It’s easy to understand why bone cement — an injectable, quick-setting paste that replaces and supports spongy bone — is increasingly used to repair fractures, and why it’s so popular among patients.

When someone with a wrist fracture is treated using bone cement, he or she typically wears a cast for only two to three weeks, compared with six to eight weeks under conventional treatment. Clinical trials have also shown that these patients experience less pain and swelling.

On Friday and Saturday, about 100 people including engineers, physicians and students explored the topic as Stanford hosted the first symposium on bone cement, sponsored by the medical school’s Department of Orthopedic Surgery and the university’s Division of Biomechanical Engineering.

"This stuff is great. You avoid the long periods of immobilization — the patient can resume normal functioning much sooner," said Brent Constantz, PhD, associate professor of mechanical engineering, who developed the first biodegradable bone cement in the 1980s.

Still, much about bone cement remains unresolved: Which of the half-dozen cements now available is best for particular fractures? What would the ideal bone cement be like? Is it feasible to infuse the cement with human stem cells?

On Friday, presentations covered the evolution of bone cement from the 1960s to today and the mechanical and biological properties of various cements. On Saturday, Stanford physicians who pioneered the use of bone cements presented case studies highlighting fractures from the wrist to the hip to the spine.

The symposium revealed that "this field is still evolving. We don’t have all the answers," said Stuart Goodman, MD, professor of orthopedic surgery and symposium co-chair along with Constantz and orthopedic surgery professor Amy Ladd, MD. What is clear, Goodman said, is that "biologics are a hot area in orthopedics."

The concept of bone cement is not new. The first bone cement — a substance called polymethyl methacrylate, or PMMA — was first used in the 1960s to fill holes in fractured bones and to anchor joint implants. While short-term results were good, some significant limitations later emerged: PMMA caused allergic reactions in some patients; it was not biodegradable; and it often inhibited fracture healing.

While PMMA is still used to anchor hip and knee joint implants, a new class of cements, called biodegradable or biologically compatible cements, has emerged as a favorable alternative. Made with calcium phosphate — a key component of human bone — these cements are easily accepted by the body and are sometimes used instead of bone-graft surgery.

"It’s a new way of thinking about fracture management," Constantz said. "It’s like taking a carpenter who works with hammer and nails and telling him, ‘Now we’re going to glue those two-by-fours together.’" A company founded by Constantz, called Norian, received FDA approval in 1987 for the first biodegradable orthopedic cement. Goodman and Ladd were among the first physicians to test the product in animals and people.

The new cements do have limitations. They cannot withstand heavy loads, preventing use in the middle of long bones such as the tibia. And some cements take up to 20 minutes to set, consuming valuable surgical time.

Engineers are striving to overcome these and other limitations as they develop better cements. They’re aiming to create stronger composites to be used for a wider range of applications. They’re also working toward cements that could carry therapeutic agents, like antibiotics or stem cells, to accelerate bone healing.

The potential impact of these efforts is enormous. There are 6 million fractures in the United States each year, costing $21.3 billion annually, Goodman said.

At the symposium, Ladd — a hand surgeon — presented the case of a woman who, in December of 1998 at age 89, splintered her wrist after falling in the garage of her Menlo Park home. The patient, Maude Oosterhof, received conventional treatment — a cast and three pins through her wrist bones. After two weeks, X-rays revealed that the fix wasn’t holding. Without further intervention, Ladd said, "her functional limitations would be significant, and she’d continue to experience pain."

As a last-ditch effort, Ladd injected a biodegradable cement into Oosterhof’s wrist bone. A few weeks later, she was out of the cast and using her hand again. She later resumed playing the piano.

Today, Oosterhof says her wrist has held up well and hasn’t required further intervention. "The treatment I received was wonderful. I can’t complain."