advances in external skeletal fixation

Advances in External Skeletal Fixation

Canine Elbow Dysplasia In Newfoundlands

Robert J. McCarthy, DVM, MS, DACVS

• CED is the #1 cause of forelimb lameness in Newfoundlands, as well as in several other large breed dogs

• Canine elbow dysplasia (CED) refers to a collection of developmental diseases of the elbow, specifically ununited anconeal process (UAP), fragmented coronoid process (FCP), and distal humeral osteochondritis dissecans (OCD)

• FCP is by far the most common problem in Newfoundlands

Overview

Overview: Anatomy of the elbow

• The elbow is essentially a hinge, with three bones (humerus, radius and ulna) forming the joint

Overview: Anatomy of the elbow

Coronoid process

Anconeal process

32 week old Newfoundlan

d

Overview: Ununited anconeal process

UAP

Overview: Elbow OCD

8 mo old Newfoundland

Overview: Fragmented coronoid process

6 mo old Newfoundland

• Essentially all dogs with untreated CED will develop progressive osteoarthritis and lameness

Overview

• Intermittent, persistent or shifting leg lameness• Stiff, choppy, stilted forelimb gait• Pocket of fluid at outside of the elbow• Panosteitis is very rare in Newfoundlands!

Overview: Clinical signs

Overview: Clinical signs

Age of first clinical sign in dogs with CED

• UAP and OCD are easily diagnosed on routine radiographs

Overview: Diagnosis

• FCP is very difficult to see on routine radiographs

Overview: Diagnosis

• Computed tomography will diagnose this problem

Overview: Diagnosis

• Arthroscopy can be used to visualize the problem

Overview: Diagnosis

• Elbow incongruity (EI) is believed to be the underlying cause of all manifestations of CED, and may exist alone

• It has been difficult to prove a single anatomic defect to explain all manifestations of CED

Overview: Anatomic defect

Classic research by Alida Wind postulated abnormal shape of the ulna caused CED

UAP

FCP

OCD

Normal Canine elbow dysplasia


• Compared shape of the ulna in a breed with a high incidence of CED (Rottweiler) with that of low incidence breed (Greyhound)

Overview: Anatomic defectCollins KE, Cross AR, Lewis DD, et.al. A comparison of the radius of curvature of the ulnar trochlear notch of rottweilers and greyhounds using three dimensional digitization. Proc 9th Annual Amer Coll Vet Surg Symposium 1999; 4.

Rottweiler

Greyhound

Both Greyhounds and Rottweilers have an elliptical, rather than circular trochlear notch, and Greyhound is actually more narrow


• A second common theory implicates uneven growth between the radius and ulna

UAP FCP or OCD


• Compared tracings of lateral radiographic projections in dogs with unilateral UAP

Overview: Anatomic defectSjostrom L, Kasstrom H, Kallberg M. Ununited anconeal process in the dog. Pathogenesis and treatment by osteotomy of the ulna. VCOT 1995; 8:170-176.

Tracings obtained from a dog with unilateral UAP

Brown = UAPGray = Normal leg


• 15/17 elbows traced had a relatively long radius on the UAP affected side

FCP or OCD

Overview: Anatomic defectPreston CA, Schulz KS, Kass PH. Effect of radial shortening and subsequent corrective ulnar ostectomy on joint contact patterns in a canine elbow model. Proc 27th Annual Vet Ortho Soc 2000; 41.• Created a short radius in

normal cadaver dogs, and found intraarticular contact pattern was altered to stress the medial coronoid process, similar to cases with FCP

• Whatever the cause of canine elbow dysplasia, it is important to remember that simple removal of a UAP or FCP, or curettage of an OCD lesion will not resolve the underlying problem


• 33% of Newfoundlands in Norway diagnosed with CED

• 57% of Rottweilers in Australia have XR signs of CED

• 30-50% of Bernese Mountain Dogs are affected

Elbow Dysplasia: Incidence of the problem

• 57% of Rottweilers in Australia had XR signs, but only 15% developed clinical signs

• If +XR at 6mo, 50% chance of developing clinical signs

• Grade 2 CED at 12 month significantly correlated with clinical signs of disease

Elbow Dysplasia: Clinical vs. XR signs

Osteophytes None 0<2mm 12-5mm 2>5mm 3

• UAP, OCD, and FCP are inherited, independent polygenic traits (Padgett)

• Incidence in progeny more likely with increasing severity of arthritis in sires and dams

• Maternal effect has been demonstrated in Labrador retrievers and Rottweilers

Elbow Dysplasia: Genetics and breeding

• Prevalence of elbow dysplasia can be decreased with selective breeding


• Dogs with CED should NOT be bred• Dogs producing offspring with CED should NOT be bred• If possible, “NORMAL” first degree relatives of dogs with CED should NOT be bred


• Medical management should involve a “total health” plan– Moderate exercise– Control of body weight– Anti-inflammatory pain medication (NSAID’s)– Disease modifying osteoarthritis drugs

(DMOA’s)

