Abstract:
The present disclosure relates to an anchoring group for an external fixator, that comprises a connecting body designed to be coupled to a bar of an external fixator. A locking device is connected to the connecting body at a fastening point thereof and comprises a pin locking arm provided with two seats suitable for locking a corresponding number of uni-cortical pins. A connection base is intended to be coupled to a connecting body of the anchoring group. An additional member, also associated with the connecting body, comprises at least one auxiliary seat, not aligned with the seats of the locking device, for locking an additional uni-cortical pin. In an additional embodiment, the connection base of the locking device extends in an angled relationship with respect to the pin locking arm and away from both the seats. The connection base has a point for fastening to the connecting body which is not aligned with said seats.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application claims priority to European Patent Application 13178834.1 which was filed Jul. 31, 2013 and is incorporated herein by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present disclosure pertains to the field of orthopaedic surgery and relates in particular to the application of an external fixator to a long bone by means of unicortical pins. 
         [0003]    The disclosure also relates to an anchoring group comprising the aforementioned pin-locking device articulated to a locking clamp of an external fixator bar, as well as to an external fixator comprising said anchoring group. 
       BACKGROUND 
       [0004]    External fixators are widely used for the treatment of bone fractures or for joining together two or more bone fragments. Known fixators comprise bone screws which are inserted in the bones and use external devices such as fixation clamps, fixation bars, rings, etc., that allow the creation of a rigid structure able to hold together the bone fragments in the desired position until completely healed. 
         [0005]    These external fixators have the advantage of ensuring strength and stability owing, among other things, to the use of bone screws which penetrate into the bones at a sufficient depth; in particular, these screws pass through the bone cortex in two points so as to provide a flexurally resistant fastening. 
         [0006]    However, the use of bi-cortical screws may be excessively invasive for patients in critical conditions, who for example have multiple fractures along with, in some case, extensive wounds and/or contusions. In particular the time devoted to checking the tip which emerges from the second cortex may be critical. 
         [0007]    Also, with particular reference to the reduction of fractures in long bones, the aforementioned bi-cortical screws pass through the medullary cavity, which makes it impossible to simultaneously insert a medullary nail, which is particularly suitable for the treatment of certain types of trauma. 
         [0008]    Moreover, the surgical implant of a definitive fixator of the aforementioned type requires time and suitable facilities and is not always compatible with the unforeseen circumstances where rapid intervention is required; for example, it is relatively difficult to perform the implant of such an external fixator in the context of a field hospital or in any case under environmental conditions where sterility is not guaranteed and where the fracture must be treated as a matter of emergency. 
         [0009]    In order to meet these specific needs, external fixators of a provisional nature have been developed that, in addition to having a structure which is generally slimmer and lighter, use unicortical screws or unicortical pins for the attachment to the bone, i.e. that have been designed to be screwed in superficially so that they are attached to a single bone cortex only. 
         [0010]    The unicortical pin undoubtedly represents a less invasive fixation system than conventional bone screws; moreover, owing to its limited penetration, the pin does not reach the medullary cavity of the bone, thus avoiding the risk of unwanted infections. 
         [0011]    On the other hand, however, owing to its limited stability—due mainly to the fact that it passes through one cortex only, which means that flexural strength is limited—this type of screw is not widely used in external fixation applications. 
         [0012]    It would instead be desirable to be able to use an external fixator, which has the advantages of stability and strength typical of provisional fixation systems, and to combine it with the advantages of ease of application, lightness and limited invasiveness that are instead typical of systems that use unicortical pins. 
         [0013]    The technical problem forming the basis of the present disclosure is therefore to devise a locking device for unicortical pins to be associated with external fixators, which is able to create a structure sufficiently rigid for it to withstand the external loads acting on it, so as to allow the formation of external fixators that are extremely flexible, but that at the same time have that degree of structural rigidity that typically distinguishes external fixation systems. 
