Stress and stability comparison between different systems for high tibial osteotomies

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Medical device design

Background:

• Medial opening wedge high tibial osteotomy (HTO) is a treatment for medial compartment osteoarthritis.
• HTO can lead to proximal tibia instability, with fixation devices posing risks of mechanical failure.
• Appropriate fixation device design and application are critical, particularly for overweight or weight-bearing patients.

Purpose of the Study:

• To compare the biomechanical performance of one-leg and two-leg plate systems for high tibial osteotomy.
• To evaluate construct stresses and wedge micromotions under physiological and surgical loads.
• To inform the selection of fixation devices based on patient factors and surgical goals.

Main Methods:

• A finite-element model of the tibia with a medial opening was created using CT-based images.
• The model was instrumented with both one-leg and two-leg plate systems.
• Simulations subjected the constructs to physiological and surgical loads, measuring construct stresses and wedge micromotions.

Main Results:

• Locking screws enhance construct stability, reducing implant and bone stresses.
• Two-leg designs distribute load more effectively, minimizing stresses and micromotions.
• One-leg plates can create tension at the wedge tip, potentially hindering callus formation, while two-leg systems present concerns regarding incision size and structural rigidity.

Conclusions:

• The selection of HTO plates involves balancing surgical ease, stability, and stress shielding.
• Two-leg systems are recommended for patients requiring high stability, particularly those with greater load demands or larger tibias.
• One-leg systems with locking screws are appropriate for the general patient population without significant weight or bone quality concerns.