EP1135074A1

EP1135074A1 - Device for retaining and protecting damaged bones

Info

Publication number: EP1135074A1
Application number: EP99962167A
Authority: EP
Inventors: Hans Albert Richard; Thomas Beier
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-11-30
Filing date: 1999-11-26
Publication date: 2001-09-26
Also published as: WO2000032124A1; DE19855254B4; DE19855254A1; AU1860300A

Abstract

The invention relates to a device (50) for retaining and protecting damaged bones (1). Said device has two sections (10, 11) which can be fixated at the bone (1) on both sides of the damaged bone (2). Said sections are linked with each other via at least one spring device (20) in such a manner that they can be elastically displaced in an axial relation to each other. The device is further provided with means for varying the spring rate.

Description

Device for the retention and protection of damaged bones

The invention relates to a device for the retention and protection of damaged bones, with two sections fixed to both sides of the bone damage to a bone, which are coupled to one another so as to be able to bridge the bone damage by means of at least one spring device so as to be axially resiliently displaceable.

Damage to bones, i.e. Bone fractures can be treated using two different methods. One method is flexible fixation (e.g. bandage / plaster), which results in natural bone healing. Another method is surgical fracture treatment with a rigid fixation, known as primary bone healing. Such a rigid fixation takes place in that the bone above and below the breaking point by means of screws, pins or the like, with a rigid connecting rod or the like. is connected. This rigid connecting rod can either be used as an external fixator, i.e. a connecting rod located outside the body, as a plate implant or the like, which is screwed directly to the outside of the bone, or can also be designed as an intramedullary nail in tubular bones.

The natural bone healing takes place through the formation of a kailous tissue, which with increasing solidification The mobility of the broken ends is reduced more and more until ultimately stability has been achieved.

Bone healing takes place in three phases.

The first phase is characterized as the cellular callus formation phase (reparative inflammation). Here, a rapid accumulation of cells of mesenchymal (embryonic) origin can be observed around the injured pieces of tissue. This cellular callus develops the basic substance and gradually envelops the fracture site. It is a microscopically visible new bone tissue that forms in response to the bone injury. A prerequisite for the formation of callus between the fragments is, on the one hand, the sufficient proximity of the fragments to one another, and, on the other hand, a certain movement between the fragments.

In the second stage, the connective tissue callus and fixation callus (mineralization phase) are formed. This is based on the accumulation of minerals in the cartilage and bone substance, which was formed by the cells of the first callus phase. The onset of mineralization depends on the mechanical stability which is brought about by the preliminary enrichment of the connective tissue callus. Mechanical stability characterizes the clinical condition of the bony superstructure.

In the third bone healing phase (remodeling), the mineralized tissue that has undergone the fracture is replaced by lamellar bone. The injured bone then returns to its full normal function. At this stage, there is consolidation and remodeling. The above-mentioned primary bone healing with a stable fixation by means of plates, screws or intramedullary nail aims to ensure a quick functional restoration with the most anatomical reconstruction possible. The price for this, however, is the absence of a natural fracture callus formation. This skips the first and second phase of natural bone healing and only normal osteonal remodeling, ie the third phase of natural fracture healing, takes place. However, such direct union without callus formation under stable mechanical conditions is the slower way of bone healing. It is only a quick, functional rehabilitation is achieved.

Another major disadvantage of this stable fixation is the incomplete recovery of the entire load-bearing capacity after the fracture has healed. The bone as a natural organ only rebuilds to the extent necessary to bear the total load together with the implant. It therefore only reaches its original mechanical stability weeks after implant removal. Immediately after implant removal, the bone's load-bearing capacity is also reduced. This is due on the one hand to the weakening of the cross section by the fastening screws, and on the other hand to the injuries caused by the surgical intervention. In order to avoid refraction at this stage, the patient must exercise great caution until the bone has healed completely.

In order to stimulate the bone substance to grow even during an operative fixation of the bone, DE 40 02 400 C2 describes a device of the type mentioned at the beginning in the form of a Intramedullary nail suggested. The nail shown there has two telescoping sections with a spring arrangement in between, which is pretensioned at the beginning of the healing process. The two sections of the intramedullary nail are thus permanently pushed apart by the spring arrangement, ie the bone fragments are subjected to a force that pulls the fragments apart. With an external pressure load on the bone, for example a thigh bone with a load on the leg, when the patient stands on this leg, the spring is compressed minimally. This inevitably leads to certain movements in the axial direction, which stimulates callus formation. The spring can be re-tensioned regularly, so that in patients who have bone defects or bone substance losses of a few millimeters, healing can take place without shortening the bone.

