing, audio, text chat, etc., and facilitates the recording and later playback of the communications.
Existing conferencing systems can be described as either video conferencing systems or "whiteboard" systems. In a video conferencing system, a snap-shot of the conference presentation is taken at regular intervals, such as thirty times per second. Given that the image on a computer display is not changing nearly that often, video conferencing wastes large amounts of bandwidth. In a whiteboard system, the presenter at the conference draws within a whiteboard application or imports the output of another program into the whiteboard program for manipulation. When the presenter is ready to present a snap-shot, the presenter presses a "send" button and the whiteboard program updates all the attendees' displays with the image created by the presenter. This type of system, while requiring less bandwidth than video conferencing, is clumsy to use, lacks real-time responses, and limits the presenter to the tools provided with the whiteboard program.
Existing shared-display or shared-image systems rely on interception and communication of display or graphics system commands or depend on conferees' having similar hardware and software platforms. These systems lack flexibility and performance if the network connections are unreliable or have narrow bandwidth, or they require uniform hardware or software installations.
Existing systems that provide single or multiple data stream handling of a nature different than shared-image conferencing depend on wide bandwidth network connections or on all participants having similar platforms.


The invention describes a surgical implant for providing stabilization of an intraosseous circumferential fracture within a femoral neck of a proximal femur. The surgical implant includes a bone barrel and a cortical side plate having at least one screw hole to allow rigid fixation of the implant to the proximal femur. The cortical side plate abuts a lateral cortex of the proximal femur having a lateral portal of entry to ensure the bone barrel remains substantially parallel to an inner bony surface of the lateral portal of entry at all times. The bone barrel ensures a collection of bone growth elements is retained intraosseously. An osteomedullary rod being coaxially aligned with the bone barrel includes an axial threading for securely engaging an internal mating thread of the bone barrel. The axial threading is adapted to allow clockwise axial rotation of the osteomedullary rod to position a compression head thereof in operational contact with an autogenous cancellous osteomedullary bone cylinder. Further axial clockwise rotation induces the collection of bone growth elements to be extravasated from the autogenous cancellous osteomedullary bone cylinder and to flow into a region of surrounding bone within the femoral head and the femoral neck so as to induce bidirectional new bone formation. Other embodiments of the invention are described herein.

1. Field of the Invention
Osteonecrosis of the femoral head in the young patient is a musculoskeletal disorder with growing concerns, particularly as osteolysis from particulate polyethylene wear debris compromises the longevity of a total hip arthroplasty. Approximately 20,000 new cases are reported each year, with an estimated 450,000 patients, on average, with ongoing disease in the United States. Lavernia et al. further reported in the Journal of the American Academy of Orthopaedic Surgeons in 1999 that osteonecrosis usually occurs during the prime of one""s working years.
Osteonecrosis of the femoral head can be separated into two clinical categories, the symptomatic hip and the asymptomatic hip. Almost uniformly, 85% of symptomatic hips progress to collapse, irrespective of the stage of disease at the time of the initial diagnosis. It is often the asymptomatic hip wherein controversy arises regarding treatment. Urbaniak found in his series of asymptomatic patients that at least ⅔ would progress to collapse. Importantly, one may define impending collapse of the femoral head as greater than 50% head involvement in two radiographic orthogonal views. Bradway and Morrey, in the J of Arthroplasty 1993, found that a collection of 15 xe2x80x9cpresymptomaticxe2x80x9d hips all collapsed. Consequently, proponents of core decompression recommend early diagnosis and treatment of disease, with the understanding that such a treatment regimen may not halt progression.
Many theories have been proposed to explain the pathogenesis of osteonecrosis of the femoral head, as the name itself seems to describe the end condition, dead or nonviable osteocytes surrounded by a matrix of mineralized bone. More importantly, at least five categories have been identified as a potential mechanisms underlining the basis for disease: (1) Direct Cellular Mechanisms, cells die as a result of chemotherapy of thermal injury; (2) Extraosseous Arterial Mechanisms, ischemic necrosis of the femoral head following a substantially displaced fracture of the femoral neck; (3) Extraosseous Venous Mechanisms, an observation supported by the work of Ficat and Arlet in which these investigators observed venous hypertension in all clinical stages of osteonecrosis. Interestingly, The Johns Hopkins University observed compensatory mechanisms in the venous outflow of the femoral head when the venous system was obstructed using a dog model, raising questions about the role of venous congestion in the pathogenesis of disease; (4) Intraosseous Extravascular Mechanisms, this finding is thought to be consistent with bone marrow edema often observed on magnetic resonance imaging; and (5) Intraosseous Intravascular Mechanisms, occlusion of small vessels in patients with sickle-cell disease and dysbaric exposure wherein emboli of fat or nitrogen bubbles are thought to lead to osteonecrosis of the femoral head.
At least four Stages of osteonecrosis are described to allow one to institute and compare various treatment regimens. The most frequently used staging system is that of Ficat and Arlet as follows: Stage I, normal plain film radiographs; Stage II, Sclerotic or cystic lesions without subchondral fracture; Stage III, Subchondral fracture (crescent sign), with or without articular incongruity; and Stage IV, osteoarthrosis with osteophytes. Other staging systems include those of Marcus et al., University of Pennsylvania System of Staging, Association Research Circulation Osseous (ARCO), and the Japanese Investigation Committee on Osteonecrosis wherein the location of the lesion determines the stage of disease.
