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 login to view 1 more bullet smoking location login to view 1 more bullet pattern login to view 2 more bullets 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 Laboratory evaluation CBC, ESR, CRP must rule out infectious etiology total protein and serum albumin vitamin D, TSH, PTH Vitamin D deficiency is the most commonly encountered nutritional deficiency (60-70%) 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 login to view 3 more bullets Operative infected nonunion often associated with pseudoarthrosis chance of fracture healing is low if infection isn't eradicated staged approach often important modalities login to view 4 more bullets pseudoarthrosis may be found in association with infection modalities login to view 3 more bullets hypertrophic nonunions often have biologically viable bone ends issue with fixation, not the biology modalities login to view 1 more bullet oligotrophic nonunions often have biologically viable bone ends may require biological stimulation modalities login to view 1 more bullet atrophic nonunions often have dysvascular bone ends modalities login to view 7 more bullets Techniques Bone stimulators four main delivery modes of electrical stimulation direct current login to view 1 more bullet capacitively coupled electrical fields (alternating current, AC) login to view 1 more bullet pulsed electromagnetic fields login to view 1 more bullet 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