NURS 611: Advanced Pathophysiology

Musculoskeletal Pathologies: Osteomyelitis Maryville University NURS 611: Advanced Pathophysiology Musculoskeletal Pathologies: Osteomyelitis Osteomyelitis is a bone infection affecting all ages, from neonates to adults (McCance & Huether, 2019). It is most common in males and ages between three and twelve years old adults (McCance & Huether, 2019). Factors that can predispose a patient to osteomyelitis development include various infections such as impetigo, cerebral abscesses, infected burns, furunculosis, and prolonged intravenous or parenteral nutrition (McCance & Huether, 2019). Typically bone is quite resistant to infection, but osteomyelitis develops from inoculation with a large number of organisms, bone damage, or the presence of hardware or foreign material into the bone (Sopirala, 2020). The pathogenesis is multifactorial and not widely understood, but the degree of severity seems to depend on the pathogen's virulence, the host's immune system, and the vascularity of the bone (Sopirala, 2020). Pathophysiology Osteomyelitis can be divided into two categories based on pathogenesis: hematogenous and nonhematogenous (Sopirala, 2020). Nonhematogenous develops adjacent to a contiguous focus of infection or from direct inoculation of infection into the bone (Sopirala, 2020). Nonhematogenous osteomyelitis develops from direct inoculation of infection into the bone, usually from trauma, surgical intervention, or hardware placement, whereas hematogenous results from microorganisms that settle into the bone causing bacteremia (Sopirala, 2020). Staphylococcus Aureus is the most common pathogen associated with osteomyelitis by promoting bacterial adherence, resistance to host defense, and proteolytic activity (Sopirala, 2020). Staphylococcus Aureus can survive intracellularly in osteoblasts and adhere to various components, including fibrinogen, fibronectin, laminin, and collagen (Sopirala, 2020). When digested by the osteoblasts, the bacteria undergo phenotypic alterations leaving them increasingly resistant to antimicrobials, which likely contributes to the high relapse rate in osteomyelitis treatment (Sopirala, 2020). Osteomyelitis induces a suppurative infection with acute inflammatory cells, vascular congestion, edema, and small vessel thrombosis (Sopirala, 2020). Early in the disease process, the vascular supply to the bone and surrounding soft tissue becomes compromised, and when the medullary and periosteal blood supply becomes compromised, large areas of dead bone known as sequestra form (Sopirala, 2020). Bacteria adhere to the necrotic and ischemic tissues, making them difficult to eradicate despite surgery, antibiotic therapy, and a robust immune response (Sopirala, 2020). New bone, known as involucrum, forms from the surviving fragments of the periosteum and cortex in the region of the infection after the active period of infection due to a vasculature reaction (Sopirala, 2020). However, the surviving bone is often osteoporotic due to the inflammatory response and atrophy (Sopirala, 2020). Clinical Manifestations There are differences seen in osteomyelitis depending on the patient's age and the site of the original infected bone (Krogstad, 2020). Initial symptoms are often nonspecific until the infection is established in the bone, and more focal symptoms such as inflammation and functional deficits can be seen (Krogstad, 2020). Osteomyelitis is rare in young infants without risk factors such as prematurity (Krogstad, 2020). In neonates and infants, symptoms include fever and pseudoparalysis, where the child fails to move the affected area (McCance & Huether, 2019). The infection easily spreads into the epiphysis and joint space in young infants and children due to the capillaries present across the epiphyseal growth plate (Sopirala, 2020). In older school-age children, the growth plate forms a temporary barrier from the epiphysis, sparing joint involvement; additionally, the periosteum is stronger and more challenging to perforate (McCance & Huether, 2019). Osteomyelitis of children most often affects the long bones, but the spine and pelvis can be involved (McCance & Huether, 2019). Clinical manifestations include local symptoms of infection such as pain, edema, erythema, decreased or impaired movement; if the spine, pelvis, or lower extremities are involved, a child may refuse to walk or develop a limb or gait disturbance (Krogstad, 2020). There is minor swelling of surrounding tissues in adolescents and adults and fewer functional restrictions (Krogstad, 2020). Due to the closure of the growth plate in older patients, infections can extend into the joint space by eroding through the periosteum (Sopirala, 2020). Accompanying lab values include elevations in white blood cell counts and erythrocyte sedimentation rates, with the most sensitive sign being an elevated C-reactive protein (CRP) level (McCance & Huether, 2019). Additional studies that may be done include blood cultures, MRI imaging, and infection culture (McCance & Huether, 2019). Treatment includes antibiotics, usually a combination of intravenous and oral for at least six weeks, dictated by culture data (McCance & Huether, 2019). Surgical intervention for irrigation and debridement may also be necessary (McCance & Huether, 2019).