Narrative Review: Femoral Neck System (FNS) for Young Femoral-Neck Fractures — Long-Term Functional Outcomes

Abstract

Background Femoral-neck fractures in young adults are uncommon but clinically significant injuries due to the high functional demands of this population and the importance of preserving the native femoral head. Traditional fixation methods such as cannulated cancellous screws (CCS) and dynamic hip screws (DHS) are associated with complications including non-union, femoral-neck shortening, fixation failure, and avascular necrosis (AVN). The Femoral Neck System has emerged as a newer fixation construct designed to provide improved axial and rotational stability while allowing controlled fracture compression.

Aim To evaluate the long-term functional outcomes, union rates, avascular necrosis rates, and reoperation patterns associated with the use of the Femoral Neck System in young adult femoral-neck fractures through a narrative meta-analytic synthesis of current clinical evidence.

Methods A systematic literature review was performed using PubMed, Embase, Google Scholar, PubMed Central, and publisher databases for studies published from 2019 to October 2025. Search terms included “Femoral Neck System,” “femoral neck fracture,” “young adults,” “Harris Hip Score,” “revision,” and “avascular necrosis.” Clinical studies evaluating FNS outcomes were included, while purely biomechanical studies without clinical follow-up, isolated case reports, and non-extractable studies were excluded. Extracted variables included study design, patient demographics, fracture characteristics, follow-up duration, functional outcomes, union rates, AVN incidence, and reoperation rates. Due to heterogeneity among studies, a narrative synthesis was performed.

Results The evidence base consisted predominantly of retrospective and prospective cohort studies, comparative studies, and recent systematic reviews/meta-analyses. Most studies demonstrated good-to-excellent functional outcomes, with postoperative Harris Hip Scores commonly reported in the mid-70s to mid-80s. High union rates and relatively low non-union rates were observed across most series. Reported pooled revision or reoperation rates ranged from approximately 8–12%, while AVN rates varied from low single digits to nearly 10%, depending on fracture displacement and duration of follow-up. Comparative analyses suggested that FNS provides improved biomechanical stability, reduced femoral-neck shortening, and comparable or improved functional outcomes relative to CCS fixation. However, most available studies had short- to mid-term follow-up durations and observational designs.

Discussion The Femoral Neck System demonstrates promising early and mid-term clinical outcomes in young adult femoral-neck fractures, particularly in unstable vertical fracture patterns such as Pauwels type III fractures. Biomechanical studies support its theoretical advantages in rotational and axial stability, correlating with reduced loss of reduction and neck shortening observed clinically. Nevertheless, long-term evaluation remains limited, especially regarding late-onset AVN and durability of functional recovery. Variability in fracture patterns, follow-up periods, and study methodologies limits the strength of current evidence.

Conclusion Current evidence suggests that the Femoral Neck System is a promising fixation option for young adult femoral-neck fractures, offering favorable functional outcomes, high union rates, and acceptable reoperation rates with biomechanical advantages over conventional screw constructs. However, larger prospective comparative studies with long-term follow-up are necessary to establish definitive conclusions regarding femoral-head survival, AVN incidence, and long-term durability.

Keywords: Femoral Neck System, femoral-neck fracture, young adults, internal fixation, Harris Hip Score, avascular necrosis, non-union, reoperation, cannulated cancellous screws, functional outcome, hip preservation.