Elbow incongruity is a form of hereditary elbow dysplasia that causes disturbance in the growth of the long bones in the forelimbs. Elbow incongruity causes osteoarthritis, pain, and lameness, and it is common in chondrodystrophic breeds which are typically short-legged and have a long body. Typical chondrodystrophic breeds include Dachshunds, Corgis, Skye Terrier – and Irish Glen of Imaal Terrier.
Elbow incongruity
Bone growth occurs at the cartilaginous growth plates. When the growth plates close, the growth of the bone stops. The dwarfed legs of the chondrodystrophic breeds is a result of the termination of long bone growth in the limbs. In these breeds, the bones of the limbs are also thicker and more bowed than normal. In some cases, the growth of the ulna, one of the two long bones in the foreleg, stops prematurely (PCDUP, premature closure of the distal ulnar physis). While the other long bone, the radius, continues to grow, the result is uneven growth of the two long bones and, furthermore, bad alignment of the joint surfaces of the elbow i.e., elbow joint incongruity (INC). In some dogs, the disorder may lead to outwards bent paws and inwards bent wrists. Elbow joint incongruity has been associated with puppy lameness, which in severe cases, continues also in adulthood. Over time, elbow incongruity leads to osteoarthritis in the elbow joint. As premature closure of the growth plates in ulna is hereditary in chondrodystrophic breeds, its occurrence can be influenced by breeding choices.
Screening of Elbow incongruity
Hereditary growth disorders of the elbow joint in dogs are examined by using X-rays. Typically, X-rays are taken according to the recommendations of the International Elbow Working Group (IEWG), and the degree of elbow dysplasia is classified using the IEWG International Rating Scale. However, this method is not suitable for chondrodystrophic breeds because it does not assess incongruity at all. Therefore, a novel screening protocol has been developed for short-limbed breeds (Lappalainen et al. 2016), in which incongruence is assessed on a scale INC0 – INC3 (INC0 is no incongruity and INC3 severe incongruity in the joint). In chondrodystrophic breeds, INC1 can be considered “normal,” but the INC2 and INC3 elbow joints are clearly abnormal. Breed-specific breeding recommendations can only be made once enough dogs have been examined. However, the general recommendation from the researchers who developed the method is that dogs with INC2 and INC3 joints should only be combined with dogs with INC0 or INC1 joints.
The Finnish Kennel Club has begun storing official INC statements on 01.01.2021
For a few years now, informal INC statements have been given in the OC- and INC-statement service (“INCOC”) by Associate professor Anu Lappalainen, Veterinarian, Specialist in Small Animal Diseases, and Vilma Reunanen, LVM, Veterinarian, Specialist for Small Animal Diseases. At the end of 2020, the Finnish Kennel Club finally announced that it would begin storing INC statements in its database, i.e., giving the elbow incongruity examination and statements an official status. The Kennel Club has started organizing the INC-statements on 1 January 2021 and the statements will be displayed in the Kennel Club’s open KoiraNet breeding database. INC statements given earlier in the INCOC service can be transferred to the Kennel Club’s breeding database at the owner’s request from the end of January 2021. The Kennel Club will provide more detailed instructions later.
In accordance with the Finnish Kennel Club’s Elbow Growth Dysplasia Examination Guideline, certain chondrodystrophic breeds (Irish Glen of Imaal Terrier included) has no longer been given an official IEWG-compliant elbow joint dysplasia statement as of 01.01.2020.
Sources:
Lappalainen, AK. 21.4.2018: Elbow incongruity (in Finnish) https://www.incoc.fi/kyynarnivelen-inkongruenssi/ (06.01.2021).
Lappalainen AK., Hyvärinen T., Junnila J., Laitinen-Vapaavuori O. Radiographic Evaluation of Elbow Incongruity in Skye Terriers. J. Small. Anim. Pract. (2016) 57: 96-99.
The Finnish Kennel Klub News 09.12.2020: Storing of osteochondrosis of the shoulder joint and forearm incongruity statements in dogs with short limbs begins in the breeding database (in Finnish): https://www.kennelliitto.fi/tietoa-meista/uutiset/olkanivelen-osteokondroosi-ja-matalaraajaisten-koirien-kyynarnivelen-inkongruenssilausuntojen-kirjaaminen-jalostustietojarjestelmaan-alkaa (06.01.2021).
The Finnish Kennel Klub: Guidance on radiography and classification of growth disorders of the elbow joint. Valid from 1.1.2021 (in Finnish) https://www.kennelliitto.fi/en/media/4637