Introduction

Elbow dysplasia includes an array of abnormalities including fragmented medial coronoid process (FCP), osteochondritis dissecans (OCD), joint incongruity and ununited anconeal process (UAP). Treatment of elbow dysplasia includes many options depending on the clinical syndrome. Clinical outcome depends on the extent and severity of disease. The best outcome is typically obtained with early diagnosis and prompt treatment. Minimally invasive treatment modalities should be used whenever possible. Long-term medical management of osteoarthritis may also be needed as adjunctive therapy.

Ununited Anconeal Process

Ununited anconeal process (UAP) occurs most commonly in German shepherd dogs, but can be seen in many dog breeds. Surgical treatment is recommended. Arthroscopy allows assessment of the integrity of the anconeal fragment, the degree of fragment stability and the extent of osteoarthritis. The medial coronoid process should also be examined, as many patients having UAP also have FCP. If the UAP fragment is of good integrity, it is a good candidate for reattachment using a lag screw. UAP fragments that are minimally displaced and partially attached may fare well with proximal dynamic ulnar osteotomy only. This procedure allows lengthening of the ulna as the radius grows and removes the shear stress of the anconeal process, allowing it to unite with the ulnar metaphysis. If the fragment is mobile and displaced, it should be reattached and stabilized using a lag screw and k-wire, combined with a proximal dynamic ulnar osteotomy. Arthroscopic guidance can be used to place the k-wire and lag screw. Arthroscopy can also be used to assess reduction and compression of the fragment as the lag screw is tightened. If OA of the fragment and trochlear notch is severe, fragment removal is suggested.

Incongruity and Short Radius Syndrome

Elbow dysplasia may be associated with a shortened radius, leading to incongruity and osteoarthritis. The goals of treatment include improved congruity of the elbow, removal of any loose intraarticular fragments and surface treatment of osteoarthritic cartilage. Improved congruity of the elbow is accomplished by dynamic ulnar partial ostectomy. A small portion of the ulna is excised, allowing improved humeroradial contact. The ulna is not rigidly stabilized in order to allow it to shift over time to the "best fit" position. Occasionally, a small intramedullary pin is placed to give partial stability to decrease pain and prevent excessive caudal translation of the proximal ulna. This can be performed proximally, midshaft or distally. Morbidity is reduced the more distal the osteotomy is performed. It would seem that a more proximal osteotomy above the interosseous ligament would have a better chance of correction of incongruity; however, anecdotal reports suggest distal osteotomy can also be effective. Some surgeons feel that distal osteotomy is best in immature dogs because they have a more flexible interosseous ligament. Mature dogs may require a higher osteotomy due to a more rigid interosseous attachment.

Osteochondritis Dissecans

Osteochondritis dissecans (OCD) affects the medial humeral condyle. Treatment includes OCD flap removal and abrasion arthroplasty or microfracture of the subchondral bone. Recent advances have made it possible to replace the damaged area of the medial humeral condyle with an osteochondral graft obtained from the patient's stifle joint. Sliding humeral osteotomy (SHO) has also been proposed as a possible adjunctive surgery to shift loads to the lateral compartment of the elbow.

Fragmented Medial Coronoid Process

Treatment of FCP may include fragment removal, abrasion arthroplasty, microfracture, subtotal coronoidectomy, biceps tendon release or SHO.

Fragment Removal

Surgical removal of the fragment is recommended to remove one potential source of pain and factor that may lead to progressive osteoarthritis. Fragment removal can be performed using arthrotomy or arthroscopy. Arthroscopic treatment of this condition has become the treatment of choice because of its minimal invasive nature, improved view of the fragment and increased accuracy of surgical debridement. Removal of the fragment from the medial coronoid process can occasionally be accomplished by simply grasping the loose fragment with a grasping forceps while the medial joint space is opened, as valgus pressure is applied by the surgical assistant. This is typically not possible without causing iatrogenic damage to the cartilage of the medial coronoid process, radial head and medial coronoid process.

Several practical tips can facilitate removal of the fragment:

Practical Tip 1

Sometimes the fragment is visible, but is clearly not dislodged. Occasionally, the fissure line associated with the fragment is not initially visible. Use the probe to gently probe and rub the region of the medial coronoid process. This maneuver will usually reveal the margins of the fragment. A small curette, probe or banana knife is used to try to elevate the fragment to facilitate its removal.

Practical Tip 2

Fragment removal can be more effectively performed after removing a small portion of bone and cartilage from the medial coronoid process just cranial to the fragment. Chondromalacia and microfractures of the subchondral bone are typically found in this region.² A curette, hand burr or power shaver can be used to remove these damaged tissues, creating more space and improved access to remove the main fragment.

