Volume 48 | Issue 1 Article 12

1986 Osteochondritis Dissecans in the Dog David Novotny Iowa State University

Caroline L. Runyon Iowa State University

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Recommended Citation Novotny, David and Runyon, Caroline L. (1986) "Osteochondritis Dissecans in the Dog," Iowa State University Veterinarian: Vol. 48 : Iss. 1 , Article 12. Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol48/iss1/12

This Article is brought to you for free and open access by the Journals at Iowa State University Digital Repository. It has been accepted for inclusion in Iowa State University Veterinarian by an authorized editor of Iowa State University Digital Repository. For more information, please contact [email protected]. Osteochondritis Dissecans in the Dog

David Novotny, BS, DVM* Caroline L. Runyon, DVM, MS**

Introduction drocytes near the joint surface. As the carti­ Osteochondritis dissecans (OeD) is a mani­ 1age continues to grow, these chondrocytes festation of osteochondrosis characterized by a hypertrophy, vesiculate, degenerate, and be­ focal thickening of joint cartilage and subse­ come calcified. This calcified layer of the car­ quent dissection of a flap of this thickened car­ tilage is invaded by vessels from the bone tilage away from the underlying subchondral marrow. Some of the calcified cartilage is re­ bone. 1 The etiology of this condition remains sorbed, but remnants of cartilage are used as somewhat of a mystery; trauma, nutrition, is­ a framework upon which osteoblasts lay down chemia, and hereditary abnormalities of ossi­ bone. This process is called endochondral os­ fication have all been suggested.2 The disease sification. 4 is usually seen in the faster growing members In osteochondrosis, the normal chondro­ of large and giant breed dogs. The first clini­ cytes differentiation process is disturbed. 5 Ve­ cal signs of lameness are usually noted when siculation, degeneration, and calcification do the dog is between 5 and 9 months of age. not occur in a normal fashion, and the carti­ OCD is most commonly recognized in the lage gets thicker than normal. Vessels from proximal humerus, but is also found in the the bone marrow cannot penetrate this thick­ distal humerus, distal femur, and tibial tarsal ened cartilage, and bone is not formed. Re­ bone. One case of OeD of the distal radius sorption of the basal layers of cartilage and has been reported. 3 Other manifestations of replacement by bone on the diaphyseal side of osteochondrosis include ununited anconeal the joint cartilage ceases. The chondrocytes process, fragmented coronoid process, and re­ continue to proliferate near the joint surface, tained cartilage of metaphyseal growth resulting in a thickening of the joint carti­ plates. 1 Current research suggests there may lage. 4 If this process is localized to only a por­ be some relationship between osteochondrosis tion of the joint cartilage, and formation of and the development of cervical spondylolis­ bone continues in the calcified layer of the thesis, slipped femoral capital epiphysis, and surrounding cartilage, the radiographic ap­ hip dysplasia. 1 pearance will be that of an osseous defect. If the thickening of the joint cartilage is the only Pathogensis pathological change, there are no apparent OeD is a pathological condition in rapidly clinical signs. There is little inflammatory growing cartilage caused by a disturbance of reaction in the subchondral bone at this stage. endochondral ossification. Growth of the After the thickened cartilage is resorbed and epiphysis occurs in the articular cartilage in endochondral ossification then proceeds nor­ the same manner that growth of the long mally. bones occurs in the cartilage of the metaphy­ Since joint cartilage nutrition depends seal growth plates.4 Normal growth of the upon simple diffusion of nutrients from the epiphysis takes place by proliferation of chon- synovial fluid, the deeper layers of the thick­ ened cartilage are insufficiently nourished. These deeper layers of thickened articular car­ *Dr. Novotny is a 1985 graduate of the College of Vet­ tilage die, necrose, and serve as a' starting erinary Medicine at Iowa State University. point for fissures. 5 When a developing fissure **Dr. Runyon is a Professor of Veterinary Clinical Sciences at Iowa State University. reaches the joint cartilage surface, synovial

