Previously there were two groups of sub-ischial socket systems. On the one hand the systems that are stabilised via muscular blocking, on the other hand the systems that are stabilised via a major reduction of the stump volume or pressure using several truss pads.
Here, the VPS System adopts a completely new approach: it makes such effective use of the inactive zones between the remaining muscle groups that it is suitable even for users with low mobility. The VPS System thus increases the use potential of the sub-ischial socket and simultaneously extends the patient spectrum. It is suitable for all users who satisfy the following preconditions:
With upper-leg stumps the muscles can be sub-divided into adductive, inflectional and extending groups. Very little muscle activity is discernible between these "resting points" - irrespective of which direction of movement is selected.
The "Dimplemat" device developed by
Vogel Orthopädie Technik enables reproducible adjustment of the resting points.
This does not lead to a reduction in volume, but rather to a volume
shift whose core stabilises itself independently of the direction of movement.
This column, situated between the main muscle groups, is indirectly stabilised
further by the muscle groups.
A usable cast can only be achieved using Dimplemat, as the points previously identified on the stump cannot be transferred, irrespective of the casting technique chosen. The Dimplemat enables technicians to adjust and document the points in reproducible manner.
The prosthesis socket is arranged frontally and sagitally on a 50%/50% basis in accordance with the established structural guidelines.
The optical alignment of the classic socket systems can be dispensed with. Patients therefore align themselves strongly to the foot position and the lateral arrangement when attaching the prosthesis. They require a little time to gain a feel for when the prosthesis is correctly fitted. All further parameters such as height, flexion position (Trippe test) etc. correspond to those of other socket systems.
In addition to the known parameters, considered here in the gait cycle, account must be taken of the fact that a shifting of the "resting points" as well as a lack of free space have a significant influence on rotations, in particular following toe detachment. In the event of minor deficiencies in the gait cycle, technicians should check whether the prosthesis has been fitted in the correct position.