At the histologic level, necrosis of the femoral head can be described as dead or nonviable osteocytes surrounded by a mineralized matrix of bone. In a retrospective study by Marcus and Enneking, 13 core biopsies had been performed to treat eleven patients with asymptomatic or silent hips in Stage I or Stage II disease. All core biopsies in their series demonstrated normal articular cartilage, necrotic subchondral bone, and creeping substitution (osteoclastic bone resorption followed by the infiltration of marrow mesenchymal cells within a fibrovascular stroma). These observations and those of Phemister, Bonfiglio and others suggest that the success of core decompression in the treatment of osteonecrosis of the femoral head, Stage I or II, partly depends on the ability of autologous bone graft to incorporate the necrotic segment of bone within the femoral head. However, these authors did not attempt to characterize the requirements for host bone incorporation beyond an adequate blood supply.
The diagnosis of osteonecrosis can be easily made on plain film radiographs, assuming the disease is at least Ficat and Arlet Stage II, combined with a thorough history with an emphasis on predisposing risk factors, principally alcohol and steroid use, and a complete physical examination. Magnetic resonance imaging (MRI) may add additional information but is not routinely necessary. The MRI, however, is particularly useful in the asymptomatic hip, Ficat and Arlet Stage I.
Treatment options for osteonecrosis of the femoral head are categorized into one of two major groups, non-operative and operative. Nonoperatively, limited clinical success has been observed in the treatment of the symptomatic hip. Mont and Hungerford reviewed the nonoperative experience in the medical literature and found that only 22% of 819 hips in several pooled studies had a satisfactory result. These authors refer to the location of the osteonecrotic lesion, medial versus lateral, and suggest that medial lesions are more likely to have a satisfactory outcome. This observation is consistent with a mechanical component having a dominant role in the progression of disease, irrespective of etiology. Operative treatment can be characterized as core decompression of the femoral head with or without bone grafting followed by at least six weeks of non-weightbearing. Brown et al. at the University of Iowa used a three-dimensional finite-element model to elucidate the stress distribution over the diseased femoral head so as to characterize the optimal placement of a decompressing core with respect to location, depth, and diameter. More importantly, Brown et al. further showed that the optimum mechanical benefit of appropriately placed cortical bone grafts in a decompressed femoral head is realized when such grafts are situated in direct mechanical contact with the subchondral plate. These authors used the gait cycle to identify peak stress in the femoral head during normal walking and concluded that when fibula grafts are appropriately placed they potentially afford relief of stress to vulnerable necrotic cancellous bone in the subchondral and superocentral regions of the femoral head, implying that osseous incorporation of the cortical bone graft may be ideal but not completely necessary in the prevention of collapse. Although Brown et al. outlined the importance of strategic placement of a cortical fibula graft, it is important to recognize that these authors assumed that the necrotic cancellous bone is at risk for an intra-substance fracture, in the absence of treatment and that such intra-substance structural failure is principally responsible for the progression of disease, i.e., collapse of the femoral head. One must consider that as a segment of the femoral head becomes increasingly necrotic, its modulus of elasticity may vary substantially from that of the surrounding cancellous bone, and that progression of disease is perhaps also failure of this surrounding bone at the necrotic host bone interface; the area of creeping substitution in the work of Bonfiglio et al. Although not a part of the investigative objective, Brown et al. additionally did not demonstrate how cyclic loading of a cortical bone graft beneath the subchondral plate influences the healing behavior of the surrounding necrotic bone at the host necrotic bone interface. More specifically, is bony union achieved at the necrotic host bone interface now that the necrotic bone is unloaded? Is the fibula strut really a load-bearing cortical graft to the extent that the surrounding necrotic bone no longer sustains a substantial cyclic load during gait? Does the fibula strut simply allow the joint reactive force to bypass the segment of necrotic bone thereby substantially reducing its micromotion? Does micromotion of the necrotic segment of bone cause pain? Does the pain spectrum associated with osteonecrosis suggest a nonunion at the necrotic host bone interface, an intraosseous nonunion? A clear distinction is made in that an intraosseous fracture does not extend into the cortex of the affected bone. These questions and others are prompted by the observation of good to excellent outcomes in patients with Ficat and Arlet Stage I or Stage II disease treated with core decompression with vascular and avascular cortical bone grafts, keeping aside the retrospective results of Kim et al. presented at the 1998 Annual Meeting comparing vascular to avascular fibula struts in treating osteonecrosis. More importantly, patients have been shown to benefit from core decompression alone implying that increased intraosseous pressure may play a dominant role in the early stages of disease, whereas in the later stages, the necrotic bone is less ductile and behaves in a more brittle fashion giving rise to subchondral collapse as evidence for a mechanical component playing a dominant role in the progression of disease. Recently, Mont et al. reported in the Journal of Bone and Joint Surgery good to excellent results in two groups of six dogs, twelve osteonecrotic hips, treated with trans-articular decompression of the femoral head and bone grafting, with and without osteogenic protein-1. Although the authors sought to elucidate the difference in healing time, i.e., the time to graft incorporation between the two groups, the critical observation is that all twelve hips were treated with avascular autograft. Therefore, Mont""s work in view of Brown et al. causes one to consider the role a vascularized fibula graft in the treatment of osteonecrosis of the femoral head. Does revascularization really occur?
