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Zimmer, Inc.

Zimmer® iASSIST™ Knee - The Personalized Guidance System™

Zimmer iASSIST Knee - Surgical Assistance for Total Knee Arthroplasty

Zimmer iASSIST Knee is an advanced surgical guidance system engineered to improve the accuracy and alignment of total knee replacement surgery.  Zimmer iASSIST Knee helps to assist the surgeon in precisely aligning knee implants to each patient’s unique anatomy, providing a personalized fit and a truly tailored total knee replacement.

iASSIST Knee has synthesized the latest guidance technologies into a palm-size electronic display to help surgeons align and validate implant positioning during a total knee replacement surgery as shown in Zimmer  iASSIST Knee Demonstration for Total Knee Arthroplasty video on ZimmerTV.

Zimmer iASSIST Knee is engineered to help orthopaedic surgeons achieve reproducible accuracy and alignment in total knee replacement, and is fully compatible with Zimmer's primary knee implants: Zimmer NexGen®, Zimmer Natural-Knee® and Zimmer Persona®.

Zimmer iASSIST Knee System seamlessly integrates into the operation by requiring no complex imaging equipment or additional surgical incisions.  Combining iASSIST Knee with Zimmer’s full range of knee replacement and instrument options helps surgeons deliver the best possible fit for patients undergoing total knee replacement.

  • No capital equipment purchase needed
  • No pre-operative imaging
  • No additional incision or external pin fixation

The Personalized Intraoperative Guidance Device System for Knee Surgery

Zimmer iASSIST Knee supports more personalized and streamlined knee replacement procedures through a simple, disposable intraoperative device. Zimmer iASSIST Knee is engineered to help orthopaedic surgeons achieve reproducible accuracy and alignment, to help deliver the best possible fit during total knee replacement surgery. View the complete Zimmer iASSIST Knee Surgical Technique on ZimmerTV

iASSIST Knee Improves on Previous Navigational Technology

The main component of the iASSIST Knee is a disposable device that can be used as needed; no capital equipment investment by the hospital is necessary.

  • Designed to intuitively integrate with surgeons’ conventional instrumentation for total knee arthroplasty
  • No pre-operative imaging
  • No wait time for the patient and the hospital
  • Less invasive procedure to the patient

Unlike prior navigation technology or robotic surgery, the iASSIST Knee system saves surgeons more time, hospitals additional costs by eliminating pre-operative imaging, and is less invasive for the patient with the absence of additional incision for pins fixation.

More importantly, the iASSIST Knee has the ability to validate bony cuts intra-operatively, which allow the surgeon to target a greater level of accuracy.

Dr. Camarata describes the system with these words: “[When using iASSIST Knee] the surgeon can be confident that there will be no outliers or bony cuts that are out of alignment. I have never used traditional navigation, yet I was able to adapt this technology immediately for my patients with no down time”. 1

The Zimmer Knee Advantage

Currently, more than one in every four knee replacements in the U.S. is a Zimmer implant, making Zimmer the number one knee replacement company in the country.2

More than 7,000 surgeons use Zimmer products in the U.S.; making Zimmer the most trusted knee company in the world.3

Zimmer invests more than $100 million each year in clinical studies and patient safety and quality programs to ensure that our implant systems are the best available anywhere in the world.4

To get more information on Zimmer iASSIST Knee technology, contact your local Zimmer representative 

Surgical Techniques


1. ICJR Staff, March 2014, New Technology Brings Intelligence, Accuracy to TKA Instrumentation.

2. Each year, nearly 1 in every 4 knee replacements performed in the United States utilizes a NexGen Knee product. Zimmer’s NexGen System is the world’s most trusted, widely used and clinically proven knee system with more than four million implanted worldwide since 1994 and 1.45 million implanted in the United States.

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3. More than 7,000 surgeons use Zimmer products in the U.S. To find a doctor for your knee replacement surgery, call 1-800-HIP-KNEE (447-5633) or Zimmer Proven Knee Info

4. Zimmer invests more than $100 million each year in clinical studies and patient safety and quality programs to ensure that our implant systems are the best available anywhere in the world.

Zimmer Facts

Data on file.

