Osteomyelitis-By; Dr. Dhiren B. Bhoi

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Assignment on OSTEOMYELITIS PRESENTED BY DR. DHIREN B. BHOI M. V. Sc. VETERINARY GYNAECOLOGY AND OBSTETRICS COLLEGE OF VETERINARY SCI. & ANIMAL HUSBANDRY ANAND

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Osteomyelitis Osteomyelitis is the inflammation of bone & its marrow contents Results from infection of bone during open fracture repair, orthopaedic surgery, haematogenous spread etc. Bone is normally resistant to infection unless there is soft tissue infection, bone necrosis, sequestration, implantation of foreign material, prolonged wound closure etc.

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Classification of Osteomyelitis Based on nature of organism involved Bacterial osteomyelitis Fungal Osteomyelitis Acute Haematogenous Osteomyelitis Acute Osteomyelitis Chronic Osteomyelitis Post traumatic Osteomyelitis Septic arthritis

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I. Acute Haematogenous Osteomyelitis is an endogenous form of the disease most often affecting neonates & young dogs Source of infection may be umblicus Organisms – Staphlococci, Steptococci, E.Coli, Klebsiella, Pasteurella, Proteus, etc Cl. signs – Fever, malaise, non weight bearing lameness, soft tissue swelling over the involved bone In horses, Rhodococcus equi also causes osteomyelitis (Clark et al., 2003)

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Pathophysiology Septicaemia initiated from focus of infection (umblicus) Infective emboli enters the nutrient arteries of long bones The emboli gets entrapped in the end arteries and capillaries of the metaphyseal area (epiphyseal plate) Bacterial emboli causes inflammation, microthrombi formation, ischaemia, bacterial proliferation & necrosis

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Hyperaemia, migration of leucocytes & pus formation Purulent material travels under pressure in plane of least resistance Reaches the outer cortex and elevates the periosteum This compromise cortical blood supply Leads to sequestrum formation

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Blood supply & Purulent exudation beneath periosteum

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Sequestra – are avascular segments of bone surrounded by purulent exudate isolated by fibrous tissue & new bone originating from periosteum Involucrum – is the new highly vascular bone surrounding the sequestrum When the joint capsule is attached to the metaphsysis below the epiphyseal area, it results in septic arthritis In adults, the haematogenous osteomyelitis localises in periarticular subchondral bone because of extensive anastomosis b/w epiphyseal & metaphyseal vessels The involucrum isolates the infection & also prevents the immune system & antibiotics reaching the sequestered bone paving the way for chronic osteomyelitis

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Hallmarks of late onset acute haematogenous osteomyelitis are – - Bone destruction - Osteoporosis evident in radiograph - Periosteal bone formation Diagnosis: History of previous infection & clinical findings Increased WBC count Fluid aspiration & culturing to identify the bacteria Radiograph – soft tissue swelling Technitium Scintigraphy – uptake of isotopes at the site of infection

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CT-guided tissue-core biopsy and aspiration appears to be a safe and very accurate procedure for use in the diagnosis of bone-associated diseases in small animals (Vignoli et al., 2004) Treatment Broad spectrum antimicrobial like Cephalosporins given I/V for 3-5 days Fluid therapy, good nutriton & analgesia Palpable abscesses are drained & debrided Biodegradable ciprofloxacin-CLHAS (Crosslinked high amylose starch matrix) implants are a safe and efficient modality for the prevention and treatment of osteomyelitis (Huneault et al., 2004)

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Post traumatic Osteomyelitis Exogenous source of osseous infection includes - - Direct inoculation such as bites - Open fracture - Open treatment of closed fracture - Foreign body penetration - Gunshot injuries - Surgical procedures etc.

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Acute osteomyelitis Mostly long bones are affected than axial skeleton Usually a complication of open fracture repair Cl. signs – febrile, leukocytosis, affected area is edematous, erythematous & warm, non weight bearing on affected limb, pain etc. Diagnosis – By clinical signs Needle aspiration for culture test Radiography reveals only soft tissue swelling MRI scan using gadolinium is also used

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The I/V injection of gadolinium in acute osteomyelitis Large area of hypointensity in bone marrow and also reveals a small abscess

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Treatment Early treatment prevents development of chronic osteomyelitis Broad spectrum antibiotics I/V Surgical wound – debridement, lavage & drainage Removal of infected implants External fixation device can be used to provide stabilization

