A Novel Dynamic Growth Rod Inducing Spinal Growth Modulation for the Correction of Spinal Deformities

Area of Science:

• Biomedical Engineering
• Orthopedic Surgery
• Spinal Biomechanics

Background:

• Current growth rods for early-onset scoliosis (EOS) do not optimize spinal growth.
• Frequent distraction surgeries lead to significant complications and burdens.
• There is a critical need for improved growth rods with dynamic growth and external regulation capabilities.

Purpose of the Study:

• To design and evaluate a novel growth rod (NGR) with unidirectional sliding and external regulation.
• To compare the biomechanical performance of NGR against traditional growth rods (TGR) in a simulated EOS spine model.

Main Methods:

• A 3D EOS spine model was used to simulate TGR and NGR implantation.
• Axial stiffness and bending stiffness were tested under various loading conditions.
• Range of motion, Von Mises stress distribution, axial force, moment, fatigue life, and strain energy were analyzed.

Main Results:

• NGR demonstrated higher axial compression and torsional stiffness compared to TGR and the intact group.
• NGR exhibited higher Von Mises stress values than TGR, concentrated near screw fixation, but with adequate fatigue life.
• Total strain energy for NGR was slightly lower than for TGR.

Conclusions:

• NGR shows superior stiffness and improved stress distribution compared to TGR.
• The NGR's design, featuring unidirectional sliding and a non-invasive extension mechanism, promises reduced infection rates and enhanced stability.
• NGR presents a promising advancement for early-onset scoliosis surgical interventions.