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Synthetic 'dust' may replace bone grafts

By Ann Geracimos (Contact) | Wednesday, December 10, 2008

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Strong when solid, the human ankle is the source of immense grief when impaired. Compared to the hip or knee, the ankle is the smallest joint supporting the entire human frame.

"Every pound of body weight is magnified by gravity as much as seven times," says Dr. Steven K. Neufeld, a surgeon in Arlington, where he directs the Orthopaedic Foot & Ankle Center.

As people live longer and stay more active, medical professionals like Dr. Neufeld are seeing a greater increase in foot and ankle injuries - hence, a greater need for surgical repair with its attendant complications. Some are recreational athletes, the 40-plus boomers he calls the "weekend warriors."

All this may be good for the surgeon business, but it is seldom a solace for patients who must endure considerable pain and frustration - not to mention lack of mobility - while awaiting a return to normalcy.

Reston resident Kathleen Kadela's situation is a case in point. Human bodies differ according to their history, and treatment depends on the kind of injury sustained by the patient. Ms. Kadela had routine surgery after breaking her ankle in 2007. The fracture healed but she developed arthritis - the acute or chronic inflammation of a joint often caused or aggravated by an earlier injury. By August, she had not been able to walk on her own without pain for many months. In addition, the heavy leather and metal boot she wore to keep her foot stable limited her activity and meant her circulation was poor, making her condition even worse.

She also lived alone and had to climb stairs to get to her living quarters. She was certainly ready - and surprisingly cheerful - when it came time for the operation proposed by Dr. Neufeld, a procedure known as ankle fusion that is undertaken when just about every other palliative measure fails.

Normally, "three bones in the joint work in concert and move like a hinge," Dr. Neufeld says. Due to arthritis and the resulting loss of cartilage, the bones of Ms. Kadela's ankle were rubbing against one another. Under anesthesia, he would fuse two bones into one, using screws and rods, so that eventually - ideally - they heal. "Imagine two pieces of dough becoming one," he says.

Unfortunately, the fusion doesn't always take, especially in people with poor blood flow to the bone. A bone graft may then be required to fill the space between the bones, which entails using marrow, or living cells, from the patient's leg or hip so the healthy cells will encourage growth. Without this secondary procedure, which is done at the time of the fusion, the patient may have a less successful outcome.

But the second incision - taking bone from another part of the body - is painful, prolongs recovery, and opens up the further possibility of infection. Even in the best of circumstances, the fusion can take between six and 12 weeks to heal.

Ms. Kadela's operation at Virginia Hospital Center in Arlington took two hours and included taking marrow from her tibia (the thicker of the two leg bones) and placing it in her ankle. The marrow from her tibia was replaced with croutons - bits of bone from a cadaver - so she would not lose strength in the leg. Dr. Neufeld scraped off the soft part of the arthritic ankle bones, placed metal screws and a support brace, sewed up the wounds, and predicted that, as a result, "she will walk straight but not have the full mobility of her foot."

She is healing well, he reported recently, despite a staph infection acquired either in the hospital or during a long recovery in a nursing home that slowed her progress. Laid off work since September and confined to home, she still hopes to be able to visit her brother in Florida over Christmas. "I wish I had some Skymiles for all the time I've spent going back and forth to the doctor," she said by phone, with her spirits if not her ankle fully intact.

What Ms. Kadela experienced is what orthopaedic specialists like Dr. Neufeld call "the gold standard across the country and the world" - using the patient's own bone to help in the repairing process but leaving the patient with two incisions, two operations in one.

Another option is on the horizon, however, depending on results of an ongoing clinical trial at 34 sites around the country, including Virginia Hospital Center. If approved for use, the approach, which involves a new bioengineered substance, is expected to reduce patients' pain and recovery time significantly by reproducing a powerful triggering protein normally found in the body and known to be helpful in bone formation.

Four years in the making, the product's trade name is Augment - "as in augmenting natural healing," says Steven Hirsch, chief operating officer of BioMimetic Therapeutics Inc., in Franklin, Tenn., its developer. Many of those taking part in the trial, including Arlington's Orthopaedic Foot & Ankle Center, regard the synthetic as cutting-edge technology. Known in medical parlance as PDGF - for (blood) platelet-derived growth factor - it has been referred to as "magic dust" by one medical practitioner, impressed by its potential.

Hopes are high for the substance, which is a mix of two components with the consistency of wet sand - a vial of liquid and a powder (hence the "dust") - packed into bone to replace material extracted from another part of the body.

Early reports for the experimental bone graft substitute are encouraging. A pilot study showed no serious adverse effects. "If we can demonstrate it is effective in this application, then we might move on to other trials that could demonstrate its effectiveness as a bone graft substitute for other bones in the body," Mr. Hirsch says. This might include helping repair wrist fractures or hip fractures, all done "to encourage the body's own regenerative processes."

A previously approved product, GEM21S (for growth factor enhanced matrix) was developed and sold by BioMimetic to be used in periodontal surgery for grafting defects in the jaw bone that result from severe periodontal disease.