Hybrid actuation dynamic intramedullary nail and dynamic intramedullary nail set with magnetic actuator

Abstract

The subject of the present invention is a dynamic intramedullary nail with a hybrid drive, comprising a casing with a proximal segment and a distal segment, said casing containing therein a magnetic rotor driven by an external magnetic field and an internal spring element which stores potential energy during assembly and constitutes a drive means for telescopically extending the nail.

Description

[Technical field]

[0001] The subject of the present invention is a variable length intramedullary nail driven by a hybrid drive system. The implant allows the correction of the length of the bone to be repaired. By lengthening or shortening the nail, the rate of bone growth and repair can be controlled. The hybrid drive used in the implant allows the forces required during extension to be realized and allows full control of the nail length using an external device. [Background technology]

[0002] One of the ways to solve problems related to limb imbalance is to surgically lengthen the limb. Lengthening limbs with external stabilizers is cumbersome and dangerous for the patient due to the large size of the limb and the high chance of infection and other complications. By using an internal mechanism, the intramedullary nail, the healing process proceeds painlessly and the internal implant does not interfere with the patient's daily functions. Furthermore, the risk of wound infection is significantly lower.

[0003] Existing solutions for dynamic intramedullary nails are characterized by a single energy source that drives the elements of the implant. Dynamic intramedullary nails with hybrid drive use mechanical energy stored in elastic elements inside the implant in synchronous with magnetic energy generated from the outside. The magnetic drive allows energy to be introduced into the device from an external actuator through the patient's tissue. The magnetic energy is converted into mechanical energy that moves a mechanism within the implant. At the same time, the mechanical energy stored in elastic elements with specific properties supports the movement of the implant during the lengthening process. The forces generated by the elastic elements compensate the mechanical interactions occurring in the soft tissues (muscles, tendons, skin) and mitigate the magnetic drive.

[0004] The combination of two types of actuators allows to control the elongation process during healing and to minimize the amount of energy generated outside the patient's body and passing through it. It also allows to minimize the size of the magnetic actuator inside the implant, improving the compactness and mechanical strength of the structure. The strength of the magnetic field generated by the external element that drives the nail mechanism is limited to an absolute minimum.

[0005] From the Polish patent specification PL162850B1, a bone repair device is known, which is intended to longitudinally correct and laterally correct the bone being repaired with play within defined limits. The device has fixed and movable jaws connected by a bolt. The jaws have a guide channel and an elliptical opening for mounting a bone implant. The channel and the opening are perpendicular to a plane passing through the longitudinal axis of the cylindrical guide.

[0006] According to the Polish patent specification PL226930B1, an expandable intramedullary nail for bone lengthening with a piezoelectric mechanism is known for bone lengthening with a lengthening mechanism based on a piezoelectric actuator. The nail consists of a central body, an upper body with a transverse opening and a longitudinal opening, a bellows attached to the flat surface of the lower slot and a pin on which the piezoelectric mechanism is located. Meanwhile, the central body has upper and lower slots with an outwardly extendable ratchet element introduced into the groove of the central body, the ratchet element being based on a spring element with an opening and 12 openings around the entire circumference.

[0007] According to the Polish patent specification PL237952B1, a dynamic intramedullary nail is known that allows angular correction driven by an external magnetic field, the structure of which includes a rotating ring with an inclined front face, the rotation of which allows bending the nail and possibly changing the angular orientation of the end of the bone to be repaired. The nail structure is based on a telescopic extension mechanism with the function of independently rotating one end of the nail and bending the nail. The drive of the nail extension and bending mechanism is constituted by a magnetic transducer placed in the middle part of the nail. Under the influence of an external magnetic field, the magnetic transducer rotates and drives both nail mechanisms independently.

[0008] A device for lengthening long bones is known from patent specification US5961553B, which comprises a lengthening mechanism based on an electric motor which rotates a guide screw of a linear actuator. The electric motor is connected to the guide screw via a reduction gear. The part of the implant consisting of a rope drive and a piston is attached to the bone. Based on the measurement of the number of turns of the guide screw the lengthening value is determined. The system for measuring the number of turns of the guide screw also identifies the direction of rotation.

[0009] According to patent specification US5415660, an implantable limb extension nail driven by a shape memory alloy is known, the extension mechanism of which is based on a shape memory alloy and a ratchet assembly. The implant consists of two telescopic cylinders connected to the bone. The alloy element moves a rod with an edge adapted to engage with the hook of the ratchet assembly. The edge has a shelf-like shape that narrows gradually in one direction. This allows the movement of the rod in only one direction.

[0010] Patent specification US5976138B describes a known traction system for long bones, which displaces the central fragment of a bone divided into three fragments (proximal, middle, distal). The proximal and distal fragments are connected to the casing of an implant, the middle fragment being displaceable. The implant is equipped with a linear actuator based on an internal drive which rotates a guide screw. The implant is fixed to the bone fragments by means of a screw.

[0011] The implant known from patent specification US2014 / 0236311A1 is in the form of a linear actuator, two elements of which are attached to two bone fragments. The implant replaces the removed bone fragments. The drive consists of a piezoelectric motor connected to a gear which drives a guide screw. The rotational movement of the guide screw is converted into a linear movement of the shaft by a longitudinal groove and a screw which is arranged in the casing and enters into a groove. The drive is inductively powered by an external source. [Brief description of the drawings]

[0012] The object of the invention is illustrated in more detail in the drawings, in which FIG. 1 shows a schematic diagram of the construction of a dynamic intramedullary nail with a hybrid drive.

