This application claims priority to European Application Number 15195745.3, filed on Nov. 22, 2015, which is incorporated herein by reference in its entirety.
The invention is related to a scaphoid prosthesis. The scaphoid is the most important carpal bone. Because of the distally based blood supply healing of fractures is at risk because the proximal pole has no blood supply and therefore only bad healing potential. If a fracture does not heal a pseudoarthrosis will develop. Untreated, the pseudoarthrosis will lead to destruction of the joint cartilage (arthrosis) and inflammation (arthritis) with pain, loss of range of motion and function.
A number of conventional approaches are available depending on the severeness of the pseudoarthrosis developed in consequence of an undetected and consequently untreated or unhealed fracture. The treatments range from placing a non-vascularized or vascularized bone graft to reconstitute the patient's scaphoid to ultimately a fusion of the carpal bones or to a resection of the first carpal row in a proximal row carpectomy.
Already in 1945 a patient specific prosthetic replacement of the scaphoid was developed using Vitallium (cobalt, chrome and molybdenum alloy). Very little is known about the use and results in the literature. Agner developed an Acrylate prosthesis in 1954 and used this prosthesis in patients [1]. Severe complications like foreign body reaction to silicone with the development of granulomas were reported. In addition, the carpal collapse could not be prevented. Although these problems were well known, Swanson brought another silicone prosthesis 1962 on the market with the same complications, such as the one disclosed e.g. in U.S. Pat. No. 4,164,793A or U.S. Pat. No. 4,158,893 A.
In 1989 Swanson reacted on these complications and developed a non-anatomical prosthesis made of titanium, such as the one disclosed in U.S. Pat. No. 4,645,505 A. There is no information upon the use of this kind of prosthesis in the literature.
Another type of placeholder is the prosthesis made of pyrocarbon by Tornier named Amandys also without any functional or biomechanical suspension or attachment to the carpal bones. An example for a composite prosthesis made of pyrocarbon and metal has been disclosed e.g. in WO2008001185 A2. The only functional and biomechanical attached prosthesis for the carpus is an implant for the lunate made of pyrocarbon by Ascension, as disclosed in US2005033426A1.
A publication in 2011 reported on a custom-made prosthesis made by titanium by Spingardi/Rossello [2] who reported on the implantation in 113 patients. Five of them dislocated within the follow-up period of 12 years.
All these prosthesis have the same problems, in that they are not biomechanical compatible and just act as a spacer without any suspension or link to the carpal arrangement. These spacers have a major complication: they tend to luxate and cannot prevent carpal collapse.
From U.S. Pat. No. 6,371,985B1 it is known to fix prostheses to bones whereby channels are drilled in these prostheses. It is intended that the bone grows into these channels thus it grows into these channels. Neither the tendon nor the prosthesis can move/glide anymore. Such a prosthesis would not meet the biomechanical need and however prevent the patient from regaining most of the flexibility of the hand, therefore the application of this technique for hand surgery appears to be unsuitable.
According to U.S. Pat. No. 5,702,468 A1, a surgically implantable carpal bone prosthesis is provided, which comprises a biocompatible, medically inert body member contoured to resemble the shape of the carpal bone, which it is to replace. The body member contains two independent channels, which are used for means for restraining the body member along crisscrossing axes. The constrained prosthesis is fixed by drilling a channel through the lunate where the tendon in the technique of Henry/Corella is passed through and sutered to itself to biomechanically reconstruct the dorsal and palmar scapho-lunate ligaments to ensure physiological movement of the prosthesis.
It is also known from WO2009076758A1 to produce an anatomical replica of a scaphoid bone based on images of the scaphoid bone of the contralateral wrist, i.e. a mirror image using computer tomography or magnetic resonance scans.
The objective is thus to develop a patient-specific prosthesis for the scaphoid bone of increased strength and stability which shall replace the pseudoarthrotic/non-reconstrucatable scaphoid in cases of impossible or failed attempts of reconstruction.
