Total Joint Replacement
Most joint replacement operations involve a total joint replacement, which means that both sides (compartments) of the joint are replaced.
If arthritis affects only one side of your knee – usually the inner side – it may be possible to have a half-knee or unicompartmental replacement (sometimes called hemiarthroplasty or partial joint replacement). The unicompartmental operation is only suitable for about one in four people with knee osteoarthritis. This is a less extensive operation than a TKR and it should therefore mean a quicker recovery.
It is possible to replace just the kneecap (patella) and its groove (trochlea) if this is the only part of your knee affected by arthritis. This is also called a patellofemoral replacement or patellofemoral joint arthroplasty. Again this is a less major operation with speedier recovery times. The operation is only really suitable for about 1 in 10 people with knee osteoarthritis.
Who should have their joint replaced?
To be a candidate for joint replacement you should have radiographic evidence of joint damage, moderate to severe persistent pain that is not adequately relieved by extended course of non-surgical management, and clinically significant function limitation resulting in diminished quality of life.
Joint replacement surgery dramatically relieves pain in people with severe osteoarthritis of the hip or knee, and this benefit appears to last for up to 30 years. However, it may take up to 1 year before the benefits of joint replacement surgery become fully apparent. Joint replacement is an elective procedure, and the risks and outcomes vary. Therefore, it is essential that you be informed of the goals and expectations should be considered before surgery to determine whether these goals are attainable and the expectations realistic. Any discrepancies between your expectations and the likely surgical outcome should be discussed in detail with the orthopaedic surgeon before surgery.
With proper patient selection, good to excellent results can be expected in 95 per cent of patients, and the survival rate of the implant is expected to be 95 per cent at 15 years. When overall health improvement is used to assess the cost-effectiveness of total joint arthroplasty, the hip and knee arthroplasty have similar results. Costs associated with long-term medication, assistive care and decreased work productivity may exceed the cost of arthroplasty.
It should be noted that joint replacement is more cost-effective among patients who had the most to gain (those with lower preoperative function). However, if left until functional status has declined, the postoperative functional status does not improve to the level achieved by those with higher preoperative function. Please don’t defer the surgery until your function is too impaired; for example, if you are wheelchair- or bed-bound for a long time before the surgery your postoperative recovery will be very difficult and prolonged.
Other Surgical Options
Arthroscopy, or ‘scoping’ a joint, is a day surgery procedure that is used to examine and sometimes repair joints. For arthroscopy, the doctor inserts a viewing tube (an arthroscope) through a small cut (about 5mm) into the fluid-filled space in the affected joint. The technique can be used to help with diagnosis or to carry out treatment or keyhole surgery using miniaturised instruments.
In arthroscopic debridement the surgeon clears away the debris and smooths damaged cartilage in the knee. For a small subgroup of knees with loose bodies or flaps of meniscus (disc cartilage in the knee) or cartilage that are causing mechanical symptoms, such as locking, or catching of the joint, arthroscopic removal of these unstable tissues may improve joint function and alleviate some of these mechanical symptoms. Although his surgery may provide temporary relief of symptoms, it does not stop the progression of arthritis. Thus a selected group of patients with osteoarthritis may benefit from arthroscopy. However, if there is already a lot of osteoarthritis, it may be better to do another type of surgery rather than arthroscopy.
Arthroscopic debridement (clearing away debris and smoothing the cartilage in the knee) is still commonly performed in people with knee osteoarthritis but is used less frequently nowadays as evidence of its lack of benefit accrues.
Osteotomy / Alignment
Surgery may be used to realign bones and other joint structures that have become misaligned because of long-standing osteoarthritis. For the knee, such realignment may shift weight-bearing to healthier cartilage where the joint has been unevenly damaged by the osteoarthritis, with pain relief. The procedure is done to relieve stress on the cartilage and prevent further damage to the joint. During an osteotomy, the surgeon removes a small wedge of bone near the affected joint. Removing the piece of bone realigns the bone and improves the contact between the remaining, healthy areas of cartilage in the joint. The tibial osteotomy for the knee may be recommended for a younger, active patient instead of joint replacement surgery.
Arthrodesis / Fusion
A surgical procedure called arthodesis, or joint fusion, is sometimes used to correct severe joint problems caused by osteoarthritis. In this procedure, the surgeon makes the affected joint permanently immobile by using a bone graft and inserting metal screw, plates, and rods to hold the joint in place. Arthrodesis is performed only when the pain from osteoarthritis is so severe that immobilising the joint is an improvement. This may be recommended for badly damaged joints for which joint replacement surgery is not an option. Fusion may be recommended for joints of the wrist and ankle and the small joints of the fingers and toes but is rarely recommended for knees or hips. Joint immobility in large joints such as the knee and hip leads to marked impairments in function and should be avoided unless this procedure is absolutely necessary.
Cartilage Grafting / Transplantation
Unlike bone, cartilage that is injured does not rejuvenate. Surgery may be used to graft new cartilage cells into damaged regions of cartilage. The benefits of cartilage grafting in arthritis joints is still being studied. Cartilage grafting is likely to be most practical when the cartilage damage is confined to a very small area surrounded by normal cartilage. Current techniques are not helpful for people with large areas of thin or absent cartilage, as is typically the case in osteoarthritis.
Cartilage transplantation used live cells from donated cartilage. This process is known as autologous chondrocyte therapy (ACT) or autologous chondrocyte implantation (ACI). Another technique, called mosaicplasty, involves moving cartilage and some bone from another part of the knee to repair the damaged surface. Graft procedures combining these two techniques may be used to cover large areas of joint damage. The donated cartilage must be transplanted within 72 hours.
Other Surgical Options
There are several other techniques that are occasionally offered to people with arthritis. One such procedure is microfracture. This operation, which is performed by keyhole surgery, entails making holes in the bone surfaces with a drill or pick to encourage new cartilage to grow. The benefits are not well proven and the results are not as good as knee replacement for advanced arthritis.
Please recognise that surgery is not the first line of treatment for OA and should generally only be recommended once other more conservative modes of treatment have been tried and not helped.