Partial Knee Replacement (PKR)

Overview

Knee replacement for osteoarthritis of the knee is a frequent and successful operation. For late-stage medial compartment osteoarthritis of the knee, there are two surgical options: partial knee replacement (PKR), in which just the diseased compartment of the knee is replaced, or total knee replacement (TKR). In contrast to total knee replacement, partial knee replacement replaces only the damaged or diseased segment of the knee with a prosthesis. PKR is a less common treatment than complete knee replacement.

What is partial knee Replacement (PKR)?

Some individuals may benefit from a partial knee replacement (PKR), also known as unicompartmental knee replacement, for arthritis-related knee discomfort. Partial knee replacements are procedures in which one side of the knee joint is removed and replaced with a prosthesis, generally owing to wear and tear on the cartilage and bone from arthritis. A partial knee replacement (PKR) is a less invasive procedure than a whole knee replacement, resulting in a faster recovery period.

When only a segment of the knee is affected by arthritis, partial knee replacement involves removing only the diseased or damaged tissue and bone in the knee joint. The rest of the knee is usually preserved. Originally reserved for older patients who engaged in a few physical activities, this therapy is now often used on younger patients since their recovery is less painful and quicker.

Because of advancements in surgical procedures and equipment, partial knee replacement is becoming a more realistic option for a rising number of patients. According to current research, ranging from 10% to 25% of all patients with knee osteoarthritis who require replacement surgery may be candidates for the operation.

Knee anatomy

The knee joint is the biggest in the human body and the most usually afflicted joint by arthritis. At the knee joint, three bones come together and rub against each other:

• The femur (thigh bone) joins the tibia (shin bone) at the bottom and front of the femur. The patella (kneecap) slides along a groove at the bottom and front of the femur.

Articular Cartilage of the Knee

The surfaces of the bones where they meet are covered in articular cartilage: the bottom of the femur, the top of the tibia, and the rear of the kneecap. Articular cartilage is a slippery, tough, and flexible substance.

Articular cartilage serves two purposes:

• It permits the bones to slide over one other as the knee bends and straightens.
• It works as a shock absorber, cushioning bones from colliding (e.g. during walking)

Knee Meniscus

A meniscus is a thick cartilage pad placed between the femur and tibia in the knee. In each knee, there are two menisci:

• The medial meniscus, which is located on the inside of the knee.
• The lateral meniscus, located on the outer side of the knee.

When the knee moves or bears weight, the menisci absorb stress and absorb impact. They also serve to support the knee and allow for seamless mobility between the knee surfaces.

Ligaments of the Knee

Ligaments are strong tissue bands that link bones. The femur is connected to the tibia by four main ligaments in the knee:

• Anterior cruciate ligament (ACL)
• Posterior cruciate ligament (PCL)
• Medial collateral ligament (MCL)
• Lateral collateral ligament (LCL)

The ACL and PCL keep the femur and tibia from slipping forward or backward too far. The MCL and LCL keep you from moving side to side.

A relatively recent discovery discovered another ligament in the knee known as the anterolateral ligament (ALL), which appears to act in tandem with the ACL. However, research is currently being conducted to determine its precise role and relevance in the function and stability of the knee.

Who is a Good Candidate for Partial Knee Replacement?

Partial knee replacement is acceptable for individuals with localized arthritis to a single compartment of the knee and is typically limited to people who are not excessively obese (BMI greater than 40). The operation is not recommended for individuals who have severe knee stiffness or a substantial angular deformity. To be a candidate, a patient's knee ligaments must be intact. Patients with an untreated ruptured ACL, for example, are frequently denied partial knee replacement. People with rheumatoid arthritis of the knee may also be ineligible because inflammatory arthritis usually affects the entire joint.

Additional factors are considered on an individual basis, with the surgeon and patient deciding jointly if partial knee replacement is the best treatment choice. One of the most essential elements in assuring a satisfactory functional result and lifespan for a partial knee replacement is selecting the proper patient. This procedure is occasionally preferred for people over the age of 80, even if they do not match all qualifying requirements, because it requires less trauma than a total knee replacement.

What is a partial knee replacement prosthesis made of?

All knee replacement implants and prostheses are constructed of metal and plastic. These surfaces are intended to slide easily against one another, much like cartilage in a healthy knee. The surgeon will employ either a unicondylar fixed-bearing knee replacement or a mobile-bearing unicondylar knee replacement depending on which compartment is compromised and whether the patient's anterior cruciate ligament (ACL) is intact.

What Are the Advantages of Partial Knee Replacement Over Total Knee Replacement?

The surgery is essentially a resurfacing process, with excellent results. It is a quicker recovery. Because you preserve all of your regular ligaments in the knee, it provides a better kinematic knee (more normal biomechanics). When compared to full knee replacement, there is less blood loss, a lower incidence of infection, greater satisfaction ratings, and a higher percentage of patients feeling like they have a more natural knee.

Furthermore, you haven't ruined your chances of receiving a complete knee replacement. I believe it will be very useful to the young kid; we will be able to buy them more time before they require a total knee replacement. The operation may also be advantageous for an elderly patients whose partial knee replacement will outlast them.

Before Surgery

A doctor from the anesthesia department will review your anesthetic options with you prior to your surgery. During your preoperative clinic sessions, you should have also discussed anesthetic choices with your surgeon. Options for anesthesia include:

• General anesthesia, in which you are put to sleep.
• Spinal, in which you are awake but your body is numb from the waist down.
• Peripheral nerve block. Nerve blocks are a form of regional anesthesia in which numbing medicine is administered near a specific nerve or nerves to block pain sensations in that area of the body. These blocks can be used with general or spinal anesthesia.

