SAN FRANCISCO (CBS SF) – On average, Major League Baseball pitchers see a drop-off in performance following Tommy John elbow surgery, according to a soon to be released study.

Researchers from Henry Ford Hospital analyzed statistics of 168 MLB pitchers before and after surgery between 1982 and 2010 and found statistical drop offs in three key pitching statistics: Earned runs average (ERA), walks and hits per inning pitched (WHIP) and innings pitched (IP).

READ MORE: Asian American Attacks: San Francisco Police Identify Suspect in Market Street Stabbing of 2 Women

“Tommy John surgery is an effective surgery and most pitchers get back to pitching after surgery. But it’s not going to improve their level of performance,” says Vasilios (Bill) Moutzouros, M.D., a Henry Ford orthopedic surgeon and the study’s senior author. “There’s been a perception that the surgery will make you better. Our findings debunk that perception.”

On average, the number of innings pitched fell among the study group from 59 to 50 per season, while ERA’s swelled from 4.15 to 4.74 and WHIP ticked up from 1.40 before the operation to 1.48 after.

“Eighty to 90 percent of major league pitchers will get back to pitching at the major league level but they just won’t be as effective as they were before injury,” said Moutzouros.

During the procedure, the ulnar collateral ligament in the elbow is replaced with a tendon from the same arm or from the hamstring.

READ MORE: Pedestrian Hit, Killed By Vehicle In Sunnyvale

The report comes less than a week after Dr. Frank Jobe, who pioneered the surgery, died at age 88. The procedure is named after a former Dodgers pitcher who was the first to successfully undergo the procedure and return to the majors.

The newest Giants starter, Tim Hudson, posted two of his most productive seasons after his 2008 surgery. Similarly, former Giants closer Brian Wilson underwent the procedure in college, became a star, and needed the surgery again at the end of his tenure with the Giants. He posted excellent numbers late last year after working his way into the Dodgers bullpen.

The complete Ford Hospital study is being presented at the annual meeting of the American Academy of Orthopedic Surgeons March 11-15 in New Orleans.


MORE NEWS: San Jose Man Killed In Hit-and-Run Collision After Falling Off Electric Unicycle