TOTAL KNEE ARTHROPLASTY

Over the years, knee joints degenerate and get damaged making it difficult to perform simple daily activities, such as walking or climbing stairs. This condition is described as knee osteoarthritis. Sometimes degeneration is so severe that the patient reports pain even when sitting or lying down.

Conservative treatment, such as analgesics or a walking cane, is often insufficient, and then the patient should consider joint replacement surgery known as total knee arthroplasty. Total knee arthroplasty is today a safe and effective procedure that relieves pain and allows the patient to return to daily activities.

The first knee arthroplasty took place in 1968 and since then the continuous improvement in materials and surgical techniques have greatly increased its success rates. In general, total knee arthroplasty is one of the most successful surgical interventions in medicine. It is worth-mentioning that more than 600,000 surgeries are performed each year in the United States.

ANATOMY

The knee is the largest and strongest joint in the human body. It consists of the lower end of the femur (thigh), the upper end of the tibia and the patella. Bone surfaces that come in contact with each other are covered with articular cartilage, a smooth, slippery layer that protects the bones from damage while allowing painless movement during bending and stretching.

The meniscus, two wedge-shaped cartilages, acts as a “shock absorber” between the femur and the tibia. Their elastic properties smoothen and provide extra stability to the joint.

Finally, the knee joint is surrounded by a thin film, the synovial bursa that produces the synovial fluid that nourishes and lubricates the articular surfaces by reducing frictional forces.

 

ETIOLOGY

The most common cause of chronic knee pain and disability are “arthritic lesions”. Although there are many types of arthritis, the most common are: Osteoarthritis, Rheumatoid Arthritis and Post-Traumatic Arthritis.

Osteoarthritis: Osteoarthritis is the most common form of knee arthritis. It is a degenerative type of disease that occurs mainly in people over 50 years of age.

In osteoarthritis, the cartilage of the knee surfaces is gradually degenerated. As the cartilage is degraded, the bones begin to come into contact with each other. The procedure is accompanied by hardening of the bony surfaces beneath the cartilage, development of new bone and cartilage at the edges of the joint (osteophytes) as well as synovial fibrosis. It may be presented with asymmetric distribution and is often located in a single articular compartment. Moreover, in addition to wear, due to friction forces, it is also often associated with weight over-loading. Often, there are no other systemic manifestations, but – locally – signs of inflammation may occur.

Rheumatoid Arthritis: Rheumatoid arthritis is a chronic inflammatory disease that simultaneously affects many joints in the human body including the knee. It is manifested as symmetrical polyarthritis, which means it affects the same joint bilaterally.

In rheumatoid arthritis, the synovial membrane is inflamed, swollen and gradually knee pain and stiffness are presented. It is an autoimmune disorder. This means that the immune system, through the inflammatory response it causes, destroys normal tissues (cartilage, ligaments and bone surfaces).

Post-traumatic arthritis: This type of arthritis is developed after a knee injury. For example, a fracture involving the joint (intra-articular fracture) can cause irreparable damage to the cartilage covering the knee articular surfaces, and consequently lead to chronic arthritic lesions. In addition, meniscus ruptures and ligament injuries (e.g. anterior cruciate ligament rupture) can cause instability and further damage to the knee joint, which over time leads to arthritic lesions.

DESCRIPTION

Knee replacement surgery (also known as knee arthroplasty) could be more accurately called “replacement of articular surfaces” as actually only the bone surface is replaced. There are 4 basic steps to a knee arthroplasty surgery.

  1. Preparation of bone surfaces. Degenerated surfaces of the articular cartilage at the ends of the femur and tibia are removed along with a part of the underlying spongy bone.
  2. Placement of metal implants. The surfaces from which the cartilage has been removed are replaced with special metal implants that restore the articular surfaces of the knee and can be stabilized either by the use of special resin or “cement” or by the “press-fit” method, that is, by the creation of new bone.
  3. Patella replacement. The articular surface of the patella is removed and replaced with a special plastic implant (polyethylene). This is a step that is often skipped by the surgeon as appropriate.
  4. Placement of polyethylene insert. A special durable plastic material (polyethylene) is placed between the metal prostheses to create a smooth sliding surface.

