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    • 专利摘要:
    Partial prosthesis for the scaphoid bone. This invention relates to a partial scaphoid bone prosthesis, adapted to replace, after an exeresis of a proximal portion of the actual scaphoid, said removed proximal portion, thereby keeping at least the distal pole of the scaphoid bone intact and also with integrity of the scapho-trapezius-trapezoid joint. It has the advantage that it does not have an anchor at the level of the radius that crosses the radiocarpal joint, but rather that the prosthesis is kept in position thanks to: (a) an anchor at the distal level to the scaphoid bone remnant thanks to the provision of a blind hole, for example by means of a threaded morse cone system, and (b) a stabilization at the proximal level thanks to the provision of proximal channels for the passage of a tendon plasty formed by the Flexor Palmar Largo or Plantar Delgado muscle to the lunate bone. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2778573A1
    申请号:ES201930102
    申请日:2019-02-08
    公开日:2020-08-10
    发明作者:Barbero Patricia Gomez；Alonso Daniel Montaner；Perez José Luis Rodrigo
    申请人:Universitat de Valencia；Fundacion para el Fomento de la Investigacion Sanitaria y Biomedica de la Comunitat Valenciana FISABIO；
    IPC主号:
    专利说明:

    [0004] The present invention relates to a partial prosthesis of the scaphoid bone, adapted to replace, after an exeresis of a proximal portion of the actual scaphoid, said removed proximal portion, thereby keeping at least the distal pole of the entire scaphoid bone undamaged and also with integrity of the scapho-trapezius-trapezoid joint.
    [0006] Background of the invention
    [0008] The wrist, and especially the carpal bones, form a joint joint subjected to significant forces of shear, torsion and compression. The scaphoid bone is the first external bone of the first row (proximal row) of the carpus. It has a cuboid shape, with six faces, of which four are articular, and presenting a proximal pole and a distal pole. It articulates with the radius, lunate bone, large bone, trapezoid bone, and trapezius bone. Within the carpus, the scaphoid plays a fundamental role as it acts as a connecting link between the two rows. Any alteration in it entails a modification of the biomechanics of the wrist, causing an abnormal transmission of loads between the radius and the scaphoid that leads to pain symptoms with loss of mobility and in the future to joint instability that will lead to carpal osteoarthritis.
    [0010] On the other hand, after an impact to the hand or wrist, scaphoid bone fractures are the most common, representing 80% of carpal fractures. The importance of its correct diagnosis and treatment in the acute phase is fundamental for the prognosis and evolution, since untreated or incorrectly managed lesions of this bone will have long-term complications such as the absence of consolidation or pseudoarthrosis, avascular necrosis in up to 50 % of cases or chronic instability that will progressively lead to the development of carpal osteoarthritis.
    [0012] Chronic "non-union" of the scaphoid and post-traumatic or idiopathic avascular bone necrosis (NOA) (Preiser's disease) are closely related to its anatomy, since the scaphoid bone is covered in more than 80% of articular cartilage where the supply The main blood supply comes from the dorsal radial artery (70-80%), through the ligamentous attachments, although the blood supply at the proximal pole depends only on the intraosseous flow, which explains the rates of delayed union, recalcitrant nonunion, or NOA. In the face of any of these mentioned injuries, it will be indicated to carry out a surgical procedure in order to start the osteogenesis process again, correct bone deformities and avoid carpal collapse secondary to non-union.
    [0014] Among the primary surgical options, the use of vascularized and non-vascularized bone grafts, with or without supplementary fixation with needles and screws, is considered. Unfortunately, these techniques are not always successful, and in some cases we find episodes of pseudoarthrosis or advanced NOA where, secondarily, an instability of the midcarpal joint has been generated that leads to the development of osteoarthritis and carpal collapse, following the patterns called SNAC wrist ( “Scaphoid nonunion advange collapse ').
