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 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
Osteochondrosis/osteochondrosis dessicans (OC/OCD):
1. Osteochondrosis (OC) – Failure of endochondral ossification resulting in a focal area of abnormally thickened articular cartilage
2. Osteochondrosis dessicans (OCD) – Separation of the thickened area of cartilage from the underlying bone
3. Newfies, Labs, Golden retrievers, Bernese, GSD, Mastiff, Rotts – other large and giant bred dogs
4. Etiology – factors possibly involved in development of CO/OCD
a. Diet and growth rate – Over feeding during juvenile growth period, high-energy and protein rich diets, excessive supplementation of calcium and phosphorus.
b. Hormonal balance
c. Trauma – intense exercise
d. Joint morphometry
e. Genetics
5. History
a. Age of onset – 4-7 months, typically diagnosed 6-10 months
b. Progressive weightbearing lameness
i. Intermittent, worse after activity or rest
ii. Bilateral – 50-90% of cases
1) Shifting lameness
c. Equal sex distribution of OC/OCD however OC/OCD can commonly occur with FCP which is more common in males
6. 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
7. Radiographs
i. Craniocaudal view most important
ii. Primarily the medial aspect of the condyle
iii. Radiolucency that interrupts the normal curvature of the trochlea
a. Also need lateral and flexed lateral views to be complete and look for additional disease processes
b. Evaluate for subchondral sclerosis surrounding the subchondral bone defect and 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 OC/OCD. Also occurs with FCP and other elbow diseases resulting in OA.
8. CT Scan
a. Helpful to evaluate for incongruity
b. Aid in evaluation of additional disease processes especially FCP
c. Aid in decision making for treatment
9. 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 – Same as above
b. Surgical – removal of cartilage flap with debridement of subchondral bone to allow bleeding and development of fibrocartilage 'scar'
i. Open arthrotomy
ii. Arthroscopy
Ununited Anconeal Process (UAP):
1. Large breed dogs have a separate ossification center for the anconeal process. Small breed dogs do not.
2. Failure of union between the anconeus and the rest of the ulna by 20 weeks of age, 24 weeks at the latest.
3. German Shepherd Dogs primarily but large and giant breeds along with Bassetts and Dachshunds
4. Cause unknown however there are several theories
a. Form of osteochondrosis
b. Disruption of microcirculation during ossification
c. Joint incongruity
i. Radioulnar incongruity
1) Radial head is higher than coronoid of ulna resulting in proximal displacement of the humerus and increased forces on the anconeal process resulting in failure of bone union. This can be a static problem or related to an episode of disparate growth that resulted in injury to the anconeal process but the growth has since equalized
ii. Malarticulation of trochlear notch
1) The radius of the trochlear notch is decreased resulting in abnormal forces on the anconeal process resulting in failure of bone union
5. History
a. Age of onset – 4-12 months
b. Progressive weightbearing lameness
i. Intermittent, worse after activity or rest
ii. Bilateral – 11-47% of cases
1) Shifting lameness
c. Equal sex distribution or more males
6. 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
7. Radiographs
a. Radiolucent line visible between the anconeus and the rest of the ulna greater than 20-24 weeks of age.
b. Flexed lateral view is most helpful to avoid superimposition with the larger medial epicondyle.
c. Standard lateral and Craniocaudal view should also be performed to evaluate for other concurrent problems.
d. Radiograph opposite elbow
8. CT Scan
a. Helpful to evaluate for incongruity
b. Aid in evaluation of additional disease processes especially FCP
c. Aid in decision making for treatment
9. Treatment - No one surgical treatment has been proven to be superior. Arthritis will most likely progress. The outcome can be anywhere from excellent to poor. Decision making depends on the size of the anconeal process, degree of OA, separation of the fragment on lateral and flexed lateral views, elbow congruity, other disease processes present, planned use of the patient (working dog vs couch potato), client, and surgeon's preferences.
