WO2016159901A1

WO2016159901A1 - Lambda fixator

Info

Publication number: WO2016159901A1
Application number: PCT/TR2015/000301
Authority: WO
Inventors: Ibrahim Deniz AKCALI; Huseyin MUTLU; Ercan AVSAR; Ahmet Aydin
Original assignee: Akcali Ibrahim Deniz
Priority date: 2015-04-03
Filing date: 2015-08-03
Publication date: 2016-10-06
Also published as: JP6556247B2; EA201790793A1; JP2018509961A; CN107530107A; EA034003B1; CN107530107B

Abstract

Lambda fixator is fundamentally composed of two rings, which have at least double-row holes, connected to each other by means of three main structural elements called λ -module. There are altogether four different kinds of λ -module, two of them being basic types, the others being their subclasses. In the first basic type, there are three spherical joints at the ends, a simple revolute joint connecting long leg to the short leg and two screw-nut pairs for changing leg lengths. In the second basic type, there exist two spherical joints at the ends of long leg, two universal joints at the each end of the short leg and two screw-nut pairs changing leg lengths. Using only one kind of λ -module it is possible to set the fixator up in 512 different ways.

Description

LAMBDA FIXATOR

Title of the invention is "Lambda Fixator".

The invention belongs to a multidiciplinary technical area where engineering technologies and orthopaedics practice in medicine intersect.

Usage area of the invention is orthopaedics.

The subject of invention is a modular system that externally enables bringing bone fragments to desired positions in order to overcome orthopaedic problems in medicine such as extremity fractures, deformities, etc... Most commonly used tools in orthopaedic external fixation procedures are simple devices like hinges, rods and pins, and classical frame systems called pin fixator. There are various examples for this kind of frames such as unilateral, uniplanar bilateral, biplanar unilateral (Donald et. al., 1982; Seligson et. al., 1982; Fernandez, 1985; Fernandez, 1992). Despite their simple architecture, a notable disadvantage of these frames is providing the required translations and rotations to bone fragments having six degrees of freedom in space after a time-consuming and complex planning which is a great burden for orthopaedist. Proposal of ring fixator is accepted as a new step in external fixator applications as it provides controlled movement in all directions (lllizarov, 1992). In recent years, a fixator type pioneered by J.C. Taylor from US and named by him as Taylor's Spatial Frame Fixator, which is sometimes called as "hexapod" among ring fixators, has gained popularity. (Taylor et. al., 1999; Seide et. al., 2004; Simpson et. al., 2008; Taylor, 2015). There are numerous patents based on Taylor frame and showing methods facilitating usage (Austin et. al, 2004; Koo et. al., 2002). In this fixator type, two rings are interconnected by attaching six rods to twelve fixed points where six points are at top frame and six points are at bottom frame. In a previous study, it has been shown that this sort of structures cannot be used safely without singularity analysis (Akcali et. al., 2014). Besides, it is very likely that attached rods might block the fragments on fracture lines on X-ray images. In addition, there are some challenging and restrictive conditions for orthopaedists such as top and bottom rings being parallel to each other at either initial or final position, and before some of the operations it requires preplanning or premeasurement. There are other patents proposing change of architecture parameters and preloading in order to resolve undesired complexity and pollution issues in X-ray images (Karidis and Stevens., 2009; Karidis, 2009). It is reported that a system called "Storm" is put to use in England for alignment of fractured tibia and femur fragments (Ogrodnik, 2007). However, since this system is cumbersome, it confines the patient to the bed.

The problem which the invention aims to solve is to form user-friendly external fixator device alternatives which are to be utilized in the field of orthopaedics to bring together displaced bone fragments on desirable axes, which minimize the singularity issues, which tend to alleviate the burden of computation as much as possible, which leave unobstructed regions for clear-cut fragment images in X-ray films, which create multi-directional facilities that possess structural potentials and flexibilities.

Fundamentally, this invention is a modular parallel robotic arrangement with six degrees of freedom, composed by connecting two rings, one being lower the other being upper, having ordered holes placed on preferably at least two concentric circles, with three /l(lambda)-shaped structural elements namely λ- modules. A-module consists of two cylindrical parts which are defined as long and short legs. The long and short legs have both moving variable and fixed-length segments. These legs are connected to each other in such a way that the connection point is on the fixed-length segment of the long leg. It is possible to connect the one end of the long leg to the upper ring, the other end to the lower ring, and the free end of the short leg to either upper or lower ring. These basic properties allow a single A-module to connect upper and lower rings in eight different ways. The variable-length segment of the long leg may be on the upper ring side and the fixed-length segment may be on the lower ring side, or conversely the variable-length segment of the long leg may be on the lower ring side and the fixed-length segment may be on the upper ring side. Besides the fact that one end of the long leg is always connected to one of the rings while the other end is connected to the other ring, the free end of the short leg may be connected to either upper ring or lower ring from the left hand side or the right hand side of the long leg. Thus, robotic applications with three modules as an external fixator will provide 8³ = 512 different set-ups, which means a huge construction flexibility and diversity.