46 Iowa State University Veterinarian fluid enters the fissure and contacts the basal and development, and are "pushed" nutri­ layers of the joint cartilage and the subchon­ tionally during their most active growth pe­ dral bone. An inflammatory reaction then riod have the greatest risk of developing takes place in the defect. The dog becomes OCD. 1 painful and starts to limp. It is at this stage that the lesion becomes osteochondritis disse­ oeD of the Shoulder cans. Osteochondritis refers to the inflamma­ OCD of the shoulder joint is seen in large tion in the joint cartilage and subchondral and medium size dogs, predominantly in the bone, and dissecans refers to the flap of carti­ male. The clinical signs are first noticeable 1age that is dissected away fron1 the underly­ between 4 to 7 months of age and are usually ing subchondral bone. This flap may remain insidious in onset. Lameness on one or both in the defect, or it may detach and form an forelegs, which worsens after exercise, is the intraarticular body. The fate of the flap is of n10st prominent clinical sign. Stiffness after great importance to further development of periods of rest is also an important clinical clinical signs. 5 sign. Pain can usually be elicted by palpation, hyperflexion or hyperextension of the Etiology shoulder joint. The clinical signs may vary in A number of factors have been incrimi­ severity over periods of weeks to months. The nated as the cause of OCD, but the etiology condition is often bilateral. remains controversial and appears to be The definitive diagnosis of OCD is made multifactorial. The most common factor in­ by radiology. The view that best demonstrates criminated in experimental and clinical stud­ the lesion is the medial-lateral with slight ex­ ies is rapid growth and weight gain. In one tension ofthe limb. 13 The affected limb should study of nearly 300 patients with only a few be placed down on the film cassette and pulled dogs were not of medium or larger size. There cranial. The unaffected or upper limb should were twice as many males as females in these be pulled caudally. The image of the humeral cases. This difference may be explained by the head will thereby be superimposed over the fact that male dogs usually grow more rapidly radiolucent lumen of the trachea to enhance than female dogs.1 delineation of any lesions present. Radio­ There is probably a hereditary predisposi­ graphs will demonstrate a defect, usually in tion for OCD in the dog, although this has not the caudal aspect of the humeral head. In been proven. A higher incidence of OCD was mild or early cases only a flattening of the found in offspring of certain dogs and there dorso-caudal contour of the humeral head is were litters in which several or all of the pup­ seen. In advanced lesions there may be 12 6 9 pies were affected. . . - Genetic factors that sclerosis of the subchondral bone and calcifi­ affect growth rate and weight gain, sexual de­ cation of the cartilagenous flap. A radiograph velopment, behavior, and conformation un­ of the shoulder taken with the primary beam doubtedly playa role in the etiology.10 directed at a slightly oblique angle from the Nutrition seems to be an important factor lateral may be needed to visualize the lesion. in the development of OCD. In an experi­ This view may assist in a diagnosis because in mental study in Great Dane puppies, free many cases the lesion is slightly to the caudo­ choice feeding resulted in increased growth lateral instead of the caudal side of the hu­ rate accompanied by skeletal abnormalities meral head. 13 Both shoulders should be radio- similar to those seen with OCD.ll graphed, even if there is no history or clinical Trauma may also contribute to the develop­ sign of bilateral lameness.1 ment of OCD. Biomechanical studies have It is generally easier to diagnose OCD of shown that OCD lesions typically develop in the shoulder than it is to decide what therapy those areas of the joint cartilage that are most to use. If the flap mineralizes, it is usually subjected to the stress and trauma of weight visible on radiographs. The cartilagenous flap bearing. Trauma probably enhances the op­ may remain connected to the adjacent normal portunity for the abnormally thickened and articular cartilage and within the defect. If the slow-to-mature cartilage to cleave further flap remains cartilagenous, radiographs will once a fissure is formed. 12 reveal only the defect in the subchondral In conclusion, most evidence indicates that bone. Because animals show pain and lan1e­ dogs with a genetic capacity for rapid growth ness, restriction of exercise has been recom-

