What is New in Knee Replacement

If you are considering knee replacement surgery, there are new developments under study which can help enhance the quality of life. These include:

  • Use of cementless parts that allow new bone to grow into a porous prosthesis and hold the parts in place, creating a biologic fixation
  • Use of bioactive joint surfaces such as hydroxyapatite
  • Use of mobile-bearing knee replacement in which a polyethylene insert creates a dual-surface articulation by articulating with the femoral as well as tibial components. This will enhance the life of the implant by reducing wear.
  • Development of systems with improved kinematics
  • Better fixation
  • Use of navigation-guided surgery that involves the use of navigation-guided instruments with smaller incisions and less tissue damage. 

Only suitably-trained surgeons with various skills offer these procedures.

 

After Knee Replacement

What is Knee Replacement?

Knee replacement is a surgery performed to replace parts of a diseased knee joint with artificial prostheses. The goal of knee replacement is to eliminate pain and return you to your normal activities. You can help in recovery and improve the outcomes of the procedure by following certain precautions and changing the way you carry out your daily activities.

What happens after Knee Replacement?

After knee replacement surgery, once the anesthesia wears off, you will start to experience pain, for which your doctor will prescribe medication. You may have to remain in the hospital for a few days depending on your progress and overall health. Remember to get plenty of rest during this initial phase. Your surgical wounds should be monitored for swelling, inflammation and other changes and frequent dressing changes are performed. A continuous passive motion (CPM) machine is fixed to keep your knee moving. Compression boots or elevation of your leg may be recommended to encourage circulation and prevent stiffness, clots and scar formation.

Rehabilitation after Knee Replacement

Rehabilitation begins within 24 hours of surgery, where a physical therapist will help you stand up and walk using crutches or a walker. Adhering to the goals of the rehabilitation program is important to help you recover and resume your normal activities. You will be guided to perform strengthening exercises daily and learn to get in and out of bed, and use a bedside commode. 

Recovery at Home after Knee Replacement 

When you are discharged from the hospital, you will be encouraged to walk short distances with an assistive device, climb a few stairs, dress, bathe and perform other basic functions by yourself. On reaching home, have a family member or caregiver assist you with your activities for a few weeks. Taking care of someone following knee replacement surgery requires compassion, awareness, and patience. The basic points to be followed by your caregiver include:

  • Helping with basic movement and functions as well as emotional support
  • Having a clear understanding of your medication and ensuring they are administered in a timely manner
  • Keeping emergency numbers ready
  • Assisting you with household chores, paperwork and traveling to keep your appointments
  • Helping and motivating you to perform your rehabilitation exercises
  • Ensuring that furniture is rearranged so as not to interfere with your movement and cause falls. 
  • Avoiding bending or reaching out for items that you frequently use by placing them within easy reach

You and your caregiver must be aware of the signs of infection. Contact your doctor if you notice any abnormal wound changes or any changes in general health and mental state, or should you have persistent fever, drainage, excessive swelling or other signs of infection. 

Certain instructions that your doctor will brief you about include:

  • You may shower once the wound heals, but avoid soaking in a bathtub for at least six weeks.
  • Keep the wound clean and dry. Your doctor will let you know when you can shower or bathe. 
  • Some amount of swelling is normal after knee replacement and may last for more than a month. It can be controlled by placing ice on the knee and elevating your leg for 30 to 60 minutes every day. 

Downtime

By week 3, you should be able to move with minimal assistance and significant reduction in pain. Your physical therapy program will gradually include new and more difficult exercises as you improve in strength and flexibility. By week 7, you should be able to walk independently. To reduce stress, use the opposite knee to lead when climbing stairs and the replaced knee to lead when descending. 

You will be able to drive a few weeks after surgery when you have sufficient pain control, improved strength and can easily enter and exit a car. 

Walking and exercising at least 2-3 times a day for 10-15 minutes is recommended for a faster recovery.

 

 

Custom-fitted Total Knee Arthroplasty

What is Custom-fitted Total Knee Arthroplasty?

Custom-fitted total knee arthroplasty is a newer more advanced technology in total knee replacement surgery that uses an individualized patient-specific knee implant for the replacement of all three components of the knee. 

The difference with custom knee replacement from other knee replacement surgeries is the use of an MRI scan prior to the surgery to obtain a clear view of the shape and structure of the different components of the joint. The implants are then designed specifically to match the natural shape of the articulating surfaces of your knee based upon the MRI. Unlike other knee replacement surgeries, custom-fitted total knee replacement can also be used for severe knee arthritis. 

