Several years ago, the University of Pittsburgh's Dr. Freddie Fu began performing an innovative surgery to repair a common knee injury: a tear in the anterior cruciate ligament.

While most surgeons use a single bundle of tendon fibers, Dr. Fu, the Pitt medical school's chairman of orthopedic surgery, often uses two, placed near each other and at different angles.

He and other researchers from around the world will discuss what they have learned about the approach during a three-day conference that begins in Pittsburgh tomorrow.

More than 200 surgeons and other health professionals are expected to attend the conference, "Anatomic Double Bundle ACL Reconstruction," at UPMC Shadyside. Surgical skills workshops also are being held today and Saturday.

Dr. Fu, who learned of the double bundle approach from doctors in Japan, believes it more closely restores the anatomy of the uninjured knee compared to the standard, single bundle approach.

For the last 30 years, most ACL tears have been repaired through a "one-size-fits-all surgery," he said.

Concerns have been raised that single bundle reconstruction does not provide full stability to the knee. Some patients complain of persistent instability and pain.

But some experts question whether double bundle surgery, which requires more time and expertise, is clearly better.

Proponents "have not been proved wrong, but neither have they provided convincing evidence this is the best way," said Dr. Gary Poehling, a professor of orthopedic surgery at Wake Forest University, Winston-Salem, N.C.

"It's a very useful exercise to be asking, 'Are we doing well enough with single bundle reconstructions?' said Dr. Donald Fithian, director of the Dale M. Daniel Center for Orthopedic Research at Kaiser Permanente in San Diego.

Still, "there's a fair amount of controversy" about double bundle surgery, he said, "and a large number of respected orthopedic surgeons who have not jumped on that bandwagon."

Both surgeries are performed arthroscopically, with a tiny camera and surgical instruments inserted through incisions around the knee.

Dr. Fu and his colleagues are working to investigate the merits of double bundle surgery. At Pitt, more than 20 studies have been completed or are underway.

One study found some evidence that the surgery did a better job of restoring normal movement and stability to the knee compared to similar patients who had single bundle surgery, said Dr. James Irrgang, director of clinical research for Pitt's Department of Orthopaedic Surgery.

Dr. Fu also recruited another researcher, Dr. Scott Tashman, from Henry Ford Health System in Detroit. He directs a new biodynamics laboratory that will conduct motion analyses of surgically repaired and uninjured knees. The $2 million facility was funded by the Pitt medical school, the Department of Orthopaedic Surgery and the University of Pittsburgh Medical Center, with academic support from Pitt's School of Engineering.

Dr. Tashman's earlier studies involved high-speed X-rays of patients running on treadmills. Movement of the reconstructed knee was compared with that of the uninjured knee.

He said those results showed that single-bundle surgery is not perfect and that replacement tendons used to make repairs can lengthen over time. The differences may not be noticed by patients, he said, but could create abnormal stresses that might lead to arthritis.

Dr. Tashman said his subsequent research involving nine double bundle patients at Henry Ford suggests those patients had more normal knee motion.

At Pitt, he plans a randomized controlled trial, along with Dr. Fu and Dr. Irrgang, that compares the two surgical approaches in a total of 100 patients.