US20230397918A1 - System for Connecting a Connecting Device, in Particular a Distractor, to a Bone - Google Patents

Abstract

System for connecting a connection device to a bone with a bone pin, wherein the connection device is provided with an opening for receiving the bone pin, wherein the system comprises:

• • said connection device;
  • a guiding tube arranged to guide the bone pin from the connection device to the bone for connecting the bone pin to the bone, wherein the inner diameter of the guiding tube corresponds to the outer diameter of the bone pin and wherein the guiding tube can be slidably received in the opening, the guiding tube being slidable with respect to the connection device along an axis parallel to a longitudinal axis of the opening;
  • a locking device arranged to be received in the opening of the connection device and arranged to engage the bone pin for locking the bone pin with respect to the connection device,
    wherein the guiding tube is movable with respect to the connection device and bone pin such that the guiding tube is removable from the combination of the bone pin and the connection device and wherein the locking device is arranged to lock the bone pin after removal of the guiding tube.

Description

• This application is a continuation of U.S. application Ser. No. 17/130,543 filed Dec. 22, 2020, which application is a continuation of U.S. application Ser. No. 15/748,398 filed Jan. 29, 2018, now issued as U.S. Pat. No. 10,898,208, which application is a national stage entry of PCT/EP2015/067547 filed Jul. 30, 2015, the disclosures of which applications are herein incorporated by reference.
• The present invention relates to a system and method for connecting a connection device to a bone with a bone pin. The invention further relates to an external orthopaedic device, in particular a distractor, connecting different bones or bone parts. The invention further relates to a method for connecting an external distractor between at least two bone parts of a patient.
• In the field of trauma surgery as well as in orthopedics, external fixators are commonly used for treatment of complex fractures, stabilization of bony structures or joints, and in bone lengthening procedures. In external fixation, multiple bones or bone fragments are connected with a frame for providing additional structure to the bones, where fixation is achieved with bone pins, which can partially or fully penetrate the bone, providing one or more options per bone pin for attachment of an external device. More complex approaches comprise the use of ring fixators, or Ilizarov frames, which enable fixation of multiple bones with bone pins or tensioned wires, such that bones are reachable from nearly any direction preferably perpendicular to the longitudinal bone axis. For fixation of less bone parts, unilateral fixators, generally connected with multiple sets of two or three bone pins, may provide the required additional structure for a treatment.
• Various frame designs provide, besides fixation, additional features like adjustability of the frame for reconfiguration of the fixated bone parts after fixation and without replacing the bone pins, dynamization between the entry sites for stimulation of bone growth, or joint motion in case of fixation of multiple bones forming a joint. Recent development introduced externally fixated devices in treatment strategies for joint diseases like osteoarthritis where affected joints can be bridged by a dedicated external fixator for application of joint distraction.
• Osteoarthritis is a degenerative joint disorder, progressive over time, characterized by cartilage damage and loss, changes in peri-articular bone, synovial inflammation, and peri-articular muscle and ligament changes. These tissue changes are considered causative for clinical characteristics like pain, stiffness, and functional disabilities (Bijlsma J W J et al. Lancet 2011; 377: 2115-26). Knee osteoarthritis is the most prevalent form of osteoarthritis with an increasing socioeconomic and healthcare burden. Due to, amongst others, aging of the population and increase in obesity at a young age occurrence of knee osteoarthritis is estimated to increase significantly in the forthcoming years.
• Few options are available for treatment of end-stage knee osteoarthritis and none have clearly been shown to halt or reverse tissue structure damage. Conservative treatment focuses on minimizing functional disability and pain relief with anti-inflammatory treatment when indicated (Bijlsma J W J et al. Lancet 2011; 377: 2115-26).
• In case of uni-lateral tibio-femoral knee osteoarthritis, high tibial osteotomy or unilateral knee arthroplasty as well as new options like partial medial joint unloading by subcutaneous placed devices may provide a temporary solution. However, these techniques are rather invasive. Most importantly these techniques do not serve bi-lateral tibio-femoral knee osteoarthritis.
• Eventually for all these cases a total knee prosthesis is indicated, and joint tissue is removed from the bony ends and replaced by artificial joint components. Unfortunately, these endo-prostheses have a limited life span due to wear and tear of the materials. The younger the patients (the more active they still are) the shorter the life span of a knee prosthesis. In case placed at an age below 65 years the chance for revision surgery is high. These revision surgeries are much more complex and expensive with less good outcome.
• Therefore, there is a need for joint preserving treatments, to delay the first total knee prosthesis and with that prevent revision surgery. For specifically such cases, knee joint distraction has been introduced as a bi-lateral tibio-femoral joint preserving procedure. In case of failure of this treatment, the joint is uncompromised and any other treatment, including surgical intervention like hemi prosthesis, osteotomy or a total knee prosthesis remains optional.
• Knee joint distraction has quite recently been introduced as a tibio-femoral joint preserving procedure and is more and more accepted as option to postpone placement of a first prosthesis below the age of 65 years. Both clinical improvement and structural tissue regeneration have been demonstrated with clinically relevant duration. (Mastbergen S C et al Nat Rev Rheumatol. 2013; 9: 277-90). This surgical treatment gradually separates the bony ends of a joint to a certain extent, increasing the joint space width with approximately five millimetres, for a limited period of 6-8 weeks.
• Separation of the bony ends is achieved with an externally fixated device, connected to the bones forming the joint, with in general half bone pins drilled through soft tissues into both bone cortices. For a stable fixation bone pins are placed at multiple locations in each bone, in case of the knee at the medial and lateral side of femur and tibia. The external device is connected to these bone pins, as such forming a rigid structure enabling fixation of the whole joint and enabling distraction of the joint. Joint loads during application are primarily transduced via the external device and the bone pins, relieving the affected joint. In the distracted configuration, a confined axial displacement remains present when loaded and unloaded, still preventing further wear and tear of the damaged articulating surfaces with the resilience potentially stimulating the regenerating capability of the joint.
• As primary functionality, external fixators provide additional stiffness to a bony structure. Stiffness is established by interconnecting bony parts via bone pins to a frame with specifications that suit the chosen treatment strategy. The connection between the external frame, in particular a connection device thereof, and the bone pins should be ensured in order to have advantage of other system features. Due to the variation in optimal position between patients and anatomical sites, establishment of the connection between the bone pins and the frame often requires multiple actions like tightening of multiple bolts from multiple directions, while stability of the connection is not always ensured. Reusability of external devices, and accompanying signs of use like burrs and wear from the cleaning and sterilization procedures, often worsen the reliability of such connections. Since placement of a bone pin requires at least one line of action for attachment to a bone, it is ensured that for every placed bone pin, a certain position and orientation provides sufficient reachability for performing other actions like fixation of the pin to the external frame. A solution which enables use of this ensured line of action provides a more intuitive and easy way of working for the surgeon. Moreover, the established connection can become more reliable when critical components receive inspection previous to every usage, or even are replaced.
• A problem associated with known external orthopaedic devices including a system for connecting a connection device to the bone is therefore the heaviness and bulkiness of the existing solutions to frame the bones, because of the use of many components. Moreover, existing solutions require a time consuming surgery process to place the frame optimally to the human body, because of the use of (many) external tools for placement and assembling various system components to a functional structure. A further problem associated with known connection systems is that incorrect or non-optimal placement of bone pins may result in undesirable stress levels in the pin and in the bone structure.
• Fixation of the device with half-pins into the bones of the treated joint requires anatomically optimal positioning at each of the bony ends of the joint of interest, such that bone pins do not intersect or interfere with critical tissue structures like nerves and blood vessels, but also not with tendons and muscle bundles and with that reducing the risk for complications or permanent damage. Furthermore, bone pins should not enter the joint capsule. Additionally important bone pins should avoid the area where later in life a prosthesis needs to be placed, so they should be placed at a certain distance from the joint space. Clearly there are for all joints a limited number of preferable anatomical locations where bone pins should be placed for optimal result with minimal damage.
• As a result of the preferred anatomically available bone pin locations at each side of the joint and at the different sides of each bone, bone pins might need positional ‘misalignment’ with respect to mechanics of the external fixation frame, to obtain optimal anatomical positions of the bone pins. In case bone pins are positioned for fixation and distraction of the knee joint, angular misalignment around the mechanical axis of the joint results from the choice for optimal anatomical pin placement.
• The interaction of the bone pins with soft tissues is therefore a further problem associated with known external fixation devices such as external distractors. The pin positions and orientation are dictated by the device, such that pins may intersect with fragile soft tissue. Moreover, axial displacement cannot be guaranteed to stay parallel with the longitudinal axis of the tibia, which is preferred. If axial displacement is not parallel to the longitudinal axis of the tibia, the interdistance of the frame and the human leg increases in the length direction of the femur, which is not favourable regarding joint configuration, and which is making this construction uncomfortable for the patient to wear.
• It is a goal of the present invention, next to other goals, to provide a system for connecting a connection device to a bone wherein at least one of the above mentioned problems is solved or at least alleviated.
