Computer Assisted Knee Replacement

Minimally Invasive Surgery (MIS) for Knee Replacement:

Minimally invasive surgery is improving patient’s lives after knee replacement. Many patients have less post operative pain, recover faster and are hospitalized for only one or two nights. The benefits derived from minimally invasive surgery are due to the fact that no incision is made in the quadriceps tendon (the large muscle on the front of the thigh) and the procedure is done through as small of skin incision as is possible (depending on individual patient factors) causing less traumas to the soft tissues. We combine MIS technique with computer navigated instrumentation for the most precise placement of your new knee. 

Computer Assisted Surgery (CAS) is one approach to reduce surgical errors and improve surgical outcomes associated with knee and hip surgery.

Computer assisted orthopaedic surgery is defined as techniques that enhance identification of surgical anatomy thereby improving surgical accuracy. These computer based tools increase the repeatability and accuracy of surgical procedures and should improve quality control in orthopaedic surgery.

Computer Navigation utilizes an operating room based computer and infra-red transducers pinned to the thigh and shin bones. The patient’s unique anatomy is mapped and displayed on the computer screen. This real time anatomic data is used to plan and verify bone cuts for precise implant placement.

Potential advantages of CAS are:

  1. Enables the surgeon to create accurate and reproducible bone cuts helping to ensure accurate placement of Total Knee implants.
  2. Greatly reduces possibility of MIS technique component mal-positioning.
  3. Vital for complex TKR when unusual bone deformities are present.
  4. Valuable tool when performing revision total knee replacement.

Potential disadvantages of CAS are:

  1. Time in operating room could be longer due to setup, calibration and usage of computer.
  2. Navigation Pin breakage, femur or tibia fracture/stress fracture, prolonged bleeding/drainage from navigation pin sites (all rarely occur).

Computer or tracker malfunction could require conversion to traditional total knee instruments (rarely occurs).

Computer Navigated Knee Replacement Surgery:

Computer Assisted Surgery helps the surgeon precisely align the artificial knee implants within a fraction of a degree. Studies indicate accurate implant alignment correlates with less implant wear and the longer life of a knee replacement.

During computer navigated surgery tracking devices (transducers) connected to threaded pins placed into the thigh bone and shin bone collects and sends an electronic signal to a computer to provide a comprehensive understanding of your joint anatomy and mechanics.

The software program maps out the unique geometry of each patient’s leg bones. This is displayed on a video screen with real time information in the operating room in the surgeon’s line of sight. The surgeon uses this map to accurately choose where to cut the end of the thigh bone and top of the shin bone for optimal anatomic implant alignment.

The navigation software records knee range of motion at the end of the operation allowing the surgeon to document each patient’s motion profile in the operative report. This is useful for directing postoperative rehabilitation.

What is computer-assisted knee replacement?

A computer with specialized software is used in the operating room to assist the surgeon to achieve proper placement and alignment of the knee prosthesis. The system provides instant information on the boney alignment of the knee joint, the function and tensions of the ligaments required for knee stability, and the special cuts that must be made in the femoral and tibial bones to achieve a precise placement of the prosthesis.

Why was computer-assisted surgery developed?

The long-term results of knee replacement operations before computer-assisted techniques were developed have been very good. In fact, total knee replacement is one of the most successful operations performed in the human body. In many published studies, over 90% of the knee replacements were reported to be intact and functioning 15 years after surgery. However, not all knee replacement procedures are successful because the exact alignment desired at surgery is not obtained. There are many reasons that cause this problem and even the most experienced joint replacement surgeons may encounter this complication.

Total knee replacements require exact alignment and balancing so that weight bearing forces are spread evenly across the knee joint. An analogy would be correctly aligning or balancing a tire on a car so that that there is even wear over an extended period of time, and not excessive wear on just one side. The same is true of a knee replacement. The plastic insert is sensitive to abnormal pressures which could result in premature wear and possible failure of the replacement.

What are the downsides of computer-assisted surgery?

There is additional time, usually 15 minutes, that is added to the operative procedure. This is necessary to input the information and recheck that the computer is collecting the correct information it requires. It is possible that the surgeon will determine that the computer is not providing the appropriate data and convert to visual alignment methods. In this case, other instruments are used in the procedure to obtain correct alignment of the replacement.

What is minimally invasive surgery of the knee joint?

This term is applied when the surgeon selects a method in which the tissues about the knee joint are disturbed or cut in the least amount possible to perform the surgery.

In years past, the use of arthroscopic-guided surgery in the knee joint was considered minimally invasive as it allowed the surgeon to perform a great deal of the surgery through small incisions. Visualization through the arthroscope decreased the need for large incisions or any incision at all. A majority of ligament reconstructions and other knee repairs are now performed by surgeons trained in these arthroscopic techniques.
Knee replacements are now being performed using minimally invasive types of techniques. The instruments used during the procedure are smaller and the incisions are also smaller resulting in fewer disturbances of the soft tissues. The computer-assisted surgical technique allows in some cases the ability to use smaller incisions as the computer provides virtual visualization or navigation during the procedure.
Whenever the surgeon can minimize the incision or disturbance of soft tissues, generally there will be less pain after surgery and a more speedy recovery. Less pain medication is necessary and the patient is out of bed sooner and more frequently. The rehabilitation process is easier and the muscles regain their function faster. This has been proven in all aspects of knee surgery when these lesser invasive techniques have been applied.