From LOINC’s perspective, I think it is probably your choice. (Not sure what HL7 SDWG would say). The LOINC code is meant to identify the expected information contents of that item. LOINC’s definition of HPI (which could be improved) is based on the general use of the phrase in medicine…which employs a broad definition of “illness” that would include trauma. In the context of trauma, an HPI might include things like the mechanism of injury, timing of the injury, situational details (entrapment, airbag deployment, etc), other prehospital assessments,etc (per The trauma manual: trauma and acute care surgery). So, I think it would be reasonable to use the HPI template if it fits your needs. The advantage of using an injury-specific code would be that you could find it much more easily amidst all the other HPI’s.