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Chronic osteomyelitis Represents infection in bone for several weeks, month or years May occur after bony union or prior to union of fractures Incorporation of infected bony sequestrum in remodelling callus & cortex provides a nidus for continuing infection Wear particles from implants induce inflammation and provides a nidus for infection Associated with avascularity & scar formation ( by occlusion of small arteries – bone dead – avascularisation )

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Hall marks of chronic osteomyelitis - pain - disuse atrophy - tenderness & - drainage from the area Radiographic features – New bone production with areas of lysis (moth eaten appearance) Extensive remodelling Presence of sequestrum

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Treatment Combination of antibiotics & surgery Identifying the organism & administering proper antibiotic Surgical debridement – including medullary cavity Removal of dead bone until bleeding (Sequestrectomy) Stabilization of fracture with external fixation device or internal fixation device Cancellous bone grafting to fill bone defects Antibiotics mixed in plaster of paris, Polymers or copolymers of antibiotic-impregnated polylactic acid, polyglycolic acid or polyparadioxanone may provide an absorbable system for localized antibiotic delivery for chronic osteomyelitis (Garvin & Feschuk, 2005)

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Fungal osteomyelitis Caused by fungus like Blastomyces sp, Histoplasma capsulatum, Cryptococcus neoformans, Coccidiodes immitis, Penciillium, Aspergillosis sp. Clinical signs – lameness, soft tissue swelling, pain, open wound, draining tracks, systemic illness, lymphadenopathy etc. Organism enter into the body through inhalation, spread from GIT, direct inoculation, haematogenous spread etc. Lesions are typically pyogranulomatous in nature with mononuclear cells predominate Visceral leishmaniasis caused osteolytic osteomyelitis in a dog (de souza et al., 2005)

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Diagnosis: Based on cytological examination & identification of fungus Radiographic signs include soft tissue swelling, periosteal & endosteal proliferation and bone lysis Lesions are often below the stifle and elbow Bone biopsy is done to rule out neoplasia Treatment: Long term antifungal therapy for months until clinical signs resolute Drugs like ketoconazole, fluconazole, amphotericin B can be used and recently itraconazole is used because of fewer side effects

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Fungal osteomyelitis

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Septic arthritis is a bacterial infection secondary due to joint contamination, from neighbouring osteomyelitis, direct injuries, surgical procedures, intra-articular injections Animals receiving immunosuppressive medication may be predisposed Affected joint is swollen, painful, warm, elevated rectal temperature, limited or no weight bearing on affected limb

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Septic arthritis

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Diagnosis: Arthocentesis – to evaluate joint fluid Increased no. of PMN leucocytes Presence of bacteria Increased turbidity or purulent appearance Early radiographic signs are related to effusion & soft tissue swelling Later on, bone lysis & joint surface irregularity Computed tomography(CT) suggests proliferative, osteolytic pathology of the involved joint (Luther et al., 2005)

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Treatment: Immediate antimicrobial therapy – I/V Tetracycline – Borrelia, Rickettsiae, Mycoplasma Antibiotics continued for 2-4 weeks Joint lavage with N.S to remove cellular & enzymatic constituents. Fibrin & necrotic synovium should be removed Decompression to reduce pressure & to preserve epiphyseal vascularity in young animals Arthroscopy & surgical debridement, copious lavage for post-operative joint infection Endoscopic surgery makes a valuable contribution to the management of synovial contamination and infection (Wright et al., 2003)

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Infection associated with prosthetic implants Seen especially in total hip replacement in dogs Removal of the prosthesis & PMMA bone cement is recommended Clinical signs include illness, intermittent pain & lameness Infection usually occurs in osseous tissue adjacent to the implant particularly at bone-cement interface Metallic implants influence susceptibility to infection through several mechanisms, including corrosion, adherence of biofilm, isolation from the immune response and compromise of blood supply (Nekas et al., 2003)

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Fibronectin and plasma glycoprotein aids adherence of bacteria to the implant Certain bacteria produce a mucopolysaccharide known as biofilm on the prosthetic device which alter the environment in favour of bacteria This biofilm allows persistence of infection Diagnosis: Persistence of lameness after total joint replacement Serial radiographs show bone lysis & loosening of prosthesis Joint aspiration to isolate bacteria

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Osteomyelitis due to a prosthetic implant

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Treatment: Immediate incision, debridement, drainage for 2-3 days Broad spectrum antibiotics Removal of implant and cement material

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