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KneeMainPageImageComputer Assisted Surgery for Total Knee Replacements

There are more than 600,000 knee replacement surgeries performed each year in the United States according to the American Academy of Orthopaedic Surgeons.[1]  The evolution of technology and surgical techniques continue to improve the effectiveness of knee replacement procedures.  Several factors impact the success of a total knee replacement surgery. One such factor is the proper alignment of the knee implant components to the patient’s unique anatomy.  Studies have shown a well-aligned knee replacement may last longer and be less likely to dislocate.[2][3]  This is a major reason why orthopaedic surgeons may choose to utilize computer assisted surgery (CAS) in their practices.
 
During a total knee replacement, the end of the femur (thigh bone) and the top of the tibia (shin bone) are resurfaced.  The knee implant is composed of metal and polyethylene – a durable plastic.  The femoral and tibial components glide together to replicate the knee joint.  The end of the femur and the top of the tibia are cut to match the corresponding surfaces of the implant components.  CAS enables surgeons to make these boney cuts within a fraction of a degree, allowing for more accurate alignment of the implant specific to the patient’s unique anatomy. 
 
Stryker’s CAS technology for orthopaedic surgery consists of 1.) an infrared navigation camera, 2.) Smart Instruments with light-emitting diode (LED) technology and 3.) a computer with specialized surgical navigation software.

The general premise behind computer assisted surgery is the computer software generates a virtual model of the patient’s knee anatomy and that serves as a “blueprint” for the surgeon to follow.  The navigation camera tracks the location and movement of Smart Instruments during the procedure and relays this information to the navigation computer.  The software then displays in real-time on the virtual model the exact position of Smart Instruments and implant components in relation to the patient’s anatomy.   

In the operating room, Smart Instrument trackers are attached to the patient, so the navigation camera is able to track the location and movement of the patient’s knee throughout surgery.  In a process called patient registration, the surgeon puts the leg through a series of motions and uses a Smart Instrument pointer to touch off on distinct anatomical landmarks of the patient’s knee.  This data is used by the computer software to generate the virtual model of the patient’s knee.  Once patient registration is complete, the computer software provides the surgeon with valuable information including the angles, lines and measurements of the patient’s unique anatomy and displays the exact location of Smart Instruments in relation to the knee joint all in real time.

CAS does not replace a surgeon’s skills but provides the surgeon with a comprehensive understanding of the patient’s own knee anatomy and kinematics to help determine proper placement of the implant.     This information and guidance is not available with conventional, mechanical instruments.

“Implant alignment with navigation (CAS) is much approved over mechanical instruments.  There have been studies that show improved functional results with navigation, says Dr. Knute Buehler, orthopaedic surgeon at St. Charles Medical Center, Bend, OR.  “Patients that were within 3 degrees neutral biomechanical axis had much improved Knee Society Functional Scores at three months and one year after surgery, compared to those patients with more mal-aligned knees.”

In addition to arming an orthopaedic surgeon with information to ensure the new knee joint has the stability and range of motion necessary for a successful replacement, CAS has other advantages.  CAS allows for enhanced visualization of the anatomy, which is particularly important when minimally invasive techniques are used.  This technology further provides the surgeon with feedback and the ability to correct potential misalignment in surgery, before any boney cuts are made.

CAS technology offers a total knee replacement patient several benefits including:

  • With CAS technology, surgeons are able to make precise adjustments to ensure the optimal implant fit.  This may help to reduce joint wear and extend the life of the implant.
  • CAS may allow for less invasive techniques which have other potential advantages including: shorter post-operative physical rehabilitation,[4] smaller incision[5], less blood loss compared to a standard knee replacement.[6]


If you are reading this, chances are you or someone you know might be considering total knee replacement surgery. There are risks associated with computer assisted knee replacement surgery as with any surgery. To read more about the risks associated with total knee replacement surgery you may visit http://www.aboutstryker.com/knee/expectations/risks-complications.php.  Be sure to talk to your doctor about what treatment options are appropriate for you and the risks associated.

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Surgeon Testimonials

Dr.Buehler210x210

Implant alignment with navigation is much approved over mechanical instruments.  There have been studies that show improved functional results with navigation.  Patients that were within 3 degrees neutral biomechanical axis had much improved Knee Society Functional Scores at three months and one year after surgery, compared to those patients with more mal-aligned knees.  As more and more instruments and devices in our society are computerized, it seems to me somewhat of a throwback to be stuck with mechanical instruments as we enter in to the computer age.”
 
Dr. Knute Buehler
Orthopaedic Surgeon
St. Charles Medical Center, Bend, OR

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Image Gallery

(Knee) Knee Navigation OR SetupStryker’s computer assisted surgery technology aides in the accurate positioning of implants during total knee replacement surgery. As the surgeon moves a Smart Instrument within the knee joint, special infrared trackers calculate its position.

(Knee) Navigation Screen on MonitorIntuitive software provides surgeons with a comprehensive understanding of the patient’s joint and kinematics during total knee replacement surgery. The computer analyzes and displays data the surgeon needs to make more exact boney cuts and accurately align the implant to the patient’s unique anatomy.

(Knee) precisioN Automatic Implant Positioning ScreenshotThe real-time data enables the surgeon to make intra-operative adjustments within a fraction of a degree, helping to ensure the best possible fit of the implant during total knee replacement surgery. The navigation computer software provides the surgeon with a “blueprint” to help plan and follow throughout surgery.

(Knee) Dr.BuehlerDr. Knute Beuhler of St. Charles Medical Center performs a total knee replacement on a patient with Stryker’s computer assisted surgery (CAS) technology. CAS aids in implant alignment and accuracy.

 

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