GB2095999A

GB2095999A - Fracture reduction apparatus

Info

Publication number: GB2095999A
Application number: GB8110131A
Authority: GB
Original assignee: DAJUE WANG UNIVERSITY COLLEGE
Current assignee: DAJUE WANG UNIVERSITY COLLEGE
Priority date: 1981-04-01
Filing date: 1981-04-01
Publication date: 1982-10-13
Also published as: GB2095999B

Abstract

A fracture reduction apparatus is provided for use in external fixation. The apparatus comprises a base and a first unit which comprises a platform, selectively movable with respect to the base either along a first translational axis or pivotally about a first pivotal axis. The first unit comprises a pair of blocks (1,2) which are movable in unison with one another or at different speeds. The blocks (1,2) carry a strut (7) which in turn carries the platform. A second unit, similar to the first, is mounted on the platform of the first unit, and a third unit, similar to the first and second units, is mounted on the platform of the second unit. The units operate at right angles to one another. The third unit is provided with means for holding the ends of bone fixation pins. <IMAGE>

Description

SPECIFICATION Fracture reduction apparatus This invention relates to the field of orthopaedics, and in particular to an apparatus for use in external fixation.

A variety of techniques are known for holding together the parts of a fractured bone while healing is taking place, One such technique, which is most usually employed for fractures of the tibia, is external fixation. This involves passing a plurality of pins usually two or three, through each of the parts of the bone so that the pins emerge through the skin of the patient. The pins may either emerge from the skin on only one side of the bone (single-sided fixation) or they may emerge on both sides (double-sided fixation). In what follows, only single-sided fixation will be referred to, but it is to be understood that what is described applied with appropriate modifications also to double-sided fixation.In most known frames the emerging ends of the pins are connected to a frame by adjustable clamps, and after the bone has been manipulated to reduce the fracture the clamps are tightened to hold the parts of the bone fixed with respect to one another and in the correct position. There are two main difficulties associated with this procedure. Firstly, accurate reduction of a fracture in three dimensions is very difficult and time consuming. Secondly, a frame which allows all the movements necessary for accurate reduction is of necessity complicated since a large number of lockable joints are necessary. Once reduction and fixation have been achieved a complicated and cumbersome apparatus remains attached to the patient.Systems have been designed which attempt to simplify the frame, but in these the relative movement of the pins is restricted and hence the accuracy of reduction possible is reduced.

The present invention derives from the notion that the functions of fracture reduction and fixation can be separated from one another, so that a sophisticated apparatus can be used on a patientforfracture reduction and then replaced, after reduction has been carried out by a simple fixation device, the reduction apparatus thus being freed for use on another patient.

According to the invention there is provided a fracture reduction apparatus comprising means for holding the ends of bone fixation pins, and means for rotating the said holding means about three orthogonal axes passing throught a point which is, in use, located at the site of the fracture and for moving the said holding means parallel to the said axes.

According to the invention there is further provided a fracture reduction apparatus for use in external fixation, comprising a base, a first unit selectively movable with respect to the base either along a first translational axis or pivotally about a first pivotal axis, a second unit mounted on the first unit and selectively movable with respect to the first unit either along a second translational axis or pivotally about a second pivotal axis, and a third unit mounted on the second unit and selectively movable with respect to the second unit either along a third translational axis or pivotally about a third pivotal axis, the third unit being provided with means for holding the ends of bone fixation pins, the translational axes being mutally perpendicular and the pivotal axes substantially intersecting one another at a point which, in use of the apparatus, is located at the site of the fracture.

An embodiment of the invention is shown in the accompanying diagrammatic drawings, in which: Figure 1 is an elevation showing part of one of the units of an embodiment of an apparatus according to the invention; Figure 2 is a plan view of part of what is shown in Figure 3; Figure 3 is an end view taken in the direction of arrow A in Figure 1; and Figure 4 is a perspective view of a fixation for use in conjunction with the fracture reduction apparatus.

As shown in Figures 1 and 2 a unit of the apparatus comprises two blocks 1 and 2. Each block slides on a respective rod 3 and 4 which is fixed at its ends in a stationary part of the apparatus which is ultimately secured to an appropriate base (not shown). Each block is internally threaded and a respective threaded rod is received in the internal threading of the blocks. The rod for block 1 is indicated by reference numeral 5 in Figure 1. The rod for block 2 is not visible in Figure 1, but the end of it can be seen in Figure 3 where it is denoted by reference numeral 6.

A transverse strut 7 is pivotally connected to the top of the blocks 1 and 2 by pivots 8 and 9. Pivot 9 is substantially larger than pivot 8 as it has to carry a greater load. The pivot 8 comprises a pivot pin fixed to the block 1 and received in a slot which is slightly elongate to allow for the variation in distance between the pivots 8 and 9 as the angular position of the strut varies (see below). An elongate member 10, for example a box section, extends perpendicularly to the strut 7 and in the same general direction as the rods3and4.

The threaded rods 5 and 6 are rotatable by means of a gear mechanism shown in Figure 3. This comprises parallel shafts ila and 11b and 12 of which the shafts 1 la and 1 1b carry bevel gear wheels 13 and 14which mesh with bevel gear wheels 15 and 16 on the ends of the rods 5 and 6.

The shafts 1 la and 1 1b further carry toothed wheels 17,18,19 and 20, and the shaft 12 carries toothed wheels 21,22 and 23. The wheels 19 and 20 are the same diameter as one another; the gear ratio between the wheels 22 and 18 is the same as that between the wheel 23 and the wheels 19 and 20.

