Presentation
Presented with 6 weeks of lameness of the left front limb.
Patient Data
The left elbow is luxated with the radius and ulna positioned cranial and lateral to the humerus with rotation. The trochlear notch of the ulna is partially formed but shallow. The radial head is also abnormal in shape; however, the physis is visible. The humeral condyles are smaller compared to the normal right limb.
Left elbow luxation.
Case Discussion
These luxations in young dogs are often called congenital elbow luxations because of the arrested development of the components of the elbow. Bone forms according to the forces placed on it, and if they are not normal, such as the trochlear groove of the ulna and the condyles in apposition, none of the bones form in the expected manner.
Congenital usually refers to something that occurred in utero. Congenital luxations that do form in utero may be expected to be missing components of the involved bones. Those that result from trauma at birth or shortly after will have more normal looking bones that lack normal development. Unfortunately it is often difficult to pinpoint when such a trauma might have occurred, in order to relate it to the radiographic signs.
There are three types of elbow luxation in dogs. The most common type is luxation of the humeroulnar joint with lateral rotation. The radial head may also be involved. This type, as illustrated in this case, occurs in small breed dogs.
The second type of congenital elbow luxation is lateral or caudolateral luxation of the radial head, while the ulna remains in a normal position. The third type occurs with general laxity of the elbow, along with multiple other congenital abnormalities such as ectrodactyly, patellar luxation and hydrocephalus.
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