On the other hand, there are two basic A-module types providing six- degree-of-freedom motions to the robotic arrangement which basically result from the assembly of two rings and three λ-modules. First basic λ-module type is a structural element having spherical joints with ability of rotation about three independent axes at both ends of long leg, a simple revolute joint with one degree of freedom at the connection point of long and short legs, and a spherical joint with three degrees of freedom at the free end of the short leg, Figure 1. Second basic A-module type is a structural element having spherical joints with three degrees of freedom at both ends of long leg and universal (cardan) joints with two degrees of freedom at connection point of long and short legs and at free end of the short leg, Figure 2. In order to make sure that the parts, pieces and features of the external fixator device, the subject of this patent here, are well understood, figures listed below are given and these figures and their explanations are as follows:

Figure 1 First basic A-module type

Figure 2 Second basic A-module type

Figure 3 Second kind of first basic λ-module type

Figure 4 Second kind of second basic A-module type

Figure 5 Example of (3-6) type fixator obtained by using first basic Λ- module type Figure 6 - Example of (3-6) type fixator constructed by using second kind of first basic Λ -module type

Figure 7 - Example of (3-6) type fixator obtained by using second basic Λ- module type

Figure 8 - Example of (3-6) type fixator constructed by using second kind of second basic A-module type

Figure 9 - Upper (1) and lower (2) rings having double-row holes.

Figure 10 - Part numbered (3)

Figure 11 - Intermediate piece numbered (4)

Figure 12 - Pieces numbered (5) and (6)

Figure 13 - Parts numbered (7) and (8)

Figure 14 - Part numbered (10)

Figure 15 - Assembly of cylindrical part (10) with a nut (3) attached to its end

Figure 16 - Part numbered (11)

Figure 17 - Assembly form of the long legs of Λ -modules

Figure 18 - Intermediate connection piece number (12) used with kinds of basic A-modules

Figure 19 - (3-6) system constructed by using first kind of first A-module type

Figure 20 - (4-5) system constructed by using first kind of first A-module type

Figure 21 - (5-4) system constructed by using first kind of first A-module type Figure 22 - (6-3) system constructed by using first kind of first A-module type

Figure 23 - (3-6) system constructed by using second kind of first A- module type Figure 24 - (4-5) system constructed by using second kind of first A- module type

Figure 25 - (5-4) system constructed by using second kind of first A- module type

Figure 26 - (6-3) system constructed by using second kind of first A- module type

Figure 27 - (3-6) system constructed by using first kind of second A- module type

Figure 28 - (4-5) system constructed by using second kind of first A- module type Figure 29 - (5-4) system constructed by using first kind of second A- module type

Figure 30 - (6-3) system constructed by using first kind of second A- module type

Figure 31 - (3-6) system constructed by using second kind of second A- module type

Figure 32 - (4-5) system constructed by using second kind of second A- module type

Figure 33 - (5-4) system constructed by using second kind of second A- module type Figure 34 - (6-3) system constructed by using second kind of second A- module type

Figure 35 - (3-6) system constructed by using first kind of first A-module type with all short legs connected from the left hand side. Figure 36 - (4-5) system constructed by using first kind of first A-module type with all short legs connected from the left hand side.

Figure 37 - (5-4) system constructed by using first kind of first A-module type with all short legs connected from the left hand side.

Figure 38 - (6-3) system constructed by using first kind of first A-module type with all short legs connected from the left hand side.

Figure 39 - (3-6) system constructed by using second kind of first A- module type with all short legs connected from the left hand side.

Figure 40 - (4-5) system constructed by using second kind of first A- module type with all short legs connected from the left hand side. Figure 41 - (5-4) system constructed by using second kind of first A- module type with all short legs connected from the left hand side.

Figure 42 - (6-3) system constructed by using second kind of first A- module type with all short legs connected from the left hand side.

Figure 43 - (3-6) system constructed by using first kind of second A- module type with all short legs connected from the left hand side.

Figure 44 - (4-5) system constructed by using first kind of second A- module type with all short legs connected from the left hand side.

Figure 45 - (5-4) system constructed by using first kind of second A- module type with all short legs connected from the left hand side. Figure 46 - (6-3) system constructed by using first kind of second λ- module type with all short legs connected from the left hand side.

Figure 47 - (3-6) system constructed by using second kind of second Λ- module type with all short legs connected from the left hand side.

Figure 48 - (4-5) system constructed by using second kind of second λ- module type with all short legs connected from the left hand side.

Figure 49 - (5-4) system constructed by using second kind of second Λ- module type with all short legs connected from the left hand side.

Figure 50 - (6-3) system constructed by using second kind of second Λ- module type with all short legs connected from the left hand side.

