Background: This study evaluated treatment patterns for long bone fractures and factors that contribute to use of intramedullary nails (IMN). Methods: Patients from IBM MarketScan® Research Commercial and Medicare Databases with femoral/ tibial/humeral fractures during inpatient admission between January 2016-July 2019 were identified. Patients were categorized by treatment (i.e., non-surgical/internal fixation [extramedullary internal fixation/plating]/IMN/external fixation). Four-year rates of IMN were reported by fracture type. Logistic regression evaluated factors contributing to IMN use. Results: 14,961 femoral, 14,101 tibial, and 7,059 humeral fracture patients were identified (mean[SD] age was 45.3[18.9], 42.0[16.3], and 39.8[21.6] years and % female 50.8%, 47.7%, and 55.3%, respectively). Mean(SD) lengths of stay were 6.7(9.2), 5.9(7.0), and 5.8(10.3) days, rates of surgical treatment were 74.3%, 84.0%, and 62.7%, and rates of IMN among surgical patients were 46.6%, 27.1%, and 6.7% for femoral, tibial, and humeral fractures, respectively. IMN was the predominant treatment for femoral fractures over the past 4 years. Factors contributing to IMN use included open/closed diaphyseal fractures, pathological fractures, diagnoses of cancer or AIDS/HIV, and alcohol abuse. Conclusions: IMN was the predominant treatment for femoral fractures and use slightly increased for tibial/humeral fractures. Open/closed diaphyseal fractures, pathological fractures, cancer or AIDS/HIV, and alcohol abuse contributed to IMN use.