In Bloskas v. Murray, 646 P.2d 907 (Colo. 1982), the court found that evidence of a doctor's habit or custom of routinely advising patients about to undergo hip or knee replacement surgery of the risks of infection and loosening of the artificial joint was admissible as circumstantial evidence to show that he had given the same advice to the plaintiff, even though he had no independent recollection of ever so advising the plaintiff.