Inside, the body’s own stem cells switched on to
A husband and wife research team has found a way to use the
sleeve-like cover on bone to heal serious bone injuries faster and more
simply than current methods. And they’ve developed an artificial sleeve
that spurs fast healing when a car wreck, bomb blast or disease leaves
too little cover.
Melissa Knothe Tate, a joint professor of biomedical engineering and
mechanical & aerospace engineering at Case Western Reserve
University, and Ulf Knothe, an orthopedic surgeon at the Cleveland
Clinic, announce their work at the annual meeting of the Orthopedic
Research Society in New Orleans this week.
Knothe used the technique on a wheelchair-bound patient who suffered
from cerebral palsy, hip dysplasia and a curved spine exacerbated by
legs of differing length. To lengthen her shorter leg while correcting
her hip dysplasia, he replaced the hip joint with a long-stemmed
prosthesis, in the process cutting and spreading the femur to match the
length of its mate. Around the newly-created gap in the femur he left a
section of the periosteum, the bone’s sleeve-like cover, intact to
envelop and heal the gap.
Inside the sleeve, bone grew and matured around the prosthesis stem.
The patient has since learned to walk again.
Why does the sleeve work?
"The sock-like sheath on the outside of the bone is a habitat for
stem cells," Knothe Tate explained.
In testing on sheep in Switzerland, animals that had the periosteum
operation to bridge a 1-inch gap in their leg stood within 24 hours and
had substantial bone filling the gap within two weeks. In the lab,
Knothe Tate and fellow researchers found that direct and angular
pressure on stem cells from periosteum stimulated the cells to develop
into bone. They believe the pressure of standing and shifting weight
drove the bone growth in the sheep.
"Just like in the embryo, given the right trigger, the cells build
bone like crazy," Knothe Tate said.
She tested the periosteum process against the standard bone graft
technique of packing the gap with spongy bone taken from the pelvis and
included a third model in which the gap was packed with spongy bone and
covered with periosteum. The results showed the periosteum alone healed
fastest and with the greatest density. "Surprisingly, including the bone
graft slowed the healing process." she said.
In addition to better results, the surgical procedure is simpler for
the doctor and patient, the couple says. That’s no small matter: of the
nearly 8 million bone fractures that occur in the U.S. annually, about
1.5 million result in bone grafting operations.
Compared to the process called distraction osteogenesis, which uses
pins inserted through the skin and into two lengths of bone to pull them
together and bridge a large gap, the perisoteum procedure is far less
invasive and less likely to result in infection and other complications.
Knothe, who has worked with patients suffering bone cancer or bone
loss from traumatic injuries, knows that sometimes there is not enough
periosteum to make a sleeve.
With support from the Case-Coulter Translational Research Program,
the couple designed an artificial periosteum and Knothe Tate produced
the novel implant, a sleeve made of materials approved by the Food &
Drug Administration for other treatments. In sheep testing, collagen,
collagen and cells scraped from periosteum, and pieces of periosteum
were tucked into the artificial sleeves. Sheep treated with pieces of
periosteum healed fastest, followed by those with collagen and cells.
"The next step is to bring the technology to the clinic, to broaden
its access to the general public beyond the top clinics, for example for
patients relying on hospitals in rural areas, as well as for soldiers
injured on the battlefield," Knothe said. "You can sterilize the
membrane in an autoclave, along with the surgical tools. Its modular
design makes it easily adaptable to a variety of clinical situations."
The couple has filed for a patent on the artificial periosteum and is
now working with other researchers to develop optimum materials to