Biomechanical Analysis of Distal Radius (Greenstick) Fracture Healing

Biomechanical Analysis of Distal Radius (Greenstick) Fracture Healing by Finite Element Method

The study will be conducted to investigate the effects of electrical charges (flexoelectric effect) & mechanical brachioradialis muscle bending force on the displacement and strain of fracture gap on children with Distal radius greenstick fracture via finite element method.

Distal radius fractures are common fractures and highly prevalent especially in children, due to skeletal immaturity. They may present as greenstick fractures; due to falling on the outstretched hand during sporting events.

This type of fracture causes deformation and angulation on the cortex layer of bone, while the other side remains intact due to the higher proportion of collagen and flexibility in immature bones, making them more prone to bending rather than breaking completely.

The biomechanical environment plays a dominant role in the process of fracture healing.

It controls the communication network of biological tissues and triggers the complex proliferation process.

This mechanical load is originated from muscle contraction along the axis of bone, which improves the healing process and accelerates the earlier return to weight bearing.

Likewise, the electrical stimulation plays a superior role in acceleration of bone healing. It enhances the cells migration and proliferation process, increases mineralization, and osteogenic genes activation. The bone minerals can generate electromechanical signals through the flexoelectricity effect, which they polarize in response to bending stress force.

While finite element method is an advanced technique and a promising field to simulate the mechanical properties and predict the biomechanical behaviors on the biological structures, no previous research took advantage of both flexoelectricity and mechanical principles to simulate and predict the healing behavior on specific case.

HYPOTHESES:

H0: There will be no significant effect of brachioradialis muscle bending force and flexoelectric effect on strain of distal radius greenstick fracture.

METHODOLOGY

1. The study is analytical and will be conducted by (Finite Element Analysis) study with the following steps:

   • Modelling the radius fracture with angle ≤ 15 degrees.
   • Simulation the strain and displacement of fracture site by computerized mathematical equations with applying brachioradialis muscle force within 10-40 N and electrical charge.

2. Validation the results of computerized simulation by experimental case-control study with the following steps.

Participants :

Child A: The child will receive active elbow flexion exercise with electrotherapy. Child B: The child will be managed by conservative treatment with brace only.

Instrumentation used in treatment:

Transcutaneous Electrical Nerve Stimulation (TENS) is a form of electrotherapy commonly used in physiotherapy to relieve pain. The setting will be adjusted on 2±0.4 Hz sinusoidal wave, pulse width is typically set between 50-200 microseconds and each session lasts between 20-30 minutes.

After the electrotherapy session, active assisted elbow flexion exercise will be applied with forearm in neutral position with 3 × 15 repetition to enhance the role of horizontal components of brachioradialis muscle force.

Inclusion Criteria:

• Child with green stick fracture in the distal third of radius bone.
• Child with immobilized brace or splint.
• Angle of fracture is ≤ 15 degrees.

Exclusion criteria:

The participants will be excluded from this study if they have one of the following:

• Other type of bone fracture.
• Osteoporotic bone.
• Neurological diseases.