VARIABLE ANGLE LIMB SUPPORT

Field of the Invention

[0001] The present invention generally relates to a device for supporting a limb in various angular positions, especially for supporting a lower limb in radiographic projection of the patello-femoral joint.

Background of the Invention

[0002] Radiographic projection of the patello-femoral joint is currently the best projection to demonstrate patello-femoral pathologies, particularly in the evaluation of patello-femoral disorders such as chondromalacia and recurrent subluxation. In common medical practice, a patient's lower limb is supported by a conventional fixed angle support, which provides a fixed knee-flexion of 30-40 degree between the long axis of the tibia and the long axis of the femur. A horizontal X-ray beam is directed towards the patello-femoral joint space, while the patient manually holds a film cassette to capture the penetrated X-ray beam.

[0003] FIG. 1 shows two types of conventional fixed angle supports, each having a fixed supporting angle theta in a range of 30-40 degree. Although the 30-40 degree knee-flexion is sufficient for demonstration of the patello-femoral joint space, it may not be optimal for certain pathological diagnosis, such as subluxation of the patella. It is desirable to obtain a series of patello-femoral projections at various degrees of knee- flexion for further diagnostic information.

[0004] In addition, the manual holding of the film cassette by the patient is unstable, resulting in distortion of the projection image, which impairs the required information for diagnosis. And the patient's close position towards the film cassette increases the overall radiation dose received, posing threat to the health of the patient.

Summary of the Invention

[0005] The present invention provides a limb support with a broad range of adjustability to support a limb at various angular positions. The limb support comprises a base frame disposed on a supporting surface, a pivoted structure in an inverted V-shape mounted on the base frame for supporting the limb at various pivot angles, and adjustment means for adjusting the pivot angle of the pivoted structure, wherein the distance from the apex of the pivoted structure to the supporting surface is maintained for different pivot angles. The pivoted structure comprises a first support member and a second support member, which are pivotally connected to each other, forming the inverted V-shape. When the support is used to support a lower limb in radiographic projection of the patello-femoral joint, the relative position of the patello-femoral joint with respect to the supporting surface remains unchanged during projections at various knee-flexion angles. Therefore, no adjustment is required to the height of the radioactive source.

[0006] According to one aspect of the invention, there is provided a limb support wherein the base frame has a J-shaped structure, which comprises a horizontal portion in contact with the supporting surface, and an arc portion extending upwards, and wherein the distal end of the first support member is supported by the horizontal portion of the base frame, whilst the distal end of the second support member is maneuverable along the arc portion of the base frame.

[0007] According to another aspect of the invention, there is provided a limb support, wherein the arc portion of the base frame is part of a circle. The circle has the center at the apex of the pivoted structure, which is of a pre-determined distance from the supporting surface; and the radius being the length of the second support member. [0008] According to yet another aspect of the invention, there is provided a limb support, wherein the adjustment means comprises a plurality of sockets carved on the arc portion of the base frame, and a pin extended from the distal end of the second support member, wherein the distal end of the pin is operable to sit in any of the sockets so as to adjust the pivot angle between the first and second support members.

[0009] According to another aspect of the invention, there is provided a limb support, wherein the adjustment means comprises a groove carved along the arc portion of the base frame, a pin extended from the distal end of the second support member, the pin having the distal end disposed and restrained in the groove and operable to slide therein, and an extendable/retractable structure disposed and linking between the base frame and the second support member; wherein the longitudinal length of the extendable/retractable structure is adjustable, so as to adjust the pivot angle between the first and second support members. In one embodiment, the extendable/retractable structure is operable to extend/retract by a telescopic mechanism built therein. In another embodiment, the extension/retraction is motorized.

[0010] According to yet another aspect of the invention, there is provided a limb support, wherein the longitudinal lengths of the second support member and the horizontal portion of the base frame are adjustable so as to support limbs of various lengths. In one embodiment, the length adjustment is achieved by telescopic mechanisms built therein.

