ORTHOPEDICS
Growing a
Growth Plate
Between operations, pediatric orthopedic surgeon
Nancy Hadley-Miller, MD, sips tea and looks at X-rays.
She pulls the femur and tibia of an 8-year-old girl. On
the righthand head of the tibia, just below the knee joint,
the clean black line of the growth plate breaks up into
a smear of grey, marbled and indistinct. The fracture
punched through the growth plate, and when it healed it
healed as bone. Effectively sealed, the plate can’t expand.
The bone can’t grow.
“Trampoline injury, if I’m not mistaken,” she remarks.
In her 30-plus years as an orthopedic surgeon, Dr. Hadley-Miller has seen thousands of
injuries like these. At Children’s Hospital Colorado alone, the Orthopedics Institute sees
150 to 160 fractures a week, about 30 percent of which affect the growth plate. Of those,
3 percent might form a “bony bar” like that of Dr. Hadley-Miller’s 8-year-old patient. On
average, that’s perhaps one a week.
If the bar fuses less than half the growth plate, Dr. Hadley-Miller and surgeons like her
can resect it and fill the area with a material to stop it from reforming: sometimes a fat
graft, sometimes bone cement. Neither option is great. Fat degrades and melts away.
Bone cement goes on hot, inflaming the surrounding tissue, and while it lasts longer, it
can’t grow with the patient.
That’s best-case scenario.
In many more cases, surgeons injure the counterpart limb — killing its growth plate, too.
Given her age, that was the only option for the 8-year-old on Dr. Hadley-Miller’s screen.
Her tibia won’t ever grow, but at least she won’t have an angular deformity.
“There’s a real need for better treatment options,” says Karin Payne, PhD, Dr. Hadley-
Miller’s research partner and Director of the Payne Regenerative Orthopedics Lab at the
University of Colorado School of Medicine, which shares both campus and faculty with
Children’s Colorado. “Currently there’s no clinical treatment that can regenerate growth
plate tissue.”
Unlike bone, the growth plate comprises five distinct zones. Cartilage cells form in the
top zone, proliferate in the next and hypertrophy after that. Then they die and calcify,
to be broken down by osteoblasts and, finally, replaced by mineralized bone tissue.
This process continues through skeletal maturity, when the plates fuse.
A stain of a tibia taken from an animal model shows the formation of a
blue line of cartilage across the growth plate in response to treatment
with cartilage-promoting agents.
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NEW CONSTELLATIONS
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