Femoral neck fractures are significant injuries that require fixation to allow for return to weight-bearing [1]. Determining factors of fracture management include variables such as age, physical condition, fracture displacement and fracture characteristics, with decisions often being made based off such things as the Garden or Pauwel classification system [1,2]. Elderly patients presenting with a Garden I or II fracture typically undergo internal fixation as opposed to a hip arthroplasty with a Garden III or IV fracture. Given the high mortality rates related to femoral neck fractures in the geriatric population, it is recommended for most patients to undergo surgical intervention, while subsequently monitoring for complications such as non-union, avascular necrosis, and femoral neck shortening (for those who undergo internal fixation) [[2], [3], [4], [5]]. There are multiple internal fixation options, including a sliding hip screw, multiple cannulated screws, plates and even combinations of multiple different fixation options [5,6]. It remains a point of discussion as to what the optimal fixation option or configuration is, and often this discussion is based off specific fracture characteristics.

Previous studies have attempted to assess the difference between parallel vs non-parallel cannulated screws clinically [7,8] and demonstrated no clear difference in the number of patients subsequently going on to avascular necrosis, but increased incidence of non-union in the parallel arrangement and a more favorable Harris Hip Score (HHS) in diverging screws [7]. Papanastassiou et al. focused on a fixation of 3 cannulated screws diverging in the coronal plane with one engaging the calcar femorale for greater medial cortical support and aiding in the prevention of subsidence and varus malformation [7]. Overall, diverging screws were previously advocated for due to improvements in biomechanical stability and reduction in fixation failure risk due to increases in the spread of fixation points within the femoral neck, enhancing the resistance to shear, torsional, and vertical forces [8]. This theoretically allows for limiting the risk of varus collapse and femoral head collapse [7].

Screw failure typically occurs through mechanisms such as toggling, backout, and fracture from bending, shear, or torsional forces at the fracture site [3,9]. Zdero et al. performed a study assessing two separate inverted triangle formations for cannulated screws. They assessed parallel screws, with the maximum distance between screws, abutting the anterior, posterior and inferior cortices of the femoral neck, to minimize translational movement along the fracture plane, against parallel screwed with the minimum distance between screws [9]. The maximum distance arrangement was found to demonstrate greater torsional stiffness, axial stiffness, and axial failure load and no difference in axial failure displacement [9].

Given the current uncertainty in the literature regarding the most advantageous internal fixation construct of femoral neck fractures [[7], [8], [9]], this current study sets out to determine if altering the trajectory of screws to achieve maximal spread within the femoral head portends to increased biomechanical stability when treating moderate Pauwels angle femoral neck fractures. It is hypothesized that the diverging constructs are non-superior to the parallel configuration in transcervical femoral neck fractures with a moderate Pauwel’s angle of 40 degrees.