Rasch Modelling with R: Is there a possibility to estimate only person parameters from given item difficulties

Question

So I am doing some Rasch Modelling (simple binary Models and PCM Models) with the eRm-package in R. In the future we may want to use the results to produce feedback for individual experimentees, but (at first) we do not want to recalculate the complete model every time. Thus, I am looking for a possibility to estimate only the person parameters with given item paramters. Has anybody experience with this and maybe even knows a function, preferably from the eRm-package which does the job? I really do not want to implement the whole likelihood-method all by myself.