Parts, pieces in Figures 5 and 6 have been numbered and their descriptions are given below:

(1) - Upper ring

(2) - Lower ring

(3) -Nut

(4) - Intermediate piece

(5) - Intermediate connection piece

(6) - Set-screw hole on intermediate piece number (5)

(7) - Part of spherical joint connected to screw (11)

(8) - Part of spherical joint connected to ring

(9) - Free end of the short leg of the λ-module

(10) - Hollow cylindrical part

(11) - Threaded cylindrical part (12) - Intermediate piece in Λ-module kinds

In the robotic arrangement of external fixator, first basic Λ-module type (Figure 1) may be used with rings having single-row holes; because short and long legs of the A-module, together with their axial lines, lie on a single plane perpendicular to the rotation axis of the re volute joint connecting them. Presence of short and long legs on the same plane may introduce small restrictions on length of short leg and amount of change in this length. This situation may be overcome with the second kind of first basic A-module seen in Figure 3. By letting the rotation axis of the revolute joint pass through a point on the axis of the long leg, the condition for the short leg to take on greater lengths is satisfied by this second kind (Figure 3). In this case, axis lines of short and long legs of A-module lie on two separate planes parallel to each other and simultaneously perpendicular to the rotation axis of the revolute joint. Thus no change in the joint features of the second kind (Figure 3) is made with respect to the first basic type; but a large area of maneuver is gained by shifting the short leg axis line to a line passing through a point on the long leg axis, when viewed along the rotation axis of the revolute joint, outwards in the radial direction, which is perpendicular to the long leg axis. While setting up fixator with second kind of first basic module, it will provide convenience in practice to use ring with double-row holes for connecting the free- end of short leg.

A modification similar to the one made in order to obtain second kind of first basic A-module, is applied on second basic A-module as well. Figure 4 shows the second kind of second basic A-module in which a universal joint with two degrees of freedom connecting short and long legs of the second basic A-module is shifted sideways. While broadening the maneuver area for short leg of the second basic A-module, this modification will help longer cylindrical parts to fit into this area at the same time.

Considering the system having three joints at three points of the upper ring and six joints at six points of the lower ring, namely (3-6) type, as basis, external fixator device options obtained by the use of four A-modules mentioned in Figures 1,2,3 and 4 are shown in Figures 5,6,7 and 8, respectively. In Figure 5, (3-6) type of fixator obtained by connecting upper and lower rings with three A-modules of the first basic type, in which moving variable-length segments of the long legs are on the upper ring side and short legs are all connected from the right hand side is exhibited. In Figure 6, a (3-6) type of fixator device which is constructed similarly except that the second kind of the first basic A-module is used, is seen. Examples of (3-6) type fixator devices obtained by assembling the upper and lower rings by using three first and second kinds of the second basic Λ-module type are presented in Figures 7 and 8, respectively. Details of A-modules are to be explained through the first basic type of A- module shown in Figure 1, referring to the integrity of the (3-6) type of fixator, shown in Figure 5, constructed from this module. First of all, upper (1) and lower (2) rings with double-row holes connected to each other with the first basic A- module of Figure 5 are given in Figure 9. A-module in question here is made up by assembling the long leg the length of which is adjusted by means of the nut, numbered (3), with the short leg which has similar structural features like the long leg, using the pieces numbered as (4),(5) and (6). Long leg of the A-module is connected to the upper (1) ring by means of a universal joint with three degrees of freedom consisting of parts numbered (7) and (8), and connected to lower (2) ring by means of a joint with similar properties. Free end of the short leg of the A- module with number (9) is also connected to lower (2) ring from the right hand side using a joint with three degrees of freedom. Cylindrical parts, numbered (10) and (11), reflecting the structure of long and short legs of all A-modules, are connected to each other by the nut numbered (3). The part numbered (3) shown in Figure 10 together with the cylindrical part numbered (11) on which fitting threads are cut forms a screw-nut pair, in its narrowest section, to be utilized in changing the length of the leg. The part numbered (3) has a knurled surface on its cylindrical section with largest diameter, convenient for manual rotation, and properly cut planes on its upper outside section to fit to a standard wrench, a cylindrical hole simultaneously perpendicular to the nut (3) axis and cut planes, and cylindrical space on its inner lower section in which a groove is carved to be a seat for a ring to connect nut (3) to the hollow cylindrical part (10).

The detailed drawings of the intermediate connection piece numbered (4), which on the one hand holds axis lines of the long and short legs of the A-module in the same single plane perpendicular to the rotation axis of the revolute joint and carries on itself the hole through which the pin of the revolute joint passes, on the other hand fixes the location of the revolute joint at a point on the axis of the fixed-length segment (10) of the long leg by means of a connecting bolt and nut, are shown in Figure 11. The drawing of the part numbered (5) on the short side of the revolute joint that is seated on the piece numbered (4), together with the set- screw hole numbered (6), used to connect this part to the screw end of the short leg in such a way that there is no relative rotation, is given in Figure 12. In Figure 13 the drawings of the universal joint composed of part numbered (7), which is connected to the threaded (11) end of the long leg of the λ-module by means of a set-screw in such a way that there is no relative rotation, and of a part numbered (8) that is connected to the upper ring by means of a suitable screw are shown.

