1：Ground Stone Redux：2019/11/12(火) 04:47:54 ID:.CwsIRrI0
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2：Ground Stone Redux：2019/11/12(火) 05:02:19 ID:.CwsIRrI0
From 「Notes on artificial medical devices」,
5.2 Medical high-polymeric materials
5.2.5 New high-polymeric materials used for artificial joints and re-generative medicine
The higher the levels of technologies for medicine and welfare get, the more un-stable the medical and welfare system at present under which most payments rely on the nation’s health system becomes.
Accordingly, it’s necessary to utilize medical technologies including artificial joints at high performance under stable economic & social ground.
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This does not necessarily mean to supply cheap artificial joints.
Special attentions are being poured into technologies to heal articular diseases of many medical technologies.
One of the main reasons is that it’s likely that this technology contributes to not only prognoses of people’s life but also the maintenance of autonomy or independency, a lifespan at healthy condition and improvements in economic & social activity.
4：Ground Stone Redux：2019/11/12(火) 05:29:39 ID:.CwsIRrI0
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The replacement with an artificial joint has following three main tasks.
① bearability
② movability
③ painless
Namely, movability with bearing one’s weight and movability with no pains are requested.
These are necessary points to enable a human being to independently make the daily life.
Concrete characters requested to future type artificial joints are summarized into following two points.
( 1 ) articular functions sustained for a long term
( 2 ) improvements in articular function
5：Ground Stone Redux：2019/11/12(火) 05:41:10 ID:.CwsIRrI0
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The former task is to reduce stresses originated in replacement and prolong a lifespan at healthy condition namely to develop an artificial joint usable without being exchanged for a long period.
Meanwhile, the latter task is to recover individual life activities such as work, sport and hobby.
Improvements in economic & social activity for patients are necessary to assure of the usefulness of the artificial joint as a new technology.
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6：Ground Stone Redux：2019/11/12(火) 05:55:40 ID:.CwsIRrI0
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In this section, we mention main points of maintenance of joints for a long period and its improvements in performance, limits of artificially ‘produced’ joints and new aspects of ‘grown’ joints with regenerative technologies.
Furthermore, we briefly introduce ways to prepare communication-environments ( communications about risks, risky communications ) required to find out new ways for healing damaged joints into this section too.
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5.2.5-1 Maintenance of articular function for a long period ( structural healthiness in wide meaning )
The replacement of artificial joint is clinically generalized as an articular constructive method taking movability into consideration.
But, the ‘structural healthiness’ of the artificial joint as an industrial product has never been established yet ( about 2013 ).
‘Structural healthiness’ as a term means a generic durability including fatigue resistance, abrasion resistance.
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It’s hard to find out a machine which continues to work without maintenances for a long period of about 20 years except for artificial joints in various industrial products.
Furthermore, in case of artificial joints, it’s needed to estimate ‘structural healthiness’ in wide meaning with bearing biological interactions on the interface between a living tissue and a material in mind.
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Ultra High Molecular Weight Polyethylenes ( UHMWPE ) which were applied to clinical fields by Charnley are being generally utilized as rubbing materials for artificial joints for now.
It’s rare that rubbing functions are lost due to abrasions.
But, as polyethylene abrasion granules at submicron in size cause osteo-lyses, further, loosenings between the artificial joint and osseous tissues,
it’s important to reduce the quantity of abrasion and suppress osteo-lyses for prolonging the lifespan of artificial joint.
10：Ground Stone Redux：2019/11/13(水) 06:22:35 ID:r5.ITLX.0
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An idea of cross-linked polyethylene proposed by Oonishi and others was mainly applied to artificial hip joints, it considerably contributed to improvement in abrasion resistance.
Furthermore, a way to graft 2-methacryloyloxyethyl phosphoryl-choline ( MPC ) onto the polyethylene-surface of the rubbing part of an artificial hip joint at nano-scale ( MPC-processing ) was devised by a collaboration of the orthopaedic class of the medical department and the faculty of engineering of Tokyo-university, this way also remarkably improved abrasion resistance.
And, Tomita and others in Kyoto-university showed that mixing dl-α-tocopheral as a kind of vitamin E with polyethylene before molding can prevent oxidative fatigue fractures of polyethylene for artificial joints.
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By the way, the most important factor to determine the lifespan of an artificial joint is bone-absorption.
This bone-absorption is caused by reactions of polyethylene abrasion granules in a living tissue.
Both technologies shown in the above can suppress reactions of abrasion granules with living tissues.
As the above, new material technologies have possibility to prolong the lifespan of an artificial joint including an artificial hip joint and an artificial knee joint.
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But, in experiments of the former MPC-technology, activations of actually generated abrasion granules in a living body have never been made clear yet.
And, even in experiments of the latter polyethylene containing vitamin E , activations of abrasion-granules under the same complete aseptic condition as an inner-living body have never been made clear yet ( in 2013 ).
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A device to realize an aseptic frictional state in vivo is shown in Fig 24 .
It’s possible to freely prepare an optional rubbing state matching with the artificial hip joint and that matching with the artificial knee joint with this device.
Systems to measure its bio-activations at the contact of abrasion granules generated by such a device with living cells are being developed.
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The primary problem to develop artificial joints until now is that there have never been ways to directly the extent of osteo-lysis as the main factor to determine its lifespan and its performance.
Therefore, general industrial ways for examination have been applied to estimating materials for artificial joints without taking the differences between a living body and a matter into consideration.