In other words, the problem is solved by providing a more accurate scaphoid prosthesis matching with the patient's scaphoid which is suitable for interaction with the portions of the anatomic structure not affected by pseudoarthrosis. For obtaining a more accurate scaphoid prosthesis, a modelling of the patient's scaphoid has been performed to provide a more accurately shaped scaphoid prosthesis.
The scaphoid prosthesis comprises a body bounded by an outer surface, whereby the outer surface is substantially corresponding to a patient's scaphoid. The body of the scaphoid prosthesis comprises a tubular base element including a first end portion and a second end portion and a plurality of protruding portions. A single curved passage is provided in the tubular base element for a fixation means for fixing the scaphoid prosthesis in its position. The curved passage is positioned in the body in such a way that the distance between the passage wall and the body surface is substantially uniform, that means the passage is arranged in a central region of the body. In particular, the distance between the passage wall and the outer surface measured along any line intersecting with the longitudinal axis is substantially uniform in any cross-sectional area arranged normally to the longitudinal axis of the passage. The advantage of adapting the curvature of the passage to the surface structure of the outer surface of the body is to maximize the body volume surrounding the passage in almost any position of the passage.
A scaphoid prosthesis is thus generated from a scaphoid model, whereby the scaphoid model is generated from patient data and corresponds in its shape with the patient's scaphoid.
Under a scaphoid model, it is to be understood a computer generated three-dimensional image of the patient's scaphoid. An image of the patient's scaphoid can be obtained by state-of-the art imaging technologies, such as X-ray imaging or MRI imaging, which can be available in a database. Due to the fact that the shape of the scaphoid prosthesis is known from the scaphoid model, it is possible to calculate the curvature of the passage from the shape as given by the scaphoid model. Thereby the body can be anatomically contoured based on data of the contralateral side or from the database. The boundary condition for obtaining the optimum curvature is determined by setting the distance between the passage wall and the outer surface to be substantially uniform, thus to be substantially the same. Thus the passage is arranged in the scaphoid model in such a manner, that the distance from the passage wall to the outer surface is substantially the same for any cross-sectional area arranged normally to the longitudinal axis of the passage.
There is a need to provide a patient specific prosthesis mounted in an anatomical structure, such as a bone assembly of a wrist. In particular, if treatment of a joint is required, it is required that the position of a plurality of engaging or interacting anatomical structures is aligned.
A scaphoid prosthesis comprises a body bounded by an outer surface, whereby the Is outer surface is substantially corresponding to a patient's scaphoid. The body of the scaphoid prosthesis comprises a tubular base element including a first end portion and a second end portion and a plurality of protruding portions.
A partial arthrodesis (4-corner fusion) or removal of the first carpal row by proximal row carpectomy (PRC) can be avoided using the scaphoid prosthesis according to the invention. In particular, by using a scaphoid prosthesis according to the invention, the anatomy and biomechanics of the wrist can be maintained. If the prosthetic replacement of the scaphoid should fail, the application of the prior art techniques remains possible.
To meet the biomechanical requirement of the wrist the prosthesis is functionally suspended using the surgical technique mentioned below. This functional and biomechanical aspect is a unique feature of the implant. The biomechanical and functional suspension of the prosthesis derives from known procedures for scapholunate ligament reconstruction, which is the ligament between the scaphoid and the lunate bone and one of the main stabilizers of the carpus. Other ligaments for the stabilization of the carpal bone are so called secondary stabilizers and are ligaments between the scaphoid and the carpus other than the scapholunate ligament. The technique for the scapholunate ligament reconstruction is performed to anchor the scaphoid prosthesis in the biomechanically correct position. Thereby, a good fixation of the prosthesis is obtained and in addition, luxation and carpal collapse are prevented, which would finally lead into the development of carpal arthrosis.
According to an embodiment, a passage is provided in the tubular base element for a fixation means for fixing the scaphoid prosthesis in its position. The fixation is advantageously obtained by a tendon strip of the Flexor Carpi Radialis tendon (FCR) passing through the passage in the scaphoid prosthesis.
