GB1571392A - Reciprocal walker - Google Patents

Description

(54) RECIPROCAL WALKER (71) I, THE SECRETARY OF STATE FOR SOCIAL SERVICES, London, do hereby declare the invention, for which I pray that a patent may be granted to me and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to bi-pedial ambulation aids of the reciprocal walker type, i.e.

those permitting alternate strides, for paraplegic patients. Such patients being without muscle control in the lower limbs, require both support to hold the limbs in an extended position to support the body weight, and a mechanism by which they can swing the legs forward, when required, to achieve forward motion.

One conventional ambulation aid for paraplegic patients utilises long-leg calipers attached to a body brace by hinged hip joints. In one such ambulation aid the hinge joints are positively locked in an alternating sequence. In an alternative ambulation aid a system of lever or cable operated motion transfer is used. Neither of these ambulation aids is completely satisfactory, the former imposing a gait of individual disjointed strides and the latter imposing a particular spatial constraint on the limbs.

The invention provides a bi-pedial ambulation aid for a paraplegic patient, comprising a truncal brace, a leg caliper for each leg, a hinge joint for each leg caliper by which this leg caliper is attached to the truncal brace at a position adjacent the patients anatomical hip joint, and a biasing means for each hinge joint by which means hyperextension of the corresponding anatomical hip joint is resisted. In the context of this specification hyper-extension of the hip joint refers to extension of the thigh in a direction to the rear of the trunk or to leaning of the trunk in a direction to the rear of the thigh. The ambulation aid of the invention, used in conjunction with a rollator or crutches for support, permits a limited rearward tilt of the trunk against the action of the biasing means so enabling the patient to move a non-supporting leg forward by leaning backwards on the supporting leg and perhaps twisting the trunk, and also enables a rearwardly extended leg to swing forward under the action of the spring. A detailed description of the gait will be given later.

Preferably each biasing means comprises a tension spring, and a forward facing outrigger on the leg caliper close to the hinge joint, the tension spring acting between a position on the outrigger and a position on the body brace close to the hinge joint. Suitably, the biasing means is designed so that the tension spring is unstressed when the leg caliper is in axial alignment with the trunk (upright stance) and the tension spring is chosen so that it will support the weight of the leg during its forward movement whilst permitting a useful degree of rearward tilt of the trunk.

The outrigger is preferably pivotally attached to the leg caliper in such a way as to permit limited rotational movement of the former to enable the spring to resist hyper-extension of the hinge joint whilst not effecting forward extension thereof for seating.

Preferably the hinge joints each comprise a hinge pin attached to either the truncal brace or the leg caliper, and a ball or roller journal bearing, mounted on the hinge pin, the journal bearing being laterally offset from the normal vertical position by an angle of 10 degrees such that the lower edges of the bearings are convergently directed. The estimated degree of rock in the patients gait is 10 degrees so that by virtue of their lateral offset the bearings are maintained in a substantially upright position during the forward swing of the leg. By making the hinge joint revolve on a ball or roller bearing and by keeping this in a verti cal position during the forward swing of the leg, frictional forces in the hinge joint are minimised.

A means, independent of the biasing means, may be provided to limit the forward and rearward extension of the thigh by limiting rotation of the hinge joint. Preferably this rotation limiting means may be dis engaged to permit forward flexure of the thighs for seating.

The leg calipers are preferably attached at their lower ends to the shoes of the patient by means of spur elements of circular cross section which extend transversely of the shoe and which permit the shoe to hinge about the axis of the spur elements. This mechanism obviates the requirement for substantial contouring of the shoe sole which would otherwise be necessary if the calipers were rigidly attached to the shoe.

With the pivotal shoe attachment described the rear of the heel of the shoe may be chamfered to maintain ground clearance during the forward swing of the foot, and the outer edges of the shoe sole may be chamfered to minimise the effort required to perform a transverse rocking movement during ambulation but the sole of the shoe does not have to match the curvature of the shoes swing about the hip joint.

The invention will now be described, by way of example only, with reference to the drawings accompanying the provisional specification, in which: Figure 1 is a sketch of one lateral half of the ambulation aid of the invention showing its general arrangement; Figure 2 is a sketch in enlarged scale showing a lateral view of the hinge joint portion of the ambulation aid illustrated in Figure 1; Figure 3 is a sectional drawing of the hinge joint illustrated in Figure 2; and, Figure 4 is a schematic diagram illustrating use of the invention.

