Patent Application
20140276094
a. Technical Field
This invention relates generally to an apparatus for capturing the shape of a foot for an orthosis and, more specifically, to an apparatus for optical scanning of a human foot for orthosis.
b. Background Art
There are several known types of methods for capturing the shape of the foot for orthosis. One type is a full weight bearing method where the surface of the foot is captured while the patient is standing. In embodiments, plaster cast material is wrapped around the foot, and often the patient stands on a foam block or a hard surface. In other embodiments, the patient stands on a clear glass surface and the weight-bearing image of the foot is scanned by an optical scanner through the glass. With full-weight-bearing methods, the soft tissue is excessively deformed so that there is little contour left, and the topographical surface becomes the same shape as the flat glass or weight bearing surface. An example of a soft tissue envelope 18 of a foot in a full-weight-bearing method is shown in
A second type of method is to capture the foot in a non-weight-bearing position. This may be accomplished using a suspension cast/capture technique where the foot is held in the correct segmental position to replicate mid-stance using one hand to position and hold the foot. This is often the ideal technique for positioning but is technically difficult and, being non-weight-bearing, provides little to no soft tissue deformation. An example of the soft tissue envelope 22 of a foot in a non-weight bearing position is shown in
A third type of method is a partial-weight-bearing capture. In this method only part of the body weight is utilized to compress the soft tissue while still allowing for proper foot segment positioning. An example of the soft tissue envelope 20 of a foot in a partial-weight-bearing technique is shown in
An embodiment of an apparatus for capturing the shape of a foot may include an optically-transparent flexible membrane configured to receive the foot, a support structure configured to retain the membrane, and an optical scanner configured to capture an image of the foot through the membrane. The membrane may comprise linear low-density polyethylene having a thickness of between about 60 mil and about 120 mil. The membrane may have a generally uniform thickness, or may have a variable thickness. In an embodiment, the optical scanner may be configured to capture an image of the foot from the side.
Various embodiments are described herein to various apparatuses, systems, and/or methods. Numerous specific details are set forth to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments as described in the specification and illustrated in the accompanying drawings. It will be understood by those skilled in the art, however, that the embodiments may be practiced without such specific details. In other instances, well-known operations, components, and elements have not been described in detail so as not to obscure the embodiments described in the specification. Those of ordinary skill in the art will understand that the embodiments described and illustrated herein are non-limiting examples, and thus it can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments, the scope of which is defined solely by the appended claims.
Reference throughout the specification to “various embodiments,” “some embodiments,” “one embodiment,” or “an embodiment”, or the like, means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in various embodiments,” “in some embodiments,” “in one embodiment,” or “in an embodiment”, or the like, in places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Thus, the particular features, structures, or characteristics illustrated or described in connection with one embodiment may be combined, in whole or in part, with the features, structures, or characteristics of one or more other embodiments without limitation given that such combination is not illogical or non-functional.
Referring to the drawings, in which like numerals refer to the same or similar elements in the various drawings,
There are 3 key functional joint segments that come into play in the foot 10 during ambulation. One is the ankle-subtalar joint complex 12. While the ankle and subtalar joint are separate anatomical joints, they work together in the positioning of the rear foot that comprises the talus and calcaneus bones. The second functional segment is the mid-tarsal joint 14, which determines the position if the forefoot. The mid-tarsal joint 14 also is two anatomical joints arising from the calcaneo-cuboid and talo-navicular articulations. The third functional segment is the first ray or medial column 16 of the foot that is comprised of the first metatarsal and medial cuneiform bones and their articulations. Together these functional segments 12, 14, 16 of the foot provide the complex three dimensional motions required for efficient ambulation.
To allow for the dynamic movement provided by the functional segments 12, 14, 16 of the foot 10 while using a static device such as a foot orthosis, one period of the gait cycle may be chosen as a reference point for the position and topographical surface shape of the orthosis, and the foot measured for an orthosis while in that position. One period that may be selected is mid-stance, when the ankle-subtalar joint 12 is in its “neutral” or central articulated position, the mid-tarsal joint 14 is in a “locked” or maximally pronated position and the medial column 16 of the foot 10 is plantarflexed. If the foot 10 is positioned in this mid-stance position and the topographical surface of the foot 10 is captured while in this position, that surface may be effectively replicated with an orthosis shell that, when placed under the foot, will press against the soft tissue that in turn pushes the osseous tissue to replicate the original position. Thus, it is important to capture the topographical shape of the foot with proper soft tissue deformation.
To overcome the deficiencies in known techniques for capturing a foot for producing an orthosis, a partially-elastic, clear membrane may be used to deform the soft tissue of the foot. The membrane may have some plastic memory (i.e., may be partially elastic), so as the joint is moved through its range of motion to find the proper neutral position, the membrane will not permanently be deformed. This property may offer an advantage over foam for a partial-weight-bearing procedure, as the foam may be inelastic (i.e., may collapse into a compressed state). In contrast, even when a partially-elastic membrane is stretched, the foot can still be manipulated while the soft tissue compression of the heel dynamically changes with the changing position of the proximal segment. This agrees with the theory of how a foot orthosis works. That is, the shape of the curvature of the heel may determine the reactive forces acting on the heel and proximal joint segments. Similarly, the theory is that as the proximal joints are positioned, the contour of the soft tissue will change.
