Optimizing medial malleolar fixation: Two bicortical screws improve stability in osteoporotic and healthy bone models

Medial malleolar fractures are a common orthopedic injury, especially in osteoporotic bone. These fractures present unique challenges due to fragile tissues and reduced bone density, increasing the risk of fixation failure. This study aims to compare the biomechanical performance of single versus double bicortical screws in medial malleolar fractures in both healthy and osteoporotic bone.

Biomechanical study.

Using fourth-generation composite Sawbones models, 32 tibias (16 osteoporotic, 16 healthy) were divided into four groups: one or two bicortical screws in either bone type. Fractures were simulated, and fixation was achieved in a lag-by-technique fashion. Specimens were subject to axial compression until failure, measuring load-to-failure and stiffness. Statistical analysis compared performance across groups.

Constructs with two bicortical screws demonstrated significantly higher load-to-failure in both healthy (mean: 1747 N vs. 1090 N, p = 0.02) and osteoporotic bone (mean: 935 N vs. 509 N, p = 0.01). Stiffness was also greater in two-screw constructs, though not statistically significant. We used a two-tailed t-test to compare the means of the two groups, with a p-value of <0.05, which is considered statistically significant. Osteoporotic bone exhibited lower overall performance than healthy bone, but the two-screw configuration partially mitigated these disadvantages.

Our study demonstrates that two bicortical screws provide superior biomechanical stability compared to one screw, particularly in osteoporotic bone. These findings underscore the importance of optimizing fixation strategies for osteoporotic fractures. While prior studies found minimal differences between single and double-screw constructs, our use of bicortical screws highlights their advantage in load distribution and resistance to failure. Implementing these findings in clinical practice could potentially reduce the risk of fixation failure and improve outcomes for patients with osteoporotic fractures.