         [0014]    The device should have an optimum performance, under traction and compression, of the tip in the cortex of the bone and should eliminate, as far as possible, the flexural stresses acting on the shank of the single screw. 
       SUMMARY OF THE DISCLOSURE 
       [0015]    In some embodiments of the present disclosure, the aforementioned technical problem may be solved by using a locking device for unicortical pins. 
         [0016]    In some embodiments of the present disclosure, application of an external fixator to a patient&#39;s long bone by means of the unicortical pins is provided for. 
         [0017]    The application method described above may make it possible to create fixation systems with exceptional stability, despite its use of unicortical pins only. 
         [0018]    Further features and advantages will become clearer from the detailed description provided below of some preferred, but not exclusive, embodiments of the present disclosure, with reference to the attached figures provided by way of non-limiting example. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIGS. 1-4  show different perspective views of an external fixator associated with the long bone of a patient using the method according to the present disclosure, where the locking devices of the distal and proximal anchoring groups are mounted in different configurations; 
           [0020]      FIG. 5  shows a front view of an anchoring group associated with the bone of a patient; 
           [0021]      FIG. 6  shows a perspective view of the anchoring group of  FIG. 5 ; 
           [0022]      FIG. 7  and  FIG. 8  show two perspective views of an anchoring group, in which mounting of the locking devices in two different configurations is shown; 
           [0023]      FIG. 9  shows a perspective view of a connecting body of the anchoring group; 
           [0024]      FIG. 10  shows a front view of the connecting body of  FIG. 9 ; 
           [0025]      FIG. 11  shows a further perspective view of the connecting body of  FIG. 9 ; 
           [0026]      FIG. 12  shows a perspective view of the locking clamp of the anchoring group; 
           [0027]      FIG. 13  shows a perspective view of the main body of a locking device; 
           [0028]      FIG. 14  shows another perspective view of the main body of  FIG. 13 ; 
           [0029]      FIG. 15  shows a perspective view of the pressing body of the locking device; 
           [0030]      FIG. 16  shows a perspective view of the locking means of the locking device; 
           [0031]      FIG. 17  shows a perspective view of a deformable sphere forming part of the locking means shown in  FIG. 16 ; 
           [0032]      FIG. 18  shows a perspective view of a bar/pin clamp which can be associated with the connection bar of the external fixator. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    With reference to the attached figures, and in particular to  FIGS. 1-4 , the reference number  1  denotes overall an external fixator applied according to the method of the present disclosure, to a long bone of a patient using only unicortical pins or screws  100 . 
         [0034]    The external fixator may comprise in particular a bar  2 , known per se, which may be fixed to the bone by means of two anchoring groups  20  which may be respectively arranged in a distal position and proximal position. 
         [0035]    Each of the anchoring groups  20  may comprise two locking devices  10 , each of which may be designed to be locked into position by two unicortical pins  100  which may be implanted into the bone of a patient. The two locking devices  10  may extend laterally, in the manner of wings, from a central connecting body  11  of the anchoring group which may also support a locking clamp  3  designed to grip the bar of the external fixator  1 . 
         [0036]    In some embodiments, the locking devices  10  may be made as modular elements which may be mounted separately on the connecting body  11 ; nevertheless, alternative embodiments may be possible in which the entire anchoring group  20  may be formed as one piece, while retaining the particularly advantageous form and functional characteristics described below. 
         [0037]    The single locking device  10  may have a substantially L-shaped main body. More specifically, the single locking device  10  may have a pin-locking arm  101  and a connection base  102  which may together form an elbow. An angle α between the direction of extension of the arm x and the direction of extension of the base y, shown in  FIG. 13 , is preferably an angle that is substantially greater than a right angle, namely between 120° and 150°. It may be noted that the pin-locking arm  101  and the connection base  102  may extend along a same plane of orientation P 1  of the locking device  10 . 
