Use of porous biodegradable polymer implants in meniscus reconstruction. 1) Preparation of porous biodegradable polyurethanes for the reconstruction of meniscus lesions

Abstract

Porous biodegradable poly(urethanes) for reconstruci~ng menisci have been prepared using two different combinations of techniques: freeze-drying/salt-leaching and in-situ polymerization/salt-leaching. Using these methods, homogenous porous materials with a controllable and reproducible morphology can be prepared. The materials were made of three different poly(urethanes): a methylenediphenyldiisocyanatebased polyurethane, a lysine diisocyanate-based poly(urethane), and a poly(e-caprolactone)-based poly(urethane). The compressive stress-strain behavior of the Estane foams was determined. Foams made by the freeze-drying/salt-leaching technique implanted in dogs showed healing and good ingrowth of fibrocartilaginous tissue.

Preparation of a polyurethane scaffold for tissue engineering made by a combination of salt leaching and freeze-drying of dioxane

“…It has been found that optimal ingrowth of fibrocartilagenous tissue takes place if the pore size is in the range of 200-300 µm [18]. Therefore the scaffold should contain a maximal number of pores in that range, consequently as much sugar as possible should be mixed with the polymer solution.…”

“…There the foams had a similar size of the large pores in combination with a major amount of micro pores that could not be infiltrated with cells. Moreover, the interconnectivity was determined by the size and number of the micro pores [18]. A decrease in small pores in combination with a constant overall porosity and an increase in interconnectivity will increase the volume suitable for cell ingrowth and cell viability.…”

“…De Groot demonstrated that interconnectivity can also be obtained by mixing the polymer dioxane solution with c-hexane/water and a porogen, thereby introducing liquidliquid phase separation during cooling [18]. The connection between the micro pores and the macropores could be opened by applying this phase separation process.…”

“…The problems with these types of implant were e.g., fragmentation of non-resorbable materials, which may induce macrophage or giant cell reactions [14], synovial irritation, cartilage softening [17]. Degradable scaffolds lack the combination of satisfying mechanical properties and a high interconnectivity [18]. It has been found that a fast infiltration of fibrous tissue into the polymer scaffold depends on the presence of interconnected macropores [19][20][21].…”

“…An accurate control over the interconnectivity independent of the pore size and overall porosity is thus necessary. De Groot et al [18] studied foams and foam preparation methods based on Estane where the interconnectivity between the pores originating from the porogen was introduced by the crystallization of the solvent. However, this leads to systems with a high content of so-called micro pores.…”