compound
Don't compound compound fractures.
The sentence warns against making serious bone fractures even worse.

Meanings
to combine, mix, or make worse by adding to
- His tardiness compounded the problem.
- The pharmacist compounded a custom medication.
as noun: a substance composed of multiple elements; as adjective: composed of multiple parts (as in 'compound fracture' or 'compound interest')
- Water is a compound of hydrogen and oxygen.
- A compound fracture pierces the skin.
Word origin
From Old French componre, from Latin compōnere ('to put together'), formed from com- ('together') + pōnere ('to place'). The verb-noun stress alternation in modern English follows the trochaic noun rule that governs 'abstract', 'present', 'conduct', and dozens of others.
Fun fact
In medicine, a 'compound fracture' is one where the broken bone breaks the skin — terminology that survives despite the more clinical name 'open fracture' being preferred today. The verb 'to compound' a problem and the noun 'compound fracture' come from the same Latin root: things being put together, in different metaphorical ways.