IS TOTAL KNEE ARTHROPLASTY INDICATED FOR THE PATIENT?

The decision to undergo surgery is made by the patient and his or her family in cooperation with the Orthopedist. However, every decision is preceded by a thorough examination and evaluation to determine the benefits and risks of this process.

 

Total arthroplasty surgery is recommended when:

  • The patient experiences severe joint pain and stiffness that restricts daily activities, such as walking. It should be considered when pain is triggered after walking a few blocks and it is necessary to use a walking cane.
  • Moderate or severe pain during rest, day or night.
  • Chronic knee inflammation with edema and redness that is not improved by rest and anti-inflammatory drugs.
  • Joint deformity and stiffness.
  • Failure to improve with treatments such as anti-inflammatory drugs, cortisone injections, hyaluronic acid injections and physiotherapy.

CANDIDATES FOR SURGERY

There are no absolute restrictions on the patient’s weight and age. The indications for the surgery are based on the degree of pain and disability of the patient, not age. Most patients undergoing total knee arthroplasty are between 50 and 80 years of age, but it is the orthopedist the one who evaluates the patient and proceeds accordingly.

Nowadays, knee arthroplasty has high success rates, whether it is performed on teenagers with rare forms of arthritis or elderly patients with degenerative osteoarthritis.

 

DECISION ON SURGICAL INTERVENTION

REALISTIC EXPECTATIONS

An important factor in a patient’s final decision is to realize what to expect from surgery.

More than 90% of people who have undergone total knee arthroplasty experience a dramatic reduction in pain and a significant improvement in their daily activities. However, it should be noted that surgery will not allow the patient to do more than what he or she could do before the development of arthritic lesions.

With regular use and normal activity, arthroplasty plastic parts (polyethylene) begin to wear out. Excessive activity or weight can accelerate this normal wear and cause pain and loosening. As such, the Orthopedist recommends avoiding demanding activities such as running, jumping or team contact sports.

Realistically, hiking, golf, swimming, riding, cycling and dancing can be the daily activities for a patient that has undergone total knee arthroplasty.

 

POSSIBLE POST-OPERATIVE COMPLICATIONS

The rate of complications after total knee arthroplasty is low. Severe complications, such as infection, occur in less than 2% of patients. Other major complications such as heart attack or stroke occur at insignificant rates. Although rare, when these complications occur, they can prolong or limit complete recovery.

 

INFECTION

The infection either relates to the trauma or materials of the prosthesis and can occur peri-operatively during hospitalization or at home after discharge, even years after surgery. Local infections are treated with antibiotics. On the contrary, infections related to the materials of the prosthesis may require removal of the prosthesis and replacement with another at a subsequent time.

 

THROMBOSIS

Thrombosis is one of the most common complications in Orthopedics. If these clots are released and are transferred to the lungs through bloodstream, they can cause pulmonary embolism, a pathological condition which is potentially life-threatening. The orthopedist recommends some preventive measures that include periodic lower extremity lifting, use of graded compression stockings and anticoagulant agents, which are able to reduce the risk.

 

PROBLEMS RELATED TO THE PROSTHESIS

Despite advances in medicine and technology, prostheses inevitably wear out and get loose. In addition, although bending-extension movements of at least 130° are expected after surgery, scar tissue formation and reduced compliance of the patient to the physiotherapy protocol may significantly limit the range of motion of the joint.

 

CONTINUOUS AND PERSISTENT PAIN

A small number of patients continue to experience pain after surgery. This is a rare complication as the vast majority of patients report immediate pain relief.

 

NEUROVASCULAR DAMAGE

Although rare, it is also described after total knee arthroplasty.