The work of Brown et al. suggests that core decompression is substantially core debridement of the femoral head. However, as one attempts to adequately debride the femoral head of osteonecrotic bone, the diameter of the core, by necessity, becomes increasingly large because one is not able to mechanically debride bone from the femoral head at a right angle to the decompressing core. Further, strategic placement of a cortical bone graft beneath the subchondral plate simply provides means for bypassing the at risk necrotic bone and transfers the load during gait to the fibula strut, which is often secured at the lateral cortex of the femur with a single Kirschner wire. The addition of a xe2x80x9cblood supply,xe2x80x9d vascularized fibula graft, in part relies on the work of Bonfiglio et al. Interestingly, actually xe2x80x9cnecroticxe2x80x9d autogenous bone stimulates osteoclastic bone resorption. In a recent issue of the Journal of Bone and Joint Surgery, Enneking showed in a histopathologic study that massive preserved human allografts (avascular bone) are slowly incorporated into host bone through limited bridging external callus and internal repair, even when rigid fixation is used to stabilize these grafts. Enneking suggests that the limited incorporation of allograft at corticalxe2x80x94cortical junctions could be enhanced with more recently developed osteoinductive substances. Importantly, however, is that Enneking observed enhanced bridging callus formation at allograft host junctions that were augmented with autogenous bone, and not increased internal repair that characterizes graft incorporation. Therefore, one is inclined to conclude that the newer osteoinductive substances may simply enhance external bridging callus and not internal repair. More importantly, Enneking observed bone at the allograft host junctions that lacked remodeling along the lines of stress. The critical issues here is that resorption must be followed by the infiltration of mesenchymal cells within a fibrovascular stroma for true incorporation to be established. Viable autograft appears to retain its ability to stimulate ongoing osteoclastic resorption whereas allograft lacks this ability, as it is principally osteoconductive. A blood supply may be more important at corticalxe2x80x94cortical junctions. Cortical-cancellous junctions depend on the nature of the host cancellous bone. Cortical bone will not incorporate necrotic cancellous bone as cortical bone lacks sufficient metabolic activity. However, given that cancellous bone is 8 times as metabolically active as cortical bone, one can expect incorporation of viable cortical bone at a cortical-cancellous junction. Within the growth plate, necrotic calcified cartilage stimulates osteoclastic resorption followed by the laying down of osteoid by osteoblast. In primary bone healing, osteoclast bore into necrotic segments of bone, which are then followed by the laying down of osteoid by osteoblast. One might recognize that in these examples, necrotic and avascular autogenous bone stimulates the infiltration of osteoclast and mesenchymal cells, and that external bridging callus in the presence of internal repair represents union. Enneking""s work suggest that external bridging callus along human allograft bone is a surface event driven by local mesenchymal cells in the surrounding tissue while internal repair is limited as the cytokines germane to new bone formation within the allograft bone are lost during the sterilization process.
Einhorn et al. have shown that despite the great ingrowth of capillaries into fracture callus, the cell proliferation is such that the cells exist in a state of hypoxia. This hypoxic state could be favorable for bone formation, as in-vitro bone growth optimally occurs in a low-oxygen environment. Therefore, avascular autogenous bone in and of itself is not xe2x80x9cbadxe2x80x9d bone. Necrotic bone (a necrotic segment in the femoral head) retains its osteoinductivity and osteoconductivity. Osteoinduction is an avascular physiologic event dependent on BMP""s, whereas osteoconduction is an avascular physical event dependent on the structural integrity of the inorganic extracellular matrix of bone. Urist in the Journal of Science in 1965 showed that xe2x80x9cavascularxe2x80x9d demineralized bone implanted in extra-skeletal sites would induce bone formation. Enneking has shown recently in the Journal that new bone formation can occur with massive allografts (necrotic bone) but internal repair (a physiologic event) is limited. More specifically, Hedrocel, a proprietary metal, will support the infiltration of osteoblast, with the assumption that once infiltration is complete, new bone formation will ensue and ongoing remodeling (appositional new bone formation) will be sustained. Importantly, human allograft bone lacks osteoinduction sufficient to promote internal repair characteristic of bony union, as allograft bone is xe2x80x9cprocessedxe2x80x9d bone and consequentially may lose its ability to induce new bone formation. Necrotic or avascular autogenous bone retains its ability to induce and to conduct new bone formation, having a major requirement of stability and a healthy host bed. In this regard, as an osteoclastic front advances into the graft, avascular or necrotic, the mesenchymal cells that follow must continually receive the appropriate signals from cytokines (a physiologic event), and the graft must be sufficiently stable. Thus, one might consider the necrotic segment of the femoral head as a form of an unstable autograft and that the pathogenesis of osteonecrosis can be considered a mechanically unstable intra-osseous nonunion during the later stages of disease. An intra-osseous nonunion is to be distinctly differentiated from an extra-osseous nonunion wherein fibrous tissue characterizes the ununited bone. Clearly then, if stability of the necrotic segment of autogenous bone can be achieved, either through unloading of the necrotic bone or providing means for stabilization so as to facilitate internal repair where osteoinduction remains, union can be expected. The prevention of collapse and the absence of progression will characterize the extent and quality of union, i.e., internal repair.
