The present invention relates to a method for preparing a chitosan matrix having good mechanical properties comprising the steps of- a) preparing a solution of chitosan,- b) pouring the solution of a) into a mould in order to form a layer,- c) lyophilizing the layer of b) in order to obtain a matrix of chitosan,- d) sterilizing the matrix obtained in c) by water vapor treatment.The invention also relates to the matrices obtained and to surgical implants comprising such matrices.The invention further relates to a method for increasing the suture retention strength of a chitosan matrix obtained by lyophilization of a chitosan solution, and to a method for for decreasing the solubilization rate in hydrochloric acid of a chitosan matrix obtained by lyophilization of a chitosan solution, comprising the step of sterilizing said matrix by a water vapor treatment.