a. Medical – same as above
b. Surgical excision
i. Open vs arthroscopy assisted vs arthroscopy
c. Lag screw fixation
i. Screw placed from caudal surface of the ulna into the anconeus in lag fashion
d. Proximal ulnar osteotomy (PUO)
i. Allows proximal ulna and anconeus to migrate proximally thereby reducing contact pressure and permit bone union
e. Proximal ulnar osteotomy and lag screw fixation
Elbow Incongruity
1. Transient- occurred during a phase of growth but has currently resolved
a. One of the theories of the underlying causes of FCP and UAP
2. Primary – No underlying cause identified
a. Some degree may be normal variant for certain chondrodystrophic breeds ie: Dachshund, Bassett, Lhasa, Shih Tzu
3. Secondary – Underlying premature closure of growth plates or other injury
a. Most commonly associated with premature closure of the distal ulnar physis
4. Exam
a. Generalized forelimb muscle atrophy
b. Swelling of the elbow joint due to fluid, soft tissue or bone production
c. Decreased range of motion with pain and crepitus
d. May notice carpal valgus and procurvatum of the radius if associated with premature closure of the distal ulnar physis
5. Radiographs
a. Orthogonal views of radius/ulna including the elbow and carpus to allow assessment of incongruity of elbow along with changes to carpus, valgus, varus, cranial or caudal bowing
6. CT Scan
a. Helpful to evaluate for incongruity
b. Aid in evaluation of additional disease processes
c. Aid in decision making for treatment
7. Treatment
a. Medical – see above
b. Surgical
i. Treat underlying issues – FCP, UAP
ii. Ulnar osteotomy/ostectomy
iii. Correction of angular deformity
1) Acute
2) Dynamic
Ununited Medial Epicondyle
1. Cause is unknown. Theories include failure of union of the medial epicondyle, traumatic avulsion of the tendinous origin of the humeral head of the flexor carpi ulnaris or superficial digital flexor muscles or dystrophc calcification of the tendons due to trauma or chronic inflammation
2. History
a. Age of onset – 5-8 months or older (years)
b. Acute onset with gradual improvement in young dogs
c. Slowly progressive, intermittent signs in older dog
3. Exam
a. Generalized forelimb muscle atrophy
b. Swelling of the elbow joint due to fluid, soft tissue or bone production
c. Decreased range of motion with pain and crepitus
d. Although fragments are large, may be unable to palpate
4. Radiographs
a. 3 views of elbow
5. CT Scan
a. Aid in evaluation of additional disease processes
b. Aid in decision making for treatment
6. Treatment
a. Medical – Same as above
b. Surgical - open debridement
Incomplete Ossification of the Humeral Condyle (IOHC)
1. Normally two separate centers of ossification separated by a cartilaginous plate identified at ~14 days of age. Plate replaced by bone by 70 days +/- 14 days of age
2. Male cocker spaniels along with other spaniel breeds, Labs, Rottis, GSD
3. Predisposes to lateral condylar fractures with decreased amount of trauma compared to normally fused condyle
4. Exam
a. May be anywhere from nonclinical to a fracture of the lateral humeral condyle
5. Radiographs
a. Craniocaudal view - ulna may superimpose on the area of incomplete ossification. May need several views with subtle degrees of obliquity
b. Evaluate the opposite elbow. May be bilateral.
6. CT Scan
a. Eliminates superimposition of ulna
b. Allows evaluation for additional disease processes
7. Treatment – if no current fracture
a. Medical – Same as above
i. Warn owner of potential for increased risk of fracture
b. Screw placement
i. Lag vs positional
c. Bone grafting
d. Screw placement with bone grafting
Additional reading
Textbook of Small Animal Surgery, Ed: Douglas Slatter, 3rd edition. Pub. Saunders of Elsevier Science, Philadelphia, 2003
Handbook of Small Animal Orthopedics and Fracture Repair, Ed: D Piermattei, G. Flo, C. DeCamp, 4th edition. Pub. Saunders of Elsevier Science, Philadelphia, 2006
Small Animal Surgery, Ed. T. Fossum, 3rd edition. Pub. Mosby of Elsevier Science, St. Louis, 2007
