Understanding Knee Replacement Surgery
Knee Replacement
Anatomy of the Knee joint
The knee joint, surrounding muscles and tissue are important structures in carrying out day to day activities. The knee joint is a complex hinge formed between the large thigh bone called the femur and the large shin bone, called the tibia, covered by the knee cap or patella.
The main muscles spanning the knee joint include the front thigh muscles or quadriceps and the back thigh muscles, the hamstrings. The knee joint is assisted by the other joints of the leg and pelvis as well as the muscles of the entire lower limb and body’s trunk or core. There are a number of mechanisms that can cause the knee joint to become damaged or weakened, ultimately leading to arthritis.
Arthritis is damage to the boney surfaces that form the joint. It causes pain, stiffness and deformity. Arthritis of the knee makes it difficult walk, get up from a chair, kneel or squat, climb stairs among other activities. As it worsens, arthritis can even cause pain at rest or at night. Arthritis can be hereditary or caused by injury or obesity, however its affects can be lessened by a healthy and active lifestyle.
Knee replacement involves removing the damaged surfaces of the knee joint and replacing them with artificial components called prostheses (Watch a Knee Replacement Video). With the aid of rehabilitation, a knee replacement can reduce pain, improve mobility, strength and function resulting in a better quality of life.
Research has shown that joint replacement is very effective at achieving these outcomes in most people. For persons who are physically and emotionally ready for Joint Replacement, there is roughly an 80% chance of being satisfied with the outcomes of surgery. For the remaining 20% there are some known and many unknown reasons for less than ideal results. Complications such as infection or blood clots do occur in less than 1% of patients and can lead to poorer surgical outcomes and prolonged recovery. Other important factors such as realistic expectations and sufficient recovery of function are also very important. It is important to understand your particular risk level for surgical complications and what you can expect after surgery along with the efforts you will undertake to restore your quality of life. Talk to your surgeon about your risk levels, expectation and rehabilitation as it will assist with your decision making for surgery.
Revision Knee Joint Replacement
A revision joint replacement is done to replace a malfunctioning previously implanted joint prosthesis. Also called revision arthroplasty, revision joint replacement is often more complicated with less predictable results than primary or a first time joint replacement.
Because of the many different reasons for which a revision joint replacement may be done, surgery decisions are made on an individual basis. Not all revision joint replacements require the replacement of all parts of the implanted joint. In some cases, parts of the original implant may still be in perfect condition while others may need to be replaced.
Reasons a revision joint replacement may be needed include worn-out implants, implants coming loose from the bone, infection of a replaced joint, and instability or misalignment of an implanted joint. Much of the information applicable to the original (or primary) joint replacement in terms of preoperative, intraoperative, and postoperative care is also true for a revision procedure. However, there are some differences of which you should be aware.
Hospital Stay
The hospital stay for a patient undergoing a revision total joint surgery may be slightly longer than for the original surgery. Hospital stays for the original (primary) total joint replacement average around three days. This compares to 5-7 days for a revision total joint replacement patient.
Blood Loss
As with the original joint replacement, revision total joint replacement is associated with some loss of blood during and immediately following the surgical procedure. The lost blood can be replaced with either: 1) blood that you have donated before the surgery or 2) blood that is donated at an authorized blood bank.
In general, we prefer that patients do not donate their own blood prior to surgery. The blood available through the blood bank is tested with sophisticated and sensitive tests to minimuze the risk of infection. You will be in better physical health if you have not donated blood prior to surgery and your overall risk of transfusion is reduced by not pre-donating blood.
Bone Graft
In revision total joint replacement, a bone graft procedure may be required. Grafting involves the reconstruction of the bone surrounding the implant with new bone. The new bone can either be taken from another location in your own body or from a donor patient.
The decision to use your own bone (called autograft) versus donor bone (called allograft) is usually based upon how much bone is needed. If only a small amount of bone is needed, bone can be obtained from either bone removed during the surgical procedure itself or bone taken from another site (such as the pelvis). For many revision total joint replacement cases, more bone is needed than can be obtained from another site from your own body. When this is the case, donor bone is used.
Similar to blood bank blood, donor bone comes from a certified tissue bank. Certification standards include screening of all donor samples for infectious agents (hepatitis, HIV, e.g.) and the assurance of proper processing so that bone grafts carry the smallest risk possible for use in patients.
Revisions for Infection
In the case of a revision due to infection, depending on the type and extent of infection, you may be told that you need to undergo a 2-stage revision. This involves two surgeries: 1) the removal of the prosthesis and the treatment of the bone to get rid of the infection, and 2) inserting a new prosthesis several weeks later after the infection has been eradicated.
Unicompartmental (UKA)
A partial knee replacement or Unicompartmental knee replacement may be done if the arthritic damage is confined to a localized part of the joint. The procedure is similar to a total knee replacement, but with only one side of the joint replaced.
Recovery time is generally shorter following this kind of surgery. If the arthritis is widespread, the ligaments of the knee are not intact or the knee has become stiff, then the partial knee replacement is NOT appropriate, and should not be considered.