# Prepopulated Expressions
The essence of this approach is that the user is presented with a clinical phrase representing a specific clinical meaning, and in the backend of the system, this clinical phrase is associated with a postcoordinated expression (instead of a precoordinated concept).
In the example shown in the image below, the user interface includes a list of phrases such as “Open fracture of left radius”, and “Open fracture of right radius”. Some of these phrases may be associated with precoordinated content (either via mapping or the released SNOMED CT descriptions), while other phrases may be associated with postcoordinated expressions. In this example, the phrase “Open fracture of left radius” and “Open fracture of left ulna” is associated with postcoordinated expressions.
Options displayed in a user interface may be associated with a postcoordinated expression
This approach requires the expressions to be created and mapped to an interface term by a SNOMED CT implementer. This occurs as part of the terminology binding process in the design stage of the implementation. Different approaches to the creation of the expressions exist and depend on the tools available. These approaches are described in the following pages.
Using postcoordinated expressions for items in a prepopulated list, or predefined values in a UI, each expression is associated with one field on the user interface. For precoordinated concepts, the best practice is to record the concept identifier as the code, and the term that was displayed or selected by the user as the original text.
The recommended approach to the storage of predefined postcoodinated expressions is similar to the storage of precoordinated concepts. This means that the display term used for the expression should be recorded in the health record, but the ‘code’ should either be the terse form of the full expression (i.e. the expression with the terms and spaces removed), or the unique identifier associated with the expression when this was added to the expression repository.
**Terminology services**
Enabling prepopulated expressions in the EHR requires the EHR to access expressions already created in the expression repository.\
For this purpose, the following services may be required:
* [Lookup Expression](https://github.com/SNOMED-Documents/snomed-postcoordination-guide/blob/main/expressions-in-the-ehr/entering-expressions-in-an-ehr/broken-reference/README.md)
* [Search Expression](https://github.com/SNOMED-Documents/snomed-postcoordination-guide/blob/main/expressions-in-the-ehr/entering-expressions-in-an-ehr/broken-reference/README.md)
* [Get Display Term](https://github.com/SNOMED-Documents/snomed-postcoordination-guide/blob/main/expressions-in-the-ehr/entering-expressions-in-an-ehr/broken-reference/README.md)
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