WO1997030650A1

WO1997030650A1 - External fixator apparatus for bone surgery

Info

Publication number: WO1997030650A1
Application number: PCT/EP1996/004713
Authority: WO
Inventors: Michael Saleh; Michael Neal; Daniele Venturini
Original assignee: Orthofix S.R.L.
Priority date: 1996-02-21
Filing date: 1996-10-30
Publication date: 1997-08-28
Also published as: AU7561696A; ITVR960018A0; IT1289078B1; ITVR960018A1

Abstract

An external fixator for bone surgery including a plurality of pins (V, F) which can be inserted in a bone fragment (M', M'') so that at least one end thereof projects outwardly from the peripheral muscle tissues, a rigid frame arranged to stably support the pins at their outer end while keeping them at an adjustable distance from one another. The frame includes at least a first element (2; 102) adapted to removably and selectively clamp a first group of pins (V) which extend from one side with respect to a first bone fragment (M'), at least a second element (3; 103, 104) arranged to clamp a second group of pins (F) which extend from one side to the other of the bone and, connecting elements (31; 104, 105) extending between at least the first and second elements in order to change their orientation and their distance from one another.

Description

EXTERNAL FIXATOR APPARATUS FOR BONE SURGERY

DESCRIPTION

Field of application The present invention relates to an external fixator for bone surgery, i.e. for reducing tibia fractures in the periarticular joint area of the knee for adjustment of equinus foot deformities.

Prior art

External fixators have been used in bone surgery for a long time for stabilising fractures or for eliminating traumatic and/or congenital deformations.

Such apparatus essentially consist of a plurality of pins which can be inserted into bone fragments in such a way as to have an end coming out the muscle and the epithelial tissues, which pins are stably and removably secured to an external rigid structure of suitable configuration. Among external fixators a distinction is made between two large families, i.e. that of monolateral apparatuses and that of the circumpherential or bilateral apparatuses.

Examples of monolateral fixators are the external axial fixators, such as those of the series 10000 manufactured by Orthofix of Bussolengo, Italy, that substantially consist of a pair of end clamps connected to a central body of adjustable length by means of lockable ball joints which make it possible to set them.

Such external axial fixators have the advantage of being very easily and rapidly mounted owing to the fact that the screws must be applied to one side only and are simple to fix thanks to a large contact surface offered by the two halves of the clamps.

Moreover, the screws have dimensions such as to allow the transmission of bending and shearing loads to the bone tissues.

Mechanical stress exerted by the screws, however, are highly unbalanced, which makes it advisable not to insert them near the diaphysary ends, where the tissue has a lower density, and near the articulations where the risk of damaging the neurovascular tissues is higher. The fixators of circumpherential or bilateral type have as a first prototype the model of fixator designed and first employed by llizarov, which fixator comprises at least two rigid support rings peripherally arranged with respect to the bone fragments to which it is possible to removably fix at diametral positions one or more Kirschner wires inserted in the bones and having both their ends projecting out from the muscle and the epithelial tissue of the limb.

The support rings can be mutually connected by longitudinal rods or bars adjustable in length and inclination so as to vary their mutual distance and orientation.

The bone wire used in such circumferential fixators has the advantage of transmitting stresses in a perfectly balanced way and of being insertable into more delicate or osteoporotic bone tissues in periarticular areas with smaller risk of affecting highly vascolarized tissues. Owing to the reduced diameter of the wires it is possible to increase their number so as to distribute the circumferential load in a uniform manner.

On the other hand, each single wire can apply a concentrated load to the bone tissue into which it is inserted, and thus it can cut it or affect its adhesion. This reduces endurance and stability of the device with respect to an external monolateral fixator.

Finally, the operation of inserting wires into through holes in the bones and that of securing their ends to the rings is rather complicated and time consuming, and requires high skill and rather long operational times.

Fixator devices of a hybrid type have also been designed in which axial structures supporting one end of radial screws or pins extending out of the bone and the epithelial tissue are anchored to the support rings mutually connected by means of bar that can be elongated and bent.

Such devices, however, have not eliminated the difficulties of inserting the wires and in some cases have contributed in making more difficult and longer the mounting operations.

Brief summary of the invention A main object of the present invention is to eliminate or at least to mitigate the drawbacks referred to above by providing an external fixator apparatus which makes it possible to simplify the operations of application thereof and to reduce the operational times with respect to the conventional circumferential or hybrid devices.

