hi mary,
this is billable per knee/ per session. (not per plug).
The lay description according to optum/ encoderpro.com states:
"multiple cylindrical grafts are placed in corresponding size cylindrical holes made in the recipient area-instead of using one larger bone plug. Portals for inserting the instruments are chosen to ensure perpendicular access to the recipient site. Detached cartilage is excised, the margins squared off, and the subchondral bone is abraded to healthy, bleeding tissue. The number and size of grafts needed is determined. In 29866, a tubular chisel is used to harvest cylindrical osteochondral grafts down to the desired level, perpendicular to the cartilage surface, from the patient. Grafts are harvested from the non-weight bearing patellofemoral area, medial or lateral femoral trochlear rim, or the intercondylar notch periphery. The grafts are ejected from the chisel. A guide tube is put in place and the recipient hole is drilled to the desired depth with a graduated bit, replaced with a tapered dilator, and the graft is inserted and tamped into place. This is repeated until all grafts have been placed. Report 29867 when fresh donor tissue from a tissue bank is used instead of harvested from the patient."