Texas Equine Veterinary Association

www.teva-online.org • Page 16 Developmental orthopedic Disease Skeletal disease associated with developmental orthopedic disease is an uncommon cause of lameness in foals less than two to four months old. However, developmental orthopedic disease is a very common skeletal disease in weanlings and yearlings and is generally considered a self-limiting disease. Developmental orthopedic disease is complex and includes osteochondrosis, physeal dysplasia, and cervical vertebral malformation. Clinical findings include synovial distention and varying degrees of lameness in the acute stage. Most young foals (less than two months old) affected with developmental orthopedic disease have multiple joints or bones involved. These foals are typically more lame than older foals, and usually have severe osteochondrosis. Radiographic findings initially may show osteochondral fragmentation, subchondral bone erosions, or may be normal. Therefore, it is important to plan on serial radiographic studies to monitor the progression of changes. Conservative management for osteochondrosis is almost always recommended in young foals and includes rest, anti- inflammatory medications, systemic chondroprotective drugs, calcium-based oral supplements, and/or intra-articular hyaluronan. If osteochondral fragmentation is evident, surgical retrieval may be beneficial; however, this should be performed at an optimal time for the individual. If there is a non-displaced fragment in a weanling or younger age foal, surgery should be delayed until the yearling period and monitored radiographically. Time will allow maturation of the underlying bone so minimal debridement and curettage will be necessary. In many instances, the extra time will allow these fragments to remineralize and surgical removal will not be necessary. traumatic nerve Injury Collision injuries of the proximal forelimb in foals may result in injury to the radial nerve or other components of the brachial plexus. Most commonly, the foal will have a "dropped" shoulder, is unable to advance the limb, and will drag the limb during ambulation. The primary rule-outs are fracture of the scapula, humerus, or olecranon; radiographic evaluation should be performed to differentiate. The condition may be transient, if attributable to neuropraxia, lasting only a few hours or the condition may be permanent. Treatment for nerve injury consists of steroidal and non-steroidal anti-inflammatory medications, DMSO, and vitamin E. Supportive care such as physical manipulation of the limb, and splinting may aid in preventing contraction of the injured limb. Acupuncture may be beneficial in some instances of nerve injury. In general, if no improvement is seen within three to five days of treatment, only 25 percent of foals will recover. InfectIous cAuses of LAmeness Determination of the location and etiology of infectious causes of lameness in foals is crucial in deciding a course of therapy and assessing prognosis. As a general rule, all foal lameness should be considered as infectious in origin until proven otherwise. In this instance, prompt appropriate treatment uniformly results in a more favorable outcome than if treatment is delayed. The clinical complex of infectious arthritis, tenosynovitis, infectious osteitis or osteomyelitis occurs in foals quite commonly. This typically occurs in foals less than four months of age, but can occasionally occur in older foals as well. Bacteria may gain entry through the umbilicus, respiratory tract or gastrointestinal tract, although direct penetration of a synovial structure from external trauma may result in synovial infection. Hematogenous dissemination of bacteria allows localization into metaphyseal, physeal, or epiphyseal cartilage. Because of the relatively sluggish blood flow and vascular stasis of nutrient vessels approaching a cartilage interface, bacteria are allowed to proliferate and colonize. Infectious arthritis and osteomyelitis of Hematogenous origin have been classified into fives types based on location of the structure involved (Figure 5). Infectious synovitis (S-type) often affects foals less than 10 days of age, can involve multiple joints and radiographic changes are rarely observed. Epiphyseal infectious arthritis (E-type) involves the joint and adjacent epiphysis. These foals are generally several weeks of age or older; multiple or single joints are involved, and radiographic evidence of epiphyseal involvement is seen. Physeal type (P-type) may occur in foals one week to four months of age. Varying degrees of soft tissue swelling and lameness are present, and only one joint is typically involved. "Sympathetic" effusion in an adjacent joint may occur. Lesions may be seen radiographically in the metaphysic, physis, or epiphysis. Pathologic fracture may result because of weakening of the involved structure. Small tarsal or cuboidal bone osteomyelitis (T-type) may result in collapse of the affected cuboidal bone(s). Multiple joints are commonly affected. Invasion into a physis or joint from a periarticular soft tissue abscess is called an I-type infection. Most commonly, joints of the upper limb are involved. Diagnosis is determined based on clinical signs, diagnostic imaging findings, increased synovial fluid white blood cell count (>30,000 cells/ul), synovial fluid hyperproteinemia (>3.5 g/dl), presence of inflammatory cells within synovial fluid, and synovial fluid culture. Foals with septic arthritis, septic physitis, and/or osteomyelitis typically have fever, lameness, joint effusion or soft tissue swelling, and palpable pain of the involved area. Radiographic changes may not initially be present; however, serial radiographic examination should be performed because radiographic changes will often lag behind clinical signs by one to three weeks. Ultrasonography is beneficial when identifying soft tissue injury or inflammatory processes of the upper limb. It is common to have abscessation of the soft tissue adjacent to infected bone or septic physitis. Magnetic resonance imaging allows early detection of bone involvement and can provide more detailed structural information prior to initiating therapy or as a means to monitor therapy. A positive synovial fluid culture can be obtained in 64 percent of the cases with the most common causative agents being Enterobacteriaceae, Streptococcus sp. and Actinobacillus. Treatment of septic arthritis consists of removing the primary source of infection, if known, and relieving the joint infection via combinations of joint lavage, regional limb perfusion, and systemic and intra-articular antimicrobials. Joint lavage is performed by using large-bore needles or arthroscopy. Joint lavage should be performed every one to three days depending upon clinical response. Reduction of synovial fluid white blood cell count by 50 percent following each joint lavage is a sign of successful treatment of joint infection. Arthroscopic debridement is beneficial if a large amount of fibrin and cellular debris are present within the joint. Alternatively, an arthrotomy along with placement of a latex drain can be performed to provide synovial drainage; sterile bandages should be changed daily for the first week. At the time of bandage change, the joint should be aseptically prepared to allow synovial fluid aspiration and antimicrobial infusion. Regional limb perfusion or intraosseous perfusion with antimicrobials is

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