High-profile patients like New York Yankees slugger Alex Rodriguez and world-class sprinter Tyson Gay have helped hip impingement procedures acquire a certain cachet, but some surgeons say more evidence and long-term patient monitoring is needed to determine the bone-shaving surgery's true usefulness.

The idea behind the combination surgery is this: A hip bone with irregularly shaped rough edges rubs against soft tissue in the joint, causing tendons to fray or muscles to tear. By shaving and smoothing the bone, surgeons hope to protect patients from further injury and prevent the development of arthritis in the hip. The amount of bone that is removed varies, but can sometimes be as much as one-third of the top of the thigh bone.

Advocates justify the procedure by reasoning that bumps on the hip bones can deteriorate cartilage and lead to severe arthritis years down the road. Still, "no one has really proven that it is uniformly helpful to the patient," says Harry E. Rubash, MD, chief of the department of orthopedic surgery at Massachusetts General Hospital and a professor of orthopedic surgery at Harvard Medical School.

Because hip impingement surgery is combined with other procedures to repair torn tissue, it is difficult to assess its true benefits, says Freddie H. Fu, MD, chairman of orthopedic surgery at the University of Pittsburgh School of Medicine. For example, it is difficult to determine whether a patient feels better because the impingement was fixed, because the torn tissue was repaired or both. Dr. Fu also notes that the surgery has only been performed for about 10 years, and cites a lack of long-term follow-up on patients who've undergone the surgery.

Nevertheless, many surgeons are convinced the operation is necessary, and many patients have reported feeling no pain after the procedure. Surgeons have cited the cases of patients followed for relatively short times as proof of improvement after the surgery.

Marc J. Philippon, MD, an orthopedic surgeon and partner at the Vail, Colo.-based Steadman Clinic, is the doctor most associated with hip impingement surgery. He counts Mr. Rodriguez and Mr. Gay among his patients. Dr. Philippon has published reports of athletes' injuries improving after the operation, noting that their hip pain remained in check for at least 2 years. Dr. Philippon says he's planning to publish data that follows professional athletes results over 10 years.

Researchers, however, still have questions regarding hip impingement surgery, including whether the operation prevents arthritis. A recent study conducted at the University of Athens in Greece, for instance, followed 96 patients (average age: 49) with hip impingement but no hip pain. None of the patients underwent hip impingement surgery. After more than 18 years, 20% of the patients had developed arthritis, which researchers said was not unexpected. The researchers determined there was no reason to blame impingement for it, concluding that "prophylactic surgery is not warranted."

Another study indicates there can be a link to arthritis. John J. Callaghan, MD, chair and professor in the department of orthopedics and bioengineering at the University of Iowa, studied a group of patients in their 50s who did not have impingement surgery and needed hip replacements due to severe arthritis. Seventy percent had impingement, but Dr. Callaghan said it is not known whether the bone shaving or reshaping operation can prevent arthritis, or whether the operation's pain-relieving effects last.

"We have absolutely no clue to whether the bone will grow back," says Dr. Callaghan. "There are investigators who are working hard to follow patients, but unfortunately there are a lot of patients being operated on who are probably not being followed long term."

Mark McGraw