ORTHOPAEDIC APPARATUS

Abstract: External fixation apparatus includes two carriages for attaching to bone at opposite sides of a fracture. The car­ riages are formed with internal keyed bores for receiving a straight rigid rod formed longitudinally with a keyway for the carriage keys and with a screwthread for nuts screwed onto the rod to fix the carriages. In a case of bone misalignment, this rod is replaced by an angularly adjustable elongate de­ vice comprised of rods 1 and 2 with keyways 21 and 22 and screwthreads 23 and 24, hinge elements 3 and 4 releasably clamped by clamps 5 and 6 to the rods 1 and 2, a nut-and-­ bolt device 8 serving as a removable hinge pin and also to clamp releasably together the elements 3 and 4, two groups of holes 9 through the element 3 with the holes within each group equally pitched, holes through the element 4 sim­ ilarly arranged except at a pitch less than that of the holes 9, and a locating member insertable through a selected hole 9 into a selected hole in the element 4.

Description: ORTHOPAEDIC APPARATUS This invention relates to orthopaedic apparatus. Known apparatus for use in external fixation includes two carriages in the form of elongate metal blocks for attaching to bone at respective opposite sides of a fracture, for example of the tibia, by way of pins or screws surrounded by bone cement. Each carriage is formed with an internal keyed bore extending therealong, and through these two bores can be slid a straight rigid steel rod formed throughout its length with a screw-thread for co-operating with four nuts, one at each end of each carriage. The rod is also formed throughout its length with a keyway for receiving the keys of the two carriages. By screwing the nuts inwardly towards each other, the carriages can be displaced towards each other along the rod, so to put the fracture under compression. After the fixation operation, it may be found that the bone parts at respective opposite sides of the fracture are angularly misaligned, for example because one of the carriages is not correctly orientated on its bone part. In order to correct this misalignment, it is likely to be necessary to detach the one carriage from its bone part and to re-attach it with the correct orientation. According to one aspect of the present invention, there is provided apparatus for use in external fixation, comprising first and second members for attaching to bone at respective opposite sides of a fracture by means of fastening elements, and a straight rigid elongate means releasably mountable on the first and second members for maintaining the first and second members fixed relative to each other, characterized in that the apparatus includes another elongate means for replacing said rigid elongate means to maintain the first and second members fixed relative to each other and comprised of first and second rigid parts releasably mountable on the first and second members, respectively, and interconnecting means arranged so to interconnect the first and second parts as to enable adjustment of the relative angular position of those parts and fixing of the adjusted angular position. It is thereby possible for a surgeon to replace the rigid elongate means by the other elongate means and ensure correct bone alignment without the need to detach one of the first and second members from the bone. According to another aspect of the present invention, there is provided orthopaedic apparatus comprising first and second elements turnable relative to each other about an axis, characterized in that a first plurality of holes is formed through the first element and distributed around said axis at substantially a constant radius therefrom, a second plurality of holes is formed in the second element and distributed around said axis at substantially said constant radius but with a pitch different from that of the first plurality, and a locating member is insertable through a selected one of said first pluralilty into a selected one of said second plurality. This orthopaedic apparatus is usable in various applications where bone alignments should be relatively accurately obtained and reliably maintained thereafter. In order that the invention may be clearly understood and readily carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows a sectional side elevation of a device of an apparatus for use in external fixation, Figure 2 shows a top plan view of the device, and Figure 3 shows a fragmentary exploded view of two assemblies and a locating pin of the device, the left-hand assembly being shown in underneath plan, the right-hand assembly in top plan and the pin in side elevation. The apparatus for use in external fixation includes two carriages in the form of elongate metal blocks (not shown) for attaching to bone at respective opposite sides of a fracture, for example of the tibia, by way of pins or screws surrounded by cement. Each metal block is formed with an internal keyed bore extending therealong, and through these bores can be slid a straight rigid steel rod formed throughout its length with a screw-thread for co-operating with four nuts, one at each end of each block. The rod is also formed throughout its length with a keyway for receiving the keys of the blocks. By screwing the nuts inwardly towards each other, the blocks can be displaced towards each other along the rod, so to put the fracture under compression. After the fixation operation, it may be found that the bone parts at respective sides of the fracture are angularly misaligned, for example because one of the blocks is not correctly orientated on its bone part. In order to enable this to be corrected, the new device shown in Figures 1 to 3 is provided. It is designed to replace the straight rod, without it being necessary for either of the blocks to be detached from the bone. It comprises two screw-threaded rods 1 and 2, which are formed with respective longitudinal keyways 21 and 22 and are identical to each other, except that their screwtheads 23 and 24 are of opposite hand. The device also includes two part-circular aluminium or steel elements 3 and 4 which incorporate respective U-clamps 5 and 6 which, by means of bolts 7, enable the elements 3 and 4 to be clamped to the respective inner ends of the rods 1 and 2. The elements 3 and 4 are connected together by a nut-and-bolt device 8 having its axis perpendicular to the rods 1 and 2. The elements 3 and 4 are formed with through bores 9 and 10 all parallel to the axis of the device 8. The bores 9 and 10 are arranged distributed about the axis of the device 8 at a constant radius from that axis. Moreover, the bores 9 or 10 of each element 3 or 4 are arranged in two sets separated by the U-clamp 5 or 6. The bores 9 in each set are equi-angularly spaced around the axis of the device 8, as are the bores 10 in each set, except that the angle of spacing of the bores 9 is greater than the angle of the spacing of the bores 10. The arrangement, particularly the angular spacing, is such that, for every few degrees of rotation of the elements 3 and 4 relative to each other around the axis of the device 8 0 throughout a range of about 20 to each side of the 1800 position of the rods 1 and 2, at least one of the bores 9 comes into exact alignment with at least one of the bores 10. With the desired bores 9 and 10 in exact alignment, a locating pin 11 can be inserted into those bores 9 and 10 to lock the elements 3 and 4 in the adjusted position. The pin is prevented from working out of the bores 9 and 10 by means of a plastics cap 12 held in position at one end of the bolt of the device 8 by a screw 13 extending axially through the bolt of the device 8. At the other end of that bolt, a nut 14 screwed onto the screw 13 holds another cap 15 in position. In Figure 2, the plastics cap 12 is shown in outline only. Following removal of the straight rod from the elongate blocks, the rods 1 and 2 are inserted through the blocks, four nuts being screwed onto the rods 1 and 2, one at each end of each block so as to leave the blocks loose between them. The rods 1 and 2 are inserted into the elements 3 and 4, with the items 3, 4 and 8 being in the assembled condition shown in Figures 1 and 2, the device 8 being loose enough to allow the elements 3 and 4 to turn relative to each other. With the clamps 5 and 6 untightened, these assembled items are turned as a unit about the axes of the rods 1 and 2, to bring the plane of angular adjustment of the elements 3 and 4 into a position parallel to the plane of correction needed between the two bone parts. Thereupon, with the rods 1 and 2 inserted deeply into the elements 3 and 4, the clamps 5 and 6 are tightened upon the rods 1 and 2, and the rods 1 and 2 are turned about the device 8 relative to each other to align the bone parts, the pin 11 being inserted into those two bores 9 and 10 giving the best degree of alignment of the bone parts. Thereupon, the device 8 is tightened, the four nuts are tightened against the two blocks, and the caps 12 and 14 are placed in position and retained by the screw 13 and the nut 14. Among the advantages of the apparatus hereinbefore described are that it and thus the fracture can be adjusted as regards angular position without removal of the elongate blocks; a relatively high degree of correction of the angular position can be reliably obtained, and, following adjustment, the apparatus is robust and remains in the adjusted condition.