However, such a preloaded spring has the disadvantage that permanent tension is exerted on the bone ends, which is not an advantage for every fracture. In addition, the force-displacement function is unfavorable in the case of such a pretensioned spring as a dynamic element, since the spring only yields to pressure from a certain predetermined minimum force, which depends in each case on the pretension of the spring. At forces above this minimum force, the spring is suddenly relatively soft.

It is an object of the present invention to provide a device of the type mentioned at the outset which does not have these disadvantages and with which there is the possibility of an exact adaptation to the course of healing. This object is achieved in that the device has means for varying the spring constant.

By varying the spring constant of the spring device, the dynamic behavior of the device can be precisely controlled without a spring being preloaded. Regardless of the external force that occurs in each case, the spring has a constant, adjustable "softness".

This spring constant is preferably varied depending on the healing process. That depending on the strength of the bone regained, the spring constant is changed so that the harder the bone itself, the softer the device. This ensures permanent, equally high bending stiffness of the device, so that the bone and in particular the fracture point are protected against transverse forces and torsional forces and refraction is avoided. Only in the axial direction does the device absorb less and less forces, so that the bone can heal completely, as in natural bone healing without an operationally stable fixation, and it already achieves its original mechanical stability with the implant.

The spring constant can be changed either step by step or continuously.

In a particularly preferred embodiment, the two sections are telescopically displaceable, and the spring device is arranged inside the sections and counteracts a compression of the sections. This embodiment is particularly suitable as an intramedullary nail. The sections are preferably secured against rotation relative to one another about their connecting axis and have at least one stop to limit the axial movement of the sections to a maximum length.

There are various options for realizing the spring device.

In various preferred exemplary embodiments, the spring device has at least one working chamber and at least one piston arranged movably therein, and means for changing the pressure and / or the pressure ratios and / or the volume and / or the volume ratios in the working chamber. The spring constant is changed in a simple manner via the pressure or the pressure ratios or the volume changes.

In an alternative preferred exemplary embodiment, the spring device has at least one mechanical spring element and means for changing the effective length of the spring element.

In further preferred exemplary embodiments, the spring device has a plurality of spring elements connected in series and / or in parallel, and means for coupling or uncoupling and / or for blocking the individual spring elements. The spring constant is changed depending on the number of active spring elements.

The device preferably also has an emergency lock which, when the two sections are displaced relative to one another by a certain axial path length, prevents further axial movement of the sections relative to one another. This Emergency locking has the sense that a sudden axial overloading of the bone in the form of pressure on the fracture points, for example as a result of a fall or the like, is prevented. This emergency lock also intervenes if, for example, the spring device fails, for example if for some reason the required pressure is missing in one of the working chambers.

The emergency lock can e.g. be designed such that at least one latching means is arranged on one of the sections, which interacts with at least one corresponding latching means on the respective other section. It preferably has means with which the emergency lock can be released again. When the emergency lock is engaged, the entire device functions in exactly the same way as a conventional, rigid intramedullary nail or fixator.

In a further preferred exemplary embodiment, the device has at least one sensor for measuring at least one parameter, from which the current healing state can be determined alone and / or in conjunction with further parameters. The sensor can be, for example, an ultrasound sensor, which determines the density of the bone substance at the break point. In addition, this can be a temperature sensor that measures statements about the body temperature at and around the break point. An increase in temperature could indicate an infection, for example. Various sensors are available for measuring such parameters as strength, density, viscosity and temperature. An example of the measurement of these parameters by means of a micromembrane based on ultrasound is in the article "Ultrasonic measurements with micromembranes" by MW Börner et al., In the journal "Sensors and Actuators A 46-47 (1995) 62- 65 ". With such sensors, unexpectedly occurring influencing variables, such as infections, circulatory disorders, etc., can be recognized at any time.

Furthermore, the device can have additional force and acceleration sensors with which information about the type of movement and the respective load level can be determined.

In a preferred embodiment, the device has at least one actuator for changing the length of the device between the fixing points, at which the sections on both sides of the bone damage are attached to the bone. A targeted change in the length of the device is possible via this actuator, this change in length taking place independently of the softness of the spring. Such a change in length is of course also possible in that the stop, which serves to limit the axial movement of the sections, is adjusted by the actuator.

Furthermore, the device preferably has at least one actuator for periodically changing the length of the device between the fixing points in the form of micro movements. This movement is also independent of the setting of the spring.

It is of course also possible to use only one actuator for changing the length of the device and for the micro movement and to actuate the desired mechanism via two couplings.

The actuator can be a small electric motor or the like. The actuators can of course also be actuators, which are not electrical, but by Compression spring tension, etc., are driven pneumatically or hydraulically, a certain "energy supply" already being present in the system due to an initially predetermined pressure in a working chamber or by a prestressed spring when the implant is inserted, and in a possibly later healing phase due to the body's own movement this energy storage is recharged.