Similarly, the rotational axis of the metatarsal phalangeal joints 32 may be manipulated to prevent excessive dorsiflexion under the load of the membrane. A physician may push the metatarsal phalangeal joints 32 into the membrane (i.e., to deform the membrane and lessen the pressure on the joints) to avoid retrograde plantarflexion of the metatarsal heads.
The support mechanism may be designed or otherwise configured to provide a selected uniform or variable tension on the foot 10 by the membrane 34. For example, the physical position of the support mechanism may be altered (e.g., shifted higher or lower) to increase or decrease the tension of the membrane against the foot. In addition, the shape of the support structure may be altered to provide more uniform or more variable tension. For example, in an embodiment, a generally rectangular support structure may be used to provide uniform tension. In other embodiments, a support structure having non-parallel sides may be used for variable tension, for example only. In any embodiment, secure edge connectors may be important—edge connectors slipping may unexpectedly reduce membrane tension.
In addition to the support structure, properties of the membrane 34 itself may be configured for a desired procedure. A membrane 34 having uniform thickness may be selected, in embodiments, to produce uniform tension and, thus, uniform pressure across the foot 10. In other embodiments, variable tensioning may be achieved by 1) varying the thickness of the membrane 34 material or 2) stretching the membrane 34 beyond the elastic region of the stress-strain curve of the membrane 34 and into the plastic region, thereby over-stretching and deforming the membrane 34 in areas to achieve proper tensioning of the membrane 34 against the foot 10. Variable tension in the membrane 34 may be desired to produce more compressive forces across some areas of the foot 10 while allowing for less compressive forces in other areas of the foot 10. In an embodiment, the area of the membrane 34 in which the patient's toes are to be depressed may have a decreased compressive load to minimize toe dorsiflexion while compressing the foot onto the membrane 34. In an embodiment, the medial column 16 or first ray 30 of the foot 10 may have reduced tension, allowing for plantarflexion, while the lateral column has greater upward loads to pronate or lock the mid-tarsal joint 14, while the medial rearfoot may have greater compressive force than the lateral rearfoot to invert (supinate) the rearfoot.
The support structure 44 may comprise, in an embodiment, an elliptical frame 48 and support arms 50 surrounding a rectangular portion 52. The rectangular portion 52 may include an upper surface 54 which may include edge connectors 56 configured to couple the membrane 34 with the support structure 44. The frame 48 may comprise a shape other than an oval, in an embodiment. Similarly, the rectangular portion 52 may comprise a shape other than a rectangle, in an embodiment. The support structure 44 may comprise materials and construction known in the art.
The membrane 34 may be optically transparent (e.g., generally transparent to the optical scanner 42), and may be made of a plastic or polymer film such as, for example only, linear low-density polyethylene (LLDPE) coupled with a membrane frame 60. The membrane frame 60 may include holes or other structures for coupling with the edge connectors 56. The membrane may be flexible and partially elastic. In an embodiment, the membrane may be 120 mil stretch wrap. In various embodiments, the membrane 34 may include thicknesses ranging from about sixty (60) mil to about one hundred-twenty (120) mil, for example only, though the membrane 34 is not limited. Thinner material (e.g., about 60 mil) may be preferred for lighter patients, and thicker material (e.g., about 120 mil) for heavier patients.
The membrane 34 may provide an advantage over known orthosis measurement devices. In known devices including optical scanners, a solid glass plate is often used which, as noted above, results in a full-weight-bearing procedure and improper soft tissue deformation. In other devices, if a membrane is included, the membrane generally is partially or completely opaque to the optical seamier. Accordingly, such devices generally measure the membrane itself, rather than the foot 10. Measuring the membrane, however, may make detection of the edge of the foot 10 difficult, which may create difficulties in properly sizing an orthosis based on the measurement. In contrast, an optically-transparent membrane 34 allows for the foot itself to be measured by the optical scanner 42.
The track 46 may be provided circumferentially about the frame 48 and below the upper surface 54 and below the membrane 34. The track 46 may be configured to guide a carrier 58 coupled with the optical scanner 42 to enable the optical scanner to image the entire foot 10 from the side of the foot 10. The movement of the optical scanner 42 about the foot 10 may allow a true three-dimensional image of the foot 10 to be captured.
In an exemplary procedure, a physician may attach a membrane 34 to the support structure 44 by placing the membrane frame 60 on the upper surface 54 of the rectangular portion 52 of the support structure 44. The physician may then press a patient's foot 10 down into the membrane 34 (e.g., the lateral center of the membrane 34) to place appropriate pressure on the patient's foot 10. The physician may flex the patient's foot 10 and the membrane 34 to place the foot 10 in the proper neutral position, substantially as described above. In an embodiment, the physician may press the foot 10 down such that the entire foot is below the upper surface 54. The physician may then activate the optical scanner 42. The carrier 58 (and, with it, the optical scanner 42) may orbit at least once about the entire circumference of the track 46, or a subset thereof as is necessary or directed. While conducting such an orbit or partial orbit, the optical scanner 42 may capture an image or a series of images of the foot 10, from the side of the foot 10, through the membrane 34. The optical scanner 42 may transmit a signal to a computer, which may compile the image or images captured of the foot 10 to create a three-dimensional rendering of the foot 10 as positioned. The three-dimensional rendering of the foot may be replicated, in an embodiment, to create an orthosis for the foot.
Although a number of embodiments have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this disclosure. For example, all joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the spirit of this disclosure as defined in the appended claims.
