Is it just because you want to know what the term means, or are you actually translating it? If translating, are you doing it for someone who just needs a vague idea of the meaning? If you are trying to provide a "proper" translation intended to be read by people who work in the fields of orthopaedics and prosthetics, then there is no substitute for familiarising yourself with the jargon which these professionals use, and to pick the most appropriate term. It is often quite important to make exactly the right choice here, because there may be important differences between terms which to a lay person (i.e. a non-medic) sound so similar that we're apt to think they're synonyms.
In the absence of any medical specialists who might be lurking here, all I can say is that your guess is as good as ours. The following excerpt from the link you provided certainly suggests that this is the prosthetic equivalent of a bootstrap.
Ein breiter Einzugsriemen erleichtert wesentlich das Anziehen im Sitzen. Deshalb ist es besonders für geriatrische Patienten und Patienten mit geringem Mobilitätsgrad geeignet.
That said, it might not be just for pulling it into position, but also to hold it there, by attaching it to some kind of anchoring contraption.