    [0016] The progression of the SNAC wrists is slow, presenting arthritic changes from 5-10 years after the initial injury in the scaphoid. In the SNAC wrist with the presence of a proximal scaphoid fragment, the joint between it and the radius remains preserved for many years, acting as a second lunate, which on many occasions does not prevent a progressive degenerative process of its cartilage, fragmentation and trabecular collapse. The problem of advanced carpal collapse is that it raises additional treatment difficulties, in many cases not well resolved, since in most cases salvage surgical techniques are chosen (proximal carpectomy, scaphoid excision or midcarpal arthrodesis such as the four corners or of the luno-grande joint or total arthrodesis), where pain is controlled but sacrificing a great joint range with the consequent functional limitation in daily activities. In addition, all these surgeries, increasingly aggressive, carry a high risk of complications such as infection, pseudoarthrosis, failure of the support system, prominence of the system with irritation of the soft tissues or rigidity associated with a prolonged time of immobilization. In fact, in four-corner arthrodesis or carpectomy, the midcarpal joint is removed, and revision of these interventions requires a total wrist arthrodesis or arthroplasty.
    [0018] The mission of an orthopedic surgeon should be to try to relieve pain while maintaining the greatest range of motion and strength possible.
    [0020] In most joints of the human body the use of arthroplasty is established in cases of osteoarthritis or NOA in order to recover the previous joint situation, controlling pain and trying to preserve the greater joint range. However, at the level of the radioscaphoid joint, reconstructive surgery gives way to salvage surgery, where the patient's pain is effectively controlled, but at a very high price. In these cases, an alternative should be available where the patient could be offered more mobile wrists without pain, with prosthetic replacement being a feasible alternative.
    [0022] Scaphoid excision represents an alternative in the treatment of advanced carpal osteoarthritis. Scaphoidectomy is a relatively simple technique for those patients with symptoms secondary to chronic nonunion of the scaphoid or bone necrosis of the proximal fragment, a fragment with a more precarious vascularization where this pathology generally settles.
    [0024] Scaphoid excision can be partial at the distal pole, at the proximal pole, or complete. Isolated complete scaphoidectomy is a technique currently ruled out since it presents problems associated with progressive carpal collapse with pain, significant loss of strength and mobility. Therefore, if performed, it requires complementary techniques to stabilize the rest of the bones so that they transmit the load through the lunate bone.
    [0026] The idea of stabilizing the carpus after excision of the scaphoid with arthroplasty has been tried repeatedly. Its defenders argue that it is a simple and less aggressive technique than salvage techniques where the anatomy and biomechanics of the carpus are recovered without sacrificing other joints. Furthermore, in case of failure there is always the possibility of resorting to a four-corner arthrodesis or proximal carpectomy.
    [0028] Currently there are some models of prostheses designed to replace the entire scaphoid bone. For example, European patent No. EP3170477 and WO201886765 describe respective scaphoid prostheses manufactured in a compatible biomaterial, where this material can comprise at least one element from the group consisting of titanium or be a polymer, such as a polyetherketone or a ceramic material. , eg, a ceramic material containing zirconium. However, for stabilization of these scaphoid prostheses they have a central channel along their axis. In this, the tendon plasty is passed, which is fixed by drilling a channel (110) through the lunate where the tendon is passed again according to the Henry / Corella technique and the dorsal and palmar ligaments of the scapho-lunar are biomechanically reconstructed to ensure the physiological movement of the prosthesis.
    [0030] They are also known from patent document No. US4198712 and US4936860 respective complete scaphoid prostheses. In the first case (US4198712) a complete anatomical replica prosthesis of the scaphoid is described, with a stem (78) that is inserted in the trapezius (that is, in the bone of the distal row of the carpus) and is fixed to the lunate with a suture Transosseous with 2-0 Dexon to provide stability to the implant, or in cases where the patient's anatomy does not allow the use of stems, this can be shortened or even eliminated and fixed by means of a transosseous suture to the trapezius. It is made of an elastic material. In the second case (US4936860) a complete anatomical replica prosthesis of the scaphoid is also described, but in this case metallic, and presents a shaft (104) that extends inside the body of the implant. It is positioned on the wrist with the shaft that is inserted into the trapezius to provide stability to the implant with a procedure similar to that described in patent No.US4198712. The first published results of the first prosthesis (US4198712) were very encouraging, however, in the long term it was observed that the carpal collapse progressed, possibly associated with the development in most patients of a synovitis due to silicone particles (88% at 8 years) 12,13. This fact led to implant removal in some series in 90% of the patients due to pain requiring partial arthrodesis interventions in approximately 25-30% of cases.