[0011] According to further another aspect of the invention, there is provided a limb support, further comprises a detachable holder. When the limb support is used in radiographic projection of the patello-femoral joint, the holder is operable to hold the X- ray film cassette. In one embodiment, the detachable holder comprises an upright post detachably connected to the base frame, and a vertical frame pivotally attached to the post for holding the X-ray film cassette.

[0012] The objectives and advantages of the present invention will become apparent from the following detailed description of embodiments thereof in connection with the accompanying drawings.

Brief Description of the Drawings

[0013] Preferred embodiments according to the present invention will now be described with reference to the Figures accompanied herein, in which like reference numerals denote like elements.

[0014] FIG. 1 shows two conventional fixed angle supports for the radiographic patello-femoral projection.

[0015] FIG. 2 shows a perspective view of a variable angle limb support device in accordance with one embodiment of the present invention.

[0016] FIG. 3 A shows a side view of the device in FIG. 2, illustrating the relative motion of the second support member during angular adjustment of the device, whilst

FIG. 3B shows an enlarged view of the adjustment means in accordance one embodiment of the present invention.

[0017] FIG. 4A shows a perspective view of a variable angle limb supporting device with motorized adjustment means in accordance with another embodiment of the present invention; FIG. 4B shows an exploded view of the motorized adjustment means; and FIG. 4C and 4D show side views of the device with the extendable/retractable structure at the most retracted and extended positions respectively.

[0018] FIGs. 5 A and 5B show side views of a variable angle limb support device for supporting limbs of different length, in accordance with yet another embodiment of the present invention; FIG. 5C shows a telescopic structure of the base frame shown in FIGs.

5A and 5B.

[0019] FIG. 6 A shows a perspective view of a variable angle limb support device with a detachable holder in accordance with a further embodiment of the present invention, whilst FIG. 6B shows the device in use for the radiographic patello-femoral joint projection.

Detailed Description of the Invention

[0020] The present invention may be understood more readily by reference to the following detailed description of certain embodiments of the invention. However, it will be understood by those skilled in the relevant art that the present invention may be practised without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention.

[0021] FIG. 2 shows a perspective view of a variable angle limb supporting device in accordance with one embodiment of the present invention. The device 100

comprises a base frame 110 disposed on a supporting surface 106, an inverted V-shaped pivoted structure 120 mounted on the base frame 110 for supporting the limb in various angular positions, and adjustment means 130 for adjusting the pivot angle formed by the pivoted structure 120. [0022] FIG. 3 A shows a side view of the device 100 in FIG. 2. The base frame

110 comprises a vertical supporting structure 111, and a J-shaped structure 112. The J- shaped structure 112 has a horizontal portion 113 disposed on the planar supporting surface 106 (not shown in FIG. 3A), and an arc portion 114 extending from a first end 113a of the horizontal portion 113 and stretching upwards. The lower end Ilia of the vertical supporting structure 111 is connected perpendicularly to a second end 113b of the horizontal portion 113.

[0023] In one embodiment of the base frame 110, the vertical supporting structure

111 is rectangle shaped. In another embodiment, the vertical supporting structure 111 has a handle 115 attached for carrying and moving the device 100. In yet another embodiment, a horizontal crosspiece is perpendicularly attached to the horizontal portion 113 for securing a stable support of the device 100 on the supporting surface 106.

[0024] Still referring to FIG. 3A, the pivoted structure 120 has a first support member 121 and a second support member 122 pivotally connected to each other, forming the inverted V-shape and defining a pivot angle theta. The distal end 121a of the first support member 121 is pivotally connected with the upper end 111b of the vertical supporting structure 111, whilst the distal end 122a of the second support member 122 is maneuverable along the arc portion 114 of the base frame 110. The relative position of the distal end 122a of the second support member 122 to the arc portion 114 is controlled by the adjustment means 130, thereby determining the degree of the pivot angle theta formed by the pivoted structure 120.

