Does fully-threaded Headless Compression Screw provide a length-stable fixation in undisplaced femoral neck fractures?

Summary: Objective: Femoral neck shortening is a common complication after surgical treatment for intracapsular femoral neck fractures. This study investigated whether fully-threaded Headless Compression Screw (FTHCS) can be a more length-stable implant than partially-threaded cannulated screw (PTCS) in reducing femoral neck shortening. Methods: A total of 50 patients with undisplaced femoral neck fractures (17 treated by internal fixation with three FTHCS, and 33 treated by three PTCS) from 2011 to 2014 were enrolled in this study. The radiography of the hips and medical records were reviewed for proximal femur geometry and complications. Results: Significant shortening of the femoral neck length until union were noted in both group (FTHCS group: −2.5 mm, p = 0.045; PTCS group: −2.4 mm, p = 0.011). There was no significant difference in the length of femoral neck shortening between groups (p = 0.855). Age was the only significant risk factor for >5 mm of femoral neck shortening (p = 0.041). The femoral neck-shaft angle tended to reduce and become more varus in both groups (FTHCS: −2.7°, SD = 4.5, p = 0.028; PTCS: −5.0°, SD = 8.3, p = 0.002), but the differences between groups were nonsignificant (p = 0.577). The complication rates were similar between FTHCS and PTCS (17.6% and 21.2%, p > 0.999). Conclusion: The FTHCSs may be a substitute for PTCSs, but it cannot prevent femoral neck shortening and varus collapse after fracture fixation. Future studies should focus on how to preserve femoral neck length and hip function after femoral neck fractures. Keywords: Cannulated screw, Femoral neck shortening, Femoral neck fractures, Headless compression screw, Threa