GB2300919A - Leg length inequality meter - Google Patents

Abstract

The device comprises a parallel sided measuring board 1, on which the patient sits, at one end. The board bears a central ridge 20, to centralise the pelvis and has a back support 11, which may bear two fixed pads 14 to centralise the spine. The back support also bears a pair of vertically adjustable pads 16, which in use are positioned behind the patients dorsal iliac crests, whereby these crests may be accurately aligned at right angles to the axis of the board. The board also bears a longitudinally movable central spacing element 4 to ensure leg alignment and a pair of identical tape measures 19. These are parallel, approximately 20 cm apart and run in recesses along the axis of the board. The tapes are for measuring the positions of the left and right heel and by construction they give identical readings if a line is drawn at right angles across the board.

Description

LEG LENGTH INEQUALTTY METER This invention relates to a measuring device to detect unequal leg length.

Leg length inequality is a common condition which may result from leg fracture, an operation to the anterior cruciate ligament, Perthe's disease or other bone disease, hip replacement, poliomyelitis, a prolonged childhood illness or unknown causes. If not corrected, it is one of several well-documented factors leading to chronic back pain.

Furthermore when lifting, an inequality may predispose the spine to a prolapsed disc, or when running, to a back or leg injury such as a muscle strain or a stress fracture.

Leg length inequality results in a tendency for the hips to be tilted laterally for most of the time while standing. Consequently the spine arises at an angle to the vertical and proceeds through one or several lateral bends, typically forming an S before reaching the top of the neck. This chronic flexion of the spine in a lateral plane is sometimes termed scoliosis, although this condition may have several other causes.

An accurate device to rapidly detect and measure leg length inequality would thus be of use to doctors, surgeons, physiotherapists, chiropractors, or osteopaths.

Measurement of inequality by tape measure, or by standing the patient on a level surface and placing blocks of various thicknesses under the short leg heel has been proved to be unreliable and usually requires that the patient strip. Shoes with mechanical or electrical heel raising features may aid the above process but do not help in ensuring that the result is true horizontal hip alignment. A device which attaches to an examination couch and measures leg length while the patient is lying prone may not take account of a skewed hip alignment, i.e. not at right angles to the measurement axis. A vertical frame within which the patient stands, has a facility to raise or lower each heel and has sliding probes attached to the side bars, but may require that the patient strip so that body alignment can be checked and to allow probes to be positioned at the chosen hip reference points.On the other hand, use of X ray tomography, or the use of an ultra sound probe to detect the relative positions ofjoint cavities, requires sophisticated equipment and may further require accurate computer or operator measurement of images. Furthermore it is undesirable to subject a patient to X radiation if avoidable. Expensive or bulky equipment usually results in restricted, and formal access.

By contrast, the invention described here does not require that the patient strip and it provides an easy to use, portable, rapid, simple, direct, mechanical measurement device that is economically more suited to most practitioners means.

Accordingly this invention provides a device for measuring leg length inequality of a clothed, seated, patient with legs outstretched. It comprises the following parts a parallel sided measuring board (the board) 1, in figure 1, on which the patient sits, at one end. The board bears a central ridge 20, at this end, to centralise the pelvis and has a back support 11, which may bear two fixed pads 14 to centralise the spine. The back support also bears a pair of vertically adjustable pads 16, which in use are positioned behind the patients dorsal iliac crests, whereby these crests may be accurately aligned at right angles to the axis of the board. The board also bears a longitudinally movable central spacing element 15, to ensure leg alignment and a pair of identical tape measures 19. These are parallel, approximately 20 cm apart and run in recesses along the axis of the board.The tapes are for measuring the positions of the left and right heel and by construction they give identical readings if a line is drawn at right angles across the board.

In the preferred design, there is a spring 25, shown in fig 2, and pairs of electrical contacts 26 and 27 placed behind each of the two adjustable pads on the backrest. This is in order that an indication be given to the measurer, audibly, or via one, or a pair of light sources, when both the patient's iliac crests are firmly pressed into their correct alignment position. To help create the requisite pressure on these pads, an adjustable ramp 2 may be placed on the seat, whereby the weight of the patient's torso, sliding down this ramp, partly contributes to creating a backward thrust against the pads. A second source of pressure may also be provided by a force applied to the patients' heels. To facilitate this, a sliding carriage 6 is positioned against the heels.This loosely articulates with the sides of the board and in use is moved forward by a central rod 8 attached to a second carriage 9 that also articulates with the board and which bears a central handle 10 for the measurer to push with. By this arrangement, equal force may be applied to both heels and after locking the forward carriage in position, the forward edge of this carriage can be used as a cursor to determine leg length inequality, if any, in millimetres, by reference to the tape measures 19.

The following features are not illustrated in figs 1. To ensure that the patient's legs are pressed down and thus straight, arrangements similar to that shown in Fig 2 are attached to 4 either side of spacing element 5. In order to double check the hip alignment, a pair of sprung loaded, extending, tape-measures attached to a transverse bar, on the underside of the board, may be used to check the position of the points of the ventral iliac crests. So that only the patient's heels are in contact with carriage 6, a rectangular spacing bar of appropriate size may be attachable to its front surface.