Elbow dysplasia: Medical therapy

Anti-inflammatory pain medication

Conservative Medical Therapy

• Highly specific COX-2 inhibitor deracoxib (deramaxxR) has recently been approved for veterinary use


Deracoxib

Disease modifying osteoarthritis drugs


• Found that 84% of tested products did not meet label claim with contents raging from 0% to 115% of the label claim

• Some products had forms of chondroitin sulfate which were not absorbed

Conservative Medical TherapyAdebowale A, Cox D, Liang Z, Eddington N. Analysis of glucosamine and chondroitin sulfate content in marketed products and the Caco-2 permeability of chondroitin sulfate raw materials. JANA 3(1): 37-44, 2000


% Label Claim

Price per daily dose (1200mg) chondroitin

• Conventional therapy involves removal, but arthritis is inevitable

Surgical Therapy: Ununited Anconeal Process

• Screw fixation has been described with success, but is technically demanding, and failure may be common

Fox SM et.al. Ununited anconeal process: lag-screw fixation. JAAHA 1996


• Ulnar osteotomy (cutting the ulna) has recently been advocated

• This procedure relieves stress on the UAP, allowing it to heal spontaneously


UAP immediate postop UAP 8 weeks postop


• Debate exists regarding whether surgical therapy of any type is beneficial

Surgical Therapy: Fragmented coronoid process

• 22 dogs received either surgery or NSAID/rest• Surgery entailed removal of the FCP• 11 dogs available for follow-up• Examined radiographic scores , mean force plate values, elbow

ROM, and owner questionnaire


Huibregtse, BA, Johnson AL, Muhlbauer MC. The effect of treatment of fragmented coronoid process on the development of osteoarthritis of the elbow. J Am An Hosp Assoc 1994; 30:190-195.

• Most owners felt that there was improvement in their pet with or without surgery


Medical therapy Surgical therapy

XR score pre 1.4 2.2

XR score follow-up

2.4 2.7

Mean force plate

0.997 1.008

ROM 78 degrees 78 degrees

Altered gait 100% 50%

• 19 dogs with either FCP or OCD of the elbow received either surgery or pentosan polysulphate

• Examined force plate values for 9 months


Bouck G, Miller C, Taves C. A comparison of surgical and medical treatment of fragmented coronoid process and osteochondritis dissecans of the canine elbow. VCOT 1995; 4:177-183.

60 55 Mean 50 Vertical Force 45 (%BW) 40 35 0 2 4 6 9 Time (months)

Medical

Surgery


• Studies that investigate surgical vs. medical management of FCP are based on small numbers of cases, broad inclusion criteria, and have been usually retrospective in nature

• Studies have not evaluated medical + surgical therapy to either therapy alone

• Traditional surgery is traumatic!!


• Arthroscopic removal of FCP has been developed over the last several years

• Arthroscopic evaluation allows improved visualization and access to intraarticular structures, with minimal patient morbidity

• Tufts University School of Medicine has performed over 100 arthroscopic procedures for FCP


• 32 dogs (62 elbows) had arthroscopic procedure for CED

• Surgical removal of fragments with minimal trauma possible in all cases

• Return to preop lameness status within 1 week• Improvement in lameness status within 4 weeks

in most dogs• Improved results if before development of severe

OA


Beale BS. Arthroscopic treatment of elbow dysplasia in dogs. Proc 26th Conf Vet Ortho Soc 1999; 4.

• Surgical therapy involves removal of the flap, and curettage of the defect

• Curettage is easily performed arthroscopically which should be considered the procedure of choice

• Very limited case numbers prohibit determination of prognosis

Surgical Therapy: Elbow OCD

• Total elbow arthroplasty is likely the best future option for dogs with severe OA and crippling lameness

• Conzemius MG, Aper RL, Hill CM. Evaluation of a canine total-elbow arthroplasty system: A preliminary study in normal dogs. Vet Surg 2001; 30:11-20.– Evaluated a TEA system in 6 healthy dogs– Three dogs did extremely well (99.6% normal

weight bearing), while three failed

Future Directions

• Canine elbow dysplasia is a complex condition believed to be caused by a primary incongruity between the humerus, radius and ulna

• Incongruity can cause UAP, FCP, or OCD• Although incongruity is believed to be the

underlying cause all forms of CED, the exact nature of the incongruity is still poorly understood

Conclusions

• Diagnosis of elbow dysplasia can be difficult, especially in young dogs with FCP

• CED is a heritable, polygenic trait and prevalence can be reduced with selective breeding programs

Conclusions

• UAP is the form of CED with the most documented indication for surgery, and recent research supports ulna osteotomy as the procedure of choice in young dogs

• Debate exists regarding indication for surgery in dogs with FCP, but results with arthroscopy have been very encouraging

• Curettage by arthroscopy is indicated for OCD• It is possible that the complexity of elbow

incongruity may preclude use of any simple surgical procedure

Conclusions

Next meeting in Hawaii??

advances in external skeletal fixation

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