“Avascular necrosis has been an enigma for orthopedic surgeons for a long time,” states Dr. James A. Nunley, Chief of Orthopedic Surgery at Duke University School of Medicine. Avascular Necrosis Resources recently had the pleasure of interviewing Dr. Nunley about the procedure of vascularized bone grafting as a possible treatment for avascular necrosis (also called osteonecrosis or AVN) of the talus. Until recently, conventional medical wisdom was that the talus could not be treated with a vascular bone graft, a procedure where living bone is transplanted along with its blood supply. According to Dr. Nunley, “...no one had found a reproducible area of blood supply that would allow us to perform that operation in a routine manner.” In 2003, Dr. Nunley and his team of medical research students at Duke University made an astounding breakthrough in the area of vascularized bone grafting that may eventually lead to a possible cure of avascular necrosis in the talus.

 

Avascular necrosis occurs when the blood supply is temporarily or permanently cut off from the bone, causing it to die. Researchers have long recognized that the first critical step in curing avascular necrosis is to bring back the lost blood supply. However, one aspect of avascular necrosis that has perplexed doctors is that once the bone dies, a change often occurs at the cellular level within the bone that inhibits the bone's ability to heal the dead tissues. Also, once a bone dies, blood no longer flows through the vessels of the dead bone, further compounding the difficulty of attempting to heal and regenerate the cells. With the normal vessels and pathways no longer functional, doctors began seeking alternative methods of reestablishing blood flow to the bone.

 

In the 1970s, researchers at Duke University leveraged their extensive background in microvascular surgery to invent a procedure called “free vascularized fibular bone grafting” for the hip in which the surgeon transplants healthy, living bone that has an attached blood supply in it into an area of AVN-affected bone in the hip. Like a seed, this transplanted bone will begin sprouting tiny capillaries and eventually grow and fuse into the graft site. According to Dr. Nunley, “We've done 3,500 of those [free vascularized bone grafts] at Duke since 1979 when I did the very first one, and that's been pioneered by Dr. Jim Urbaniak. There are multiple publications that we have on this showing that if we can catch you in stage 1 or early stage 2 disease, we have a 90% cure rate for patients.”

 

Around the same time that Duke's researchers were pioneering the use of vascularized bone grafts to cure AVN of the hip, a Japanese doctor named Dr. Hari had invented a similar technique to successfully treat and cure AVN in the lunate, one of the small wrist bones (also known as Kienbock's Disease). According to Dr. Nunley, “Dr. Hari invented an operation in which he took a small artery and a small vein under the microscope, and sewed them together as a vascular loop, much like they do for the patients on kidney dialysis. [Dr. Hari] then placed the fabricated vascular loop into the bone, and lo and behold, that caused revascularization of the bone and sprouting of tiny capillaries.”

 

Building upon his knowledge of vascularized bone grafts in the hip and wrist, Dr. Nunley shifted his clinical emphasis in the 1990s to working with just the lower extremities. In 2000, he posed an intriguing question: “If we are able to do this [cure AVN by reintroducing new blood supply via a bone graft] in the hip and in the wrist, why can't we do this for avascular necrosis of the talus?” The reason, Dr. Nunley discovered, was no one had been able to find “a reproducible area of blood supply that would allow this operation to be performed in a routine manner.” Dr. Nunley along with some of his medical students went to the laboratory in search of a solution to this problem of lack of blood supply.

 

The research undertaken by Dr. Nunley and his medical students proved fruitful as they discovered a groundbreaking method in which “vascular carotids” (robust blood vessels) could be utilized along with donor bone from the cuboid bone of the foot to perform vascularized bone grafts in the talus. One significant aspect of this discovery is the realization that the cuboid bone has enough redundant blood vessels that one blood vessel attached to donor bone can be removed for the purposes of grafting, yet, there are still enough blood vessels remaining with the cuboid to nourish the bone. Dr. Nunley explains, “The cuboid is on the outside of the foot and it has a very long pedicle, so that I can take it out of there and flip it up and put it inside the talus. The cuboid bone is a good place to take bone because it has a very robust blood supply and the body doesn't miss it.” Eventually, the void left from the graft site heals and fills in. In addition, “it's not on the medial side of the foot which is the more important side of the foot.”