In particular, the tubular base element can have a longitudinal axis substantially corresponding to the opening in the body of the scaphoid prosthesis. The longitudinal axis can extend substantially from the first end portion to the second end portion. The passage can comprise an attachment portion, which can be formed in Is particular as one of a threaded portion or a roughened portion. The attachment portion can have a smaller cross-sectional area than at least one of the ends of the passage. The threaded portion may be used for fixing a fixation element.
According to an embodiment, the passage is composed of a first hole and a second hole, whereby the first hole comprises a first longitudinal axis and the second hole comprises a second longitudinal axis. The first and second longitudinal axes are arranged in an angle to each other. One of the first or second holes is advantageously disposed with an attachment portion. According to an embodiment, the surface of the passage can include a roughened portion or a threaded portion. The attachment portion may form an anchoring portion for an interference screw. An interference screw can be used to fix the ligament in the scaphoid prosthesis and/or the lunate to increase stability.
According to an embodiment, the scaphoid prosthesis can comprise protruding portions having a roughly spherical or ellipsoid shape twisted about the longitudinal axis. In particular, the twisting angle of the first end portion relative to the second end portion can be about 90 degrees.
According to an embodiment, the scaphoid prosthesis comprises a scaphoid model, wherein the scaphoid model is obtainable from patient data and corresponds in its shape substantially with the patient's scaphoid, whereby the scaphoid prosthesis is obtained from the scaphoid model. In other words, the scaphoid prosthesis is created according to this embodiment utilizing a scaphoid model, wherein the scaphoid model is generated utilizing patient scaphoid data, and wherein the shape of the scaphoid model represents the shape of the scaphoid prosthesis. The scaphoid model can represent a replacement scaphoid, such that the shape of the replacement scaphoid has an outer surface forming the surface of the scaphoid prosthesis which has substantially the same shape as the surface of the patient's scaphoid. In particular, the scaphoid model is designed by a computer aided design software using the patient data for calculating a shape of a replacement scaphoid of the shape of the patient's scaphoid. The shape of the replacement scaphoid can have an outer surface forming the surface of the scaphoid prosthesis which has substantially the same shape as the surface of the patient's scaphoid. Thereby a patient specific scaphoid prosthesis is obtainable.
The scaphoid prosthesis according to any of the preceding embodiments is made from a biocompatible material suitable for permanent reception in a human body. Preferably, the scaphoid prosthesis is made from a biocompatible material. The material can comprise at least one element from the group consisting of titanium, a biocompatible plastic or a polymer, such as a polyetheretherketone or a ceramic material, for instance a ceramic material containing zirconia.
According to an embodiment, an opening is provided in the scaphoid prosthesis for a fixation means for fixing the scaphoid prosthesis in its position.
The scaphoid prosthesis can comprise a supporting structure extending between the passage and the body surface. The supporting structure can comprise at least one element from the group grids, webs, porous structures, fibers. The supporting structure can be filled by a filler material. The supporting structure can provide the required mechanical stability, whereas the filler material can comprise any biocompatible material such as the materials previously mentioned. The body surface may be formed by a skin, such that the supporting structure is shielded from the environment.
The scaphoid prosthesis according to any of the preceding embodiments can be obtainable by an additive manufacturing method.
In particular, a method for manufacturing a scaphoid prosthesis can comprise an additive manufacturing step. Furthermore the method for manufacturing a scaphoid prosthesis can comprise a first step to obtain data relating to the shape of a patient's scaphoid, in a second step a scaphoid model is generated by a computer aided design software, wherein the scaphoid model which is generated from patient data, corresponds in its shape substantially with the patient's scaphoid, whereby the scaphoid prosthesis can be obtained from the scaphoid model in a third step by the additive manufacturing method.
A method for manufacturing a scaphoid prosthesis according to any of the previously mentioned embodiments can comprise a shaping or forming process starting from a raw material or an intermediate product. In particular, the scaphoid prosthesis is formed from a tubular element comprising a plurality of ribbon-shaped elements, whereby the outer shape of the scaphoid prosthesis is shaped by moving the first end portion towards the second end portion such that a roughly spherical or ellipsoidical shape is obtained, whereby the first end portion is twisted relative to the second end portion such that a scaphoid shape is obtained which corresponds roughly to the surface of the patient's scaphoid.