Custom-fitted Total Knee Arthroplasty Procedure

Prior to the surgery, several MRI scans are taken to understand the specific anatomy of the affected joint. Along with the MRI images, a special tool called a jig is also used to provide a clear view of implantation. The patient-specific jigs have built-in image guidance that simplifies the surgical procedure and improves the outcome. Based on the MRI images, your surgeon plans the surgery and calculates the cutting measurements, which help your surgeon to remove the exact amount of bone, at specific angles. This customized cut provides better implantation, more reliable alignment, and removal of less amount of bone. 

Benefits of Custom-fitted Total Knee Arthroplasty

There are several advantages to customized total knee replacement arthroplasty over the regular traditional implants, which include:

  • No compromise on the size of the implant as it is patient-specific 
  • Provides a better fit of the implant as the implant conforms to your unique shape of the articulating surfaces of the knee joint
  • Maximizes the implants contact area, decreasing the polyethylene contact stress; thereby, prolonging the life of the implant
  • Preserves more natural bone
  • Maximizes proximal tibial coverage and thus reduces the risk of tibial implant caving in and loosening

 

 

Signature Knees

Knee Anatomy

The knee joint, made up of the ends of the femur (thighbone) and tibia (shinbone) is cushioned by a spongy tissue called cartilage. Damage and wear and tear of the cartilage cause painful rubbing of the joint bones, leading to disability. This condition can be successfully treated with knee replacement surgery, which involves the replacement of the damaged tissue with a prosthetic implant. 

Signature Knee System

Signature knee is a unique knee replacement procedure that is tailored to suit your individual anatomy. The technique utilizes magnetic resonance imaging (MRI) technology to create 3D images of your knee joint, which enables your doctor to efficiently plan your knee replacement surgery. The signature system also helps design and creates patient-specific femoral and tibial positioning guides that will be used during the knee replacement surgery to ensure a perfect fit of the knee implant. 

Signature vs. Traditional Knee Replacement

Before the knee replacement surgery, the signature system requires an MRI scan to obtain 3D images of the knee joint, while traditional surgeries are based on 2D images generated by X-rays. While the traditional procedure uses and places multiple instruments to assist and verify proper alignment and positioning of the implant, the signature system uses customized positioning guides directly on the femur and tibia bones and does not require any instrumentation of the bone canal, enabling a less invasive surgery. 

Advantages of Signature Knee Replacement

The following are the advantages of the signature knee system:

  • It is a very specific and personalized approach to knee replacement.
  • It is based on your unique anatomy.
  • It uses 3D MRI instead of 2D X-ray.
  • It helps your doctor position the implant accurately, as the guides are patient-matched.

 

 

Knee Implants

What are Knee Implants?

Knee implants are artificial devices that form the essential parts of the knee during a knee replacement surgery. The knee implants vary by size, shape, and material. Implants are made of biocompatible materials that are accepted by the body without producing any rejection response. Implants can be made of metal alloys, ceramic or plastic, and can be joined to the bone. The metals used include stainless steel, titanium, and cobalt chrome; whereas, the plastic used is polyethylene.

Components of a Knee Implant

The components of a knee implant replicate the natural shape and structure of the knee joint. The components used may depend on the size of your body and vary from patient to patient. There are 3 components in a knee implant:

  • The femoral component is generally made of metal and curves around the thighbone. It has a channel that allows the kneecap to move up and down as the knee is in motion.
  • The tibial component is usually a flat metal platform with a plastic (polyethylene) cushion. The metal portion has a stem that goes into the tibia for stability. The plastic portion, also known as a spacer, acts as a cushion between the femoral and tibial metallic components.
  • The patellar component is a dome-shaped device made of polyethylene that replicates the patella.

Types of Knee Implants

The type of implant used may depend on your bone quality and health of the ligaments surrounding the knee. Based on your age and activity level, there are different types of knee implants used in knee replacement surgery.

  • Fixed bearing implants: The polyethylene part of the tibial component is attached firmly to the metal platform. The femoral component moves on the cushion provided by the polyethylene implant. Fixed bearing implants are generally used in less-active and elderly patients.
  • Mobile bearing implants: The polyethylene part of the tibial component can rotate inside the metal part, and therefore provides you with greater mobility. 

Mobile bearing implants are designed to bear greater stress compared to fixed bearing implants and require greater support from the ligaments surrounding the knee. Mobile bearing implants are preferred in generally young and active patients. Medial pivot implants are a type of mobile bearing implants that can twist, bend, rotate, flex and perform all the functions of a natural knee.