The actuator can be connected in series with the spring device between the two sections. At the beginning of the healing process, an active micro movement is generated with the actuator to support callus formation. The spring is set in its highest rigidity, so that the bone is almost completely relieved. The micro-movement stimulates the blood circulation, which is conducive to callus formation. This micro-movement can then be dispensed with as the healing process progresses. Instead, the spring is set ever softer, so that more and more stress is transferred to the bone itself. This automatically leads to inevitable, i.e. the body's own micro movements, e.g. when the patient puts pressure on the affected leg. The active length change of the device usually also takes place in the first bone healing phase, but only when the bone has to be pushed apart due to the traumatic loss of bone substance in order to form sufficient callus to compensate for these losses.

In a particularly preferred exemplary embodiment, the device has a controller for determining the current healing state from the measured and / or externally entered parameters. These externally entered parameters can, for example, provide information about further injuries in the The patient's body after a polytrauma, the age and parameters relating to the general physiological condition of the patient, for example his fitness or the like, as well as current mechanical parameters of the respective movement, such as pressure load, speeds, accelerations etc. This control is preferably also used for the automatic variation of the spring constant, for the automatic length change of the device between the fixing points or for the automatic execution of the micro movements. This can be a control in the form of a microchip or the like, which is also possibly arranged in the interior of the device.

The controller is preferably a self-optimizing controller which has a database with a knowledge base and a reasoning mechanism so that the controller can learn, store and use new knowledge while the device is operating. With such a control, the device can react independently to the healing process and special stressful situations. The healing process can thus be optimized.

By using the knowledge base and the own inference mechanism, the control should be able to recognize from the movement of the patient based on the entered data and the continuously measured parameters whether the movement performed is a movement that promotes healing, which of the respective movements corresponds to the current target. The target depends on the phase of bone healing, ie the first phase focuses on optimal retention and protection of the bone as well as full load transfer by the implant. In the second healing phase, the callus formation by the micro movement, and to be promoted either by approved micro-movements of the body or by micro-movements carried out by the actuators. The load transfer through the implant is to be increasingly reduced and the load transferred to the bone. In the third healing phase, the load of the implant should then be completely reduced. Thanks to the intelligence of the system, the movement situations can be analyzed, evaluated and reacted with the help of the information from the knowledge base by adjusting the spring constant accordingly and / or moving the actuators accordingly.

The device preferably also has at least one data transmission interface for the percutaneous transmission of data between the sensor (s) and / or the actuator (s) and the controller or an external controller. These percutaneous transmissions send and receive information wirelessly through the skin. If the device is an internal implant, e.g. an intramedullary nail or a plate implant that does not contain any control inside, the control can thus be outside, e.g. in a device that is strapped to the patient's body and that is constantly connected to the actuators and sensors.

If the device itself contains an internal control, contact with a higher-level external control is possible at any time via such a percutaneous interface, which is available, for example, in the doctor's office, so that the doctor can regularly query data collected in the internal control and is informed about the healing process. Of course, it is also possible for a higher-level control to be located at the patient, for example regularly transmits signals via remote transmission to a further control system at the attending doctor, so that the doctor can monitor the healing process even without the patient being present.

Of course, a device in the form of a plate implant or an intramedullary nail for the voltage supply of the actuators and the sensors as well as a possible control has a built-in battery or the like.

The invention is explained below with reference to the accompanying drawings using exemplary embodiments. They represent:

Fig. 1. is a schematic representation of a broken

Tube of the thigh with a device according to the invention in the form of an intramedullary nail,

2 shows a schematic illustration of the bone according to FIG. 1, but with an inventive device in the form of an external fixator, which is arranged outside the leg,

3 shows a schematic illustration of the bone according to FIG. 1, but with a device according to the invention in the form of an implant attached to the outside of the bone,

4 shows schematic representations of three different to 6b exemplary embodiments of the housing of the device according to the invention,

Fig. 7 shows the load capacity of the bone and

Load of a conventional, rigid implant for a fracture of the lower extremities depending on the healing process,

8 shows a comparative diagram of the load capacity development of the healing bone when using the device according to the invention and in conventional bone healing with a conventional rigid implant, 9 several schematic representations of different to 20 b exemplary embodiments for realizing the spring device according to the invention, FIG. 26

21 a several schematic representations of different to 25 b exemplary embodiments for realizing a

Emergency locking of the device according to the invention.

1 to 3, the device (50, 51, 52) according to the invention is in the form of an intramedullary nail (50), FIG. 1, an external fixator (51), FIG. 2, and an implant (52 ), Fig. 3. The device (50, 51, 52) is used to fix a patient's thigh bone (1) broken at a damaged site (2). Of course, this device according to the invention is not limited to the healing of the femur.

