Arthroplasty is a broad term referring to any artificial joint replacement surgery. The etymology comes from two greek words – “arthro” meaning joint, and “plasty” which refers to the process of forming or molding. Specialists in the field of arthroplasty consider themselves experts in surgical joint reconstruction or joint replacement.
Joint arthroplasty most commonly refers to hip replacement surgery or knee replacement surgery. A variety of types of replacements exist, including total (both sides), hemi (only one side), and uni-compartmental (only partial). Hip and knee replacements are usually performed for arthritis in patients over 50 years old with severe pain preventing walking more than 60 meters. However, it is estimated that over half of all hip replacements are done in under 65-year-olds when there may be other causes such as trauma involved.
Joint replacement therapy is one of the most advanced and successful surgeries performed in today’s medical industry. However, because joint replacements can sound scary to some people, more often than not they’re called arthroplasties instead – which really just means “to replace with an artificial part”.
Currently, there are over 100 different types of implants, and as technology advances their popularity will grow. But right now the most commonly used replacement parts in the United States (U.S.) are hip and knee replacements; about 700,000 total per year combined. The current technology trend is towards implanting joint replacements with robotic technology.
Replacement is recommended once the pain becomes more severe and occurs at rest. Arthroplasty is not a cure but can provide relief of symptoms. Joint replacements are successful in relieving pain for 90 percent of patients, restoring range of motion to near normal, and decreasing disability more than any other treatment of arthritis. A new artificial joint usually lasts 20 years or longer if given proper care by the patient. However, some studies suggest that people who want an artificial joint should wait until they will be less active due to high failure rates in athletes and young adults who keep their joints very busy with exercise regimes. Replacement hips also wear down over time so revision surgery may be needed as much as 10-20% of the time after 15 years.
There are three primary reasons why a patient would need to have replacement surgery: 1) arthritis 2) severe trauma or 3) congenital defects that impact their ability to function normally. Congenital defects don’t necessarily mean birth defects – they can come from age as well. And traumatic events are anything that could damage the joint enough to cause severe pain and/or decrease mobility, so things like sports injuries or car accidents fall into this category.
There are different types of replacement surgeries for each joint, including partial and total. A partial replacement is when only part of the joint is replaced – usually the area that has caused the pain or extreme impairment in motion. Total replacements are when everything from one end to another is done.
Total Knee Replacement (TKR) or Total Knee Arthroplasty (TKA)
The most common type of surgery on the knee is the total replacement which consists of replacing all surfaces except for a section of bone attached to it called an “epicondyle”. The surgeon removes worn-down ends of the thigh bone and shinbone and resurfaces them with metal and plastic.
Partial Knee Replacement (PKR), Partial Knee Arthroplasty (PKA), or Unicompartmental Knee Arthroplasty (UKA)
Another form of arthroplasty surgery is partial knee replacement. A knee replacement is more like a resurfacing than a true “replacement” surgery. Instead of cutting away bone, we are only shaving away the worn-down ends to resurface the knee joint. It resurfaces only part of the surfaces of the knee, usually those that are causing pain, leaving the rest of the anatomy alone. Partial knee replacements (or unicompartmental knee arthroplasties) essentially leave the remaining anatomy alone, potentially allowing for a more naturally feeling knee.
Total Hip Replacement (THR) or Total Hip Arthroplasty (THA)
In hip replacement surgery, the socket of the joint is resurfaced with metal and plastic components while the head and neck of the femur are replaced with metal and ceramic. The surgeon makes an incision over the front or side of your thigh, removing a section of bone from your pelvic area where your hip attaches to give him access to the hip joint. He then replaces the femoral head with a metal or ceramic ball attached to a stem that inserts into the femur. Next, he uses what’s called a reamer to make space for the new ball in the pelvis. He finishes it off with a plastic or metal socket that is attached to the stem, then press-fit into place.
Hip Resurfacing Surgery
Hip resurfacing was initially thought to be a promising form of hip replacement. It’s ideal for younger patients since it preserves more bone and tissue. The surgeon uses the pelvic surface as a natural base and just “resurfaces” the worn-out ends of the femoral head and neck with metal to create a new, smooth surface that allows for an easier glide within the socket. Research studies have shown that patients had early failures from metal ion and corrosion problems. Most orthopedic surgeons will not perform this type of surgery out of fear of complications.
Partial Hip Replacement (Hip Hemiarthroplasty)
In a partial hip replacement procedure, surgeons typically only remove the damaged part of the femoral head and neck. Typically this surgery is only performed for elderly patients who have hip fractures. The concern for this implant is that higher demand patients may wear out the cartilage in the pelvis and lead to a painful hip replacement
The most common replacement surgery on other joints includes shoulder replacement, wrist replacement, and ankle replacement.