VOL. 48) No. 1 47 mended as a part of the therapy by many in­ with functional fibrocartilage and restore a vestigators. In contrast, another researchers smooth contour over the articular defect. This believes that a dog with OCD of the shoulder fibrocartilage is not as biomechanically stable should be allowed to move around as much as as the hyaline cartilage that was originally possible because this will increase the chances present, but is functionally adequate. Re­ that the flap will become dislodged. 1 If neces­ moval of the diseased tissue allows for better sary, the dog can be given analgesics. In cases healing, and greater freedom from lame­ in which clinical signs are not severe or may ness. 15 have subsided, or if there is no improvement after 4 to 6 weeks, a repeat radiographic exam oeD of the Elbow is recommended. If the defect in the humeral Three manifestations of osteochondrosis in head has not been filled, an arthrogram the elbow are ununited anconeal processes, should be made to determine whether or not a fragmented coronoid process, and OCD of flap or loose piece of cartilage remains within the medial condyle of the humerus. 1 Frag­ the defect. If the arthrogram is positive, sur­ mented coronoid process is the most common gery is indicated. Surgery is usually not neces­ and OCD of the medial condyle of the hu­ sary if there is no loose cartilage or flap in the merus is the second most common of these defect, because healing in this case can occur elbow lesions. These two lesions are seen most spontaneously. 1 frequently in Golden and Labrador Re­ Once the pedicle of the flap breaks, the flap trievers, but can be seen independently or to­ becomes dislodged and floats freely in the syn­ gether in most large breeds of dogs. 1 Although 0vial cavity. The flap is then referred to as a the clinical signs of these three elbow lesions joint mouse. The joint mouse is usually re­ are very similar in the early stages, an unun­ sorbed by the synovial fluid thru enzyme ac­ ited anconeal process is usually the only lesion tivity. Once the flap dislodges it takes one or that can be radiographically diagnosed at five two weeks before the pain subsides. It is in months of age. The owner usually complains these cases where conservative medical of a stiff foreleg gait for the first few minutes therapy is indicated. Sometimes the loose flap after a long rest. This sign is usually first dem­ will grow while bathed in the synovia and 0nstrated when the dog is four to five months may then mineralize and become visible on of age. The lesion is often bilateral, which radiographs in the posterior compartment of makes it more difficult for the owner to ob­ the joint cavity. Occasionally the joint mouse serve. The lameness progresses to a stiff stilted will migrate and lodge in the bicipital tendon gait on the forelegs, which are held externally sheath resulting ,acute pain and requiring sur­ rotated with the elbows close the chest. Physi­ gical removal. 1 Surgery is indicated when a cal examination reveals joint crepitation and mineralized joint mouse is detected to prevent pain upon palpation, flexion, or extension of secondary degenerative joint disease. the elbow. A caudolateral approach to the shoulder It is sometimes difficult to differentiate joint can be used to expose the humeral lameness caused by pain in the shoulder from head. 14 Surgery consists of removing the car­ lameness caused by pain in the elbow on tilage flap or piece of cartilage in the defect physical examination. Therefore, in doubtful and trimming the edges of the defect. The cases both elbow and shoulder should be ra­ base of the lesion should be curretted to the diographed. No radiographic abnormalities bleeding subchondral bone. In addition, some will be visible in the elbow of a dog with OCD authors advocate drilling 1 mm holes through of the medial condyle of the humerus until the the defect towards the metaphysics to stimu­ dog is about seven months of age, even late neovascularization and accelerate heal­ though the clinical signs may be present inter­ ing. 15 Any free joint mice or periarticular os­ mittently for two to three months. A young teophytes should be removed. Postsurgical dog with slight clinical signs of elbow lame­ care consists of cage rest for 7 to 10 days and ness should have a repeat radiographic ex­ restricted exercise for 4 to 6 weeks. amination in four to eight weeks following the If bony sclerosis is minimal or absent adja­ first examination to allow time for radio­ cent to the lesion and there is no secondary graphic changes to develop. A flexed lateral osteoarthrosis, the prognosis is considered and an anteroposterior radiograph are neces­ good. Following surgery, the defect will fill sary to evaluate the elbow. OCD of the me-

