Comparison of Pullout Strength between 3.5-mm Fully Threaded, Bicortical Screws and 4.0-mm Partially Threaded, Cancellous Screws in the Fixation of Medial Malleolar Fractures

Fully Threaded Versus Partially Threaded Screws: Determining Shear in Cancellous Bone Fixation

“…Pollard et al (22) also performed a cadaveric medial malleolar fracture study comparing 4.0-mm partially threaded cancellous screws and 3.5-mm bicortical screws. Their results suggested a median force 2 times greater and a pullout strength that demonstrated statistical significance in favor of the 3.5-mm bicortical construct (22). Similar to the study by Parker et al (27), bone density evaluations were used to prevent heterogeneous variability (22).…”

“…Their results suggested a median force 2 times greater and a pullout strength that demonstrated statistical significance in favor of the 3.5-mm bicortical construct (22). Similar to the study by Parker et al (27), bone density evaluations were used to prevent heterogeneous variability (22). Pollard et al (22) reported that this bicortical fixation pattern for fractures in patients with multiple comorbidities, such as osteoporosis, diabetes, peripheral vascular disease, smoking, and obesity, provided a stronger, more stable construct.…”

“…Tensile strength is involved with resistance of the screw from breaking and depends on the root or core diameter (minor diameter). This is in conjunction with the pullout strength, which focuses on the outside diameter (major diameter) of the threads and the number of threads that encounter bone that fail along its longitudinal axis (11,14,21,22). The shear strength contributes to these modalities and involves the cube of the root or core diameter and a force that produces a sliding failure of the construct parallel to the direction of that force (14).…”

Surgical Intervention of Medial And Lateral Malleolus Fracture : A Case Report

“…Collinge et al (6) showed that stainless steel cancellous screws had up to 24% less pullout force, significantly less torsional and bending strength than a 3.5-mm bicortical screw. There is little evidence reported in the literature on bicortical fixation of medial malleolar fractures (7,8). The AO-ASIF group recommends tension-band wiring for small avulsion type fractures of the medial malleolus that are unacceptable for screw fixation as well as for osteoporotic bone.…”

A Biomechanical Investigation of a Knotless Tension Band in Medial Malleolar Fracture Models in Composite Sawbones®

“…Numerous recent journal articles in the foot and ankle surgical literature have focused on different techniques for the operative fixation of medial malleolar fractures (1)(2)(3). Depending on the fracture fragment size and bone quality, medial malleolar fracture fixation is typically performed with either partially threaded 4-mm cancellous parallel lag screw fixation or stainless steel tension band fixation (4-9).…”