Practical Tip 3

The fragment may have to be removed in multiple pieces, either due to the fragility of the fragment or due to the sheer size of it. Fragments having necrotic bone and microfractures will often break into smaller fragments when grasped to remove them. In this case, the fragment is removed by passing the grasper multiple times until all the fragments are removed. Alternatively, a power shaver can be used to remove small multiple fragments.

Practical Tip 4

If the fragment is large and comprised of dense bone, it may be too large to grasp and remove in one piece. The fragment can be broken into smaller pieces using a small osteotome or power burr.

Practical Tip 5

Multiple fragments are often found. Inspect the region cranial to the radial head carefully using a probe. Many patients have multiple, loose fragments and they usually are found cranial to the main fragment adjacent to the radial head.

Practical Tip 6

Some fragments may have a soft tissue attachment, which prevents simple withdrawal of the fragment from the joint. Large, soft tissue attachments should be severed from the fragment using a banana knife, aggressive shaver blade or small forceps. Small, soft tissue attachments can often be broken down by simply twisting the fragment 360–720° while it is grasped.

Abrasion Arthroplasty

To perform abrasion arthroplasty, insert a hand burr or preferentially a power shaver burr through an instrument portal or arthrotomy. Either method will produce significant bone debris that can clog the egress portal and impede visualization; therefore, it is important to monitor and maintain the flow of fluid through the joint during this procedure. Spin the burr to remove subchondral bone over the area of the lesion. Check for resulting bleeding frequently by stopping inflow of fluid and ensuring adequate outflow to decrease the pressure in the joint. When bleeding is observed diffusely from the lesion bed, lavage the joint to remove the remaining bone debris and close routinely.

A hand curette can also be used for surface abrasion if the subchondral bone is not too sclerotic. Similar principles should be used as described above. The curette is also useful to contour the edge of the cartilage defect; an effort should be made to leave the edges of the articular cartilage perpendicular to the subchondral bone.

Microfracture

To perform microfracture, insert an appropriately angled micropick into the joint and press the tip against the subchondral bone surface. Have an assistant tap the pick handle once or twice. The pick should be held securely to avoid gouging the surface and adjacent healthy cartilage. Apply the micropick diffusely across the diseased area and check for resulting bleeding frequently by stopping inflow of fluid and ensuring adequate outflow. When bleeding is observed diffusely from the lesion bed, lavage the joint to remove the remaining bone debris and close routinely.

Elbow Dysplasia in Cats

Treatment of elbow dysplasia in cats is similar to dogs. Treatment may include conservative management, fragment removal, abrasion arthroplasty, microfracture, subtotal coronoidectomy or biceps tendon release. Long-term medical management of osteoarthritis may also be needed as adjunctive therapy.

Medical Treatment

Conservative treatment can be attempted initially. Multi-modal therapy increases the chance of success. Many affected cats may be overweight. An attempt should be made to restore a proper body condition by making appropriate changes to the diet and exercise regimen. Chondroprotectants, such as chondroitin sulfate and glucosamine, should be considered. Fish oils (omega-3 and 6 fatty acids) can be given as supplements or in therapeutic diets as a means of reducing inflammation within the joint. NSAID therapy with robenacoxib or meloxicam is also helpful to reduce pain and inflammation, but they should be used judiciously to prevent undesirable side effects. Some cats with severe lameness require a short course of steroids to achieve an acceptable resolution of clinical signs. After a period of weaning down of the steroids, some of these cats can be converted back to an NSAID with acceptable result.

Surgical Treatment

Surgical treatment should be considered in cats that respond poorly to conservative therapy. Surgical options include fragment removal, curettage and biceps tendon release. Excision of periarticular mineralized soft tissues is also recommended, if present, as this appears to lead to some relief of pain and improved function in affected cats. Severe osteoarthritis that does not respond to debridement of the joint with arthrotomy or arthroscopy can be treated with elbow arthrodesis.

Arthroscopy

Arthroscopic treatment is recommended to remove loose fragments, debride the areas of cartilage erosion and to perform a biceps tendon release to decrease pressure on the medial compartment of the elbow. Arthroscopy can be performed with a 1.9-mm scope using a medial portal in most cats. Arthroscopic-assisted arthrotomy can also be used to treat cats with elbow dysplasia using a minimally invasive technique.

References

(VIN editor comment: Only reference 2 is cited in the text.)

1.  Lascelles BDX. Feline degenerative joint disease. Vet Surg. 2010;39:2–13.

2.  Staiger BA, Beale BS. Use of arthroscopy for debridement of the elbow joint in cats. J Am Vet Med Assoc. 2005;226(3):401–403.

3.  Beale BS. Feline arthroscopy. In: Montavon PM, Voss K, Langley-Hobbs SJ (eds.). Feline Orthopedic Surgery and Musculoskeletal Disease. Elsevier, London 2009:283–310.