Incidence and risk factors for failure of conservative treatment for valgus impacted femoral neck fractures in elderly patients with high-risk comorbidities–A bi-center retrospective observational study

•Although internal fixation using multiple cannulated screws is widely accepted as the standard surgical treatment for valgus impacted femoral neck fractures, relatively higher rates of complications such as early fixation failure, non-union and femoral head osteonecrosis have been reported in elderly patients.•It is important for elderly patients with valgus impacted femoral neck fractures to avoid exposure to risks associated with multiple surgeries and anesthesia when they have high-risk comorbidities.•High union rate could be obtained if the indications for conservative treatment are well-defined in these patients.•Conservative treatment can be a viable option for valgus impacted femoral neck fractures when elderly patients with high-risk comorbidities have acceptable fracture angulation, no medial cortex displacement, and no CKD. –Establishing the ideal indications for conservative treatment for elderly patients with valgus impacted femoral neck fractures is difficult because few studies have identified predictive factors for the failure of this treatment method. This study aimed to report the outcomes of conservative treatment for elderly patients with valgus impacted femoral neck fractures and determine risk factors that lead to treatment failure. –From January 2009 to December 2018, 206 patients with valgus impacted femoral neck fracture were identified at two institutions. Elderly patients with valgus impacted femoral neck fractures corresponding to an Orthopedic Trauma Association/AO Foundation (OTA/AO) classification of 31-B1.1 or 31-B1.2 who were treated conservatively were included in the study. The following data was collected to compare the preoperative characteristics of patients with valgus impacted femoral neck fractures: age, sex, bone mineral density, medical comorbidities (hypertension, diabetes mellitus, ischemic heart disease, arrhythmia, chronic kidney disease [CKD], and stroke), medial cortex displacement, valgus angle, posterior tilt, and retroversion. These data were used to assess the independent predictors for failure of conservative treatment using multiple logistic regression analysis. –The failure rate after conservative treatment for valgus impacted femoral neck fracture in the enrolled patient group was 27.3% (15 of 55). CKD, presence of medial cortex displacement, high posterior tilt, and high retroversion were all identified as independent predictors for failure. The cut-off values for retroversion and posterior tilt tha