Stegelmann S, Butler J, Matthews D, Singleton A, Ostle H
Mercy Health St Vincent Medical Center, Toledo, OH, United states of america

Background
The femoral neck system (FNS) has recently emerged as an alternative treatment option for internal fixation of femoral neck fractures, challenging the traditional methods of cannulated cancellous screws and sliding hip screws. Studies have investigated the biomechanical properties of the FNS, and potential advantages compared to other implants, but limited data exists on long-term clinical outcomes. The purpose of this study was to report survivability of the FNS implant in patients experiencing femoral neck fractures and look for risk factors associated with revision or 1-year mortality rate.

Methods
Retrospective study of adult patients who received the FNS for femoral neck fracture within a regional hospital system from January 1, 2016 to August 31, 2021. Data on demographic information, implant revisions, and patient deaths were collected from patient charts. Unpaired t tests and chi-square tests were used to analyze data.

Results
A total of 114 patients were included in this cohort, including 35 males and 79 females. Average patient follow-up was 25.7 months (ranged from 9 to 47 months). Average age at time of procedure was 74.6 years, BMI was 25.4, and hospital stay duration was 4.8 days. The 1-year mortality rate was 13.2% (15/114) and the overall revision rate was 12.3% (14/114). Time to revision ranged from 10 days to 35 months, but half of the failures (7/14) occurred within 90 days. Reasons for implant failure included cut-out, periprosthetic fracture, osteonecrosis, and non-union. Three patients suffered periprosthetic proximal femoral shaft fractures, and review of preoperative imaging suggested that these were extensions from the original fracture that may not have been appreciated prior to the index procedure. Age was significantly higher in the 1-year mortality group (P < 0.05) when compared to those who survived past 1 year. Age was not significantly different in patients receiving revisions, however (P = 0.546). Gender, BMI, and duration of hospital stay did not differ significantly when comparing rates of revision or 1-year mortality.

Conclusion
This study is the largest single-institution cohort to date that has investigated postoperative outcomes in patients receiving FNS for femoral neck fracture. Rates of revision and 1-year mortality were similar to rates in literature for FNS and other common implants. These results suggest that FNS is a safe and effective treatment option for femoral neck fractures. Age was identified as a risk factor for mortality at 1 year, however no demographic risk factors for implant revision were found. Therefore, FNS implant survivability seems to be similar within a large age range. Preoperative imaging should be meticulously reviewed to ensure there is no trochanteric extension of the fracture, as these implants are not approved to treat intertrochanteric fractures and these fracture patterns may lead to swift implant failure. Further research is now underway to classify fracture patterns in this cohort using Garden and Pauwels classification, as well as characterize quality of fixation using tip to apex distance and Parker ratios. These data will then be analyzed for potential associations with FNS survivability, which can help refine indications for this implant.