Abstract: BACKGROUND: With the development of the aging trend of society, the incidence of femoral neck fractures is increasing. Currently, the preferred surgical treatment is cannulated screw internal fixation. However, post-surgical femoral neck shortening occurs in some cases, resulting in impaired hip functionality.
OBJECTIVE: To investigate the incidence of femoral neck shortening following the use of half-threaded cannulated screws for internal fixation in patients with femoral neck fractures, to analyze the effect on hip function, and to identify factors contributing to neck shortening.  
METHODS: A retrospective analysis was conducted on the medical records of 102 patients treated with half-threaded cannulated screws in an inverted triangle setup for femoral neck fractures at Affiliated Hai’an Hospital of Nantong University from January 2016 to January 2021. This group included 36 males and 66 females at the mean age of (57.2±7.7) years, with 34 cases of Garden type I and II fractures and 68 of Garden type III and IV fractures. The mean bone mineral density value T was -2.8 SD. The Harris score was used to evaluate the hip function. During the follow-up period, the occurrence of femoral neck shortening was determined using X-ray imagery, and the factors influencing this shortening were examined using both univariate and multivariate regression analyses.
RESULTS AND CONCLUSION: (1) Among the 102 patients with femoral neck fractures, 30 patients developed femoral neck shortening, accounting for 29.4%. 72 patients had no femoral neck shortening (70.6%). (2) The Harris score for patients experiencing neck shortening was significantly lower than that for patients without shortening (P < 0.05). (3) The study identified several factors associated with femoral neck shortening following the internal fixation of femoral neck fractures included age, gender, bone mineral density value T, preoperative Garden classification, and quality of reduction. These factors not only affect the shortening of the femoral neck after surgery, but are also directly related to the functional performance of the patient’s hip joint. (4) Femoral neck shortening after surgery for femoral neck fracture is associated with various clinical parameters, especially the patient’s age, gender, bone mineral density, preoperative classification, and accuracy of reduction during surgery.

Key words: femoral neck fracture, cannulated screw, internal fixation, femoral neck shortening, hip function, orthopedic implant