The two most common joints replaced with artificial ones are the knees and hips—a prosthesis, from the Ancient Greek – prosthesis, meaning addition or attachment. There are also lower and upper limb prosthetics, typically needed as the result of amputation or trauma to the limb. Prosthetics are not a 20th-century invention or even the 18th century. The apparatus dates back to circa 3,000 BC in the Near East. A Roman General, Marcus Sergius, had an iron hand prosthetic after losing his right hand in battle in the first century AD.
We will focus on the longevity of hip and knee replacements due to the number of surgeries done annually. There are approximately 400,000 total hip (THR) and 700,000 total knee replacements (TKR) each year in the U.S. The American Academy of Orthopaedic Surgeons (AAOS) predicts that the THR will increase by 171% by 2030; the TKR will grow by 189%. According to the AAOS, the escalation in these two joint replacements will continue for many decades as the number of older adults in America rises. The unrelenting growth in orthopedic surgeries could create a shortage of surgeons due to the volume of candidates.
Several factors affect the durability of the artificial joint. The recipient’s age, weight, physical condition, and motivation to exercise, and adhere to therapy. For example, a patient who has osteoporosis, weak bones, may have a shorter life of the joint than someone whose bones have more mass and less brittle. One’s physical activity benefits the recovery, but intense sports, such as tennis, skiing, and running, could be detrimental. Extreme activities could cause a degree of friction in the artificial socket, causing accelerated wear.
The good news is that a THP replacement can last 30 to 40 years. For some individuals, the joint may outlast them as the average of a THP is 64 and 65 for knees. However, many candidates are middle-aged or younger who require hip replacement and want to maintain an active lifestyle. A company, Conformis, is a pioneer in joint replacement with one of its products being the Conformis Hip System. 3D imaging and state-of-the-art manufacturing allow the patient to receive a customized joint, thus ensuring a perfect fit for the person’s specific anatomy. For a long-lasting joint, Cobalt Chrome Molybdenum Alloy is used in the manufacture of the femoral component and titanium for the hip cup.
Conformis uses the same materials for the femoral and tibial components of the knee implants. Its innovative custom-designed knee replacement results in a shorter hospital stay and quicker recovery. Younger adults resume strenuous sports, such as spin classes, and one patient, per Conformis, was playing golf six weeks post-surgery. Another patient attested to being home from the hospital after his knee implant in two days. The company’s personalized implants receive the praise of orthopedic surgeons across the United States.
Often, it is not the artificial joint that reaches the end of its usefulness, but the conditions of the person that cause the need for a second operation. Individuals with chronic pulmonary disease, diabetes, liver disease, and a high body mass index (BMI) contribute to the possibility of further surgery – frequently due to infection. Deep infection is rare, as studies show this occurs in only about 1% of knee replacements. Maintaining a healthy body weight has a significant bearing on longevity, although an overweight person may be sedentary. Lack of physical activity puts less stress on the new joint, which, paradoxically, helps it last longer.
One long term study reported that 90% of patients had fully functioning knee implants after twenty years. As stated above, the materials comprising the implant, plus the expertise of the specialist that can also affect durability.
This part of the anatomy has fewer replacements than the hip and knees. There are about 53,000 shoulder implants performed annually in the U.S. The two common reasons are a severe fracture, osteoarthritis, and avascular necrosis (loss of blood to the bone). The operation may involve the replacement of the ball and the socket or just the placement of a plastic surface on the socket.
Longevity for a complete shoulder replacement is 15 to 20 years; it’s a rarity to need revision surgery on the same joint. The timeframe could be less in a partial implant when the orthopedic surgeon places a metallic head on the surface of the humeral (upper arm) bone. If the joint socket or glenoid begins to wear, this could shorten the need for a second operation.
The advancements in surgical techniques and ingenious implants have made joint replacements attractive for patients in debilitating pain. The operations have become routine for specialists in this field of orthopedics. More importantly, the procedures have restored the joy of movement to adults, young and elderly.
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