To date, treatment modalities for osteonecrosis focus on attempts to deliver oxygenated blood to the necrotic bone within the femoral head. In a 1998 January/February article in the Journal of the American Academy of Orthopaedic Surgeons, Urbaniak describes a patent vascular pedicle along a fibula strut within a femoral head 5 days post-operatively. The patency of a typical vascularized fibula graft is usually assumed given the resolution of pain and the lack of progression of disease in a treated patient several years after the index surgery. The formal surgical procedure of decompression of the femoral head with vascularized fibula grafting usually requires prolonged surgery and is a demanding procedure. Vail and Urbaniak reported on donor site morbidity in 247 consecutive grafts in 198 patients at five years follow up. The authors observed an abnormality in 24% of limbs, a sensory deficit in 11.8%, and 2.7% had motor weakness. Other complications reported by Urbaniak and Harvey in 822 vascularized fibula grafts procedures include superficial wound infections in two patients, and thromboembolic events in three patients.
Recently, Zimmer began an IDE study using a proprietary material, Hedrocel (trabecular metal, tantalum) as a mechanical device to fill a surgically created void in a femoral neck of a decompressed femoral head. The trabecular metal has a compressive and an elastic modulus similar to cancellous bone. The current IDE study is designed to evaluate the safety and efficacy of trabecular metal in the treatment of patients with early stage disease. The frictional properties of trabecular metal interfaced against cancellous bone are outlined as means for securing the implant within host bone. More importantly, the current investigation is of a nature thought to promote revascularization of the femoral head. Trabecular metal is osteoconductive and promotes bony ingrowth. In this regard, bony ingrowth is unidirectional growth, i.e., growth from the surrounding bone into the trabecular metal implant. As an aside, Zimmer promotes an acetabular component in which trabecular metal overlies the outer surface of the component. Bony ingrowth is promoted along the surface of the implant as means for establishing its stable fixation. In this setting, unidirectional growth is ideal, i.e., bony ingrowth into the implant. However, trabecular metal or any synthetic component juxtaposed necrotic bone will not promote new bone formation in a direction away from the implanted device and toward the necrotic bone. Further, such a large porous material will create a physiologic demand on bone formation in a direction away from the necrotic bone toward and into the implanted device, when in fact the purpose of treatment, particularly vascularized fibula grafts, is to direct bony ingrowth into the necrotic bone, i.e., bone growth in a direction away from the fibula strut and into the necrotic bone. More specifically, an acetabular component with trabecular metal on its outer surface has clinical value, whereas a mechanically stable column of trabecular metal within the femoral neck of a patient with osteonecrosis has less than obvious clinical value, as the bony ingrowth in this setting is in a direction away from the necrotic bone, thereby almost ensuring that the necrotic bone will not undergo sufficient internal repair as characterized by Enneking. One might surmise that complete debridement of the femoral head of necrotic bone and subsequent stabilization with trabecular metal may very well serve the clinical objectives of operative treatment. However, it is more prudent to stabilize the femoral head with autogenous cancellous bone. More succinctly, why discard a column of cancellous bone antecedent to the segment of necrotic bone within the femoral head? The antecedent cancellous bone is viable and is useful clinically. Successful incorporation of a necrotic segment of bone requires bi-directional bony ingrowth. Bi-directional bony ingrowth is only available with viable cancellous autograft.
With the understanding as outlined, one might be principally inclined to (1) adequately debride a femoral head of necrotic bone, (2) replace the necrotic bone with viable cancellous bone, and (3) provide means for structural support to a region of overlying cartilage. It is the purpose of the invention described herein to achieve these objectives using a novel device and a minimally invasive surgical technique, without the use of a fibula strut.
2. Information Disclosure Statement
Bone grafting is among one of the most frequently performed surgical procedures by surgeons challenged with reconstructing or replacing skeletal defects. Over the years, several techniques have been devised to obtain and implant autologous bone. Scientist and clinicians have sought and defined the essential elements of bone healing and have further desired to secure these elements when considering the benefits of various types of bone grafting techniques. Recently, scientific inquiry has been directed toward understanding the role of bone morphogenic protein (BMP) in the process of new bone formation. What we have learned is that a simple fracture incites a tremendous cascade of events that lead to new bone formation, and that reducing this cascade to a product that can be sold is a difficult task if not impossible. Nonetheless, complex fractures continue to occur which orthopaedic surgeons manage daily. Therefore, if one is to appreciate the invention at hand the essentials of fracture healing and new bone formation must be understood.
The essential elements required for bone regeneration are osteoconduction, osteoinduction, and osteogenic cells. In this regard, autogenous bone is the gold standard for bone harvesting. Cancellous bone, as does cortical bone, contains all of these elements but lacks structural integrity. Cortical bone has structural integrity but is limited in quantity. At the histologic level, cortical bone is 4 times as dense as cancellous bone, and cancellous bone is 8 times as metabolically active as cortical bone. Further, clinicians have recognized the consequences of donor site morbidity and prolonged hospitalization after a traditional harvesting technique. To circumvent some of these issues, numerous synthetic bone like products have been made available for general use. Each product attempts to exploit one or more of the three essential elements of bone regeneration described above. Although many of these products, e.g., Pro Osteon, INTERPORE, Collagraft, ZIMMER and others are unique, they remain expensive.