48 Iowa State University Veterinarian dial condyle of the humerus has a characteris­ secondary degenerative joint disease. Surpris­ tic radiographic appearance. A small ingly, many untreated dogs can function well triangular defect can be seen in the weight in spite of their handicap, but even slight bearing surface of the medial condyle on an trauma to the elbow results in transient lame­ anteroposterior projection. This defect is of­ ness. 5 ten surrounded by a sclerotic zone. In later stages, this defect may be obscured by os­ oeD of the IStifle teophytes formed at the margin of the medial OCD of the stifle usually affects large dogs humeral condyle and the medial aspect of the between three and nine months of age, and proximal ulna. In such cases, an anteroposte­ has been reported in severaJl instances to occur 2 rior medial to lateral oblique view should be in littermates. ,6,9 As high as 15 % of all cases obtained for better interpretation. 13 Cartilage­ of osteoarthrosis of the kn~e in large dogs is nous flaps and joint mice may also be ob­ secondary to OCD of the s~ifle joint. 1 Diagno­ served. Signs of secondary degenerative joint sis is often difficult becaus~ the clinical signs disease vary with the extent and severity of are vague. The hip joint rather than the knee the lesion, age of the patient upon presenta­ is apt to be suspected as the cause oflameness. tion, and possible coexistence of additional The dog presents with a disturbed gait pattern bony disease, i.e. ununited anconeal process of the hind legs similar to the "slinky gait" of and fragmented coronoid process. 2 hip dysplasia. Sometimes there is only a tem­ If left untreated, OCD of the medial con­ porary "locking:'s Physical examination may dyle of the humerus will lead to severe os­ or may not reveal joint distension and pain teoarthrosis with decreased range of motion of upon manipulation of the affected joint. How­ the elbow joint. Treatment is surgical and ever, the physical examination is valuable in should be done as soon as a diagnosis is made. ruling out other causes of stifle lameness in A medial approach to the elbow should be young dogs, such as ruptured cruciate liga­ used. Two techniques for approaching this ments or a patellar luxations. area have been described in veterinary litera­ Lateral and anteriopo$terior radiographs ture. Flexor muscle tenotomy with radial col­ are needed to confirm the diagnosis. The lateral ligament severance, or osteotomy of most common site of OCD of the stifle is the the medial epicondyle an be utilized to gain medial aspect of the weigh~ bearing surface of surgical exposure to the medial humeral con­ the lateral femoral condyle. The radiographic dyle. 14 In early cases of OCD of the medial appearance can vary from a flattening of the condyle of the humerus there is a defect in the affected femoral condyle to the presence of a weight bearing surface covered by a flap of radiolucent concave defect on the articular cartilage. The flap should be removed, the surface, often bordered by a sclerotic edges of the defect trimmed, and the base of margin. 13 Joint distension and joint bodies the defect curetted to bleeding subchondral may be observed. bone. A flap is usually not present in more In some dogs, the pathologically thickened advanced cases. It may be present as a large cartilage of the condyle does not lead to OCD, cartilagenous body adherent to the joint cap­ as ossification may be resumed and the radio­ sule, or it may have been resorbed. In a joint graphic defect may resolve. Other dogs de­ with a defect and no flap, the defect should be velop OCD, but healing can take place in the trimmed and curetted and all fragments re­ same way it does in the humeral head. In moved.2 The medial ulnar coronoid process most cases, however, only the floor of the de­ should also be carefully inspected, as OCD of fect fills with fibrocartilage and severe second­ the medial condyle of the humerus is fre­ ary osteoarthrosis develops. 5 quently associated with a fragmented cor­ Surgery has not proven very effective in the onoid process. Follo'wing surgery the dog is treatment of OCD of the stifle. Even animals cage rested for ten days and kept on restricted that have been operated on early by removal exercise for 4 to 6 weeks. of the flap do not have a good prognosis. In cases of OCD of the medical condyle of However, surgery should be attempted in ani­ the humerus, the prognosis is guarded even if mals that present with an acute case of stifle surgery is done early. However, surgery lameness and radiographically show a large should always be attempted, because an un­ flap or a joint mouse. In such cases an ex­ treated animal usually develops very severe ploratory arthrotomy should be done and the

