Knee mechanics comparisons

These are some videos that show how implants and synthetics can be important or how they can aid the mechanical function of the human knee.

This is actually a very interesting video of the knee joint which shows the movement of a normal knee that ha snot undergone knee replacement surgery, but is rather a healthy knee.

http://www.youtube.com/watch?v=dq1pHLudtKU

This link contains another video that compares a normal knee's motion to one that has undergone replacement. It shows that there are some variable changes in the mechanical ranges of the implant compared to the actual knee that one has.

Knee Implant Mechanics and Associated Factors

Factors Associated with Knee Replacement:

Patient Weight: Patient weight is highly important for knee replacement because the knee’s are parts that bear the most weight in the body. They are the lower extremities that provide support to the body. Also, they are the ones that spring the body into motion. That is why the knee joints are the fastest to wear out and deteriorate. The amount of activity done with the knee outweighs all other activities with different limbs. Artificial implants should be able to sustain major activity of the knees and they should be able to support the patient for great periods of time.

Shape of the knee: The shape is important because different patients have bones that are calcified at different rates. Also, patients have bone sizes that are different from one another. Thus, the measure matters and the shaping of the artificial implant is important because it serves to offer the patient maximum motion.

Load Transfer: Load transfer is especially important in the knees, because they are highly important in accelerating the person’s movement, thus, there is constant shift of balance on the knees. The spring motion of the knees must have an equalized load transfer. Load transfer also determines how well the patient will be able to do activities such as kneel down, sit, squat, walk, and other vital functions.

Patient Bone quality: The patient bone quality is quite important when considering knee arthroscopy. The patients bones at times can be quite weak. Thus, the joints would not aid the bones at all, but instead make them weaker, so it is important to consider whether there will be a better outcome for the patient through the implants, or whether, there are serious confines to the knee that will lead to harsh results from the procedures taken to put the implants in.

Motion: Motion of the original knee joint should be looked at, but it does not really play into size-up. The new artificial limbs should be able to provide more function than the original joints because the artificial limbs are reinforced and they have the ability to support more than the original joints. The motion of the artificial joints should however match that of the original joints in terms of displacement of the knee during walking and other activities that way there is no problem in such activities in the patient’s future.

Hip Implant mechanics 2

This is a list of other factors that play into mechanics of the patients hip implant

Patient bone quality: Patient bone quality is important because the hip implant is a relatively new part of the body. If the hip implant is able to sustain weight and pressure, there might be a problem with how much the bony mass and muscle of other parts can handle. Often, in geriatric patients, the bony mass may be affected by osteoporosis which is a condition in which there are porous portions of bones that increase risk of breakage. The main bone to look at for quality is the socket of the hip because if it cannot handle the movement of the hip implant, then there is a good chance that it can break or cause immense pain.

Fixation: Fixation has to do with the surgical procedure that involves placement of the hip joint and its alignment with the socket and femur. Fixation is also critical because when the patient is in a neutral position, the hip implant or joint should be aligned in such a way, that there the max pressure should be placed on the hip that specific point. That point is where the body is straightened out. The body should be flush with a flat surface at that point. When the lower extremities are moved, then the hip should release from its neutral position and have less pressure on it. The surgical director must be able to place the hip implant so that it matches such consistencies that the original hip had.

Motion: motion of the original hip implant is important because it mainly involves centripetal force and acceleration. When we lift our leg up, the hip joint spins in a circular motion. When we try to stretch our leg at our side, the hip does not spin, but rather, it lifts like the motion that an oil piston makes. The motion of the implant should be able to match the positions that the original hip made when in different positions.

Hip Implant Mechanics 1

Patient weight: The patient weight is especially important. The hip sustains a certain amount of weight due to the fact that it is part of the lower body, so there is pressure placed against the hip joint. This pressure can often lead to pain in the hip joint upon sitting down or other actions involving purely hip movement. Patient weight should be measured so that the implant can sustain the weight and bear it under body movements.

 Shape: The shape of the hip is similar in patients but not the same. Calcification and other processes can often cause the socket of the hip area to change and alter. Osteoporosis can also have caused the area to weaken, which means that The Hip implant must be shaped accordingly to the patients hip shape. This is critical because there should be less chance of a dislocation or inability to fit the hip implant into the patient’s hip. The shape also affects the motion of the patients hip and that practically initiates movement to the rest of the lower extremities, so shape should be one of the first things to look at when measuring a patient for hip replacement surgery.

Load Transfer: Load transfer goes along the lines of weight, but it also involves the shift of weight from one hip to the other. The load, which we can identify as the body weight of the upper portions of the body (the heaviest parts) obviously shifts from one hip to the other when the patient walks, so there must be an equal load transfer between the hips, which means that THe the hip implant must be able to establish that equal range of transfer.