• This goal, amongst other goals, is met by a system according to the present disclosure. More specifically, this goal, amongst other goals, is met by a system for connecting a connection device to a bone with a bone pin, wherein the connection device is provided with an opening for receiving the bone pin, wherein the system comprises:
• • said connection device;
  • a guiding tube arranged to guide the bone pin from the connection device to the bone for connecting the bone pin to the bone, wherein the inner diameter of the guiding tube corresponds to the outer diameter of the bone pin and wherein the guiding tube can be slidably received in the opening, the guiding tube being slidable with respect to the connection device along an axis parallel to a longitudinal axis of the opening;
  • a locking device arranged to be received in the opening of the connection device and arranged to engage the bone pin for locking the bone pin with respect to the connection device,
    wherein the guiding tube is movable with respect to the connection device and bone pin such that the guiding tube is removable from the combination of the bone pin and the connection device and wherein the locking device is arranged to lock the bone pin after removal of the guiding tube.
• The system for connecting a bone pin to a connection device according to the invention allows the connection device, for instance in the form of a connection block of an external orthopaedic device, to be used as a drilling guide such that the trajectory of the bone pin is determined by the configuration of the connection device, in particular the orientation of the opening thereof. After proper guidance of the bone pin using the opening of the connection device, the bone pin can be efficiently locked to the connection device using a locking device which is shaped to be received in the opening of the connecting device and which is arranged to lock the bone pin with respect to the connection device. A simple and efficient connection system that is intuitive to use is herewith provided.
• Inserting the bone pins by drilling needs protection of the soft tissues during drilling by a guiding tube, sometimes also referred to as a cannula or sleeve, around the bone pin protecting soft tissue to be harmed by the rotating bone pin during drilling. To enable drilling of a bone pin through the connection device using the guiding tube and subsequent fixation of the bone pin after removal of the guiding tube to the connection device, a locking device is provided. In a preferred embodiment, rotation of the guiding tube is blocked during drilling.
• The invention also relates to a method for connecting a connection device to a bone with a system according to invention, wherein the method comprises the steps of:
• • providing a bone pin in said guiding tube in the opening of the connection device;
  • guiding the guiding tube to the bone by sliding said guiding tube in the opening of the connection device with respect to said connection device, such that the guiding tube abuts the bone;
  • inserting the bone pin into the bone;
  • removing the guiding tube from the combination of the bone pin and the connection device after insertion of the bone pin; and
  • locking the bone pin with respect to the connection device with said locking device after removal of the guiding tube.
• The opening is arranged to slidably receive a guiding tube. This allows adjusting the relative position of the guiding tube to be adjusted with respect to the connection device. It is in particular preferred that the depth of the guiding tube in the patient can be adjusted, such that the guiding tube is adjusted such that the distal end of the guiding tube abuts the bone. This prevents damage to the tissue surrounding the bone upon drilling of the bone pin.
• The connection system according to the invention is in particular suitable to connect a bone pin in accordance with a pre-planned trajectory. This trajectory is defined by the orientation of the opening of the connection device. This solves or at least alleviates the problem of incorrect placement of the bone pins, resulting in undesirable stress levels in the pin and in the bone structure, as well as on the device. The guiding tube is therefore preferably slidable in the opening along only the longitudinal axis of the opening. Any other relative movement is preferably prevented. The step of guiding the guiding tube therefore preferably comprises keeping the connection device substantially stationary with respect to the patient.
• According to a preferred embodiment, the locking device has an annular body having an outer diameter corresponding to the diameter of the opening of the connection device and an inner diameter suitable for engaging the bone pin. The outer surface having the outer diameter is then arranged to efficiently connect to the connection device due to the matching diameters. As an alternative, or in addition thereto, it may however also be possible that the locking device and the connection device interconnect at another location than the outer surface of the locking device.
• The inner surface of the locking device is then arranged to be able to lock the bone pin by engagement. This prevents movement between the locking device and the bone pin, such that also relative moment of the bone pin with respect to the connection device is prevented.
• In order to achieve an efficient locking of the bone pin, the locking device according to a preferred embodiment comprises an engaging surface for engaging the bone pin, wherein the engaging surface is movable towards and from said bone pin between an unlocked position, wherein the bone pin is movable with respect to the engaging surface, and a locking position, wherein the engaging surface engages the bone pin for locking said bone pin with respect to the connection device by clamping. The step of locking the bone pin in the method according to the invention therefore preferably comprises engaging the bone pin with an engaging surface of the locking device for clamping said bone pin. The engagement surface is preferably moveable radially inwardly towards the longitudinal axis of the bone pin.
• It may be possible that the engagement surface is only movable from the unlocked position to the locked position, such that the bone pin can no longer be loosened after locking with the locking device, preferably with (but not restricted to) plastically deforming either of the components, preferably the locking device. It is however preferred if the engaging surface is also movable from the locked to the unlocked position, such that the bone pins can be loosened if needed.
• The engaging surface may for instance be formed on movable or deformable parts of the locking device, such as tongues, which are movable towards and preferably also from the bone pin for locking the bone pin.
• Preferably, the locking device has an inner diameter substantially corresponding to the diameter of the bone pin. In this embodiment, the locking device can only be placed in the opening after the removal of the guiding tube, as the guiding tube would not fit in the locking device. Providing a locking device having an inner diameter corresponding to the outer diameter of the bone pin allows a good locking action, as for instance the engagement surface only needs to be displaced over a little distance to obtain a good clamping action.
• As an alternative, the locking device has an inner diameter substantially corresponding to the outer diameter of the guiding tube in the unlocked position. This allows the locking device to be already in place in the opening when the guiding tube is guided in the opening. The locking device may then have a guiding function for guiding the guiding tube. When the guiding tube is removed after insertion of the pin in the bone, the engagement surface is moved towards the bone, thereby bridging the wall thickness of the then removed guiding tube, to clamp the bone pin.
• In order to be able to efficiently move the engaging surface to the locked position, the opening of the connection device preferably has a tapering diameter, seen along the longitudinal axis of the opening, for moving the engaging surface between the positions, upon longitudinal movement of the locking device with respect to the connection device. The step of locking the bone pin in the method according to the invention then preferably comprises moving the locking device along the longitudinal axis of the opening of the connection device for urging the engaging surface onto the bone pin. The tapering diameter, or at least varying diameter, of the opening then serves as a guiding surface for guiding the engagement surface towards the bone pin for engagement. To further improve the movement of the engaging surface, the locking device preferably comprises a correspondingly shaped tapering outer diameter.
• As an alternative, it is also possible that only the locking device has a varying outer diameter, for instance a wedge shape, which urges the engaging surface onto the bone pin upon movement of the locking device into the opening.
• According to a further preferred embodiment, the locking device comprises a deformable element arranged to deform in the locked position for engaging the bone pin. The deformable element may for instance be manufactured from a resilient material such as rubber or flexible plastic.
• The locking device may be formed as a single unit. This reduces the number of parts. It is however also possible that the locking device comprises an engaging element provided with at least one engaging surface and a separate driving element arranged to move the engaging element along the longitudinal axis of the opening for moving the engaging surface from the unlocked to the locked position. It is for instance possible that the driving element is removed from the opening after locking the bone pin with the engaging element. This prevents accidental loosening of the bone pin.
• It is however preferred when the engagement element is arranged to be moved to the locked position upon movement in the opening along the longitudinal axis as explained above, that the engaging element comprises at least one second engaging surface at a distance from the first engaging surface, seen along the longitudinal axis of the opening. This allows clamping at two locations of the bone pin, thereby improving the locking action. The driving element is then preferably provided with an opening for receiving the engaging element and wherein the opening of the driving element has a tapering diameter, seen along the longitudinal axis of the opening, for moving the second engaging surface between the unlocked and locked position upon longitudinal movement of the driving element with respect to the engaging element. Also the engaging element and the driving element are then provided with a cooperating guiding surfaces for urging the engaging surface towards the bone pin. As said, this improves the locking action.
• According to a further preferred embodiment, the opening comprises, seen along the longitudinal axis of the opening, a first section having a first diameter and a second section having a second diameter corresponding to the outer diameter of the guiding tube, wherein the first diameter is larger than the second diameter. The change in diameter can be used to move the engaging surface towards the bone pin as mentioned above. The broader section moreover allows receipt of the locking device. To efficiently move the engaging surface as mentioned above, it is further preferred if the opening comprises a tapering section extending between the first and the second sections in which the diameter tapers from the first diameter towards the second diameter. It may be possible that the second section has a limited length, such that the tapering section extends until the end, wherein diameter at the end corresponds to the second diameter.
