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| Fragmented coronoid process is the third
developmental condition that affects the elbows of large and giant breed dogs,
particularly retrievers, Rottweilers, mastiffs, Burnese Mountain dogs, and German shepherd
dogs. The etiopathogenesis of this condition is controversial. Fragmented coronoid process
was initially believed to be a manifestation of the osteochondrosis complex; however,
pathoanatomic studies have not fully supported this contention. |
 Histologic
section through a fragmented coronoid process. Note the thickening of the articular
cartilage suggestive of osteochondrosis is not evident.
|
 Fragmented
coronoid process (circle) in a dog with distal radiohumeral subluxation which was
secondary to premature closure of the distal radial physis. |
 Normal
proximal articulation of the radius and ulna. |
 Distal
radioulnar subluxation would place increased load on the medial coronoid process (circle).
|
| Fissures or fragmentation may result from abnormal stresses
placed on the developing coronoid process secondary to conformational abnormalities of the
elbow. Distal radioulnar subluxation is a purported cause of an increased load being
placed on the medial coronoid process. The medial coronoid process is most often involved.
The disease is more common in male dogs and is often bilateral. Injury to the distal
radial physis in skeletally immature dogs may also result in distal radiohumeral
subluxation as the ulna continues to grow with subsequent fragmentation of the coronoid
process. |
 Disarticulated
elbow with a fragmented coronoid process (circle) and degenerative joint disease. |
 Typical
posture of a Rottweiler with fragmented coronoid process. Note the external rotation of
both forelegs. |
Clinical signs are rarely noted before five months of age.
Subtle weight-bearing lameness, exacerbated by prolonged rest or exercise, is typical. The
onset of lameness is insidious. As lameness persists, it may increase in severity.
Affected dogs often place the carpus in an exaggerated valgus position when sitting or
standing and circumduct the antebrachium during the swing phase of the stride. A pain
response is usually not elicited unless the elbow is fully extended. Some investigators
suggest that the carpus should be placed in a flexed, externally rotated position while
the elbow is extended. Joint effusion may be detected as a fluctuant swelling beneath the
lateral epicondyle of the humerus. |
| The fragmented coronoid process is rarely
identified radiographically because of superimposition of the medial coronoid process and
the head of the radius. The mediolateral (extended and supinated) view made with the elbow
maximally extended and supinated 15° reportedly is a superior radiographic projection for
demonstrating pathology of the medial coronoid process; however, we have not found this
view to be useful for specific identification of coronoid pathology. Although the pronated
oblique, craniocaudal view is more useful for specific identification of medial coronoid
pathology, the percentage of cases in which a specific fragment can be identified is still
limited. |
Pre
and Post Operative Radiographs of a Dog with Fragmented Coronoid Process |
 A. Craniocaudal view radiographs of a
dog's elbow with a fragmented coronoid process. Although degenerative changes are evident
(circle) the fragment can not be visualized. |
 B. On the oblique view radiograph the
fragment can be seen (box). The insert (circle) is a radiograph of the excised fragment. |
C. Postoperative radiograph
demonstrating that the fragment has been removed.
|
| When fragmentation of the coronoid process can
not be identified radiographically, a clinical diagnosis of fragmented coronoid process is
supported by the presence of degenerative changes in the elbow in the absence of an
ununited anconeal process or osteochondrosis of the humeral condyle. Osteophyte
development on the anconeal process and increased density of the ulna subjacent to the
coronoid process and the trochlear notch are early radiographic degenerative changes
associated with fragmented coronoid process. Degenerative changes are usually not
radiographically evident before seven months of age. Distal radiohumeral subluxation, a
purported etiology for fragmentation of the coronoid process, may be apparent in some dogs
before degenerative changes are apparent.
|
Radiographs
of Both Elbows of a Dog with a Unilateral Fragmented Coronoid Process. |
  The
left elbow (a) is normal, while the only degenerative change evident in the right elbow
(b) is sclerosis subjacent to the semilunar notch. |
 |
Lateral view radiograph of a two year old Labrador
Retriever with advanced degenerative joint disease secondary to a fragmented coronoid
process. |
| Definitive diagnosis of fragmented medial
coronoid process is made at exploratory arthrotomy or via arthroscopy. Again some
veterinary surgeons are successful diagnosing and removing fragmented coronoid processes
using arthroscopy. If a standard surgical arthrotomy is done, the medial coronoid process
is exposed via the previously described muscle separating approach. Experience and
adequate lighting facilitate definition of the pathology. |
| In some dogs, a free fragment exists and is readily
identified and removed. In other dogs, only fissuring of the articular cartilage is
present. These fissures can extend variable depths into the subchondral bone. These
lesions can be difficult to recognize and confusing. Probing the articular surface of the
medial coronoid process with a Freer periosteal elevator can help identify fissures that
are not readily apparent. Although optimal treatment of these fissures has not been
determined, we generally excise the affected region as if it were a fragment. |
 Disarticulated
elbow of a dog win an obvious large fragmented medial coronoid process (circle).
|
 Surgical
excision of a fragmented medial coronoid process (box) via a medial arthrotomy. |
 Disarticulated
elbow of a dog with a fissure (arrow) of the medial coronoid process
|
| Postoperative care depends upon the approach
that was used at surgery. A soft padded bandage is applied to the affected limb for three
to five days following surgery. If an osteotomy of the medial condyle or a desmotomy of
the medial collateral ligament was performed, strict kennel confinement and limited
activity on a leash is recommended for 4 to 6 weeks. If the medial collateral ligament was
simply retracted and an osteotomy or desmotomy was not performed, 2-3 weeks of confinement
and leash activity is sufficient. Gradual return to activity is recommended over the
subsequent 4 weeks. The prognosis for dogs with fragmented coronoid process is again
guarded. The benefits and efficacy of surgery, and for that matter arthroscopy, for dogs
with fragmented coronoid process is a contentious issue. Although degenerative joint
disease progresses irrespective of whether or not surgical intervention is done, most dogs
will eventually become sound with a slightly stiff, stilted gait. Although studies
disagree regarding the benefits of surgery, surgical excision of fragmented coronoid
process in young dogs seems to result in a more rapid improvement of lameness. Surgery,
however, does not seem to benefit dogs older than 18 months. Despite the continued
progression of degenerative joint disease, most dogs regain sufficient limb function to be
functional pets. Medical management may be necessary to optimize the dog’s comfort
and function. Some dogs can return hunting, obedience and field trail work; however,
lameness should be expected with vigorous activity. |