Furthermore, in the event of the patient having a large leg length inequality, spacing elements of known thickness may be temporarily attached to the short leg side of the forward carriage, to make up most of the deficit.

A specific embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing in which: Figure 1 shows in perspective the leg length inequality measuring device, comprising a seat back support, seat back, with iliac crest pads, and measuring board, with paired tape measures set into it. On the board, at the seat end are a central ridge and a ramp.

In the middle is a leg alignment carriage. At the far end is a combination of a forward carriage for the patients' heels to bear against and in tandem with it, a rear carriage for the operator to use for applying even pressure to both heels: Figure 2 shows a large scale sectional drawing of one of the pair of hinged flaps. This carries a vertically moveable iliac crest pad on its outer surface and an electrical contact on its inner surface.

Referring to the drawings, to use the invention, the patient is seated, leaning slightly forwards, with legs outstretched and aligned along the measurement board 1, (hereinafter known as the board). For the sake of ease of use this may be incorporated as part of, or alternately rest on, two chairs or stools, one for the patient and the other for the measurer. At each end of the board, a narrow strip (not shown), which run across the underside, help to stabilise it on concave chair seats.

Three devices aid accurate leg alignment. Firstly a longitudinal central ridge 20 is provided on the seat and on the ramp 2. Secondly a carriage 4, which articulates with and slides along the board, is positioned at the back of the patients' knees. This carries a central, spacing element 5, which lies closely between the legs. To either side of this there may be a pressure sensitive pad, not shown. These only complete an electrical circuit, as indicated by a light emitting diode, when both legs are evenly straight.

Thirdly, another articulating, sliding, carriage 6, is positioned against the heels. This also carries a spacing element 7, protruding from the front of it, to help position the feet so that they are equally centralised.

Four features aid accurate alignment of the pelvis at right angles to the board's long axis. Firstly the hinged seat back 11, is accurately aligned in a plane at right angles to the board's axis. The seat back may be supported as shown, by a hinged support 12 together with two restraining straps 13 between them, or preferably by an alternative arrangement whereby the support is attached by hinges, on the opposite side to that shown, to the end of a short extension of the measurement board. A stop at the top rear side of the seat back 11 and a single releasable strap from this to the middle of the back of the support 12, together in section form a rigid triangle. Secondly the seat back may be provided with a pair of small, parallel, adjacent, sprung, pads 14, which help to support the spine and centralise it. In section these may comprise three layers, leather, wood and sponge rubber.Thirdly, the patient's torso weight bears down on a smooth, backward facing, ramp 2, which is adjustable by means of a series of fixings 3 and is thus designed to suit different sizes of pelvis. It is also accurately aligned at right angles to the board's long axis. The ramp's second fUnction is also to deflect part of the torso weight to the rear, in order to press the iliac crests evenly against the seat back. On this there are a pair of sprung hinged flaps 15, these carry a pair of narrow, horizontal, pads 16. Pads 16 can be moved vertically, to be positioned directly behind the patient's dorsal iliac crests in order to support them in a plane at right angles to the board's axis. niac crest alignment, as an indicator of hip alignment, is essential for accurate measurement of leg length inequality using this device.As a means of checking alignment, a pair of electrical contacts 26 and 27 are positioned behind each flap 15. When correct pressure and alignment have been achieved, both sets of electrical contacts complete a single or double circuit, thus giving a visual indicator for the measurer by use of a light emitting diode or diodes. Alternatively an audible signal may be produced. Fourthly, in the event of a difficulty in ensuring alignment of the dorsal iliac crests, a pair of sprung loaded extending steel tape measures may be used to check the alignment of the ventral iliac crests. The tape cases are fixed to and evenly positioned on the ends of a bar (not shown). This is attachable accurately at right angles to the axis of the board, where it is held in position by slotting it between two rectangular strips attached to the underside of the board. The ends of the tapes have small rings attached to them which the patient holds against the front edges of the two iliac crests. The measurer then checks that the two tapes give equal readings, before making a leg assessment.

Figure 2, shows in a sectional drawing, an example of how the pads 16 may be retained on flaps 15, and the arrangement of the hinge 23, screws 24 and other parts. Behind each flap 15, there is a compression spring 25, which is set into a shallow cavity in 11.

This spring is retained by a countersunk screw 20, which passes through a clearance hole in 15 and into 11. A contact 26, attached to the back of 15, only touches another contact 27, when 16 is exactly parallel to the seat back 11. Each of the pads 16 are retained on 15, by a pair of short rods 21, which protrude from the back of 16 and slide into holes 22, drilled into 15. A series of such paired holes in 15, allow for vertical adjustment of 16 to accommodate different depths of pelvis. In an alternative arrangement (not shown), the moveable pads 16 are dispensed with and two narrow flaps with fixed pads are attached to both ends of a moveable rectangular bar. This bar is capable of vertical movement on the seat back 11, by a similar means to that of ramp 2 which is capable of longitudinal adjustment on the board.This alternative device is provided with electrical contacts and thus functions in the same manner as the combination of iliac crest pads 16 and flaps 15.