A further object is that of providing an external hybrid fixator which makes it possible to obtain a more balanced partly circumpherential distribution of the loads with respect to the conventional monolateral devices.

According to one preferred aspect of the invention, there is provided an external fixator device for bone surgery, comprising a plurality of pins that can be inserted into a bone fragment such that at least one end thereof projects outside the peripheral muscle tissues, and a rigid frame arranged to stably support the said pins at their outer ends while keeping them at an adjustable distance from one another. The device is characterised in that the said frame comprises at least a first element arranged to removably and selectively clamp one end of a first group of pins extending from one side only with respect to the bone, a second element arranged to clamp a second group of pins extending from opposite sides with respect to the bone, and connecting means extending between the said first and second elements to change their orientation and their mutual distance.

Brief description of the drawings

Further features, objects, and advantages of the invention will be better understood from the following detailed description of some preferred but not exclusive embodiments of an external fixator device according to the invention, illustrated by way of non limiting example with reference to the accompanying tables of drawings, in which:

Figure 1 shows a general perspective view of a first embodiment of a device according to the invention applied to an elongate bone;

Figure 2 shows a perspective view of a portion of the device of Fig. 1 ;

Figure 3 shows a section view of a ring of Fig. 1 taken along the section line III- III;

Figure 4 shows a section view of a detail of Fig. 3 taken along the section line

IV-IV;

Figure 5 shows an assembled side view of a clamp of the device of Fig. 1 ; Figure 6 shows a plan view of the detail of Fig. 5;

Figure 7 shows a side view of a portion of the clamp of Fig. 5;

Figure 8 shows a section view of the portion of Fig. 7 taken along the section line VIII-VIII;

Figure 9 shows a lateral view of a clamp of the device of Fig. 1 ; Figure 10a shows a partially sectioned front view of a wire clamp mounted on the device of Fig. 1 ;

Figure 10b shows a side view of the wire clamp of Fig. 10a;

Figure 10c shows a lateral view of the wire clamp of Figs. 10a and 10b;

Figure 10d shows a locking pin for a bone wire inserted in the clamp of Figs. 10a, 10b, 10c;

Figure 1 1 shows a section view along a meridian plane of the ring of Figure 1 in the phase in which a bone wire is being inserted;

Figure 12 shows a front view of spacing bar clamp of the device of Fig. 1 ;

Figure 13 shows a side view of the clamp of Fig. 12; Figure 14 shows a diagrammatic axonometric view of a second embodiment of the fixator device according to the invention;

Figure 15 shows a diagrammatic axonometric view of a modification of the fixator device of Fig. 14;

Figure 16 shows a partly sectioned view of a 5/8 ring which can be used with both the device of Fig. 1 and that of Figs. 14 and 15;

Figure 17 shows a non-sectioned side view of the element of Fig. 16;

Figures 18 and 19 show section views of a detail of Fig. 1 6 taken along section

Iines XVIII-XVlll and XIX-XIX respectively;

Figure 20 shows a partly sectioned view of a U-shaped bracket which can be used in the device of Figs. 14 and 15;

Figure 21 shows a side view of the bracket of Fig. 20; and

Figures 22 and 23 show section views of the bracket of Fig. 20 taken along the section Iines XXII-XXH and XXIII-XXIII respectively.

Detailed description of the preferred embodiments

With reference to Figures 1 to 14, a fixator device according to the invention, generally indicated with the reference numeral 1 , comprises a first side element 2 and a second circumferential element 3.

Element 2 comprises an elongated monolateral clamp which is illustrated in more detail in Figures 5 to 8. The clamp 2 comprises two parts or jaws 4, 5 which are substantially semielliptic in cross section and mutually articulated by means of a hinge 6. The parts 4, 5 on their facing surfaces are provided with a series of transverse seats or grooves 7 having a substantially semicircular cross section and arranged to cooperate with the ends projecting out of the epithelial tissue of a first group of screws V which can be inserted into a bone stump M' with substantially coplanar axes. The two parts 4, 5 can be mutually tightened through a socket head screw 8 by means of a suitable wrench. Part 4 has a lower extension 9 provided with side lugs having slotted holes 10 for connection to the second support element 3.