    [0032] Failures in attempts to replace the scaphoid have been attributed to the material, synovitis secondary to silastic, and implant instability. Implant instability has been observed in many of the current models, regardless of the material used, with pain, implant flexion and carpal collapse with deformity in DISI.
    [0034] The pyrolytic carbon material has been used in arthroplasties of the trapeziometacarpal, interphalangeal or lunate joint.
    [0036] A prosthesis, in this case partial, in the shape of an ellipsoid for the proximal pole of the scaphoid, made of pyrolytic carbon, is known through patent document No. US6090145. This prosthesis is known as APSI "Adaptive Proximal Scaphoid Implant" (Bioprofile®, Grenoble, France), and is used for cases of avascular necrosis or proximal nonunion without arthritic signs in the proximal radioscaphoid joint. Said prosthesis is inserted between the lunate bone and the distal scaphoid remnant after excision of the proximal pole, its stability lies in the three-dimensional adaptation of the implant to the movements of the wrist. Therefore, it does not provide any type of fixation element to the rest of the bones or ligaments of the carpus and only acts as a mere spacer, that is, it is in mobile contact with at least one bone surface and the implant remains free. It has been found that, in the short term, this prosthesis allows a recovery of the grip strength similar to the contralateral wrist, a symmetrical mobility to the contralateral side. However, it is difficult to understand that an implant that dispenses with the support provided by the intrinsic carpal ligaments can be kept in place simply with the help of the joint capsule or its three-dimensional morphology, so with this implant the problem of Instability. There are currently long-term studies with a mean follow-up of 8.7 years that corroborate this, presenting 21% of implant dislocations or deformity in DISI. Therefore, the problem of stabilizing a partial scaphoid prosthesis persists in an attempt to keep the implant in position to minimize the risk of implant dislocation and for it to function according to carpal kinematics.
    [0038] In view of the above, there is an obvious need for a partial prosthesis of a proximal part of the scaphoid bone, which allows the prosthesis to be stabilized to keep it without displacement and that it works according to carpal kinematics, thus reducing and even completely eliminating the risk of a dislocation of the prosthesis.
    [0040] Description of the invention
    [0042] In the description of this invention, the term implant or prosthesis is used interchangeably, with the same meaning.
    [0044] In describing this invention, the term "proximal" is used as the part of the scaphoid closest to the radius, and the term "distal" as the part of the scaphoid furthest from the radius.
    [0046] The object of the present invention is to provide a partial prosthesis for a proximal part of the scaphoid bone of a patient, which solves the aforementioned drawbacks and presents the advantages that are described below.
    [0048] According to a first aspect, the present invention provides a partial prosthesis of the scaphoid bone, adapted to replace, after an exeresis, a proximal part of the scaphoid real of a patient, said proximal part removed, while the remaining part of the real scaphoid corresponding to the distal side remains in place without being removed as a bone remnant, characterized in that it comprises a body:
    [0050] - with a shape and external dimensions that correspond substantially to the actual morphology of the removed part of the scaphoid corresponding to a portion of the proximal side of the scaphoid,
    [0052] - which, on the distal side, comprises a blind hole that extends along the prosthesis, where this blind hole comprises at least one threaded portion so that a fixation element can pass through the scaphoid bone remnant in a retrograde direction to stabilize the prosthesis distally, and
    [0054] - which, on the proximal side, comprises through channels for the passage of a proximal tendinous plasty with the Flexor Palmar Largo muscle or with the Plantar Delgado muscle to the lunate bone, so that the prosthesis is anatomically stabilized at the proximal level with the lunate bone.
    [0056] Furthermore, the prosthesis is made of a material that comprises a biocompatible material.