As can be seen from FIGS. 1 to 3, the device (50, 51, 52) each has an upper section (10) which is connected to the upper fragment (4) of the bone (1 ) is connected (proximal locking), and a second lower section (11), which is connected to the lower fragment (3) of the bone with corresponding pins, nails (22) or screws. These two sections (10, 11) are axially resilient against one another in order to bridge the bone damage (2) via at least one spring device (20, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200) slidably coupled together.

4 to 5 show various embodiments of how the two sections (10, 11) can be coupled to one another and at the same time form a housing for the spring device (20). The outer shape of the housing can, for example, correspond to the shape of a conventional intramedullary nail.

In the first embodiment according to FIG. 4, the two sections (10, 11) are two cylinder tubes which form a telescopically displaceable housing in which the spring device (20) is arranged. The lower and the upper tube section (10, 11) are each connected to the bone fragments (3, 4) via the proximal lock (21) and the distal lock (22). Inside the pipe sections

(10, 11) there is a linear ball bearing (23) which guides the lower pipe section (11) in the upper pipe section (10) and ensures the connection of the two pipe sections (10, 11). Between the ball bearing guide (23) and the distal lock

(22) of the lower section (11) is the spring device (20), so that the two sections (10, 11) are coupled together via this spring device (20).

Fig. 5 shows a further embodiment with a one-piece housing, which represents the first section (10). This is firmly screwed to the upper bone fragment (4) at the proximal end via the proximal lock (21). The tube section (10) has elongated holes (24) at the distal end. A pin which forms the distal lock (22) and which is connected to the lower bone fragment (3) runs through these lateral elongated holes (24). The lower section (11) is completely encapsulated in the interior of the upper section (10) and is coupled via the spring device (20) to the upper section (10) or the proximal locking device (21). 6 a shows a further exemplary embodiment with two telescopically displaceable sections (10, 11), in which the two pipe sections (10, 11) are coupled to one another directly, without the interposition of a linear ball bearing, by means of a suitable spring device (20).

Both the embodiment of FIG. 4 and the embodiment of FIG. 6 a have seals (25) at the point at which the two pipe sections (10, 11) are slidably mounted one inside the other in order to separate the interior of the implant (50, 52) from the surroundings. In the exemplary embodiment according to FIG. 5, corresponding seals could be located within the elongated holes (24).

Fig. 6 b shows a section through Fig. 6 a, on which it can be seen that the two sections (10, 11) through a corresponding groove (32) in the upper outer tube section (10) and a matching nose (31) on inner lower tube section (11) are secured against rotation about the axis (30).

9 to 20b different exemplary embodiments for the spring device (20, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200) and the means for varying the spring constant are shown schematically.

In the examples in FIGS. 9 and 10, the spring device (100, 200) has at least one working chamber (101, 201, 202, 203) with at least one piston (110, 210, 211, 212) movably arranged therein and with means to change the pressure or the pressure ratios or the volume and / or the Volume ratios in the working chamber or chambers (101, 201, 202, 203).

In Fig. 9, the spring device (100) consists of two pressure vessels (125, 124), a divided working cylinder (101) with a piston (110) movable therein and four control valves (120 to 123). The piston (110) is sealed off from the walls of the working cylinder (101). The piston (110) divides the space of the working cylinder (101) into two compartments (111, 112), each of these compartments (111, 112) using corresponding valves (120, 121, 122, 123) both with the one pressure vessel ( 124) as well as with the other pressure vessel (125). One of the two containers (125) initially has a relatively high pressure; the other container (124) has a low pressure or may be completely empty. The entire facility works with a body-compatible compressible medium. Depending on the opening of the individual control valves (120 to 123), the pressure in the two subchambers (111, 112) can be set exactly as long as there is a pressure difference between the two containers (125 and 124). By adjusting the pressure in the partial areas (111, 112) of the working cylinder (101), on the one hand, the position of the piston (110) within the working cylinder (101) and thus the overall length of the device can be set, since the piston (110) is inevitable in the position in which the pressure is the same in both sections (111, 112). The piston (110) in the working cylinder (101) thus serves as an actuator for changing the length or for performing micro movements. In addition, the absolute rigidity of the pressure changes the axial rigidity, ie the spring constant of the entire system. The setting of the position of the piston (110) in the working cylinder (101) and the setting of the spring constant are thus independent of one another, since the position of the piston is set by the pressure conditions predetermined from the outside in the two partial areas of the working cylinder (111, 112), whereas the rigidity or spring constant of the system is determined by the absolute pressure. By suitable control of the valves (120 to 123) this system can in principle also be used to increase the pressure in the accumulator (125) compared to the pressure in the accumulator (124) by means of later external movements, so that practically the energy accumulator by Movement of the patient is recharged.

