Total Knee Replacement-An Introduction


Total Knee Replacement is a surgical procedure in which the knee joint, which comprises the lower end of femur and upper end of tibia are replaced by a  prosthesis.

Usually it is done in cases of chronic knee pain due to degeneration, injury etc  and which is  not being managed conservatively with help of medications or physical therapy.

Causes chronic knee pain and disability are

Osteoarthritis: This is the age related wear and tear of the joint. The cartilage that cushions the bones of the knees softens and wears away.

Rheumatoid Arthritis :This is a disease in which synovial membrane of the joint becomes inflamed and thickened eventually leading to cartilage loss, pain and stiffness.

Post traumatic arthritis: This can follow a serious knee injury.

The surgery is recommended when

  • Severe knee pain or stiffness that is limiting the everyday activity.
  • Moderate to severe knee pain in resting day or night.
  • Chronic knee inflammation.
  • Knee deformity.
  • Failure to substantially improve with conservative management.

POSSIBLE COMPLICATIONS

  1. Wound infection
  2. Blood clots
  3. Implant problems
  4. Continued pain
  5. Neurovascular injury

TYPES OF IMPLANTS USED

The implants are not one size fits all. Prosthesis implants vary greatly by design, fixation and material.

TOTAL KNEE IMPLANT COMPONENTS

THE FEMORAL COMPONENT: Made up of metal and curves around the lower end of femur.Also it has a groove which fits in the patella.

THE TIBIAL COMPONENT: It is a flat metal platform with a polyethelyne plastic insert or spacer.

THE PATELLAR IMPLANT: It  is a dome shaped polyethylene knee cap.

TYPES OF PROSTHESIS

a) FIXED BEARING IMPLANTS

This is the most common implant. Its is called fixed because the cushion of tibial component is fixed firmly to metal platform base.It provides good range of motion.

b) MOBILE BEARING IMPLANTS

If you are young and more active and or overweight the doctor may recommend a rotating platform or mobile bearing knee replacement, the implants are designed for longer performance.

The difference between fixed and mobile bearing implant is the bearing surface is though both use the same 3 components, in mobile bearing the polyethylene insert in tibial component can short distances inside the metal tibial tray. This rotation allows greater rotation to medial and lateral sides of their knee, rotate but this does require a strong ligament support otherwise chances of dislocation are there,

c) MEDIAL PIVOTAL IMPLANT

It replicates rotating, twisting, bending , flexion and stability of natural knee.The locking and unlocking mechanism is quite perfectly mimicked by this knee. But compared to above two knees this implant is less forgiving of imbalance in soft tissues

d) POSTERIOR CRUCIATE LIGAMENT RETAINING OR SUBSTITUTING IMPLANT

The PCL is one of the most important ligament to support and stabilize the movement of knee and preventing femur to roll back on top of tibia hen flexed.

PCL retaining: In this design, rearwards movement of tibia continues to be resisted by intact PCL creating stability.t= The prosthesis have notches to accommodate ligament.

PCL substituting: They have raised surface on tibial component cushion with raised sloping cam or post which compensates for missin PCL to give stability.

e) UNICOMPARTMENTAL IMPLANTS

If only one side of knee joint is damaged smaller implants can be used to resurface other side.

f) GENDER SPECIFIC INPLANTS:

Some orthopaedic have recently introduced gender specific implants, considering the geometrical difference between both sexes.

TYPES OF KNEE IMPLANT FIXATION

Cemented prosthesis utilize special kind of bone cement that holds components. This is most commonly used,

Cementless it becomes fixed with bone growth into surface of implant, but recovery takes little longer.

COMING SOON!!!!
Exercise therapy and Do’s and Don’t’s after a total knee replacement.

 

Advertisements

One thought on “Total Knee Replacement-An Introduction

  1. Pingback: Zimmer Knee Failure | Zimmer Knee Lawyer « Earl's View

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s