Jim Liston, CP, FAAOP, and owner of Specialized Prosthetics and Orthotics, understands that providing a proper-fitting socket is the key to patient mobility and comfort.

With more than 18 years experience and recognition as a Fellow of the American Academy of Orthotists and Prosthetists, Jim has the commitment, expertise and know-how to provide the specific socket, liner and leg that best suits his patients' needs and expectations.

More importantly, Jim knows that what works for some, may not work for all.

As a conscientious practitioner, Jim researches componentry and discusses its feasibility with each patient. He finds that many of his transtibial patients achieve the best fit and comfort by using the Otto Bock Harmony® System with VASS™ (Vacuum Assisted Socket System) technology.

Not every practitioner is certified to fit Harmony. Jim was one of the first practitioners in the country to embrace the new technology when it was first introduced in 2002 by TEC Interface Systems. He became certified in its application by TEC, and certified again by Otto Bock after they purchased TEC. He has assisted both TEC and Otto Bock in teaching other clinicians how to properly fit the system.

As amputees know, the residual limb doesn't stay the same size all day when wearing a prosthesis. Studies have shown that a patient can lose between 6 to 12 percent of the residual limb's total volume through perspiration, edema and other fluid movement. This results in the prosthesis becoming loose and causing skin irritation, which may lead to uncomfortable and unstable movement. It's even more dangerous for diabetic patients who have less sensation and may not feel the slippage; the result can be serious infections. Reasons for volume fluctuation lie within the socket/residual limb interface and in the biomechanical functions of the gait or walking cycle.

During normal gait, legs are in stance phase about 60 percent of the time, and in swing phase about 40 percent. Because the pressure of the socket on the residual limb during the longer stance phase can "press" or carry fluid out of the residual limb, and because the swing phase is shorter, more fluid can flow out than flow back in, therefore decreasing limb volume.

Typically, patients adjust to the changes by adding layers of prosthetic socks over the residual limb, but it is not always convenient to remove the prosthesis to add or change socks. Also, socks can distort the fit of the socket, resulting in less control of the prosthesis.

The Harmony System addresses this issue by reducing variations in limb volume.

Components of the system include: a total surface weight-bearing socket, which helps distribute pressure more evenly around the residual limb to improve fit and prevent pressure peaks; a mechanical pump that draws air out of the system during normal walking; a sealing sleeve that makes an air-tight seal with the user's liner and body; an adjustable shock absorber; and a torsion adapter to increase walking comfort and relieve the strain on joints and the spine.

The components work together to create an elevated vacuum environment. The result for the user is that the liner is drawn completely into the socket for a more intimate fit, allowing fluids to be more easily drawn back into the leg during each swing phase. This increases healthy fluid flow and maintains consistent limb volume to reduce forces on the limb.

Studies have shown the Harmony System reduces tissue elongation and displacement and also helps users achieve a more symmetrical gait pattern by allowing them to spend almost as much time on their affected side as on their contralateral side.

The improved linkage also increases proprioception, the sensory nerve ending that supplies the brain information concerning movement and position of the body. Through the Harmony System and his expert fitting skills, Jim provides his patients with a comfortable socket, enabling them to achieve their mobility goals.