The Intelligent Instrument for Total Knee Replacement

  • The Zimmer iASSIST Knee is the latest intelligent instrument to be introduced to computer assisted surgery (CAS), engineered to help orthopaedic surgeons achieve repeatable accuracy and alignment in total knee arthroplasty. 
  • Small electronic positioning sensors are placed within the surgical field, to assist orthopaedic surgeons in achieving proper limb and component alignment of the main femoral and tibial bone cuts during total knee replacement surgery.
  • iASSIST Knee consists of small disposable electronic sensors, which employ accelerometers and gyroscopes to provide accurate alignment information to the surgeon, directly at the surgical site.
  • Instantaneous alignment validation information is wirelessly transmitted to a simple electronic display for the surgeon. The compact display of the iASSIST Knee has been designed to help guide—not distract the surgeon during total knee replacement surgery.
  • Compatible with Zimmer's primary knee implants:  NexGen™, Natural-Knee™ and Persona™
  • The iASSIST Knee features simple and intuitive instrumentation based on conventional instruments used in total knee replacement.

Personalized Guidance System for Total Knee Arthroplasty

Zimmer strives to design the most comprehensive surgical guidance system that is anatomically accurate using the most advanced technologies, and personalized to address the unique needs of each patient.

iASSIST Knee is a perfect blend of intelligent design and engineering excellence, allowing the surgeon to tailor the configuration to accommodate for preferences intra-operatively, for greater accuracy, efficiency and time saving benefits.

  • More intuitive instruments assist to improve accuracy and reduce early revisions, while driving efficiencies.
  • Better outcomes result from personalization; lowering costs through pre-operative planning and patient customization.

The Personalized Guidance System for Total Knee Replacement Surgery

Zimmer’s iASSIST Knee is a guidance system to assist the surgeon in customizing the positioning of knee replacement system components intra-operatively. It involves surgical instruments and position sensors to determine alignment axes in relation to anatomical landmarks and to precisely position alignment instruments and implant components relative to these axes.

Advanced Engineering Technology that is Intuitive and Accurate

  • iASSIST represents a revolutionary next step in intelligent surgical guidance, engineered to offer orthopaedic surgeons intuitive and accurate intraoperative feedback and alignment validation.
  • It has been reported that the use of guidance technology such as iASSIST Knee in total knee replacement helps provide more accurate alignment of the joint replacement, potentially enhancing overall function and the lifetime of the implant. By offering precise intra-operative feedback and alignment validation, the iASSIST Knee may contribute to improved clinical outcomes and increased implant longevity in patients.1
  • iASSIST eliminates the hassles and significant expense associated with current robotics and navigation systems. Current technologies utilize optical-tracking, which requires a clear line-of-sight into the surgical field, as well as complex additional equipment in the operating room, such as bulky external computer monitors.2
  • iASSIST does not require pins, additional incisions, or additional pre-operative imaging or logistic management.3

System Controller Specifications

  • Weight:  About 1.9 kg
  • Dimensions:  273.5mmx207.5mmx36mm (irregular)
  • Power:  100-240 VA, 47-63 Hz, 1.22 -0.68 A
  • Operating conditions: 0°C to 50°X
  • Transport/storage condition: 20°C to 70°C
  • User devices:  Touch screen, 2D barcode scanner

Wireless Communications

The system Controller Computer (20-80011-070-01) contains RF transmitter with the following characteristics:

  • Transmission frequency:  2.405 GHZ to 2.48 GHz
  • Modulation:  Offset Quadrature Phase-Shift Keying (OQPSK)
  • Coding:  Direct Sequence Spread Spectrum (DSSS)
  • Transmission bandwidth:  2MHz
  • Effective isotropic radiated power:  4dBm

Surgical Technique


1. SIKORSKI JM, CHAUHAN S (2003) Computer-Assisted Orthopaedic Surgery: Do we need CAOS? JBJS 85-B:319-23.

2. HAAKER RG, STOCKHEIM M, KAMP M, PROFF G, BREITENFELDER J & OTTERSBACH A (2005) Computer-assisted navigation increases precision of component placement in total knee arthroplasty, Clinical Orthopedics, 433:152-9.

3. NOBLE PC, SUGANO N, JOHNSTON JD, THOMPSON MT, CONDITT MA, ENGH CA Sr, MATHIS KB (2003) Computer Simulation: How can it help the surgeon optimize implant position? CORR, (417):242-52.