The present invention relates to a prosthesis for repairing radial head bone in an arm elbow joint with impaired originality due to fracture or osteoarthritis. Background of the Invention

The radius is one of the bones in the forearm. The radius is located in the lateral (on the thumb side) part of the forearm according to the anatomical posture. It articulates with the humerus at the elbow, whereas it articulates with the scaphoid bone and the lunatum bone at the wrist. It is the movable bone of the two bones in the forearm and helps the forearm rotate around its own axis. This bone is frequently broken as a result of falling on the hand, i.e. indirectly. There are prostheses currently in use for fixing the said fracture, however these prostheses cannot protect the cartilage tissue in case of facing with any load while repairing a bone fracture and they lead to new damages as a result of pressure. Therefore, there is need for a novel radial head prosthesis which does not lead to a new damage in the body during use thereof.

The International patent document no. W02006048520, an application in the state of the art, discloses a radial head prosthesis. The prosthesis consists of an anchoring rod, an insert and a radial head. The radial head comprises an anatomical concave cavity on its upper part. The anchoring rod and the insert are combined, whereas the insert and the radial head are combined with one another by means of the studs and hollow pieces. The prosthesis has a modular structure consisting of three pieces. The said invention can be used in patients suffering from osteoporosis and broken bones. The United States patent document no. US6709459, another application in the state of the art, discloses a radial head prosthesis which is used in a patient’s elbow joint and can mimic anatomical movements. The prosthesis comprises a head, a curved stem (body), a connecting member providing the connection between the head and the curved stem. The head part is formed by a recess and the recess is concave in shape. The curved stem is made of a material such as cobalt- chrome or titanium and its surface is roughened. The surface of the connecting member can be coated with a material such as titanium, cobalt-chrome beads, or hydroxyapatite. Besides, the head part and particularly the proximal surfaces of the recess are made of a highly polished cobalt chrome or a ceramic material.

The International patent document no. W02013026676, another application in the state of the art, discloses a prosthesis. The prosthesis basically consists of a joint head member and a stem part. The joint head member comprises a first head component and a second head component. In addition, a telescopic mechanism is located between the first head component and the second head component. The telescopic mechanism is used for adjusting the relative longitudinal positioning of the first head component according to the second head component. After determining the suitable height for the prosthesis, a desired height is maintained by means of a fixing screw.

Summary of the Invention

An objective of the present invention is to realize a prosthesis for repairing radial head bone in an arm elbow joint with impaired originality due to fracture or osteoarthritis.

Another objective of the present invention is to realize a prosthesis for eliminating the possibility of an additional injury to occur by avoiding a pressure to be applied to the arm while healing a radial head fracture, by means of its telescopic motion capability.

Detailed Description of the Invention

“Radial Head Prosthesis” realized to fulfil the objective of the present invention is shown in the figure attached, in which:

Figure 1 is top, bottom and side perspective views of the body among the inventive prosthesis parts.

Figure 2 is top, bottom and side perspective views of the closing member among the inventive prosthesis parts.

Figure 3 is top, bottom and side perspective views of the connecting member among the inventive prosthesis parts. Figure 4 is a sectional view wherein all modular pieces of the inventive prosthesis are mounted.

The components illustrated in the figure are individually numbered, where the numbers refer to the following:

1. Radial head prosthesis

2. Stem

3. Spring

4. Housing

5. Body

6. Connecting member

7. Cylindrical member

8. Cavity

9. Closing member The inventive radial head prosthesis (1) for repairing radial head bone in an arm elbow joint with impaired originality due to fracture or osteoarthritis and having a modular structure comprises:

- at least one body (5) which has at least one stem (2) that enables fixation to the bone marrow, at least one spring (3) that is located on the end part of the stem (2) and provided in the form of a hollow open-ended cylinder used for creating a telescopic motion, and at least one housing (4) that is located on the part where the stem (2) combines with the spring (3);

- at least one connecting member (6) which is inserted into the housing (4) that it located on the body (5) from one end thereof; and

- at least one closing member (9) wherein the end of the connecting member (6) that is not connected to the housing (4) enters the small one compared to the other one, which has two hollow cylindrical members (7) that have two different diameters with the same embedded centers and one open end, wherein at least one cavity (8) is included on the outer surface of the one with a large diameter among the cylindrical members (7) that are located on the closed end, and surrounds the spring (3) upon the connecting member (6) fits into the small-diameter cylinder member (7).