• According to a further preferred embodiment, the opening of the connection device and the locking device are provided with cooperating connecting means for interconnecting the locking device and the connection device. This improves the locking action. Several types of connecting means may be used. It is for instance possible to use a bayonet connection between the locking device and the connection device having a resilient lip engaging in a correspondingly shaped recess or groove. For instance in the case a deformable part is used, it is preferred if the opening is provided with a recess, preferably a groove, for receiving the deformable element for locking the connection device and the locking device.
• Efficient locking, while allowing easy manipulation, is however obtained if the locking device and the connection device are provided with cooperating threading.
• In case a driving element is used, it is preferred if the driving element and the opening of the connection device are provided with cooperating connecting means. This then locks the driving element with respect to the connection device, while the locking element and the driving element are further preferably also provided with cooperating connecting means.
• In order to provide sufficient room for the connecting means, it is preferred if the connecting means are provided in the first, broader section of the opening.
• As mentioned above, it is possible that the locking device is arranged to receive and guide the guiding tube. The locking device thereto has a suitable inner diameter. It is however also possible to use a separate guiding element, such that the locking device is dedicated to lock the bone pin. The inner diameter of the locking device may then correspond to the outer diameter of the bone pin as mentioned above. Therefore, a further preferred embodiment of the system further comprises a guiding element for guiding the guiding tube, wherein the guiding element is arranged to be received in the opening of the connection device, wherein the guiding element has an outer diameter corresponding to the diameter of the opening and wherein the guiding element has an inner diameter corresponding to the outer diameter of the guiding tube, wherein the guiding element and the guiding tube are removable from the combination of the bone pin and the connection device. The method according to the invention then preferably further comprises the step of inserting a guiding element in the opening of the connection device and arranging the guiding tube in said guiding element.
• After proper guidance of the guiding tube, which in turns guides the bone pin to the bone, the guiding tube and the guiding element are removed. Preferably, the guiding element is removed prior to locking the bone pin. Also the guiding element preferably has an annular body. The outer diameter thereof preferably corresponds to the diameter of the opening, more preferably the annular body has an outer diameter corresponding to the diameter of the first section of the opening. The guiding element is then placed in the first section of the opening and serves to bridge the distance between the inner wall of the opening and the guiding tube.
• In order to at least temporary fix the guiding element to the connection device to allow a stable guidance of the guiding tube, the guiding element is preferably provided with corresponding connecting means for interconnecting the guiding element and the connection device. The same connecting means as used for connecting the locking device in the opening are preferably used.
• According to a further preferred embodiment wherein a separate driving element is used, said driving element is formed as the guiding element. This reduces the number of parts.
• The system according to the invention is in particular useful for connecting a connection device to a bone with two parallel bone pins. A further preferred embodiment of the system according to invention therefore further comprises a second locking device, wherein the connection device comprises a second opening for receiving a second bone pin, wherein the longitudinal axes of the first and the second openings are substantially parallel and wherein the second locking device is arranged to lock the second bone pin after removal of a guiding tube from the second opening. The openings hereby define at least one of the trajectories of the bone pins to be inserted into the bone.
• The invention thus further relates to a method for connecting a connection device to the bone with two parallel bone pins, comprising the step of connecting a connection device to the bone with a first bone pin and connecting the connection device to the bone with a second bone pin according to the method according to the invention. Using two parallel bone pins allows adjustment of distance of the connection device with respect to the patient, in particular when the locking device also allows loosening of the bone pins after locking said bone pin.
• At least the second bone pin is connected in the above described manner, wherein the opening is used as drilling guide. After placement of a first bone pin at the most appropriate preferred anatomical position, the locations of additional bone pins is (to a certain extend) determined as they are all to be connected to the same external device. To facilitate guiding of the subsequent bone pins for fixation to an external device to the optimal anatomical bone pin positioning there is an advantage to use the for each application specifically designed connection device as bone pin positioning guide or drilling guide. In this way the optimal anatomical position of the bone pin is directly related to an optimal connection to the device and with that the mechanical positioning of the device. Moreover, the optimal anatomical positions can be found intuitively by the guidance of the connecting device.
• The first pin may also be fixed using the system and method according to invention. It is however also possible that the step of connecting a connection device to the bone with a first bone pin comprises:
• • inserting the bone pin into the bone using a guiding tube;
  • removing said guiding tube from the inserted bone pin;
  • arranging the connection device onto said inserted bone pin;
  • locking the bone pin with respect to the connection device with a locking device,
    wherein the method further comprises subsequently connecting the second bone pin according to the method according to the invention. As the position of the connection device with respect to the patient is then fixed, it is an advantage that the slidable guiding tube is adjustable in depth to allow efficient protection of the surrounding tissue upon insertion of the second bone pin.
• The invention further relates to an external orthopaedic device arranged to be connected between a first bone part and a second bone part, wherein the orthopaedic device comprises a first connection device according to the invention and a second connection device, preferably also according to the invention. This orthopaedic device can be connected efficiently to the patient as discussed above. For each application this connecting device will be specifically shaped to guide the bone pins of the second connecting device intuitively to the preferred anatomical bone pin position and to provide optimal positioning of the second connecting device regarding mechanical characteristics of the entire configuration.
• The invention further relates to an external orthopaedic device in the form of an external distractor arranged to gradually enlarge the distance between a first bone part and a second bone part, wherein the distractor comprises a first connection device, preferably as defined above, and a second connection device, preferably also as defined above, wherein the first connection device is arranged to be connected to the first bone part with at least one first bone pin and wherein the second connection device is arranged to be connected to the second bone part with at least one second bone pin, wherein the first and second connection devices are interconnected via at least a distraction device, the distraction device having an adjustable length for adjusting the distance between the first and the second connection devices along an adjustment axis.
• The distractor device preferable comprises a first part and a second part which are movable with respect to each other along the adjustment axis. The parts may for instance be provided with cooperating threading to allow the adjustment of the length. The distractor device is preferably arranged to adjust the distance between the bone pins while maintaining the structural integrity of the distractor. The distance can thus be adjusted while transferring loads between the first and second bone parts.
• The invention therefore also relates to a method for connecting an external distractor between at least two bone parts of a patient, comprising the steps of:
• • providing an external distractor according to the invention;
  • connecting the first connection device to the first bone part with at least one bone pin; and
  • connecting the second connection device to the second bone part with at least one bone pin.
• In particular when using the connection system according to the invention, the distractor can efficiently be connected to the patient. It is however noted that the invention is not necessarily limited to a distractor having connection devices according to invention. Addition of other connection devices, such as connection blocks which are known as such, may also be used.
• In order to prevent further wear and tear of the damaged articulating surfaces and to potentially stimulate the regenerating capability of the joint, it is preferred if the distractor, in particular the distractor device thereof, comprises resilient means which are arranged for allowing resilient movement along the adjustment axis between the connection devices. The resilient means, for instance in the form of a spring or similar device, then allows small displacements along the adjustment axis.
• Although it is possible that the distractor device directly couples the two connection devices, it is preferred if the external distractor further comprises an interconnecting system extending between the first and second connection devices, wherein the interconnecting system is movable between an unlocked position, wherein the connection devices are movable with respect to each other, and a locked position, wherein the mutual positions of the connection devices are fixed. The interconnecting system allows the connection devices to be moved with respect to each other which is in particular useful when connecting the distractor to the patient.
• The interconnecting system may for instance comprises at least one lockable hinge, preferably two at either side connected to the connection devices. It is preferred that the interconnecting system is connected to the first and second connection devices with two respective lockable ball joints. This allows the connection devices to be efficiently moved with respect to each other.
• A preferred method according the invention therefore preferably further comprises the steps of:
• • providing the interconnecting system in the unlocked position;
  • aligning at least one of the connection devices along a predetermined axis with respect to a bone part; and
  • moving the interconnecting system to the locked position for fixing the mutual positions of the connection devices after alignment.
