Two transtibial prostheses () were manufactured for each subject. Two different suspension systems were used: Seal-In X5 liner with valve (Icelock Expulsion Valve 551, Össur) and Dermo liner with shuttle lock (Icelock Clutch 4H 214, Össur). All prosthetic feet were Flex-Foot Talux (Össur) [16,18].
Prosthetic gel liners are often prescribed for persons with lower-limb amputations to make the prosthetic socket more comfortable. However, their effects on residual limb pressures and gait characteristics have not been thoroughly explored. This study investigated the effects of gel liner thickness on peak socket pressures and gait patterns of persons with unilateral transtibial amputations. Pressure and quantitative gait data were acquired while subjects walked on liners of two different uniform thicknesses. Fibular head peak pressures were reduced ( = 0.04) with the thicker liner by an average of 26 +/– 21%, while the vertical ground reaction force (GRF) loading peak increased 3 +/– 3% ( = 0.02). Most subjects perceived increased comfort within the prosthetic socket with the thicker liner, which may be associated with the reduced fibular head peak pressures. Additionally, while the thicker liner presumably increased comfort by providing a more compliant limb-socket interface, the higher compliance may have reduced force and vibration feedback to the residual limb and contributed to the larger vertical GRF loading peaks. We conclude that determining optimal gel liner thickness for a particular individual will require further investigations to better identify and understand the compromises that occur between user perception, residual-limb pressure distribution, and gait biomechanics.
Transtibial prothesis (WIP) - 3D CAD model - GrabCAD
Based on the literature, the pistoning is correlated with the prosthetic suspension system and fit . Thus, both clinicians and researchers should be able to determine the quality of suspension and prevent the negative effects of pistoning (such as gait deviation, skin breakdown, and discomfort) by pistoning measurement [13–22].
Below-Knee Prosthetics – Hanger Clinic
This includes controlled knee flexion after heel strike, smooth rollover with limited recurvatum (hyperextension), and heel off prior to initial contact on the normal (other) foot.
In the sagittal plane, proper anteroposterior (AP) positioning of the socket with regard to the foot will result in even weight distribution between the heel and toe portion of the foot statically.
For a trans-tibial prosthesis, a plumb line (gravitational line 90° to the ground) should fall through the center of socket (it may be easier to mark this with an erasable marker), slightly anterior to where the ankle joint axis would be, and through the weight bearing area of the foot between the middle of the weight bearing surface of the heel, and the metatarsal heads (shown in Figures 1 and 2).
Steps in Making an Transfemoral Prosthesis | Elevated …
more uniform distribution of pressure over the residual limbs of unilateral, transtibial amputees wearing TSB sockets during walking compared with the pressure distribution created with a thinner gel liner. Specifically, the thicker gel liner was expected to reduce peak pressures over those areas of the anatomy that are regarded as sustaining higher pressures during load-bearing through the prosthesis. As a result of the increased compliance between the prosthesis user and the prosthesis, we anticipated that shock absorption would be improved, resulting in lower peak GRF magnitudes during weight acceptance. Analysis of the group data indicated that a statistically significant reduction in peak pressure occurred with the 9 mm gel liner at the sFH only (), one of the three measurement sites for which pressure data were successfully obtained. In a previous study that measured sock-socket pressures within PTB sockets as subjects walked with various combinations of prosthetic feet and pylons, the investigators reported that changing prosthetic components within a single testing session altered the interface stress by an average of 14.5 percent . Therefore, the 26 percent decrease in mean peak pressure over the sFH that was observed in this current study supports the assertion that the thickness of a prosthetic gel liner can reduce pressures over bony prominences on the residual limb during loading, as was suggested by previous investigations [15,20].
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pressure was measured was limited in this study. Pressure data were acquired at only three specific locations on the subjects– residual limbs because of problems that developed with two other sensor arrays. To provide more compelling evidence that a thicker liner is able to distribute pressure more uniformly over the residual limb compared with a thinner liner, researchers should implement experimental protocols that incorporate pressure sensors over more sites on the residual limb, including regions with soft tissues and bony landmarks. Additionally, the accommodation period given for the experimental prosthesis may not have been sufficient to effect significant changes in gait parameters, particularly in the BRL subjects who were not as accustomed to the increased compliance at the limb-socket interface. Subjects were asked to wear the experimental prosthesis as much as possible during the 2-week accommodation period, but the extent of each subjects– fluency with the prosthesis was not quantified. While a 2-week accommodation period is fairly common in studies of prosthetic components for unilateral transtibial amputees, a minimum recommended length of time for accommodation with these gel liners is unknown. Had a longer accommodation period been part of this protocol, the subjects may have become better accustomed to the increased compliance at the residual limb-prosthetic socket interface and their gait biomechanics may have changed to better reflect the benefit they derived from the shock-absorbing characteristics of the liner.