The fracture codes have extra 7th digit possibilities. You need to look at what applies for whatever type of fracture it was. For example, if a new patient has a nonunion fracture of the forearm, S52.-, consider which of the following 7th digits applies:
K subsequent encounter for closed fracture with nonunion
M subsequent encounter for open fracture type I or II with nonunion
N subsequent encounter for open fracture type IIIA, IIIB or IIIC with nonunion