Page 102 - REV T-I JOURNAL INTERIOR ISSUU 18 2-3
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178 KAHLE ET AL.
2. Adjustable TFA Interface. The Infinite Socket™ six study conditions across three repeated indepen-
is a custom-molded four-strut design combined with dent utilization periods, each followed by an outcome
a textile brim and tensioner to contain and control assessment. The study design controlled for all pros-
the pelvis and femur and soft tissues across a varying thetic variables (Table 1), as the subject utilized his
volume. Adjustments can be made by both clinicians usual prosthetic components with only the exception
and patients to manage long-term and daily fluctua- of the socket (independent variable) throughout the
tions. The pivoting and sliding connection between study. The order of testing was randomized using an
the struts and base provides additional flexibility in offsite computer randomized number generator to
adjustability as well as shock absorption and energy improve methodological quality and minimize bias
response. The dynamic frame of the Infinite socket™ risk. Further, raters and the study statistician were
has a textile interface that is reportedly low in friction, blinded to the independent variables. Data collec-
anti-microbial, durable, and washable. The Infinite tion was completed over three sequential days. Each
Socket™ achieves control and pressure distribution data collection period began at the same time of day.
through multiple custom components, which include The subject was instructed to maintain fluid, salt
an ischial seat, proximal brim, four struts, and a flex- intake, and diet over the study period. Weight was
ible inner distal cup. recorded each day, in addition to RL circumference
measurements, to help ensure volume consistency.
Study Design A ten-minute rest period between conditions was
To simulate the same volume fluctuations an ampu- provided between tests to mitigate confounding from
tee would experience, three conditions were tested. fatigue. Blood pressure and heart rate were moni-
First, to establish a baseline (BASE), the subject was tored before each test to ensure normalization prior
casted over his Otto Bock 6Y87 3D TF pin-locking to re-testing.
liner (Otto Bock Healthcare, Duderstadt, Germany)
and a five-ply sock. Both the SOC and Infinite™ sock- Outcome Measures
ets were fabricated from this cast. The sockets were Physical performance measures were selected to
then fit and adjusted to this configuration to ensure assess functional capability and safety differences
an equal baseline. Second, to simulate volume loss between the two socket conditions. For instance,
(VLOSS), the five-ply sock was removed from the speed of movement and walking are valuable clinical
RL and liner, and then the subject was tested in this tests of functionality and provide good identification
condition. This constituted a 2 cm circumferential of multiple-falls risk (15-17). Slower gait has also been
volume change (VLOSS) less than the BASE circum- shown to be an indication of fall risk (18). Thus, the
ference. Third, to simulate volume gain (VGAIN), the following tests were selected:
five-ply sock plus an eight-ply sock was added to the
RL and liner for a total of 13-ply. This constituted a 2 a. L-Test: a short walking test with transitional
cm circumferential volume change (VGAIN) more movements and multiple turns
than the BASE circumference. b. Four Square Step Test (4SST): a brief assess-
An experimental case study design was utilized for ment of multi-directional stepping (15)
this project. An independent researcher randomized c. Two-Minute Walk Test (2MWT): a test to pro-
Table 1. Table of Variables
Table 1. Table of Variables
Independent Dependent Controlled
SOC- IRC TFA Subjective Response (i.e., Accommodation
Interface Comfort, Pain) Clinical Schedule
LIM -Adjustable TFA Mobility, i.e., 4SST Environment
Interface Function, i.e., AMP Knee, Foot, Liner,
Gait Speed, L-Test, 2MWT Suspension
