Injury, poisoning and certain other ICD-10-CM codes require a seventh character. It records not what happened, but where the patient is in the course of care for it. The same fracture carries a different code on the day it is treated, at a follow-up visit, and years later when a complication appears.
The three you will use most
| Character | Means | Applies when |
|---|---|---|
| A | Initial encounter | The patient is receiving active treatment |
| D | Subsequent encounter | Routine care during the healing phase |
| S | Sequela | A complication or condition arising from the injury |
“Initial” does not mean first
This is the misunderstanding that causes most seventh-character errors. The character A does not mean the first visit. It means active treatment - and active treatment can span several encounters, and can be delivered by more than one provider.
Surgical treatment, emergency department care, and evaluation and treatment by a new physician are all active treatment, whether or not they are the patient's first contact. A patient seen by three providers during active treatment gets A from all three.
Conversely, D is for routine care while the patient heals: cast changes, medication adjustment, follow-up checks. The patient is still under care, but the care is no longer active treatment of the injury itself.
Sequela is the condition, not the injury
The character S marks a sequela - a condition that arises as a direct result of a previous injury, after the acute phase has ended. Scarring following a burn is the standard example.
Sequela coding requires two codes, and the sequencing matters. Code the condition itself first, then the injury code with the S character. The S code never goes first, and the injury code is never used alone to describe the sequela. There is no time limit - a sequela may appear months or years later.
The placeholder X
Some codes need a seventh character but are shorter than six characters. The seventh character must genuinely sit in the seventh position, so the gap is filled with the placeholder X.
The placeholder is not optional and it is not decorative. A code that needs padding and does not get it is invalid, and so is a code where the extension has been placed in the wrong position. This is a common cause of rejections that look inexplicable, because the code appears superficially correct.
Not every code uses A, D and S
Fracture codes are the important exception. They use an expanded set of seventh characters that also record whether the fracture is open or closed and whether healing is routine, delayed, a nonunion or a malunion. There are far more than three options, and the correct one depends on detail that must be present in the documentation.
Always read the seventh-character note attached to the specific code rather than assuming the A/D/S pattern applies. Where a code carries such a note, this site displays its definitions on the code page itself.
A checklist
- Does this code require a seventh character at all?
- Is the patient in active treatment, healing, or presenting with a sequela?
- Does this code use A/D/S, or an expanded fracture set?
- Does the code need X placeholders to reach seven characters?
- If sequela, is the resulting condition sequenced first?