Tendons and ligame
Tendons and ligaments
Ligaments are the fairly elastic bands of tissue that join bones together, tendons are made of similar tissue. The most commonly replaced ligaments are those of knee. (19)Manmade tendons have made of woven and braided porous structure coated with silicon, but nonwoven fabrics are not suitable as ligament prosthesis because of their lack of strength, woven and knitted structures are used as artificial ligaments. (5) Braiding a carbon fiber core and a polyester sleeve have produced a material for replacing damaged ligaments (20) as well as polyester and carbon fibers were used in twisted, knitted and narrow- woven constructions (21) but braided fabrics with a stress strain behavior similar to a natural tendons or ligament are the most suitable structure where braided polypropylene implant usually consists of several strands that are braided into tape –like structure, A braided carbon fiber implant is typically made up of thirty –two strands of 3.000 fiber each .
The requirements for ligament and tendon implants are both biological (biocompatibility – long – term stability ,and supporting tissue proliferation and bio-mechanical (physiological progressive stress strain), bio-absorbable are preferable for manufacturing of ligaments and tendon .(4) Synthetic material can not match the fatigue resistance of natural tissue with its ability to regenerate itself so a graft should encourage the ingrowth of new collagen to form a new tendon or ligament a successful graft must match the mechanical properties of the original ligament or tendon as
closely as possible and must induce adverse tissue reactions .(5) Finally at the present time, no material has been shown to be ideal tendon where founding problem including the abrasion of the prostheses at the point of entry , leading both to malfunction and excessive tissue response to the debris and the creep of the polymer that radically alters the ability to replicate the natural mechanical response to loads, thereby leading to instability