Left Parasymphysis + Right Angle Mandible Fracture: Order of Reduction

The Answer: Reduce the Left Parasymphysis FIRST

The Core Principle

"Fractures in the tooth-bearing area of the anterior mandible are generally treated first to establish the ideal occlusion. Fractures in the regions without teeth (posterior body/angle/ramus/condyle) are usually treated secondarily."

• AO Foundation Surgery Reference

Step-by-Step Surgical Sequence

Step 1: Apply Maxillomandibular Fixation (MMF)

• Erich arch bars or IMF screws are placed on both arches
• The patient is placed into MMF to restore premorbid occlusion before any reduction is done
• This is the reference point for all subsequent reduction

Step 2: Expose Both Fracture Sites

• Both sites are exposed via intraoral vestibular approaches
• The parasymphysis is accessed anteriorly; the angle may need a posterior extension of the incision or a transbuccal trocar approach

Step 3: Reduce and Fix the LEFT PARASYMPHYSIS FIRST (Anterior/Dentate Fracture)

1. Occlusion is the guiding principle. The parasymphysis lies in the dentate (tooth-bearing) segment. Reducing it first restores the correct dental arch alignment and occlusion. Any error here will compound into the angle fixation and cause malocclusion.
2. Less complex, easier to visualize. According to the JOMI article on ORIF of mandibular fractures: "The reason for starting with rigid fixation of an easier fracture is that any errors in bone reduction from the first fracture repair will result in compounding bone reduction error in subsequent fracture sites."
3. Establishes a stable reference segment. Once the parasymphysis is rigidly plated, the anterior arch is restored as a solid unit. This functionally converts the problem from a bilateral injury into a simpler unilateral angle injury.
4. Muscular forces favor this approach. The suprahyoid muscles pull the parasymphysis/symphysis segment inferiorly and posteriorly. Reducing and fixing this first removes their deforming pull.

• Two miniplates (tension band plate along the superior border + inferior border plate) OR
• One inferior border plate with bicortical screws + a tension band monocortical plate superiorly
• Rigid fixation is mandatory here due to the torsional forces at this site

Step 4: Reduce and Fix the RIGHT ANGLE FRACTURE Second (Posterior Fracture)

1. Once the parasymphysis is rigidly fixed, the bilateral injury is now functionally a unilateral angle fracture, which is far simpler to manage.
2. The angle can be treated with nonrigid fixation (Champy technique) - a single miniplate along the external oblique ridge (superior border). The PMC bilateral mandibular fractures study states: "Rigid fixation of the body/parasymphysis fracture functionally converts a bilateral injury into a unilateral injury at the angle, which can be managed with nonrigid fixation due to the muscular forces on the mandible resulting in compression at the inferior border."
3. Muscular forces at the angle are now favorable. Masseter and medial pterygoid compression forces at the inferior border of the angle become compressive (favorable) once the anterior arch is solid.

• Single Champy miniplate along the external oblique ridge (Champy's ideal osteosynthesis line)
• If unfavorable/displaced: two miniplates or a strut plate; extraoral approach may be needed

Summary Table

Why Not the Angle First?

• The anterior parasymphysis segment is still free-floating with muscular pull
• You have no stable anterior reference from which to judge the occlusion
• Any slight malreduction of the angle will displace the dental midline when you subsequently try to reduce the parasymphysis
• The result is near-guaranteed malocclusion

Key Biomechanical Note