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1st
appeared 19 April 1999
Prosthetic Device that Saves Legs with Cancer
Also Stimulates Bone Development, Study Finds
A clinical study led by UCSF researchers has found that a new prosthetic device primarily
used to save legs with cancer also stimulates bone development.
"With this new device, we've changed the whole picture of how forces go through the
bone," said James Johnston, UCSF professor of orthopaedic surgery, UCSF Stanford
Health Care orthopaedic oncologist, and principal investigator of the study. "The
fixation device produces an environment where bone appears to heal to a metal surface in a
pattern similar to fracture healing."
The novel device, known as the compliant pre-stress system (CPS), is under investigation
at UCSF and has been in development for over ten years.
"For patients with cancer of the leg, the findings suggest this device will not only
prevent loosening of the prosthetic device but will also allow patients to function long
term," said Richard O' Donnell, UCSF assistant clinical professor of orthopaedic
surgery and UCSF Stanford Health Care orthopaedic oncologist.
UCSF researchers presented preliminary findings April 14 at the International Society of
Limb Salvage Surgeons meeting in Cairns, Australia.
Prior to the use of prosthetic devices, patients with cancer of the leg required
amputation, said the researchers. Since the early 1970's, prosthetic devices have been
used to replace cancerous bone and knee joints, allowing the leg to function normally.
The conventional system involves a titanium implant, a
six-inch stem that is cemented in the canal of the femur or the thighbone.
"Previous research has shown that the conventional implants are becoming loose and
failing in approximately 50 percent of the cases after 10 years and 75 percent of the
cases after 20 years," said Johnston.
When the implants become loose, said the researchers, patients experience pain, may start
limping, or may not be able to walk.
The problem with the conventional system, said the researchers, is that bone surrounding
the metal stem disappears over time because the conventional device is stress shielding -
it prevents force or stress to the bone. Without stress, they said, the bone atrophies,
resulting in loosening of the implant.
Another problem with the conventional device is that bone and metal are not compatible.
The bone does not integrate or grow into the metal, which plays a role in loosening of the
implant.
Concerned with the high failure rate of conventional implants, the UCSF researchers
designed the new CPS system and have been studying the effectiveness on patients for the
past seven years.
Links:
UCSF Orthopaedic Surgery
UCSF Stanford Health Care
UCSF Stanford orthopaedics
Source: Lordelyn P. del Rosario,
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