• Mid – face distraction: Not performed until 3.5 years to ensure adequate bone stock.
• Distraction osteogenesis principle: Stress – tension principle.
• Zero latency period: Followed in children due to high osteogenic potential.
• Distraction histiogenesis: Simultaneous lengthening of soft tissue envelope with bone.
• Consolidation phase: 6 – 8 weeks (twice the time of initial distraction).
• Inverted L osteotomy: For advancements > 12 mm with counterclockwise rotation.
• BSSO limitation: Transverse movements are least possible.

Characteristics of Middle-Third Facial Fractures

Middle-third facial fractures, often referred to as "midfacial fractures," involve the central portion of the face, including the nasal bones, maxilla, and zygomatic arch. These fractures can result from various types of trauma, such as motor vehicle accidents, falls, or physical assaults. The following points highlight the key features and clinical implications of middle-third facial fractures:

1. Oedema of the Middle Third of the Face

• Rapid Development: Oedema (swelling) in the middle third of the face develops quickly after the injury, leading to a characteristic "balloon" appearance. This swelling is due to the accumulation of fluid in the soft tissues of the face.

• Absence of Deep Cervical Fascia: The unique anatomical structure of the middle third of the face contributes to this swelling. The absence of deep cervical fascia in this region allows for the rapid spread of fluid, resulting in pronounced oedema.

• Clinical Presentation: In the early stages following injury, patients with middle-third fractures often present with similar facial appearances due to the characteristic swelling. This can make diagnosis based solely on visual inspection challenging.

2. Lengthening of the Face

• Displacement of the Middle Third: The downward and backward displacement of the middle third of the facial skeleton can lead to an increase in the overall length of the face. This displacement forces the mandible to open, which can result in a change in occlusion, particularly in the molar region.

• Gagging of Occlusion: The altered position of the mandible can lead to a malocclusion, where the upper and lower teeth do not align properly. This can cause discomfort and difficulty in chewing or speaking.

• Delayed Recognition of Lengthening: The true increase in facial length may not be fully appreciated until the initial oedema subsides. As the swelling decreases, the changes in facial structure become more apparent.

3. Nasal Obstruction

• Blood Clots in the Nares: Following a middle-third fracture, the nares (nostrils) may become obstructed by blood clots, leading to nasal congestion. This can significantly impact the patient's ability to breathe through the nose.

• Mouth Breathing: Due to the obstruction, patients are often forced to breathe through their mouths, which can lead to additional complications, such as dry mouth and increased risk of respiratory infections.

• Gow – Gates landmarks:
  • Corner of mouth
  • Disto – palatal cusp of maxillary 2nd molar
  • Neck of condyle
  • Extraoral: Lower border of tragus
• Laryngeal mask airway (LMA): Supraglottic device
• Tracheostomy incision: 4–5 cm below cricoid cartilage
• Common tracheostomy complications:
  • Peri – op: Anterior jugular vein injury
  • Late: Innominate artery fistula

Extraction Patterns for Presurgical Orthodontics

In orthodontics, the extraction pattern chosen can significantly influence treatment outcomes, especially in presurgical orthodontics. The extraction decisions differ based on the type of skeletal malocclusion, specifically Class II and Class III malocclusions. Here’s an overview of the extraction patterns for each type:

Skeletal Class II Malocclusion

• General Approach:
  • In skeletal Class II malocclusion, the goal is to prepare the dental arches for surgical correction, typically involving mandibular advancement.
• Extraction Recommendations:
  • No Maxillary Tooth Extraction: Avoid extracting maxillary teeth, particularly the upper first premolars or any maxillary teeth, to prevent over-retraction of the maxillary anterior teeth. Over-retraction can compromise the planned mandibular advancement.
  • Lower First Premolar Extraction: Extraction of the lower first premolars is recommended. This helps:
    • Level the arch.
    • Correct the proclination of the lower anterior teeth, allowing for better alignment and preparation for surgery.

Skeletal Class III Malocclusion

• General Approach:

  • In skeletal Class III malocclusion, the extraction pattern is reversed to facilitate the surgical correction, often involving maxillary advancement or mandibular setback.

• Extraction Recommendations:

  • Upper First Premolar Extraction: Extracting the upper first premolars is done to:
    • Correct the proclination of the upper anterior teeth, which is essential for achieving proper alignment and aesthetics.
  • Lower Second Premolar Extraction: If additional space is needed in the lower arch, the extraction of lower second premolars is recommended. This helps:
    • Prevent over-retraction of the lower anterior teeth, maintaining their position while allowing for necessary adjustments in the arch.

Bone Healing: Primary vs. Secondary Intention

Bone healing is a complex biological process that can occur through different mechanisms, primarily classified into primary healing and secondary healing (or healing by secondary intention). Understanding these processes is crucial for effective management of fractures and optimizing recovery.

Secondary Healing (Callus Formation)

• Secondary healing is characterized by the formation of a callus, which is a temporary fibrous tissue that bridges the gap between fractured bone fragments. This process is often referred to as healing by secondary intention.

• Mechanism:

  • When a fracture occurs, the body initiates a healing response that involves inflammation, followed by the formation of a soft callus (cartilaginous tissue) and then a hard callus (bony tissue).
  • The callus serves as a scaffold for new bone formation and provides stability to the fracture site.
  • This type of healing typically occurs when the fractured fragments are approximated but not rigidly fixed, allowing for some movement at the fracture site.

• Closed Reduction: In cases where closed reduction is used, the fragments are aligned but may not be held in a completely stable position. This allows for the formation of a callus as the body heals.

Primary Healing (Direct Bone Union)

• Primary healing occurs when the fractured bone fragments are compressed against each other and held in place by rigid fixation, such as with bone plates and screws. This method prevents the formation of a callus and allows for direct bone union.

• Mechanism:

  • In primary healing, the fragments are in close contact, allowing for the migration of osteocytes and the direct remodeling of bone without the intermediate formation of a callus.
  • This process is facilitated by rigid fixation, which stabilizes the fracture and minimizes movement at the fracture site.
  • The healing occurs through a process known as Haversian remodeling, where the bone is remodeled along lines of stress, restoring its structural integrity.

• Indications for Primary Healing:

  • Primary healing is typically indicated in cases of:
    • Fractures that are surgically stabilized with internal fixation devices (e.g., plates, screws).
    • Fractures that require precise alignment and stabilization to ensure optimal healing and function.