         [0038]    The pin-locking arm  101  may have at its two opposite ends two seats  101   a ,  101   b  which may be designed to lock a corresponding number of unicortical pins  100 . This locking action may be performed by the locking means  103  described below. 
         [0039]    The locking means  103  may comprise, in particular, two deformable spheres  103   a ,  103   b , one of which is shown separately in  FIG. 17 , which may be provided with a diametral insertion channel  1031  that defines the actual seat  101   a ,  101   b  for the unicortical pins  100 . The deformable spheres may have a plurality of incisions that may cross the sphere in a planar manner passing through the insertion channel  1031 ; the incisions may lead alternately into one or the other of two opposite openings of the insertion channel  1031 . Because of the incisions, the sphere may become deformed when it is compressed along the axis of the insertion channel. Thus, the insertion channel  1031  may be constricted locally, by which the unicortical pin  100  housed therein may be locked. 
         [0040]    The aforementioned deformable spheres  103  may be housed between an elongated impression  101   c , formed along the upper surface of the pin-locking arm  101 , and a pressure plate  103   a  shaped to counter the opposite impression  101   c . In particular, both the pressure plate  103   c  and the impression  101   c  may have smooth through-holes  1011  at their ends; the two deformable spheres  103  may be locked between two smooth through-holes  1011  situated opposite each other. The insertion channel  1031  of the spheres  103  may be accessible via the smooth through-holes  1011  so as to allow the introduction of the unicortical pin  100 . 
         [0041]    A pressure plate  103   c  may be connected to the impression via tightening means  103   d  which may take the form of a screw. The shank of the screw may be inserted into a central through-hole  1010   a  of the pressure plate and then into an opposite central hole  1010   b  formed in the bottom of the impression  101   c , on the outside of which it may engage with a nut. Resilient setting means  103   e  may also be arranged between the pressure plate  103   c  and the impression  101   c , which may be formed in particular by two helical springs that are compressed between the two elements and may be retained inside oppositely arranged depressions  1012  of the impression  101   c  and the pressure plate  103   c.    
         [0042]    The springs, which may be arranged in intermediate positions between the deformable spheres  103  and the screw, may oppose the tightening action of the latter. Such arrangement may allow the deformable spheres  103  to be deformed and the unicortical pins  100  to be locked inside them. 
         [0043]    It should be noted that when the compression plate is not clamped, the deformable spheres  103  may be rotatable inside their seat, such that the surgeon may modify as required the orientation of the inserted unicortical pins  100 . Tightening the head of the screw  103   d  eliminates this degree of rotational freedom. 
         [0044]    The deformable spheres  103  may have, in one of the openings of the insertion channel  1031 , a raised cylindrical edge  1032  which, once inserted inside the smooth through-hole  1011 , may limit the rotational movement of the element, while may allow access to the insertion channel  1031 . 
         [0045]    In some embodiments, the deformable spheres  103  may allow the direction of the unicortical pins  100  to be varied with respect to the axis perpendicular to the plane of orientation P 1  by about 20°. 
         [0046]    The connection base  102  has at its free end a fastening point  102   a  suitable for connection to the connecting body  11 . 
         [0047]    Moreover, the connecting body  11  may have, on both sides, two alternative fastening seats  110   a ,  110   b  for the connection of the fastening point  102   a.    
         [0048]    The fastening point  102  of the locking device  10  may present an enlarged portion through which a fastening hole  102   c  may passes and, on the opposite side of the enlarged portion, a projecting tenon  102   b ; on the other hand, the fastening seats  110   a ,  110   b  may present a depression or mortise  110   c  shaped to match the tenon  102   b , and a fastening hole  110   d  formed in the bottom of the mortise  110   c.    
         [0049]    When the tenon  102   b  is correctly inserted into the mortise  110   c  of one of the fastening seats  110   a ,  110   b , the two fastening holes  102   c ,  110   d  may be aligned so that a threaded connection element  104  that fixes the locking device  10  to the connecting body  11  may pass through them. 
