Wiki How do I know when I NEED a modifer?

use modifiers when...

...the code description in the CPT/HCPCS manual does not completely describe the service that was provided by the doctor...that is the most common usage of modifiers.
Hope this helps
A modifier is exactly what it's called, it modifies a code when it's appended. Modifiers give more information reguarding a service that was provided.

I would suggest that you study your modifiers and learn them like the back of your hand. When reading reports there will come times more often than not that you will need to append a modifier to a code or codes to "complete the picture."

When you learn your modifiers you will know when to use them. For instance, a bilateral procedure is done, but the correct code does not specify "bilateral." You would append modifier -50 (bilateral procedure) to that procedure code to indicate that the procedure was done on BOTH sides of the body, rather than unilateral or ONE side. (However, some code descriptions specify a bilateral procedure; in these instances you would not append modifier -50 because it was specifed in the code already.)

-LT, a procedure that is done on the left side of the body, -RT, a procedure that is done on the right side of the body. ...and so forth.
I'm not sure when I need a modifer.....

example 29125-59-RT, 73110, 73100

You do not need a -59 modifier here. The -59 is a misunderstood and overused modifier. This should only be used when you bill two codes that are bundled and there is reason to unbundle the codes. Here are the reasons per CMS:
1) Different sites
2) Different incisions
3) Different encounters

See this article for more info on -59:

CMS publishes many manuals including one on modifiers.
However, I disagree with Katie. The mod -50 is not simply for bilateral pxs. Mod -50 is for paired organs only, not both sides of the body. Often the code will be entered twice for bilateral procedures.

If you can justify a modifier, you will code it as:

29125 73110 73100-59


29125 73110 RT 73100 LT

In order to justify that -59 it should be on the other wrist. If it wasn't a contralateral shot (with supporting med nec), I'd suggested seeing Chapter 9 on the NCCI Policy manual. They are pretty specific on how you can bill for multiple images of the same fracture/lesion

Modifier -50

Mod -50 means DR performed the same procedure on the contralateral side (organ or not). Unfortunately, the use of modifer -50 is not that easy. To be sure you're allowed to use mod -50, I'd suggested pulling Medicare Fee Schedule. That will tell you what codes CMS will allow modifier -50 with. Got to page 5 and download RVU12AR

To add to DeeCPC: RT/LT is the equivalent of modifier -59 and are never used together.