SYSTEME PROTHETIQUE DE REMPLACEMENT ANATOMIQUE POUR LA MAIN ET LE POIGNET

THE ANATOMIC REPLACEMENT PROSTHESIS SYSTEM IN THE HAND AND WRIST

Abrégé français

Dans le traitement des fractures distales du radius, l'atteinte de la surface articulaire du radius peut parfois donner lieu à des problèmes sérieux. En raison de la réduction anatomique des fragments sérieusement endommagés et déplacés, la surface articulaire ne peut pas toujours être reconstruite. Il s'ensuit donc que, lors du suivi, le patient peut afficher des changements dégénératifs progressifs au niveau de toute l'articulation du poignet, dont les surfaces articulaires des os du carpe, qui étaient peut-être intacts après le traumatisme initial. € ce stade, les options thérapeutiques englobent la fusion de l'articulation ou la mise en place d'une prothèse totale par arthroplastie. Malheureusement, à l'heure actuelle cette intervention ne connaît pas autant de succès que dans le cas de certaines autres articulations. Par conséquent, l'arthroplastie du poignet est une option thérapeutique que les chirurgiens ont généralement tendance à écarter. Dans le présent cas, une nouvelle approche conceptuelle de l'arthroplastie du poignet est présentée qui permet au chirurgien de procéder à un remplacement partiel ou semi-partiel. Au besoin, ce remplacement partiel peut être converti en remplacement total de l'articulation et cette intervention peut être utilisée dans le cas de tumeurs, de processus dégénératifs consécutifs à un traumatisme ou de maladies rhumatismales de cette articulation.

Abrégé anglais

In the treatment of distal radial fractures. the
involvement of the articular surface of the radius may in some case
cause serious problems. Because the anatomic reduction of
seriously damaged and displaced fragments of the articular
surface can not be always reconstructed. As a result of that,
in follow-up, the patient can have progressive degenerative
changes all over the wrist joint including articular surfaces of
the carpal bones which might have been undamaged after the
original trauma. At this point, the treatment alternatives are
the fusion of the joint and total replacement arthroplastic.
Unfortunately, the current status of the total wrist replacement
arthroplastic is not so successful as some other joints.
Consequently, total wrist arthroplastic is a kind of option which
surgeons usually try to avoid. Here a new conceptual
approach to wrist replacement arthroplastics has been brought
to the agenda which permits the surgeon the partial and/or
hermipartial joint replacement. In case of necessity, this partial
arthroplastic can be converted to total joint replacement, and
can be used in tumors, traumatic degenerative and
rheumatismal conditions of this joint.

Revendications

CLAIMS
1.The prosthesis is a modular partial or total articular surface replacement device used in different
pathology of the distal radial articular surface.
2.This is a systhem according to claim 1. And is constituted from three main part ,namely the tail
part (tail module) Fig 1, body part ( colar module) formed by two hemi-part Fig 2 and articular
part (articular module) Fig 3. The tail part helping to fix the prosthesis in the medullary cavity
of the bone having a couple sulcus (1) or wings to prevent the movements after the insertion and
integration in the os or cement and a cylindrical shape (4)fitting the medullary cavity holding
distally a spherical protuberence (2) helping to connect with other parts(modules)
3.The body part,also may be named the colar,has two quasi symmetrical hemi-parts fixed to each
other with a screw (6) during the application of the prosthesis. The body part helps to connect the
articular surface modul and the tail modul and fix both to each other in a desired position according
to the medullar shape pattern and the inclination of the distal radial articular surface proper to each
patient. Fig.4. This fixation(locking) occurs with a help of the central screw(6)wich connect the two
hemi-parts of the body(colar)modul while holdig between two hemi-parts the spherical connection
protuberences of the tail and articular moduls. The body modul fits the the metaphizeal region of the
radius and has two spherical cavity (7)to recive the cylindrical protuberences of the other two
moduls. Moreover in each hemi-cylindrical cavity of the radial site hemi-part of the body module
a hole fore a screw may be pierced for additional stability to fixation.(8)
4.The articular surface modul (Fig 3)is a systhem according to the claim no 1 and has constituted by
the articular surface (9) and the connecting proximal spherical protuberence (10). The articular
surface has the anatomic shape of the distal radial articular surface and it is in the configurational
harmony with the contours of the corresponding proximal carpal bones( lunate and scaphoid).
The larger site is the radial border of this modular element and may have a threaded hole( 12)
to manipulate with a holding device fitting here.
5.This is a systhem according to claims 1,2,3,4. In each module it is possible to add some screw
holes to fix the prosthesis directly to the bone with the help of screws .Also each modular part may
have wings or connected plates for additional screws fixation.
6.The prosthesis can be fabricated in different sizes or may be custom made for the patient considered.
7.In the case when the only scaphoid fossa of the radial articular surface is damaged the prosthesis
will be modified to made taking into consideration the claims 1,2,3,4,5,6 and the articular part
having only the scaphoid (radial part)of the articular modul .The body modul also will be reduced
to fit only the radial partof the radius and the spherical connection of the tail modul will also be
displaced radially to fit the off-set body part (Fig .5)
8.In the case when the only damaged part is the lunate fossa of the radial articular surface the
prosthesis will be modified taking always into consideration claims 2,5,6 and the articular surface
reconstruction concept but this time the prosthesis will be compact(monobloc) holding the articular
surface and body and tail parts fitting the lunar articular surface of the radius andthe ulnar part of
the distal radius and fixed with screws and/ or cement (13)which cross the body into the bone Fig 6
9.In designs created for finger joints the device is composed of the stem and the articular part. The stem
fits the medullar cavity of the tubular bones of the hand. The particularity is that the articular surface is exactely
anatomic thus can be applied as a partial replacement prosthesis without any intervention need to
the healthy opposing articular surface.