[0025] In one embodiment of the pivoted structure, each support member 121 or

122 comprises a pivot arm, at least one bar attached to the pivot arm for defining a planar surface, and a cushion disposed on the planar surface for supporting the limb. [0026] FIG. 3B shows an enlarged view of the adjustment means 130 for adjusting the pivot angle theta formed by the pivoted structure 120 in accordance with one embodiment of the present invention. The adjustment means 130 comprises a pin 131

extending from the distal end 122a of the second support member 122, and a plurality of sockets 132 carved along the inner surface of the arc portion 114 of the base frame 110. The tip of the pin 131 is operable to sit in any of the sockets 132, to form a pin-socket joint. Once a pin-socket joint is secured, the position of the pivoted structured 120 on the base frame 110 is locked, and the pivot angle theta is fixed. The location of the sockets 132 along the arc portion 114 of the base frame 110 determines the range of the pivot angle theta and the adjustable angular interval.

[0027] In one embodiment of the pin, the pin 131 is T-shaped, having a first portion 131a in line with the longitudinal axis of the second supporting member 122 and a second portion 131b perpendicular thereto and operable to fit in the linear sockets 132. In another embodiment, the pin 131 is rod-shaped with a round tip fitting in the point sockets 132.

[0028] Now referring back to FIG. 3A, the relative motion of the pivoted structure 120 controlled by the adjustment means 130 is illustrated. When the distal end 122a of the second support member 122 is moved upwards and the pin 131 is locked in the socket 132 closer to the upper end of the arc portion 114 of the base frame 110, the pivot angle theta is decreased. And the arc portion 114 of the base frame 110 and the adjustment means 130 are so configured that during adjustment, the distance from the apex of the pivoted structure 120 to the supporting surface 106 (not shown in FIG. 3A) is maintained.

[0029] In one embodiment, the arch portion 114 is configured as part of a circle.

The circle has the center at the apex of the pivoted structure, which is of a pre-determined distance from the supporting surface 106; and the radius being the longitudinal length of the second support member 122 plus that of the pin 131.

[0030] FIG. 4A shows a perspective view of a variable angle limb supporting device with motorized adjustment means in accordance with another embodiment of the present invention. The device 200 has a similar configuration with the early embodiment 100 shown in FIG. 3, except for the adjustment means. The motorized adjustment means

230 comprises a groove 232 carved along the inner surface of the arc portion 214, a pin

231 extending from the distal end 222a of the second support member 222, the tip of which is disposed and operable to slide in the groove 232, an extendable/retractable

structure 234 disposed between the horizontal portion 213 of the base frame 210 and the second support member 222 for positioning the second support member 222, a motorization unit 233 secured to the horizontal portion 213 of the base frame 210, and a coupling means 235 for coupling the motorization unit 233 to the extendable/retractable structure 234.

[0031] FIG. 4B illustrates an exploded view of the motorized adjustment means

230 shown in FIG. 4A. The extendable/retractable structure 234 includes a hollow housing 237 and a shaft 236 operable to extend therein. The housing 237 has a first end 237a with internally carved threads 237c, and a second end 237b pivotally connected to the second support member 222. The shaft 236 has a first end 236a rotably connected to a holder 239 via a bearing 238, and a second end 236b with external threads 236c to engage with the internal threads 237c of the housing 237. The holder 239 is pivotally mounted on the horizontal portion 213 of the base frame 210. The motorization unit 233 comprises a power 233a (not shown in FIG. 4D), a motor 233b (not shown in FIG. 4D) electronically connected to the power, and a controller 233c (not shown in FIG.4D) for controlling the speed and rotation direction of the motor. The coupling means 235 is a pair of bevel gears. The first bevel gear 235a is mechanically connected to the motor 233b, whist the second gear 235b is coupled with the shaft 236.

[0032] In operation, when the power 233a is switched on and the controller 233c is actuated, the motor 233b drives the rotation of the shaft 236 through the coupled bevel gears 235. The interaction between the shaft 236 and the housing 237 via the engaging threads causes the housing 237 to move along the longitudinal axis of the shaft 236, and to push or pull the second support member 222 supported thereon, with the pin 231 sliding up or down along the groove 232. In this way, the position of the pivoted structure 220 and the pivot angle theta is adjusted as desired. FIG. 4C and 4D illustrate side views of the device 200 with the extendable/retractable structure 234 at the most retracted and extended positions respectively.