The support element 3 is illustrated in greater detail in Figs. 3, 4 and 1 1 and comprises an annular rigid structure having a substantially U-shaped cross section overturned by 90° and an inwardly directed rounded end with parallel flat surfaces. The ring 3 is formed with a series of radial holes 1 1 which are slotted in circumferential direction and delimit stiffening ribs 12, as well as a series of axial holes 13. According to the invention the annular structure comprises two half rings 3' , 3" connected to each other at their ends by means of snap coupling pins 14, 15.

More particularly, the pin 14 is secured to the half ring 3' by means of a transverse locating peg 1 6 extending through a slotted hole 1 7 and has a ground end thereof that can be snugly fitted into a hole bored in the opposite half ring 3".

The pin 1 5 is secured to the half ring 3" by means of a locating peg 18 and is removably snap coupled to the half ring 3' through a ball 19 seated in a recess and urged outwards by a spring 20 to snap enter a bore 21 formed in the half ring 3' .

Thus, the annular support structure 3 can be positioned around the patient's limb without the need of inserting it from one end thereof, but by simply arranging one of the two half rings 3', 3" below the patient's limb in the desired position and successively snap coupling it with the other half ring by direct insertion with a very simple operation.

The ring 3 supports in diametral position one or more stainless steel Kirschner's wires F inserted into a second bone fragment M" of the fracture so as to have both its ends coming out from both sides of the limb.

Advantageously, expansions E, e.g. frustoconical in shape, can be provided towards one of the ends of the wires F and can be inserted into flared limit recesses formed in radial bores of the ring 3. The other end of the wire F can be locked and tightened by means of a suitable clamp 23 illustrated in more detail in Figs. 10a, 10b, 10c and 10d comprising two opposite portions 24, 25 provided with dovetail lugs that can cooperate with the surfaces of the ring 3 by means of a screw 26.

A pin 28 is rotatably mounted in the clamp 23 and has a through hole 29 for the insertion therein of the free end of the wire F with the expansion E abutting against the ring 3. By rotating the pin 28 the wire F is tightened and held within the through hole 29. The end in excess of the wire can be cut to size by the surgeon.

The clamp 2 is suitably anchored to a second annular element 30 similar to the first element 3 and possibly having different dimensions for fitting to the dimensions of the limb so as not to interfere with the limb.

More particularly, the support element 30 may comprise easily couplable half rings 30', 30" or can be incomplete, e.g. extending through an arc of about 5/8 of a circumference so as to be inserted onto a limb without problems thereby avoiding subsequent interference, e.g. at a joint.

Thus, the clamp 2 can be secured to the annular element 30 by means of simple screws extending through slotted bores 10 so as to be directed towards the annular element 3 in a direction substantially parallel to the axis of the two elements.

The rigid connection between the two elements 3 and 30 is obtained by means of three or more bars 31 comprising threaded rods provided with one or more articulated joints 32 illustrated in more detail in Figs. 12 and 13 and adjustable extensions 33. The joints 32 can be locked in predetermined angular positions through knobs 33 having a socket head.

The embodiment of the device according to the invention shown in Figure 14 is generally indicated with the reference numeral 101 and is particularly, although not exclusively, indicated for stabilisation of fractures of the foot and the correction of deformations occurring in that area.

The device 101 differs from the previous one in that the clamp member 102 is directly connected to a second arcuate element 103 and a third bracket element 104 through respective bars 105, 106 and lockable joints 107. As shown in Figs. 16 to 23 the annular elements 103, 104 are formed with circumferential holes through which Kirschner's wires can extend and axial holes for securing the spacer bars or rods 105, 106 or their respective joints 107.

Also in this case the clamp 102 is arranged to secure a first group of bone screws not illustrated in the drawings and extending out from one side only of a bone fragment, and at its free end can be provided with a ball joint

108 for its connection to the main body of an axial fixator, e.g. of the series

10000 manufactured by Orthofix.

The two arcuate elements 103, 104 are arranged for anchoring Kirschner's wires to a second bone fragment so as to have ends extending out from opposite sides with respect thereto.

The embodiment diagrammatically shown in Fig. 15 differs from that of Fig. 14 substantially in that further stiffening bars or rods 109 which connect the two elements 103 and 104 are provided. Operatively, the surgeon inserts the first group of screws V into the first bone fragment in aligned positions by using the same clamp 2, 102 as a drilling jig. Then, after having secured the clamp 2, 102 to the screws V, he connects the same to the complete annular element 3 or the incomplete annular element 103, 104 by means of rods 31 , 105, 106. Finally, he forms in the other bone fragment bores for inserting Kirschner's wires to be secured to the said annular elements through joints and connectors by adjusting by means of X rays their relative position and inclination to obtain the reduction of the fracture or the correction of the deformation.