Description

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THE ANATOMIC REPLACEMENT PROSTHESIS SYSTEM IN THE H~ND
AND WRIST.
Currently, the wrist prosthesis are the applications which replaces both radial
s and carpal components of this joint. In such prosthesis the amount of carpal
resection is quite considerable and the resultant changes in the wrist
biome-~h:sni-~ leads to some di~sS~ti~f~rtion which ends in limited application and
as so as delate the timing of the operation till the highly advanced degenerative
joints.
10 CUI . ~..lly, the wrist biomechanic is not ve~ well understood yet. Especially the
kin~ ~tics of the skafoid and the lunatum present semifree kind of movements
from each other. However, in current practice the carpal component is either
fixed to both of these bones or, applicated after the resection o~ the alleged ones.
Beyond that, in tumor cases, affecting articular surface located in the distal
radius, when trauma or a kind of rhumatoid disease spear the carpa3 bones, but
seriously affects articular surface of the radius, until today a joint replacement
system which can only reconstruct the damaged radial part of the wrist has not
yet described.
The cu- .~nt status of the prosthetic app1ications in hand surgery can be checked
20 from thelast publication of operative Hand Surgery of David P. Green- (ISBN 0-
443-08803-9 Churchill Livingstone Publications page 143-187 ), and also the
Journal of ~n--, ;can Hand Surgery could be investigated.
It is obvious that all kinds of current prosthesis forces the surgeon to change the
wholeof the joint inevitably. When in case of the normal carpal side cartilage to
2s be obligated to apply prosthesis to the carpal side of the joint increse the risk of
co~p!iration and be~me q "too ,...uch treatment".
In applications of the total wrist prosthesis, loosening seen particularly in carpal
~ component and the stabilit~ lost due to the wide carpal resec~ion are still
unsolved problem. Therefore, many surgeons keep away from total wrist
30 prrosthesis surgery and prefer artrotdesis or delate the ~ur~ until extreme
deformity occurs. Here mentioned, new concept enables the prosthetic
repl ~c~. -c..t of only the damaged part of the joint (t~ tieS tumoral,
degc..c. ~ive and so on). Likewise with the assistance of the limited replacement

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arthroplastie r~inf~in~ the original biomechanic of the wrist joint and provides a
sort of profilactic surgery with conservation of wrist ligaments and undamaged
parts of the joint. In daily practice, the phenemenons which disturb the
morphologic and functional wholeness of such as introarticular r ~.elul~s, giantcell tumors. Generally happens within the distal radius . In such cases, on
arthroplastie which reconstruct to only the radial part of thc joint is not
described . Certainly, the prosthetic material in question will be in different types
according to the location and the stage of the pathology. For instance, incase of
benign tumors, a design possesing a massive stem (body) in order to be applied
10 with bone cement ( Methilmetakrilat) is preferable. On the other hand, in a case
of introarticular fractures the application of cementless design will be choosen as
a low profile one to leave sufficient bone tack.
With the new concept which we have been introduced here, new horizons might
possibly be lied beforestarted and with the re~ t:~ of ru~ -r experimental
15 and clinical studies prototype designs will undoubtly developed. Similarly, the
fact that the distal radial joint is affected or not will modify the choise of required
design.
Following the arthroscopic MRI and operative findings, only if the carpal bones'articular surfaces are found degenerated, sugeon may be contend with only the
20 rep~ nt of degenerated surfaces. Moreover, if only a part of radial articular
surface is found degenerated ~Skafoid or Ulnar fossa), again the limited
rep!~ce~c~lt of degenerated parts maty be choosen as a hemi-partial prosthetic
application an dspare the rest of the joint. The insertion of the radial component
may either be realized by a trans- radial -stiloid approach which is not published
25 yet, in case of distal radiovulnar joint degeneration the t~ k moAifi~~tion
approach for capanji procedure ( resection of distal ulnar) or finally current
dorsal approach used regularlt in wrist replacement arthroplastie . ~ the last one,
especially the hemi-partial application9.
Whether TFCC (Triangular fibrocartilage complex) is infact or not, and the
30 carpal instability added or not, may imply little mo~ tions in the design is
prefered.
In accordance with the abovementioned principles, partial surface rep~ac- cnt
prosthetic applications are nor described and realised for fimger joints. Till today

