Penal Code Section 12022.7 provides for an additional three year prison term in the event that a defendant is convicted of a felony involving great bodily injury to another person in California. Great bodily injury is defined as "significant or substantial physical injury". In addition, a defendant found guilty of this enhancement must serve 85% of their prison term because such a conviction qualifies as a violent felony. Penal Code Section 667.5(c)(8) classifies a violent felony as "Any felony in which the defendant inflicts great bodily injury on any person other than an accomplice which has been charged and proved as provided for in section 12022.7"
Calcrim jury instructions (3160) state that great bodily injury is an injury that is greater than minor or moderate harm. This would certainly include broken bones, and may also include soft tissue injury that is more than minor and cuts requiring medical treatment. The jury must determine if an injury constitutes great bodily injury, not the judge.
In plea negotiations, prosecutors retain the discretion to dismiss a great bodily injury enhancement thereby avoiding the sentencing consequences of penal code section 12022.7. They may do this in borderline cases where the injury is not particularly serious, or in circumstances where the defendant has paid restitution in full to a victim who is satisfied, or because the defendant has earned consideration and leniency by showing remorse and taking steps to address his or her sobriety. If probation is granted, the judge retains discretion to impose a sentence that does not include state prison time even with a plea to felony dui with this enhancement. A person convicted of a felony DUI with great bodily injury in Los Angeles is, however, presumed not to be eligible for probation.