Extraspinal CMT Performed Same Date as Spinal CMT

I have always been under the premise that when billing 98943, extraspinal chiropractic manipulations, on the same visit as spinal manipulation 98940-98942, that the extraspinal manipulation requires modifier 51. However I recently received a denial from United Health Care that the modifier was improper. Is there a requirement to use 51 modifier with this combination of coding?
From the initial adoption of the current CMT codes 98940-98943 there has been a general acceptance that when extraspinal was billed with spinal that the extraspinal manipulation code is to be appended with modifier 51. This modifier was often thought by many chiropractors that it indicated a separate distinct manipulation and in fact that assumption was incorrect.
Modifier 51 (multiple procedures) is used to inform payers that two or more procedures are being reported on the same day. A claim form (CMS 1500) that has modifier 51 appended to a CPT code(s) tells the payer to apply the multiple procedure payment formula to the CPT code(s) linked to the modifier 51. Therefore in actuality it was not to inform that a separate service was done but that multiple procedures were done and that a fee reduction applies. This is why United Health Care reduced the fee of 98943 by 50% as it was the use of the 51 that indicated such.
Clearly 98940-98942 compared to 98943 are distinctly separate as the former indicates manipulation to the spine and the latter to an extraspinal region. Clearly and based on the code description a modifier was not needed to indicate they are separate and if it did the modifier would be 59 not 51. Per the CPT description and definition of modifier 51, is not appropriate for use with E&M services or physical medicine rehabilitation services. Of course chiropractic manipulation is neither an E&M code nor physical medicine rehabilitation service but would appear to fall in the same range and likely it too should not be used.
Then why would a carrier require it for a CMT as a multi-procedure when it is not used for any other services that fall under physical medicine? The answer appears to be simply it allows a 50% reduction of the fee. In my opinion the use of 51 always appeared inappropriate as the services are clearly separate and while the pre-manipulation assessment associated with CMT is part of the overall service there is distinctly a separate premanipulation to extraspinal regions that would not be included in the spinal regions. And furthermore there should not be any reduction of the fee to extraspinal simply because spinal manipulation was done. The premanipulation assessment for the spine does not include what is necessary to assess nor manipulate an extraspinal region a reduction of fee on that basis would seem improper.
While many if not most carriers have abandoned the need and use of the 51 there were several carriers that maintained the requirement. Specifically United Health Care (Optum Health), as you noted, did so. However they recently eliminated the need due to AMA, The CPT® Assistant, who made a definitive statement on need for the 51 modifier with chiropractic manipulation.
According to “The CPT® Assistant” [December 2013], these are separate and distinct procedures and the use of modifier 51 does not apply. Modifier -51 (Multiple Procedures) does not need to be appended to the extraspinal CMT code (98943), when billed in conjunction with chiropractic manipulative treatment (CMT) codes (98940- 98943). Due to the definitive nature of the publication in relating to coding of CPT this means that 51 does not apply and more importantly nor does the 50% reduction of payment.
In response United Health Care in April 20014 published that there is no longer a need for the use of the 51 modifier for extraspinal chiropractic manipulation when done in conjunction with spinal manipulation.