    [0058] The prosthesis of the invention is based on maintaining the intrinsic capacity of the wrist at the distal pole, not affected in most cases, and making an anatomical partial prosthesis that only requires stabilization at the proximal level. In other words, instead of completely replacing the scaphoid, the distal third of the scaphoid is kept together with the trapezius, so that the prosthesis of the invention respects the intrinsic ligaments of the wrist, which play an important role in carpal kinematics during the different movements, especially in the movement "to throw darts." In addition, this distal scaphoid remnant will be used for the distal anchoring of the prosthesis, so that in future movement of the wrist they act as a single block imitating the previous movement of the scaphoid .
    [0060] In other words, the prosthesis of the invention advantageously does not act as a simple spacer (as is the case of patent No. US6090145) that, due to its curved surfaces and the low coefficient of friction presented by pyrolytic carbon, allows the prosthesis to slide , which is undesirable since it leads to a risk of implant dislocation. This type prosthesis type "spacers" were placed where previously damaged bone was and filled its space to prevent collapse. The problem is that these systems were not fixed to other carpal bones trying to reproduce the normal anatomy of the wrist where there are multiple intrinsic and extrinsic ligaments that allow it to act in a coordinated and synchronous manner.
    [0062] Furthermore, another advantage is that this invention does not have any anchor at the level of the radius that passes through the radiocarpal joint, which is also undesirable. On the contrary, the implant of the present invention is optimally held in position in the patient, thanks to:
    [0063] - (a) its anchorage distally to the scaphoid bone remnant thanks to the provision of a single blind hole at the distal level, for example by means of a threaded morse cone system, and
    [0064] - (b) to its stabilization at the proximal level in a totally anatomical way with the lunate bone thanks to the provision of proximal channels for the passage of a tendinous plasty formed by the Flexor Palmar Largo muscle or with the Plantar Delgado to the lunate bone.
    [0066] Another advantage is that for prosthetic stabilization, this invention does not use the flexor carpis radialis, a tendon involved in carpal kinetics that allows flexion of the hand on the forearm and also acts in part of the pronation and abduction movements. Failing that, the Long Palmar Flexor (Palmaris Longus) is used, an inconstant, narrow and elongated muscle that does not contribute to the kinetics or kinematics of the carpus, so that it may even be absent in 20% of patients, specifying then the use of another donor tendon that does not alter the normal biology or mechanics of the body, such as the Plantar Delgado.
    [0068] Preferably, the knockout is arranged in a substantially central position within the body, and in the desired orientation.
    [0070] Preferably, the threaded portion of the blind hole is disposed at the proximal end of said blind hole. The aforementioned threaded portion of the blind hole comprises, according to a preferred embodiment, a thread in the part of the proximal end where it will engage the coil of the compression screw that has a different thread pitch and a different diameter between the proximal and distal portion to allow compression. at the time of positioning the scaphoid. In the real scaphoid bone remnant, self-drilling is performed by passing the self-tapping and self-drilling screw mentioned above.
    [0072] Optionally, the surface of the prosthesis that contacts the scaphoid bone remnant comprises a rough, i.e. unpolished material. This, advantageously, achieves a correct osseointegration with the bone remnant and avoids micromotion.
    [0074] According to a second aspect, the present invention provides the above-described partial prosthesis that further incorporates the fixation element, to anchor the prosthesis to the distal scaphoid bone remnant. Preferably, the fixation element is a cannulated screw with a length between 18 and 26 mm. This cannulated screw is introduced through the bone remnant in a retrograde direction (ie distal to proximal), stabilizing the prosthesis. During the intervention, it is preferably guided by a Kirschner wire that allows the remnant to be connected to the prosthesis. The effects of this connection to the bone remnant consist of a decrease in the “microgap” between both components (prosthesis and scaphoid bone remnant). This fact is verified, from a mechanical point of view, in a decrease in the implant-bone remnant micro-movements, supported by an increase in the contact surface of the same, with the consequent improvement in stability.
    [0076] As initially commented, the prosthesis comprises proximal channels that allow a proximal (biological) tendon plasty to pass with the long palmar flexor or, failing that, with the plantar thin to the lunate bone. In the design process of the proximal plasty, the reconstruction of the dorsal lunate ligament is used, as in the 3LT technique of Marc García Elías, and in the same way, the ulnar traction of the lunate and pyramidal is decreased by tightening the joint. to the radiopyramidal ligament.
