Surgery: splint – brace – or bandage – Orthopedic bandage – Splint or brace
Reexamination Certificate
1999-10-18
2002-06-11
Pothier, Denise (Department: 3764)
Surgery: splint, brace, or bandage
Orthopedic bandage
Splint or brace
C602S016000
Reexamination Certificate
active
06402713
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to orthosis', and in particular an orthosis designed to provide a structural movable mechanism to support a human knee joint. Such devices are usually known as a knee brace or knee orthosis. Also described is a hinge mechanism for use in such an orthosis.
2. Description of the Prior Art
Injuries to the human knee are common and can be the result of many different occurrences from athletic injuries to the onset of old age. A healthy knee operates to provide forward and backward hinging motion, tilting, rotating, and sliding motion of the upper leg or femur relative to the lower leg or tibia.
The knee joint consists of two principle bony structures, an upper bone, the femur, and a lower bone, the tibia. The femur has two large rounded knuckles of different sizes with the center located rearward of the center line of the vertical component of the bone. The articular surfaces on the knuckles have some of their contact surface facing downwards towards the tibia and a smaller, radiuses surfaces facing the back of the leg. The tibia, on the other hand, has a large relatively flat articular surface, primarily facing upwards towards the femur. When the human knee is straightened to full extension the lower portion of the large rounded knuckle of the femur sits a top the upwards facing articular surface of the tibia.
When the knee is moved by flexing the joint from this straightened position, the femur, while rotating on the rearward portion of the knuckle will also slide forward on the flat downwards facing portion of the articular surface of the femur. While this is occurring the femur may also tilt from side to side during the flexion process.
All of these complex motions, in a healthy knee joint, are controlled by a complexity of ligaments, muscles and tendons. When an injury occurs many of these elements can be torn from their attachment points in the skeletal or musculature, rendering them useless in controlling of the motion of the femur with respect to the tibia. In many cases, as the result of these types of injuries, the knee can no longer flex and extend normally and may in fact, dislocate and re-injure itself.
The basic understanding of the mechanism of these types of injuries are well understood by the medical profession. Numerous attempts have been made to externally and internally replace the torn element with a mechanical apparatus which would act similarly to the torn element. Traditionally this apparatus, which may include orthosis, or even ligamental repair, has resulted in a restriction of overall motion of the joint and may, in many cases, cause re-injury or dislocation of the knee. An orthosis is generally used to attempt to support the knee externally and it would have an upper cuff, wrapped around the upper leg and a lower cuff, wrapped around the lower leg, which would likely be connected together via a linkage. This linkage was usually a simple hinge of some fashion mechanically attached to the upper cuff and directed downwards where it would be fastened to the lower cuff.
It is understood that the knee tilts, slides and pivots during flexion and extension when healthy. It is also apparent that an orthosis for the knee with a simple hinge on the side(s), does not. In practice this means the orthosis restricts all types of movement of the knee preventing the knee from functioning as it should.
When an orthosis, as described above, is placed on an injured knee, the upper and lower cuffs are unable to remain conformal to the leg as the knee is flexed. This results in a scrubbing action between the leg and brace often resulting in skin irritation. Further detrimental effects, as the orthosis separates from the leg as the knee is flexed, the orthosis loses contact with the leg allowing the orthosis to descend down the leg. It is obvious that if the orthosis is sliding down the leg it cannot support the knee and may in fact, create hazards of its own to the knee while being used.
The effects of the knee orthosis restricting the movement of the knee in this fashion, can prevent the wearer of the orthosis from doing even simple things like sifting into a low chair. It is often understood by wearers of the orthotic devices, that if they should try to exercise or participate in athletic endeavours they may be gravely risking re-injury of the joint. In addition to this and because the orthosis cannot slide and tilt the way the knee does, the orthosis creates internal forces in the knee joint further adding to the wearers discomfort.
After considerable effort, the joint motion of the human knee has begun to be understood. Its complex movements can be generally described in the following:
When in full extension, the lower most portion of the femurs articular surfaces are in direct contact with the upward facing plateau surfaces of the tibia. As the knee begins to flex, the femur will begin to slide in a forward direction on the surface of the tibial plateau and as the result of the differences in the femurs knuckle sizes, begin a slight tilting motion. As the knee continues to flex, the larger radius knuckle of the femur begins to rotate on the tibial plateau, and due to the center of rotation of the knuckle being behind the center line of the vertical portion of the femur, this lifts the front of the femur articular surface from contacting the forward most portion of the articular surface of the tibia. While lifting at the front of femur is taking place, and due to the difference in knuckle size of the femur, an external rotation of the femur with respect to the tibia is introduced.
As the knee continues to flex the relative displacements in translation forward, rotation outwards, lifting upwards and tilting sideways, begin to increase. In a standard orthosis, where these motions are not included in the mechanical joint design, these relatively large displacements cause internal pressure on the muscle-skeletal structure due to the restrictive nature of the orthosis. This can, and does, when used on an injured leg where the ligamental structure has been torn away from the bone, force the femur into an abnormal, if not extremely uncomfortable positions. This abnormal motion has been known to accelerate degradation of the articular surfaces of the femur and tibia. During that abnormal displacement of the femur, it is often noted on wearers of standard orthosis, that significant gaping of the upper cuff with respect to the thigh muscle. This generally results in the brace sliding downwards with each step, resulting in the wearer holding the top of the brace to prevent this downward migration. This leaves the knee joint completely unsupported and possibly resulting in further injury.
As is well understood by the medical profession, people come in all different sizes and shapes. The problem often faced by the designers of the knee orthosis, is its suitability to be manufactured. Many orthotic manufacturers have been unable to reach a compromise between manufacturability, adaptability to the many shapes and sizes of people and functionability after the orthosis has been manufactured. An example of this is when two hinges are mounted on either side of the knee connected by an upper and lower cuff.
Contributing to discomfort is the positioning of the strapping system used to hold the orthosis on to the leg. It has been well understood that the Anterior Cruciate Ligament will prevent, when fully attached, the femur from sliding backwards off the tibial plateau. This is most pronounced when the leg is slightly bent and the center line of the femur is directed in a rearward fashion towards the back of the tibial plateau. The problem with the placement of many strapping systems knee orthosis is that they allow the head of the femur to continue in a rearwards motion often to the point of dislocation. An example of this style of dislocation is often seen in skiing when the ski bindings do not release and the skier falls directly forward resulting in a backwards displacement of the femur on the tibia
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