THE ANATOMIC REPLACEMENT PROSTHESIS SYSTEM IN THE HAND AND WRIST

Abstract: 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 arthroplastie. Unfortunately, the current status of the total wrist replacement arthroplastie is not so successful as some other joints. Consequently, total wrist arthroplastie is a kind of option which surgeons usually try to avoid. Here a new conceptual approach to wrist replacement arthroplasties has been brought to the agenda which permits the surgeon the partial and/or hemipartial joint replacement. In case of necessity, this partial arthroplastie can be converted to total joint replacement, and can be used in tumors, traumatic degenerative and rheumatismal conditions of this joint.

Description: THE ANATOMIC REPLACEMENT PROSTHESIS SYSTEM IN THE HAND AND WRIST. Currently, the wrist prosthesis are the applications which replaces both radial and carpal components of this joint. In such prosthesis the amount of carpal resection is quite considerable and the resultant changes in the wrist biomechanics leads to some dissatisfaction which ends in limited application and as so as delate the timing of the operation till the highly advanced degenerative joints. Currently, the wrist biomechanic is not very well understood yet. Especially the kinematics 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 of 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 carpal 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 current status of the prosthetic applications in hand surgery can be checked 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 American 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 be obligated to apply prosthesis to the carpal side of the joint increse the risk of complication and become a "too much treatment". In applications of the total wrist prosthesis, loosening seen particularly in carpal component and the stability lost due to the wide carpal resection are still unsolved problem. Therefore, many surgeons keep away from total wrist prrosthesis surgery and prefer artrotdesis or delate the surgery until extreme deformity occurs. Here mentioned, new concept enables the prosthetic replacement of only the damaged part of the joint (taumatic, tumoral, degeneretive and so on). Likewise with the assistance of the limited replacement arthroplastie maintains 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 fractures, giant cell tumors. Generally happens within the distal radius . In such cases, on arthroplastie which reconstruct to only the radial part of the 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 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 realisation of further experimental 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 replacement of degenerated surfaces. Moreover, if only a part of radial articular surface is found degenerated (Skafoid or Ulnar fossa), again the limited replacement 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 yet, in case of distal radiovulnar joint degeneration the talensik modification 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 application^ Whether TFCC (Triangular fibrocartilage complex) is infact or not, and the carpal instability added or not, may imply little modifications in the design is prefered. In accordance with the abovementioned principles , partial surface replacement prosthetic applications are nor described and realised for finger joints. Till today 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 holds one articular surface of MP or PIP joint may imply a contradiction for reviscularisation 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 the joint space between the prosthetic material and opposing normal articular surface can be made. Practice might be by cement or not. Bone graft, porous-coated, hidroksipatit inpregrinated surface, bone-ongrowth, bone-ingrowth phenemenonstaken in to consideration when designing prosthesis. Modular system; style articular surface stem 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 assistance 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 beginning the proyotype model will possess an extension screw system, in the case of necessity this will be modified. Distal radial articular surface inclination angle is given generally in two different plans as 23 and 11 degree. However, we have seen considerable modifications in our measurements. 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 will be designed to allow this accomadation. It is obvious 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 fasciliatate the insertion of the prosthesis some distraction will probably be needed. Thus a kind of external fixation device will be utilized in addition to this, multiple raspes, osteotoms and specially designed insertion devices are indispensable for this goal. These instruments will be developed in experimental studies and in following days newly designed versions will be invented. Incase of necessity custom made prosthetis will be provided. 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 to the stability of the device. 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 with difficulty to repair, special design to embody this area may be utilized. 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 damaged part of the wrist joint with an anatomically designed prosthetic device, healthy parts will be left intact, then only in the case of necessity other parts of the joint 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 furniture group available commercially. In following designs, main details have been mentioned on the radial prosthetic component shown in approximately natural dimensions. It must be kept in mind that necessary modifications will be realized in details. ILLUSTRATION 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. The groove of 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. ILLUSTRATION 2: Profile: 9. The hole for the screw 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. Since the explanations in the text are sufficient 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.

Claims: CLAIMS 1. Radial prosthetic component may be manufactured as a metalic or synthetic plastic device. The prosthesis is composed of two modular component which are articular surface and intermediate part (1) and tail part (5) these two modules may be fixed to eachother with the help of expension screw (4). On the other hand, the interimediate modul which is fabricated in an elipsoidic cross-section shape to fill the metaphysis of the distal radius and having wings (2) may be hold together, with body and tail parts, owing to the power of negative pressure working of a ball and socket joint. The intermediate part (module) (7) and the tail part (module) (5) may be submitted to porous- coating coverege, hidroksiapatit coverege processes or may be polished. As an other alternative, intermediate part and tail part may be manufactured as custom - made product to proper to the bone lesion in question. Several holes and sulcus (gouges) (8) may be opened on the prosthetic device to help to necessary manipulations during the insertion and removal of the device, or to fix the ligaments. Also holes (3) for which are going to be filled with bone grafts can be created. The joint surface part imitates the anatomic contours of the distal radial articular surface. In the intermediate part there are screw holes to serve either to fix the instrument (4) or to expend the tail part (6). 2.1n cases when the only replacement needed is the articular surface which is corresponding to the scaphpoid or the lunate the design of the prosthesis will immitate either the scaphoid or the lunate in such a way to wiev intact the healthy part of the distal radial articular surfacc.(Hemipartial application) 3. In designs created for finger joints the particularity of the system is in fact the articular surface of the device is exactly anatomic, thus can be applied as partial replacement prosthesis without any intervention need to the healthy opposing articular surface. AMENDED CLAIMS [received by the International Bureau on 3 Duly 1997 (03.07.97); original claims 1 and 2 amended; remaining claim unchanged (1 page)] 1. Radial prosthetic component may be manufactured as a metalic or syntetic plastic device. The prosthesis is composed of two modular component which are articular surface and intermediate part (1) and tail part (5) these two modules are to be ' designed to be fixed to eachother with the help of expension screw in a position of articular surface which is appropriately adjusted according to the personnel variations of the distal articular surface of each patient(4). On the other hand, the intermediate modul which is fabricated in an elipsoidic cross-section shape to fill the metapysis of the distal radius and having wings (2) may be hold together, with body and tail parts, owing to the power of negative pressure working of a ball and socket joint. The intermediate part (module) (7) and the tail part (5) may be submitted to porous-coating coverege, hidrol siapatid coverege processes or may be polished. As on other alternative, intermediate part and tail part may be manufactured as costum-made product to proper to the bone lesion in question. Several holes and sulcus (gouges) (8) may be opened on the prosthetic device to help to necessary manipulations during the insertion and removal of the device, or to fix the ligaments. Also holes (3) for which are going to be filled with bone grafts can be created. The joint surface part imitates the anatomic contours of the distaf radial articular surface. In the intermediate part there are screw holes to serve either to fix the instrument (4) or to expend the tail part (6). 2. In cases when the only remplacement needed is the articular surface which is corresponding to the scaphoid or the lunate, the design of the prosthesis will imitate either the scaphoid or the lunate in such a way to leave intact the healtly part of the distal radial articular surface. (Hemipartial application) 3. In designs created for finger joints the particularity of the system is in fact the articular surface of the device is exatly anatomic, thus can be applied as partial replacement prosthesis without any intervention need to the healty opposing articular surface.

Inventors: EGE AHMET, EGE, AHMET
Applicants: EGE AHMET, EGE, AHMET
Application year: 1997
Main classification: A61F2
IPC codes: A61B17, A61F2