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Alignment Systems Step Forward

Any prosthetist will tell you that a successfully fitted prosthesis depends, in part, on achieving the proper alignment. And yet learning to make alignment adjustments through observational gait analysis—not to mention becoming comfortably proficient at it—is no easy task. Not only does it involve classroom training and perhaps years of on-the-job experience, it also relies on keen observation and communication skills. Even the most proficient prosthetists will admit that achieving "perfect" alignment is out of their reach.

"Prior to the 1960s, the worldwide standard for alignment was ‘not bad,'" says John Michael, MEd, CPO, FISPO, FAAOP. In the era where re-alignment meant literally cutting the prosthesis in half and re-gluing it after each and every change, once there were no grossly visible abnormalities, the process was done. If the patient's gait changed over time, there was no practical way to angulate or rotate the socket due to costs of cutting it in half and re-laminating. If the alignment wasn't 'too bad,' amputees just lived with it, despite the discomfort and gait inefficiencies.

"The real meaningful change occurred when Otto Bock introduced the ‘inverted pyramid' endoskeletal design…because for the first time, the alignment of the prosthesis could be incrementally adjusted—in all planes and at all levels—for the lifetime of the prosthesis. Adjustable endoskeletal components proved to have such a clinical advantage that they are now the standard for practice worldwide." But even with this advance, Michael continues, "the standard of care went from 'not bad' to ‘acceptable.'

"The fundamental limitation of current alignment is the difficulty in optimizing characteristics that cannot be seen with the eye, such as torques," he says. Not only must a clinician rely on his or her educated interpretation of a split-second observation, "clinicians rely on patient feedback about how the prosthesis feels as an indirect indicator of when the torques on the residual limb are too high, too abrupt, or too inconsistent." This introduces variations in how accurately the patient communicates what he or she is feeling and how accurately the prosthetist interprets that feedback. "Good prosthetists working with experienced amputees consistently achieve acceptable alignment results," Michael says, "but there is good scientific evidence that a range of alignment styles are acceptable. Optimal alignment remains the holy grail."

Prosthetists and their patients are now one step closer to that ultimate prize, thanks to two companies that are bringing new prosthetic alignment systems to market.

Compas Prosthetic Alignment System

Orthocare Innovations, Oklahoma City, Oklahoma, released its Computerized Prosthetic Alignment System (Compas™) on a limited basis earlier this year. The Compas™ system consists of hardware and software that allows a prosthetist to analyze the dynamic functions of a prosthesis, and a modular, endoskeletal, multiaxial force sensor called the Smart Pyramid™. This component "will take the standard lower-limb prosthesis and make it an intelligent, active, part of the care process," says David Boone, CP, MPH, PhD, chief technology officer at Orthocare Innovations. According to their website, the Smart Pyramid's™ design is based on the industry-standard inverted pyramid and is easily integrated into any new or existing endoskeletal lower-limb prosthesis.

The Compas™ system "provides the kinetic information that one might seek in a gait laboratory, but the measurements can be made without specialized laboratories or technicians, and the information is relayed [via Bluetooth technology] instantaneously and directly to the prosthetist," Boone wrote in the article "The Next Challenge in Prosthetics," Rehab Management, July 2009. The software then provides recommendations to the prosthetist "for adjusting the pyramid screws to optimize sagittal and coronal plane alignment," according to Orthocare Innovation's website.

In other words, the Compas™ system helps the prosthetist see more than he or she can observe.

"Fifty years ago, cardiologists would use a stethoscope to listen to your heart, and they could tell a lot about the function of your heart and blood pressure from that," Boone told The O&P EDGE, "but having the electrocardiogram and the ultrasound of your heart gives them so much more information to properly diagnose what's going on. That's the level of information that we're getting to the prosthetist now.

"What we want to do," Boone continues, "is to make prostheses that adapt to the environment and to the needs of the user rather than having the user adapt to the prosthesis." The Compas™ Smart Pyramid™ creates a prosthesis that has the ability to "inform the user or the prosthetist how it's working. It's a fundamental change to practice and service delivery for amputee care all the way around."

Michael, who had some involvement in the development of the Compas™ system, says he has been impressed by the system from the start. "I was stunned by how closely the Compas™ feedback coincided with my own clinical judgment," he says. "Even more remarkably, the Compas™ data coincided 100 percent with the patient's feedback about when alignment was ‘better than before.' [This is] the first meaningful change in prosthetic alignment since the transition from fixed exoskeletal or endoskeletal systems to adjustable ones," he adds.

According to Carol Sorrels, Orthocare Innovation's director of marketing and communications, the Compas™ system is scheduled for wide market release as this issue of The O&P EDGE goes to press.