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14.9 Ununited Anconeal Process 209

14.8 Osteochondrosis Dissecans

Osteochondrosis/osteochondritis dissecans (OCD) of the elbow joint affects the medial humeral
condyle (trochlea). In contrast to OCD lesions of other joints, elbow OCD is frequently diagnosed
together with MCD. Similar to OCD lesions in other joints, OCD of the elbow is the consequence
of an endochondral ossification failure resulting in excessive thickness of the cartilage that may
detach (and develop a flap). Cartilage pathology affecting the trochlea may also develop secondary
to a mismatch between the humerus and ulna, as well as from erosion from the opposing coronoid
pathology. Such lesions are termed “kissing lesions” and can be difficult to distinguish from true
OCD lesions in some cases (Cook and Cook 2009). Although OCD of the elbow can sometimes be
identified with radiography, most often CT (Figure 14.5) or arthroscopy is used to establish a final
diagnosis. The use of these technologies also allows to identify concurrent incongruity and
coronoid pathology. Because the prognosis for elbow OCD is questionable, treatment is somewhat
controversial, with most authors recommending surgical debridement of the lesion (and address-
ing concurrent elbow pathology if indicated).

14.9 Ununited Anconeal Process

Failure of fusion of the ossification center of the anconeal process is defined as UAP. The patho-
physiology of UAP is unclear, but premature distal ulnar physis closure frequently results in UAP ELBOW REGION
indicating that radioulnar incongruity may play a substantial role. Ossification of the anconeal
process should be completed by 20 weeks during normal development, although fusion frequently
occurs earlier. UAP has been reported to occur together with MCD in 16% of the cases (Meyer-
Lindenberg et al. 2006). A wide variety of treatment options are available including ulnar osteot-
omy procedures, lag screw fixation, or removal of the anconeal process.

14.9.1 Signalment and History
Any large-/giant-breed dog is susceptible to UAP, especially German Shepherd Dogs, Bernese
Mountain Dogs, and Mastiffs. Nevertheless, even small dog breeds, including French Bulldogs and
Dachshunds, have been diagnosed with UAP. Animals with unilateral disease usually present
before they reach maturity. Bilateral disease, which is present in 20–25% of the cases, may make
the lameness harder to identify for owners and hence these animals may present later in life due to
advanced degenerative disease (Cross and Chambers 1997).

14.9.2 Physical Exam
Dogs with UAP generally have more obvious physical exam findings compared to dogs presenting
with MCD. Significant joint effusion is generally palpable, and pain is most evident with hyperex-
tension of the joint.

14.9.3 Diagnostics
In contrast to the other forms of ED, UAP is easily diagnosed with radiographs. If a lack of anco-
neal fusion is observed after 20 weeks of age, the diagnosis is confirmed (Figure 14.8). The flexed
lateral radiographic view (Figure 14.8A) eliminates superimposition of the anconeal process and