• Preferably, the interconnecting system is moved to the locked position after fixation of the bone pins.
• According to a further preferred embodiment, the distraction device is arranged in one of the connection devices, preferably integrally, wherein the interconnecting system extends between the distraction device and the other connection device. More preferably, the ball joint is formed as a part of the distractor device. The distraction device is hereby coupled between a connection device, and the interconnecting device. Although the distraction device may be formed integrally, it is also possible that the distraction device is insofar arranged in one of the connection devices that the minimal distance between the opening in the connection device and the adjustment axis of the distraction device is movable and can be fixed. The location of the opening in the connection device may for instance be adjustable along the adjustment axis of the distraction device to allow adjusting the length of the distractor upon connecting the distractor to the patient.
• To allow efficient distraction, in particular of a joint, it is important that the distraction device is correctly aligned with the bone parts. It is in particular preferred if the adjustment axis is aligned with at least one of the longitudinal axes of the bone parts. The step of aligning therefore preferably comprises aligning the longitudinal axis of a bone to be substantially parallel to the adjustment axis of the distraction device. This alignment is more easy to perform if the distraction device is part of one of the connection devices as mentioned above, although this is not strictly necessary.
• In order to allow connection of the connection device to a bone without damaging fragile soft tissue (at the anatomically preferred locations), while still allowing axial displacement parallel with the longitudinal axis of the bone (for optimal mechanical performance of the configuration), for instance the tibia, according to a further preferred embodiment the connection device is arranged to receive the bone pin at a certain distance from the adjustment axis.
• In order to transduce loads over the joint via the distraction device, correction in alignment is required to ensure optimal unloading of the joint. A certain off-set of the bone pin connection to the axis of the device as well as preferably a certain curvature in the device as will be explained below to obtain optimal anatomical bone pin locations relative to optimal mechanical positioning of the external device will be needed.
• According to a further preferred embodiment, at least one of the connection devices is arranged to be connected to the bone part with two substantially parallel bone pins. This improves the stability of the system, while the distance of the connection device and the patient is still adjustable as explained above.
• At least one of the steps of connecting a connection device to the respective bone part according to the invention then comprises connecting the connection device to two substantially parallel bone pins. Preferably both connection devices are connected to the bone with two parallel bone pins. The connection devices thereto preferably comprise two openings for receiving two bone pins. The step of aligning then preferably comprises aligning the connection device such that the openings in the connection device are arranged along an axis substantially parallel to the longitudinal axis of the respective bone part. This allows efficient alignment, wherein the openings in the connection devices are used as a reference for alignment.
• It is then preferred if a connection device is provided with two openings for receiving the two bone pins, wherein the openings in the connection device are arranged along an axis at a distance from the pivot point of the ball joint. This creates an offset between the pivot point of the ball joint and the openings through which the bone pins are to extend. This offset allows an improved connection to the bone, at the preferred anatomical positions of the bone pins, preventing potential damage to sensible surrounding tissues. This offset may be specific for specific devices for specific joint bones.
• For the connection device provided with the distraction device, it is preferred that when the connection device is provided with two openings for receiving the two bone pins, the openings in the connection device are arranged along an axis substantially parallel to the adjustment axis and such that the two bone pins extend substantially perpendicularly to the adjustment axis. The openings of the connection device can then be used to correctly align the adjustment axis with a predetermined axis of the bone, preferably the longitudinal axis of the bone. It is again preferred if an offset is created between the adjustment axis and an axis onto which the openings in the connection device extend. The openings in the connection device are therefore preferably arranged along an axis at a distance from the adjustment axis.
• In particular for distracting a knee joint, it is preferred if one connection device is arranged to receive its bone pins at a distance in a first direction from the adjustment axis or the pivot point, wherein the second connection device is arranged to receive its bone pins at a distance in a second direction from the adjustment axis or the pivot point, the second direction being substantially opposite to the first direction. This protects sensible tissue when inserting the bone pins in accordance with the openings provided at an offset as explained above. Moreover, it provides intuitive positioning of the bone pins at the preferred anatomical locations, guided by the openings in the connection device.
• In order to further adapt to the curvature of the patient, it is preferred if the connection device comprises a patient facing surface and an outer surface, wherein an opening extends between the patient facing surface and the outer surface, wherein at least the patient facing surface of the connection device has a curved cross-section, seen in a plane perpendicular to the axis trough the openings. The patient facing surface is then preferably curved in accordance with the curvature of the patient. This provides further intuitive positioning of the bone pins at the preferred anatomical locations, guided by the openings in the connection device.
• The distractor is particularly suitable to be used to distract the knee joint. The invention thus also relates to a method for connecting an external distractor between the tibia and the femur, wherein one of the connection devices is connected to the tibia and the other connection device is connected to the femur.
• When setting joint distraction to the distraction device, only an increasing joint space width is aimed for, while further joint configuration remains intact. To do so, the distraction direction needs to be orthogonal to both joint surfaces. In case of the knee this means perpendicular to the tibial surface and in the axial direction of the tibia. Specifically to the knee joint, the femoral joint side has a convex, spherical like, surface, while the tibial joint side has a more flattened concave corresponding surface. A direction of distraction orthogonal to both joint sides can be achieved, independent from flexion angle of the joint, by choosing the direction orthogonal to the least spherical surface, or orthogonal to the most flattened surface.
• As the connection of the bone pins in the femur is more critical in terms of surrounding tissue which may be damaged, it is preferred if the femur is connected to its connection device prior to connecting the tibia to its connection device.
• It is hereby possible that the first pin is inserted into the femur using a guiding tube, to subsequently connect the connection device according to the invention. A second bone pin can then be inserted into the bone using the connection device as drill guide after proper alignment of the connection device, in particular along the longitudinal axis of the bone.
• According to a further preferred embodiment, the step of aligning comprises aligning the adjustment axis of the distraction device in the connection device to be substantially parallel to the longitudinal axis of the tibia in the coronal plane and preferably the sagittal plane substantially perpendicular to the tibial plateau. This provides an efficient distraction of the knee joint.
• It is hereby noted that it is in particular important that the longitudinal axis of the tibia is aligned with the adjustment axis. It may for instance be possible that the patient is not capable of completely extending the knee, such that the alignment axis is not properly aligned with the longitudinal axis of the femur, such that the connection device on the femur is not aligned with the longitudinal axis of the tibia. The interconnection system then still allows proper alignment of the connection device on the tibia, such that the adjustment axis is parallel to the longitudinal axis of the tibia as explained above.
• It is noted that the term aligned as used herein is to be understood that the axes to be aligned are substantially parallel, that is within ±10 degrees with respect to each other.
• It is hereby preferred if each of the connection devices is provided with two openings for receiving the two bone pins, wherein the connection devices are aligned such that the openings in the connection device are arranged along axes substantially parallel to the longitudinal axes of the respective bones and such that the two bone pins extend substantially perpendicularly to the longitudinal axes of the respective bones. In order to prevent damage to tissue as already mentioned above, it is then preferred if the step of aligning the connection devices further comprises aligning the adjustment axis and/or the pivot points of the ball joints substantially on the coronal plane, and:
• • orienting the openings of the connection devices to be connected to the femur in a posterior position; and/or
  • orienting the openings of the connection devices to be connected to the tibia in anterior position.
• The distractor as explained may be used as an unilateral distractor. It is however preferred to use the system as a bilateral system for application of knee joint distraction. The invention thus also relates to a method for connecting an external distractor system between at least two bone parts of a patient, comprising the steps of connecting a first external distractor according to the invention at a first side of the bone parts and connecting a second external distractor according to invention at a second side, opposite the first side of the bone parts. It is hereby preferred if the first and second external distractors are arranged substantially on the similar coronal plane on either side of the knee.
• The present invention is further illustrated by the following Figures, which show a preferred embodiment of the device and method according to the invention, and are not intended to limit the scope of the invention in any way, wherein:
• FIGS.1A-1D schematically show a system and method for connecting a connection device to a bone;
• FIGS.2A-2D schematically show a variant of the system ofFIGS.1A-1D;
• FIGS.3A and3B schematically show a variant of fixing a bone pin to a connection device;
• FIG.4 shows a variant of a connection device having two openings;
• FIG.5 shows a distractor according to the invention;
• FIGS.6A-6C shows a first connection device of the distractor ofFIG.5 in perspective, top view and side view respectively;
• FIGS.7A-7D shows a second connection device with distraction mechanism in perspective, top view in two positions and in side view respectively;