An aspect of the disclosure relates to a method for manufacturing a scaphoid prosthesis comprising a body bounded by an outer surface, wherein the outer surface is substantially corresponding to a patient's scaphoid, wherein the body of the scaphoid prosthesis comprises a tubular base element including a first end portion and a second end portion and a plurality of protruding portions wherein a single passage is provided in the tubular base element configured to engage a fixation means for fixing the scaphoid prosthesis in its position, wherein the passage is configured as a curved passage, the method comprising an additive manufacturing step.
In one embodiment, the method comprising, by a computing device, receiving data relating to the shape of a patient's scaphoid and generating a scaphoid model, wherein the shape of the scaphoid model corresponds to the shape of the patient's scaphoid.
In one embodiment, the method comprising, by a computing device, generating a scaphoid model utilizing data relating to the shape of a patient's scaphoid.
The invention will be explained in more detail in the following with reference to the drawings obtained from [3]/[4].
The development of the arthrosis follows a defined process and results finally in a collapse of the biomechanical important carpal alignment, which will finally lead to a complete arthrosis of the wrist.
Surgical treatment of the scaphoid pseudoarthrosis according to the prior art consists of a resection of the pseudoarthrosis and reconstruction of the scaphoid using a non-vascularized bone graft (i.e. from the iliac crest).
In cases of a vascularity of the proximal pole a local vascularized bone graft 25 is used (
Alternatively a free vascularized bone graft 40 can be used taken from another location in the body, such as e.g. from the medial femoral condyle as shown in
If these techniques do not lead to healing of the scaphoid bone, a partial fusion would be the next step as shown in
If the capitate head and the lunate fossa of the distal radius is still in good condition and covered by cartilage, a proximal row carpectomy (PRC) can be performed alternatively as shown in
The surgical salvage procedure in the final stage of arthrosis, (complete radio- and midcarpal arthrosis) is the complete fusion of the wrist.
The passage 110 is in
In
The tubular base element has a longitudinal axis substantially corresponding to the passage 110 in the body of the scaphoid prosthesis 100. The longitudinal axis substantially extends from the first end portion 104 to the second end portion 106. The protruding portions 107, 108, 109 have a roughly spherical or ellipsoid shape twisted about the longitudinal axis, whereby the twisting angle of the first end portion relative to the second end portion is about 90 degrees.
The scaphoid model is generated from patient data and corresponds in its shape substantially with the patient's scaphoid, whereby the scaphoid prosthesis is obtained from the scaphoid model.
The scaphoid model can be designed by a computer aided design software using the anonymized patient data for calculating a shape of a replacement scaphoid of the shape of the patient's scaphoid. The shape of the replacement scaphoid can have an outer surface forming the surface of the scaphoid prosthesis, which has substantially the same shape as the surface of the patient's scaphoid. In particular, the scaphoid prosthesis can be made from a biocompatible material. The scaphoid prosthesis can be made from one of titanium, a plastic or a ceramic material. The plastic can be a biocompatible plastic. The biocompatible plastic can be made of a polymer.
By way of an example, the manufacture of a scaphoid prosthesis will be explained in the subsequent paragraph. An average size of the prosthesis was evaluated by measuring 9 scaphoids of anonymized computed tomography patient data by making use of the Geomagic Freeform® application resulting in the scaphoid prosthesis according to
According to an alternative embodiment shown in
A passage 110 can be provided in the scaphoid prosthesis for a fixation means for fixing the scaphoid prosthesis 100 in its position. The passage 110 extends from the first end portion 104 to the second end portion 106.
A tendon strip 125 is threaded through the passage 110 and connected to itself after being passed through a dorsal radio-carpal ligament 115 as shown in
The suspension is carried out through the passage 110 in the prosthesis using a tendon strip of the Flexor Carpi Radialis tendon (FCR) 125. A modified scapholunate ligament reconstruction technique is shown in
Alternatively, a minimal invasive and modified technique is shown also in
An aspect of the disclosure relates to a method for manufacturing a scaphoid prosthesis comprising a body bounded by an outer surface, wherein the outer surface is substantially corresponding to a patient's scaphoid, wherein the body of the scaphoid prosthesis comprises a tubular base element including a first end portion and a second end portion and a plurality of protruding portions wherein a single passage is provided in the tubular base element configured to engage a fixation means for fixing the scaphoid prosthesis in its position, wherein the passage is configured as a curved passage, the method comprising an additive manufacturing step.
