In this Specification, the term"lower back"is used in the conventional sense to describe the lumbar spinal and pelvic regions of the user. The lumbar spine is made up of the last five vertebrae of the spine which are numbered Ll to L5 running down the spine. The lowest vertebra of the spine is connected to the sacrum and the sacrum is in turn connected to the ileum. The joints commonly the cause of lower back pain are those between the individual vertebrae of the lumbar spine (the"lumbar joints"), those between the lowest vertebra and the sacrum (the"sacro- lumbar joints") and those between the sacrum and the ileum (the"sacro-iliac joints").

In this Specification the terms"upper","lower", etc., when applied to a user refer to the user in a normal standing position. The terms"upper"and"lower"when applied to the back manipulator or components thereof refer to the back manipulator when placed on the ground in its normal operating position.

According to the U. K. Department of Health, there are 27 million people in the U. K. who are affected by back pain during the course of a year. It is reported to be the country's biggest of absence from work, with 119 million days lost annually, costing industry £5. 5 billion per year.

The fundamental cause of lower back pain is compression of the lumbar joints, the lumbar-sacral joints and the sacro-iliac joints.

A wide range of devices have been designed with the aim of reducing or alleviating back pain. For example there are many different forms of lumbar support available for seating, as well as special pillows and vibrating back massagers. There have also been many different designs of corset or belt for being worn to provide back support, but these are intended to be worn to provide support for the back for extended periods during normal daily activity and tackle the symptoms rather than attempting to alleviate the root cause of the problem.

For example GB 1,288,960 discloses a belt device which incorporates a plurality of spaced support members on the inside of the belt and designed to contact the muscles laterally adjacent the spine. The support members are mounted on a flexible spring strip to be relatively mobile about several axes both due to the flexibility of the strip and by virtue of pivotal connections between the support members and the spring strip.

DE 1,566,401 discloses a device which comprises a band which is clamped around the body, and which consists of a flat flexible strip to which are pivotally connected support members which bear on the back muscles to either side of the vertebral column. Again the support members are capable of compound movement about several axes.

In the main, these only provide temporary relief for the symptoms of back pain rather than tackling the root cause. After extended research and practice in this area, we have designed a back manipulator which manipulates or articulates the lower back region of the user to relieve the compression of the lumbar, lumbar-sacral and sacro- iliac joints by traction, movement and pressure. This design of back manipulator in use supports the lower back region of a user when in a supine or part-supine position and by suitable movement and rest by the user provides manipulation, decompression and traction.

Accordingly, in one aspect of this invention, there is provided a back manipulator for placing in use beneath in the lower back region of a user in a supine or part-supine position, said manipulator comprising a plurality of spaced support segments each having a back-engaging region which in use contacts a part of the lower back of the user, said support members being constrained for relative rotational movement about a substantially common rotational axis.

In this way, the support members engage the lower back of the user at spaced longitudinal locations and are constrained to rotate about a substantially common rotational axis.

Preferably, the support segments are arranged in two groups, with the first group thereof being designed to support the lumbar region of the user and a second group of the support segments being designed to-support the pelvic

region of the user. In this way, the back-engaging regions can be applied appropriately to the muscular/skeletal structure.

Preferably, each support segment of the lumbar support group includes two spaced back-engaging regions for contacting the back of the user to either side of the spine. The two spaced back-engaging regions of each support segment may therefore engage the back muscles.

Preferably, the upper surface portions of the support segments in the pelvic support group are profiled to provide a relieved or sunken region for receiving the sacral region of the user and ideally each providing extended contact along a region of the user's back.

Each of the support segments is preferably of plate- like form having spaced generally planar surfaces generally orthogonal to the rotational axis and with one or more sides thereof forming said back-engaging region. The support segments may conveniently made from wood although many other materials would be suitable.

Although it may be possible to support the device with the support segments off the ground, each of the support segments preferably includes a ground-engaging side region for engaging the ground. Each of the ground-engaging side regions preferably has a generally circular profile so that the device may be rocked back and forth on the ground in use. The location of the centre of curvature of the profile is preferably adjacent or coincident with the axis

through the spinous processes of the user, The circular profiles of each of said ground-engaging side regions preferably have the same radii of curvature.

Preferably, at least some of the ground-engaging side regions are provided with a friction-enhancing surface.

This may conveniently take the form of a plurality of grooves.

The support segments are preferably configured such that the rotational axis lies generally horizontally when the manipulator is in use in an equilibrium position.

Preferably the spaced support segments are mounted for rotation on a common shaft. The support segments are preferably spaced on said shaft by respective spacer elements. The manipulator preferably includes some form of locking device for locking the support segments against relative rotation, for ease of storage or transportation.

The locking device may comprise a threaded cap threadably engaging one or each end of the shaft and which may be turned to clamp the support segments against relative rotation.

The spacing of the segments and their thickness in the direction of the rotational axis may be selected to suit a particular user but we have found that, anatomically the variation of the extent and configuration of the back in different users is very low and so a single device will suit most, if not all, adult users.

