Below is from AMA CPT Changes 2002, the clinical example they provide for 20553 describes three separate muscles. I have wonder the same thing that you are stating in your question, I have always counted per separate muscle name that is documented to be injected. I know that you have already received a response to question, but since the way I have been counting the muscles differs from your response. I thought I would provide another view point with the understanding that there is nothing from AMA that specifically addresses your question.
Clinical Example (20552)
A 60-year-old female with a three-month history of pain in the left low back above the left posterior iliac crest with radiation of pain into the left buttock. Muscle relaxants, nonsteroidal anti-inflammatory drugs, and physical therapy have been ineffective in relieving her pain. Physical examination reveals no evidence of neurological dysfunction, but does reveal a distinct trigger point in the multifidus muscle left of the L5 spinous process. She now presents for injection of the trigger point.
Clinical Example (20553)
A 40-year-old male presents with chronic left neck and right upper back pain resulting from cervical degenerative disk disease and myofascial pain syndrome. The patient has already completed a trial of physical therapy and nonsteroidal anti-inflammatory drug therapy without relief of his pain. Physical examination reveals no evidence of neurological dysfunction, but does reveal three distinct trigger points in the left multifidus muscle, the left trapezius muscle and the right levator scapular muscle. He presents for injection of the trigger points.
