Robot-Assisted Hip Surgery Is a Medical First

In what is cited as a medical first, surgeons in Sacramento have used a specially designed robot to help them perform a hip replacement surgery. Although robots have been used by surgeons in the past to help align instruments for brain surgery, the Sacramento procedure apparently marks the first time a robot has actively participated in an operation.

The robot--actually, a seven-foot flexible arm with a drill on the end--was used in the surgery Saturday to produce a precisely drilled cavity in a person’s leg bone to hold a long titanium pin for the ball-and-socket joint. The idea is to get such a good match between the cavity and the pin inserted into it that no cement will be necessary to hold the prosthesis in place.

“Our hypothesis is that if we do the surgery more precisely, then the outcome will be better,” veterinarian Howard Paul told the Sacramento Bee in an interview coincidentally published Saturday, before the surgery at Sutter General Hospital was disclosed Sunday.

Hospital spokesmen Sunday refused to release any information about the operation other than to say that it was successful and that the unidentified patient was “in stable condition and resting comfortably.”

Sacramento orthopedic surgeon Dr. William Barger performed the surgery using the robot he had developed in conjunction with Paul while both were on the orthopedics faculty at the UC Davis School of Medicine. The pair have formed a Sacramento company, Integrated Surgical Systems Inc., to market the robotic arm, which they call “Robodoc.”

The team is scheduled to release additional information about the operation at a news conference in Sacramento this morning.

About 200,000 Americans undergo hip replacement surgery every year when their hips become painfully damaged, most often from the complications of arthritis. The new procedure employing the robot surgeon would not be appropriate for all patients, however.

Conventional hip replacement is fairly successful in patients over age 65. In those cases, the titanium pin is cemented into the leg bone, the femur, and the joint is expected to last for the rest of the patient’s life.

But younger patients are more active, putting much more stress on the prosthesis. Because of that stress, the cement tends to deteriorate over about a five-year period, once again leaving the patient with a painful joint that often needs to be replaced a second time.

In such patients, surgeons prefer to insert the pin into the femur without cement. That necessitates constructing a very precise cavity so that the pin does not slip and slide around in it. But creating such a precise hole, usually about 8 to 10 inches deep, with hand-held tools is extremely exacting and requires exceptional skill. Robodoc was developed to circumvent the need to use such crude tools.

“When we aren’t as exact now as we want to be,” Paul told the Bee, “Mother Nature helps the healing and the patients do fine. So what would it be like if we can do a really precise job with the surgery and still let Mother Nature help in the healing process?”

In practice, the robot arm is attached to the hip and femur with three cylindrical pins that hold it steady. Using data obtained with a sophisticated X-ray imaging device called a computed tomography scanner, a computer directs the arm and drill so that the hole is positioned precisely. An external “fixator,” similar to the frameworks used to hold a fractured wrist immobile while it heals, is attached to the femur to prevent it from moving during the surgery.

Saturday’s first use of the robotic arm in a human came after six years of work and 26 experimental uses of the robotic arm in dogs. The team has permission from the U.S. Food and Drug Administration to perform 10 such operations in humans to test the system.

If these preliminary tests are successful, the team will ask the FDA for permission to do a full-scale clinical trial in which results obtained with the robot arm would be compared to those obtained with conventional surgery.

Drs. Yik San Kwoh and Roger A. Slater, neurosurgeons at Memorial Medical Center in Long Beach, have developed a robot assistant for brain biopsies that they have used in humans since 1985. The robotic arm, not very different from the Sacramento device, uses a similar principle to help the surgeons drill a hole in a precise spot on the skull and insert a probe to retrieve tumor tissue for biopsy.

But in their case, the surgeons have to manually control the depth to which the probe is inserted. Robodoc works independently once it is activated.