• FIG.8 shows the positional relationship of the bone pins of the two connection devices in side view;
• FIGS.9A-9B and10A-10B show a joint knee and the femur and tibia in cross section indicating the bone pin positions; and
• FIGS.11A-11C show a bilateral distraction system according to the invention.
• InFIGS.1A-1D the steps for connecting a connection device1 in the form of a connection block to abone100 is shown. The connection block1 is thereto provided with anopening11 which extends between afirst surface12, which faces thepatient101, and asecond surface13 which faces away from thepatient101. Theopening11 has asection11atowards thesecond surface13 which is provided with threading14. Towards thepatient facing surface12, theopening11 is provided with atapering section11bwherein the diameter of theopening11 becomes smaller in the direction of thepatient101, seen along a longitudinal axis A of theopening11.
• Inserted into the opening is alocking device2 which has a substantially annular shape and is shaped to fit inside theopening11. Thelocking device2 has aflange21 at one side anddeformable tongues22 at the other side and a body23 provided there between. The body23 is provided with threading24 for cooperation with the threading14 of the opening. The outer diameter of the body23 of thelocking device2 thereby corresponds to the diameter of thefirst section11aof theopening11. The length of the body23 provided with the threading24 preferably corresponds to the length of the first second11aof theopening11, seen along the longitudinal axis A.
• The threading14,24 fixes the relative position of thelocking device2 and the connection device1, which position can be adjusted by rotating thelocking device2. In the position as show inFIG.1A, the lower surface of theflange21 extends at a distance from thesurface13, such that further movement of thelocking device2 in a direction indicated with I inFIG.1A is possible, as will be explained in greater detail below. In the situation as shown inFIG.1A, thetongues22 of thelocking device2 only partially extend in thetapering section11bof theopening11.
• The inner diameter of thelocking device2, including the diameter at the location of thetongues22, corresponds to the outer diameter d1 of a guidingcannula3. This limits relative movement of thelocking device2, which also serves as a guiding device for guiding thecannula3, in a direction along the longitudinal axis A. The guidingcannula3 is arranged to guide abone pin4 from the connection device1 to thebone100, seeFIG.1B. In inserted situation as shown inFIG.1B, thecannula3 is thereto slidable along the longitudinal axis A with respect to thelocking device2 and thereby with respect to theconnection device2. Aflange32 is provided to allow efficient adjustment of the depth of thecannula3. This allows efficiently guiding abone pin4 to thebone100, irrespective of the distance between the connection device1 and thebone100. When thecannula3 is advanced sufficiently far such that adistal end31 abuts thebone100, thebone screw4 can be inserted into thecannula3, schematically indicated with the arrow inFIG.1B. The inner diameter of thecannula3 thereto corresponds to the outer diameter of thebone pin4 such that relative movement of thebone pin4 in thecannula3 is again restricted to movement along the longitudinal axis A. The movement of thebone pin4 with respect to the connection device1 is therefore also fixed.
• In a next step, seeFIG.1C, thebone pin4 can be fixed to thebone100. In this example, self-tappingbone screws4 are used, such that the bone pins4 are inserted into thebone100 by rotating thebone pin4 inside thecannula3. Thecannula3 thereby prevents damage to the surrounding tissue of thepatient3.Other bone pins4 can however be used.
• After fixation of thebone pin4 to thebone100, thecannula3 can be withdrawn from the combination of thebone pin4, thelocking device2 and the connection device1. This movement is indicated with the arrow inFIG.1C. As the inner diameter of thelocking device2 corresponds to the outer diameter of thecannula3, which is larger than the outer diameter of thebone pin4, thebone pin4 is held in thelocking device2 with play. Therefore, in order to lock thebone pin4 with respect to thelocking device2 and thereby with respect to the connection device1, thelocking device2 is rotated, thereby moving thelocking device2 along the longitudinal axis A, see arrow inFIG.1D, in theopening11. The outer surfaces of thetongues22 will thereby engage the inner surface of thetapering section11b, urging thetongues22 radially inwardly, i.e. towards to the longitudinal axis and thereby towards thebone pin4. The inner surface of thedeformable tongues22 thereby act as engaging surfaces which are arranged to engage thebone pin4, thereby locking thebone pin4 with respect thelocking device2 and thereby the connection device1. In the locked position as shown inFIG.1D, the lower surface of theflange21 of thelocking device2 abuts theupper surface13 of the connection device1, which is in this example provided with a correspondingly shaped recess to receive theflange21 in a countersunk manner.
• In this situation, thebone pin4 is firmly locked with respect to the connection device1. It will be appreciated, as will be explained in greater detail below, that thebone pin4 can simply be unlocked by rotating thelocking device2, thereby loosening thetongues22 such that thelocking device2 is again movable with respect to thebone pin4.
• In the example shown inFIGS.1A-1D, thelocking device2 serves to lock thebone pin4 and to guide thecannula3. It is however also possible to use a separate guiding device to guide thecannula3. Moreover, in the above example, the relative position of thelocking device2 and the connection device1 is fixed using threading14,24. Other means can however be used as will also be shown with reference toFIGS.2A-2D.
• The connection device1 as shown inFIGS.2A-2D is similar to the connection device1 as shown inFIGS.1A-1D and is again provided with anopening11. The diameter of thisopening11 is again larger than the outer diameter d1 of thecannula3, such that a guidingdevice5 is used to limit the relative movement between thecannula3 and the connection device1 along the longitudinal axis A, seeFIG.2B. The guidingdevice5 again has a annular shape and has an inner diameter corresponding to the outer diameter d1 of thecannula3. This allows efficient adjustment of the depth of thecannula3 with respect to the connection device1 as indicated with double arrow inFIG.1B. Note that this is different from thelocking device2 as used inFIGS.1A-1D.
• Instead of threading, the guidingdevice5 is provided with adeformable part51 which locks into theopening11 upon inserting thepart51. Thedeformable part51 thereby exerts a clamping action of the inner surface of theopening11, thereby retaining the guidingdevice5 in theopening11 by friction. The guidingdevice5 is further provided with aflange52 for easy manipulation of the guidingdevice5.
• After insertion of thebone pin4, seeFIG.2C, the combination of the guidingdevice5 and thecannula3 can be removed from the combination of thebone pin4 and the connection device1, see arrowFIG.2D. As thebone pin4 is firmly attached to the bone, the combination can be withdrawn by pulling sufficiently hard to overcome the friction of thedeformable part51 of the guidingdevice5. Thecannula3 and the guidingdevice5 can hereby be removed in unison.
• Although a locking device similar to the locking device as shown inFIGS.1A-1D can be used to lock thebone pin4 with respect to the connection device1, for instance by providing corresponding threading, it is also possible to use a locking mechanism formed of two separate parts, as is shown inFIGS.3A and3B.
• The locking mechanism comprises a drivingelement6 and alocking element7, wherein the annularly shaped lockingelement7 is provided with sets oftongues71,72 at either side. Both sets oftongues71,72 are arranged to move radially inwardly upon deformation, thereby locking thebone pin4. The first set oftongues71 at the lower side of thelocking element7 are moved radially inwardly upon moving, or driving, the lockingelement7 in a direction indicated with the arrow inFIG.1A. The reduction of the diameter indicated with19 in theopening11 will thereby urge thetongues71 towards the outer surface of thebone pin4. Agroove11cis provided near end of theopening11 towards the patient, whereinribs71aof thetongues71 can snap for locking the relative positions of thelocking element7 with respect to the connection device1. In this locked position, thetongues71 exert a firm clamping action on thebone pin4 at a location along the longitudinal axis A indicated with the arrow C inFIG.3B, thereby preventing movement of thebone pin4.
• To further improve the locking action, also to thetongues72 provided on the upper side of thelocking element7 will be urged radially inwardly upon movement of the drivingelement6 towards the lockingelement7. More specifically, the annularly shaped drivingelement6 is provided with anopening61 of which thelower section64 has a tapering diameter, wherein the diameter increases towards the lower side. The taperingsection64 forms a guiding surface for urging thetongues72 inwardly, i.e. towards thebone pin4, when the drivingelement6 is moved towards the lockingelement7.
• Also thetongues72 can be provided withribs72awhich can be received in a correspondingly shapedgroove63 at the end of the guiding surface. This connects the drivingelement6 to thelocking element7 and thereby to the connecting device1. In the situation as show inFIG.3B, thetongues72 exert a clamping action on thebone pin4 at a location along the longitudinal axis A indicated with B, at a distance from location C. This improves the locking action of the locking mechanism.
• The locking system may but not necessarily make use of ribs (71a/11cand72a/63) and corresponding grooves at either side or at both sides, to fix the7 into the connecting device1 or the drivingelement6 or both.
• The connection system as described above is particularly suitable to connect a connection device to a bone with two parallel bone pins. This is explained with reference toFIG.4. Although in this figure a connection system is shown which corresponds to the system as shown inFIGS.1A-1D, it will be appreciated that the same applies to the system as shown inFIGS.2A-2D and3A-3B, or combinations thereof.
• InFIG.4, a connection device1 is shown provided with twoparallel openings11, into which bone pins4aand4bare inserted. In this example,bone pin4awas inserted first by using a separate cannula to drill thebone pin4ainto thebone100. After fixation of thisbone pin4a, the connection device1 was advanced over theproximal end42 of thepin4aand thepin4awas locked with respect to the connection device1 using alocking device2a. In order to ensure that asecond pin4bwas inserted parallel to thefirst bone pin4a, the connection method similar to the methods shown inFIGS.1A-1D and2A-2D was used to insert and connect thebone pin4b. A cannula is thereby used to guide thebone pin4bto thebone100, the surface of which differs in terms of height from the surface of thefirst bone pin4aas shown inFIG.4.
• In this example however, a separate guiding device was used (similar to the method ofFIGS.2A-2D) to guide the cannula, although a locking device in one piece was used (similar to the locking device ofFIGS.1A-1D). Moreover, the interconnection of thelocking devices2aand2b(and the guiding devices which are not shown) with the connection device1 is obtained with corresponding threading, again similar to the embodiment ofFIGS.1A-1D. The situation of thebone pin4bas shown inFIG.4 thus corresponds to the situation ofFIGS.2D and3A: after guidance and insertion of the pin and prior to locking of thepin4b.