Referring firstly to the general arrangement drawings of Figure 1, it can be seen that the ambulation aid utilises long leg calipers for support of the legs, only one of these calipers being shown. Each caliper comprises an outside leg brace member 1 which runs the full length of the leg, and an inside leg brace member 2 which runs from the upper/mid section of the thigh to the foot. Brace members 1 and 2 are linked together at their upper ends by a thigh band 3, and by a knee support band 4 at a level just below the knee. Shoe mounting spurs 5 are provided at the lower ends of the brace members 1 and 2.

At the upper end of the outside leg brace member 1, is provided a hinge joint, generally indexed 6, by which each long leg caliper is joined to a truncal brace which comprises a thoracic strap 7, an abdominal strap 8, and body brace members 9 (only one being shown). To add lateral stability to the ambulation aid, the body brace members 9 are linked together at their lower ends at a position adjacent the hinge joint 6 by a pelvic cross-tie 10.

The construction of the hinge joints 6 can be clearly seen by reference to Figures 2 and 3. Each joint t comprises a hinge pin 11, which is brazed to a lower hinge plate 12 mounted on the outside leg brace member 1, and a journal bearing 13 of the deep groove ball bearing type. This type of ball bearing is utlised for the journal bearing 13 in order to provide a bearing of minimum width which is capable of tolerating the thrust forces imposed on it during use of the invention. The journal bearing 13 is clamped, by means of a bearing housing 14, to one face of an upper hinge plate 15 which is in turn attached to the lower end of the body brace member 9. A retaining nut 24 which is screwed onto a threaded end of the hinge pin 11 acts against the inner ferrule of the ball bearing to hold the hinge joint 6 together.

Adjacent the hinge joint 6, a forward facing outrigger 16 is pivotally attached to the outside leg brace member 1 by means of a shouldered screw (not indexed). A pin 17 is positioned in the outside leg brace member 1 to prevent rotational movement of the outrigger 16 upwards of the position shown in Figure 2. The pin 17 does not, however, prevent rotational movement of outrigger 16 downwards of the position shown. A tension spring 1S is attached at one of its ends to the projecting end of outrigger 16 and is attached at its other end to a mounting block 19 on upper hinge plate 15. The configuration of the hinge joint 6 is such that the tension spring 18 is unstretched when the leg is in its neutral position in alignment with the body. Thus, hyper extension (as previously defined) of the hip joint is resisted by action of the spring on the outside leg brace member 1 but forward extension of the leg with respect to the body, e.g.

when seating is unaffected by the tension spring 18, by virtue of the rotational movement of the outrigger 16. A spring 18 having a rate of 140 Ib.f/inch extension will permit sufficient hyperextension of the hip joint whilst adequately supporting the leg against its own weight during its forward movement for use of the abulation aid by a child having a body weight of 522 lb.

Arcuate stop members 20, which are attached to the lower hinge plate 12, and a stop pin 21, mounted in the mounting block 19 on upper hinge plate 15, co-operate to provide a positive overide stop to prevent inadvertent over extension of the hip joint in either direction. To enable the patient to sit down, this stop mechanism may be disen gaged to permit unrestricted movement of the legs by pulling a knob 22 which lifts stop pin 21 against the action of its bias spring 23.

In order to minimise the frictional forces in the hinge joint 6 during the forward swing of the leg, the ball bearing is preferably maintained in a substantially vertical position during this phase of the gait. This is achieved by laterally offsetting the ball bearings by an angle of 10 degrees with reference to the normal vertical position of the calipers such that the lower edges of the bearings are convergently directed. The body brace members 9 and the outside leg brace members 1 are curved to fit the body contours of the patient. To take account of this curvature and to mount the ball bearings with their correct offset angle upper hinge plate 15 and lower hinge plate 12 are both laterally offset at their ends by an angle of 10 degrees as shown in Figure 3.

The ambulation aid illustrated in Figures 1-3 is attached to the body of the patient by means of thoracic strap 7, abdominal strap 8 and thigh straps 3. It is also attached to the shoe of the patient by means of shoe mounting spurs 5. The shoe can be attached to a single flat spur member 5 of flat section to provide a rigid connection but this would necessitate that the whole of the sole of the shoe be curved to the shape of an arc drawn about the hip joint. In the preferred arrangement the shoe mounting spurs are of circular section and pass transversely through a through-bore in the heel of the shoe to permit hinged movement of shoe about the axis of the spur. By this means the sole of the shoe is able to conform to the ground surface irrespective of its angular position with respect to the hip joint. The rear surface of the heel is chamfered to provide maximum ground clearance during the forward swing, and the outside lateral edges of the sole are chamfered to minimise the effort required to perform a sideways rocking movement which is required for ambulation.

