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Elbow Dysplasia _ED_


									 Elbow Dysplasia (ED)
     Peter Sebestyen, DVM
   Diplomate American College of
        Veterinary Surgeons

  Veterinary Surgical Specialists of
           Orange County

Elbow dysplasia (ED) is a common cause
of thoracic limb lameness in young large
–breed dogs. The term elbow dysplasia is     Arthroscopic view of a fragmented coronoid process
now commonly used to represent a group
of conditions affecting the elbow joint
including fragmented medial coronoid         gested as a potential cause of the fragmentation
process (FCP), osteochondritis dissecans     (Olsson 1993). Results obtained from histologi-
(OCD) of the medial aspect of the hu-        cal analysis of removed coronoid fragments
meral condyle and ununited anconeal          from clinical cases seem to have refuted this
process (UAP) (Schulz and Krotscheck         idea. Not only there was no evidence of osteo-
2003). Other less common abnormalities       chondrosis, but the changes were more consis-
such as ununited medial epicondyle are       tent with fibrous non-union indicating fatigue
also included by some authors (Walker        fractures of the medial coronoid process
1998).                                       (Guthrie et al 1992). A more recent paper de-
         The FCP appears to be the most      scribed histomorphometric analysis of medial
common form of ED and usually is seen        coronoid fragments removed via subtotal coron-
as an isolated condition, however, less      oid ostectomy and found that the morphological
commonly it is combined with ununited        changes most consistent with a non-healed os-
anconeal process or osteochondrosis dis-     teochondral fracture (Danielson et al 2006).
secans of the humeral condyle. The                   The advent of veterinary arthroscopy
etiopathogenesis of the FCP is not fully     provided tremendous incite into the medial
understood. Theory of an ununited me-        coronoid pathology. Arthroscopic evaluation of
dial coronoid was proposed initially simi-   elbow joint from clinically affected dogs re-
larly to UAP (Olsson 1974). Later it was     vealed significant cartilage changes despite of
discovered that the medial coronoid de-      negative radiographic findings (Schulz 2003).A
velops from the same ossification centre     classification scheme was suggested to stan-
as the rest of the proximal ulna. (Guthrie   dardize the description and severity of these
et al 1992).Osteochondrosis of the me-       changes in an attempt to compare different co-
dial coronoid process has also been sug-
hort of dogs with elbow disease. A number             years. Smaller amount of supraphysiologi-
of cartilage changes have been described              cal load on the medial compartment may
including chondromalacia, fibrillation, fis-          not result in fragmentation, instead it
suring of the cartilage, non-displaced frag-          causes erosive lesion as it was seen in the
mentation, displaced fragmentation, synovi-           above study. If the degree of compressive
tis and frictional abrasion of the opposing           stress is more severe and/or presents earlier
medial aspect of the humeral condyle                  in life, it will lead to development of large
“kissing lesion”. Furthermore, some of the            fragment as it is seen in the typical mani-
clinically lame patients had significant carti-       festation of the disease in younger dogs.
lage changes including severe “kissing le-                     The focal increase of mechanical
sion” without the presence of any fragment.           load at the medial joint compartment is
Based on these clinical observation obtained          thought be caused by incongruency. Four
from elbow arthroscopy, the term of medial            basic theories have been advocated. The
compartment disease (MCD) was suggested               first concept suggested bicentric concave
as better description of this specific elbow          humeroulnar incongruency. The radius of
pathology. It appears that the classic form of        curvature of the ulnar trochlear notch is
FCP with a displaced large fragment sepa-             reduced comparison to the radius of curva-
rated form the medial coronoid process                ture of the humerus. This will result in a
represents only one specific lesion on a              smaller curvature of ulnar notch not fitting
much wider spectrum. Recent clinical study            around the humeral condyle and placing
described arthroscopic and imaging findings           stress on the medial coronoid region (Wind
in 51 dogs six years and older with elbow             et al 1986). This theory was supported by
lameness (Vermote et al 2010). The distri-            radiographic studies showing a decreased
bution of the lesions affecting the medial            radial curvature in breeds predisposed to
coronoid region was significantly different           FCP. Another, perhaps more popular con-
from the lesions found in younger dogs.               cept advocates radioulnar incongruency
Older dogs had mainly cartilage and sub-              (RUI) resulting asynchronous growth be-
chondral bone damage without overt frag-              tween the radius and ulna. There are two
ments as opposed to displaced fragment was
the predominant findings in younger dogs.
They concluded that medial coronoid dis-
ease is not uncommon in older dogs and the
most common lesions are medial compart-               •   Fragmented coronoid
ment erosions without macroscopic frag-
mentation of the medial coronoid process.             •   Ununited anconeal
These findings further support the idea of
medial coronoid disease has a wide spec-
trum. The older dogs seem to be on a dif-
ferent end of the spectrum. The direct cause
                                                      •   OCD of the humeral
of the osteochondral fatigue fractures on the             condyle
medial coronoid region is thought to be
caused by increased loading due to uneven             •   Incongruity (IC)
weight bearing. Whatever the exact mecha-
nism of this increased load, it may not cause
significant enough damage until several

