May 16, 2014 - Oral surgeons at the University of California, Davis School of Veterinary Medicine have recently increased the scope of their novel jawbone regrowth surgeries, taking the next step to advancing this procedure. The two dozen previous procedures have been on regenerating a variable size section of the side of the jawbone. UC Davis is now able to increase the regrowth area to include the front arch (chin area) of the jaw. As long as there is enough healthy bone remaining on the rear of the lower jaw on each side of the mouth, a reconstruction of nearly the entire lower jawbone can be performed. This latest advancement has now been successfully performed on three dogs in the past year.
Background on the Surgery
In 2011, professors Frank Verstraete and Boaz Arzi, both oral surgeons at the School’s Veterinary Medical Teaching Hospital (VMTH), started refining the treatment of dogs that had lost sections of their jawbones due to injuries or removal of cancerous tumors. Using cutting-edge biomedical technology, the veterinarians collaborated with UC Davis biomedical engineers—along with a generous donation of materials from Medtronic—to regrow segments of the jawbone.
During the reconstructive surgery, Drs. Verstraete and Arzi, from the VMTH’s Dentistry and Oral Surgery Service (DOSS), remove loose bone fragments from an injured area or a full section of the jawbone from a cancerous area. The surgeons then screw a titanium plate into place on the remaining bone on each side of the removed area. A sponge-like scaffolding material, soaked in a bone growth promoter known as bone morphogenetic protein, is then inserted into the space where the bone was removed. The growth-promoting protein stimulates remaining jaw bone to grow new bone cells, eventually filling the entire defect and integrating with the native bone.
On a radiograph (x-ray), the formation of new bone can be detected by two weeks post-surgery. By four to six weeks, the majority of the defect is filled in with new bone. By eight to 10 weeks, the new bone is fully formed and integrated with the native bone, forming one continuous mandible. The procedures to date have all been successful.
Advancing the Procedure
One of the lucky recipients of the latest advancement of this procedure is Hoshi, a 10-year-old female collie from Montana. Hoshi’s owner, Katy Harjes, noticed swelling and unusually bad breath in Hoshi’s mouth in the summer of 2013. Her local veterinarian in Montana diagnosed squamous cell carcinoma and removed some diseased bone from the front of Hoshi’s mouth. However, Hoshi would need more treatments beyond what was available in Montana. Research turned up the option of taking Hoshi to UC Davis for treatment, so Katy called the world-renowned veterinary facility to discuss. She soon found herself on a 15-hour roadtrip, with Hoshi in tow, to California.
After arriving at UC Davis and meeting with veterinary oncologists to discuss treatment options for Hoshi, Katy was told of DOSS’ procedure and introduced to the oral surgeons. Squamous cell carcinoma is one of the most common oral tumors in dogs so DOSS was familiar with the surgical removal, and confident that a recent advancement of their bone regrowth surgeries could reconstruct the front part of Hoshi’s jaw. DOSS had recently performed the first front arch mandible reconstruction with success, and the two dozen other bone regrowth surgeries were enough to convince Katy that bringing Hoshi to UC Davis was the right course of action.
“Once they told us about the surgery, we were on board immediately knowing the success rate,” said Katy. “It seemed too good to be true, so of course we were very excited and grateful for the opportunity.”
3D Printing Technology
VMTH oncologists examined Hoshi and found that the cancer had not metastasized into her lungs or other areas. A CT scan confirmed that removal of the entire front part of the jawbone (extending back on both sides of the mouth) was necessary to completely remove all the effected tissue. From the CT scan, UC Davis Biomedical Engineering TEAM facility printed a 3D model of Hoshi’s skull to help DOSS surgeons plan the surgery.
Using the 3D printed skull, the surgeons were able to contour and fit the titanium plate needed to form Hoshi’s new jawbone before the surgery. This preparation shortens the surgery time, creating a safer environment for any animal under anesthesia. Following the procedure, another CT scan showed that Hoshi’s plate was placed properly and had conformed well to her remaining jawbone.
A Successful Reconstruction Surgery
Radiographs of Hoshi’s jaw at about a month post-surgery showed her jaw to be stable and firm, with new bone formation. While Hoshi was still having trouble picking up food or toys, there was no evidence of loss of integrity or mobility of the jaw. With less nerve endings in the front of her mouth, Hoshi would need time to adjust to her new jaw. Katy took Hoshi back to Montana, confident that this would come in time.
One technique Katy employed to help Hoshi adjust was to “bench feed” her. Once Hoshi was able to eat on her own, having the food elevated on a bench made it easier for her to keep the food in her mouth. Slowly, Hoshi adjusted to the feel of her new jaw and resumed biting and chewing on her favorite toys.
Six months after the surgery, Katy and Hoshi made the 15-hour drive back to UC Davis for a recheck examination. Her CT scan showed bone regrowth throughout the entire front arch of the jaw, and surgeons were pleased with the progress of the healing. Hoshi was returning to her normal self.
Katy and Hoshi returned to Montana where they live on a sheep ranch with 11 other dogs, some house pets like Hoshi and some working dogs for the sheep herd.
“Hoshi likes to think she’s in charge of everyone,” said Katy. “We are so grateful to UC Davis that she has returned to her role of ‘Boss Girl’ on the ranch.”
Click here for more photos of Hoshi