Proper treatment of distal radius and ulnar fracture in toy breeds: the answer is surgical.

Toy breed dogs are known to be jumpers. Unfortunately between jumps, falls and drops, these dogs are prone to fractures of the forelimbs, specifically the distal radius and ulna. Typically, splinting of these fractures fails and here is why:

Toy breeds just as Poodles, Pomeranians, Yorkies, Chihuahuas enjoy jumping to and from the couch, chairs etc. Perching atop the couch and then diving off at a moments notice is typical behavior. Add to that, the jumps out of owners arms and the delicate bone structure and you have the tendency to fracture. The distal radius and ulna typically take the most impact leading to fracture. Fractures generally occur just proximal to the distal physis, leaving little room for fixation. This situation might push one to suggest splinting; however, the outcomes of splinting are poor due to variations in anatomy in these toy breed dogs.

Fractures of small and toy breed dogs tend to occur in the distal one-third of the diaphysis. The blood supply of this region is diminished in small breed dogs (Figure A) compared to large breed dogs (Figure B). The literal density of blood vessels is dramatically less in small breed dogs. (Figure A) Small breed dogs must rely on the nutrient artery more than large breed dogs for local blood supply.

Figure A: This is an image created of the blood supply of the distal radius in a young Jack Russell Terrier. The black arrow is placed where blood supply is significantly diminished relative to large breed dogs (figure B below). (Courtesy of Veterinary Surgery 26: 57-61 1997, Janet Welch et al)

Figure B: This is an image created of the blood supply of the distal radius in a young large breed dog. The white arrow is placed where blood supply is very dense and extensive compared to the above pictured small breed dog (figure A). (Courtesy of Veterinary Surgery 26: 57-61 1997, Janet Welch et al)

The significance of this diminished blood supply is that without rigid internal fixation, nonunions and delayed unions occur. There must be essentially no motion at the fracture site so that the nutrient artery can cross the fracture and provide blood supply. In a large breed dog with significantly more blood supply distally, external fixation tends to have a more favorable outcome.

With the knowledge of this anatomy, veterinarians can better guide their clients to pursue surgery in these fractures. Finances always play a role in this decision; however, this is a time when surgery is critical. Patients can be splinted until finances are procured. Ideally surgery is performed sooner (days) rather than later (weeks), both both time frames can lead to positive outcomes if surgery is pursued.

Immediate internal fixation is ideal for maximal and expedient healing. An appropriately sized bone plate is applied to the dorsal surface of the radius. Fixation of the ulna is not necessary. A T-plate is commonly used to maximize the amount of screws that may be placed distally on the radius. Ideally three screws are placed on either side of the fracture; however many cases only have room for 2 distally, still resulting in positive outcomes with proper activity restriction during healing. For the first two weeks, a splint may be placed in precarious cases e.g. those with only 2 screws or previous non-unions that required grafting etc.

Figure C: This is a malunion/delayed union fracture of a 9mos old FS Yorkshire terrier. This fracture had been splinted due to lack of finances. Although some attempt at union can be noted, the distal portion of radius and ulna (and paw) is rotated 90degrees from normal resulting in an attempted partial malunion. Additionally motion could be felt at the fracture site. Note the marked osteopenia of the distal components of the forelimb fracture. This dog also had marked laxity of the carpus from being splinted for 9 weeks.

Figure D:

This is the craniocaudal view of the distal radius and ulna fracture in the 9 month old Yorkshire terrier that was splinted for 9 weeks due to the financial constraints of the owner. Note the blunted fracture ends and marked osteopenia (loss of bone density) of the bones distal to the fracture site. Motion could be felt at the fracture site allowing rotation at the level of the fracture.

In this case due to the very small size of the dog (2.5kg), a very small bone plate was selected (1.0mm 2X5 hole). Vetimplants.com

Figure E: This is the immediately post operative view (lateral) of the repaired fracture. In this case, using an oscillating saw, the blunted fracture ends were cut to encourage bone healing and improve alignment.

A 1.0mm bone plate was applied to this 3kg dog. It is important to have an appropriately sized implant. The ideal implant provides enough support to promote bone healing but not excessive support which would create stress protection and require plate removal eventually and potentially prevent complete bone healing.

A bone graft was placed (cancellous bone graft VOI).

Figure F: A cancellous bone graft was applied using bone putty (veterinary orthopedic implants—vetimplants.com). This provides convenience, saving time in harvesting for an autogenous bone graft (e.g. proximal humeral), not to mention morbidity of site harvest.

Figure G: This is the immediate post operative craniocaudal view of the distal radius and ulna fracture. Note the refreshed bone ends. Criticism: there would ideally be 3 screws above and below the fracture site. In this case, the most proximal screw was not placed due alignment issues. A splint was placed for this reason and to support the repair for a short time to allow the bone to start to bridge. The splint was placed for two weeks to give bone bridging a head start. There after, a soft bandage was placed to destabilize the region gradually and give the lax soft tissue structures support prior to taking off the bandage completely at 4 weeks post operatively. Radiographs were taken at 4 weeks to verify removal of the soft bandage and 8 weeks for final bone union documentation.

And here, is the lovely patient in all her glory!!