A 56-year-old female patient with a history of degenerative disc disease at levels T2-T3 and...

The case describes two primary surgeons working together, which supports modifier 62 (co-surgeons) on the spine fusion/discectomy codes.

22556 = primary level anterior thoracic discectomy and fusion (T2–T3)

22585 = each additional thoracic level (T4–T5)

20931 = structural allograft (reported by the surgeon who solely performed/placed the structural allograft, per the statement—Surgeon Z)

Why D fits best:

Surgeon X performed the approach/exposure and closure and assisted the primary surgeon → reports the co-surgeon spine procedure codes (22556-62, 22585-62).

Surgeon Z performed the discectomy/fusion and solely performed utilizing a structural allograft → reports 22556-62, 22585-62, plus 20931.

Options with -51 are not correct here (and add-on/related reporting logic in CPT does not support the way -51 is applied in those options).