    [0078] This proximal tendon plasty that passes through channels from the proximal pole of the scaphoid prosthesis to the lunate bone simulates the scapholunate ligament. With this, the prosthesis is intended to simulate the scaphoid in carpal kinematics, avoiding its flexion and subluxation when applying loads.
    [0080] According to a preferred embodiment of the invention, these proximal through channels of the prosthesis body are two channels that intersect each other, forming a "T", so that there are three openings in the body. These channels are preferably straight. These canals have such a diameter to be able to pass a tendon plasty.
    [0082] The operation to anatomically stabilize the prosthesis with the lunate bone at the proximal level is detailed below:
    [0084] 1. Extraction of the proximal part of the scaphoid bone, keeping a distal part not extracted.
    [0085] 2. Drilling a blind hole in the distal side of the scaphoid bone remnant for the passage of the fixation element.
    [0086] 3. In order to anatomically stabilize the prosthesis with the lunate bone at the proximal level, the lunate bone must have previously been drilled through two openings (opening from dorsal to palmar and opening from the lunate side toward convergence with the other perforation), so the doctor opens two channels in the lunate bone connected to each other.
    [0087] 4. The partial denture is placed.
    [0088] 5. The partial prosthesis is anchored distally with a retrograde fixation screw.
    [0089] 6. It begins to stabilize it at the proximal level, passing the plasty through the most dorsal opening of the scaphoid and the plasty is removed from the side of the lunate. Then the doctor introduces the plasty to the lunate through its palmar opening, leaving through the dorsal.
    [0090] 7. Then again, the doctor introduces the plasty through the same dorsal opening of the scaphoid and this time takes it out through the most distal opening to finally suture the tendon on itself without losing traction.
    [0092] Preferably, the shape and exterior dimensions of the body of the prosthesis correspond substantially to the actual morphology of a part of the distal side greater than the proximal pole itself. According to a preferred embodiment of the invention, the shape and outer dimensions of the prosthesis body correspond substantially to the actual morphology of the 2/3 parts of the proximal side of the actual scaphoid removed from a patient, while the remaining distal 1/3 of the scaphoid remains in place without retreating. However, a partial prosthesis of a proximal part can be made with a portion other than 2/3 parts as long as it is sufficient to allow proximal stabilization of the lunate with a plasty through the transosseous channels mentioned above and allows the retrograde screw pitch exerting distal stabilization.
    [0094] The body of the prosthesis has a narrowing at the level of the navicular waist resulting, simulating the waist part of the actual removed scaphoid. It also has a base on the distal side, substantially flat, for connection to the distal bone remnant.
    [0096] The shape and external dimensions of the body of the prosthesis will depend on the anatomical shapes and sizes of the scaphoid of each patient. The prosthesis is manufactured, preferably, in three different sizes, and a prosthesis for the left side and others for the right side. However, this prosthesis can be made to measure, according to the specific dimensions of each patient. It can be manufactured according to known manufacturing techniques, for example by 3D printing.
    [0098] After numerous measurements carried out by the holders, it has been seen that the optimal external dimensions of the prosthesis can vary according to the following parameters:
    [0100] - length of the body of the prosthesis from the proximal end to the distal end added to the length of the bone remnant between 25 and 31mm.
    [0102] - thickness at the level of the scaphoid waist of the prosthesis is between 8 and 11.9mm.
    [0104] Due to this variability in length and thickness, it has been decided to make the prosthesis of the invention in three different sizes, in order to mold the prosthesis to the best anatomy of the patient.
    [0106] Preferably, internally, the blind hole of the prosthesis extends along the prosthesis with a total length between 10 and 20mm. and has a diameter between 3 to 4mm., and more preferably 3.5mm.
    [0108] Also preferably, the proximal channels of the prosthesis have a diameter between 2 and 4mm, and more preferably between 2.5 and 3.5mm.
    [0110] Optionally, the exit of the central hole and the proximal channels can be rounded or blunt, so as not to damage the plasty and prevent it from breaking or cutting.
