Biomedical Engineering Reference
In-Depth Information
7.2. Off the shelf ligaments
7.2.1.
Non-resorbable artificial ligaments
Artificial ligaments became tremendously popular in the early
1990s and were envisioned as the holy grail of ligament
reconstruction, overcoming all limitations encountered in the
autografts. This enthusiasm was abruptly stopped by the poor long-
term stability which often result in catastrophic failures of these
structures. Indeed, several short-to mid-term clinical retrospective
studies revealed that despite appropriate initial behavior and rapid
patient recovery [GLO 88], the vast majority of implanted ligaments
were breaking down and had to be explanted. Most of these newly
developed artificial ligaments were rated as inappropriate for clinical
utilization [PAU 92]. The reasons for this immense failure are
multiple and are related to the biomaterials utilized in the fabrication
of the ligament which were not necessarily adequate for repetitive
loading. Indeed, Paulson
et al
. reported that almost one third of the
patients presented excessive knee laxicity and partial rupture of
the ligament occurred in another third of the patients [PAU 92].
Guidoin
et al.
investigated the explanted failed ligaments and made
some highly interesting observations [GUI 00]. They noticed that the
majority of the ligaments failed at the bony interface which
engendered an acute inflammatory response, a thick disorganized
collagenous scar tissue surrounded the ligament preventing further
tissue infiltration and hence no ligamentization could occur. In
addition, this scar tissue resulted in splitting the fibers of the artificial
ligaments, reducing their mechanical properties.
Most of these prosthetics were soon after removed from the market
or utilized only in very challenging and specific cases. Recent
improvements in the polymer quality and in fiber manufacturing have
enabled the development of a better and safer polyethylene
terephthalate (PET) artificial ligament known under the commercial
name LARS ligament. Several recent short- and mid-term clinical
studies have demonstrated the safety of this prosthetic with only a few
cases of synotivitis or ruptures and LARS is now considered as a
suitable prosthetic for ACL replacement [PAR 13].