[0033] In one embodiment of the controller, the controller 233c is a fuzzy control system. In another embodiment, the controller 233c is an analogue control system. In yet another embodiment, the controller 233c is a digital control system.

[0034] In one embodiment of the coupling means, the coupling means 235 is a worm gear.

[0035] In one embodiment of the device, the device 300 has the similar extendable/retractable structure 334 as shown in FIG. 4B for angular adjustment of the pivoted structure 320, however, which is manually powered. A handle is attached to the shaft 336 for manually driving the rotation.

[0036] In another embodiment of the device, the extendable structure/retractable

234 is a telescopic structure, the extending/retracting movement of which is locked or released by locking means.

[0037] FIG. 5A and 5B show a variable angle limb support device in accordance with yet another embodiment of the present invention. The device 500 has a similar configuration with the earlier embodiment 100 shown in FIG. 3, except that the longitudinal lengths of the second support member 522 and the horizontal portion 513 of the base frame 510 are adjustable by built-in telescopic structures 540, so as to adapt the device 500 to limbs of different lengths. Due to the similar structure, only the telescopic structure 540 built in the horizontal portion 513 of the base frame 510 is described below in detail.

[0038] FIG. 5C shows an enlarged view of the telescopic structure 540 built in the horizontal portion 513 of the base frame 510 as illustrated in FIG. 5B. The telescopic structure 540 has a receiving member 541, and an extending member 542 positioned and operable to slide therein. The extending member 542 has a plurality of lock apertures 543 along the longitudinal axis, each of which can be aligned with a lock aperture 544 (not shown in FIG. 5C) in the receiving member 541. A locking pin 545 is operable to be inserted through the pair of aligned lock apertures so as to fix the relative position of the receiving member 541 and extending member 542, thereby defining the longitudinal length of the horizontal portion 513.

[0039] The telescopic structures 540 of the device 500 are so configured that the length of the second support member 522 and the horizontal portion 513 of the base frame 510 can be adjusted proportionally. As a result, the distance H from the apex of the pivot structure 520 to the supporting surface 506 is maintained throughout adjustment.

FIG. 5 A and 5B show side views of the device with the telescopic structures 540 at the most retracted and extended positions respectively.

[0040] In one embodiment of the device 500, the telescopic structure 540 is employed to connect the pin 531 to the second support member 520. [0041] FIG. 6 A shows a perspective view of a variable angle limb support device in accordance with a further embodiment of the present invention. Compared to the embodiment 100 shown in FIG. 3, the device 600 further comprises a detachable holder 650. The holder 650 has a post 651, an arm 653 connected to the post, and a frame 652 supported by the arm 653. The post 651 is detachably mounted at the side of the vertical supporting structure 611. The arm 653 is operable to pivot about the post 651 and move along the length of the post 651. The frame 652 is in a 90 degree rotated U shape and mounted to the arm 653 via a linker 654.

[0042] FIG. 6B shows a perspective view of the device 600 in FIG. 6A when it is in use for the radiographic projection of patello-femoral joint. The upper leg 602 of a patient 601 is placed on the first support member 621, and the lower leg 603 on the second support member 622, wherein the knee cap 604 is supported on the apex of the pivoted structure 620. The pivot angle theta corresponds to the knee flexion. An X-ray film cassette 605 is disposed in the frame 652. The position of the film cassette 605 can be adjusted by pivoting the arm about 653 and/or by raising or lowering the arm along the post 651. The patient 601 can comfortably lie back and away from the X-ray film cassette 605 during projection process, to minimize the exposure to the X-ray. [0043] While the present invention has been described with reference to particular embodiments, it will be understood that the embodiments are illustrative and that the invention scope is not so limited. Alternative embodiments of the present invention will become apparent to those having ordinary skill in the art to which the present invention pertains. Such alternate embodiments are considered to be encompassed within the spirit and scope of the present invention. Accordingly, the scope of the present invention is described by the appended claims and is sported by the foregoing description.