    [0112] Preferably, the body of the prosthesis is made of an outer portion of biocompatible ceramic. For example, it can be made of a metallic alloy with at least one biocompatible ceramic outer portion. Pyrolytic carbon can be chosen as the ceramic, although the use of other ceramics is also possible, for example ceramic alumina which has been used successfully in hand implants. Pyrolytic carbon is a totally biocompatible material, highly resistant to deterioration by friction, practically indestructible and chemically inert, without causing bone wear. Its coefficient of friction is very low, which allows the implant to slide without causing bone wear in order to achieve the least resistance. Furthermore, its Young's modulus, identical to that of bone, allows it to be perfectly tolerated.
    [0114] The prosthesis of the present invention is used, preferably, in cases of recalcitrant pseudoarthrosis of the scaphoid, avascular necrosis thereof, Preiser's disease, acute fractures with great comminution or displacement where it is impossible to perform an anatomical reduction and primary osteosynthesis, or in cases of Incipient osteoarthritis of the wrist secondary to advanced collapse due to scaphoid nonunion, provided there is no compromise of SNAC II I-IV type intercarpal degeneration.
    [0116] The most significant thing that differentiates the prosthesis of the invention from other implants is that it remains stabilized to the rest of the carpal bones, imitating the native scaphoid and, therefore, fully integrated with the carpal kinematics. In this way, there is an implant that replaces the non-viable part of the scaphoid but keeping the distal third of it, which allows prosthetic anchoring and behaves as a unit. In addition, the prosthesis is also stabilized at the proximal level to recreate 100% carpal anatomy and kinematics.
    [0118] Thanks to the advantageous configuration of the prosthesis, they make it unique and different from what currently exists on the market.
    [0120] Brief description of the figures
    [0122] For a better understanding of what has been explained, some drawings are attached in which, schematically and only as a non-limiting example, practical cases of different embodiments are represented.
    [0124] Figures 1 to 5 represent different views of a possible embodiment of the prosthesis of the invention, where the shape and external dimensions are appreciated, as well as the three openings of the two proximal channels for the passage of the plasty and the distal side opening of the central blind hole.
    [0126] Figure 6 schematically represents the carpal bones, where the scaphoid bone has not been removed.
    [0128] Figure 7 schematically represents the carpal bones in a position other than that of Figure 6, where the most proximal part of the scaphoid bone has been removed and has been replaced by the partial prosthesis of the invention and with the plasty inserted.
    [0130] Figures 8 and 9 schematically represent respective detailed views of the prosthesis of the invention once positioned in a patient and with the plasty inserted.
    [0132] Figure 10 schematically represents a possible embodiment of the cannulated fixation screw.
    [0134] Description of some examples of realization
    [0136] Some embodiments of the present invention are described below with reference to Figures 1 to 10.
    [0138] The kinematic behavior of the prosthesis (10) of the invention has been empirically tested by the owner in cadavers, with satisfactory results. The tests carried out were:
    [0140] - First the corpse forearm piece is prepared (with 4 to 6 specimen pieces). Almost all of the soft tissues are removed both proximally and distally, leaving only four axes of traction corresponding to the flexor carpis radialis, flexor carpis lunaris, extensor carpis lunaris and extensor carpis radialis longus and brevis that work together. The forearm is attached to a support by means of screws anchored in the ulna and radius and connected to a photogrammetry system with several dynamometers in the 4 main tendons that allows to apply flexion-extension forces and radial and ulnar deviation and analyze them.
    [0141] - The 2/3 of the carpal scaphoid is then replaced by the previously designed prosthesis that is stabilized and the same kinematic analysis is repeated.
    [0143] - During the movement everything is captured with cameras and load cells to be able to extract the frames and calculate the relative position of the markers and the traction forces, the Euler angles and the instantaneous centers of rotation.
    [0145] In addition, the study is completed with radiographic measurements of flexion-extension, prono-supination, and lateralization movements.