The body (5) included in the inventive radial head prosthesis (1) is a structure made of a single piece comprising the stem (2), the spring (3) and the housing (4). The stem (2) included in the body (5) has a size and shape suitable to be inserted into the radial bone marrow in a thickness and shape specifically for the patient by considering the patient anatomy, and it is inserted into the radial bone marrow. In addition, the stem (2) is made of a porous structure similar to a spongiform bone structure for enabling strong adherence and fusion to the bone upon being inserted into the bone marrow. In another preferred embodiment, surface roughening and hydroxyapatite coating and similar methods are applied to the stem (2) in order to enhance adherence to the bone. Thereby, it is ensured to avoid complication of prosthesis loosening by reducing the possibility of loosening within the bone marrow. The spring (3) included in the body (5) is responsible for enabling the closing member (9) to move telescopically. In other words, it absorbs undesired impacts and slows down fast movements. Thus, any impact to occur on a repaired radial head bone or formation of a new damage in the arm is avoided. Stiffness, number of spirals, section thickness and similar design properties of the spring (3) are chosen according to the patient and stiffness properties of the cartilage belonging to the age group of the patient to whom it will be applied are considered in the said choice. The housing (4) included in the body (5) creates the opening enabling to place one end of the connecting member (6). In one embodiment of the invention, the body (5) is made in one piece and of titanium metal alloy with flexible structure.

The connecting member (6) included in the inventive radial head prosthesis (1) is in the form of a partial cylinder with two closed ends. Part of the cylinder wall is in the form of a truncated cone (Y) in the connecting member (6). The part (Y) of the connecting member (6) with a truncated cone shape has a size suitable to be mounted upon being fit into the housing (4) included in the body (5). Thus, the connecting member (6) is connected to the housing (4) by means of shrink-fit from one end thereof. The cylinder-shaped part (X) of the connecting member (6) has a size suitable to be fit into the internal clearance of the small-diameter cylinder of the closing member (9). Thus, it is fit into the small-diameter cylinder

(7) of the closing member (9). Thereby, the connecting member (6) enables connection of the body (5) and the closing member (9) with one another. In addition, the connecting member (6) is a piece responsible for the stable telescopic motion realized between the body (5) and the closing member (9). The connecting member (6) is made of a metal that is similar to cobalt-chromium alloy, has a low coefficient of friction, is rigid and abrasion resistant.

In the closing member (9) included in the inventive radial head prosthesis (1), the outer surface of the large-diameter cylinder member (7) has an anatomic cavity

(8) used for articulating with the humerus bone. The diameter of the large- diameter cylinder member (7) of the closing member (9) is larger than the diameter of the spring (3) for covering the spring (3) such that it will be enclosed entirely while inserting the closing member (9) into the body (5). Meanwhile, the small-dimension cylinder member (7) of the closing member (9) is fit into the connecting member (6) inserted into the housing (4) that is located in the center of the body (5). The closing member (9) is made of a metal that is similar to cobalt- chromium alloy, has a low coefficient of friction and is abrasion resistant.

The inventive radial head prosthesis (1) consists of combining a body (5) having a modular structure, the closing member (9) and the connecting member (6). The stem (2) located in the body (5) part of the prosthesis (1) is produced together with the spring (3) part integrally from a single-piece metal block by means of CNC processing and the number of pieces included in the prosthesis (1) is reduced. In this way, it is aimed to reduce the metal debris arising from moving parts in a radial head prosthesis (1) and to extend the wear life. Also, it is ensured that the minimum force required for the concentric motion of the spring (3) is just below the maximum elastic compression strength of the cartilage by adjusting the physical, design and alloy properties of the spring (3) in the body (5). Thus, it is ensured that when a radial head prosthesis (1) is under a compressive load in a patient’s body, the articular cartilage being in contact with it is prevented from being damaged.

The inventive radial head prosthesis (1) is produced by means of a patient-specific design. For this purpose, it is ensured that a body (5) and a closing member (9) of a radial head prosthesis (1) are modified such that they will meet the need of a patient optimally by processing a 3D anatomy of a patient -that is obtained by means of radiological imaging of both diseased and healthy arm- in a CAD program. Prostheses are produced specifically for the patient for whom the order was given by a doctor or a hospital, by using Industry 4.0 applications in the production process of the components composing a radial head prosthesis (1) and thereby, these are delivered to the hospital and the doctor who will use them shortly after the order. It is ensured to deliver radiological and clinical information required for production of a patient-specific radial head prosthesis (1) to a design center over via Internet. Design activities are completed for the production step upon modifications of the radial head prosthesis (1) are carried out by a qualified team in a design center specifically for the patient’s need. Then, the 3D computer- aided design file of the radial head prosthesis (1) design specific for the patient is sent to production facilities via Internet. A patient-specific radial head prosthesis (1) is produced by the staff at a production center by using computer-aided production techniques (3D printers, CNC, milling, lathe, etc.) and delivered to the related hospital and/or doctor so as to be used in surgery. Due to this production strategy, it is ensured to produce and apply an ideal radial head prosthesis (1) required for a patient’s treatment within a reasonable waiting period. It is aimed that the said period will not exceed 24 hours by means of the production centers established. In addition, it is possible to eliminate cost-increasing effects such as stocking and storage by means of the said production. Therefore, a cost-effective production of the said radial head prosthesis (1) having patient-specific ideal characteristics is possible and the profitability demanded for production can be ensured.

Within these basic concepts; it is possible to develop various embodiments of the inventive radial head prosthesis (1); the invention cannot be limited to examples disclosed herein and it is essentially according to claims.