The hollow cylindrical part numbered (10) which is present in structures of both long and short legs to represent the fixed-length segment is depicted in Figure 14. On the lower section of this part, there is a set-screw hole to attach a universal joint with two or three degrees of freedom, and there are two spherical grooves, on the upper sides in mutually opposite directions, into which a ball with suitable dimensions can be seated, and a ring seat so cut as to allow the nut (3) to be attached conveniently. Besides, the section on the upper end of the cylindrical part (10) is conically tapered such that nut (3) and the ring can be easily mounted. Furthermore there is a slot parallel to the cylinder (10) axis, graded according to a linear scale, used for measuring the length of the λ-module leg, Figure 14. The assembly of the hollow cylindrical part (10) with the nut (3) is drawn in Figure 15, whereby the nut (3) is fitted into its seat by means of the ring in such a way that it can rotate without being allowed to translate axially, the ball is pressed against the spherical groove on the surface of the cylindrical part (10) by a helical spring inserted in the cylindrical hole with a cap at the end, which belong to the nut (3).

The part which is present in the general structure of the long and short legs of the yl-module and which represents the moving variable-length segment is the cylindrical part numbered (11), Figure 16. On the upper end of the cylindrical part (11), on which threads fitting to those of the nut (3) are cut, a flat surface on which the end of the connecting set-screw will be seated is generated on the side of the stepped section with reduced diameter so that there is no rotation relative to the joint element to which this part is connected. On the lower end of the said part (11), there is a screw hole, drilled in the direction perpendicular to the cylinder axis, to which an indicator pin in suitable size is mounted, Figure 16.

In Figure 17, assembly form of long leg of the λ-module, which connects upper and lower rings to each other, is given as views in two mutually perpendicular directions and as a cross-section along the long axis. The three- degree-of- freedom universal joints (7) at the two ends are attached by means of a set-screw to the screw (11) in the upper side, again by means of a set-screw to the hollow cylindrical part (10) with length scale in the lower side. Additionally, there exist on the fixed-length cylindrical segment (10) of the long leg, the nut (3) attached by a ring and the intermediate connection piece, either (4) or (12), to which the short leg is connected by means of a bolt and nut. The intermediate connection piece (12) constitutes by the protruding cylinder the fixed connection axis of the two-degree-of-freedom universal joint as well as the rotation axis of the simple one-degree-of-freedom revolute joint of the second kind of the first basic yl-module, by being connected to the cylinder (10) axis, by means of a bolt and nut, to which the protruding cylinder axis is perpendicular. An indicator pin is placed at the end of screw (11) by means of a set-screw in such a way that its dimensions fit to those of the scaled slot cut on the cylinder (10). From Figure 17, it is possible to understand that rotating the nut about the axis of the cylindrical part (10) axis will translate the screw (11) connected to nut (3) along the cylinder axis and cause a length change in the variable-length segment of the long leg. The ball under the effect of the spring fulfils the task of acting as locking mechanism thus fixing leg length by being seated on the surface of the spherical groove at each time whenever the nut (3) turns half a revolution. In this way it will be possible to shorten or lengthen the leg size of the A-module with a resolution equal to half of the screw pitch.

Explanations about the structure and length change of long leg in Figure 17 are valid for the short leg as well, in case the set-screws of the three-degree-of- freedom joints at ends are demounted, instead relevant joints are mounted and the intermediate connection piece (12) in the fixed-length segment is removed. If the joints at ends and intermediate connection piece (4 or 12) are excluded, then the assembly of long and short legs is fundamentally realized by joining the hollow cylindrical part (10) with the nut (3).

Up until now, the two basic A-modules being in the first place, the common features of all four different kinds and types of A-modules have been stated. At this point, elements that are different will be explained. One of them is between the two kinds of the first basic A-module. The difference in question here is that the piece numbered (4) in Figure 5, the details of which are shown in Figure 11, is present in the first kind of A-module, whereas piece numbered (12) in Figure 6, the detailed drawings of which are given in Figure 18 is present in the second kind of the A-module. The very same piece in Figure 18 is utilized both in the two kinds of the second basic Λ-module in connecting the long and short legs to each other by evaluating it in two different positions separated from each other by 90-degree angle. This situation is clearly observable from Figures 2,4,7 and 8. One other reason for making a difference between A-modules is that despite structural similarities the universal joint with three degrees of freedom, as in the case of part numbered (8) in Figure 5, together with the connecting bolt has rotational freedom about the hole axis with respect to the ring whereas the universal joint with two degrees of freedom attached to the ends of the short leg, as observed in Figures 2,4,7 and 8 has no rotational freedom with respect to the part to which it is connected. For this purpose, the bolt connecting the joint to the ring is rigidly mounted in the case of two-degree-of-freedom universal joint, while in the case of three-degree-of-freedom universal joint a clearance is left between the contact surfaces of screw head and the ring by way of adjusting the length of the threaded portion so that relative rotation of the screw occurs with respect to the ring.

