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proposed to cause humero-ulnar con ict and resultant supraphysiologic loading of the medial coronoid process include static elbow incongruity (radio-ulnar length disparity), dynamic elbow incongruity (radio- ulnar longitudinal incongruence), ulnar trochlear notch geometric incongruity, primary rotational instability of the radius and ulna relative to the distal humerus and musculo-tendinous mismatch. Whether pathologic incongruity itself is the cause of forelimb pain and lameness is dif cult to determine as it is usually associated with FCP.
Radio-ulnar step incongruity occurs due to disparate growth of the paired radius and ulna during skeletal development. In the case of a short radius, increased contact pressure has been reported in the area of the tip of the medial coronoid process in cadaveric studies of radii shortened experimentally18 and FCP has been induced by premature closure of the distal radial physis and resultant radial shortening. Radio-ulnar incongruity may be a dynamic state, only occurring at certain joint positions or during elbow loading. Diagnosis of radio- ulnar incongruity during arthroscopy has been reported to have a higher diagnostic value than radiography and computed tomography (CT), as dynamic incongruity may be observed. Dynamic elbow incongruity may be present transiently during the development of elbow dysplasia but resolved by the time of diagnosis, making identi cation dif cult.
Geometric incongruity, resulting in an elliptical ulnar trochlear notch that is too constrained to accommodate the humeral condyle, is another proposed etiology. Theoretically, this anomaly would cause increased pressure to occur on both the anconeal process and
the medial coronoid process and both FCP and UAP could occur in the same joint. However, the incidence
of UAP and FCP occurring in the same elbow is low
and following three-dimensional digitizing studies and those examining the radius of curvature of the ulnar trochlear notch in breeds typically affected compared with those unaffected with FCP, it is considered unlikely that the conformation of the ulnar trochlear notch alone is responsible for clinical disease.
Commonly recognised lesions associated with
medial coronoid disease are typi ed by cartilage malacia,  brillation,  ssuring and erosion in
addition to subchondral bone micro-cracks and fragmentation. Frictional erosion of the medial humeral condyle (‘kissing lesion’) is frequently associated
with coronoid disease whilst osteochondrosis of the medial aspect of the humeral condyle may give rise to lesions of osteochondritis dissecans. This plethora of pathology and ensuing full thickness cartilage erosion with subchondral bone exposure in the region de ned by the medial coronoid process and medial aspect of the humeral condyle has been referred to as medial
An Urban Experience
compartment disease (MCD). Elbow incongruity such as radio-ulnar step defects, humero-ulnar incongruence/ con ict, varus deformity of the humerus or imbalance between skeletal and muscular mechanics may contribute to medial compartment syndrome of the elbow joint in dogs. Pathology of the lateral aspect of the elbow joint is far less commonly observed.
Non-surgical treatment of elbow osteoarthritis should always be considered as the  rst treatment option. Conservative treatment of osteoarthritis is based on 4 major components: 1) weight loss/control, 2) controlled low-impact activity; 3) NSAIDS; 4) chondroprotection. More recent additions to these treatments include physical therapy (a type of controlled low-impact activity), acupuncture, and intra-articular injection of hyaluronic acid, steroids, platelets enriched plasma or autologous conditioned plasma or stem cells. While medical treatment of osteoarthritis is well accepted and has
been evaluated in several clinical studies, very few data are available for the most recent treatment modalities. Surgical treatments may include radial or ulnar osteotomies to address perceived incongruity, removal
of free fragments and cartilage debris, debridement of lesions and subchondral micro-picking. Osteochondral Autograft Transfer System (OATSTM, Arthrex, Naples
FL) allows resurfacing of lesions associated with OCD. Osteotomy of the ulna may lead to varus deformity of
the limb and subsequent increased load on the medial compartment. Novel osteotomies have been recently described and are under investigation. The aim of these osteotomies is to achieve similar results to the sliding humeral osteotomy (shift in compartmental pressure) but with a less invasive procedure. A proximal ulnar ostotomy has been developed by Ingo Pfeil and Slobodan Tepic with the goal of causing a valgus tilt of the distal ulna
and therefore of the limb. Another options for end stage elbow osteoarthritis include uni- or bi-compartmental arthroplasty. The data available for elbow arthroplasty
is still scarce compared to total hip replacement. Total elbow replacement such as the Iowa total elbow or the TATE elbow replacement (both from Biomedtrix) offer semi-constrained implants with cemented or cementless  xation. The early results of the TATE are promising, but further long-term studies are needed. The main limitation of the elbow arthroplasty is that if revision surgery following catastrophic failure is needed, arthrodesis or amputation may be the only options. A more recent surgical option for medial compartment disease consists of a resurfacing prosthesis which aims at eliminating the medial compartment collapse and bone-to-bone contact caused by advanced medial OA. This procedure is called CUE (from Arthrex Vet System). Although few cases have been performed, the initial results are promising with good to excellent return to activity and minimal morbidity.
Osteochondrosis is not only found under the umbrella term “elbow dysplasia”, but can also affect other joints

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