Elbow dysplasia in dogs (Proceedings)


Elbow dysplasia in dogs (Proceedings)

The elbow joint or cubital joint is composed of three joints: humeroradial, humeroulnar and proximal radioulnar. The joint capsule includes all three joints with one space. The radial head articulates with the capitulum of the humerus whereas the ulna articulates with the trochlea. The majority of joint surface contact at the humeroulanar joint is at the medial portion of the coronoid process. The lateral process of the coronoid does not provide significant contact. The stronger lateral collateral ligament originates on the lateral epicondyle, divides and inserts on both the radius and ulna. The weaker medial collateral ligament originates from the medial epicondyle, divides and inserts on the radius and ulna. The annular ligament runs transversally around the radial head inserting on the medial and lateral extremities of the radial incisor of the ulna. There is a small olecranon ligament connecting the olecranon to the humerus.

Elbow dysplasia is a term used for a group of diseases that result in abnormal development of the cubital joint. The most common causes of elbow dysplasia are developmental and include Fragmented Medial Coronoid Process (FCP or FMCP), osteochondrosis/osteochondrosis dessicans (OC/OCD) and Ununited Anconeal Process (UAP). Additionally elbow incongruity that is either primary or secondary, such as that due to premature closure of a physis ie: distal ulnar physis, along with Ununited Medial Epicondyle (UME) and Incomplete Ossification of the Humeral Condyle (IHOC) may also fall under the larger classification of elbow dysplasia.

Fragmented Medial Coronoid Process (FCP or FMCP)

     1. Technically it is the medial portion of the coronoid process not the medial coronoid process
     2. Unknown cause but many theories
          a. Osteochondrosis
          b. Radioulnar Incongruity – Coronoid of the ulna is higher than radial head resulting in distal displacement of the Humerus and increased forces on the medial process of the coronoid resulting in failure fragmentation. This can be a static problem or related to an episode of disparate growth that resulted in injury to the medial process of the coronoid but the growth has since equalized. The reverse is a proposed mechanism of UAP.
          c. Humeroulnar incongruity – An incongruence between the trochlea of the humerus and the trochlear notch of the ulna may result in abnormal loading or forces on the medial coronoid. This is also a proposed mechanism of UAP.
          d. Secondary to contraction of biceps tendon
     3. Labs, Rottis, Goldens, Bernese, Newfies
     4. History
          a. Age of onset – 4-7 months
          b. Progressive weightbearing lameness
               i. Intermittent, worse after activity or rest
               ii. Bilateral – 50-90% of cases
                    1) Shifting lameness
          c. More common in males
     5. Exam
          a. Adduction of the elbow, external rotation of foot
          b. Generalized forelimb muscle atrophy
          c. Swelling of the elbow joint due to fluid, soft tissue or bone production
          d. Decreased range of motion with pain and crepitus
          e. May exhibit 'medial compartment pain' with flexion of the elbow and carpus at 90°, suppination and pronation of the foot and pressure on the medial aspect of the elbow in the area of the medial coronoid
          f. May exhibit pain on hyperextension of the elbow with pressure on the distal aspect of the biceps.
     6. Radiographs
          a. 3 views – Craniocaudal, lateral and flexed lateral
          b. Evaluate for subchondral sclerosis surrounding the semilunar notch, indisctinct or blunted medial coronoidand osteophytosis
               i. Osteophytosis primarily occurs
                    1) Nonarticular cranioproximal surface of anconeus
                    2) Radial head
                    3) Medial humeral epicondyle
                    4) Medial coronoid process
               ii. Osteophytosis is nonspecific to FCP. Also occurs with OC/OCD and other elbow diseases resulting in OA
          c. Uncommon to visualize the fragmented medial coronoid itself. You are looking for secondary signs
          d. Craniolateral 15° caudomedial oblique view had a 62% sensitivity for identifying FCP in one study (Wosar MA, JAVMA, 1999)
     7. CT Scan
          a. Helpful to evaluate for incongruity
          b. Aid in evaluation of additional disease processes
          c. Aid in decision making for treatment
     8. Treatment – Regardless of treatment osteoarthritis will progress. Goal of surgery is to make the patient more comfortable in the short-term and hopefully improve long-term outcome although, to date, no long term studies exist
          a. Medical – – needs to be a component of long-term care regardless of whether surgery is performed
               i. Weight management
               ii. Nonsteroidal anti-inflammatories (NSAID's)
               iii. Joint supplements
               iv. Controlled exercise
               v. Physical rehabilitation
          b. Surgical – Open arthrotomy or arthroscopy
               i. Fragment removal
               ii. Subtotal cornoidectomy
               iii. Biceps tendon release