Multi-Link Safety Knee
Activity Level and Body Weight Limits
|Activity Level||Body Weight|
Walking can now be safer, smoother, easier, and more graceful.
The M0780 Swan has a body weight limit of 75 kg, while the M0786 Swan100 has a body weight limit of 125 kg. Both offer the same basic functionality.
- Preventing Knee Bending During the First Half of the Stance Phase (the Dynamic Stabilization Mechanism)
When the Swan applies weight to the heel during full extension, the Swan's links use bouncing bumpers to absorb the impact by displacement (slight bending). When that happens, the front and back vertical links become nearly parallel, momentarily transferring the knee joint's center of rotation toward the hip joint and preventing knee bending during the first half of the stance phase.
During the mid-phase, the displacement of the Swan links is gradually reversed, restoring the four main links and allowing the knee to bend.
- The Bouncing Mechanism
Because the Swan links undergo elastic displacement (slight bending of 4° or less) during the first half of the stance phase, vertical repositioning of the center of gravity is reduced, while at the same time, the body absorbs stance-phase impact from the floor, allowing it to advance forward smoothly. As a result, walking consumes less energy, and enabling a smooth gait (with double knee action) that is very close to a normal walk.
The duration, sensitivity, and volume of the bounce can be adjusted to suit the user's body weight and activity level by adjusting the inclination of the Swan and the amount of compression by the bouncing bumper.
The Hydraulic Cylinder
- Light Hydraulic Resistance
Hydraulic knees are considered to have a heavier swing than pneumatic knees, but Swan has been designed with a low amount of hydraulic resistance to provide a more comfortable walk for low and medium-activity users.
By reducing the amount of flexion resistance in the pre-swing, we were able to get that light-swing feeling that pneumatic models have. At the same time, Swan offers progressively increasing resistance in response to walking speed during first half of the swing phase (the acceleration phase) for smooth knee motion.
- Pace Matching
- The small, easy-to-control hydraulic cylinder can adapt to a walking cadence of up to 105 steps per minute thanks to its fluid characteristics. It adapts to a wide range of speeds, from a "gentle stroll" which requires light resistance, to a "speed walk" which requires strong resistance.
A Comment from the Developer
We analyzed the vector of the load sustained by the knee joint while walking with a prosthetic leg, and in order to achieve dynamic stability, we outfitted it with five links. The redundant links satisfy the difficult-to-meet conditions for achieving both safety and comfort. We worked on a design that would include functionality for "safe and comfortable walking without fatigue" as well as "gracefulness," and also kept its appearance while in the sitting position—something usually overlooked—in mind. Normalization includes users giving up the urge to hide their prostheses. We designed this knee joint with that in mind.
- The front S-shaped link prevents interference with the socket when the knee is bent. We narrowed the design of the shinbone part that connects to the bottom.
- We made no compromises with the hydraulic cylinder that cushions the rear links, cutting it from a single block of aluminum alloy to make it very strong and light-weight.
- To prevent it from pinching clothing or fingers, we fitted it internally with an extension stopper. Its overall round contours give it a friendly appearance.
Even though the users may not realize it, this product has a five-link structure with a dynamic stabilization mechanism (preventing knee bending through link geometry) and bouncing bumper that allow for safe, comfortable, worry-free walking and an attractive gait. We drew a clear line regarding traditional "hide the handicap" designs, designing instead a prostheses that was meant for showing, and we hope this will be encouraging for both users and those around them as well.
|Body Weight Limit||75 kg||125 kg|
|Weight||670 g||935 g|
|Overall Length||164 mm||198 mm|
|Overall Width||63 mm||76 mm|
|Material||Aluminum Alloy||Aluminum Alloy and Stainless Steel|
|Swing Phase Control Mechanism||Hydraulic Cylinder|
|Stance Phase Control Mechanism||Bouncing Mechanism|
|Maximum Bend Angle||150°|
Winner of the 2003 Good Design Award
Imasen Engineering Corporation was presented the 2003 Good Design Award by the Japan Industrial Design Promotion Organization (JIDPO) for its Lapoc System prosthetic multi-link safety knee, the M0780 Swan. This marked the second time Imasen has been presented with the Good Design Award for a prosthetic limb product; Imasen previously won the award in 1997 for its SL prosthetic leg, becoming the prosthetic industry's first recipient of the award.
The Good Design Award is the successor to the Good Design Products Selection System (the G-Mark System) launched by the Department of Trade and Industry in 1975, and since its new start in 1998 as JIDPO's Good Design Award program, it has served as a comprehensive design values and recommendation system, something unique in Japan. JIDPO's activities center around activities that can tangibly contribute to the culture and lifestyle of a new era, evaluating infrastructure that will lead to "good design," and seeing that infrastructure used to develop "more prosperous lifestyles" and "good businesses" that embody "good design."
The Origin of the Nickname
The Swan is the second knee joint in the Lapoc product line, after the M0770 BASS, to earn a nickname. It was chosen after staff involved with Lapoc solicited the rest of the company employees for ideas. If one considers the reason for the overwhelming support that this contender earned above the second-place contender and those below it, the case for "Swan" must come not only from the shape of the product, but with the grade with which swans move as they glide along with the tide, and the name served to remind everyone of what they had hoped for in this product. When the product first went on sale, the name met with some resistance among our customers, but now, when we hear our customers talk about the product, they refer to it not by its module number, but by its nickname, "Swan." Swan is also the first Lapoc product to be given its own logo. The logo modifies the letter "S" to look like a swan, adding a sense of playfulness to the design.
The logo of the M0786 Swan100 incorporates a black swan to lend an image of enhanced durability and strength.