To define a less invasive technique for bone harvesting, percutaneous methods have been described. The recently developed techniques simply involve using a coring cylindrical device to obtain a segment of bone. David Bilimire, M. D. describes this technique in his article, Use of the CORB Needle Biopsy for the Harvesting of Iliac Crest Bone Graft, PLASTIC AND RECONSTRUCTIVE SURGERY, February 1994. Billmire makes no effort to ensure the quality of the harvested bone but rather describes a power-driven counter-rotating hollow needle as cutting through bone and soft tissue. Michael Saleh describes a percutaneous technique for bone harvesting in his article, Bone Graft Harvesting: A percutaneous Technique, Journal of Bone and Joint Surgery [Br] 1991; 73-B: 867-8. The author describes using a trephine to twist and lever out a core of bone of 8 mm in size. INNOVASIVE DEVICES describes using their COR(trademark). System for arthroscopic bone graft harvesting. This system describes a disposable cutter having a distal cutting tooth projected into the lumen of the Harvester. This cutting tooth ensures that all harvested osteochondral bone grafts will have a uniform dimension. This cutting tool also serves as means for removing the harvested bone from its donor site. Further, the plunger of the COR(trademark) System is used to disengage gently the harvested bone so as to maintain the overall length of the graft. This concept is absolutely essential to the successful use of the COR(trademark) System as these precisely obtained samples of osteochondral bone are implanted into pre-drilled osteochondral defects within the knee. Further, a vacuum of any sort could not be used on the COR(trademark) System, as the vacuum would simply continue to extract water from the knee joint thereby failing to create an effective pressure drop across the harvested bone and loss of operative visualization. Brannon, in U.S. Pat. No. 6,007,496 describes the use of a vacuum apparatus to create a pressure drop across an osteopiston of bone. Scarborough et al., in U.S. Pat. No. 5,632,747 described a device for cutting short segment dowels from a bone mass.
When considering bone for grafting purposes, the recipient site must be considered as well. Failure to achieve bony union at a fracture site or bony fusion at a fusion site may be caused by several factors. Often, the blood flow is inadequate at the fracture site because of local trauma during the inciting event, as might be the case in osteonecrosis of the femoral head. Further, when considering augmentation of the healing process with bone graft, it is imperative that the grafted bone contains all of the essential elements germane to successful osseous regeneration, namely, osteoconductive elements, osteoinductive elements, and osteoprogenitor cells. Most current devices used for bone grafting focus on quantity, the osteoconductive portion of the harvested bone, and less so on quality, the osteoinductive portion of the harvested bone. Recently, bone substitutes have been developed and can be classified according to the following major categories: 1) Osteoconductive synthetics (Pro Osteon 500), 2) Osteoinductive allograft (Grafton), 3) Osteoinductive biosynthetics (OP-1), 4) Osteoinductive autologous bone marrow aspirates, 5) Osteoconductive/Osteoinductive combination synthetics, and 6) Gene therapy. When implanting the above bone graft substitutes, recognizing the usefulness of a collection of bone growth elements at the fracture site or those generated during the process of open reduction and internal fixation (ORIF) or any other bony procedure, such as posterior spinal instrumentation, has not been achieved through the development of a simple device to promote in situ bone grafting. In this regard, synthetic alternatives to bone grafting can be used as expanders that can be added to autogenous bone and mesenchymal cells harvested in situ at the fracture site or the surgical site. This approach will indeed ensure that all patients are given an optimal opportunity for bony union or bony fusion.
To recognize the issues at hand governing the invention described herein, a simple discussion of biomechanics, physiology, and general physics is warranted and presented in support hereof.
Bone is a viscoelastic material, and as such, it behaves predictably along its stress strain curve when axially loaded in either tension or compression. The key word here is viscoelastic. The prefix xe2x80x9cviscoxe2x80x9d describes the fluid component of the material being tested and the suffix xe2x80x9celasticxe2x80x9d describes the recoil potential of the material being tested. The ratio of stress:strain is Young""s Modulus. Clearly, a spring is fully elastic. One may place a tension force on a spring, but when the tension is released, the spring recoils to its original length. A syringe, on the other hand, with a thin hypodermic needle attached, is considered viscoelastic. In other words, the amount of deformation observed is time dependent. Simply, the deformation will remain after the tension is removed. Consider one throwing Silly Putty against the ground and observing it bounce versus letting the material sit on a counter for several hours. One should appreciate that minimal deformation occurs when the Silly Putty bounces from the floor versus sitting it on a counter for several hours. The deformation is time dependent because of the internal fluid properties of the material; an amount of time is required to observe a net fluid flow. Bone behaves in a similar fashion, but has the additional property of being able to respond to a given stress by forming new bone. When bone fails to respond favorably, it fractures.