 

PREPARATION FOR SURGERY

Preoperative evaluation: A thorough examination is planned before surgery, which includes clinical examination, blood tests and appropriate (e.g. patients with cardiovascular disease) preoperative evaluation by specialists, such as a cardiologist. During the evaluation it is advisable to report in detail the patient’s medication and to inform the Orthopedist of any possible dental or urological problems, as any infection can lead to a prosthesis infection.

Practical home changes: Several home modifications can make patient recovery easier:

  • Shower or bath bar
  • Secure railings on the stairs
  • Toilet seat lift
  • Removal of carpets or cables

 

SURGERY

The patient is often admitted to the hospital the day before surgery.

 

ANESTHESIA

After admission, the patient is evaluated by a member of the anesthesiologists’ team. The most common types of anesthesia are general anesthesia (the patient is asleep), dorsal and epidural anesthesia, or regional anesthesia (nerve blocking). The anesthesiologist takes into account the patient’s medical history and determines the type of anesthesia that is best for the patient.

 

SURGICAL PROCEDURE

The procedure lasts about 1 hour. As mentioned above, the surgeon removes the damaged cartilage and bone and then inserts new metal and plastic implants to restore knee alignment and function.

HOSPITALIZATION

The patient is hospitalized for 3 days.

 

PAIN CONTROL

After surgery, the patient receives powerful painkillers to help manage pain and speed up the process of postoperative recovery.

 

THROMBOSIS PREVENTION

As mentioned above, the Orthopedist recommends some preventive measures that include periodic lower extremity lifting, use of graded compression stockings and anticoagulant therapy that are able to reduce the risk of thrombosis.

 

PHYSIOTHERAPY

Most patients begin to exercise the next day after surgery. In some cases, kinesiotherapy begins on the same day. The physiotherapist will teach the patient specific exercises to strengthen and restore the range of motion of the joint. Occasionally, continuous passive motion (CPM) devices are used which, according to some studies, reduce edema and improve blood circulation by motivating the leg muscles.

 

RECOVERY AT HOME

The success of the surgery will largely depend on the patient’s compliance with the orthopedist’s recovery plan recommended during the first few weeks.

 

SURGICAL TRAUMA HEALING

The patient treats the trauma at home, and the sutures are removed 2 weeks after surgery. Internal stitches are absorbable and do not need to be removed.

It is advisable to avoid moisture around the surgical trauma and to cover it to prevent clothing irritation.

 

DIET

Minor loss of appetite is common in the first few days after surgery. However, a balanced diet with iron supplements is important for nourishing and healing the wound.

 

PHYSICAL ACTIVITY

The patient’s activity plan should include:

  • Patients start charging the limb immediately on the 1st postoperative day
  • Other common indoor activities.
  • Special exercises several times a day alone or with the help of a physiotherapist.

Finally, the patient will be able to drive again when the knee can be flexed adequately to sit comfortably in the car and when control of muscles provides sufficient reaction time for braking or accelerating. Most patients resume driving 4 to 6 weeks post-operatively.

 

RESULTS

Improving knee motion is one of the goals of total knee arthroplasty and complete movement recovery is now a given. Most patients can stretch the knee and bend it enough to climb stairs or get into the car within the first 5 days after surgery.

In addition, many patients experience some numbness in the skin around the incision and some degree of stiffness. Finally, some patients may hear or feel “clicks” created by the metal implants and plastic inserts while bending or walking. They are normal sounds that decrease with time and are well-tolerated by the patient.

Knee prostheses can activate metal detectors at airports or public buildings. It is advisable to inform security personnel.

 

LIFE EXTENSION OF KNEE PROSTHESIS

Currently, more than 90% of modern total knee arthroplasty prostheses are still in operation 25 years after surgery. By following the instructions of the Orthopedist and preserving the prosthesis through a normal lifestyle – without exaggerations – the patient contributes to the eventual success of the operation.