This was a 42-yr old male who had his left lower limb amputated 5 yr prior as a result of traumatic injury. His limb was revised 16 mo after his initial amputation because of complications from surgical staples within his residuum. His residual limb length was 16 cm from the mid-patellar-tendon to distal end and cylindrical in shape with a fair amount of hair. He was 180 cm in height, 88 kg in mass, and a K-4 level  ambulator. His prosthesis was a total contact socket design with an elevated vacuum unit, and a dynamic response foot (Renegade Freedom Foot, Freedom Innovations). He used elevated vacuum because of prior diurnal residual limb volume change problems using a Pelite  liner, and because he had an interest in trying elevated vacuum suspension. One year prior to our bioimpedance testing he switched from a manual elevated vacuum system (Harmony, Otto Bock) to an electronic system (eVAC, Smith Global). In bioimpedance testing, he was tested with his electronic system. He had a history of blister problems when he set the vacuum pressure at the highest setting, 15 psi (104 kPa), instead of his usual setting, 10 psi (69 kPa). These pressure settings were the values labeled on the elevated vacuum unit; we did not measure the actual pressures. It is thus unknown if the stated pressure levels were achieved in the present study. The subject typically wore his prosthesis for 16 h/day, and wore a 5-ply and 3-ply sock outside of the liner. He did not add or remove socks during the day.
These subjects were short-term users (3-4 wk) of the manual (Harmony) system prior to bioimpedance testing. For each of the three subjects, a new socket was made to use with the elevated vacuum prosthesis. No locking pin was used with the elevated vacuum socket. All had residual limbs with prominent bony structures and little redundant soft tissue.
This male subject was 61 yr of age and had his amputation 5 yr prior as a result of traumatic injury. His 17 cm length residual limb was conical in shape with a fair amount of hair and little soft tissue. He was 175 cm tall and 73 kg in mass, and a K-4 level ambulator. He was healthy and did not take any medications, though he used to be a smoker (for 20 yr; stopped smoking more than 5 yr ago) and his blood pressure was on the high end of normal. His regular prosthesis was a patellar tendon bearing (PTB) endoskeletal prosthesis with a gel liner and lock-and-pin suspension, and his prosthesis was equipped with a dynamic response foot (Luxon Max, Otto Bock). He wore his prosthesis for at least 16 h/day. He typically did not add socks to compensate for limb volume change except on days when he was very active. He was a good candidate for elevated vacuum because of his high level of activity, desire for optimal proprioception, and need for fewer sock changes to eliminate pistoning during active days. Prior to bioimpedance testing he was fitted with a new socket equipped with a P2 Harmony vacuum unit, and Seattle Lightfoot (TrueLife). He used this prosthesis exclusively for the 3 wk prior to bioimpedance testing.