Reinforced locking screws with enhanced head and neck junction: improving biomechanical stability in opening-wedge...

Locking plates and screws are essential in orthopedic surgeries, including opening-wedge high tibial osteotomy (OWHTO), owing to their ability to provide angular stability and support under mechanical stress. However, screw breakage at the head and neck junction remains a significant issue, compromising fixation and requiring revision surgery. This study aimed to determine whether increasing the diameter of the locking screws at the head and neck junctions enhances biomechanical stability.

Sixty screws, divided into two groups (n = 30 per group) -a non-reinforced group with a standard design and a reinforced group with an increased head and neck diameter- were tested. Both groups consisted of 5.0 mm locking screws, each with a length of 80 mm. Biomechanical testing, which included compression, fatigue, and torsional strength tests, was conducted to reflect clinically relevant conditions.

The reinforced screws demonstrated significantly superior biomechanical performance. In the compression test, they exhibited a higher load to failure (909.0 ± 30.4 N vs. 757.5 ± 46.2 N, p < 0.001). In the fatigue test, the reinforced screws endured more cycles before failure (70788.6 ± 6310.6 cycles vs. 23016.2 ± 5,157.9 cycles, p < 0.001) and had a greater displacement distance (3.0 ± 0.4 mm vs. 2.3 ± 0.3 mm, p = 0.001). The torsional test showed higher torque at failure for the reinforced screws (17.3 ± 0.3 Nm vs. 16.5 ± 0.4 Nm, p < 0.001), although the angular displacement differences were not statistically significant (202.0° ± 63.9° vs. 247.2° ± 64.9°, p = 0.105).

Reinforcing the head and neck junction of locking screws significantly improves their biomechanical performance. These findings suggest that structural modifications can reduce hardware failure risks in high-stress procedures such as OWHTO, enhancing implant durability and clinical outcomes.