Orthopedic Case Study

Filling the Gap: Distraction Osteogenesis

The Patient

Brody and Drs. Agnello and CioffiWhen Stuart Shapiro went to pick up his new puppy at an Amish farm in Harrisburg, he thought something wasn’t quite right. Brody had a slight limp. The farmer told Stu it wasn’t out of the ordinary, that puppies often tumble and twist as they go through their first few weeks, learning to walk and play with the rest of the litter. He would be fine. Young dog and soon-to-be owner bonded immediately and Stu took his new skinny, black puppy home, trusting all would be well.

Brody, who was underweight, but otherwise pretty healthy, moved from a bed of hay in a barn to urban life in the Rittenhouse Square section of Philadelphia. With a healthy diet and plenty of play time, Brody followed his new human everywhere, including the office. His was a happy canine life – except for a lingering problem with his right foreleg.

Read Brody's story to see what happened...

The Surgeon

Kim Agnello, DVM, and RosieKim Agnello, DVM, DACVS

Dr. Kim Agnello, assistant professor of surgery at Penn Vet, completed her DVM from Cornell University College of Veterinary Medicine.

The Problem

In both dogs and children, the long bones in the legs and arms grow from an area at either end of these bones called the physis, or more commonly, the growth plate. These areas produce new bone tissue and determine the final length and shape of bones in adulthood. When growth plates close prematurely, which can either be hereditary or the result of a trauma, the bone is unable to achieve its normal length.

As a result of Brody’s incongruent elbow joint, he was bearing the majority of his weight through his ulna bone. The ulna is not equipped to handle full weight-bearing forces, and at less than one year of age, Brody had already developed osteoarthritis and pain in his elbow joint. To decrease Brody’s pain, improve his limb function, and prevent further injury, Drs. Agnello and Cioffi strongly recommended surgery.

The Solution: Distraction Osteogenesis

The surgical team, comprising Dr. Kim Agnello, supervising surgeon, Dr. Adrienne Bentley, and Dr. Krista Cioffi, recommended a procedure called distraction osteogenesis, a less traditional and more technically challenging approach than the typical surgery that involves bone cuts and internal fixation using bone plates.

Distraction osteogenesis in dogs was first described by the University of Pennsylvania School of Veterinary Medicine's Drs. David Nunamaker, Charles Newton, and C.R. Dickinson in 1975 (Newton CD, Nunamaker DM, Dickinson CR: Surgical management of radial physeal growth disturbances in dogs. J Am Vet Med Assoc 167;1011, 1975).

This procedure is a way to lengthen the limb that involves:

  • Breaking the bone and applying an external fixation device around the limb
  • Periodically adjusting the external device setting over the course of several weeks, thereby causing the bone segments to gradually move apart from one another

This technique of moving the two segments of a bone slowly apart in a controlled manner allows for new bone to fill in the gap and make the bone longer.

This surgical approach has been successfully used in children with abnormalities of their growth plates and in maxillofacial surgery. Although distraction osteogenesis cases have been reported in canine patients, since it is a complicated technical procedure, it is not common in veterinary surgery.

The Surgery

Brody’s surgery was performed using minimally invasive surgical techniques. 

  • The first part of the surgery involved arthroscopy, where “key hole” incisions are made into the elbow joint and surgery is performed via a small camera and instruments. This was done to remove bone fragments and scar tissue that was filling the space where the radial bone was missing.
  • Then an osteotomy (cut in the radial bone) was created and an external fixator device was placed on Brody’s limb using a c-arm or fluoroscopy. Fluoroscopy is a way of performing intra-operative x-rays to minimize surgical incisions and allow for precise placement of the external skeletal fixator.   
  • The distraction, or bone lengthening, started three days after surgery.

Brody's Short Radius Bone: The Gap

XRay of Brody's limb

Figure 1. X-rays of Brody’s right limb showing the short radius bone and the gap in the elbow joint (yellow arrow).

External Fixation Device

External skeletal fixatorFigure 3.  Brody’s limb showing the placement of the external skeletal fixator and the post-operative x-ray showing the osteotomy (yellow arrow) in the radial bone.

Surgery: Placing the Device

Placing the device on BrodyFigure 2.  Intra-operative image of the external skeletal fixator device being placed on Brody’s limb to allow for distraction osteogenesis.

The Outcome