BackgroundWhile proximal humerus fractures remain common within the elderly population, the optimal treatment method remains controversial. Intramedullary nailing has been advocated as an effective and less invasive surgical technique. The purpose of this study is to elucidate the demographics, outcomes, and complications of intramedullary nailing for acute, displaced proximal humerus fractures.Materials and methodsMultiple computerized literature databases were used to perform a systematic review of English-language literature. Studies that met our stated criteria were further assessed for the requisite data, and when possible, similar outcome data were combined to generate frequency-weighted means.ResultsFourteen studies with 448 patients met our inclusion criteria. The frequency-weighted mean age was 64.3 years, and mean follow-up was 22.6 months. Females accounted for 71 % of the included patients. Three-part fractures (51 %) were most commonly treated. The overall frequency-weighted mean Constant score was 72.8, and American Shoulder and Elbow Surgeons (ASES) score was 84.3. Frequency-weighted mean forward elevation, abduction, extension, and external rotation were 137.3°, 138.4°, 33.8°, and 43.1°, respectively. The Constant score for two- and three-part fractures was significantly higher than for four-part fractures (p = 0.007 and p = 0.0009, respectively). The reoperation rate for two-, three-, and four-part fractures was 13.6, 17.4, and 63.2 %, respectively.ConclusionsIntramedullary nailing of acute, displaced two- and three-part proximal humerus fractures yields satisfactory clinical outcomes, although reoperation and complication rates remain high. Use of this implant for four-part fractures cannot be recommended until further clinical studies with larger patient numbers are available.Level of evidenceLevel IV, Systematic review.