The gait adopted by a paraplegic patient having the bi-pedial ambulation aid of the invention and using this in conjunction with a conventional rollator for support, is illustrated schematically in Figure 4. The patient starts from position 1 in which both legs are in the neutral position in line with the trunk and in which the patient has adopted an upright stance using both legs to support his weight. From this position the patient places his weight on one foot, say the left foot as shown, by rocking the body laterally in the direction of this foot and by so raising the non-supporting right foot from the ground.

This rocking movement of the body is aided, as mentioned previously, by the chamfer given to the outside edge of the shoe soles.

The patient then leans backwards on his supporting leg to reach position 2 and hyper-extends the supporting hinge joint 6 thus stretching its tension spring 18. As the patient leans backward in this position his non-supporting right leg moves forward in its neutral position, the tension spring 18 effectively locking the hinge joint 6 for this leg against its own weight. The patient then may ground this leg to reach position 3 in which his weight is again supported by both legs. The chamfered rear edge of the shoe heel, which has been mentioned previously, helps the patient to maintain ground clearance under his shoe in the movement from position 2 to position 3. From position 3 the body weight is again taken by one foot, this time the right foot, and the patient rocks laterally towards the right which lifts the left foot from the ground and permits this to swing forward to the neutral position under the action of the extended spring, simultaneously the patient pulls on his rollator, or other similar supporting device, in order to gain the upright posture of position 4. At this point he may pause to take his weight on both feet before beginning ambulation again from position 1. Preferably, however the patient does not pause in position 4 but hyper-extends his right hinge joint by leaning backwards so bringing his left leg forward in its neutral position through position 5 to position 6 in which he may again support himself with both feet. Ambulation beyond position 6 is achieved by repeating the sequence of movements from position 3 onwards but using the opposite feet of course.

It can be seen from the foregoing description that the bi-pedial ambulation aid of the invention is in itself more cosmetically acceptable and also permits a more aesthetically acceptable and flexible gait than prior art ambulation aids. It will be apparent, to those of normal skill in the art, that many variations in the design and construction of the ambulation aid described may be made without departure from the scope of the invention as defined in the appendent

Claims (8)

claims. WHAT I CLAIM IS:

1. A bi-pedial ambulation aid for a paraplegic patient, comprising a truncal brace, a leg caliper for each leg, a hinge joint for each leg caliper by which this leg caliper is attached to the truncal brace at a position adjacent, in use thereof, the patient's anatomical hip joint, and a biasing means for each hinge joint by which, in use thereof, 'hyper-extension' of the corresponding anatomical hip joint (as hereinbefore defined) is resisted.

2. A bi-pedial ambulation aid as claimed in Claim 1 in which each biasing means comprises a tension spring, and a forward facing outrigger on the leg caliper close to the hinge joint, the tension spring acting between a position on the outrigger and a position on the truncal brace.

3. A bi-pedial ambulation aid as claimed in Claim 2 in which the outrigger is pivotally attached to the leg caliper in such a way as to permit limited rotational movement of the former to enable the spring to resist 'hyper-extension' of the anatomical hip joint (as hereinbefore defined) whilst not affecting forward extension thereof for seating.

4. A bi-pedial ambulation aid as claimed in any one of the preceding Claims in which the hinge joint comprises a hinge pin attached to either the truncal brace cr the leg caliper, and a ball or roller journal bearing mounted on the hinge pin, the journal bearing being laterally offset from the normal vertical position of the calipers by an angle of 10 degrees such that the lower edges of the bearings are inwardly directed.

5. A bi-pedial ambulation aid as claimed in any one of the preceding Claims com prisrg a means, independent of the biasing means, to limit forward and rearward extension of the thigh by limiting rotation of the hinge joint.

6. A bi-pedial ambulation aid as claimed in Claim 5 in which the means to limit forward and rearward extension of the thigh is disengageable to permit forward extension of the thigh for seating.

7. A bi-pedial ambulation aid as claimed in any one of the preceding Claims in which the leg calipers have transversely extending spur elements of circular cross section by which, in use thereof, the shoes of a patient can be secured to the leg calipers whilst allowing the shoes to hinge about the axis of the spur.

8. A bi-pedial ambulation aid substantially as hereinbefore described with reference to and as illustrated in the drawings accompanying the provisional specification.