    [0147] As shown in Figure 6, where the situation of the carpus is represented in which the prosthesis (10) has not yet been placed, the complete real scaphoid bone (1) is arranged in the carpus being in contact with the trapezoid (6), the trapezoid (5), the large one (4), the lunate (3), and the radius (7). The scaphoid bone (1) has a length "A" and a thickness at the level of the waist "B", the parameters of which will depend on each patient.
    [0149] On the other hand, Figures 7 to 9 represent the situation of the carpus in which the prosthesis (10) of the invention has already been placed in place, keeping the bone remnant on the distal side of the scaphoid bone (2). In said Figures it can be seen how the prosthesis (10) is fixedly attached to the bone remnant (2) by means of a screw (in Figures 7 to 9 only the hole (12) is shown while in Figure 10 the screw (18 ), which is arranged within the central blind hole (12). Proximally, the prosthesis is anatomically stabilized with the lunate bone (3) by means of a tendon plasty (23) with the Flexor Palmar Largo muscle or with the Plantar Delgado This tendon plasty (23) is arranged by forming two loops that pass through the channels (16 and 17) following the operations described in the part of the Description, and being fixed by means of a suture point (22), see Figures 8 and 9. Preferably, the final end and the proximal end of the plasty (23), once the two loops have been passed, are sewn on the same plasty (23) already passed.
    [0151] As can be seen in the attached Figures 1 to 5, this particular embodiment of the prosthesis (10) of the invention presents a body with a shape and external dimensions that substantially correspond to the real morphology of 2/3 parts of the proximal side that have previously been removed from the scaphoid of a patient. It has a surface (11) on the distal side that is substantially flat, where an opening (12a) is provided which extends to form the central blind hole (12). The body of the prosthesis is solid and at the proximal level It has three openings (13, 14, and 15) that form two channels (16, 17) that intercept each other for the passage of the plasty (23). The first channel (16) extends from the first opening (13) until it reaches the second channel (17), and this second channel (17) extends from the second opening (14) until it reaches the third opening (15). It can be seen in Figure 5 how these two channels intersect forming a "T" shape.
    [0153] Returning again to Figures 7 to 9, in them a possible configuration of the blind central hole (12) of the prosthesis can be seen, which has a thread (13a) at the proximal end of the central hole (13), and in the continuation of the central blind hole (12). In the bone remnant (2), a second thread will be created that will self-tapping when the retrograde screw is inserted, which is self-drilling and self-tapping (13b).
    [0155] Figure 10 shows a possible configuration of the screw (18) that is screwed inside the central blind hole (12) of the prosthesis and the continuation of the central blind hole (12) of the bone remnant (2). Said screw (18) has a slightly conical body, and is characterized in that its proximal and distal thread have different size and different thread pitch. Thus, it has a lower portion (screw head area) (21) equipped with a larger and larger thread, an intermediate portion (20) without thread, and an upper portion (screw tip) (19) provided with a smaller pitch and smaller thread, wherein the upper portion (called the first thread pitch) (19) is adapted to be threaded into the internal thread (13a) of the hole (12) of the prosthesis (10).
    [0157] Despite the fact that reference has been made to a specific embodiment of the invention, it is clear to a person skilled in the art that the partial scaphoid prosthesis described is susceptible to numerous variations and modifications, and that all the mentioned details can be substituted by others. technically equivalent, without departing from the scope of protection defined by the appended claims.
    权利要求:
    Claims (15)
    [1]
    1. Partial prosthesis (10) of the scaphoid bone, adapted to replace, after an exeresis of a proximal part of the real scaphoid of a patient, said proximal part removed, while the remaining part of the real scaphoid corresponding to the distal side remains in place without being removed as a bone remnant (2), characterized in that it comprises a body:
    - with a shape and external dimensions that correspond substantially to the actual morphology of the removed part of the scaphoid corresponding to a portion of the proximal side of the scaphoid,
    - which, on the distal side, comprises a blind hole (12) that extends along the prosthesis, where this blind hole (12) comprises at least one threaded portion (13a) so that through the scaphoid bone remnant in a retrograde direction a fixation element can pass to stabilize the prosthesis distally,
    - which, on the proximal side, comprises through channels (16, 17) for the passage of a proximal tendinous plasty (23) with a band of the Flexor Palmar Largo muscle or with the Plantar Delgado to the lunate bone (3), of so that the prosthesis (10) is anatomically stabilized proximally with the lunate bone (3), and
    - made of a material comprising a biocompatible material.
