QI have a 10-month-old Boykin spaniel named Lilly. She recently suffered a broken elbow, which required surgery to repair. The odd thing was that she was just running on a golf course when it happened. No real reason was apparent, to me, that would explain a broken leg. This repair was expensive and she is still not quite right on the leg. Why did this happen, and do I need to be concerned about the other legs?
A: Lets start with basic anatomy. The bone that forms the top of the elbow joint is called the humerus. The end of that bone that reaches the joint is called the humeral condyle. This condyle is divided into lateral (outside) and medial (inside) parts, which contact the lower two bones of the joint. These two parts share the load of weight bearing.
In growing puppies, these separate parts of the condyle fuse together by about 12 weeks of age. Until this happens, they are joined only by a layer of cartilage. This situation is inherently weaker than solid bone, therefore, puppies are at increased risk for this type of fracture. We frequently treat puppies that have been dropped, or have jumped off the bed, and sustained elbow fractures.
Puppies are not the only ones at risk. There is a condition known as incomplete ossification of the humeral condyle (IOHC), which has been documented in many pure breeds as well as mixes, but is most prevalent in spaniel breeds. The problem is that the two sides of the condyle never completely fuse together. Like young puppies, adult dogs with IOHC are also prone to elbow fractures.
This condition is genetic, as evidenced by its concentration within certain breeds. Its mode of inheritance appears to be through a recessive gene since there is an increased incidence among inbred populations. This means that even though both parents are unaffected, they could produce affected puppies, or genetic carriers.
Interestingly, the American Cocker spaniel has a high prevalence, while it is rare in the English Cocker. The English Springer is at particularly high risk of being affected. This also appears to be a sex-linked trait, with males being affected 69 percent to 83 percent of the time.
When fractures occur as a result of IOHC, they are generally spontaneous. Studies indicate that up to 80 percent of cases have no history of trauma.
In spaniel breeds, approximately 75 percent of all humeral condylar fractures have no history of trauma. These fractures are generally due to IOHC, and these patients, which include the dog in question, have IOHC on the opposite limb 85 percent of the time. Worse yet, 25 percent of these dogs will fracture the opposite leg within 8 months.
Given that the odds are so great that the other elbow is affected, it should be routinely evaluated whenever an adult dog has a spontaneous condylar fracture.
If it is proven to be affected, it may be treated by placing a screw across the condyle. This is a simple procedure, which may be performed on an outpatient basis, or at the same time as the repair for a fracture on the opposite limb.
The treatment after the condyle has fractured is technically demanding and requires near perfection if a good outcome is to be achieved. The bone must be perfectly aligned to re-establish the joint surface, otherwise abnormal wear and severe arthritis will result. The implants are placed in a very small area, leaving little tolerance for positioning.
If the alignment and implant placement are excellent, near normal function may be regained. Some arthritic changes may still develop after repair and completely normal function may not be achieved. This is why identifying and treating this condition before a fracture occurs is important, and why breeders of at-risk breeds need to be vigilant in monitoring for, and excluding from the breeding program, affected individuals and potential carriers.
If you are purchasing a spaniel breed, discuss this condition with the breeder, and know that should your dog be affected, any guarantees of genetic soundness should cover this condition as well.