Before surgery, your surgeon will also meet you and sign your knee with a marker to confirm the operative location.

Surgical Procedure

A partial knee replacement surgery usually takes between 1 and 2 hours. The joint is being inspected. An incision will be made in the front of your knee by your surgeon. They will next examine all three compartments of your knee to ensure that the cartilage damage is restricted to one compartment and that your ligaments are in good condition.

If your surgeon believes that your knee is not suited for partial knee replacement, he or she may do a whole knee replacement instead. Before your procedure, your surgeon will have reviewed this contingency plan with you to ensure that you agree with this method.

A partial knee replacement implant.

There are three basic steps in the procedure:

• Prepare the bone. Your surgeon will use special saws to remove the cartilage from the damaged compartment of your knee.
• Measure the size of your bones and position the metal implants. The lost cartilage and bone are replaced with metal covers that mimic the joint surface. These metal components are often cemented to the bone. In cementless fixation, the metal pieces are press-fit to the bone, allowing bone to grow onto the implant.
• Insert a spacer. To provide a smooth gliding surface, the surgeon inserts a plastic insert between the two metal components.

Recovery area You will be brought to the recovery room following the operation, where you will be closely observed by nurses as you recover from the anesthetic. You will then be sent home or transferred to your hospital room if you require overnight care.

What can I expect from PKR? 

Following an initial assessment, your surgeon will select the best course of therapy. The following are the benefits of partial knee resurfacing surgery:

• A comprehensive pre-operative examination focused on preparing you for your partial knee resurfacing surgery.
• The surgery takes between one and two hours.
• Two to three days in the hospital, with physical rehabilitation starting the day after surgery.
• Pain treatment regimen that reduces reliance on pain medicines every few days
• Physical treatment for six weeks
• Within six to twelve weeks of surgery, patients can resume regular, ordinary activities.

Is partial knee replacement painful?

All operations cause some discomfort. While discomfort after partial knee replacement varies by patient, patients often feel less pain and stiffness than they do after total knee replacement.

Most patients take 7 to 14 days of prescription pain medication after partial knee replacement surgery. Furthermore, physicians and researchers are presently employing treatment regimens that reduce the quantity of pain medication required following partial knee replacement surgery, including nerve block injections to administer medication locally.

How long does it take to recover from a partial knee replacement?

• Hospital discharge

Patients getting partial knee replacement often have less postoperative discomfort and edema, as well as an easier recovery than patients undergoing total knee replacement. In rare situations, patients are admitted to a skilled nursing (rehabilitation) facility following surgery.

• Pain management

 You will have some discomfort following surgery, but your surgeon and nurses will make every effort to make you as comfortable as possible.

Opioids, nonsteroidal anti-inflammatory drugs (NSAIDs), and local anesthetics are among the medications available to assist reduce pain. Medication can make you feel more comfortable, which will help your body heal and recover faster following surgery.

Opioids are effective pain relievers; unfortunately, they are narcotics and can be addictive. It is critical to use opioids only as prescribed by your doctor and to discontinue them as soon as your pain begins to improve.

Weightbearing. You will be able to put weight on your knee shortly following surgery. For the first few days or weeks, you may need to use a walker, cane, or crutches until you are comfortable enough to walk without help.

• Rehabilitation exercise

A physical therapist will prescribe exercises to help you maintain your range of motion and regain strength. You will continue to see your orthopedic surgeon at regular intervals for follow-up appointments in their clinic. By 6 weeks after surgery, you should be able to resume all of your normal daily activities.

What is the Success Rate of a Partial Knee Replacement?

Approximately 9 out of 10 patients who have a PKR are satisfied.

• 85% return to work and or sport
• When a PKR fails with time it is usually converted to a total knee replacement
• About 90% of PKRs are still functioning at 5 years
• About 90% of PKRs are still functioning at 10 years
• Because only part of the knee has been replaced patients can still have symptoms from unreplaced areas.

What kind of problems can occur with partial knee replacement surgery?

Partial knee replacement typically results in minimal blood loss and has a low likelihood of complications. Complications may include knee instability, implant loosening, infection, nerve damage, and deep vein thrombosis, like with any joint replacement operation. Complications are less common after partial knee replacement than they are after complete knee replacement. Discuss any concerns you have about these or other issues with your surgeon.

Patients who have been appropriately evaluated for the treatment should expect few problems and a quick recovery. However, similar to other forms of knee surgery, revision operations are necessary for a small number of instances. The outcomes of revision surgery may not be as excellent as those of first surgery.

How long does a partial knee replacement last?

In the first decade after surgery, a well-done partial knee replacement in an adequately selected patient can have an implant survival rate equivalent to that of a whole knee replacement. According to the research, partial knee surgery may have a greater revision rate than total knee surgery after the second decade.

What are recent technological advances in partial knee replacement?

Partial knee replacement has long been considered a specialty operation. It was performed by a few numbers of surgeons since it needed careful patient selection and a high degree of ability to ensure a successful outcome. One-third of my arthritic knee patients would benefit from a partial knee replacement. Because to technological developments, the capacity to do partial knee replacements is rising.

The MAKO Robot, which was first used for partial knee replacement, allows us to generate a live GPS during surgery by using 3D planning from a CT scan and real-time information of where the knee is in space. It enables us to correctly locate the patients' components, size them, and balance the knee with regard to its existing ligaments. As a result, patients heal faster, have better biomechanics, a more normal-feeling knee, and have favorable long-term results for up to 15 years. 

Conclusion 

Partial Knee Replacement is a less invasive operation in which an implant replaces only the damaged compartment of the knee. If your arthritis is limited to a single compartment of your knee, you may be a candidate for partial knee replacement surgery.