In practice, the manipulator is designed such that the

support segments contact a region of the user which extends between the lower thoracic/lumbar juncture to adjacent the lower portion of the sacrum.

In another aspect, this invention provides a method of manipulating the lower back of person to relieve or alleviate compression or spasm in one or more of the lumbar, sacro-lumbar and sacro-iliac joints, which comprises supporting the lower back region of the person when in a supine or part-supine position on a back manipulator device, raising the knees of the person with their feet on or near the floor, and rocking the user's legs alternately to either side of their longitudinal axis in a latero-medial plane, thereby to provide a rotational traction in one or more of the lumbar, sacro-lumbar, and sacro-iliac joints.

Preferably said leg movement is preceded by or followed by a period of rest on the back manipulator.

Preferably the back manipulation device comprises a plurality of spaced support segments each having a back- engaging region contacting the lower back region of the user and being relatively rotatable about a substantially common rotational axis.

Whilst the invention has been described above, it extends to any inventive combination of the features set out above or in the following description.

The invention may be performed in various ways, and an embodiment thereof will now be described in detail, by way

of example only, reference being made to the accompanying drawings, in which:- -Figure 1 is a general perspective view of an embodiment of back manipulator device in accordance with this invention; Figure 2 is a end view on the embodiment of Figure 1, taken on the"pelvic"end; Figure 3 is an end view of the embodiment of Figure 1, taken on the"lumbar"end; Figure 4 is a side view of the embodiment of Figure 1 ; Figure 5 is a top plan view of the embodiment of Figure 1 ; Figure 6 is an underneath plan view of the embodiment of Figure 1; Figures 7 (a) to 7 (c) are respective plan views of the first, second and third/fourth lumbar support segments of the embodiment of Figure 1; Figures 8 (a) to 8 (d) are respective plan views on the first, second, third and fourth pelvic support segments respectively; Figure 9 is a side respective plan view of the common support shaft of the embodiment of Figure 1; Figure 10 is a view of the lumbar spine region of a human showing the lumbar vertebrae, the sacrum and the coccyx, and Figure 11 is a diagrammatic transverse view showing the device in use.

Referring initially to Figures 1 to 9, the back manipulation device 10 comprises a plurality of support segments 12 to 26 mounted for rotation on a common shaft 28 (see particularly Figure 9). The support segments are spaced apart by respective spacer rings 30 in this embodiment made of a hard plastics material. The opposite ends of the shaft 28 are threaded and carry respective threaded caps 32. The caps may be tightened or relaxed to clamp the support segments or allow them to rotate relative to each other and to the shaft. In normal use, the support segments will be able to rotate, the manipulator being clamped solely for transportation and storage.

The support segments comprise two different groups, namely a lumbar support group 34 made up of lumbar support elements 12 to 18., and a pelvic support group 36 made up of pelvic support segments 20 to 26. In this embodiment the third and fourth lumbar support segments 16 and 18 are identical with the first and second having a generally similar shape but a slightly different profile as can be seen in the end view of Figure 3. Thus the lumbar support segments 12 to 18 each comprise a ground-engaging portion 38 of circular profile with the same radius of curvature.

Each of the lumbar support segment ground-engaging portions 38 is provided with an anti-slip surface here in the form of notches or grooves 40 cut in the ground-engaging surface. The lumbar support segments each have two curved back-engaging regions 42, designed to contact the muscles

in the users back to either side of their spine. Again, as seen in Figure 3 the height of the back-engaging portions increases from the first lumbar support segment 12 to the third support segment 16. This is designed to suit the expected profile of the spine when a user is supported in the device.

The pelvic support segments 20 to 26 each have a ground-engaging portion 44 of circular profile with the same radius of curvature as that of the lumbar support segments so that the ground-engaging surfaces 38,44 of the support segments together define a generally cylindrical surface which allows the manipulator to be rocked back and forth without twisting the rotational axis defined by the shaft 28. The ground-engaging portions also include notches or grooves 46 to provide an anti-slip effect.

Referring particularly to Figure 3, the pelvic support segments have curved upper back-engaging regions 48 which define a concavely dished region for supporting a transverse section of the sacral region of the user in use.

It will be noted from a comparison of Figures 8 (a) to 8 (d) that the height of the lowermost portion of the back- engaging surface 48 of the segments progressively increases from the first pelvic support 20 to the fourth pelvic support 26.

In use, a person lies on the floor in a supine or semi-supine position and slides the manipulator under their pelvis and the backbone, which tilts the back upwards. As

the weight-bearing lower lumbar spinal joints, the pressure on inflamed muscles, strained tendons, bulging discs and compressed nerves is relieved. The person then rocks gently from side to side to massage the muscles in the lower back area and also to manipulate the joints. After this movement the patient may rest to provide relaxation and decompression of the lower lumbar spinal joints, the lumbar-sacral joint and the sacro-iliac joints. The device has been clinically tested and has been found to help alleviate a range of problems including arthritis, sports injuries and rheumatism.