Bella, I add the modifier 59 when billing these 2 codes when documentation supports it. Here is an excerpt from Margie Vaught, who writes for AAOS:
Rotator cuff repair
Open rotator cuff repair is confusing because three codes can be used: 23410(Repair of musculotendinous cuff, acute), 23412 (Repair of musculotendinous cuff, chronic) and 23420 (Reconstruction of complete shoulder [rotator] cuff avulsion, chronic [includes acromioplasty]).
There are no standardized definitions to distinguish acute from chronic. What often makes the difference is the size of the lesion (i.e., how many tendons are involved or whether the lesion is less than 1 cm, 1 cm to 3 cm, 3 cm to 5 cm or more than 5 cm), as well as the amount of retraction and scarring, not how long ago the tear occurred.
Code 23410 should be reserved for young patients who have an acute episode resulting in a torn rotator cuff and early repair. Code 23412 is more appropriately used for most of the rotator cuff tears that occur in older individuals who have sustained a tear over time, with or without a superimposed acute episode.
If there is significant retraction with a large tear, extensive releases and mobilization may be required, justifying the use of code 23420. If fascia or synthetic material is required, code 23420 also is appropriate. If a tendon transfer was performed, code 23397-59 would be used in addition to code 23420.
Arthroscopic rotator cuff repair is code 29827 (Arthroscopy, shoulder, surgical, with rotator cuff repair). If arthroscopic subacromial decompression with or without acromioplasty and/or coraco-acromial ligament release also is performed, code 29826-51 is appropriate. If arthroscopic subacromial decompression is done, followed by an open or mini-open rotator cuff repair, the coding sequence should be 23410 or 23412 and 29826-59.
Hope this helps!
Ray CPC