Background:The prevalence of diabetes mellitus (DM) and chronic kidney disease (CKD) has markedly risen over the past three decades. Patients with DM and CKD are at increased risk of infection, immune dysfunction, as well as bone and mineral disorders. Although we know that patients with DM and CKD have these risks, we do not know how these translate to proximal humeral fracture (PHF) healing. We sought to analyze whether these established comorbidities had increased rates of complications after open reduction and internal fixation (ORIF) for PHF treatment.Methods:Using a national insurance database, 72,365 patients with PHF managed with ORIF were identified using records from 2010 to 2022. Patients were initially split into those with DM and those without and were further stratified by the presence or absence of CKD. For our comparison baseline cohort, patients were not diagnosed with either DM or CKD. Post-ORIF complication rates were assessed looking specifically at nonunion, postoperative infection, and all-cause revision surgery. A logistic regression statistical analysis was also conducted.Results:Of the 72,365 patients with PHF treated by ORIF, 41,047 were non-DM without CKD (comparison); 17,025 had DM alone (no CKD); 11,729 had DM and CKD; and 2564 had CKD alone (non-DM). Multivariate analysis indicated that patients with DM and/or CKD were at increased risk of developing nonunion (odds ratio [OR] = 1.37, 1.48, 1.23) and all-cause revision surgery (OR = 1.21, 1.11, 1.18) after ORIF for PHF compared with our comparison cohort. In addition, all patients with DM alone (non-CKD) and DM with CKD had an increased risk of postoperative infection (OR = 1.39, 1.26).Conclusion:The management of PHF is a controversial topic, particularly regarding the degree of intervention and optimal treatment choice. Regardless, using a pragmatic design and reviewing a national insurance database, this study provides information for patients in high-risk populations, specifically patients with DM and CKD, and may prove beneficial when selecting a patient-specific treatment plan. Additional studies are needed to assess varying stages of both DM and CKD in patients who sustain PHF treated by ORIF along with postoperative strategies to minimize complications.