• Using a connection device1 having two parallel openings for receiving bone pins, ensures that after fixation of a first bone pin in the bone, a second bone pin will be inserted into the bone parallel to the first bone pin. The guiding device and the cannula after all limit movement of the bone pin with respect to the connection device along the longitudinal axis of the opening. The connecting element as such guiding the second bone pin to a preferred anatomical position.
• Providing parallel bone pins allows adjusting the distance between the connection device1 and thepatient101, of which theskin101ais schematically indicated inFIG.4. In case of for instance a swelling, as schematically indicated aroundbone pin4b, thelocking devices2aand2bmay be loosened, in this example by rotating thelocking devices2a,2b, such that the connection device1 is again movable with respect to the bone pins4a,4b, schematically indicated with the double arrow inFIG.4. After displacement of the connection device1 along the longitudinal axes of the bone pins, thelocking devices2a,2bcan again be tightened to lock the bone pins4a,4bwith respect to the connection device1.
• In the following figures, an external orthopaedic device, in this example in the form of adistractor110 is explained. Theexternal distractor110 of this example is arranged to distract, that is gradually enlarge, the joint space width of the knee joint. Thedistractor110 is thereto provided withconnection devices1a,1bto receive and lock thepins4a,4bwithlocking devices2.Connection device1ais arranged to be connected to the tibia with two parallel bone pins4a, whereasconnection device1bis arranged to be connected to the femur using two parallel bone pins4b. It is noted that although it is preferred to use a connection system as shown in any of theFIGS.1A-1D-4 to connect the bone pins4a,4bto the respective bones, this is not strictly necessary. Other suitable connection systems may be used.
• Theconnection devices1a,1bare interconnected by an interconnectingsystem120. Theinterconnection system120 comprises a centraltubular member123 of which both ends comprisereceptacles121a,barranged to receiveballs140a, b(see for instanceFIGS.6A and7A) of theconnection devices1a, bfor forming ball joints. Thereceptacles121a, bfor theballs140a,bare arranged to receive theballs140a, bin a rotating manner in an unlocked position and to prevent any relative movement of theballs140a, bwith respect to theirrespective receptacles121a,bin a locked position. In the unlocked position, theconnection devices1a,1bare substantially free to rotate and angulate with respect to the centraltubular member123, while in the locked position, the relative positions of theconnections devices1a,1bare fixed withscrew122.
• With reference toFIGS.6A-6C, theconnection device1bis provided with twoopenings11 which extend between apatient facing surface12 and anouter surface13. Bothopenings11 are oriented parallel with respect to each other. The longitudinal axes A of the openings, and thus of the insertedbone pins4b, therefore also extend parallel. As mentioned above, theconnection device1bis provided with aball140bto form a ball joint when inserted into the receptacle of the interconnectingsystem120. With specific reference toFIG.6B, it can be seen that theball140b, in particular thecentre140cthereof, extends at a distance d2 from an axis A3 extending though (the centres of) bothopenings11. The axis A3 is perpendicular to the longitudinal axes A of the openings. The distance d2 is in this example determined as the minimal distance between the axis A3 and thepivot point140c. As shown inFIG.6C, this construction creates an offset d2 of the longitudinal axes A of the openings11 (and thereby of the bone pins4b) with respect to thepivot point140c.FIG.6C further illustrates that thelower surface12 of theconnection device1bis curved (bended) towards the patient, seen in the direction from thepivot point140ctowards theopenings11 in thelower surface12, enabling optimal intuitive guidance to anatomically preferred positions of the bone pins with proper mechanical characteristics of the whole configuration of device and bones.
• Theother connection device1ais discussed in greater detail with reference toFIGS.7A-7D. Also thisconnection device1ais provided with twoparallel openings11 for receiving two parallel bone pins4a. Theopenings11 again extend between apatient facing surface12 and anouter surface13. Also thisconnection device1ais provided with aball140ato form a ball joint in combination with thereceptacle121aof the connectingsystem120.
• Theconnection device1ais however further provided with a distraction mechanism, generally indicated with130. The distraction mechanism comprises means to adjust the distance between the bone pins4aand4bof the twoconnection devices1a,1b. More specifically, the distraction mechanism is arranged to gradually increase the distance between thepivot point140cof theball140aand theopenings11 for the bone pins4a. This is achieved by cooperating threading provided on thesupport131 of theball140aandrotatable ring132 at the end of atubular base body134 of theconnection device1a. Rotation of thering132 will adjust the distance L1 between thebase body134 and theball140a, as is visible inFIGS.7B and7C. This allows adjusting the length L1 along an adjustment axis A4. In this example, the adjustment axis A4 is defined to extend through thecentre140cof theball140aforming the pivot point of the ball joint.
• It will be appreciated that the adjustment of the length L1 along the adjustment axis A4 can take place without loosening the tension or structural integrity between the twoconnection devices1a,1b, thereby keeping the joint at the preferred relative distance. In order to allow adjustment of the distance between the two sets ofbone pins4a,4bprior to use, theconnection device1acomprises abody19 which is arranged slidable along thetubular body134 in a direction L2. Movement of thebody19, which is provided with theopenings11, can be locked using thescrew19a.
• In order to still allow little displacement along the adjustment axis A4 during use of the patient, thestem133 of theball140ais resiliently supported, in this example using a spring, in thesupport131 of theball140a.Support131 and stem133 are thus allowed to move, as indicated with the double arrow L3 along the adjustment axis A4.
• Although theball140ais allowed to move with respect to theopenings11 for receiving the bone pins4a, due to thedistraction mechanism130 or the sliding movement between thebody19 and thetubular body134, the relative orientation of theopenings11 along an axis A3 with the respect to the adjustment axis A4 remains unchanged. The axis A3 extending between the two centres of theopenings11 and perpendicular to the longitudinal axes A thereof extends at a distance d3 and parallel to the adjustment axis A4. The same offset d3 is also visible inFIG.7D, wherein also a curvedpatient facing surface12 is shown as option.
• As is already clear fromFIG.5, the offset of the bone pins4bin theconnection device1bis opposite to the direction of the offset in theconnection device1awith thedistraction mechanism130. This relative orientation is further shown inFIG.8, which is a view of the system ofFIGS.1A-1D along arrow VIII inFIG.5.
• InFIG.8 it can be seen that the longitudinal axes Aa, Ab of the two sets ofpins4a,4bextend under an angle α with respect to each other. The offset d2, i.e. the distance between the adjustment axis A4 (also thepivot point140c) and the axis A3 through theopenings11 of theconnection device1bis in the opposite direction of the offset d3, i.e. the distance between the axis A3 through theopenings11 in theconnection device1aand thepivot point140c. It also shows the curvature in this case in one of the connectingdevices1b. This configuration allows an efficient placement of thedistractor110 on the patient, with preferred anatomical location of bone pins, preventing damage to or interference with critical tissues.
• In case of the knee joint, placement of adistractor110 on apatient101 is explained while referring toFIGS.9A-9B and10A-10B. In a first step of fixing thedistractor110 to thepatient101 to distract the knee joint101b, afirst bone pin4bis inserted into thefemur101cwith an orientation which is posterior (indicated with P in the cross section ofFIG.9B seen along the transverse plane Tp1 ofFIG.9A) with respect to the coronal plane Cp. This prevents damage to and/or interference with sensible tissue. For the fixation of thefirst pin4b, a separate cannula may be used to connect thebone pin4bto thebone101c. After fixation of thefirst bone pin4b, aconnection device1bof thedistractor110 is connected to thebone pin4b. Theconnection device1bis then aligned such that the axis A3 between theopenings11 is aligned to be substantially parallel to the longitudinal axis Af of thefemur101c. Theconnection device1bis then used as drill guide, preferably using the system as shown inFIGS.1A-1D-4, to insert asecond bone pin4bparallel to thefirst bone pin4bat the location of the transverse plane Tp2. Bone pins4bthen extend parallel and perpendicular to the longitudinal axis Af of thefemur101c.
• As the interconnectingsystem120 of thedistractor110 is in the unlocked position, theconnection device1aprovided with thedistraction mechanism130 is freely movable with respect to the already fixedconnection device1b. As it is important that the adjustment axis A4 of thedistraction mechanism130 is parallel to the longitudinal axis At of thetibia101d, (FIGS.10A-10B) theconnection device1ais arranged such that the adjustment axis A4 is parallel to said longitudinal axis At of thetibia101d. This can be done by aligning the axis A3 through theopenings11 in theconnection device1ato be parallel to the longitudinal axis At of thetibia101d.
• With reference toFIGS.10A and10B, the trajectories A of the bone pins4aare chosen to be anterior (indicated with Ant in the transverse section ofFIG.10B along plane Tp1 inFIG.10A) with respect to the coronal plane Cp. This prevents damage to and/or disturbance of sensible tissue. It is hereby noted that the configuration of thedistractor110 and more in particular the offsets d2 and d3 as shown inFIG.8 automatically forces the posterior placement of the bone pins4bin thefemur101cand the anterior placement of the bone pins4ain the tibia101 (intuitive guiding of optimal anatomical positions of bone pins by the device). The bone pins4aare inserted into thebone101dusing theopenings11 of theconnection device1aas drill guides, preferably using the method as shown inFIGS.1A-1D-4.
• After correct fixation of the twoconnection devices1aand1bat preferred distance from the bone/skin enabled by parallel pins), theinterconnection system120 can be moved to the locked position, thereby fixing the relative positions of theconnection devices1a,1b.
• It is possible to use thedistractor110 as an unilateral distractor. It is however also possible to use the distractor in a bilateral configuration. For that case, a second distractor having a configuration which is mirror symmetrical with respect to the sagittal plane Sg (seeFIGS.9B and10B) is connected to the patient. The orientation of the bone pins4a,4bfor thefemur101candtibia101dis indicated in phantom inFIGS.9B and10B. This configuration is shown inFIGS.11A-11C, whereinFIG.11A shows a transverse section in thefemur101c,FIG.11B shows a transverse section in thetibia101dandFIG.11A-11C is a side view of the system.
• The present invention is not limited to the embodiment shown, but extends also to other embodiments falling within the scope of the appended claims.

