Described herein are injectable alloplastic implant compositions that are particularly useful for soft tissue defect augmentation. The compositions include microparticles, such as polymethylmethacrylate particles, and collagen as a suspending agent, wherein the collagen contains a reduced amount of low molecular weight gelatine compared to high molecular weight collagen. By controlling the molecular weight of the collagen in the compositions, the injectability, stability, and antigenicity of the alloplastic implant compositions can be improved.