By reviewing the outstanding structural features of the basic A-modules, the differences between the classical fixator devices and the new device architectures that can be formed with the Λ-modules in question in a geometrically versatile manner will be better perceived. Fundamentally, while the first basic λ- module has three three-degree-of-freedom spherical joints, one single-degree-of- freedom revolute joint and two one-degree-of-freedom screw pairs, the second basic A-module has two three-degree-of-freedom spherical joints, two two-degree- of-freedom universal (cardan) joints and two single-degree-of-freedom screw pairs. What is common to both modules here is that three-degree-of-freedom joints are present at the ends of long legs of both modules and that there are four essential bodies which can move relative to each other in both modules. In two basic modules that can easily be perceived to be of modular structure themselves, the feature that the joints at the ends of short legs can be changed by means of suitable set-screws and by evaluating the intermediate pieces in Figures 11,12,18 will make it easy to pass from one kind to the other among the four different Λ- module kinds. This modular structure feature mentioned here will facilitate in a very grade scale setting up new fixator devices that can be constructed with the modules.

In the parallel robotic structure derived from the first module, essentially there are totally nine three-degree-of-freedom spherical joints, together with six one-degree-of-freedom screw-nut pairs and three one-degree-of-freedom revolute joints. On the other hand, there exist six three-degree-of-freedom spherical joints, six screw-nut pairs and six two-degree-of-freedom universal (cardan) joints in the parallel robotic arrangement derived from the second module. In this way, fundamentally a six-degree-of-freedom relative motion consisting of three rotations and three translations between the upper and lower rings results in the new fixator architectures formed by two modules. By this result, a facility is provided to position the bone fragments attached to the rings, as desired.

The parallel robotic arrangements obtained from the two modules within the framework of the principles set forward above make it possible for the fixator to fulfil the functions of holding the bone fragments under stable equilibrium conditions and of moving them in conformity with the medical constraints by external means through the lengthening or shortening of the leg lengths. Additionally, the effective degree of freedom of the system is equal to the number of active screw-nut pair. Thus by keeping all screw-nut pairs inactive (locked up), the system is held under stable static equilibrium.

It has been previously stated that by rotating one single λ -module about three orthogonal axes by approximately 180-degree angle in two directions, it is possible for a single λ-module to connect upper and lower rings in 2³ = 8 different ways. Departing from this fact, it is possible to obtain 8³ = 512 different set-ups for a fixator structure built by the same type of three λ-modules. If a novel device structure is to be formed from four different kinds of λ-modules, then there are totally 4³ x 512 = 32 768 different possibilities to set up a fixator. This situation makes it clear that the novel modular system subject to patenting has a very flexible structure.

As examples for the aforementioned 512 set-ups, miscellaneous fixator architectures are to be exhibited which can be formed with four different types of λ-module. In Figure 19, (3-6) system constructed by only the first kind of the first λ-module, in which all the short legs are connected to long ones from the right- hand side is depicted. If one of the spherical-universal joints (three-degree-of- freedom) at the end of the short leg in one of λ -modules of the system of Figure 19 is disconnected from the lower ring and connected to the upper ring, then (4-5) system shown in Figure 20 will result. When the two of the spherical-universal joints at the ends of the short legs of the λ-modules in Figure 19 are disconnected from the lower ring and connected to the upper ring, this time (5-4) system depicted in Figure 21 is obtained. In case all three spherical-universal joints at the ends of the short legs of all λ-modules in Figure 19 are connected to the upper ring, then (6-3) system seen in Figure 22 results. In Figures 19, 20, 21 and 22, the threaded variable-length parts of the long legs of the λ-module have been kept closer to the upper ring while their fixed-length parts are near the lower ring. When the parallel robotic structures are constructed in such a way that threaded variable length parts of the long legs are closer to the lower ring and their fixed- length parts are closer to the upper ring, although the resulting architectures will not fundamentally differ from the previous ones, the associated direct and inverse kinematic calculations will change. For this reason it is appropriate to talk about eight different ways of using every kind of λ-module in setting up a fixator system. Here only examples from those systems which possess different architectures have been selected.

Fixator device architectures which are called (3-6), (4-5), (5-4) and (6-3) systems and have spherical-universal joints at three, four, five and six points on the upper ring, and spherical-universal joints at six, five, four and three points on the lower ring, respectively, with all the λ-modules being of second kind of the first type, in which all the short legs are connected to the long ones from the right- hand side, are exhibited in Figures 23,24,25,26 respectively. Those fixator device architectures which are called (3-6), (4-5), (5-4) and (6-3) systems and have spherical-universal joints at three, four, five and six points on the upper ring and spherical-universal joints at six, five, four and three points on the lower ring, respectively, with all the λ -modules being of the first kind of the second type, in which all the short legs are connected to the long ones from the right-hand side, are shown in Figures 27, 28, 29 and 30, respectively. If the procedure of setting up fixator is applied to the case in which the all short legs are connected to the long ones from the right-hand side for the second kind of the second type of λ-module, then the fixator device architectures that result therefrom and are called (3-6), (4- 5), (5-4) and (6-3) systems can be seen in Figures 31,32,33 and 34, respectively. In case the procedure of constructing the fixator device is applied to the first kind of the first type of λ-module in which the short leg is connected to the long one from the left-hand side in such a way that three, four, five and six connection points on the upper ring and six, five, four and three connection points on the lower ring, respectively, are formed, the resulting device architectures, which are referred to as (3-6), (4-5), (5-4) and (6-3) systems in that order are exhibited in Figures 35, 36, 37, 38, respectively. When the construction procedure is implemented utilizing the second kind of the first type of λ-module, all other conditions remaining the same, fixator device architectures called (3-6), (4-5), (5- 4) and (6-3) systems, which are depicted in Figures 39, 40, 41 and 42, respectively, will result. The construction procedure, when implemented with the first kind of the second type of λ -module under the same other conditions, is to lead to the fixator device architectures which are referred to as (3-6), (4-5), (5-4) and (6-3) systems depicted in Figures 43, 44, 45, 46, respectively. If the λ-module with which the construction procedure is to be implemented leaving all other conditions same is selected as the second kind of the second type, then fixator device architectures called (3-6), (4-5), (5-4) and (6-3) systems seen in Figures 47,48,49 and 50, respectively, will result.

