Microprocessor Knee Evolves to Meet Military Personnel Needs

The X3 is the latest generation of microprocessor knees evolved from the X2 and C-Leg.

  • O&P Business News, June 2012

The modern lower extremity prosthesis continues to evolve with the addition of a technologically advanced and military-tailored X3 microprocessor knee. Designed for transfemoral amputees, the first generation X2 by Otto Bock HealthCare was released 2 years ago as a precursor to the X3.

Differences

To meet certain military criteria, the X2 microprocessor knee was built with five sensors that recognize the actions of the user, allowing for a more natural gait and less cognitive demand. The combination of microprocessor sensors, gyroscopes, accelerators and hydraulics create a more stable knee that can intuitively switch from walking mode to running mode for the user. The X3 is essentially the same knee as the X2, only further ruggedized to meet military mission needs.

  Zach T. Harvey, CPO
  Zach T. Harvey

“The C-Leg was a great breakthrough in development, addressing safety, stance stability and swing control compared to previous knees,” Zach T. Harvey, CPO, chief prosthetist, Walter Reed National Military Medical Center (WRNMMC) said. “The Genium, X2, and X3 are examples of knees furthering improvement in terms of adaptation to various terrains, efficiency of gait, and modeling more closely normal biomechanics.”

Assessments

A government grant partially funded Otto Bock to develop a knee that was versatile and durable enough to return some combat injured amputees to active duty, according to Harvey. Compared with the C-Leg, the X3 increases dynamic response, facilitates walking backwards and has increased durability. Tailored to the military user’s needs, the X3 is waterproof up to 1 meter for approximately 10 minutes.

“The initial benefits of the X2 and X3 appear to be the utilization of stance flexion with the optimized physiological gait programming feature,” Harvey told O&P Business News. “In theory, this restores shock absorption and lessens work of the lower back and hip extensor musculature. Standing mode has been reported to reduce the necessity to push back in the socket and support weight acceptance, thus alleviating stress on the lower back and contralateral limb.”

Who gets the X3?

The first 36 X2 units were supplied under the condition that they would be exchanged for the X3, once it was available. The data and wear patterns from the used X2s were assessed by the manufacturer in order to make future improvements. WRNMMC completed a research study in conjunction with Brooke Army Medical Center on the X2 and manuscripts will soon be submitted for publication, according to Harvey.

“Some X3 knees have been exchanged for some of the original X2 knees,” Harvey said. “The advances with the X3 over the X2, such as being waterproof, do not affect the functional performance of the individual. There is no formal study under way regarding X3 knees, although clinical gait evaluations are often being performed in order to optimize gait and alignment.”

The X2, both in terms of functionality and technological advancement, was considered an overwhelming success. Because of the positive feedback, will users want to switch to the X3?

“The necessity of the additional ruggedized features of the X3 versus the X2 would be dependent upon the type of work and conditions under which the work would be performed,” Harvey said. “Individuals who have requirements for the X3 will switch over. When full production of the X3 begins, production of the X2 will cease. The X3 will then become one of the options for our patients. Specific needs will determine if they need an X3, a mechanical knee, a power knee, or some other microprocessor knee unit.”

According to the Army Times, as of early March, the Army is collecting user feedback on the X3. It is currently only available to military personnel. — by Anthony Calabro

For more information:

Tan, Michelle. Army Times. DoD says amputations reached wartime high. Available at: http://www.armytimes.com/news/2012/03/army-amputations-reach-war-time-high-031212w/. Accessed: April 9, 2012.

Disclosure: Harvey had no financial disclosures. The views expressed in this article are those of the authors and do not necessarily reflect the offcial policy or position of the Department of the Navy, Department of the Army, Department of Defense, nor the US government.

Perspective

  • I follow up with every patient I fit with the X3. What really sets the X3 apart is that it is waterproof. That’s the biggest difference. One of my patients was mowing the lawn and he got his knee dirty. He simply hosed it off. Another patient was hiking last weekend and rather than going around the stream without getting wet, he went right through it. Another guy jumped into the pool with his kids. To be able to do that with a microprocessor knee used to be out of the question. It would be the equivalent of jumping into the pool with your cell phone on your hip.

    For the military application, one of the requirements is that they can break into a run from a standstill. This knee allows you to do that. It has a walk-to-run mode. You can take off and land on your knee with one-and-a-half times your body weight and the knee automatically goes into a run mode. This is helpful for recreational uses, but also if a soldier is in a situation where they need to move quickly, they won’t have to wait for the knee.

    Training can be unnerving the first few times because you are going to jump out onto your leg. The knee will be bent. You are going to have trust the knee to be there and support you when you hit that stride. We start patients out with the parallel bars and it doesn’t take long to get the hang of it. We teach them how to run, even though the X3 wouldn’t be a primary running leg. They can run and perform all of their duties with the X3.

    • John R. Fergason,, CPO
    • Chief prosthetist, Center for the Intrepid, San Antonio, Texas

Comments

Healio is intended for health care provider use and all comments will be posted at the discretion of the editors. We reserve the right not to post any comments with unsolicited information about medical devices or other products. At no time will Healio be used for medical advice to patients.