         [0050]    The connecting body  11  may have a structure that is substantially symmetrical with respect to its median plane M. Said connecting body  11  may have a cusp portion  111  at the front with opposite inclined surfaces that are symmetrical with respect to said median plane M, and at the rear a hinge portion  112 , which will be described below. 
         [0051]    Both the inclined surfaces of the cusp portion  111  have a top section with an inclination greater than the horizontal and a bottom section with a smaller inclination. The first fastening seat  110   a  may be formed on the first section and the second fastening seat  110   b  may be formed on the second section. Thus, depending on whether the locking device  10  may be connected to the first fastening seat  110   a  or to the second fastening seat  110   b , two different inclinations of the plane of orientation P 1  with respect to the median-plane M may be obtained. Consequently, also the inclination of the preferential plane of orientation P 2  of the unicortical pins  100  may be modified, i.e. the plane on which the pins lie, with due allowance for any adjustments performed by means of the deformable spheres  103   a ,  103   b.    
         [0052]    The inclination imparted to the fastening seats  110   a ,  110   b  in the present disclsoure may be such that, by associating both locking devices  10  with the respective first seat  110   a , an angle between the two planes of orientation P 1  may be created that is smaller than a right angle; on the other hand, by associating the locking devices  10  with the second seat  110   b , an angle between the two planes of orientation P 1  may be obtained that is greater than a right angle. The first configuration may be particularly suitable for small-size bones (e.g., tibial mounting), while the second configuration may be suitable for large-size limbs (e.g., femoral mounting). 
         [0053]    The hinge portion  112  of the connecting body  11  may allow for articulation, around an axis of rotation r 1  perpendicular to the median plane M, of a locking clamp  3 . 
         [0054]    The hinge portion  112  may define in particular a cylindrical seat  1120  intended to define interiorly an articulation hinge  33  of the locking clamp  3 . A threaded element, with a shank which defines the pin  33   a  of the hinge  33  and a head which acts as a cover for the cylindrical seat  1120 , is in fact screwed laterally into the cylindrical seat  1120 . A shank  30  of the locking clamp  3 , which may comprise an eyelet end  30   a , which may embrace the aforementioned pin  33   a , may also be inserted, via an upper groove  1121 , inside the cylindrical seat  1120 . 
         [0055]    Outside of the cylindrical seat, the shank  30  may pass through, in succession, an intermediate element  34 , slidably movable along an outer cylindrical surface of the hinge portion  112 , and two jaws  32  designed to grip in a known manner the bar  2  of the external fixator. A splined coupling IM may be formed between the bottom jaw  32  and the intermediate element  34  that ensures restriction of rotation when the two parts are clamped against each other. The free end of the shank  30  may be threaded and a lock nut  31  may be screwed onto it. 
         [0056]    When the abovementioned group is not clamped, adjustments both around the axis of rotation r 1  of the hinge and around the axis r 2  of the shank  30  may be possible. Tightening the lock nut  31  may cause the entire group to be pressed together and performs the triple function of locking the bar  2  between the jaws of the clamp  3  and blocking the two abovementioned rotational axes. In particular, the axis of rotation r 1  may be blocked by the friction between the intermediate element  34  and the outer cylindrical surface of the hinge portion  112 , and the axis of rotation r 2  may be blocked by the locking action of the splined coupling IM. 
         [0057]    Having described individually the single elements which make up the anchoring groups  20  of the external fixator  1 , description is now provided below for the different possibilities of assembling them in order to obtain different configurations of the said fixator. 
         [0058]    First of all, the locking devices  10  may be constructed in two configurations which may be a mirror image of each other, namely a configuration oriented to the right of the connection base  102  and a configuration oriented to the left of the connection base  102 . 
         [0059]    The external fixator  1 , which by nature is modular, may comprise both right-hand and left-hand locking devices  10  which may be used alternatively by the surgeon in the field depending on the actual operating requirements. 