10 consists of a multi-chamber cylinder with three chambers (201, 202 and 203). A piston (210, 211, 212) is arranged in each of these chambers (201, 202, 203). These pistons (210, 211, 212) are connected to one another via a coaxial common connecting rod (204) or spindle, which runs in a sealed manner from one chamber (201, 202) to the next chamber (202, 203). In this embodiment, only the pressure between the working surface (213, 214, 215) of the respective piston (210, 211, 212) and the opposite end wall of the working cylinder (201, 202, 203) is opened or closed by the valves (220, 221, 222) changed to an expansion tank (223). By opening and closing these valves (220, 221, 222), any combination of the chambers (201, 202, 203) or pistons (210, 211, 212) that are in engagement can be selected. The total work volume is thus also changed. The combination then achieves the various stiffnesses of the entire spring system. Due to the limited number of combinations, it is not possible to continuously adjust the spring constant stiffness. In the exemplary embodiment according to FIG. 11, the spring device (300) has two closed spaces (301, 302), each of which is filled with a highly compressible medium, for example a gas, and a slightly compressible medium, for example a liquid. The spaces (301, 302) are separated by a membrane (303). A change in the spring constant is achieved by changing the volumes in the two rooms (301, 302). The volume is changed by a hydraulic or pneumatic system, each with a pump (304, 305), an associated valve (308, 309) and an associated expansion tank (306, 307). This enables infinitely variable control of the rigidity.

12, the spring device (400) has a gas space (401) and two liquid spaces (402 and 403). One liquid space (402) is separated from the gas space (401) via a membrane (404). The two liquid areas (402, 403) are separated from one another by a rigid wall (408) in which there is a valve (406) adjustable by means of an actuator (405) and a check valve (407). A working piston (409) is located in the liquid space (403) which is further away from the gas space (401). When loaded, the piston (409) causes a volume change in the working area (403) and thus a defined liquid flow into the compensation area (402). The adjustable valve (406) allows the spring characteristics of the system to be changed in the event of rapid path changes. The system works on the principle of the liquid spring. When the pressure is relieved, the compressed gas in the gas space (401) ensures liquid balance through the check valve (407) from Compensation area (402) in the work area (403). This spring device can also be changed continuously.

In the exemplary embodiment according to FIG. 13, the spring device (500) has a cylinder (501) filled with liquid with a piston (502). The working cylinder (501) is connected to an expansion tank (504) via a control valve (503). Liquid can in turn be pumped from the expansion tank (504) into the working cylinder (501) by means of a pump (505) and a further control valve (506) in order to change the pressure in the working cylinder (501) and thus the spring constant. A stepless adjustment is possible with this.

In all of the above embodiments, the

Device, if it is an implant, of course with body-compatible gases or liquids.

14 a to 14 c show a completely mechanical embodiment of a spring device (600) according to the invention. In this embodiment, a simple helical spring (601) is mounted centrally within the telescopic sections (10, 11). Eccentric to the coil spring (601) there is a comb-like shaft (602) with several teeth (603). The stiffness of the spring device (600) is generated by blocking individual turns of the coil spring (601) by inserting the comb shaft (602) with the teeth (603) between the turns of the coil spring (601). For this purpose, the teeth (603) are arranged radially offset on the comb shaft (602). The comb shaft (602) is driven by a motor (604). 14 b and 14 c show the comb shaft (602) from above and from the side. Depending on how many teeth (603) of the comb shaft (602) are simultaneously engaged with the spring (601), a certain number of turns of the spring (601) are blocked and the stiffness is thus adjusted. However, it is not possible to adjust the stiffness or the spring constant continuously.

The spring device (700) in the exemplary embodiment according to FIGS. 15 a to 15 c has a non-linear spring plate

(702) wound spring (701). The cross section of the spring plate (702) increases with an increasing number of turns. 15 c shows a development of the spring plate

(702); 15 b is an enlarged view of the spring plate (702) wound into the spring (701). By changing the winding diameter and the associated change in the number of turns, the axial rigidity, i.e. the spring constant of the spring (701) can be changed continuously. This change in the winding diameter is carried out using a geared motor (703).

In the exemplary embodiments according to FIGS. 16 to 18 c, the spring device (800, 900, 1000) has a plurality of spring members (801 to 804, 901, 1001) connected in series and / or in parallel, and means for coupling in and out or for blocking the individual spring links (801 to 804, 901, 1001).

