RU212481U1 - Implant for fixation of the hip exoprosthesis - Google Patents

Abstract

The utility model relates to the field of limb prosthetics, namely to devices that perform the functions of fixing exoprostheses to the human body. The technical result of the utility model is to ensure the mechanical stability of the implant of the osteointegrative system for hip exoprosthesis while reducing the risk of peri-implant fractures. The result is achieved due to the fact that the implant for fixing the hip exoprosthesis contains intraosseous and percutaneous parts and a connecting screw. The intraosseous part is made in the form of an osseointegrable screw having a central blind channel starting openly from the distal end of the rod for reciprocal connection with the percutaneous part. A honeycomb structure is made between the threads of the osseointegrated screw. The percutaneous part is made with a distal part for connection with a femoral exoprosthesis, and a proximal end for an osseointegrated screw. The connection of the osseointegrated screw with the percutaneous part is fixed with the help of a connecting screw inserted into the central channel of the percutaneous part from its distal part.

Description

The utility model relates to the field of lower limb prosthetics, namely to devices for fixing exoprostheses to the human body.

Limb exoprosthesis using osseointegration is a relatively new technology that is gaining popularity. Its main idea is to use internal fixation of the exoprosthesis components to the residual bones of the stump using a specialized implant that is connected to the external module of the exoprosthesis outside the human body.

Such a device occupies an important place in the osseointegrative system of hip exoprosthesis and performs the function of a mechanical connection between the exoprosthesis and the human body.

The clinical success of this type of prosthetics largely depends on the biomechanical stability, which consists of the primary stability and osseointegration of the implant.

Primary stability is a condition that determines the mechanically immobile state of the implant in the patient's bone tissues after surgery and until the moment of osseointegration.

The fulfillment of this condition is necessary to create a strong connection between the bone and the implant (osseointegration). It is believed that small movements between the implant and the bone can cause the formation of a fibrous layer around the implant, which will lead to biomechanical instability and the need for revision of the implant.

Therefore, after the operation, the implant must be firmly fixed in the bone, eliminating the possibility of micromovement.

If the condition of primary stability is observed, after about 3-6 months, a strong mechanical bond is formed between the bone and the surface of the implant (osseointegration).

Osseointegration during the operation of the implant is vulnerable to cyclic fatigue and impact loads due to the large difference in the physical and mechanical characteristics of the bone and titanium implant. This is due to the fact that in the section (at the border) of titanium and bone, the stress values reach a maximum, which can lead to periprosthetic fractures and instability.

To reduce stresses in the bone-implant interface, the surface area of osseointegration is increased in various implants in various ways.

Known "Percutaneous prosthesis" [RU2288673C2], containing the first component, profiled for implantation into the bone, and the second component, designed to be placed between the bone and the skin, and the second component is subjected to surface treatment to stimulate the proliferation of fibroblast cells and attachment of epithelial cells, and the third the component is designed to be placed outside the skin surface and has a low surface energy that keeps bacteria from adhering.

The disadvantage of this device is that it does not have a thread to ensure full primary stability of the implant after surgery. Insufficient primary stability may allow micromovement of the implant during human life. The presence of micromotion can lead to the development of fibrous fixation of the implant or instability of the osseointegrated component, which can lead to failure of the implanted structure.

Known "Ostoeointegrable limb prosthesis" [RU186732U1], containing an osseointegrable prosthesis, made in the form of a cylindrical part with a perforated flange in the middle part, where transverse through holes with internal thread are made on the introductory part, and a groove is made on the end of the tail part, which makes it possible to provide the possibility loading of the prosthesis immediately after the operation.

The disadvantage of this device is the need to install screws that block the intramedullary implant, which increases the risk of periprosthetic (reimplant) fractures, and also complicates the technique and increases the time of the operation.

The closest technical solution adopted for the prototype is the "Anchoring system for attaching a prosthesis to a human body" US20190254782A1], containing: anchor element, abutment, abutment screw connecting the abutment and anchor element. The abutment connects to the anchor with a conical interference fit and has an anti-rotation element at the proximal end.

The disadvantage of this device is the lack of a three-dimensional cellular structure similar to cancellous bone to improve the reliability of osseointegration.

The task is to develop a device for reliable fixation of the endoprosthesis to the human body with primary and secondary stability, devoid of the above disadvantages.

To solve this problem, studies were carried out that showed that the simultaneous finding of a volumetric cellular structure and a thread provides more reliable mechanical stability of the implant than separately.

Also, computer finite element modeling of the bone-implant system with three screws with different thread pitch (3.5, 5.25 and 7 mm) and, accordingly, with a different ratio of thread and cellular structure was carried out. The aim of the study was to determine the most optimal ratio of thread and cellular structure to ensure the primary and secondary stability of the screw. From the conducted studies, it was found that the most optimal ratio of thread and cellular structures is a screw with a thread pitch of 7 mm, since it had the lowest stresses in the bone-implant system.

The technical result of the utility model is to ensure the primary and secondary stability of the implant while reducing the risk of peri-implant fractures.

