A new configuration of cannulated screw fixation in the treatment of vertical femoral neck fractures

The treatment of vertical femoral neck fractures in young patients is a worldwide challenge. The purpose of this study is to introduce a new configuration of cannulated screw fixation in vertical femoral neck fractures by comparing with using ordinary cannulated compression screw (OCCS) alone biomechanically and clinically. Biomechanically, 20 synthetic femur models of femoral neck fractures with 20A degrees of VN angle were divided into two groups. The first group was fixed with three ordinary cannulated compression screws defined as OCCS group; the second group was fixed with two Headless Cannulated Compression Screws (HCCS) plus an OCCS, defined as combination group and tested for axial stiffness and load to failure. Clinically, a prospective study was designed with 59 patients who have vertical femoral neck fractures and were treated with cannulated screw, including 31 patients with three ordinary cannulated compression screws alone and 28 patients with an ordinary cannulated compression screw plus two headless cannulated compression screws. Biomechanically, our results showed that there was no significant difference of axial stiffness between OCCS group and combination group (109.92 +/- 10.81 vs. 123.49 +/- 15.13 N/mm, P = 0.145). But, the maximum load to failure of the combination group performed significant advantages than that of the OCCS group (446.85 +/- 76.25 vs. 302.92 +/- 80.46 N, P = 0.007). Clinically, the rates of fixation failure in the group treated with OCCS alone were 41.9%, while in the group treated with two types of screws were14.3% (P = 0.048). Our results suggested that using new configuration of an OCCS plus two HCCSs improved the outcome of vertical femoral neck fractures (FNF) patients compared to those using OCCS alone, which provides a new choice for treatment of FNF.