The musculo-skeletal system provides shape and support, protects internal organs, allows for movement, stores important minerals (calcium), and produces red blood cells. Overall, the system serves as our body's structure.
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It is this system that allows us to stand up, sit down, and move around. The skeletal system contains 206 bones and each bone and muscle has a different functions. Often the size, shape, and location of the bone determine its use. For example, the ribs and scull protect important organs like the heart, lungs, and brain. Bones in the hand, on the other hand, are small and capable of holding things and making small movements. While bones in the leg, hip, and back support the weight of the entire body.
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And with the help of the muscular system the bones provide movement. The site of movement is called a joint.
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Joints allow bones to connect to each other and there are several main types: ball and socket, hinge, pivot, gliding, and immovable joints. The ball and socket joint allows for a free range of movement and can be found in the shoulder and hip. Hinge joins provide a 180-degree of motion and form the elbow and knee. The pivot joint provides rotation and is found in the neck. Gliding joints in the vertebrae allow for small movements. And finally immovable joints, found in the skill, do not allow for any movement. When a part of the skeletal system is compromised, such as the legs, technology can even be used to help repair the support system.
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Repair and Regeneration of Bones and Muscles
Biomedical engineers apply engineering techniques using their understanding of body systems to develop technologies and devices to meet the needs of humans.
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One field of biomedical engineering is prosthetics, or artificial body parts. When an entire leg, arm, or hip needs to be replaced doctors often look to prosthetics.
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A prosthetic can either replace an entire or part of a missing/damaged body part. Prosthetics are designed to look as much as possible like the original body part and must be made with the characteristics of strength, durability, longevity, and comfort, in mind (See Figure 2).
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Common prosthetic procedures include surgery of the joints, at the knees, and hips.
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Several different materials are currently used for prosthetics such as willow wood, laminated fibers, plastics, metallic alloys and carbon-fiber composites.
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Ceramic, while strong, is very brittle making it a problem. The main concern with new materials is a lack of knowledge of how long they will last inside the body.
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Currently knee and hip prosthetics last anywhere from 10 to 15 years.
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This number is not favorable for young patients, and researchers are looking to add things to prosthetics to help promote bone growth.
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In addition to the material, biomedical engineers also focus on the sensors, joints, and connections that the prosthesis has to the body.
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While it is easy to harness the shoulder or upper these sites of attachment do not offer the widest range of movement for the patient. New technology is being developed to use small sensors, implanted in the body, that detect minute electoral changes in nearby muscles and nerves.
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This data is then transmitted to the prosthesis and movement is produced. This new wave of sensors is more lifelike and one artificial knee recently designed to adjust to a person's walking based on the speed and surface they are on.
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The body has a natural tendency to heal itself, but tissue engineering goes beyond that. We cannot replace organs yet, but biomaterials are being used to provide structural scaffolding future endeavors that may yield even more promising results. Skeletal muscle tissue engineering could help reconstruct muscle loss caused by trauma, disease, or tumors. Since there are so many issues with donor tissue being rejected when grafting, tissue engineering could tackle a problem from a new angle. Engineered tissue is new, functional muscle tissue derived form stem cells. Currently research is going on to simulate muscle myoblast cells using stem cells, use scaffolds to build muscle tissue, and also vascularizing tissue in vitro.
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Commonly Used Knee Prosthetics Overview
Cruciate-Retaining Mobile or Fixed Bearing Knee
The cruciate-retaining mobile or fixed bearing knee is a total knee replacement system. This type of prosthetic is used for patients how have a fully function Posterior Cruciate Ligament (PCL), as it is left intact during surgery. The Anterior Cruciate Ligament (ACL) is no longer functional after surgery and the prosthetic takes over for the movement of this ligament.
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Cruciate-Substituting Mobile or Fixed Bearing Knee
During this total knee replacement surgery both the ACL and PCL are lost and the prosthetic compensates for their loss. This surgery is often used for patients that have damage or a lack of function in their PCL already.
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Hinged Knee
The hinged knee is used in a patient that has already had a total knee replacement prosthetic and is in need of further repair. This surgery is therefore only used in old prosthetic patients, but longer stems of the components are used to hold the new prosthetic parts in place.
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Knee Fusion
In a knee fusion surgery the ends of the femur and tibia bones are cut off, ligaments and the menisci are removed, and the two bones are fused together. The benefit to this is a secure and pain-less joint. But the leg is often several inches shorter than before. This procedure is often performed on patients who suffer from joint infection or bone tumors. Sometimes this fusion can eventually be replaced with a bendable knee later, which allows the patient to experience some movement in the knee again.
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images/2014/4/14.04.10.02.jpg
Figure 2. Model of a total knee replacement prosthetic.
Uni-Compartmental Knee
This type of prosthetic is also referred to as a partial knee replacement because only one
compartment of the knee is replaced. One of three joints is replaced: the inner joint (medial), outer joint (lateral), or joint under the kneecap. This surgery is used for patients who suffer from osteoarthritis that is found in one part of the knee. Since other joints are capable of being weight only one joint needs to be replaced.
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