UJI. 48) No. 1 49 flap or joint mouse should be removed. Once Conclusion osteoarthorsis develops there is little that can In recent years, the increasing number of be done to improve the condition other than reports describing osteochondrosis in dogs has conventional medical or physical therapy. 1 lead to a greater awareness of the disease. Os­ teochondrosis is a generalized disease affecting endochondral ossification of cartilage in OCD of the Hock young dogs of the large and giant breeds that OCD of the hock is the least common form have the egenetic capacity for rapid growth. of the osteochondroses. It is most frequently The possible causes of OCD include rapid seen in Golden and Labrador Retrievers. 1 Va­ growth and weight gain, overnutrition, gue clinical signs that worsen following exer­ trauma, and hereditary factors. OeD should cise begin at four to five months of age. The be suspected in any large, young dog with a dog presents with a slightly shorter step on the lameness of insidious onset that becomes affected leg, with pain upon flexion and exten­ worse after exercise and periods of rest. OCD sion of the hock. The range of flexion is re­ is more frequently seen in males and the le­ duced and the dog typically stands with its leg sions are often bilateral. The shoulder, elbow, in a hyperextended position. 7 The joint cap­ stifle, and hock joints are the primary sites of sule of the tibiotarsal joint is usually dis­ occurance. Diagnosis is based on signalment, tended, and in later stages a firm swelling can history, physical examination and radio­ be palpated on the medial side of the tarsus. graphy. Treatment must be individualized Anterioposterior and lateral radiographs and based upon age, frequency and severity are needed for the diagnosis. The lesion is lo­ of the lameness, and radiographic appearance cated on the medial trochlear ridge ofthe talus of the lesion. Surgery is usually the treatment and is best demonstrated as a defect in this of choice. Prognosis depends upon the site in­ ridge on an anterioposterior projection. The volved, the severity of the lesion, the presence height of the medial trochlear ridge of the ta­ or absence of secondary degenerative joint Ius is reduced due to displacement of an osteo­ disease, and the stage at which the lesion is chondral fragment and lysis of subchondral diagnosed and treated. Finally, it seems that bone. The width of the joint space over the genetic factors influence development of the medial trochlear ridge of the talus is in­ disease, and the owner should be made aware creased. In later stages, the subchondral bone that the condition may be hereditary. of the distal tibia opposite the medial trochlear If a dog has a family history of OCD or has ridge of the talus is eroded and the medial produced offspring with a high prevelance of malleolus undergoes some lysis. 7 Displaced or the disease, breeding should be discouraged. undisplaced osteochondral fragments can be found associated with the medial trochlear REFERENCES ridge of the talus. Cartilage flaps and joint 1. Olsson S-E: Osteochondrosis -A Growing Problem to Dog Breeders. Progress. Gaines Dog ResearchCen­ mice frequently contain bone because these ter (summer ed.): 1, 4-11, 1876. structures usually remain attached to soft tis­ 2. Alexander JW, Richardson DC, Selcer BA: Osteo­ sues such as the medial collateral ligaments or chondritis Dissecans of the Elbow, Stifle, and Hock-A Review. JAAHA 17: 51-56, 1981. the joint capsule. This maintains their blood 3. Butler HC, Wallace LJ, Ladds PW: Osteochondritis supply and allows them to continue endo­ Dissecans of the Distal End of the Radius in a Dog. JAAHA 7: 81-86, 1971. chondral ossification. 1 Sometimes a flexed lat­ 4. Olsson S-E: Osteochondrosis in the Dog, in Current eral view is necessary to demonstrate these in­ Tteterinary Therapy VII. Philadelphia, WB Saunders traarticular bodies in the medial or Co., 1980, 807-815. 5. Olsson D-E: Pathophysiology, Morphology, and caudomedial compartment of the joint cap­ Clinical Signs of Osteochondrosis (Chondrosis) in sule. 7 the Dog, in Pathophysiology in Small Animal Surgery. Surgery is the treatment of choice for OCD Philadelphia, Lea and Febiger, 1981, 604-617. 6. Woodward DC: Osteochondritis Dissecans in a Fam­ of the hock. Approach to the hock joint by ily of Bull Terriers. VMISAC 74: 936, 1979. osteotomy of the medial malleolus permits 7. Johnson KA, Howlett CR, Pettit GD: Osteochon­ drosis in the Hock Joints in Dogs. JAAHA 16: 103­ direct entry into the joint and gives good ex­ 113, 1980. posure to the medial trochlear ridge of the ta­ 8. Olson NC, Mostosky UV, Flo GL, et al: Osteochon­ lus. 14 Surgical debridement of the articular dritis Dissecans of the Tarsocrural Joint in Three Canine Siblings. JAVMA 1876: 635-637, 1980. cartilage is similar to that described pre­ 9. Knecht CD, Van Sickle DC, Blevins WE, et al: Os­ viously. teochondrosis of the Shoulder and Stifle in 3 of 5