The physiologic properties of bone hinge on the fluid elements that govern bone regeneration, namely, bone morphogenic protein, various hormones, and osteoprogenitor cells. These fluid elements are important to the physiologic function of bone and are found within the bone marrow and the circulatory system. Appreciate that there is a net flow of these elements as bone bares a daily physiologic load during normal walking. Since the circulatory system is a closed system, a net loss of these fluid elements is not observed but rather continuous remodeling of bone and metabolic maintenance of the various cells and proteins as they age and become nonfunctional.
Bone is incompressible above or below its elastic limit, i.e., Young""s Modulus. Poisson""s ratio is used to describe this behavior and is defined as follows:
v=xe2x88x92(delta d/d0)/(delta I/I0)xe2x80x83xe2x80x83(1).
Poisson""s ratio can be thought of as a measure of how much a material thins when it is stretched, consider taffy, or how much a material bulges when it is compressed. Regarding bone, one does not necessarily observe an increase in volume when it is compressed, but rather an increase in the density as bone remodels along the lines of stress, i.e., form follows function, Wolff""s Law. More succinctly, bone is stimulated to produce new when it undergoes a load in tension, compression, or torsion. The essential issue in fracture healing is to exploit these principles to the benefit of the patient, i.e., early weightbearing.
When bone is compressed beyond its elastic limit, it fractures, i.e., it expands, therefore, its area will increase in a direction perpendicular to the line of force. The fracture observed occurs in the osteoconductive portion of bone, and a fluid flow will occur, as a result of the fracture, within the osteoinductive portion of bone.
The physiology of bone form and function is clear, but what a physician may observe through a series of x-rays may vary from patient to patient. Clearly then what we look for on a x-ray is evidence of healing, and in this regard, fracture healing is divided into at least four categories as follows: 1) inflammatory stage, 2) soft callus stage, 3) hard callus stage, and 4) remodeling stage. Each of these stages has clinical parameters that can be evaluated at the bedside. It is important to note, however, that any healing process in the human begins with clot formation; consider a simple laceration. Thus, fracture healing begins with clot formation. However, this stage of fracture healing does not have a clinical parameter unless the fracture is considered an open fracture and the absence of bleeding is observed.
The continuos fluid nature of whole blood (formed elements, i.e., blood cells; serine proteases, i.e., clotting factors; proteins, carbohydrates, electrolytes and hormones) while circulating in the vascular system is substantially maintained by the endothelial lining along the vessel walls. When these circulating serine proteases are exposed to subendothelial collagen or surfaces other than endothelial cells, i.e., abnormal surfaces, platelets aggregate and the clotting cascade is initiated. Blood without formed elements is considered plasma, while plasma without clotting factors is considered serum. A collection of autogenous bone growth elements is considered any and all factors germane to bone formation.
The clotting cascade is divided into two arms; the intrinsic pathway, i.e., local tissue trauma incites clot formation through exposure of the subendothelial collagen to circulating serine proteases and platelets; and the extrinsic pathway which incites clot formation through the activation of Factor VII serine protease and by tissue thromboplastin released from damaged cells. Both pathways then converge on Factor X serine protease. Regarding platelets, these cells are first to arrive and become adherent to injured tissue and form a platelet plug. Adherent platelets are activated platelets and as such release hemostatic agonist and autologous growth factors through a process of degranulation. The hemostatic agonists promote clot formation to ensure that the bleeding stops, while the autologous growth factors initiate the healing process of the injured tissue. Unique to bone is that its healing process is more regenerative of new bone formation as opposed to reparative which is more indicative of scar formation. Scar formation in fracture healing is a nonunion. Further, when bone fractures as a result of surgical or unintentional trauma, a collection of bone growth elements are generated directly within the fracture that contain both fluid and non-fluid components. Within the fluid component are platelets, blood and bone marrow mesenchymal cells, collagen and noncollagenous proteins, and small spicules of bone. The solid component is considered the bony fragments. ORIF is specifically designed to restore length and alignment of the fractured bone through rigid fixation of the non-fluid component. Bone grafting is used when it is determined preoperatively that the structural integrity and the quantity of the bony fragments are insufficient to allow ORIF. Clearly, the collection of bone growth elements required for bony union are present at the fracture site at the time of surgical (core decompression) or unintentional trauma. It stands to reason that in situ autologous bone growth elements, fluid and non-fluid, should be retained and used in conjunction with means for stabilizing the intra-osseous nonunion within the osteonecrotic femoral head. In situ autologous bone growth factors at a given fracture site unequivocally include the appropriate level of BMP""s and other noncollagenous proteins at the various stages of fracture healing as described above. Understanding the physiology of new bone formation, a reparative process, will lend credence to how one should collect and use bone graft elements harvested in situ or from a second operative site.
The above description is one of the basic sciences of new bone formation as it relates to osteonecrosis of the femoral head. In this regard, prior art does not reveal a unique process for in situ bone grafting in the treatment of osteonecrosis of the femoral head. More specifically, prior art does not describe an intraosseous circumferential fracture as means for providing the bone growth elements, nor a device for enhancing the local delivery of the bone growth elements so as to promote bidirectional new bone formation. The invention described herein uniquely exploits the above basic science principles of new bone formation so as to ensure the optimum chance for internal repair of a segment of osteonecrotic bone.