The λ-modules and the external fixator which is made up of these and thus has a very flexible structure possess very many structural superiorities over the Taylor's Spatial Frame. First of these is that the system subject to the patent has a structure connecting the upper and lower rings at a total number of nine points against the fact that Taylor's Spatial Frame has a structure connecting the two rings at a total number of twelve points. The meaning of this in orthopaedical practice is that Taylor's system is set up by using more joints in the assembly process requiring more time and effort whereas the new system subject to patent is set up by less time and effort. Another superiority of the new system with a modular structure is that Taylor's system has only one single set-up while with only one kind of one type of λ-module there is the possibility of having 512 different set-ups and by the use of 4 different modules there are altogether 32 768 different set-ups. One of the most important advantages of the new fixator subject to the patent is that the majority of potential risks of singularity imbedded in the structure of Taylor's Spatial Frame does not exist in the new system. For instance, the probability of occurrence of parallelogram formation, which renders the system an unstable equilibrium position during any phase of the treatment process

6x5

in the structure of Taylor's system involves -y- = 15 planes where as the number

3x2

of such planes in the new system is only— =3. Likewise the probability of having singular configuration of frame in which four directions of forces effective on the distal ring pass through a common point during any phase of the treatment involves——— = 15 cases, such probability in the new system is simply zero. If in the new system, the simple measure of taking the radii of the upper (1) and lower (2) rings unequal is put into effect, and also at the beginning only three pairs of long legs are so constructed not to contain any parallelogram, then the risk of running into undesired singularity is reduced to zero. Taylor's Spatial Frame, the general structure of which resembles (6-6) type of Stewart Platform, requires in its analytically exact solution a huge amount of computation (Dhingra et.al.,2000;Lee et.al.,2001), whereas the new system subject to the patent involves relatively very small amount of computation due to fact that it can be solved precisely by reducing it to (3-3) type of Stewart Platform where amount of computation has been shown to be reasonable (Akcah and Mutlu,2006).

The probability of coincidence of the images of bone fragments with those of the frame members is very low in the new system subject to the patent due to the fact that there are only three long legs whereas the probability of overlapping of six leg images on the bone images is high at the fracture site simply because of the presence of the six legs in Taylor's system. Besides, since there are 512 different set-ups of the fixator based on one type of λ-module making it easy to pass from one set-up to the other due to its modular structure, it is very easy to obtain unobstructed regions where clear images can be produced. Conclusively, it can be said that with the external fixator alternatives subject to the patent, serving as externally controlled mechanical means, in orthopedical problems such as alignment of bone fragments on their anatomical axes, correction of bone deformities and bone lengthening processes, a great vision of use and convenience, which will make available several solution facilities far away from singularity issues, with precise calculation ability based on little volume of computation, which secures areas of unobstructed images in X- ray films by presenting very many opportunities of different set-ups which possess structural flexibility due to the presence of less number of parts, are provided to overcome the orthopedical problems.

References

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Claims

Invention is an external fixator characterized by the fundamental feature of being six-degree-of-freedom modular parallel robotic arrangement composed by connecting two rings, one upper (1) the other lower (2), which have holes placed orderly on, at least preferably two, concentric circles, by three structural elements, named λ-module , constructed in the form of λ (lambda).

λ-module mentioned in claim 1 is characterized by the main feature that it is constructed by joining cylindrical parts, which are defined as long and short legs and have both fixed-length (10) and moving variable-length (11) segments, to each other at a point located on the fixed-length segment of the long leg.

λ-module of claim 1 and claim 2 is further characterized by the feature that it can connect upper (1) - lower (2) rings of claim 1 in eight different possible ways whereby the variable-length segment (11) of the long leg can be on the upper ring side while the fixed-length (10) segment is on the lower ring side, or the variable-length segment (11) can be on the lower ring side while the fixed-length (10) segment is on the upper ring side, and additionally the short leg can be joined to the long leg from the left-hand or right-hand side, and besides the free end of the short leg can make a joint with the upper or lower rings.

The parallel robotic arrangement of claim 1 is characterized by another feature that it is possible, by the use of the feature expressed in claim 3, to set it up in five hundred and twelve (512) different ways due to the fact that its structure has three λ-modules.

