Question: Our orthopedist documented an "Elmslie-Trillat procedure" for patellar instability of the knee. Which code should we assign? Pennsylvania Subscriber Answer: Elmslie-Trillat procedure describes a tibial tubercleplasty. You should report 27418 (Anterior tibial tubercleplasty [e.g., Maquet type procedure]), along with the diagnosis code 718.86, for this procedure. Code 27418 also applies when the orthopedist documents a "Fulkerson procedure," because these surgeries are very similar.