It is an object of the present invention to provide means to substantially compress an osteomedullary bone cylinder within a femoral neck so as to cause a collection of bone growth elements to be extravasated therefrom the osteomedullary bone cylinder and subsequently flow into a region of surrounding cancellous bone.
It is yet a further object of the present invention to provide means to cause an osteomedullary bone cylinder to be retained within a femoral neck so as to allow the osteomedullary bone cylinder to provide structural support to a region of overlying cartilage within the femoral head.
It is yet a further object of the present invention to promote bidirectional new bone formation within the femoral head and the femoral neck so as to promote substantial internal repair in a segment of osteonecrotic bone.
It is yet a further object of the present invention to provide means to stabilize an intraosseous circumferential fracture within the femoral neck so as to allow weightbearing on the affected extremity immediately after core decompression of a femoral head.
It is yet a further object of the present invention to stabilize an intraosseous circumferential fracture within the femoral neck using a minimally invasive technique.
It is yet a further object of the present invention to promote all musculoskeletal surgeons to use autogenous bone in situ when bone grafting is required for new bone formation.
Using an osteomedullary cylinder, an osteocentral canal is created in the femoral neck to allow surgical dxc3x3bridement or decompression of a segment of osteonecrotic bone within the femoral head. The surgical debridement can be completed with an osteoendoscopic cylinder and an endoscope thereby by accomplishing such debridement under direct visualization. Thereafter surgical dxc3xa9bridement, the osteomedullary cylinder, containing an autogenous cancellous osteomedullary bone cylinder, is inserted into the osteocentral canal. The autogenous cancellous osteomedullary bone cylinder is mechanically advanced distally out of the osteomedullary cylinder to a second position inferior to the region of overlying cartilage of the femoral head so as to provide mechanical support thereto. The osteomedullary cylinder is advanced proximally and removed from the femoral neck and thereby establishes a friction bony interface or an intraosseous circumferential fracture therebetween the autogenous cancellous osteomedullary bone cylinder and the region of surrounding cancellous bone of the femoral neck. A displacement plunger is used to advance further the autogenous cancellous osteomedullary bone cylinder into the femoral head and neck. The displacement plunger may also be used as a depth gauge. The friction bony interface allows substantial proximal advancement; subsequent expansion and incarceration of the autogenous cancellous osteomedullary bone cylinder therewithin the osteocentral canal of the femoral neck. Using an osteomedullary rod, biaxial compression of the autogenous cancellous osteomedullary bone cylinder induces a collection of bone growth elements to be extravasated therefrom and further flow into the region of surrounding cancellous bone to promote bidirectional new bone formation. The present invention describes a novel and unobvious method to compress the autogenous cancellous osteomedullary bone cylinder and thereby enhance the local delivery of bone growth elements and further provide support to a region of overlying cartilage. The osteomedullary rod is threadable into a cylindrical barrel having a side plate integral therewith. The side plate is fixed to the shaft of the femur using a plurality of screws. The osteomedullary rod is cannulated so as to facilitate congruent coaxial insertion thereof into the osteocentral canal. The autogenous cancellous osteomedullary bone cylinder within the osteocentral canal of the femoral neck is axially aligned with the osteomedulary rod so as to allow substantial biaxial compression thereof and thereby bone graft in situ. The above procedure, biaxial core compression, is accomplished using a minimally invasive surgical technique and will allow the patient to begin weightbearing immediately after surgery.


A large round baler is equipped with a chassis, including an outer pair of fixed side walls, that extend rearwardly beyond a pair of inner side walls which form opposite sides of a baling chamber. In an upper region of the baler, belts or the like are supported by a plurality of fixed rotary bodies extending either between the inner or the outer side walls and a movable rotary body carried at the end of a pivotally mounted tension arm, to form a large take-up loop that becomes smaller as a run of the belts expands during growth of the bale being formed. The run of belts, which is looped about the bale being formed, is conducted over rollers carried by a vertically pivoted frame, such that when the frame is swung between a lower extreme position, which it occupies during formation of a bale to a raised position, the formed bale is deposited on the ground.

The invention concerns a large round baler with at least one flexible, endless bale-forming arrangement that is conducted over rotary bodies with stationary axes and rotary bodies with movable axes and that generally surrounds the circumference of a baling chamber.
The book, FMO-141B, Edition D-00, shows on page 153 a large round baler with fixed side walls between which rotating rollers on stationary axes and on rotating rollers on swingable axes are arranged over which belts can be conducted. Some of the rollers are engaged in a carrier that can be pivoted vertically. The belts also extend over rollers on a tensioning arm which is forced continuously by the force of a spring into a position in which tension is applied to the belts. The advantage of this configuration lies in the fact that the carrier with the few rollers is light and does not require large positioning forces. The disadvantage, however, is that the carrier must be raised by a considerable distance so that the completed cylindrical bale can be ejected, particularly since a second set of belts is provided in the region of the ground, on which the cylindrical bale rests during its formation. When the cylindrical bale is ejected, the tension in the belts is reduced so that the ejection movement of the cylindrical bale cannot be supported.
