Purpose: Hyperglycemia in trauma patients may stem from metabolic response to stress, both in the presence and the absence of underlying diabetes. We aimed to test the association of stress hyperglycemia with risks of adverse events subjects undergoing orthopedic surgery. Patients and Methods: In a prospective observational study, we enrolled 202 consecutive patients with hyperglycemia at hospital admission for trauma injuries requiring orthopedic surgery. Based on history, diabetes was present in 183, and 13 more were defined as unknown diabetes on the basis of HbA1c ≥48mmol/mol. Stress hyperglycemia was defined in subjects with/without diabetes by a stress hyperglycemia ratio (SHR) >1.14, calculated as admission glucose/average glucose, estimated from glycosylated hemoglobin. Logistic regression analysis was used to calculate the risk of post-surgery adverse events associated with different states of hyperglycemia, after correction for demographic and clinical confounders. Results: Stress hyperglycemia was diagnosed, either as superimposed to diabetes (54/196 cases, 27.6%) as well as in the 6 cases without diabetes. At least one complication was recorded in 68 cases (33.7%), the most common being systemic infection (22.8% of cases). In the total cohort, stress hyperglycemia, irrespective of the presence of diabetes, increased the risk of adverse events (any events, odds ratio [OR], 4.43; 95% confidence interval [CI], 2.11-9.30), cardiovascular events (OR, 7.09; 95% CI, 2.47-19.91), systemic infections (OR, 4.21; 95% CI, 1.97-9.03) and other adverse events (OR, 6.30; 95% CI, 1.41-28.03), after adjustment for confounders; hospital stay was much longer. The same was true when the analysis was limited to the diabetes cohort or by comparing pure stress hyperglycemia vs diabetes without stress hyperglycemia. Conclusion: The study highlights the importance of stress hyperglycemia for adverse events in the setting of orthopedic surgery following trauma injuries. This condition requires stricter management, considering the much longer length of hospital stay and higher costs.