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Elbow dysplasia

Updated: Apr 27, 2022

What is elbow dysplasia?

 

Elbow dysplasia (ED) is a common, often debilitating, generalised incongruency of the elbow joint in young, large, pedigree, rapidly growing dogs related to abnormal bone growth, joint stresses, or cartilage development.


Elbow dysplasia is a collective term for developmental orthopaedic conditions that affect the elbow joint of young dogs of medium and large breeds.


The bone lesions that may be present in the affected elbow joint include Fragmented medial coronoid process (FMCP), Ununited anconeal process (UAP), Ununited medial epicondyle (UME), and Humeral osteochondrosis (HOC), which are also referred to as synonyms of elbow dysplasia. The disease is genetically predisposed, but the severity of the disease is influenced by other factors.


What are the clinical signs of a dog having elbow dysplasia?

 

The most usual early sign of elbow dysplasia is lameness that develops insidiously between 4 and 8 months in one or both of the front legs. In some bilateral cases, the diagnosis is well after one year. Besides the elbow pain, dogs with elbow dysplasia often develop arthritis which may cause severe lameness and stiffness in later life. In many instances, the underlying lesion goes undetected either because there are no signs or because the condition affects both front legs, and therefore, the lameness is unrecognised by the owner.


Involved elbow joints may deviate laterally, with a restricted range of motion. In advanced cases, osteoarthritis, joint effusion, and crepitus are manifested.

The clinical signs, therefore, are as follows:-

  1. Weight-bearing lameness, decreased range of motion, crepitus (joint friction).

  2. Pain on elbow extension/flexion.

  3. +/- effusion.

  4. Proximal muscle atrophy (upper limb muscle reduction).

  5. Typically noticed between 5 -18 months after birth in young animals.

  6. Common in certain large breeds of dogs, e.g.,

  7. German Shepherd Dog, Mastiff, Great Dane (Ununited anconeal process - UAP)

  8. Labrador Retriever, Golden Retriever, Rottweiler, Bernese mountain dog (Fragmented medial coronoid process - FMCP)

  9. Labrador Retriever ( Ununited medial epicondyle - UME)

  10. Labrador Retriever (Osteochondritis dissecans of the humeral condyle - OC).

The dog breeds below are predisposed to Elbow dysplasia.

How does Elbow Dysplasia develop?

 

Elbow dysplasia is a polygenic hereditary syndrome, and nutrition and exercise levels have also been implicated as predisposing factors.

Normal elbow joint
Digital X-Ray of a normal canine elbow joint

The fragmented medial coronoid process (FMCP) is the most common dysplastic elbow lesion. It occurs in 65% of cases of elbow dysplasia. In this condition, the coronoid process's medial compartment of the canine elbow fails to unite, either partially or totally, with the ulnar diaphysis and, thus, does not become a part of the articular surface of the trochlear notch. Joint laxity, irritation, and finally, osteoarthritis result. This condition and osteochondrosis of the medial humeral condyle are the most common causes of osteoarthritis of the canine elbow with bone fragments seen by radiography, arthroscopy, or CT-Scan.


The fragmented medial coronoid process (FMCP)
The fragmented medial coronoid process (FMCP)

Osteochondrosis of the humeral condyle / Incomplete ossification of the humeral condyle (IOHC) results from a disturbed endochondral fusion of the medial epicondyle's epiphysis with the humerus's distal end, resulting in chondromalacia and flap formation (Osteochondritis dissecans - OCD). This condition accounts for 3%-25% of lameness resulting from elbow dysplasia. The exact cause is unknown, but because the carpal and digital flexors originate from the ventral aspect of this structure, it may represent an epiphyseal avulsion. It results in pain on flexion of the elbow or deep digital palpation and is accompanied by soft-tissue swelling. Radiographically, radiodense structures have been seen caudal and distal to the medial epicondyle area. Lesion sometimes occurs with FMCP concurrently, and it is hypothesised that incongruity of the ulnar trochlear notch and humeral trochlear may result in osteochondral damage.

Incomplete ossification of the humeral condyle.
Incomplete ossification of the humeral condyle.

The ununited anconeal process is not a primary osteochondrosis lesion and results when there is the separation of the ossification centre of the anconeal process from the proximal ulnar metaphysis. Fusion should be completed by 5–6 months of age. The fracture results from a biomechanical imbalance of force and movement in the rapidly growing elbow. The anconeal process is connected to the ulna by a bridge of fibrous tissue, which fragments to form a pseudoarthrosis, and the elbow becomes unstable. This joint laxity continues to damage the articular cartilage, and secondary osteoarthritis results. A diagnosis is only possible in dogs over 20 weeks via a flexed mediolateral radiograph. The condition is bilateral in 20-35% of cases, and FMCP occurs concurrently in approximately 15%.

Ununited anconeal process
Ununited anconeal process

Ununited medial epicondyle, the origin of several carpal and digital flexor muscles. This epiphysis usually fuses with the medial aspect of the distal humeral condyle by six months of age. Failure of fusion accounts for approximately 3% of cases.


Ununited medial epicondyle
Ununited medial epicondyle

How is Elbow Dysplasia Diagnosed?

 

Elbow dysplasia is diagnosed by one or a number of the following:-

  1. Clinical signs are always suggestive, typically either unilateral or bilateral thoracic limb weight-bearing lameness that is episodic and with variable severity. In certain cases, e.g., in cases of FMCP, often worse after exercise and rest.