In the exemplary embodiment according to FIG. 16, several individual springs (801, 802, 803, 804) are connected in parallel to spring assemblies, which each extend between two control plates (805/807, 806/808). These spring assemblies are connected in series in the axial direction and can be coupled into and out of the system by means of corresponding coupling elements (809), so that the overall rigidity of the Spring device (800) is changed. A spring assembly can be decoupled, for example, by bridging the spring assembly by means of a rigid connection (not shown). Due to the limited number of springs that can be used, it is not possible to continuously change the spring constant.

16 further shows an actuator (810) via which the lower telescopic section (11) is coupled to the spring device (800) located in the upper telescopic section (10). A length change or the micro movement can be carried out via this actuator (810).

The spring device (900) according to FIG. 17 contains a link chain (902) constructed in the manner of a stork's beak or a pair of Nuremberg scissors. The connecting rods (903) between the joints (904, 905) are rigid. Springs (901) with associated actuators (906) are arranged between the articulation points (905) lying horizontally next to one another, which enable the individual springs (901) to be switched on and off. The spring stiffness of the entire spring device (900) is determined by the number of springs (901) connected. Of course, this also only allows a change in stiffness in certain stages.

In FIGS. 18 a to 18 c, the individual spring members (1001) are fiber elements (1001). These fibers (1001) are arranged in a circular cross-section (see FIG. 18 c) and extend from the lower telescope side to the upper telescope side. The inner and outer supports (1002, 1003, 1004) of the fibers (1001) prevent the fibers (1001) from buckling and thus achieve the highest spring stiffness. The external support is provided by two tubes (1003, 1004) which are inserted into each other changeable window openings are provided. The inner support is provided by a shaft (1002) with lateral bulges at the level of the window opening. If the two tubes (1003, 1004) of the outer support are rotated relative to one another, the window openings increase or decrease. Depending on the size of the window opening, there is the possibility for the fibers (1001) to buckle. The more fibers (1001) buckle, the lower the spring stiffness of the entire spring device (1000). A length compensation mechanism (1005) prevents the device from being shortened when the fibers (1001) are buckled. Fig. 18 a shows the spring device (1000) with the windows closed; Fig. 18 b with the windows open. 18 c shows a top view of the spring device (1000) with closed window openings according to FIG. 18 a. With this spring device (1000) it is not possible to change the spring constant continuously, but the spring constant can be changed in relatively small steps.

In the exemplary embodiment according to FIG. 19, the spring device (1100) has a permanent magnet (1101) and an electromagnet (1102), which repel one another. The rigidity can be set by the current strength running through the coils (103) of the electromagnet (1102). A suitable regulation enables a continuous change in the spring constant.

In the exemplary embodiment according to FIGS. 20 a and 20 b, the spring device (1002) has a centrally mounted circular disk (1201) with different segments (I to IV), each of which has a different elasticity. This circular disc (1201) is connected to the lower section (11) via a motor (1202). A counter bearing is located in the upper section (10) (1203) with two rollers (1204) which are in direct contact with the segmented circular disc (1201). The segments (I to IV) of the circular disc (1201) are divided so that opposite segments (I to IV) have the same elasticity. Depending on the position of the rollers (1204) of the counter bearing (1203) on the segments (I to IV), the spring device (1200) has a different spring constant.

The device according to the invention also contains a mechanical emergency lock (60, 70, 80, 90) which serves to prevent the linear movement of the sections (109, 11) against one another when a defined path (S) is exceeded. This route (S) should occur when a momentary emergency occurs, e.g. a sudden shock, no more than 1 to 2 millimeters. The emergency locking device (60, 70, 80, 90) has at least one locking means (61, 71, 81, 91) on a section (10), which is connected to the at least one corresponding locking means (63, 73, 83, 93) each other section (11) interacts.

In the exemplary embodiments shown in FIGS. 21 a and 21 b, two small slides (61) are seated in the outer tube section (10) and can be moved radially inwards by prestressed springs (62). They are attached to a defined place. The inner lower section (11) of the device also has a groove or a hole (63) in the circumferential direction at a correspondingly defined point. If the predetermined path (S) is exceeded, the slides (61) snap into the openings (63) and lock the two sections (10, 11) against each other. The slide (61) can be pulled back and disengaged again by means of a motor with a corresponding lever mechanism (not shown). 22 a to 22 c show a further embodiment. There are radially opposite, outwardly extending latching lugs (73) on the inner lower section (11). As soon as these locking lugs (73) touch a contact surface (74) on corresponding stops (72) which extend radially inwards in the outer upper section (10), a tube (76) is twisted by means of prestressed springs (75) abuts the inside of the outer upper section (10). This tube (76) has corresponding locking stops (71) at the upper end, which are rotated under the locking lugs (73) of the lower inner section (11), so that these locking lugs (73) between the upper stop (72) of the outer section (10) and the locking stops (71) of the inner tube (76) are clamped. The inner tube (76) can be turned back by means of appropriate motors or hydraulic or pneumatic devices (not shown). At the same time, the springs (75) are pretensioned again, so that the emergency lock is released and at the same time is ready for a new release.

