The invention relates to a method for producing an implant which contains a composite powder comprising microstructured particles, obtainable by a method in which large polymer particles are bonded to small spherical calcium carbonate particles. Said calcium carbonate particles can be obtained by a method with the following steps: a) providing a calcium hydroxide suspension, b) introducing carbon dioxide or a carbon dioxide-containing gas mixture into the suspension from step a), and c) separating the calcium carbonate particles formed, while adding 0.3 wt.-% to 0.7 wt.-% of at least one amino trialkylene phosphonic acid.