Consistent with claims 2,3,4, the first basic type of the λ-module making up the modular parallel robotic arrangement of claim 1 is characterized by the main feature that it is a fundamental structural element in which there are two spherical joints (7,8) with rotational capabilities about three independent axes, one at each end of the long leg, there is one one-degree- of-freedom simple revolute joint at the point where the long and short legs are connected to each other, there is another three-degree-of-freedom spherical joint at the free end of the short leg, and there are two screw-nut pairs , one at each moving variable-length segment of the long and short legs.

6. Consistent with claims 2,3,4, the second basic type of the λ-module making up the parallel robotic arrangement of claim 1 is characterized by the main feature that it is a fundamental structural element in which there are two three-degree-of-freedom spherical joints at the two ends of the long leg, there are two two-degree-of-freedom universal (cardan) joints, one at the free end of the short leg and the other at the point of connection with long leg, and there are two screw-nut pairs at moving variable-length segments of both long and short legs.

7. Consistent with claims 2,3,4, the second kind of the first basic type of λ- module making up the parallel robotic arrangement of claim 1 is characterized by the main feature that it lets one gain a broader area of maneuver by shifting the short leg axis line, out of long and short axis lines which lie in the same plane of the first basic type of λ-module of claim 5, to a line passing through a point on the long leg axis, when viewed along the rotation axis of the revolute joint, outwards in the radial direction, which is perpendicular to the long leg axis.

8. Consistent with claims 2,3,4, the second kind of the second basic λ- module making up the parallel robotic arrangement of claim 1 is characterized by the main feature that it broadens the area of maneuver of the short leg in the second basic λ-module described in claim 6 by shifting the universal joint at the connection point of long and short legs, outwards in the radial direction, perpendicular to long leg axis.

9. The parallel robotic arrangement set up, consistent with claim 1, by ways the details of which are given in claim 3, using the λ-module with its main feature given in claim 2, the first kind of the first type (first basic type) defined in claim 5 and/or the first kind of the second type (second basic type) explained in claim 6 and/or the second kind of the first type explained in claim 7 and/or the second kind of the second type explained in claim 8 is characterized by the feature that it is possible to obtain a fixator set-up, called (3-6) type, in which there are three joints at three points on the upper (1) ring, and there are six joints at six points on the lower (2) ring.

10. The parallel robotic arrangement set up, consistent with claim 1, by ways the details of which are given in claim 3, using the λ-module with its main feature given in claim 2, the first kind of the first type (first basic type) defined in claim 5 and/or the first kind of the second type (second basic type) explained in claim 6 and/or the second kind of the first type explained in claim 7 and/or the second kind of the second type explained in claim 8 is characterized by another feature that it is possible to obtain a fixator set-up, called (4-5) type, in which there are four joints at four points on the upper (1) ring, and there are five joints at five points on the lower (2) ring.

11. The parallel robotic arrangement set up, consistent with claim 1, by ways the details of which are given in claim 3, using the λ-module with its main feature given in claim 2, the first kind of the first type (first basic type) defined in claim 5 and/or the first kind of the second type (second basic type) explained in claim 6 and/or the second kind of the first type explained in claim 7, and/or the second kind of the second type explained in claim 8 is characterized by another feature that it is possible to obtain a fixator set-up, called (5-4) type, in which there are five joints at five points on the upper (1) ring, and there are four joints at four points on the lower (2) ring.

12. The parallel robotic arrangement set up, consistent with claim 1, by ways the details of which are given in claim 3, using the λ-module with its main feature given in claim 2, the first kind of the first type (first basic type) defined in claim 5 and/or the first kind of the second type (second basic type) explained in claim 6 and/or the second kind of the first type explained in claim 7, and/or the second kind of the second type explained in claim 8 is characterized by another feature that it is possible to obtain a fixator set-up, called (6-3) type, in which there are six joints at six points on the upper (1) ring, and there are three joints at three points on the lower (2) ring.

13. The parallel robotic arrangement set up in consistency with claims 1,2,3,5 and 7 is characterized by one other feature that there are totally nine three- degree-of- freedom spherical joints, six screw-nut pairs and three one- degree-of-freedom simple revo lute joints in the fixator structure.

14. The parallel robotic arrangement set up in consistency with claims 1,2,3,6 and 8 is characterized by one other feature that there are totally six three- degree-of-freedom spherical joints, six two-degree-of-freedom universal joints and six screw-nut pairs in the fixator structure.

15. The modular parallel arrangement which can be set up in accordance with claims 1 and 3 using four different λ-modules defined in claims 5,6,7 and 8 is further characterized by the feature that amenable to all other claims it is possible to obtain thirty-two thousand seven-hundred and sixty eight (32 768) different external fixator set-ups.

16. The general structure of all types of λ-modules mentioned in the previous claims, specifically defined in claim 2, is further characterized by the feature that the fixed- length (10) and moving variable-length (11) cylindrical parts reflecting the structure of long and short legs are connected to each other by means of a nut (3).