It is important in both mechanisms that the emergency lock can only be reset if the triggering mechanism is also preloaded accordingly, so that the emergency lock responds reliably even without external energy.

The releasable emergency locks have the advantage that when the intramedullary nail (50) is installed, the two sections (10, 11) can be in the locked position, ie that the intramedullary nail (50) is rigid during installation. The intramedullary nail (50) can then be driven in like a conventional, rigid intramedullary nail. Only after installation can a control system, for example, check whether all components the device work. Then the emergency lock is released and the device can perform its task.

23 to 25 c show three further exemplary embodiments for emergency arrests.

In the exemplary embodiment according to FIG. 23, the outer upper tube section (10) has a groove (81) formed on the inside from an elastic material, into which a lug (83) engages on the inner lower tube section (11).

In the embodiment according to FIG. 24, the inner lower tube section (11) is elastically designed at its upper end through a slot (82), so that the opposite lugs (83) compress and fit into a groove (81) in the outer upper tube section ( 10) click into place. This groove (81) is not formed from an elastic material, but has a run-on slope (84) on which the locking lugs (83) are pressed together during an axial movement in the direction of the groove (81).

In the embodiment shown in FIGS. 25 a to 25 c, the outer tube has elastic clips (91) at the predetermined location, which snap into a groove (81) located in the inner tube section (11).

The device also contains various sensors (12) which measure various parameters, from which the current healing state can be determined alone or in conjunction with other parameters. These sensors can be temperature sensors, ultrasonic sensors or the like. There are also sensors (13) in the device, which Provide information about instantaneous speeds, acceleration forces, pressure forces or the like on the device. Furthermore, the device can also be connected to external sensors (16), for example on the underside of the patient's foot, with which pressure forces are also measured, for example. These sensors are connected to a control device (40). In the case of external sensors (16), the connection is preferably wireless.

Furthermore, there are various actuators in the device in the form of hydraulic, pneumatic or electric motors with which a change in the total length of the device between the fixing points (21, 22), at which the sections on both sides of the bone damage (2) are attached to the bone , is possible, and with which the length of the device can also be changed periodically in the form of micro movements. These can be additional actuator systems which are connected in parallel or in series with the spring device (20, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200). In principle, however, such as 9, the spring device itself also serve as an actuator. In order to enable the various actions of continuously changing the length or of the micro-movements or also of resetting the emergency lock, either different small motors must be installed, or a motor is connected to the movement mechanisms via corresponding couplings.

In the device there is also an energy store (41) in the form of a battery or the like, with which the electrical or electronic components can be supplied.

The controller (40) determines the respective one from the data given by the sensors and from externally entered data Healing state and accordingly controls the actuators or varies the spring constant.

This is a self-optimizing controller (40) which has its own database with a knowledge base and a reasoning mechanism so that the controller can learn, store and use new knowledge while the device is operating. The controller (40) can e.g. be built directly into the device in the form of a microcontroller. It then has a data transmission interface for the percutaneous transmission of the data to an external controller (42). This external control can e.g. permanently with the patient, i.e. e.g. attached to a patient's belt or strapped to the outside of the thigh. Alternatively, the external control (42) can also be located at the doctor, so that the internal control (40) is only checked at regular intervals.

Of course, it is also possible for the entire controller (40) to be external and for the individual actuators and sensors to be connected individually to the controller (40) via corresponding data transmission interfaces for the percutaneous transmission of data.

The spring device, the actuators and the sensors are designed accordingly small, so that the entire structure e.g. in a medullary nail of normal size, with a length of approx. 400 millimeters and a diameter of approx. 16 millimeters.

As shown in FIGS. 7 and 8, the implant according to the invention becomes a completely faster one Bone restoration achieved than with conventional rigid implants. 7 shows the load-bearing capacity of the bone (a) and the load-bearing capacity of the implant (b) in the event of a fracture of the lower extremities depending on the course of healing. At the beginning of the treatment, the entire load lies on the implant. The load capacity of the bone is 0%. The load on the implant decreases as the load capacity of the bone increases. After a healing time of approx. 6 to 14 weeks, the bone has attained maximum load-bearing capacity. However, this maximum load-bearing capacity is far from the original load-bearing capacity of the undamaged bone. A large part of the load is therefore absorbed by the implant. The implant is then removed at time c. As a result, the load-bearing capacity of the bone initially drops somewhat due to the weakening of the cross-section by the fastening screws and due to the injury from the surgical intervention, and only then does it increase to its original load-bearing capacity.

