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What is Zimmer iASSIST?

The Zimmer iASSIST system is a novel, state-of-the-art knee navigation system employed for total knee replacement surgery. It is a computer-assisted stereotactic surgical instrument system designed to assist surgeons with precise positioning of knee implant components during surgery. The system includes surgical instruments and position sensors to establish proper alignment to knee anatomical markers, allowing the precise orientation and placement of instruments and implants.

A total knee replacement procedure involves replacing the damaged surfaces of the articulating bones with the artificial implant. Most of these implants wear with use. Thus the chance that revision surgery will be needed increases in younger and more active individuals. The life of the implant can be extended by its precise alignment and accurate positioning, which is the purpose of the Zimmer iASSIST knee navigation system for knee replacement.

While Zimmer iASSIST is an effective tool to guide the surgeon and improve the outcome of the procedure, it cannot replace the skills of an experienced surgeon.

Benefits of the Zimmer iASSIST System in Knee Replacement

Some of the benefits of a Zimmer iASSIST knee replacement include:

  • Increased accuracy in sizing and positioning of implant components
  • Improved functional outcome and stability
  • Improved durability of the implant
  • Reduced risk of leg-length discrepancies 
  • Reduced risk of implant wear and dislocation
  • Minimal chance of revision knee replacement
  • Reduced surgery time
  • High patient satisfaction

Knee Anatomy

The knee joint is where the lower femur (thighbone), and upper tibia (shinbone) meet a disk of bone between them called the patella (kneecap).  The patella rests in a groove on the front side of the femoral end. A second bone of the lower leg (fibula) forms a joint with the shinbone. The bones are held together by protective tissue, ligaments, tendons, and muscles. Synovial fluid within the joint aids in the smooth movement of the bones over one another. The meniscus, a soft crescent-shaped cartilaginous structure between the femur and tibia, serves as a cushion and helps absorb shock during motion.

Indications for the Zimmer iASSIST System

Some of the indications for a Zimmer iASSIST knee replacement include:

  • Chronic progressive joint disease
  • Increased pain in the affected knee
  • Trauma to the knee joint
  • Knee instability or a feeling of “giving way” while walking
  • Knee pain that interferes with sleep and other activities of daily living
  • Stiffness in the knee
  • Fracture
  • Failed knee replacement
  • Failed non-surgical treatment

Preparation for the Zimmer iASSIST Knee Replacement Surgery

Preoperative preparation for a Zimmer iASSIST knee replacement involves the following steps:

  • A thorough examination by your doctor is performed to check for any medical issues that need to be addressed prior to surgery.
  • Depending on your medical history, social history, and age, you may need to undergo tests such as blood work and imaging to help detect any abnormalities that could threaten the safety of the procedure.
  • You will be asked if you have allergies to medications, anesthesia, or latex.
  • You should inform your doctor of any medications, vitamins, or supplements that you are taking.
  • You should refrain from medications or supplements such as blood thinners, aspirin, or anti-inflammatory medicines for 1 to 2 weeks prior to surgery.
  • You should refrain from alcohol or tobacco at least a week before and 2 weeks after surgery.
  • You should not consume any solids or liquids at least 8 hours prior to surgery.
  • Arrange for someone to drive you home as you will not be able to drive yourself after surgery.
  • A written consent will be obtained from you after the surgical procedure has been explained in detail.

Procedure for the Zimmer iASSIST Knee Replacement Surgery

The procedure is done under general or regional anesthesia with you appropriately placed on the operating table. The Zimmer iASSIST computer-assisted knee navigation system provides the surgeon with real-time 3-D images of the mapped patient’s knee and the surgical instruments during surgery. The data for the images is provided by infrared sensors fixed to the bones of the knee and the surgical instruments. Their position is tracked by an infrared camera placed above the surgical table connected to the computer. The computer generates real-time images with the help of the Zimmer iASSIST software to guide the surgeon to precisely resurface and cut the bones of the knee and fix the implant precisely and accurately according to the pre-operative surgical plan. Once the surgery is completed, the incision is closed with sutures and covered with a sterile dressing.

Postoperative Care and Instructions

In general, postoperative care instructions and recovery after a Zimmer iASSIST total knee replacement will involve the following:

  • You will be transferred to the recovery area where your nurse will closely observe you for any allergic/anesthetic reactions and monitor your vital signs as you recover.
  • You may notice some pain, swelling, and discomfort at the surgical site. Pain and anti-inflammatory medications are provided as needed.
  • You are advised to keep your leg elevated while resting to prevent swelling and pain.
  • You will be placed on assistive devices such as crutches with instructions on restricted weight-bearing for a specified period of time. You are encouraged to walk with assistance as frequently as possible to prevent blood clots.
  • Keep the surgical site clean and dry. Instructions on surgical site care and bathing will be provided.
  • Refrain from smoking as it can negatively affect the healing process.
  • Eating a healthy diet rich in vitamin D is strongly advised to promote healing and a faster recovery.
  • Refrain from strenuous activities for the first few months and lifting heavy weights for at least 6 months. Gradual increase in activities over a period of time is recommended.
  • An individualized physical therapy protocol will be designed to help strengthen knee muscles and optimize knee function.
  • Most patients are able to resume their normal activities in a month or two after surgery; however, return to sports may take at least 6 months or longer.
  • Refrain from driving until you are fully fit and receive your doctor’s consent.
  • A periodic follow-up appointment will be scheduled to monitor your progress.

Risks and Complications

The Zimmer iASSIST knee replacement is a relatively safe procedure; however, as with any surgery, some risks and complications may occur, such as the following:  

  • Infection
  • Bleeding
  • Postoperative pain
  • Damage to nerves and vessels
  • Thromboembolism or blood clots
  • Anesthetic/allergic reactions
  • Providence
  • Desert Valley Hospital
  • Victor Valley Global Medical Center
  • Barstow Community Hospital
  • Bear Valley Community Hospital
  • California Orthopaedic Association
  • American Association of Hip and Knee Surgeons
  • American Shoulder And Elbow Surgeons
  • American Academy of Orthopaedic Surgeons
  • San Bernardino County Medical Society
  • California Medical Association