Use of Fully Threaded Cannulated Screws Decreases Femoral Neck Shortening After Fixation of Femoral Neck Fractures

Background: Femoral neck fractures (FNF) are becoming increasingly common as population ages. Nondisplaced fractures are commonly treated by cancellous, parallel placed, partially threaded cannulated screws (PTS) . This allows controlled fracture impaction. However, sliding implants can lead to femoral neck shortening (FNS) that has been shown to be correlated with reduced quality of life and impaired gait pattern. Recently, our institution has changed the fixation of FNF to fully threaded screws (FTS) in order to minimize this phenomenon. The aim of this study was to compare the FNS in patients treated with FTS as compared with historical controls treated with PTS

Patients and Methods: 38 patients were treated with FTS between 2014-16 for FNF. Out of them 22 were available for radiographic follow up. 41 patients treated previously with PTS were available as a control group. Radiographic analysis was performed to assess the FNF in three vectors: Horizontal (x), Vertical (y) and overall (z) according to the neck-shaft angle. Results: Patients demographics major complication rate were similar in the two patients’ groups.

Average FNS in the x axis was significantly smaller in the FTS group than in the PTS group (3.1±3.6mm vs 7.6±4.2mm, , p < 0.01) as well as y axis (1.2 ± 2.6mm vs 4.9 ± 4.2mm, p < 0.01) and also decreased overall z shortening (2.5 ± 3.5mm vs 6.23 ± 4.5, p < 0.01). There was a tendency towards a more valgus reduction in the PTS (137 vs 134 degrees, p = 0.08. The FTS had significantly smaller number of patients with moderate (5-10mm) or severe (>10mm) FNS. Screw pullout > 5mm occurred in 17/ 41 patients in the PTS but none in the FTS group (p < 0.01).

Conclusion: This study proves that FTS improve the radiographic results following FNF fixation using cannulated screws