FIG. 8 shows the load capacity of a bone as a function of the healing time with a conventional implant for comparison under curve e; In this respect, curve e corresponds to curve a from FIG. 7. For comparison, curve d shows the load-bearing capacity of the bone as a function of the healing time for bone healing with a device according to the invention.

A further example of a spring arrangement with an adjustable spring constant is shown in FIG. 26. The stiffness of the spring mechanism is set by the different number of plate spring assemblies (821-823) which are engaged in parallel. There is also the possibility of different before assembling To use disc spring assemblies, in particular the number of springs contained therein is selected according to the purpose.

The shaft (827), which connects the spring assemblies in a controlled manner, is driven by a motor (820) via a coupling (828) with an axial degree of freedom. By turning the shaft (827) the number of threaded sections (824-826) of the shaft (827), which are connected to the threads of the cover plate (829-831) of the spring assemblies, can be varied. The threads, which are not in engagement, do not transmit any force to the corresponding spring assembly.

Claims

claims

1. Device (50, 51, 52) for the retention and protection of damaged bones (1), with two sections (10, 11, 11 ') which can be fixed on both sides of the bone damage (2) to a bone (1) and which are used to bridge the Bone damage (2) via at least one spring device (20, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200) are axially resiliently coupled to one another, characterized in that the device means for varying the spring constant.

2. Device according to claim 1, characterized in that the two sections (10, 11) are telescopically displaceable into one another and the spring device (20, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100 , 1200) is arranged inside the sections (10, 11) and counteracts a compression of the sections (10, 11).

3. Device according to one of claims 1 to 2, characterized in that the sections (10, 11) are secured against rotation against each other about their connecting axis (30).

4. Device according to one of claims 1 to 3, characterized in that it has at least one stop for limiting the axial movement of the sections (10, 11) to a maximum length.

5. Device according to one of the preceding claims, characterized in that the spring device (100, 200) at least one working chamber (101, 201, 202, 203, 403, 501), at least a piston (110, 210, 211, 212, 409, 502) movably disposed therein and means (120 to 125, 220 to 223, 401, 402, 404, 405 to 408, 503 to 506) for changing the pressure and / or the pressure ratios and / or the volume and / or the volume ratios in the working chamber (s) (101, 201, 202, 203, 403, 501).

6. Device according to one of the preceding claims, characterized in that the spring device (600) has at least one mechanical spring element (601) and means (602) for changing the effective length of the spring element (601).

7. Device according to one of the preceding claims, characterized in that the spring device (800, 900, 1000) a plurality of spring members connected in series and / or in parallel (801-804; 821-823, 901, 1001) and means for input or Decoupling and / or for blocking the individual spring members (801-804; 821-823, 901, 1001).

8. Device according to one of the preceding claims, characterized in that the same as an intramedullary nail (50) or as an outside of the bone (1) attached implant (52) or as an external fixator

(51) is formed.

9. Device according to one of the preceding claims, characterized in that it has an emergency lock (60, 70, 80, 90) which, when the two sections (10, 11) are displaced by a certain axial path length (S) against each other, a further axial movement of the sections (10, 11) to one another is prevented.

10. The device according to claim 9, characterized in that the emergency lock (60, 70, 80, 90) on a portion (10) has at least one locking means (61, 71, 81, 91) which with at least one corresponding locking means (63 , 73, 83, 93) on the other section (11).

11. The device according to claim 9 or 10, characterized in that it has the same means for releasing the emergency lock.

12. Device according to one of the preceding claims, characterized in that the same has at least one sensor (12) for measuring at least one parameter, from which alone and / or in conjunction with other parameters, the current state of healing can be determined.

13. Device according to one of the preceding claims, characterized in that it has at least one actuator (14, 15) for changing the length of the device between the fixing points (21, 22) at which the sections (10, 11, 11 ') are attached to the bone (1) on both sides of the bone damage (2).

14. Device according to one of the preceding claims, characterized in that it has at least one actuator (14, 15) for periodically changing the length of the device between the fixing points (21, 22) in the form of micro movements.

15. Device according to one of the preceding claims, characterized in that the same a controller (40) for determining the current state of healing from the measured and / or externally entered parameters and / or for automatic variation of the spring constant and / or for automatic length change the device between the fixing points (21, 22) and / or for the automatic execution of the micro movements.

16. The apparatus according to claim 15, characterized in that the controller (40) is a self-optimizing controller.

17. The apparatus of claim 15 or 16, characterized in that the controller (40) has a database with a knowledge base and a reasoning mechanism so that the controller can learn, store and use new knowledge during the operation of the device.

18. Device according to one of the preceding claims, characterized in that the same at least one

Data transmission interface for percutaneous transmission of data between the sensor (s) (12, 13) and / or the actuator (s) (14, 15) and / or the controller (40) and an external controller.