    [2]
    Prosthesis (10) according to claim 1, in which the shape and external dimensions of the body correspond substantially to the actual morphology of a part substantially greater than the proximal pole of the scaphoid, while the remaining distal part of the scaphoid remains in your site.
    [3]
    Prosthesis (10) according to claim 2, in which the shape and external dimensions of the body correspond substantially to the actual morphology of the 2/3 parts of the proximal side of the actual scaphoid removed from a patient, while the 1 Remaining distal / 3 of the scaphoid remains in place.
    [4]
    Prosthesis (10) according to claim 1, in which the through channels (16, 17) are two that converge together forming a "T", so that there are three openings (13, 14 and 15) in the body.
    [5]
    5. Prosthesis (10) according to claim 1, in which it also comprises a cannulated screw (18) as a fixation element, which has a length between 18 and 26 mm.
    [6]
    Prosthesis according to claim 1, in which the threaded portion (13a) of the blind hole (12) is arranged at the proximal end of the central hole (12).
    [7]
    Prosthesis (10) according to the preceding claim, in which the threaded portion (13a) of the blind hole (12) comprises a thread at the proximal end with a smaller thread pitch, and in the bone remnant of the scaphoid ( 2) Seats a second thread with a greater thread pitch, to allow compression when positioning the scaphoid.
    [8]
    8. Prosthesis (10) according to claim 1, in which the body is made of a metallic alloy with at least one outer portion of ceramic.
    [9]
    9. Prosthesis (10) according to the preceding claim, in which pyrolytic carbon is chosen as the ceramic.
    [10]
    10. Prosthesis (10) according to claim 1, in which the part (11) of the prosthesis that contacts the bone remnant of the scaphoid (2) comprises a rough material, that is, not polished, to achieve osseointegration with the bone remnant and avoid micromotion.
    [11]
    Prosthesis (10) according to claim 1, in which the length of the prosthesis body from the proximal end to the distal end added to that of the bone remnant (2) is between 25 and 31 mm.
    [12]
    12. Prosthesis (10) according to claim 1, in which the blind hole (12) extends along the prosthesis (10) with a total length between 10 and 20 mm.
    [13]
    Prosthesis (10) according to claim 1, in which the body has a narrowing at the level of the resulting scaphoid waist, where the resulting scaphoid is the set of the proximal prosthesis plus the distal part remaining in the patient.
    [14]
    Prosthesis (10) according to the preceding claim, in which the thickness of the body of the prosthesis (10) at the level of the scaphoid girdle is between 8 and 11.9mm.
    [15]
    15. Use of the prosthesis according to any one of claims 1 to 14, in cases of recalcitrant pseudoarthrosis of the scaphoid, avascular necrosis thereof, Preiser's disease, acute fractures with great comminution or displacement where it is impossible to perform an anatomical reduction and primary osteosynthesis, or in cases of incipient osteoarthritis of the wrist secondary to advanced collapse due to scaphoid nonunion, provided there is no compromise of SNAC III-IV type intercarpal degeneration.
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    同族专利:
    公开号 | 公开日
    WO2020161374A1|2020-08-13|
    ES2778573B2|2020-12-21|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    GB2032782A|1978-10-13|1980-05-14|Dow Corning|Scaphoid implant|
    WO1998056318A1|1995-03-09|1998-12-17|Robert Goldberg|Biaxial ligamentous-restrained prostheses for upper and lower extremity arthroplasties|
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    优先权:
    申请号 | 申请日 | 专利标题
    ES201930102A|ES2778573B2|2019-02-08|2019-02-08|PARTIAL PROSTHESIS FOR THE SCAFOID BONE|ES201930102A| ES2778573B2|2019-02-08|2019-02-08|PARTIAL PROSTHESIS FOR THE SCAFOID BONE|
    PCT/ES2020/070078| WO2020161374A1|2019-02-08|2020-02-03|Partial prosthesis for the scaphoid bone|
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