gms | German Medical Science

Objectives: Gotfried positive reduction presents an alternative approach for addressing challenging cases of femoral neck fracture (FNF) where achieving anatomical reduction is difficult. Nevertheless, the precise quantification of positive reduction remains uncertain. This study aimed to examine the biomechanical implications of positive reduction across various Pauwels classifications, aiming to establish a framework for quantifying positive reduction in clinical settings.

Methods: 3D models depicting negative, anatomical, and positive reductions of FNF, stabilized with dynamic hip screws (DHS) and cannulated screws (CS), were generated using CT data. These models corresponded to different Pauwels groups (Types I, II, and III). A load of 2.100 N was applied to the femoral head along the mechanical axis of the femur. The study examined the maximum von Mises stress, femur displacement, and the maximum von Mises strain. The maximum von Mises stress within the internal fixation was selected as the primary indicator to evaluate stability.

Results: The anatomic reduction model showed the minimum peak von Mises stress of the internal fixator for three groups (68.487 MPa, 98.991 MPa, and 161.11 MPa). With increasing positive reduction, there was a proportional increase in peak von Mises stress within the internal fixation. For Pauwels type I and type II, positive reductions of 1 mm (86.042 MPa, 115.3 MPa) and 2 mm (108.77 MPa, 151.7 MPa) were considered acceptable. For Pauwels type III, a positive reduction of 1 mm (167.9 MPa) was acceptable. Negative reduction should be avoided.

Conclusion: Excessive positive reduction may increase the risk of internal fixation failure in FNF.

Figure 1 [Fig. 1]