The prospectus, VERMEER 504 HE, no publication date, shows a large round baler, in which the pivot point of a carrier extending outside the baling chamber, is located almost in the region of the center of the baling chamber. At the outer end region of the carrier, an arm is provided on which several rollers are located, over which belts are conducted and that can penetrate into the baling chamber. In this case, the tensioning arrangement forms several loops in which harvested crop can collect.
DE-A1-198 51 470 discloses a large round baler with only a single set of belts that are conducted over rollers on stationary axes and rollers on axes that can be moved in their positions in a fixed housing and in a housing component that can be pivoted. A tensioning arm is also provided that conducts the belts over two adjustable rollers. The disadvantage of this configuration consists of its limited arrangement, that results from the use of two tensioning rollers and that leads to several loops in the bale-forming arrangement during the baling operation, in which crop to be baled can accumulate and lead to jams.
The problem underlying the invention is seen in the need to propose a compact large round baler with a tensioning mechanism that maintains tension on the bale-forming arrangement and avoids jams.
This problem is solved according to the invention by the teaching of patent claim 1, where the further patent claims cite characteristics that further develop the solution to great advantage.
The arrangement of two adjacent rotary bodies on the carrier, between which the bale-forming arrangement extends, has the advantage that the bale-forming arrangement is in contact at one time with the one rotary body and at another time with the other rotary body depending on the position of the carrier. In this way, a further loop can be formed by means of the carrier that shortens the bale-forming arrangement and thereby maintains the tension. However, this loop is formed only during the raising of the carrier and does not give occasion for an accumulation of stray crop during the baling operation. The bale-forming arrangement may be configured as a set of narrow, parallel belts, as a band or as a bar chain conveyor. The rotary bodies are regularly rollers or rolls, and they may also be configured as sprockets, particularly in the case of a bar chain conveyor. The configuration of the carrier is conceivable in many ways, for example, as a component with several planes, as a lattice work of tubes, as a correspondingly curved arm or the like.
This carrier may also be configured relatively massively, since it extends and moves outside of the side walls of the baling chamber. Since only the carrier, its rollers, and the corresponding sections of the belts are moved in order to eject the bale, but not the side walls, the positioning forces are low. The positioning paths are also short, if the carrier with its rollers and the sections of the bale-forming arrangement running over them, form the bottom of the baling chamber and the bale can fall to the ground after only a small stroke of the carrier.
A support of the carrier in bearings at least in the central region of the baling chamber, in contrast to a bearing support provided above it, has the result that the baling chamber can be opened quickly for the ejection of the bale, so that the baling operation can again be resumed very rapidly. When the carrier is raised, it can hardly touch the ejected bale, because due to its central position, its radial extent is considerably less than in the state of the art.
The positioning path of the carrier is not compromised by rotary bodies on stationary axes that are located in the end regions of the baling chamber, if these rotary bodies on stationary axes are located in a region into which the carrier with its rotary bodies intrudes only to a limited extent and if the rotary bodies provide space into which the carrier can intrude. With three rotary bodies above the baling chamber, the bale-forming arrangement can form a sufficient number of loops in order to be tensioned adequately.
The tension in the bale-forming arrangement is generated in a simple way by an arm that carries a rotary body, about which the bale-forming arrangement is conducted in a loop. The force to reposition or to retain the arm can be generated by a spring, a hydraulic or pneumatic motor or the like. If the arm and the rotary body supported in bearings on it is located above the baling chamber, it does not increase the length of the large round baler, but at most its height, which is not significant.
The one rotary body on the carrier, on the one hand, can be associated with a further rotary body offset from the first, and on the other hand, will prevent the spans of the bale-forming arrangement from touching each other. As an alternative, a rotary body of larger diameter could also be used.
A triangular configuration of the carrier provides a stable arrangement that also saves space. The configuration of the one corner region as a bearing assures a secure transmission of the forces.
If the carrier simultaneously forms the side wall of the baling chamber, this can result in a reduction of the number of parts. Instead of using tubes, struts or the like, the stiffness can be improved with ribs, flanges, folded edges or the like. The position of the rotary bodies to the side wall or the side walls does not change. If the rotary bodies with the carrier and thereby with the side walls are raised for the ejection of the cylindrical bale, any crop accumulated outside of the baling chamber is ejected from the large round baler.
If a further carrier is provided that can be pivoted, whose position is a function of the tension in the bale-forming arrangement and the force of the bale, these rotary bodies can adjust themselves in such a way that the bale is supported by several rotary bodies and thereby the surface pressure remains low. A low surface pressure results in a low resistance to movement and thereby to a low power requirement.
During the baling operation and the unloading operation, if the two rotary bodies of the carrier that perform a deflection of the bale-forming arrangement are located at the same distance or essentially the same distance from a rotary body with a stationary axis, then at one time a maximum shortening of the bale-forming arrangement can be performed and at another time, a corresponding maximum lengthening of the bale-forming arrangement can be performed.
If the side walls can be repositioned relative to the chassis of the large round baler, they can be moved apart from each other for the ejection of the cylindrical bale, so that the friction forces on them can be eliminated and the bale can easily be ejected from the baling chamber.
Rotary bodies that extend outside the baling chamber, that is, extend to the side beyond it, or are at least even with the sides, and can move, if necessary, along the end edges of the side walls, are able to accommodate a movement of the side walls.

Round baler having simplified bale discharge structure