VSCD profiles interesting and instructive cases and use of techniques as they present.

Technique: Osteochondral Autograft Transfer (OAT)
Name: Treatment for Cartilage defects
Breed: Any Canine, particular large/giant breeds
Condition: Developmental or Acquired cartilage lesions

PATHOGENESIS:
Osteochondrosis (OC) is a developmental disease of articular cartilage most commonly affecting young, rapidly growing, large-to-giant breed dogs. Labrador Retrievers, Golden Retrievers, Newfoundlands, Mastiffs, Great Danes, and German Shepherds are breeds reported to have greater risk for the disease. The cause and pathogenesis of OC is not completely understood but appears to be multifactorial, with genetic, dietary, endocrine, traumatic, growth rate, and morphometric factors involved. Osteochondrosis represents a disturbance of endochondral ossification, with failure of deeper cartilage layers to mature and mineralize appropriately, resulting in thickening of articular cartilage.

OC lesions may remain dormant, or can (naturally) progress to osteochondritis dissecans (OCD) by cleavage or fracture of abnormal cartilage. Displacement of the osteochondral flap, resultant articular incongruity and exposed subchondral bone results in effusion, synovitis, subchondral edema, sclerosis, and degenerative joint disease (DJD) causing pain and lameness. (FIGURE 1, 2)

Age at presentation may be as early as 5–7 months; however, diagnosis may be made at a much later time point as OC may be missed, or superimposed on additional pathologies, in its early stages. For example, OC of the medial humeral condyle is commonly recognized as a component of a group of diseases known as ‘‘elbow dysplasia’’, but may be overlooked or under-treated in dogs with obvious pathology in the medial aspect of the coronoid process; further, stifle OC (FIGURE 3) may be misdiagnosed as cranial cruciate ligament insufficiency in puppies with stifle pain, effusion and normal “puppy drawer”.

TREATMENT:
Traditional therapy for OC has consisted of nonsurgical management, including exercise restriction and nonsteroidal anti-inflammatory medications, or palliative surgical treatment.

Surgical treatment of OCD has typically included removal of the diseased articular cartilage (flap), followed by debridement or osteostixis of underlying subchondral bone to stimulate fibrocartilaginous ingrowth. Most dogs improve clinically with surgical management, but most continue to have lameness, and all have inevitable and progressive DJD.

Prognosis after palliative surgery is variable, and related to anatomic location, necessary lifestyle/function post-operatively and lesion location. In the shoulder, lameness commonly resolves and the long-term outcome is favorable, particularly after arthroscopic management. However, up to 25% of cases managed by arthrotomy and debridement may have a poor outcome; and large (versus small), caudocentral (versus caudomedial) lesions have universally been associated with suboptimal clinical outcome.

Many dogs with OC of the elbow and stifle will have poor outcomes with traditional (surgical or nonsurgical) treatment. These poor outcomes are generally attributed to loss of articular cartilage and subchondral bone structure, inferior biomechanics of reparative tissue, incongruity, and/or pre-existing or subsequent secondary OA in these high-demand and complex joints. Therefore, for large caudocentral shoulder OC lesions, and any OC lesion in the stifle or elbow, we typically give clients a guarded-to-poor prognosis for high-level, pain-free function in the long term with traditional treatment.

OAT PROCEDURES:
Osteochondral autograft transfer (OAT) procedures involve transplantation of one or several cylindrical cores of normal articular cartilage and underlying subchondral bone. Donor cores are harvested from a region of limited load bearing, to an osteochondral defect in a load-bearing area. Unlike traditional surgical palliation, OAT procedures allow accurate reconstruction of subchondral and articular contour, resurfacing with hyaline or hyaline-like cartilage, and creation of an immediate barrier between synovial fluid and subchondral bone.

OAT procedures are widely used for osteochondral resurfacing in human joints and have a consistently achieved a superior outcome compared with microfracture for treatment of articular cartilage defects in the knee of human athletes. Subsequently, preclinical and clinical outcomes after OAT procedures have been reported in the canine elbow, shoulder and stifle joints - all with repeatable success. Donor sites from the canine stifle have been established and currently represent the only reliable available source of canine donor osteochondral autograft material. OAT grafts from the sulcus terminalis and medial trochlear ridge of the femur are used to reconstruct OC defects in the shoulder, elbow and stifle. (FIGURE 4) For very large OC lesions, multiple smaller OAT cores are transplanted in a mosaicplasty, to more anatomically reconstruct the articular contour. (FIGURE 4) Alternatively, custom-contoured canine osteochondral allograft is being investigated as a possible alternative to OAT autografts. (Cook, personal communication 2011)

Reconstruction of the articular surface of the medial humeral condyle using OAT procedures is technically demanding, but when anatomic reconstruction is achieved, 84% of dogs enjoy resolution of their lameness, with minimal donor site morbidity.

OC of the stifle and shoulder have also been successfully treated with OAT procedures, and are less technical than the elbow, thanks to a more uniform articular surface. In one study of stifle OAT procedures, all dogs showed significant improvement in their lameness and quality of life, 6-15 months post-operatively. In this same study, over 15% of dogs were completely free of pain and lameness after surgery. This is a considerable improvement over traditional treatments for stifle OC, when only

Similarly, in the only report of shoulder OAT procedures in dogs, lameness had subjectively resolved in 55% of limbs by 5–6 weeks postoperatively, and in 100% of limbs by 12–18 weeks. Importantly, and most compelling about this report, is that this improvement persisted for 1-4 years in all dogs, and these procedures were performed on dogs with OC lesions considered poor candidates for traditional surgeries (large or caudocentral lesions).

IMPORTANT POINTS:

• OC is a common cause of lameness in large, young dogs
• Surgical treatment should be considered for any dog with clinical pain/lameness attributed to OC
• Arthroscopic debridement of shoulder OC is consistently successful for small or caudomedial lesions on the humeral head
• Very active dogs, dogs with large/caudocentral shoulder OC, or dogs with elbow or stifle OC usually have suboptimal outcomes with traditional treatment
• OAT procedures represent an important advance in OC management, and dramatically improve the prognosis for a majority of dogs
• OAT procedures are now available by consultation at both VSC locations: Berkeley and Dublin
• contact info@vscdsurgerycenters.com if you have any questions, or would like to refer a case for evaluation and possible OAT procedures.

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