variation of RUI can exist. Either the radius
(positive RUI) or the ulna (negative RUI)
ends up being shorter creating a stair step
at the radioulnar articular surface. Experi-
mental studies produced FCP in growing
beagles with radiation induced premature
closure of the distal radial physis. The re-
sulting short radius and relative long ulna
caused stress fracture on the medial coron-
oid process. In vitro study also supported
that the shorter radius relative to the ulna
will change the location and size of the ra-
dioulnar contact areas. Dynamic proximal
ulnar osteotomy restored the contact pat-
terns (Preston et al 2001). Short ulna was
proposed to be the cause of ununited an-                Un-united anconeal process
coneal process. The proximal displacement
of the radial head subsequently puts in-
creased pressure on the anconeal process        united and stable, this laterally applied up-
leading to failure to unite. Osteotomy of       ward force will create a downward rotation
the ulna allowed the AP to fuse in the ma-      of the condyle on the medial side using the
jority of patients with UAP in one reports      anconeus as fulcrum and causing increased
(Sjöstrom et al 1995). The argument             load on the medial coronoid surface (Lozier
against these theories is a general clinical    2006). However, this model still does not
observation about the lack of obvious RUI       provide convincing explanation for the fact
at the time of diagnosis of MCD. Also, the      that RUI or HUI are not always present at
fact that FCP and UAP can coexist, makes        the time of diagnosis of MCD.
it difficult to explain with a simple length            Whatever the specific mechanism
discrepancy between the radius and ulna         (RUI, transient incongruency, dynamic in-
(Meyer-Lindenberg et al 2006). Further-         congruency, altered weight bearing axis) is,
more, the clinical experience suggests that     it ultimately leads to a focal increase of me-
the short ulna syndrome is much more            chanical stress on the medial elbow joint
common in patient with FCP than the short       compartment. Plenty of evidence supports
radius (Lozier 2006). It has been proposed      the theory that MCD results from focal wear
that the incongruency either transient or       and tear of the cartilage and subchondral
only occurs in certain dynamic conditions.      structures. Several osteotomies were pro-
More complex model was suggested to de-         posed to alleviate the increase medial com-
scribe elbow joint incongruency trying to       partment stress. If the friction at the medial
explain why FCP could occur with either         joint compartment is not eliminated, just a
short radius or short ulna. This angular vec-   focal treatment of the coronoid (fragment
tor model (AVM) proposed that proximally        removal only) is unlikely to produce optimal
displaced radial head puts upward stress on     results due to continued damage at the area.
the lateral aspect of the humeral condyle.      More aggressive arthroplasty to lower the
As long as the anconeal process is already      joint surface of the MCP by motorized shav-
ing during arthroscopic procedures has been                  the cases in the second study. It was con-
advocated to ameliorate the effects of ‘‘medial              cluded that subtotal coronoid ostectomy is
compartment’’ pain associated with joint sur-                viable method for treatment of MCD even
face friction.                                               for cases without an obvious fragment. Both
        Subtotal coronoid ostectomy has been                 studies reported progression of osteoarthritis
described to treat MCD either via medial ar-                 on follow up even in the successful cases. A
throtomy (Puccio et al 2003; Fitzpatrick et al               potential disadvantage of coronoid ostectomy
2009) or with elbow arthroscopy with or with-                includes abnormal load distribution. No evi-
out concurrent ulnar ostectomy (Holsworth                    dence or consequence of the abnormal load
2006). Over 80% of these dogs were found                     distribution was reported. Arthroscopic sub-
sound on follow-up and only minimal compli-                  total coronoid ostectomy anecdotally pro-
cation was reported. The medial coronoid proc-               vides similarly good results.
ess was grossly intact in over 17 %, fissured in
over 18 % and fragmented in 64% of


