Unicompartmental Knee Replacement Surgery
Under certain conditions a “partial” knee replacement may be indicated. Here, only “half” of the knee joint is replaced and most of the soft-tissue is preserved. This procedure is often less invasive and recovery can be smoother. Recently, surgeons have been performing “Minimally Invasive” or MIS Uni procedures. The relatively small implants and the need for less exposure allows for a smaller incision and less invasive procedure compared to a Total Knee. However, in order to be a candidate, joint degeneration is usually limited (your doctor must determine if a “uni” is indicated).
In this type of replacement a single “compartment” of the knee joint is replaced. Most of the time it is the medial compartment (the “inside” of your knee joint). The patella is left alone and only half of the femur and tibia are resurfaced. The components, like in a Total Knee, are metal and plastic and are usually cemented in place. There are even fixed and mobile bearing versions just like in a Total Knee.
Typically the femoral component is Cobalt Chrome and the Tibial component consists of a metal and plastic combination or an all plastic version.
The link below has some photos and additional information on Unicompartmental Knee Replacement.
http://orthopedics.about.com/cs/kneereplacement/a/kneeuni.htm
Knee Replacement FAQ
Q. What, exactly is “replaced” in knee replacement?
A. The worn ends of the femur ( thigh bone), tibia (shin) and patella (knee cap) are removed with a saw and replaced with metal and plastic. More on Knee Replacement Surgery
Q. What, is a Knee Replacement Implant made of?
A. Implants are typically made of a combination of Cobalt Chrome and/or Titanium metals and UHMWPE (ultra- high-molecular-weight polyethylene) plastic. More on Knee Implants.
Q. Are there different kinds of implants?
A. Yes! There are many types of implants that fit into broad categories related to their interaction with the remaining natural soft tissue. For example a CR or Cruciate Retaining knee implant is designed to work with the PCL (posterior cruciate ligament) intact. Other types of implants are designed to work without it. In addition, there are many manufacturers of implants which create several brands of knees in each of the broadcategories. Surgeons have many, many choices. More on Types of Knee Implants. Links to Implant Manufacturers
Q. How long will my Knee Replacement last?
A. There are many studies on this topic and the actual time an implant will survive before needing revision will vary on a case by case basis. Several studies demonstrate greater than 90% survivorship at 15 years (1)
Q. How are the implants held in place?
A. 
Total knee replacement implants are secured to the bone either with a special polymeric compound (“bone cement”) or are “press-fit” into place. Press fit implants have rough or porous under surfaces into which bone will grow. More on Knee Implants.
Q. What is a Uni (or Partial or Half-knee) Replacement?
A. A “Uni” or unicompartmental knee replacement replaces only the medial (inner) or lateral (outer) half of the knee joint (the tibio-femoral joint). The knee cap or patella is not replaced. More on Unicompartmental Knee Replacement
Q. What is MIS or Minimally Invasive Knee Replacement?
A. MIS or Minimally Invasive Knee Replacement is like standard knee replacement except that the incision is smaller, and care is taken not to resect the quadriceps muscle (also known as “quad sparing”). Also, the patella is not “everted” or “flipped” over This is all intended to result in less trauma and speed recovery. More on Minimally Invasive Knee Replacement.
Q. What about recovery, pain etc?
A. Every case is unique and this discussion is best left for a medical professional. You can read about the experience of other recipients at a very interesting discussion forum at Robin’s Total Knee Replacement.
References 1) Dixon MC, Brown RR, Parsch D, Scott RD. Modular fixed-bearing total knee arthroplasty with retention of the posterior cruciate ligament. A study of patients followed for a minimum of fifteen years. J Bone Joint Surg Am. 2005 Mar;87(3):598-603
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Introductory Topics
Introduction - Home Normal Knee Anatomy The Diseased Knee: Osteoarthritis The Knee Replacement Procedure
Surgery Overview > Total Knee Replacement Surgery Video Knee Replacement Complications Minimally Invasive Knee Replacement Unicompartmental Knee Replacement Computer Assisted Knee Replacement Knee Replacement Implants
The Parts of a Total Knee Replacement Mobile Bearing Knee Replacement Knee Implant Wear Knee Implant Manufacturers Related Topics
Knee Arthroscopy Total Hip Replacement Osteoporosis -
- To Retain or Sacrifice the PCL…That is the Question
- The Impact of “High-Risk” Sports in Knee Replacement Patients
- Video Showing a Traditional Total Knee Replacement Surgery
- Mobile Bearing Knee Replacement Offers no Benefits vs. Fixed Bearing
- Press-Fit Total Knee Replacement: Working to Prevent Loosening and Bone Loss
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