Claims (56)

1. System for connecting a connection device to a bone with a bone pin, wherein the connection device is provided with an opening for receiving the bone pin, wherein the system comprises:

said connection device;

a guiding tube arranged to guide the bone pin from the connection device to the bone for connecting the bone pin to the bone, wherein the inner diameter of the guiding tube corresponds to the outer diameter of the bone pin and wherein the guiding tube can be slidably received in the opening, the guiding tube being slidable with respect to the connection device along an axis parallel to a longitudinal axis of the opening;

a locking device arranged to be received in the opening of the connection device and arranged to engage the bone pin for locking the bone pin with respect to the connection device,

wherein the guiding tube is movable with respect to the connection device and bone pin such that the guiding tube is removable from the combination of the bone pin and the connection device and wherein the locking device is arranged to lock the bone pin after removal of the guiding tube.

2. System according toclaim 1, wherein the locking device has an annular body having an outer diameter corresponding to the diameter of the opening of the connection device and an inner diameter suitable for engaging the bone pin.

3. System according toclaim 1 or2, wherein the locking device comprises an engaging surface for engaging the bone pin, wherein the engaging surface is movable towards and from said bone pin between an unlocked position, wherein the bone pin is movable with respect to the engaging surface, and a locking position, wherein the engaging surface engages the bone pin for locking said bone pin with respect to the connection device by clamping.

4. System according toclaim 3, wherein the locking device has an inner diameter substantially corresponding to the diameter of the bone pin.

5. System according toclaim 3, wherein the locking device has an inner diameter substantially corresponding to the outer diameter of the guiding tube in the unlocked position.

6. System according to any of the precedingclaims 3-5, wherein the opening of the connection device has a tapering diameter, seen along the longitudinal axis of the opening, for moving the engaging surface between the positions upon longitudinal movement of the locking device with respect to the connection device.

7. System according toclaim 6, wherein the locking device comprises a correspondingly shaped tapering outer diameter.

8. System according to any of the precedingclaims 3-7, wherein the locking device comprises a deformable element arranged to deform in the locked position for engaging the bone pin.

9. System according to any of the precedingclaims 3-8, wherein the locking device comprises an engaging element provided with at least one engaging surface and a separate driving element arranged to move the engaging element along the longitudinal axis of the opening for moving the engaging surface from the unlocked to the locked position.

10. System according to at leastclaims 6 and9, wherein the engaging element comprises at least one second engaging surface at a distance from the first engaging surface, seen along the longitudinal axis of the opening, wherein the driving element is provided with an opening for receiving the engaging element and wherein the opening of the driving element has a tapering diameter, seen along the longitudinal axis of the opening, for moving the second engaging surface between the an unlocked and locked position upon longitudinal movement of the driving element with respect to the engaging element.

11. System according to any of the preceding claims, wherein the opening comprises, seen along the longitudinal axis of the opening, a first section having a first diameter and a second section having a second diameter corresponding to the outer diameter of the guiding tube, wherein the first diameter is larger than the second diameter.

12. System according toclaims 6 and11, wherein the opening comprises a tapering section extending between the first and the second sections in which the diameter tapers from the first diameter towards the second diameter.

13. System according to any of the preceding claims, wherein the opening of the connection device and the locking device are provided with cooperating connecting means for interconnecting the locking device and the connection device.

14. System according to at leastclaims 8 and13, wherein the opening is provided with a recess, preferably a groove, for receiving the deformable element for locking the connection device and the locking device.

15. System according to at leastclaims 9 and13, wherein the driving element and the opening of the connection device are provided with cooperating connecting means.

16. System according to at leastclaims 11 and13, wherein the connecting means are provided in the first section of the opening.

17. System according toclaim 13,15 or16, wherein the opening and the locking device are provided with cooperating threading.

18. System according to any of the preceding claims, further comprising a guiding element for guiding the guiding tube, wherein the guiding element is arranged to be received in the opening of the connection device, wherein the guiding element has an outer diameter corresponding to the diameter of the opening and wherein the guiding element has an inner diameter corresponding to the outer diameter of the guiding tube, wherein the guiding element and the guiding tube are removable from the combination of the bone pin and the connection device.

19. System according to at leastclaims 11 and18, wherein the guiding element has an annular body having an outer diameter corresponding to the diameter of the first section of the opening.

20. System according to at leastclaims 13 and18, wherein the guiding element is provided with corresponding connecting means for interconnecting the guiding element and the connection device.