The shaft 12 is shiftable in the direction of arrow 24 to a right hand position in which the wheels 18 and 22 mesh with one another and the wheels 20 and 23 mesh with one another. If the handle 25 is now rotated to cause the shaft 12 to rotate the shafts 1 la and 11b rotate at equal speed to one another so that rods 5 and 6 also rotate at the same speed as one another. The blocks 1 and 2 are thereby caused to travel along the rods 5 and 6 at equal speeds, causing the strut 7 to be carried parallel to the axes of the rods with no accompanying pivotal movement. If, on the other hand,lhe shaft 12 is in the left hand position illustrated, the shaft 11 a rotates faster than the shaft 11 b so that the block 1 moves faster than the block 2.This causes the member 10 to pivot about an axis perpendicular to the plane thereof as it moves along the rods 5 and 6. Although this might appearto be a composite movement compound of a rotational component and a translational component it can in fact be regarded a pure rotation or pivoting about an axis remote from the shaft. In practice this axis of pivoting should be located of the order of 20 cm away from the strut The fracture reduction apparatus according to the invention comprises three units. What is illustrated is part of the first one of those units. The elongate member 10 carries a platform at the end thereof remote from the pivot 7, and that platform carries the second unit The second unit is similar to the first unit except that its orientation is different.The rods thereof corresponding to the rods 3,4,5 and 6 extend parallel to the axes of the pivots 8 and 9. As considered from a reference point on the platform, the second unit permits longitudinal movement of a strut corresponding to strut 7 parallel to the axes of the rods of the second unit and pivotal movement of the strut of the second unit about an axis remote from that strut and perpendicular to the plane of the paper in Figure 1. The second unit has an elongate member corresponding to the member 10 of the first unit and that elongate member carries a platform.

The platform of the second unit carries the third unit in the same way as the platform of the first unit carries the second unit. The axes about which the strut 7 of the first unit pivots and the axes about which the corresponding struts of the second and third units pivot intersect at what is substantially a point. The third unit differs from the first and second units in that it is provided with at least one clamp for clamping the ends of fixation pins.

In use of the above described fracture reduction apparatus, fixation pins are inserted into the bone on either side of the fracture. The pins on the proximal side of the fracture are held stationary by a clamp attached to a stationary portion of the apparatus.

The pins on the distal side of the fracture are held in the clamp which is carried by the third unit of the fracture reduction apparatus. The distal portion of the bone is then manipulated by means of the handle 25 and the corresponding handles of the second and third units, with appropriate selection in each case of the position which causes translational movement and the position which causes pivotal movement. It should be added that pivoting up to about 15 either side of a central position is provided in each unit. Manipulation proceeds until the distal portion of the bone is correctly positioned. As the facture site is relatively unobscured by the fracture reduction apparatus it can be continuously viewed using a low intensity X-ray apparatus with an image intensifier. Since the operator of the fracture reduction apparatus does not need to place his hands close to the fracture site this procedure does not subject the operatorto more than a minimal X-ray dosage.

Once the fracture has been reduced the pins are held in the reduced position by a fixation which can be of any suitable form. For example the fixation may be of the form shown in Figure 4. This comprises two halves 26 and 27 which, when screwed together by screws 28 and 29, define four compartments 31,32,33 and 34. In use, the compartment portions in each half are filled with bone cement and the halves 26 and 27 are then located together with a respective fixation pin passing through each compartment. Once the cement has set the fracture reduction apparatus is disconnected from the pins and can then be used for another patient.

Claims

1. Afracture reduction apparatus for use in external fixation comprising means for holding the ends of bone fixation pins, and means for rotating the said holding means about three orthogonal axes passing through a point which is, in use, located at the side of the fracture and for moving the said holding means parallel to the said axes.

2. A fracture reduction apparatus for use in external fixation, comprising a base, a first unit comprising first means selectively movable with respect to the base either along a first translational axis or pivotally about a first pivotal axis, a second unit mounted on the said first means and comprising second means selectively movable with respect to the said first means either along a second translational axis or pivotally about a second pivotal axis, and a third unit mounted on the said second means and comprising third means selectively movable with respect to the said second means either along a third translational axis or pivotally about a third pivotal axis, the said third means being provided with means for holding the ends of bone fixation pins, the translational axes being mutally perpendicular and the pivotal axes substantially intersecting one another at a point which, in use of the apparatus, is located at the site of the fracture.

3. An apparatus according to claim 2, wherein each unit comprises a pair of blocks each of which is mounted for translational movement, and a strut pivotally connected to both of the blocks, the said first, second or third means being secured to the strut, the blocks of each unit being selectively movable in unison with one another to produce translational movement of the strut connected thereto and hence of the said first, second or third means secured to the strut, or at different speeds to one anotherto produce pivotal movement of the strut and hence of the said first, second or third means.

4. An apparatus according to claim 3, wherein the blocks are each threadedly mounted on a threaded rod, the rods of each unit being connected to a gear box provided with means for rotating the rods at the same speed as one another or at different speeds.

5. Afracture reduction apparatus substantially as herein described with reference to Figures 1 to 3 of the accompanying drawings.

6. A fracture reduction and fixation arrangement which comprises a fracture reduction apparatus according to any preceding claim in combination with a fracture fixation apparatus which comprises a pair of elongate members each of which has a plurality of recesses having partially cut away sidewalls, the recesses of the members cooperating to define a plurality of compartments each of which, in use contains a cement, the ends of the fixation pins passing, in use into the compartments through the cut away sidewalls and being held by the cement.