Means are provided as follows for creating even pressure on both heels, This is in order to take up slack in soft tissues and for ensuring that the dorsal iliac crests are finnly pressed against the two pads 16. A sliding carriage 6, which is loosely articulated with the measurement board by two springy strips 17, is positioned against the heels. Behind 6 is another sliding carriage 9. This also articulates with the board. It carries a central, pointed, rod 8, which is rigidly attached to the centre of 9 and bears against a central hollow on 6, whereby forward pressure, applied using handle 10, is only transmitted centrally to carriage 6, which is thus free to take up an angle with the measuring board axis that is appropriate to any leg length inequality. For example, if legs are of even length, the angle will be a right angle.Once this angle has formed, vertically downward pressure is applied to carriage 6, to hold it in position while the patient's legs are withdrawn. A pencil line may then be traced along the front edge of 6 and across the central white plastic strip 18. Another, adjacent, pencil line drawn at right angles to the measuring board, can then be used to demonstrate the equality or inequalit of leg length. Alternately this may be calculated, by reference to readings on the tape measures.

In the - event of a large inequality it may be necessary to temporarily attach one or more spacing elements of known thickness to the front of the short leg side of the carriage 6. This or these may be held in place by pairs of short tapered rods on the spacing elements that slide into paired holes on each side of the carriage 6, or into holes in the spacing element below. Alternatively recessed magnets may be used for this purpose. The inequality will then be the sum of the spacing element/s, plus or minus the inequality as read from the tapes 19.

The locking device for carriage 6 may be constructed as follows. Four, shallow, well spaced, cavities are cut out of the underside of carriage 6 and are filled with firm sponge rubber. These are covered with a thin layer of smooth plastic to provide sliding clearance between the base of 6 and the surface of the measuring board. This clearance is sufficient to allow a high friction layer to be attached to the underside of 6 without impeding its free movement. That is, until downward pressure is applied, thereby compressing the sponge rubber and locking 6 in position. This ensures that carriage 6 is not accidently moved as the patients' legs are withdrawn.

The device as described above is easily disassembled, the moveable parts may then be packed in a file box and the board's back rest assembly folded for ease of transport.

Claims (11)

1. A leg length inequality meter, partly comprising a parallel sided measuring board (the board) on which a patient may sit at one end with legs outstretched along this board. The board has a central ridge at the seat end and a seat back which bears two fixed pads to support and centralise the lower spine. The seat back also bears two adjustable pads which are placed behind the patients dorsal iliac crests, whereby these crests may be accurately aligned at right angles to the axis of the board. The board also bears a centrally placed, moveable, knee, spacing element to aid leg alignment and a pair of identical tape measures which run longitudinally, each side of a central strip and give identical readings if a line is drawn across the board at right angles.

2. A leg length inequality meter as in claim 1, wherein a sliding carriage with a central spacing element is provided to aid leg alignment. The carriage may be provided with pressure pads and electrical contacts in order that the measurer can ascertain that downward pressure is being applied to both legs and thus that they are equally straight.

3. A leg length inequality meter as in claims 1 and 2, wherein means are provided to press the patients dorsal iliac crests against the pads on the back rest, by virtue of the action of a smooth, sloping, ramp, at the seat. This ramp is aligned at right angles to the board and its position is adjustable.

4. A leg length inequality meter as in claims 1-3, wherein means are provided to help evenly press the patients iliac crests against the adjustable pads on the back rest by virtue of a device to create even pressure against the patients heels.

5. A leg length inequality meter as in claims 14 wherein means are provided to lock immobile in position the device used to create even pressure against the patients heels.

6. A leg length inequality meter as in claims 1-5, wherein electrical means are provided to indicate to the measurer when even pressure is being applied by the patient's iliac crests to the adjustable pads.

7. A leg length inequality meter as in claims 1-6, wherein the measuring board, the back rest and its support are hinged, so that the device is foldable for ease of transport.

8. A leg length inequality meter as in claims 1-5, wherein the measuring board and seat back have means for permanent attachment to two custom made chairs, one for the patient and the other for the measurer.

9. A leg length inequality meter as in claims 1-8, wherein a pair of extending, spring loaded, measuring tapes are attached to the ends of a cross member affixed to the under side of the board. These have rings at the ends of the tapes which the patient holds adjacent to the ventral iliac crests for the purpose of checking correct hip alignment, at right angles to the boards axis.

10. A leg length inequality meter as in claims 1-9, wherein means are provided to compensate for a large leg length inequality by use of one or more spacing elements of known thickness which may be placed against the short leg heel.

11. A leg length inequality meter substantially as described herein with reference to figures 1 and 2 of the accompanying drawings.