June 13, 1996
Media Contact: John Cramer
Phone: (410) 955-1534

A surgical laser commonly used to repair knee joints may be a double-edge sword, repairing the knee in the short term but causing hidden damage to surrounding cells and worsening the injury in the long term, an animal study involving Johns Hopkins suggests. The findings indicate that the laser should be used with caution in people.

"Our findings suggest that even when there's no visual evidence of damage, significant cell death in the articular cartilage may occur following exposure to the laser's energy," says Leigh Ann Curl, M.D., lead author and an assistant professor of orthopedic surgery. "This laser may generate lethal heat to cartilage cells that hasn't been previously recognized."

The results are to be presented June 17 at the annual meeting of the American Orthopedic Society for Sports Medicine in Lake Buena Vista, Fla.

Scientists tested the arthroscopic laser, called pulsed holmium:YAG, on joint cartilage taken from cows and measured the effects for four months with an electron microscope and chemical tests. The results show that the laser's energy killed or damaged surrounding normal cartilage cells in a wider area than previously suspected. None of the injured cells recovered, creating a kind of cellular dead zone around the site where the laser touched. The amount of cell death and damage increased the longer the cartilage was exposed to the laser, which produces a concentrated beam of light radiation.

Surgeons use the arthroscopic pulsed holmium:YAG laser for a variety of knee-joint repairs because it effectively cuts tissue, causes simultaneous blood clotting and was believed to cause little or no harm to surrounding cells. An arthroscope is a thin, flexible tube for viewing and treating the inside of joints.

The study was funded by The Hospital for Special Surgery and Coherent Inc., manufacturers of surgical lasers.

-- JHMI --
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