The menisci and their insertions into bone (entheses) represent
a functional unit. Thanks to their firm
entheses, the menisci are able to distribute loads and therefore
reduce the stresses on the tibia, a function
which is regarded essential for cartilage protection and prevention
of osteoarthrosis. The tissue of the
hypocellular meniscal body consists mainly of water and a dense
elaborate type I collagen network with a
predominantly circumferential alignment. The content of different
collagens, proteoglycans and
nonproteoglycan proteins shows significant regional variations
probably reflecting functional adaptation.
The meniscal horns are attached via meniscal insertional ligaments
mainly to tibial bone. At the enthesis, the
fibres of the insertional ligaments attach to bone via uncalcified
and calcified fibrocartilages. This anatomical
configuration of gradual transition from soft to hard tissue, which
is identical to other ligament entheses, is
certainly essential for normal mechanical function and probably
protects this vulnerable transition between 2
biomechanically different tissues from failure. Clinical treatment
of meniscal tears needs to be based on these
special anatomical and functional characteristics. Partial meniscectomy
will preserve some of the load
distribution function of the meniscus only when the meniscal body
enthesis entity is preserved. Repair of
peripheral longitudinal tears will heal and probably preserve the
load distribution function of the meniscus,
whereas radial tears through the whole meniscal periphery or more
central and complex tears may be
induced to heal, but probably do not preserve the load distribution
function. There is no proof that
replacement of the meniscus with an allograft can reestablish some of
the important meniscal functions, and
thereby prevent or reduce the development of osteoarthrosis which is
common after meniscectomy. After
implantation, major problems are the remodelling of the graft to
inferior structural, biochemical and
mechanical properties and its insufficient fixation to bone which
fails to duplicate a normal anatomical
configuration and therefore a functional meniscal enthesis.