In one embodiment, the method comprising, by a computing device 200 such as shown in
In one embodiment, the method comprising, by a computing device 200, generating a scaphoid model utilizing data relating to the shape of a patient's scaphoid.
A method for manufacturing a scaphoid prosthesis according to any of the preceding embodiments comprises an additive manufacturing step. In one step of the method, data are obtained relating to the shape of a patient's scaphoid. In one step of the method, a scaphoid model can be generated by a computer aided design software. The scaphoid model can be generated from patient data. Advantageously, the scaphoid model can correspond in its shape substantially with the patient's scaphoid. In one step of the method, the scaphoid prosthesis can be obtained from the scaphoid model by the additive manufacturing method.
A method for manufacturing a scaphoid prosthesis according to any of the preceding embodiments, wherein the scaphoid prosthesis is formed from a tubular element comprising a plurality of ribbon-shaped elements, whereby the outer shape of the scaphoid prosthesis is shaped by moving the first end portion towards the second end portion such that a roughly spherical or ellipsoidical shape is obtained, whereby the first end portion is twisted relative to the second end portion such that a scaphoid shape is obtained which corresponds roughly to the surface of the patient's scaphoid.
The computing device 200 can be any device, such as a personal computer, lap top, an electronic reader, or the like, configured to receive data relating to the shape of a patient's scaphoid and/or configured to generate a scaphoid model. Data can be information related to a patient's scaphoid, such as size, dimensions, angles, protrusions, shape, or the like.
The computing device 200 as shown in
The computing device 200 can have storage 204, such as, one or more storage mediums including a hard-drive, solid state drive, flash memory, permanent memory such as ROM, any other suitable type of storage component, or any combination thereof. Storage 204 can store, for example, media data (e.g., audio or video files), application data (e.g., for implementing functions on the computing device 200), firmware, data relating to the shape of a patient's scaphoid and/or scaphoid model, and any other suitable data or any combination thereof.
The computing device 200 can have a memory 206, such as a cache memory, a semi-permanent memory, such as a RAM, and/or one or more different types of memory used for temporarily storing data. In some embodiments, the memory 206 can also be used for storing data used to operate computing device applications, or any other type of data that can be stored in the storage 204. In some embodiments, the memory 206 and the storage 204 can be combined as a single storage medium. In some embodiments, the memory 206 and the storage 204 are coupled to the processor 202.
The computing device 200 can have a user interface 208 configured to receive instructions, e.g. from a user, by way of a keyboard, keypad, touch pad, microphone, movement sensor, gesture sensor, camera, or the like. The user interface 208 can have a display/monitor of any type (LED, LCD, OLED, Plasma, CRT, or the like) and/or sound generators, such as speakers.
The computing device 200 can have communications circuitry 210, for example, any suitable communications circuitry 210 configured to connect to a communications network and to transmit communications (e.g., voice or data) from computing device 200 to other electronic devices. The communication circuitry 210 can have receivers and/or transmitters. The receivers can be configured to receive instructions from a device and thus allows a user to enter instructions into the computing device 200. The transmitters can be configured to transmit instructions from the computing device 200 and thus allow a user to send instructions from the computing device 200 to another device, such as a device used in an additive manufacturing method. The receivers and/or transmitters, and the computing device 200 corresponding thereto, can be configured to communicate over a wired connection or over a wireless connection, such as via Ethernet, LAN, WAN, Bluetooth, WiFi, IR communication, a cloud environment, or the like.
It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the scope of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of an element or compound selected from the group consisting of A, B, C . . . and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.
Number | Date | Country | Kind |
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15195745.3 | Nov 2015 | EP | regional |