Courtesy: Dr. James Hui, Dr Ashok Shyam, Ortho TV

 

TENS for Pediatric Forearm Fractures

Basic Principle

• TENS uses two pre-bent elastic nails.
• The nails provide symmetrical bracing and three-point fixation within the medullary canal.
• The construct provides translational, axial, and rotational stability.
• Controlled micromotion promotes callus formation and secondary bone healing.

Indications

• Age >10 years, where tolerance for angulation, rotation, and displacement is minimal.
• Unstable both-bone forearm fractures.
• Failed closed reduction.
• Selected open fractures.
• Polytrauma.

Biomechanical Principle

• The nails act as internal splints.
• Opposing elastic forces stabilize the fracture.
• Three-point fixation helps prevent angulation and rotation.
• The final construct should maintain interosseous membrane tension and preserve pronation and supination.

Reduction Principles

• Achieve adequate reduction before nail insertion.
• Correct both angulation and rotation.
• Maintain the reduction during nail insertion.
• Traction and rotational maneuvers can assist reduction.

Nail Configuration

• Avoid the corkscrew phenomenon, caused by excessive nail rotation and loss of control.
• Aim for a C-shaped bend in each nail.
• Maintain balanced elastic forces.
• Nail diameter should be approximately 40% of the canal diameter for each nail.
• Combined nail fill should be approximately 80%.

Radius Fixation

• Preferred entry is through the distal radius.
• Entry can be at the radial styloid or through a dorsal approach.
• Advance the nail from distal to proximal.
• Protect the superficial radial nerve.
• Avoid injury to the APL and EPB tendons.

Ulna Fixation

• Preferred entry is through the proximal ulna.
• Distal entry is an alternative.
• The nail may be advanced proximally to distally or distally to proximally.
• For proximal entry, use the lateral/radial side.
• This helps create a balanced “see-saw” effect.

Operative Technique

Entry

• Make a small incision at the entry site.
• Protect superficial nerves and tendons.

Opening the Canal

• Use an awl to create the entry hole.
• The entry should be as perpendicular as possible to the cortex.

Nail Preparation

• Pre-bend the nail into a C-shaped curvature.
• The apex of the bend should correspond approximately to the fracture site.

Nail Insertion

• Advance the nail gently.
• Avoid cortical perforation.
• Use controlled rotational movements.
• Fluoroscopy can guide insertion.

Fracture Reduction

• Use traction and rotation to assist reduction.
• Maintain alignment while advancing the nail.

Final Position

• Both nails should cross the fracture.
• The nails should provide stable fixation.
• Maintain the appropriate C-shaped configuration.

Nail End Management

• Cut the nail, leaving a small length outside the cortex.
• Bend and bury the end to minimize soft-tissue irritation.

Technical Tips

• Gentle handling reduces the risk of cortical perforation.
• Correct nail contouring is essential.
• Avoid excessively large incisions.
• Use appropriately matched nail sizes.
• Preserve forearm rotation throughout the procedure.

Complications

• Entry-site irritation.
• Infection.
• Nerve injury, particularly superficial radial nerve injury.
• Tendon irritation.
• Nail migration.
• Malunion.
• Refracture after nail removal.

Outcome Principle

• Successful TENS depends on adequate reduction, appropriate nail size, correct nail contouring, and balanced biomechanics.
• The final construct should provide elastic stability while preserving forearm rotation.

Exam Pearls

• TENS = two pre-bent nails + three-point fixation.
• Each nail – 40% of canal diameter.
• Combined fill – 80%.
• C-shaped nail configuration = balanced elastic forces.
• Avoid the corkscrew phenomenon.
• Preserve the interosseous space and forearm rotation.
• Superficial radial nerve = important risk at the distal radial entry.