50 Iowa State University Veterinarian Boarder Collie Littermates. JAVMA 170: 58-60, croradiographic, and Microangiographic Methods. J 1977. Sm An Prac 12: 603-610, 1971. 10. Milton JL: Osteochondritis Dissecans in the Dog, in 13. Poulos PW: Canine Osteochondrosis, in The veteri­ The veterinary Clinics of North America, Small Animal nary Clinics of North America, Small Animal Practice. Practice. Philadelphia, WB Saunders Co., 1983: 13 Philadelphia, WB Saunders Co., 1982: 12 (2): 313­ (1): 117-133. 329. 11. Hedhammer A, Wu FM, Krook L, et al: Overnutri­ 14. Piermattei DL, Greeley RG: An Atlas of Surgical Ap­ tion and Skeletal Disease. An Experimental Study in proaches to the Bones ofthe Dog and Cat. Second Edition. Growing Great Dane Dogs. Cornell vet 64 (5): 1­ Philadelphia, WB Saunders Co., 1979 68-71,102­ 160m 1974. 105, 184-185. 12. Paatsama S, Rokkanen P, JussilaJ, et al: A Study of 15. Berzon JL: Osteochondritis Dissecans in the Dog: Osteochondritis Dissecans of the Canine Humeral Diagnosis and Therapy. JAVMA 175: 796-799, Head Using Histological, OTC Bone Labelling, Mi- 1979. Hope for the Peregrine

by Danny Brass*

In the midst of the high Sierra stands and sure stoop of the peregrine falcon along Yosemite Valley, surrounded by glacial domes the cliff face, in its unending quest for food to and enormous walls of stone soaring thou­ feed its young. sands of feet upward above a tree-laden land­ Observation of the peregrine in its natural scape. Snugly nestled in its granite sanctuary, state is an experience well beyond belief and the valley and the accompanying high country from his precarious perch high above the of Tuolumne Meadows constitute Yosemite mainstream of the valley's activities, the National Park, one of the earliest of our coun­ climber is privy to an unparalleled avian dis­ try's pristine wilderness areas to be so desig­ play, not generally available to more nated and thus conserved as an enduring nat­ earthbound visitors to the park. Their flight ural heritage. along the cliff face is difficult to describe in a Although well-known for the grandeur of manner that adequately conveys the full im­ its mountainous expanse and the splendor pact of so memorable an event. It has been that its limitless hiking trails provide, its superbly depicted by J. A. Hagar (Cade, worldwide reputation is, perhaps, predomi­ 1982). nantly derived from its wealth of high granite "The patient watcher will see an exhibition walls, which beckon to rock climbers from the of flying that is literally breath-taking... farthest reaches of our globe. It is a mecca to again and again the tiercel started well to which all of the world's climbers ultimately as­ leeward and came along the cliff against the pire; a shrine, at whose temple of stone, met­ wind, diving, plunging, saw-toothing, rolling tle, skill, and character can all be tested over and over, darting hither and yon like an against the resplendant backdrop and airy ex­ autumn leaf until he would swoop up into the posure of the valley floor below. full current of air and be borne off on the gale On an otherwise calm and still morning, to do it all over again ... Nosing over sud­ when the chink of hardware and the grunts of denly, he flicked his wings rapidly 15 or 20 his own exertions are the only sounds to assail times and fell like a thunderbolt. Wings closed a climber's ears, a great wind may suddenly now, he shot down past the north end of the well up overhead, transfix him to the rock cliff, described three successive loop-the-Ioops and, in the wink of an eye, disappear. It is as across its face, turning completely upside though sonle unseen force had thrust through down at the top of each loop, and roared out the atmosphere and a small measure of sky over our heads with the wind rustling through had been abruptly sucked out of existence. A his wings like rippling canvas. Against the slight quivering of air and flesh may linger for background of the cliff his terrific speed was some moments after the reality has passed. much more apparent than it would have been The event, of course, has marked the swift in the open sky. The sheer excitement of watching such a performance was tremen­ *Danny Brass is currently a second year student in the dous; we felt a strong impulse to stand up and College of Veterinary Medicine at Iowa State University. cheer."

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