An analysis of risk factors for failure after operative treatment of displaced femoral neck fractures in patients 18-60 years of age

OBJECTIVES: To identify risk factors for failure after operative treatment of displaced femoral neck fractures in patients 60 years of age and younger. METHODS: Design: Retrospective cohort study. SETTING: Single level 1 academic trauma center. PATIENT SELECTION CRITERIA: All patients ages 18-60 years who underwent operative fixation of a displaced femoral neck fracture (AO/OTA 31B) between 2005 and 2024 were eligible for inclusion. Patients who were lost to follow-up prior to 6 months, or who had clear indications for hemiarthroplasty but underwent fixation due to medical and or social circumstances, were excluded. OUTCOME MEASURES AND COMPARISONS: The primary outcome was treatment failure, defined as femoral neck nonunion/fixation failure, development of avascular necrosis (AVN), and/or malunion (shortening ≥ 15mm or varus angulation). Patient, injury, and treatment factors were examined as risk factors for failure. RESULTS: Two hundred and twenty-three patients were included. The average age was 39 years (SD 12, range 18-60) and 78% were male. The rates of nonunion/fixation failure, AVN, and malunion were 13%, 19%, and 5%, respectively. The overall failure rate was 30%. In multivariable analysis, increased initial fracture displacement (OR 7.1, 95% CI 1.5-33.5, p=0.013), treatment with cannulated screws versus a fixed angle implant (OR 3.7, 95% CI 1.4-10.0, p=0.009), and good (rather than excellent) reduction (OR 5.6, 95% CI 2.0-15.7, p=0.001) were independently associated with nonunion/fixation failure. In multivariable analysis, medial fracture exit <1cm from the cranial edge of the lesser trochanter was associated with a decreased risk of AVN (OR 0.13, 95% CI 0.03-0.64, p=0.011), while increasing age (OR 1.07, 95% CI 1.01-1.15, p=0.036) and low energy mechanism (OR 9.5, 95% CI 2.4-38.6, p=0.002) were associated with increased risk of malunion. In univariable analysis, treatment with a static vs dynamic implant was not associated with risk of AVN, nonunion/fixation failure, or malunion (p>0.05 for all). CONCLUSIONS: In patients aged 18-60 with displaced femoral neck fractures treated with operative fixation, the overall failure rate (including AVN, nonunion, and malunion) was 30%. Medial fracture exit < 1cm from the cranial edge of the lesser trochanter was protective against the development of AVN. Increased initial fracture displacement, treatment with non-fixed angle implants, and achieving only good (rather than excellent) reduction were independently associated with increased risk of nonunion. LEVEL OF EVIDENCE: III.