Although the invention has been illustrated with specific reference to the accompanying drawings, the same covers any variation and modification within reach of a person skilled in the art provided that it falls within the scope of the accompanying claims.

Claims

1 . An external fixator device for bone surgery, comprising a plurality of pins (V, F) that can be inserted into a bone fragment (M\ M") such that at least one end thereof projects outside the peripheral muscle tissues, and a rigid frame arranged to stably support the said pins at their outer ends while keeping them at an adjustable distance from one another, characterised in that the said frame comprises at least one first element (2; 102) arranged to removably and selectively clamp one end of a first group of pins (V) extending from one side only with respect to a first bone fragment, at least one second element (3; 103, 104) arranged to clamp a second group of pins (F) extending from opposite sides with respect to the bone, and connecting means ((31 ; 104, 105) extending between at least the said first and second elements to change their orientation and their mutual distance.

2. An external fixator device as claimed in claim 1 , wherein the said first element (2; 102) is an elongate clamp that can be located substantially parallel to the bone fragment (M'), the said clamp (2; 102) comprising two opposite portions (4, 5) provided with transverse seats (7) formed in the facing surfaces in order to clamp the said first group of pins (V) in positions substantially aligned to one another.

3. An external fixator device as claimed in claim 1 , wherein the said first group of pins comprises two or more bone screws (V) with threaded ends arranged to be inserted into the bone tissue.

4. An external fixator device as claimed in claim 2, wherein the said clamp (102) is provided with an orientable ball joint (108) at a distal end thereof.

5. An external fixator device as claimed in claim 1 , wherein the said second element (3; 103) is arranged to be peripherally located about the limb to be treated in a transversal plane with respect to the axis thereof and is substantially fully or partly circular in shape to avoid interference with the limb.

6. An external fixator device as claimed in claim 5, wherein the said second element (3; 103; 104) is substantially U-shaped in cross-section and has transverse stiffening members (12), radial holes (1 1 ), and longitudinal holes (13).

7. An external fixator device as claimed in claim 1 , wherein the said second group of pins comprises one or more Kirschner wires (F) removably anchored in diametrically opposite positions to the said second element.

8. An external fixator as claimed in claim 7, wherein the said Kirschner wires (F) have at one end thereof a substantially flared extension (E) arranged to be inserted into a correspondingly shaped seat in one of the radial holes (1 1 ) of the said second element (3).

9. An external fixator device as claimed in claim 2, wherein the said first clamp element (2) is removably connected to the said second element (3) by means of a plurality of longitudinal spacer bars or rods (31 ) arranged to be positioned outside and peripherally to the muscle tissue of the limb.

10. An external fixator device as claimed in claim 9, wherein one of the opposite portions (4) of the said clamp element (2) has a base (9) arranged to be secured to a third element (30) similar to, and substantially parallel with, the second element (3) and connected thereto through the said rods (31 ).

1 1 . An external fixator device as claimed in claim 10, wherein the said longitudinal spacer rods (31 ) have means (33) for adjusting their length.

12. An external fixator device as claimed in claim 11 , wherein the said rods have one or more lockable joints (32) in a median position in order to set the said elements one with respect to the other.

13. An external fixator device as claimed in claim 12, wherein the said first element (102) is operatively connected to a second element (103) that is substantially circular or partly circular in plan view and a third substantially U- shaped bracket element (104), the said second (103) and third (104) elements being arranged to be positioned peripherally the ends of a limb to support at least one Kirschner wire (F).

14. An external fixator device as claimed in claim 12, wherein the said second (103) and third (104) elements are mutually connectable by means of stiffening rods (109) adjustable in length.

15. An external fixator device as claimed in claim 10, wherein the said second and third complete annular elements (3, 30) comprise two substantially semicircular portions (3', 3") which can be mutually coupled at their ends by means of ball and seat coupling means so as to facilitate positioning of the elements around the limb.

16. An external fixator device as claimed in claim 13, wherein the said clamp has at a free end thereof a ball joint for connection to an extendible main body of a monolateral axial fixator.