 

Bones involved in a vascularized graft

From "Anatomy of the Human Body"

 

Dr. Nunley's procedure of “rotational vascularized pedicle bone grafting” starts with the surgeon cutting a very small incision through the skin to expose the necrotic bone. The surgeon then removes portions of the necrotic bone using a drill, similar to a “core decompression" procedure, and prepares the site to receive the graft. The healthy donor bone with its blood vessels attached is then harvested from its location and placed into the graft area. The newly implanted graft with attached blood vessel are carefully checked to ensure proper blood flow and and then the incision is closed.[1]  Best of all, this new procedure can be performed reliably and repeatably by orthopedic surgeons.

 

Rotational vascularized pedicle bone graft
From Duke University

 

Dr. Nunley explains an additional recent advancement to this surgical procedure as “In the last two cases that I did, in addition to making the core decompression and putting in the vascularized bone graft, I actually put in a genetically engineered bone morphogenic protein, which will help the bone cells to recreate new bone." This newly introduced engineered morphogenic protein is being used in other procedures to treat avascular necrosis as well. Dr. Nunley shared, “I'm aware of a report, that is not published, on a surgeon who simply does a core decompression and then puts the bone morphogenic protein in, and does no vascularized bone graft. So other people are thinking about this and thinking about things that they can put inside the bone to try and reverse the pathology as well.” It is too early to know how this research into engineered morphogenic protein will possibly aid the outcome of vascularized bone grafts or core decompression surgeries. Nonetheless, this type of research is certainly a very important and exciting advancement.

 

Dr. Nunley has performed approximately 15 of these rotational vascularized pedicle bone graft surgeries on the talus since 2004 and is excited to report, “To date, there haven't been any failures.” Unfortunately, only a very few doctors and patients even are aware that this procedure exists and is an option for treating avascular necrosis. Dr. Nunley expects that as soon as he is able to publish the clinical results, after he has had more time to review post-operative patients for follow-up data, more physicians and patients will look to this as a viable alternative to total ankle replacement.

 

Dr. Nunley cautions that not everyone is a candidate for this procedure, regardless of where in the body their AVN occurs. If a patient already has 100% dead, collapsed, cracking, or fallen bone, they are not a candidate for this procedure. For patients with AVN of the talus, the "ideal candidate has less than 50% of the talus affected by AVN, does not have any articular surface collapse of the ankle, and would not require continual or repeated exposure to factors that may have been the cause of the AVN [such as steroid medications, alcohol, or physical trauma]."

 

The risks accompanying this procedure are the same as for a standard core decompression, according to Dr. Nunley. Patients may be placed on blood thinning medication as a preventative measure to prevent blood clotting.  Also, patients must be aware that the surgical site will be weakened and will require care to prevent fracture. Dr. Nunley expains, “Because a small hole is drilled in the talus (approximately one centimeter in diameter), this weakens the bone, and therefore after the procedure patients will not be able to bear weight on the extremity for three months. [Also], for one year, the patient must wear a PTB (Patellar Tendon Bearing) brace which transfers 20% of the body's weight from the foot to the knee. This will allow the area to fill in with new bone and prevent collapse.” Patients must take this part of their recovery quite seriously.  Dr. Nunley cautions, “the most important thing is that you don't put weight on it and cause it to fracture before it has a chance to get strong again.”

 

Dr. Nunley's recent breakthrough in developing an operation to allow vascularized bone grafts in the talus and ankle is very exciting and welcome news to many patients suffering from avascular necrosis of the talus and ankle. With 15 cases showing positive results and no failures after two years, the future of this procedure is looking very bright and may soon be proven as a possible cure for avascular necrosis of the talus. Also, as Dr. Nunley pointed out, patients with avascular necrosis of the hip and wrist may already be able to benefit from proven vascularized graft techniques. Thanks to innovators and dedicated researchers like Dr. Nunley, these recent technological and medical breakthroughs in bone graft surgeries are definitely a positive step forward towards developing cures for avascular necrosis.

 

 

Dr. James A. Nunley is the Director of the Foot and Ankle Training Program at Duke University Medical Center in Durham, NC.  He is also Chairman of the Orthopaedic Department at Duke and is a Professor of Orthopaedic Surgery.  Today, Dr. James A. Nunley is considered one of the foremost experts in the field of orthopedic surgery of the foot and ankle.  Please see his complete profile for practice and contact information.

 

Article Author
Jason WIlloughby

 

[1] James R. Urbaniak, M.D. and Julian M. Aldridge III, M.D., “Free Vascularized Fibular Graft Patient's Handbook”, Duke University Health System.