  • Posterior cruciate ligament (PCL) substituting implants: The posterior cruciate ligament stabilizes the knee against forces that push the tibia towards the femur. PCL substituting implants are used if your PCL is injured. The PCL substituting implants are provided with a raised surface on the cushion of the tibial component, which acts as a center post, fits into a cam in the femoral component and duplicates the actions of the injured PCL.
  • Posterior cruciate ligament retaining implants: PCL retaining implants can be used if you have a healthy posterior cruciate ligament. Unlike PCL substituting designs, PCL retaining implants do not have the center post and cam design. The femoral and tibial components have grooves to hold the posterior cruciate ligament. 
  • Custom knee implants: For patients with smaller bone structure, the sizes of the implants required may vary. Gender-specific implants and narrow femur implants, can provide better alignment of the bones, and may be used depending on the preference of your surgeon.

Types of Fixation

Depending on your age and activity level, your surgeon may recommend any of the available three types of implant fixation.

  • Cemented fixation: The components of the artificial joint are held together with special bone cement. The bone cement is made from a special polymer called polymethylmethacrylate (PMMA). Cemented fixation is an option if you are less active. Too much stress on the cemented fixation can lead to fatigue fractures.
  • Cementless fixation: Cementless implants are coated with a porous material. They attach to the new bone that grows to the surface of the implant via bone ingrowth. The implant may be fixed using screws or pegs until bone ingrowth. Cementless fixation is an option if you are active with good bone quality.
  • Hybrid fixation: Hybrid fixation uses a combination of cemented and cementless fixation. The tibial and patellar components are fixed with cement, and the femoral component is fixed without cement.

 

Patellofemoral Knee Replacement

Compartments of the Knee

The knee can be divided into three compartments: patellofemoral, the compartment in front of the knee between the kneecap and thighbone, the medial compartment, on the inside portion of the knee, and lateral compartment which is the area on the outside portion of the knee joint. 

What is Patellofemoral Knee Replacement?

Traditionally, arthritis in only one compartment of the knee is treated by partial knee replacement surgery. Patellofemoral knee replacement is a minimally invasive surgical option performed in the patellofemoral compartment only, preserving the knee parts not damaged by arthritis as well as the stabilizing anterior and posterior cruciate ligaments (ACL and PCL). 

The smaller implants used with a partial knee replacement surgery are customized to your anatomy based upon CT scans of your knee. A surgical robotic arm assists your surgeon with pre-operative planning and intraoperative component placement, positioning, and alignment. Patellofemoral knee arthroplasty surgery will not alter your ability to eventually move to a total knee replacement in the future should that become necessary. 

Indications of Patellofemoral Knee Replacement

Patellofemoral knee replacement surgery may be recommended by your surgeon if you have not obtained adequate relief with conservative treatment options. This less invasive bone and ligament preserving surgery are especially useful if you are young and active as the implant closely mimics the actual knee mechanics when compared to total knee surgery.

Patellofemoral Knee Replacement Procedure

Patellofemoral knee replacement surgery is performed on an outpatient basis as day surgery, under general anesthesia or spinal anesthesia with sedation. Your surgeon makes a small incision, about 3-4-inches long over your knee. With the assistance of the robotic arm, the patellofemoral compartment is prepared for the artificial components by removing the damaged part of the patella and trochlea, the groove at the end of the femur. The new artificial components are fixed in place with the use of bone cement. 

The femoral component is made of polished metal and the patellar component looks like a plastic button that will glide smoothly in a groove located on the femoral component. With the new components in place, the knee is taken through a range of movements. Once your surgeon is satisfied with the results, the surgical instruments are removed and the incisions covered with a sterile dressing or biologic glue. 

Postoperative Recovery after Patellofemoral Knee Replacement

You will be taken to the recovery room and monitored for any complications. You will be given pain medication to keep you comfortable at home. You will need someone to drive you home due to the drowsy effects of the anesthesia. Swelling is normal after knee surgery. Ice, compression, and elevation of the knee will help minimize swelling and pain.

You will be given specific instructions regarding the activity. Usually, there are a few activity restrictions. You will be referred to a rehabilitation program for exercise and strengthening. Eating a healthy diet and not smoking will promote healing.