  2. Diagnostic investigation

  3. Gait evaluation.

  4. Clinical examination: palpation of the elbow for a range of motion, pain, crepitus, and effusion.

  5. Confirmation of diagnosis

  6. Radiography (X-Ray): the diagnosis is confirmed by radiography. A lateral radiograph of the elbow in the flexed position visualises the ununited process. Both elbows should be examined because the condition(s) below can be bilateral.

  7. Fragmented medial coronoid process. NB: A fragment of bone is not visible in most cases.

  8. Ununited anconeal process (diagnosis after 5 months of age).

  9. Osteochondrosis of the humeral condyle.

  10. Ununited medial epicondyle.

  11. MRI / CT can provide further information regarding suspected FMCP.

  12. Arthroscopy via medial portals confirms FMCP most accurately.


Treatment

 

Early surgical treatment is recommended before degenerative joint disease develops, and the prognosis after surgery is good. Aspirin or non-steroidal anti-inflammatory drugs (NSAIDs, e.g., carprofen, deracoxib, firocoxib, meloxicam, tepoxalin) can reduce pain and inflammation. Joint-fluid modifiers (glycosaminoglycans, hyaluronic aid) and acupuncture may also be useful. Joint injection with mesenchymal cells or platelet-rich plasma has also been described.


Fragmented Medial Coronoid Process:

  1. Conservative management - (non-steroidal anti-inflammatory medication initially for a 6-week course), short, frequent lead exercise, and maintaining optimum weight. Consider supplementation with omega-three essential fatty acids and oral chondroprotectants.

  2. Surgical treatment - arthroscopic removal of the fragment, abrasion, chondroplasty of diseased cartilage combined with an oblique proximal ulnar osteotomy. Arthroscopic surgery is popular for this disease.

Ununited Anconeal Process (UAP): for dogs that are above18 months, removal of the ununited process is performed via lateral arthrotomy. Alternatively, a midshaft ulnar osteotomy is performed to relieve asynchronous growth and results in the union of the process. For dogs aged less than 18 months, proximal oblique ulnar ostectomy plus or without lag screw fixation of the anconeal fragment is performed. Proximal oblique ulnar ostectomy with lag screw fixation appears to offer the best chance of fragment fusion and the least progression of arthritis as assessed radiographically.


Osteochondrosis of the humeral condyle: open or arthroscopic fragment removal is performed, or the subchondral bone lesion is curetted to stimulate fibrocartilage formation.


Ununited Medial Epicondyle: if the fragment is small, lameness will normally resolve by one year of age without surgery. If the fragment is large, it is reattached to the humerus via a lagged bone screw.

What is the Prognosis of Elbow Dysplasia treatment?

 
  1. Fragmented Medial Coronoid Process

  2. 85% fair to good function with ulnar osteotomy and fragment removal.

  3. 50-75% chance of improvement, such as not requiring long term non-steroidal anti-inflammatory medication with arthroscopic treatment.

  4. 94% of cases are not lame by five weeks postoperatively with subtotal coronoidectomy.

  5. Ununited Anconeal Process has a poorer outcome.

  6. Ulnar osteotomy - 50% of dogs good excellent function.

  7. Lag screw and ulnar ostectomy have a 88% good return to function. UAP excision should be considered in adult dogs with lameness that are not responsive to conservative management.

  8. Osteochondrosis of the humeral condyle 30-95% of the cases have good function with removing the flap. Success varies widely between reports.

  9. Ununited Medial Epicondyle has a good prognosis with appropriate treatment (depending on fragment size). The majority of cases have no residual lameness, and progression of secondary osteoarthritis is rare.

How is elbow dysplasia prevented?

 

Being polygenic hereditary diseases, affected dogs shouldn't be bred; the only way to eliminate these conditions. Since these diseases have a proven and strong genetic component, X-ray screening for elbow dysplasia is essential for detecting affected dogs before they can be used for breeding. The scoring may be carried out simultaneously as screening for hip dysplasia, but animals must be at least one year old.


Before purchasing a puppy, please find out if elbow dysplasia is a likely inherited condition in your chosen breed. You can visit this link for further insight into your breed of choice.

References

 

Cook C R & Cook J L (2009) Diagnostic imaging of the canine elbow dysplasia: a review. Vet Surg 38 (2), 144-153 PubMed.


Innes J (2009) Getting the elbow: diagnosis and management of elbow disease in dogs. JSAP 50 (6) 18-20 PubMed.


Burton N J, Comerford E J, Bailey M, Pead M J, Owen M R (2007) Digital analysis of ulnar trochlear notch sclerosis in Labrador retrievers. JSAP 48 (4), 220-224 PubMed.


Meyer-Lindenberg A, Fehr M, Nolte I (2001) Short and long-term results after surgical treatment of an ununited anconeal process in the dog. Veterinary Comparative Orthopaedics and Traumatology 14 (2), 101-110 VetMedResource.


Ness M G (1998) Treatment of fragmented coronoid process in young dogs by proximal ulnar osteotomy. JSAP 39 (1), 15-18 PubMed.


Denny H R, Gibbs C (1980) The surgical treatment of osteochondritis dissecans and ununited coronoid process in the canine elbow joint. JSAP 21 (6), 323-31 Wiley Online Library.

Alves-Pimenta S, Ginja MM, Colaço B. Role of elbow incongruity in canine elbow dysplasia: advances in diagnostics and biomechanics. Vet Comp Orthop Traumatol. 2019;32(2):87-96.


Barthélémy NP, Griffon DJ, Ragetly GR, Carrera I, Schaeffer DJ. Short- and long-term outcomes after arthroscopic treatment of young large breed dogs with medial compartment disease of the elbow. Vet Surg. 2014;43(8):935-943.


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