21. System according to at leastclaim 9 and any of theclaims 18-20, wherein the driving element is formed as the guiding element.

22. System according to any of the preceding claims, further comprising a second locking device, wherein the connection device comprises a second opening for receiving a second bone pin, wherein the longitudinal axes of the first and the second openings are substantially parallel and wherein the second locking device is arranged to lock the second bone pin after removal of a guiding tube from the second opening.

23. External orthopaedic device arranged to be connected between a first bone part and a second bone part, wherein the orthopaedic device comprises a first connection device as defined in any of the preceding claims and a second connection device, preferably as defined in any of the of the preceding claims.

24. External distractor arranged to gradually enlarge the distance between a first bone part and a second bone part, wherein the distractor comprises a first connection device as defined in any of the preceding claims and a second connection device, preferably as defined in any of the of the preceding claims, wherein the first connection device is arranged to be connected to the first bone part with at least one first bone pin and wherein the second connection device is arranged to be connected to the second bone part with at least one second bone pin, wherein the first and second connection devices are interconnected via at least a distraction device, the distraction device having an adjustable length for adjusting the distance between the first and the second connection devices along an adjustment axis.

25. External distractor according toclaim 24, further comprising resilient means which are arranged for allowing resilient movement along the adjustment axis between the connection devices.

26. External distractor according toclaim 24 or25, further comprising an interconnecting system extending between the first and second connection devices, wherein the interconnecting system is movable between an unlocked position, wherein the connection devices are movable with respect to each other, and a locked position, wherein the mutual positions of the connection devices are fixed.

27. External distractor according toclaim 26, wherein the interconnecting system comprises at least one lockable hinge.

28. External distractor according toclaim 26 or27, wherein the interconnecting system is connected to the first and second connection devices with two respective lockable ball joints.

29. External distractor according to any of the precedingclaims 26-28, wherein the distraction device is arranged in one of the connection devices, preferably integrally, wherein the interconnecting system extends between the distraction device and the other connection device.

30. External distractor according toclaim 29, wherein the connection device is arranged to receive the bone pin at a distance from the adjustment axis.

31. External distractor according to any of the preceding claims, wherein at least one of the connection devices is arranged to be connected to the bone part with two substantially parallel bone pins.

32. External distractor according to at leastclaims 28 and31, wherein a connection device is provided with two openings for receiving the two bone pins, wherein the openings in the connection device are arranged along an axis at a distance from the pivot point of the ball joint.

33. External distractor according to at leastclaims 29 and31, wherein the connection device is provided with two openings for receiving the two bone pins, wherein the openings in the connection device are arranged along an axis substantially parallel to the adjustment axis and such that the two bone pins extend substantially perpendicularly to the adjustment axis.

34. External distractor according toclaim 33, wherein the openings in the connection device are arranged along an axis at a distance from the adjustment axis.

35. External distractor according to at leastclaim 32 or34, wherein one connection device is arranged to receive its bone pins at a distance in a first direction from the adjustment axis or the pivot point, wherein the second connection device is arranged to receive its bone pins at a distance in a second direction from the adjustment axis or the pivot point, the second direction being substantially opposite the first direction.

36. External distractor according to any of theclaims 32-35, wherein the connection device comprises a patient facing surface and an outer surface, wherein an opening extends between the patient facing surface and the outer surface, wherein at least the patient facing surface of the connection device has a curved cross-section, seen in a plane perpendicular to the axis trough the openings.

37. Method for connecting a connection device to a bone with a system according to any of the preceding claims, wherein the method comprises the steps of:

providing a bone pin in said guiding tube in the opening of the connection device;

guiding the guiding tube to the bone by sliding said guiding tube in the opening of the connection device with respect to said connection device, such that the guiding tube abuts the bone;

inserting the bone pin into the bone;

removing the guiding tube from the combination of the bone pin and the connection device after insertion of the bone pin; and

locking the bone pin with respect to the connection device with said locking device after removal of the guiding tube.

38. Method according toclaim 37, wherein the step of guiding the guiding tube comprises keeping the connection device substantially stationary with respect to the patient.

39. Method according toclaim 37 or38, wherein the step of locking the bone pin comprises engaging the bone pin with an engaging surface of the locking device for clamping said bone pin.

40. Method according toclaim 39, wherein the step of locking the bone pin comprises moving the locking device along the longitudinal axis of the opening of the connection device for urging the engaging surface onto the bone pin.

41. Method according to any of the preceding claims, further comprising the step of inserting a guiding element according toclaim 18 in the opening and arranging the guiding tube in said guiding element.

42. Method according toclaim 41, wherein the guiding element is removed prior to locking the bone pin.

43. Method for connecting a connection device to the bone with two parallel bone pins, comprising the step of connecting a connection device to the bone with a first bone pin and connecting the connection device to the bone with a second bone pin according to the method of any of theclaims 37-42.

44. Method according toclaim 43, wherein the step of connecting a connection device to the bone with a first bone pin comprises:

inserting the bone pin into the bone using a guiding tube;

removing said guiding tube from the inserted bone pin;

arranging the connection device onto said inserted bone pin;

locking the bone pin with respect to the connection device with a locking device,

wherein the method further comprises subsequently connecting the second bone pin according to the method of any of theclaims 37-42.

45. Method for connecting an external distractor between at least two bone parts of a patient, comprising the steps of:

providing an external distractor according to any of theclaims 24-36;

connecting the first connection device to the first bone part with at least one bone pin according to any of the preceding claims; and

connecting the second connection device to the second bone part with at least one bone pin.

46. Method according toclaim 45, wherein at least one of the connection devices is provided with two openings for receiving two substantially parallel bone pins, wherein at least one of the steps of connecting a connection device to the respective bone part comprises connecting the connection device with two substantially parallel bone pins.

47. Method according toclaim 45 or46, wherein the external distractor comprises an interconnecting system extending between the first and second connection devices, wherein the interconnecting system is movable between a unlocked position, wherein the connection devices are movable with respect to each other, and a locked position, wherein the mutual positions of the connection devices are fixed, wherein the method further comprises the steps of:

providing the interconnecting system in the unlocked position;

aligning at least one of the connection devices along a predetermined axis with respect to a bone part; and

moving the interconnecting system to the locked position for fixing the mutual positions of the connection devices after alignment.

48. Method according toclaim 47, wherein the distraction device is arranged in one of the connection devices, preferably integrally, wherein the interconnecting system extends between the distraction device and the other connection device, wherein the step of aligning comprises aligning the longitudinal axis of a bone to be substantially parallel to the adjustment axis of the distraction device.

49. Method according to at leastclaims 46 and47, wherein the step of aligning comprising aligning the connection device such that the openings in the connection device are arranged along an axis substantially parallel to the longitudinal axis of the respective bone part.

50. Method according to any of the precedingclaims 45-49 for connecting an external distractor between the tibia and the femur, wherein one of the connection devices is connected to the tibia and the other connection device is connected to the femur.

51. Method according toclaim 50, wherein the femur is connected to its connection device prior to connecting the tibia to its connection device.

52. Method according to at leastclaim 48 and50 or51, wherein the step of aligning comprises aligning the adjustment axis of the distraction device in the connection device to be substantially parallel to the longitudinal axis of the tibia in the coronal plane and the sagittal plane substantially perpendicular to the tibial plateau.

53. Method according to any of theclaims 50-52 when dependent onclaims 46 and47, wherein each of the connection devices is provided with two openings for receiving the two bone pins, wherein the connection devices are aligned such that the openings in the connection device are arranged along axes substantially parallel to the longitudinal axes of the respective bones and such that the two bone pins extend substantially perpendicularly to the longitudinal axes of the respective bones.

54. Method according toclaim 53, wherein the step of aligning the connection devices further comprises aligning the adjustment axis and/or the pivot points of the ball joints substantially on the coronal plane, and:

orienting the openings of the connection devices to be connected to the femur in a posterior position; and/or

orienting the openings of the connection devices to be connected to the tibia in anterior position.

55. Method for connecting an external distractor system between at least two bone parts of a patient, comprising the steps of connecting a first external distractor according to any of the precedingclaims 45-54 at a first side of the bone parts and connecting a second external distractor according to any of the precedingclaims 45-54 at a second side, opposite the first side of the bone parts.

56. Method according to at leastclaims 50 and55, wherein the first and second external distractors are arranged substantially on the coronal plane on either side of the knee.

Images