Risks and Complications of Patellofemoral Knee Replacement

As with any major surgery, there are potential risks involved with patellofemoral knee replacement. The decision to proceed with the surgery is made because the advantages of surgery outweigh the potential disadvantages. Some of the possible complications include:

  • Allergic reactions to medications
  • Blood loss requiring transfusion with its low risk of disease transmission
  • Heart attacks, strokes, kidney failure, pneumonia, bladder infections
  • Complications from nerve blocks such as infection or nerve damage
  • Infection 
  • Deep vein thrombosis 
  • Ligament injuries
  • Injury to blood vessels or nerves 
  • Arthrofibrosis
  • Wearing out of the prosthesis 
  • Dislocations and fractures

Risk factors that can negatively affect adequate healing after knee arthroscopy include:

  • Poor nutrition
  • Smoking
  • Obesity
  • Age (over 60)
  • Alcoholism
  • Chronic Illness
  • Steroid Use
     

 

Minimally Invasive Knee Joint Replacement

Minimally Invasive Knee Joint Replacement

Total knee replacement is a very successful surgical treatment for knee arthritis. Over the years, minimally invasive knee replacement surgical techniques have been developed to lessen tissue trauma and improve patient outcomes. This minimally invasive approach involves much smaller incisions than the usual 10-12 inch incisions used in the traditional knee replacement and spares the quadriceps muscle and tendon, which control bending of the knee, from being cut to access the knee joint.

The smaller incisions with minimally invasive surgery mean fewer tissues are cut resulting in quicker healing and recovery. The potential advantages of minimally invasive joint replacement surgery are:

  • Minimal surgical dissection
  • Shorter recovery period
  • Shorter hospital stay
  • Reduced post-operative pain    

Procedure

Minimally invasive surgery for knee replacement involves the use of smaller incisions which are only 4 to 6 inches in length as compared to the 10-12 inch long incision used in the traditional procedure.

  • Surgery is performed under sterile conditions in the operating room under spinal or general anesthesia. You will be lying on your back on the operating table with a tourniquet applied to your upper thigh to reduce blood loss.
  • Your surgeon will then make an incision along the affected knee to expose the knee joint. The surgeon first focuses on the femur (thighbone). The damaged portions of the femur are cut at the appropriate angles using specialized tools.
  • Then the femoral component is attached to the end of the femur with or without bone cement. The next step involves removal of the damaged area of the tibia (shinbone) and the cartilage. It allows for a smooth surface to which implants can be attached.
  • The tibial component is then secured to the end of the bone using bone cement or screws. Your surgeon will place a plastic piece called an articular surface between these implants to ensure a smooth gliding movement.
  • This plastic insert acts in a similar way as the original articular cartilage and helps in supporting your body weight as well as allows the femur bone to move over the tibia. The femur and the tibia bone with their new components are put together to form the new knee joint.
  • To ensure that the patella (knee cap) glides smoothly over the new artificial knee, its rear surface is prepared to receive a plastic component. With all its new components in place, the knee joint is examined through its range of motion.
  • All excess cement will be removed and the entire joint will be irrigated or cleaned out with a sterile saline solution.
  • The incision is then closed and drains are usually inserted. A surgical dressing or bandage is then placed over the incision.

As there is less tissue damage around the knee during the minimally invasive procedure surgery, you can expect a shorter hospital stay, faster recovery and also avoid an unsightly smaller surgical scar. 
 

Patient Specific Knee Replacement

What is Patient Specific Knee Replacement

Patient Specific Knee Replacement is a newer technology in total knee replacement surgery. It is an advanced procedure using an individualized patient-specific knee implant for replacement of all three components of the knee.  The difference with patient specific knee replacement from other knee replacement surgeries is the use of an MRI scan prior to the surgery that provides a clear view of the shape and structure of the different components of the joint. The implants are then designed specifically to match the natural shape of the articulating surfaces of the patient’s knee based upon the MRI. Unlike other knee replacement surgeries, patient specific knee replacement can also be used for severe knee arthritis.

Procedure

Prior to the surgery, several MRI scans are taken to understand the specific anatomy of the affected joint.  Based on the MRI images the surgeon plans the surgery and calculates the cutting measurements that help the surgeon to remove the necessary amount of bone, at specific angles. This customized cut provides better implantation, more reliable alignment, and removal of less amount of bone.

Benefits

There are several advantages to patient specific knee replacement arthroplasty over the regular traditional implants, which include:

  • No compromise on the size of the implant as it is patient specific
  • Provides a better fit of the implant as the implant conforms to the patient’s unique shape of the articulating surfaces of the knee joint
  • Maximizes the implants contact area decreasing the polyethylene contact stress thereby prolonging the life of the implant
  • Preserves more natural bone
  • Maximizes proximal tibial coverage and thus reduces the risk of tibial implant caving in and loosening