         [0060]    Thus, depending on the locking devices chosen, each anchoring group  20  may be mounted in three different configurations: a U configuration, in which the two locking devices  10  may both be oriented in the same direction, away from the locking clamp  3  of the anchoring group  20 ; an M configuration, in which the two locking devices  10  may both be oriented in the direction of the locking clamp  3  of the anchoring group  20 ; and an S configuration, in which the locking devices  10  are oriented in opposite directions. 
         [0061]    With reference to the enclosed figures:  FIG. 1  shows an external fixator  1  in which both anchoring groups  20  have a U configuration; in  FIG. 2  both anchoring groups  20  have an S configuration; in  FIGS. 3 and 4  the proximal mounting group  20  has a U configuration and the distal group has an M configuration, i.e. in a position where the pin-locking arms  101  point in a distal direction and proximal direction, respectively. 
         [0062]    The various configurations described above may be used alternatively by the surgeon, depending on the specific operating requirements and the morphology of the fractured bone. In particular, with the S configuration two unicortical pins  100  may be arranged in the vicinity of the fracture site, thereby increasing stability. It is a known fact that the relative spacing of the screws may improve the stability of an external fixator  1 . 
         [0063]    In the case where additional stability is required, further unicortical pins  100  may be added, being directly fixed to the bar  2  by means of one or more bar/pin clamps  4  of the type known in the art. 
         [0064]    In some embodiments, methods for applying an external fixator  1  are provided. Methods may comprise the following steps: 
         [0000]    preparing the first anchoring group  20 , for example the distal anchoring group of the type described above, where necessary mounting it in the configuration most suitable for the intervention according to the modes described above;
 
inserting unicortical pins  100  in at least three of the seats  101   a ,  101   b  (but preferably all four of them) of the two pin-locking devices  101  of the anchoring group  20 ;
 
fixing the unicortical pins  100  to the long bone of the patient, rotating them by means of a special instrument, using the seats  101   a ,  101   b  as boring guides;
 
locking said unicortical pins  100  inside the seats  101   a ,  101   b  using the special locking means  103  described above.
 
         [0065]    It should be noted that before fixing the unicortical pins  100  to the bone, they may be oriented by rotating the deformable sphere  103   a ,  103   b  in which they are inserted and then locking them in position by tightening the aforementioned locking means  103 . 
         [0066]    It should in particular be noted that the unicortical pins may have a self-tapping tip so that it may be sufficient to rotate them, associating their head with a drilling device in order to create the fixation hole in the patient&#39;s bone, whereby said hole may only penetrate the first cortex. 
         [0067]    The steps described above may then be repeated in order to fix a second anchoring group  20 , for example the proximal anchoring group; following which, by performing the adjustments along the axes r 1  and r 2  of the locking clamps  3  of the two anchoring groups  20 , they are aligned and connected to the bar  2 . 
         [0068]    As previously mentioned, in order to improve the stability of the external fixator, further unicortical pins  100 , preferably two in number, may be used, associating them directly to the bar  2  by means of bar/pin clamps  4 . 
         [0069]    It should be noted that, during mounting of the anchoring groups, owing to the L-shaped form of the locking device  10 , X-ray access to the bone site concerned in the intervention is never obstructed by the structure of the anchoring groups, so that the various parts which make up the group need not necessarily be made of radiotransparent material. 
         [0070]    It should also be noted that the non-invasive form of the anchoring group  20 , in particular in its U configuration with the opening directed towards the bone end, may allow for easy access of an instrument for reaming the long bone of the patient and subsequently inserting an intramedullary nail, even when the anchoring group is positioned at the point where the nail end is inserted. 
         [0071]    One of ordinary skill in the art, in order to satisfy specific requirements which may arise, may make numerous modifications and variations to the devices described above, all of which are however contained within the scope of protection of the disclosure, as defined by the following claims.