Background/purposeImpaired healing is a feared complication with devastating outcomes for each patient. Most studies focus on geriatric fracture fixation and assess well known risk factors such as infections. However, risk factors, others than infections, and impaired healing of proximal femur fractures in non-geriatric adults are marginally assessed. Therefore, this study aimed to identify non-infection related risk factors for impaired fracture healing of proximal femur fractures in non-geriatric trauma patients.MethodsThis study included non-geriatric patients (aged 69 years and younger) who were treated between 2013 and 2020 at one academic Level 1 trauma center due to a proximal femur fracture (PFF). Patients were stratified according to AO/OTA classification. Delayed union was defined as failed callus formation on 3 out of 4 cortices after 3 to 6 months. Nonunion was defined as lack of callus-formation after 6 months, material breakage, or requirement of revision surgery. Patient follow up was 12 months.ResultsThis study included 150 patients. Delayed union was observed in 32 (21.3%) patients and nonunion with subsequent revision surgery occurred in 14 (9.3%). With an increasing fracture classification (31 A1 up to 31 A3 type fractures), there was a significantly higher rate of delayed union. Additionally, open reduction and internal fixation (ORIF) (OR 6.17, (95% CI 1.54 to 24.70,p≤ 0.01)) and diabetes mellitus type II (DM) (OR 5.74, (95% CI 1.39 to 23.72,p= 0.016)), were independent risk factors for delayed union. The rate of nonunion was independent of fracture morphology, patient’s characteristics or comorbidities.ConclusionIncreasing fracture complexity, ORIF and diabetes were found to be associated with delayed union of intertrochanteric femur fractures in non-geriatric patients. However, these factors were not associated with the development of nonunion.