16973
While there is strong evidence that bisphosphonates prevent certain types of osteoporotic fractures , there are concerns that these medications may be associated with rare atypical femoral fractures ( AFF ) .
 Chemical: bisphosphonates
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: bisphosphonates