Objective:To investigate the effects of cortical comminution on therapeutic outcomes and postoperative complications in young patients with femoral neck fracture after fixation with femoral neck system (FNS).Methods:A retrospective study was conducted of the 86 patients with femoral neck fracture who had been treated by FNS fixation from January 2020 to December 2020 at Department of Hip Orthopaedic Trauma, Tianjin Hospital. Of them, 41 had cortical comminution at the fracture ends of the femoral neck. They were 16 males and 25 females with a mean age of 53.0 (40.5, 57.0) years. The other 45 patients had intact cortical bone at the fracture ends of the femoral neck. They were 21 males and 24 females with a mean age of 55.0 (44.5, 62.5) years. The 2 groups were compared in terms of incidence of postoperative complications, Harris hip score, Barthel index and visual analogue scale (VAS) pain score after 6-month follow-up.Results:There were no statistically significant differences between the 2 groups in baseline data or reduction mode except for fracture classification, showing comparability between groups ( P>0.05). In the cortical comminution group, the incidences of nonunion [17.1%(7/41)] and femoral neck shortening [29.3%(12/41)] were significantly higher than those in the cortical intact group [0% (0/45) and 11.1% (5/45)], the Harris hip score and Barthel index [82.0 (72.5, 91.5) points and 100.0 (90.0, 100.0)] at 6 months postoperatively were significantly lower than those in the cortical intact group [94.0 (88.0, 98.0) points and 100.0 (100.0, 100.0)], the VAS pain score [1.5 (0, 4.5) points] was significantly higher than that in the cortical intact group [0 (0, 1.0) points] (all P<0.05). However, there was no significant difference between the 2 groups in osteonecrosis of the femoral head or internal fixation failure ( P> 0.05). Conclusions:Cortical comminution following femoral neck fracture is a major risk factor for post-operative complications after FNS fixation, because it may seriously affect the recovery of hip function and quality of life in young patients.