Smoking Prevention & Cessation

Postoperative Pain

Parkinson's Disease
Medical Center History
Research Briefs
Around & About
POV


The School of Dental and Oral Surgery will receive about $1 million in financial support and implant products from two implant companies to promote clinical research and educational initiatives in the school's dental implant program.

The two gifts from Nobel Biocare, of Göteborg, Sweden, and 3i of Palm Beach Gardens, Fla., will support research to assess outcomes of implant procedures done at the SDOS implant clinic. The research will be conducted by Dr. Peter D. Wang, associate clinical professor of dentistry and director of the 15-year-old implant program.

Training in the use of implants will be introduced more broadly into the pre- and postdoctoral coursework, says Dr. Ira Lamster, dean of SDOS. Installing an implant usually requires two steps. First a titanium base is surgically inserted in the jawbone to act like the root of a tooth. Then, in the restoration component, dentists construct and fit replacement teeth.

Currently the SDOS implant program trains eight residents (in oral and maxillofacial surgery) and postdoctoral fellows (in periodontics) each year in the surgical placement of implants. About four postdoctoral fellows in prosthodontics complete training in restoration each year.

"The gifts of material—implant fixtures and prosthetic components—will allow us to reduce the cost of implants to patients who could not otherwise afford them," Dr. Lamster says.

Implants are alternatives to dentures or bridgework for replacing teeth. The replacement teeth take hold because titanium has a special ability to bond directly to bone.

This quality of titanium was discovered by a Columbia researcher, the late Dr. Richard Skalak, the James Kip Finch Professor Emeritus of Engineering Mechanics and former director of Columbia's Bioengineering Institute, and Dr. P.I. Branemark of the University of Göteborg, Sweden, in the 1960s. Dr. Skalak also developed some of the first titanium dental implants. His studies of the interaction between titanium and human bone tissue have been widely applied in skeletal reconstruction.

—Matthew Dougherty

Orthopedic surgeons have found that both bundles of the knee's posterior cruciate ligament contribute to the knee's stability, even though one bundle is much larger and stronger than the other. The new findings suggest that the recently developed two-bundle surgical reconstruction will result in more complete recovery of normal knee stability than the more common one-bundle construction. The research was published in the March-April American Journal of Sports Medicine.

Of the two PCL bundles, the anterolateral is larger and stronger than the posteromedial, so PCL reconstructions usually only replace the anterolateral bundle. However, the surgery is not fully successful in preventing the tibia from sliding behind the femur. Because the single-bundle surgery is inadequate, major medical centers have started performing double-bundle surgeries, a more complex procedure with the potential for greater complications.

To understand why double-bundle surgeries seem to work better, Dr. Christopher Ahmad, assistant professor of orthopedic surgery, and his colleagues in the Orthopedic Research Laboratory, measured the length and position of both bundles in six cadaveric knees. The knees were placed in a joint-testing rig that held the knee at a range of angles between 120 degrees (flexed) and 0 degrees (straight). Bundle length and orientation were calculated from the locations of the femur and tibia at each angle and the points where each bundle attached to the bone.

The results showed that both bundles are needed to fully stabilize the knee. When the knee is flexed, the posteromedial bundle is oriented more horizontally than the anterolateral bundle. The horizontal orientation lets the bundle resist more destabilizing force than a vertical orientation. When the knee is straightened, the anterolateral bundle becomes oriented in a more horizontal and stabilizing position.

"Neither bundle really dominates," Dr. Ahmad says, "and that has changed the way people think about the surgery. The results support our change to the more difficult and complicated double-bundle procedure."

—Susan Conova

Physicians often prescribe medications to patients before cardiopulmonary bypass surgery to reduce the strain on the heart caused by high blood pressure or hypertension. They frequently recommend a class of antihypertensive medications, called ACE inhibitors, to help blood vessels relax and expand, lowering blood pressure.

However, immediately after cardiopulmonary bypass surgery, patients with ACE inhibitors in their blood sometimes go into vasodilatory shock, a state of low blood pressure or hypotension caused by blood vessels failing to constrict. Usually, the shock is mild but in a small number, more severe shock occurs. To bring blood pressure back to normal, physicians often administer vasoconstrictive drugs, which increase the blood pressure but can cause complications and prolong a stay in the intensive care unit.

Now, in a study led by Dr. Mehmet Oz, professor of surgery at P&S, and Dr. Donald Landry, associate professor of medicine at P&S, Columbia researchers have found that a low dose of the anti-diuretic hormone vasopressin before surgery reduces the incidence and magnitude of postoperative hypotension and limits the use of vasoconstrictive medications.

The investigators conducted a randomized, double-blind trial of vasopressin vs. placebo on 27 patients. Thirteen patients received vasopressin and 14 received normal saline starting 20 minutes before bypass surgery.

They found that a low dose of vasopressin did not affect preoperative blood pressure but significantly reduced the occurrence of postoperative hypotension. The patients in the vasopressin group who experienced postoperative hypotension required lower doses of vasoconstrictive medications and for a shorter duration compared with the placebo group. The vasopressin group also had a shorter stay in the intensive care unit—about one day compared with two for the placebo group.

Although these results seem promising, larger studies are needed before preoperative use of vasopressin can be accepted as a standard of care, Dr. Landry says. The findings were published in the March Annals of Thoracic Surgery. Dr. Landry in collaboration with Drs. Oz and Juan Oliver, associate professor of clinical medicine at P&S, discovered the syndrome of vasopressin deficiency in vasodilatory shock in 1997.

—Matthew Dougherty


[Top]