What is Knee Replacement? Procedure, Types and Surgery

If your knee is severely damaged by arthritis or injury, it may be hard for you to perform simple activities, such as walking or climbing stairs. You may even begin to feel pain while you are sitting or lying down. If nonsurgical treatments like medications and using walking supports are no longer helpful, you may want to consider total knee replacement surgery. Knee replacement surgery is a safe and effective procedure to relieve pain, correct leg deformity, and help you resume normal activities.

Knee replacement surgery was first performed in 1968. Since then, improvements in surgical materials and techniques have greatly increased its effectiveness. Total knee replacements are one of the most successful procedures in all of the medicine.

KNEE JOINT :

The knee is the largest joint in the body, and having healthy knees is required to perform most of the everyday activities.  The knee is made up of the lower end of the thighbone (femur), the upper end of the shinbone (tibia), and the kneecap (patella). The ends of these three bones where they touch are covered with articular cartilage, a smooth substance that protects the bones and enables them to move easily.

The menisci are located between the femur and tibia. These C-shaped wedges act as "shock absorbers" that cushion the joint. 

Large ligaments hold the femur and tibia together and provide stability.

The long thigh muscles give the knee strength.

All remaining surfaces of the knee are covered by a thin lining called the synovial membrane. This membrane releases a fluid that lubricates the cartilage, reducing friction to nearly zero in a healthy knee.

Normally, all of these components work in harmony.  But disease or injury can disrupt this harmony, resulting in pain, muscle weakness, and reduced function.

KNEE REPLACEMENT:

A knee replacement (also called knee arthroplasty) might be more accurately termed a knee "resurfacing" because only the surface of the bones are actually replaced.  Metal and plastic parts are used to cap the ends of the bones that form the knee joint, along with the kneecap.

Knee Replacement Procedure: 

The steps are:

  1. Preparing the bone - The damaged cartilage surfaces at the ends of the femur and tibia are removed along with a small amount of underlying bone.
  2. Positioning the metal implants - The removed cartilage and bone is replaced with metal components that recreate the surface of the joint.  These metal parts may be cemented or uncemented ("press-fit") into the bone.
  3. Resurfacing the patella - The undersurface of the patella (kneecap) is cut and resurfaced with a plastic button.  Some surgeons do not resurface the patella, depending upon the case.
  4. Inserting a spacer - A medical-grade plastic spacer is inserted between the metal components to create a smooth gliding surface.

Candidate for a Knee Replacement: 

People who need knee replacement surgery usually have problems walking, climbing stairs, and getting in and out of chairs.  They also suffer pain at rest.

Surgery Recommendation:  For a patient who has:

  1. Pain, stiffness, and swelling and who needs a cane or a walker for support.
  2. Poor quality of life due to pain that is present at rest and not relieved by medications. 
  3. Bone damage revealed by x-rays.
  4. Non-surgical treatment failure:  Failure to substantially improve with other treatments such as anti-inflammatory medications, cortisone injections, lubricating injections, physical therapy, or other surgeries.
  5. Deformity, as a bowing in or out of the knee.

Surgery Consideration:  For patients who have:   

  1. Osteoarthritis:  Arthritis, usually due to ageing.
  2. Rheumatoid arthritis:  Arthritis, due to chronic inflammation (autoimmune disease). 
  3. Post-traumatic arthritis:  Arthritis, following trauma.

Types of Knee Replacement:

Traditional Total Knee Replacement:

When nonsurgical treatments fail, total knee replacement surgery is suggested.  In total knee replacement, damaged bone and cartilage are removed and replaced with metal components that recreate the surface of the joint.  A total knee replacement implant made of metal alloys, ceramic material, or strong plastic parts is used and provides for:

  1. The lower end of the femur.
  2. The top surface of the tibia.
  3. The back surface of the patella.

Custom Fit Total Knee Replacement (Patient Specific Instrumentation-PSI):

A three dimensional bone model of the patient's knee is created based on the CT/MRI images.  Taken into account are the overall alignment, femoral and tibial bone cuts, and the size of the implant needed.  The images are sent on-line to the engineer based in the US through software, who uses the data to design and build customized surgical instruments that accommodate the unique shapes and angles of the particular patient’s joint for a precise aligned implant.  These cutting blocks are shipped to the surgeon in four weeks. 

Advantages of CFKR technique over the traditional surgery are that it:

  1. Provides a natural alignment.
  2. Alienates the multiple steps of traditional surgery.
  3. Shortens the surgery time.
  4. Minimizes blood loss.
  5. Lowers the risk of infection.
  6. Reduces the length of surgical incision.
  7. Leads to precise implant fitting.
  8. Provides better functional outcomes.

MIS Knee Replacement Surgery:

Minimally invasive knee replacement surgery (MIS-TKR) is a new method of performing a knee replacement using an incision that is half the length of the standard total knee incision. The use of this technique minimizes muscle cutting thereby reducing the post-operative pain, allowing earlier rehabilitation, and reducing the duration of the hospital stay, exceptions being patients with large legs and bulky muscles due to obesity.

COMPLICATIONS:

For knee replacement surgery, the complications are low. They include:

  1. Infection [fever greater than 100 F (37.8 C); shaking chills; drainage from the surgical site; increasing redness, tenderness, swelling and pain in the knee].
  2. Blood clots in the leg vein which may travel to the lungs, heart, and brain.
  3. Nerve damage.
  4. Implant problems causing joint surgery failure.
  5. Continued pain.

POSTOP CARE:

In the hospital, pain management, blood clot prevention, physical therapy, and pneumonia prevention are addressed.  At home, wound care, diet, and activity are advised.  

Tags: Knee replacement , Surgery , Joints , knee joints , Joint Pain

 

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