Introduction A nonunion is an arrest in the fracture repair process progressive evidence of non healing of a fracture of a bone a delayed union is generally defined as a failure to reach bony union by 6 months post-injury this also includes fractures that are taking longer than expected to heal (ie. distal radial fractures) large segmental defects should be considered functional non-unions Pathophysiology multifactorial most commonly, inadequate fracture stabilization and poor blood supply lead to nonunion infection eradication needs to occur along with the achieving fracture union smoking location scaphoid, distal tibia, base of the 5th metatarsal are at higher risk for nonunion because blood supply in these areas pattern segmental fractures and those with butterfly fragments increased risk of nonunion like because of compromise of the blood supply to the intercalary segment Classification Types of nonunion septic nonunion caused by infection CRP test as the most accurate predictor of infection pseudoarthrosis hypertrophic nonunion caused by inadequate stability with adequate blood supply and biology abundant callous formation without bridging bone typically heal once mechanical stability is improved atrophic nonunion caused by inadequate immobilization and inadequate blood supply oligotrophic nonunion produced by inadequate reduction with fracture fragment displacement Presentation Symptoms important to discern injury mechanisms, non operative interventions, baseline metabolic, nutritional or immunologic statuses and use of NSAIDs and/or nicotine containing products assess pain levels with axial loading of involved extremity Physical exam important to complete a thorough neurovascular exam, including the status of the soft tissue envelope assess mobility of the nonunion assess extremity for the presence of deformity Imaging Radiographs plain radiographs are the cornerstone for evaluation of fracture healing; four views should be included full length weight bearing films should obtained if a limb length discrepancy is present CT if the status of union is in question, a CT scan should be obtained; hardware artifact may limit utility of the CT scan Treatment Nonoperative fracture brace immobilization bone stimulators contraindications synovial pseudoarthroses mobile nonunions greater than 1 cm between fracture ends Operative infected nonunion often associated with pseudoarthrosis chance of fracture healing is low if infection isn't eradicated staged approach often important modalities need to remove all infected/devitalized soft tissue use antibiotic beads, VAC dressings to manage the wound with significant bone loss, bone transport may be an option muscle flaps can be critical in wound management with soft tissue loss pseudoarthrosis may be found in association with infection modalities removal of atrophic, non-viable bone ends internal fixation with mechanical stability maintenance of viable soft tissue envelope hypertrophic nonunions often have biologically viable bone ends issue with fixation, not the biology modalities internal fixation with application of appropriate mechanical stability oligotrophic nonunions often have biologically viable bone ends may require biological stimulation modalities internal fixation atrophic nonunions often have dysvascular bone ends modalities need to ensure biologically viable bony ends are apposed fixation needs to be mechanically stable bone grafting autologous iliac crest (osteoinductive) is gold standard BMPs osteoconductive agents (ie. crushed cancellous chips, DBM) establishment of healthy soft tissue flap/envelope Techniques Bone stimulators four main delivery modes of electrical stimulation direct current decrease osteoclast activity and increase osteoblast activity by reducing oxygen concentration and increasing local tissue pH capacitively coupled electrical fields (alternating current, AC) affect synthesis of cAMP, collagen and calcification of carilage pulsed electromagnetic fields cause calcification of fibrocartilage combined magnetic fields bone simulators work through induction coupling, which stimulates bone growth through the following direct effects increasing expression of BMP7 increasing expression of BMP7 increasing expression of BMP2 increasing expression of TGF-beta1 increasing expression of osteoblasts proliferation