The result is achieved due to the fact that the intraosseous part of the device is made in the form of an osseointegrable screw having a central blind channel starting openly from the distal end of the rod for reciprocal connection with the percutaneous part, and a cellular structure is made between the threads of the osseointegrable screw, while the percutaneous part is made with the distal part for connection with the femoral exoprosthesis, and the proximal end - for the osseointegrated screw, and the connection of the osseointegrated screw with the percutaneous part is fixed by means of a connecting screw inserted into the central channel of the percutaneous part from the side of its distal part.

It is possible to make a thread with a pitch of 7 mm.

It is possible to build a cellular structure based on a dodecahedron with an edge diameter of 0.6 mm.

It is possible to perform a cellular structure with a thickness of 2 mm.

A thread height of 1.5 mm is possible.

The essence of the utility model is illustrated by the following drawings:

in fig. 1 shows a general view of a device for fixing a femoral exoprosthesis to a human femoral stump;

in fig. 2 shows an enlarged view of an osseointegrated screw with a transparent honeycomb structure.

in fig. 3 shows a section of a device for fixing a femoral exoprosthesis to a human femoral stump;

in fig. 4 shows the junction of the abutment and the osseointegrated screw;

in fig. 5 shows a view of the implanted device in the medullary canal of the femur of the stump of the lower limb with transparent soft and bone tissues.

The device is made of a bioinert material and consists of an osseointegrated screw 1 (intraosseous part of the device), abutment 2 (percutaneous part of the device) and a connecting screw 3 (Fig. 1-5).

The shaft (body) of the osseointegrated screw 1 is made with a taper in the proximal direction (towards its end) of 1 degree, and a thread 6 with a pitch of 7 mm is made on its outer surface. The thread height 6 is 1.5 mm.

The screw 1 has a central blind channel 9 starting openly from the distal end of the rod for connection with the abutment 2. Communication channels 5 are open in the central channel 9 of the screw 1. A cellular structure 7 is made between the threads 6 of the screw 1. The cellular structure 7 is built on the basis of a dodecahedron with rib diameter 0.6 mm.

Abutment 2 is intended for connection of osseointegrable screw 1 and hip exoprosthesis. Moreover, the distal part 8 of the abutment 2 is intended for connection with the femoral exoprosthesis, and its 2 proximal end — with the osseointegrated screw 1. The outer surface of the abutment in contact with soft tissues has a polished surface.

The proximal end of the abutment 2 is made in the form of a cone - a hexagon for connection with an osseointegrable screw 1. Accordingly, the central channel 9 of the screw 1 in the distal part has a counterpart for connection with the abutment 2. This connection provides a tight tight fit, torsion blocking and is fixed with a connecting screw 4 inserted into the central channel of the abutment 2 from the side of its 2nd distal part 8.

Behind the said mating part for connection with the abutment 2, the central channel 9 of the screw 1 is sealed with a threaded plug 3, for which it has a 9 reciprocal thread.

The device works as follows.

Using a standard lateral access, an incision is made along the outer side of the femoral stump with a transition to the inner one. Soft tissues are separated in layers to open access to the femur. In the intramedullary canal of the femur, a thread is cut corresponding to the thread 6 of the osseointegrated screw 1. The osseointegrated screw 1 is screwed into the intramedullary canal. The contents of the intramedullary canal are brought into the central canal 9 of the osseointegrated screw 1 with the help of an introducer. The contents of the mentioned channel fills the cellular structure 7 through communication channels 5. Next, a plug 3 is installed, sealing the central channel 9. After that, an abutment 2 is installed in the osseointegrable screw 1 and fixed on it 1 using a connecting screw 4. Next, the surgical field is processed, followed by compliance with transcutaneous interface processing protocol. The final view of the implant is shown in Fig. 5.

After completing the rehabilitation course, a hip exoprosthesis is attached to the distal part 8 of the abutment 2. After that, the patient can walk with support on the exoprosthesis with a full load.

Claims (5)

1. An implant for fixing a hip exoprosthesis, containing an intraosseous and percutaneous parts and a connecting screw, characterized in that the intraosseous part is made in the form of an osseointegrable screw having a central blind channel starting openly from the distal end of the rod for reciprocal connection with the percutaneous part, moreover, between the coils The thread of the osseointegrable screw is made of a cellular structure, while the percutaneous part is made with the distal part for connection with the femoral exoprosthesis, and the proximal end is for the osseointegrated screw, and the connection of the osseointegrable screw with the percutaneous part is fixed by means of a connecting screw inserted into the central channel of the percutaneous part from the side its distal part. 2. The implant according to claim 1, characterized in that the thread is made with a pitch of 7 mm. 3. The implant according to claim 1, characterized in that the cellular structure is built on the basis of a dodecahedron with an edge diameter of 0.6 mm. 4. The implant according to claim 1, characterized in that the thickness of the honeycomb structure is 2 mm. 5. The implant according to claim 1, characterized in that the height of the thread is 1.5 mm.

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