Design and biomechanical study of slide-poking external fixator for hip fracture

BACKGROUND: Femoral head collapse and coxa vara lead to internal fixator failure in elderly patients with hip fracture. External fixator application is an optimal choice; however, the existing methods have many disadvantages. METHODS: Type 31-A1.3 hip fracture models were developed in nine pairs of 1-year-old fresh bovine corpse femur specimens. Each left femur specimen was fixed by a dynamic hip screw (control group), and each right femur specimen was fixed by the slide-poking external fixator (experimental group). Vertical loading and torsion tests were then performed in both groups. RESULTS: In the vertical loading experiment, a 1000-N load was implemented. The mean vertical downward displacement of the femoral head in the experimental and control groups was 1.49322 ± 0.116280 and 2.13656 ± 0.166374 mm, respectively. In the torsion experiment, when the torsion was increased to 10.0 Nm, the mean torsion angle in the experimental and control groups was 7.9733° ± 1.65704° and 15.4889° ± 0.73228°, respectively. The slide-poking external fixator was significantly more resistant to compression and rotation than the dynamic hip screw. CONCLUSION: The slide-poking external fixator for hip fractures that was designed and developed in this study can provide sufficient stability to resist compression and rotation in hip fractures.