[0013] FIG. 2 shows an intramedullary nail with a hybrid drive and an external actuator and the effect of a magnetic field. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The essence of the dynamic intramedullary nail with hybrid drive according to the invention is that it has a structure based on a telescopic mechanism that allows the implant to be lengthened or shortened.

[0015] The dynamic intramedullary nail (implant) is composed of a skeleton (shell) and a drive inside the shell. The skeleton of the nail is composed of a proximal segment (1) with a first end and a second end for attachment to the bone, and a distal segment (2) with a first end and a second end for attachment to the bone. The second ends of both members are connected telescopically. The hybrid drive of the nail extension mechanism is composed of a magnetic rotor (3) and a spring element (4) located in the center of the nail, which operate simultaneously. Under the action of an external magnetic field generated by an external actuator (7), the magnetic rotor (3) rotates and drives a mechanical gear (5). The mechanical gear (5) drives a drive screw (6) which pushes the nail out of the distal segment (2), thereby extending the nail. The actuator (7) may have various structures. For example, it can be based on an electromagnet with a variable magnetic field or it can use a rotating permanent magnet. The actuator (7) is a separate structure. In order to rotate the magnetic rotor, it is important to be able to generate a variable magnetic field.

[0016] The design of the dynamic intramedullary nail with hybrid drive allows the drive to simultaneously use forces generated from a spring element enclosed within the implant and forces generated from an external energy source via a magnetic field.

[0017] The dynamic intramedullary nail contains a permanent magnet, the magnetic rotor (3), which is moved by magnetic engagement with an external actuator (7). The movement of the magnetic rotor (3) through the additional elements of the drive system, the mechanical gear (5) and the drive screw (6), adjusts the extension and contraction of the implant elements, changing the length of the implant. The direction of movement of the external actuator (7) determines the extension or contraction of the implant length. The mechanical gear (5) comprises three gear assemblies, each consisting of three gears in planetary rotational motion with respect to a central gear. The rotation of the shackle to which the planetary gears are attached drives the central gear of the next gear set. The last shackle drives the drive screw. Inside the hybrid drive intramedullary nail there is also a spring element (4), which deforms during assembly (nail manufacturing process) and whose stored potential energy supports the nail extension motion. The spring element (4) can be selected from, for example, a coil spring, a spiral spring, a sheet spring, and a gas spring. The essence of the spring element is to store potential energy. The force generated by the spring element (4) reduces the reaction of the limb's soft tissues and increases the efficiency of the implant. A magnetic system with an external magnetic actuator (7) and an internal magnetic rotor (3) allows the nail's extension direction and extension speed to be controlled. The nail may be used for bone stabilization after trauma or for bone traction after osteotomy.

Claims

1. A dynamic intramedullary nail with a hybrid drive, comprising a casing with a proximal segment (1) and a distal segment (2), the casing containing therein a magnetic rotor (3) driven by an external magnetic field and an internal spring element (4) which stores potential energy during assembly and constitutes a drive means for telescopically extending the nail.

2. 2. The dynamic intramedullary nail with hybrid drive according to claim 1, characterized in that the proximal segment (1) comprises a first end for installation in a bone and a second end.

3. 2. The dynamic intramedullary nail with hybrid drive according to claim 1, characterized in that the distal segment (2) comprises a first end for installation in a bone and a second end.

4. 4. Dynamic intramedullary nail with hybrid drive according to any one of claims 1 to 3, characterized in that the second end of the proximal segment (1) is telescopically connected to the second end of the distal segment (2).

5. 4. The dynamic intramedullary nail with hybrid drive according to any one of claims 1 to 3, characterized in that a drive screw (6) extends from the proximal segment (1) to the distal segment (2), the screw (6) comprising a mechanical gear (5) at a first end and a second end of the screw (6) seated in the second end of the distal segment (2).

6. Dynamic intramedullary nail with hybrid drive according to claim 1, characterized in that the magnetic rotor (3) is actuated by an external magnetic field generated by an external magnetic actuator (7).

7. Dynamic intramedullary nail with hybrid drive according to claim 1 or 5, characterized in that the drive screw (6) passes longitudinally through the spring element (4).

8. 2. Dynamic intramedullary nail with hybrid drive according to claim 1, characterized in that the drive means allows to extend or shorten the length of the intramedullary nail depending on the direction of change of the external magnetic field while simultaneously using the potential energy stored in the internal spring element (4).

9. 2. A dynamic intramedullary nail with hybrid drive according to claim 1, characterized in that it has a magnetic rotor (3) which is actuated by an external magnetic field generated by a magnetic actuator (7) and which is simultaneously transformed into a movement of the nail using an elongation supporting force generated by an element placed inside the implant.

10. Dynamic intramedullary nail with hybrid drive according to claim 1, characterized in that the mechanical gear (5) constitutes a planetary gear set.

11. A set comprising a dynamic intramedullary nail with a hybrid drive according to claim 1 and a magnetic actuator (7) for use in bone traction surgery.

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