Distal femur fractures (DFF) are among the most devastating injuries affecting the lower extremity and are increasingly encountered in the setting of an aging and medically complex population [[1], [2], [3]]. These fractures typically result from high-energy trauma in younger individuals or low-energy mechanisms in elderly patients with osteoporotic bone [1,3,4]. In older adults, osteoporosis frequently coexists with sarcopenia and frailty, compounding falls risk and physiologic vulnerability during time-sensitive fracture care. They are associated with significant morbidity, functional decline, prolonged hospitalization, and a high rate of perioperative complications as compared to other orthopaedic procedures [5]. As life expectancy continues to rise and osteoporosis becomes more prevalent, the clinical burden and incidence of distal femur fractures are expected to grow substantially [4,5]. Operative fixation remains the standard of care, providing structural stability, pain relief, and early mobilization, yet outcomes remain suboptimal in medically vulnerable patients despite advances in implant design and surgical technique [[2], [3], [4], [5]].

Increasing attention has been directed toward patient-specific risk factors that influence outcomes after fracture fixation. Among these, preoperative nutritional status has emerged as an underrecognized but clinically important determinant of recovery. Malnutrition is associated with impaired immune function, delayed tissue repair, and reduced physiologic reserve, and has been linked to higher rates of infection, wound complications, transfusion, prolonged length of stay, readmission, and early mortality across multiple orthopaedic populations [[6], [7], [8], [9]]. These associations have been well described in elective joint arthroplasty, spine fusion, and hip fracture surgery [8,9]. However, despite its relevance, the impact of malnutrition on outcomes following urgent fixation of distal femur fractures has not been thoroughly investigated.

In addition to patient-level factors, surgical decision-making may influence outcomes in nutritionally vulnerable populations. Locking plates and retrograde or antegrade intramedullary nails are routinely employed for fixation of DFF, with implant choice typically driven by fracture morphology, bone quality, surgeon experience, and intraoperative considerations [[5], [6], [7],10,11]. Both constructs provide reliable fixation, but it is unclear whether one technique offers superior outcomes in patients with compromised physiologic reserve, and whether malnourished patients experience differential complication rates based on implant selection.

The primary aim of this study was to evaluate the association between preoperative malnutrition and 90-day postoperative complications in adults undergoing surgical fixation of DFF. A secondary aim was to determine whether implant type (plate versus intramedullary nail) modified complication risk within the malnourished cohort. It was hypothesized that preoperative malnutrition would be independently associated with increased rates of medical and surgical complications and that implant type would not significantly affect 90-day outcomes among malnourished patients.