Claims: CLAIMS 1. Apparatus for use in external fixation, comprising first and second members for attaching to bone at respective opposite sides of a fracture by means of fastening elements, and a straight rigid elongate means releasably mountable on the first and second members for maintaining the first and second members fixed relative to each other, characterized in that the apparatus includes another elongate means (1-11) for replacing said rigid elongate means to maintain the first and second members fixed relative to each other and comprised of first and second rigid parts (1-7) releasably mountable on the first and second members, respectively, and interconnecting means (8-11) arranged so to interconnect the first and second parts (1-7) as to enable adjustment of the relative angular position of those parts (1-7) and fixing of the adjusted angular position. 2. Apparatus according to claim 1, wherein said interconnecting means (8-11) comprises a first plurality of holes (9) formed through the first part (1,3,5,7) and distributed around an axis of relative turning of the first and second parts (1-7) at substantially a constant radius from said axis, a second plurality of holes (10) formed in the second part (2,4,6,7) and distributed around said axis at substantially said constant radius but with a pitch different from that of the first plurality (9), and a locating member (11) insertable through a selected one of said first plurality (9) into a selected one of said second plurality (10). 3. Apparatus according to claim 2, wherein said interconnecting means includes readily removable hinge pin means (8) defining said axis. 4. Apparatus according to claim 3, wherein said hinge pin means (8) serves also to clamp releasably the first rigid part (1,3,5,7) to the second rigid part (2,4,6,7). 5. Apparatus according to claim 2, 3, or 4, and further comprising protective cap means (12,15) arranged to cover the first and second pluralities of holes (9,10) and the locating member (11) and to retain said locating member (11) in the selected holes (9,10) and fastening means (13,14) arranged releasably to fasten said protective cap means (12,15) to said other elongate means (l 6. Apparatus according to any preceding claim, wherein each of the first and second rigid parts (1-7) comprises a turnable hinge member (3,4), an elongate member (12), and clamping means (5,6,7) arranged releasably to clamp said hinge member (3,4) to one end of said elongate member (1,2). 7. Orthopaedic apparatus comprising first and second elements (3,4) turnable relative to each other about an axis, characterized in that a first plurality of holes (9) is formed through the first element (3) and distributed around said axis at substantially a constant radius therefrom, a second plurality of holes (10) is formed in the second element (4) and distributed around said axis at substantially said constant radius but with a pitch different from that of the first plurality (9), and a locating member (11) is insertable through a selected one of said first plurality (9) into a selected one of said second plurality (10). 8. Apparatus according to claim 7, and further comprising protective cap means (12,15) arranged to cover the first and second plurality of holes (9,10) and the locating member (11) and to retain said locating member (11) in the selected holes (9,10), and fastening means (13,14) arranged releasably to fasten said protective cap means (12,15) to at least one of said first and second elements (3,4). 9. Apparatus according to claim 7 or 8, and further comprising readily removable hinge pin means (8) arranged pivotally to interconnect said first and second elements (3,4) and defining said axis. 10. Apparatus according to claim 7 or 8, and further comprising releasable clamping means (8) arranged to clamp releasably said first element (3) to said second element (4).

Inventors: DENHAM, ROBIN ARTHUR
Applicants: OEC EUROPE LIMITED
Application year: 1983
Main classification: A61B17
IPC codes: F16C11, A61B17