17. The nut (3) existing in the structure of the λ-module mentioned in claim 16 is characterized by the feature that together with the cylindrical part (11) on which fitting threads are cut, it forms a screw-nut pair in its narrowest section, to be utilized in changing the length of the leg; it has a knurled surface on its cylindrical section with largest diameter, convenient for rotating manually, and properly cut planes on its upper outside section to fit to a standard wrench; a cylindrical hole simultaneously perpendicular to the nut (3) axis and cut planes, and cylindrical space on its inner lower section in which a groove is carved to be a seat for a ring to connect nut (3) to the hollow cylindrical part (10).

18. The hollow cylindrical part (10) mentioned in claims 2,16 and 17 is characterized by the feature that it has a set-screw hole in its lower section placed for the purpose of easily attaching a two-degree-of-freedom or a three-degree-of-freedom joint; two spherical grooves on its upper sides in mutually opposite directions into which a ball with suitable dimensions can be seated, and a ring seat so cut as to allow the nut (3) to be attached conveniently; a slot parallel to the cylinder (10) axis, graded according to a linear scale, used for measuring the length of the λ -module leg, and that the section on the upper end is conically tapered such that nut (3) and the ring can be easily mounted.

19. The assembly of the hollow cylindrical part (10) explained in claim 18 with the nut (3) the features of which are given in claims 16,17 is characterized by the feature that the nut (3) is fitted into its seat by means of the ring in such a way that it can rotate without being allowed to translate axially; the ball is pressed against the spherical groove on the surface of the cylindrical part (10) by a helical spring inserted in the cylindrical hole with a cap at the end, which belongs to the nut (3).

20. The assembly of cylindrical part (10) to which the nut is mounted is further characterized by the feature that the ball under the effect of the spring fulfils the task of acting as a locking mechanism thus fixing leg length by being seated on the surface of spherical groove at each time whenever the nut (3) turns half a revolution.

21. The assembly form of the long leg of the λ -module connecting the upper (1) and lower (2) rings is characterized by the feature that the three- degree-of-freedom universal joints (7) at the two ends are attached by means of a set-screw to the screw (11) on the upper side, again by means of a set-screw to the hollow cylindrical part (10) with length scale in the lower side; the nut (3) is attached by a ring, and that the intermediate connection piece, either (4) or (12), is attached by means of a bolt and nut.

22. The intermediate connection piece (4) necessary for the construction of the λ -module defined in claim 5 in the accordance with claims 2 and 21 is characterized by the feature that it carries on itself a hole through which the pin of the revolute joint is to pass; it holds the axis lines of the long and short legs in the same single plane perpendicular to the revolute joint hole axis; it fixes the location of the revolute joint at a point on the fixed- length segment (10) of the long leg axis by the use of a bolt and nut.

23. The intermediate connection piece (12) mentioned in claim 21 is characterized by the feature that it constitutes by the protruding cylinder the fixed connection axis of the two-degree-of-freedom universal joint as well as the rotation axis of the simple one-degree-of-freedom revolute joint of the second kind of the first basic λ -module explained in claim 7 by being connected to the cylinder (10) axis, by means of a bolt and nut, to which the protruding cylinder axis is perpendicular.

24. The first basic λ -module defined in claim 5 is further characterized by the feature that it is constructed by connecting the long leg, the length of which is adjusted on the part of nut (3), the assembly form of which is explained in claim 21, with the short leg, which has similar structural features like long leg, by using the intermediate connection piece (4) defined in claim 22 which is attached to the end of short leg by means of set-screw hole (6) and a suitable set-screw on the intermediate piece (5) in such a way that there is no relative rotation.

25. The second kind of the first basic type of λ -module defined in claim 7 is further characterized by the feature that it is constructed by connecting the long leg, the length of which is adjusted on the part of nut (3), the assembly form of which is explained in claim 21, with the short leg, which has similar structural features like long leg, by using the intermediate connection piece (12) defined in claim 23 which is attached to the end of short leg by means of set-screw hole (6) and suitable set-screws on the intermediate piece (5) in such a way that there is no relative rotation.

26. The second types of λ -module defined in claims 6 and 8 are further characterized by the feature that the intermediate connection piece (12) is evaluated in connecting long and short legs to each other, in two different configurations separated by 90-degree angle.

27. The two-degree-of-freedom universal joint used in the second types of λ - module defined in claims 6 and 8 is characterized by the feature that it is tightly attached to the ring by means of a connecting screw such that there is no relative rotation at the connection point.

28. The three-degree-of-freedom universal joint used in all types of λ - modules, defined in claims 5-8 is characterized by the feature that the connecting screw that joins the universal joint to the ring is provided with the ability to rotate with respect to the ring by leaving some clearance between surfaces of contact of the bolt head and the ring through the adjustment of thread length.

29. All types of λ -modules defined in claims 5-8 are characterized by the common feature that each of them being modular according to the claim 2 in its own structure, the joints at the ends of short leg can be changed by evaluating the intermediate connection pieces (4),(5),(6),(12) the functions of which are explained in claims 22,23,23,25 and 26 by means of suitable set-screws and thus it becomes possible to pass from one module type to another.