Professor, University of Veterinary and Pharmaceutical Sciences Brno, Department of Surgery and Orthopedics, Small Animal Clinic, Brno, Czech Republic
Osteochondrosis (OC) is a multifocal disease of epiphyseal (growth) cartilage affecting both the articular-epiphyseal cartilage complex (immature joint cartilage covering the ends of growing long bones) and the growth (physeal) plate of bones. It is a disturbance of endochondral ossification. Up to the present there are differing views on the definition and pathogenesis of osteochondrosis and this disease has several synonyms such as osteochondritis dissecans (OCD), osteochondrosis dissecans or dyschondroplasia.
The etiology of osteochondrosis is polyfactorial, while trauma, ischemia, hereditary factors, rapid growth and nutrition of the individual are taking part. Lesions of blood vessels in the cartilage causing local ischemia play probably the key role. In small animals, large and giant breeds of dogs are predisposed to osteochondrosis. Considering large and giant dogs, such breeds as Dobermann, Collie and Siberian Husky are relatively of low risk with regard to the occurrence of osteochondrosis. The OC of the humeral head was described in the cat, as well. The first clinical symptoms are seen in period of rapid growth of animals. Predilection sites for osteochondrosis are the shoulder, elbow, stifle and hock joints.
Early intervention, and as possible minimally invasive method of surgical management, represent current trends of OCD treatment. Arthroscopically assisted surgery is the treatment of choice. Recently, it is routine practice to manage OCD lesions of the shoulder, elbow, knee and hock joints arthroscopically.
The principle of managing osteochondritis dissecans is to remove cartilage flap (free fragments and/or adherent cartilage) usually with grasping forceps, and treat the surface of the lesion with abrasion chondroplasty, subchondral drilling (forage), or microfracture technique.
Arthroscopically assisted abrasion chondroplasty might be performed with a curette, hand burr, or motorized shaver. The surface is abraded until the underlying subchondral bone bleeds. The edges of the defect are debrided with the same instruments, leaving edges perpendicular to the bone surface. However, debridement during arthroscopic surgery should not be too aggressive, maintaining as much subchondral bone as possible to keep the bone plate and overlying cartilage repair tissue contoured to the normal congruency of the opposing joint surface. Smoothing of the bed is best accomplished with the motorized shaver in reverse mode.
Forage or subchondral drilling to stimulate hemorrhage and fibrocartilage response is usually done with a small Kirschner wire.
Subchondral bone microfracture technique (micropicking) has many of the advantages associated with subchondral drilling, including focal penetration of the dense subchondral bone plate to expose cartilage defects to the benefits of cellular and growth factor influx, as well as improving anchorage of the new tissue to the underlying subchondral bone and to some extent surrounding cartilage. In this technique, a microfracture pick and mallet are used to treat the OC lesion bed. It has been shown that long-term there is significantly increased filling of full-thickness articular defects, and that microfracture has superior results to autologous chondrocyte transplantation.
At the end of arthroscopic surgery, the joint is inspected and flushed thoroughly to remove all cartilage fragments.
Cartilage repair using osteochondral autografts transplantation (mosaicplasty) is promising treatment of choice in managing large defects, especially in stifle joint. Mosaic arthroplasty might be considered as a method of articular cartilage reconstruction resulting in renewed cartilage gliding surface.
Joint resurfacing, represented by chondrocyte transplantation and mesenchymal stem cell transplantation techniques, remains a challenge for future scientific research in this field.
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