Boulay JP. Fragmented medial coronoid process of the ulna in the dog. Vet Clin North Am Small Anim Pract
1998; 28: 51–74.

Danielson KC, Fitzpatrick N, Muir P, et al. Histomorphometry of fragmented medial coronoid process in dogs: A
comparison of affected and normal coronoid processes. Vet Surg 2006; 35: 501–509.

Guthrie, S., Plummer, J. M. & Vaughan, L. C. Post natal development of the canine elbow joint: a light and elec-
tron microscopic study. Research in Veterinary Science 52, 67-71, 1992

Guthrie, S., Plummer, J. M. & Vaughan, L. C. Aetiopathogenesis of canine elbow osteochondrosis: a study of
loose fragments removed at arthrotomy. Research in Veterinary Science 52, 284-291, 1992

Holsworth I: The role of sub-total arthroscopic partial coronoidectomy and concurrent distal ulnar ostectomy. Pro-
ceedings of the British Veterinary Orthopaedic Association. Autumn Scientific Meeting, Birmingham, UK, No-
vember 2006, p 30

Huibregtse BA, Johnson AL, Muhlbauer MC, et al: Theeffect of treatment of fragmented coronoid process on the
development of osteoarthritis of the elbow. J Am Anim Hosp Assoc 30:190–195, 1994

Lozier SM. How I treat elbows in the older canine patient and new prospectives in elbow dysplasia. In:13th ESVOT
Congress; 2006 Sep 7–10; Munich, Germany: 93–96.

Meyer-Lindenberg, A., Fehr, M, Nolte, I. Coexistence of ununited anconeal process and fragmented medial coron-
oid process of the ulna in the dog. Journal of Small Animal Practice 47, 61-65, 2006

Olsson, S. E. A new type of elbow dysplasia in the dog. A preliminary report. Svensk Veterinartidning. 5, 152-
157, 1974

Olsson, S. E The early diagnosis of fragmented coronoid process and osteochondritis dissecans of the canine el-
bow. Journal of the American Animal Hospital Association 19, 616-626, 1983.

Preston CA, Schulz KS, Taylor KT, et al. In vitro experimental study of the effect of radial shortening and ulnar
ostectomy on contact patterns in the elbow joint of dogs. A J Vet Res 2001; 62: 1548–1556.
Puccio M, Marino DJ, Stefanacci JD, et al: Clinical evaluation and long term follow up of dogs with coronoidec-
tomy for elbow incongruity. J Am Anim Hosp Assoc. 39:473–478, 2003

Punke JP, Hulse DA, Kerwin SC, et al: Arthroscopic documentation of elbow cartilage pathology in dogs with
clinical lameness without changes on standard radiographic projections. Vet Surg 2009

Read RA, Armstrong SJ, O’Keef D, et al: Fragmentation of the medial coronoid process of the ulna in dogs: a
study of 109 cases. J Small Anim Pract 31:330–334, 1990

Schulz KS, Krotscheck U.:Canine elbow dysplasia. In: Textbook of Small Animal Surgery (3rd ed.) Douglas Slat-
ter (editor). W. B. Saunders, Philadelphia; 2009: 1927–1952.

Schulz KS.: What’s new in elbow arthroscopy? ACVS Symposium 2003.

VermoteKA, BergenhuyzenAL, et al: Elbow lameness in dogs of six years and older. Vet Comp Orthop Traumatol.
23(1):43-50. 2010;

Walker, T. M.: A redefined type of elbow dysplasia in the dog – two cases. Canadian Veterinary Journal 39, 573-
575, 1998

Wind AP, Packard ME: Elbow incongruity and developmental elbow diseases in the dog. Part II. J Am Anim Hosp
Assoc 22:725–730, 1986

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