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surgeons exherted arthrothesis in case of introarticular fractures or benign
tumors located adjusted to finger joints. Thus the joint is sacrificed, even one of
the joint surface is compeletly intact. Furthermore, only the fracture which ho1ds
one articular surface of MP or PIP joint may imply a contradiction for
reviscularisaffon or replantation of the finger. Therefore, a simple partial surface
replacement can change the destiny of the whole finger. Also in corpometacorpal
an intercarpal joints only the damaged surfaces' anatomic replacement can be
used.
Synthetic surface may be in metal or plastic in nature. May be covered with
plastic or other material or as a measure the injection of some chemicals in thejoint space between the prosthetic material and opposing normal articular
surface can be made.
Practice might be by cement or not. Bone graft, porous-coated, hidrok~ip~tit
inpregrinated surface, bone-ongrowth, bone-ingrowth phenemenonstaken in to
consideration when de~igning prosthesis. Modular system; style articular surfacestem and body components may be fabricated to construct the assembly outside
of the body: or inside with different surgical approach with each of these.
Arthroscopic ~cs;~t~nce may probably be required. With the plate and the screw
application, additional primary stability can be obtained. Variations of plate and
screw applications can be fixedor assembled over the material.
To increase the primary stability, the stem and the body components, may be
manufactured as "expension type~'. In the be~- nin~ the proyotype model will
possess an exten~i~n screw system, in the case of ~ -cesi,ily this will be modified.
~istal radial articular surface inclination angle is given generally in two different
plans as 23 and ~1 degree. However, we have seen considerable mo~ ons in
our mea~u~ ~.e.~ts. Ideally we anticipate to accomadate the angle of the articular
surface in comparison with the other wrist, to other wrist of the patient. Either
modular and compact system ~vill be designed to allow this accomadation.
~ 30 It is ohvious that, this prosthetic system will be applied with the help of an
instrument set to provide to find the correct size, position, and the fixation of the
implant. To fasciii~t~te the insertion of the prosthesis some distraction will
probably be needed. Thus a Icind of externa~ fixation device will be utilized in

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addition to this, multiple raspes, osteotoms and specially designed insertion
devices are indispensable for this goal. These irlstruments will be developed inexperimental studies and in following days newly ~le~i~ cd versions will be
invented. Incase of necessity custom made prosthetis will be provided.
s Variations allows the fixation of the prosthesis to the bone with the help of
several devices.
In the stem and or the body of the prosthesis, a rectangular area to fill with the
bone graft to be taken with a special instrument may be helpful to contribute tothe stability of the device.
~o In the above mentioned radial styloid approach, the main concern is to protect
volar and dorsal ligaments, thus the stability of the joint. This is a new approach
not described elsewhere.
Scaphoid and lunate bones articular surfaces may be reconstructed with the help
of synthetic materials primarily or later. In the case of the scapho-lunate rupture
15 with difficulty to repair, special design to embody this area may be .Itili7e.1
As it is seen, with the help of the new conceptual approach to the prosthetic
surgery in the hand, it will only be possible to reconstruct the limited damagedpart of the wrist joint with an anatomically flçsigned prosthetic device, healthy
parts will be left intact, then only in the case of necessity other parts of the joint
20 will be changed to convert to total wrist prosthesis. While doing this, any of the
previously applicated prosthetic component will not be removed as much as
possible if it will be expressed through the help of a parable this modular
reconstruction is similar to a modular r..l if..re group available commercially. In
following fl~$ign~, main details have been mentioned on the radial prosthetic
2s component shown in approximately natural dimensions. It must be kept in mind
that necessary mo~lific~tions will be realized in detai!s.
ILLU~TRATION 1: Appearence in face
1. Joint surface commponent 2. The alar process of the intermediate part to be
hold within the spongois bone 3.The hole for bone graft 4and 6. Tlhe groove of
30 screws which help to fixation of the bone. 5. Distal stem component which has the
property of expansion. 7. The intermediate component ~part) 8. The groove for
the fixation of Triangular fibrocartilage complex.

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IELUSTRATION 2:
Profile: 9. The hole for the scre v to fix the articular component and the
intermediate component in desired position. 10. Alar process of the distal stem.11. Expansion screw hole in distal stem.
s Since the explanations in the text are suffl~icnt for the description of the
prosthetic devices except the radial component further illustrations are being
thought to be unnecesary. However the concept of anatomic surface replacement
which is the cardinale concept in the design of these is to be remembered.

Dessin représentatif