But, as a device to generate abrasion granules at aseptic state and various rubbing conditions was developed, it has enabled to investigate bio-activations of abrasion granules at higher accuracy.
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5.2.5-2 Further improvement in articular function ( artificial joints matching for life-demands and re-generative joints )
As stated previously, it’s important to reconstruct articular functions matching for individual life demands such as works, sports and hobbies for developing future type artificial joints.
For instance, it’s often reported that a famous pro-golfer continues playing a golf after receiving a replacement operation with an artificial joint.
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Furthermore, recently, it’s requested to design artificial medical materials matching individual conditions and hobbies.
Especially, it’s getting possible to produce artificial joints so as to match them with individual shapes of bone and life-styles owing to the appearance of customized artificial joint.
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However, if we continuously make a more active motion with a mechanical matter such as artificial joints, its durability of the mechanical tool also will be lowered.
And, even though we provisionally succeed in the prevention of osteolysis, as its functions are sustained under the constant exchange of components, it’s unlikely that an artificial matter semi-permanently plays stable functions.
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For example, athletes basically have same joints as those of general people in structure.
But, joints of athletes are endurable to tens times more extreme motions than usual motions.
Those mechanisms have never been made clear yet ( about 2013 ).
However, joints of living being seem to have functions to keep the low frictional state with adjusting themselves against extreme conditions.
Technologies to re-generate such living tissues, further, systems to heal damaged joints including re-generative processes are being realized.
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19：Ground Stone Redux：2019/11/14(木) 05:49:09 ID:aBjyCzo60
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But, as regenerative treatments for cartilage at present are applied to only cases with widely damaged articular cartilages of deforming osteo-arthritis and chronic rheumatoid arthritis,
we must develop treatment-systems taking bearability, movability and painless into consideration from now.
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For instance, as the appearance of deforming osteoarthritis includes the bad circle of deformation → failure in dynamical balance → failure in lubricant function → damaged tissue → deformation as a main factor, even if the cartilage is regenerated, the same symptom appears again.
Accordingly, we must combine the correction of this deformation with the regeneration of cartilage and the reconstruction of mechanism to support a weight.
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As the effectiveness of ways to mold a bone so as to be a proper shape to each condition for correcting considerable deformation ( arthroplasties including corrections of dynamical environments such as formation of acetabular and bone cutting operation for higher tibia ) has been already, widely known,
future-type treatment systems for joint in which above arthroplasties are combined with technologies to regenerate cartilage are being prepared ( about 2013 ).
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Fig 25 shows a treatment system to which a technology to regenerate cartilage is added after an arthroplasty such as bone cutting operation for higher tibia and formation of acetabular.
Under the treatment system, a fibroin-sponge with one highly strengthened membranous side is pasted on the injured part to which an arthroplasty and an operation to promote the re-generation of cartilage ※ are applied.
※ A hole is made on the surface of the joint, the treatment to easily lead inner-cells to an injured part through such a hole.
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Fibroin is a protein extracted from a refined silk thread.
If cells are scattered over a fibroin-sponge ( a kind of porous medium ), healthy chondral tissues are formed around the put cell.
And, the following case is reported in a clinical model applied to kneecap ( replacement surgery for a patellofemoral joint ).
In the case, if a silk-fibroin over which chondral cells are scattered is pasted on a lost chondral part, chondral tissues similar to articular cartilages are actually formed after 2 〜 6 weeks.
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Chondral tissues formed near the pasted fibroin are bonded to the joint, both scattered cells and cells near the joint are shifted to the injured part, consequently, chondral tissues are formed on the injured part.
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25：Ground Stone Redux：2019/11/14(木) 21:59:22 ID:aBjyCzo60
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Furthermore, it was found out that even if scattered cells are replaced with own bone marrow cells, chondral tissues are well repaired.
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Accordingly, when bone marrow liquids extracted in performing a surgery are injected into a fibroin-sponge without culturing in vitro,
if the fibroin-sponge ( into which bone marrow liquids are injected ) is pasted on the damaged part, it’s expected as a new treatment method to self-organize cartilages under the pasted part.
But, why proteins refined out of silks have such healing effects has never been made clear yet ( in 2013 ).
27：Ground Stone Redux：2019/11/14(木) 22:23:16 ID:aBjyCzo60
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According recent researches, it has been made sure that a cluster composed of cells moves around in a fibroin-sponge.
It’s supposed that cellular clusters formed in this fibroin and cells in vivo cooperatively generate functional tissues near the material.
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5.2.5-3 Development of medical technology on life and risk communication
In technological development for medicine & welfare, it’s often insufficient for improvement in medical level to prolong lifespan and remove pain.
For example, even if it becomes possible to save a life from some intractable disease owing to medical progress, it’s possible that the person survives with certain disability.
Actually, such cases are increasing.
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Furthermore, regarding this country as a family of 20 members hypothetically, it’s supposed that 10 members of them work, those 10 members bear remaining 10 members.
In this case, if the work of one person of working 10 members is to take care of a sick person, then substantially 9 members bear lives of 20 members.
Medical・welfare works are included in a main mature industry in the future.
By the way, if two members of 10 members take care of two sick persons as its main tasks, is it actually possible that 8 members bear lives of 20 members ？
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The increase of borne medical expenses until now has been supposed by improvement in productivity in society.
But, keeping exhaustion of resources, reconstruction of old buildings in mind, we can’t expect improvement in productivity over the whole society so much.
