Distraction Osteogenesis

When was the field of craniofacial surgery established?

In 1967 after publication of Paul Tessier’s work in the paper “Osteotomies totales de face, Syndrome de Crouzon, Syndrome D’Apert, Oxycephalies, Scaphocephalies, Turricephalies.”

What are the main insights that have helped to overcome the limitations in craniofacial surgery over the past 25 years?

Understanding of the pathologic anatomy through better imaging (3D CT scan), extensive bone grafting of bony defects, rigid fixation of osteotomized segments, and most recently, the evolving applications of distraction osteogenesis.

What is distraction osteogenesis?

A concept of fixation that actively mobilizes osteotomy segments and promotes osteogenesis. Also known as callostasis (stretching of callus, as in a fracture).

What is the concept of distraction osteogenesis?

1. Distraction zone: location of the bone separation by osteotomy or corticotomy

2. Latency period: time allowed for reparative callus formation in the distraction zone

3. Activation period: gradual distraction forces applied to callus, elongation of callus under tension

4. Consolidation period: external fixation maintained after activation, allows consolidation of distraction generate.

What are the advantages of distraction osteogenesis?

Reduced risk of infection seen in nonvascularized bone grafts, eliminated need for a donor site hence no donor site morbidity or limitations, simple design, more predictable bone survival, potential for three-dimensional changes, reduced operative blood loss, reduced number of subsequent procedures, possibility of repeated applications, avoids in situ metal plates and screws or maxillomandibular fixation (MMF), early closure of tracheostomy in cases of micrognathia, ability to be used in irradiated bone, well tolerated, no known evidence of growth retardation, possibility of better aesthetic results.

True/False: Distraction osteogenesis has a higher rate of morbidity and greater need for secondary midface procedures compared to bone grafting.

False.

True/False: Distraction osteogenesis actually causes enlargement of the overlying surrounding tissue via histiogenesis.

True.

What are the disadvantages of mandibular distraction osteogenesis?

Hypertrophic scarring at pin site (most common disadvantage), pin tract infection (osteomyelitis not reported to date), pin extrusion or migration, facial nerve injury, sensory deficits of inferior alveolar nerve, intolerance or noncompliance (uncommon), dentigerous cyst formation, ankylosis, tooth bud injury in patients younger than 1 year, may still require secondary procedures.

How is new bone formed during distraction osteogenesis?

Intramembranous ossification.

True/False: Distraction is a unique form of fracture healing that occurs in the craniofacial skeleton without a cartilaginous intermediate.

True.

What are the zones of distraction osteogenesis that result in mature bone formation?

Zone of fibrous tissue (zone I): the fibrous interzone (FIZ) is composed of highly organized, longitudinally oriented, parallel strands of collagen with spindle-shaped fibroblasts and undifferentiated mesenchymal precursor cells through the matrix. Central region of the distraction gap.

Zone of extending bone formation (zone II): the primary mineralization front (PMF) found on both the edges of the FIZ composed of fibroblasts and undifferentiated mesenchymal precursor cells in direct continuity with osteoblasts on the surface of bone spicules (osteoblasts longitudinally oriented and parallel to direction of distraction). Spindle-shaped fibroblastic cells transform into bone-forming cells. Increased levels of alkaline phosphatase, pyruvic acid, and lactic acid. Also known as the transitional zone.

Zone of bone remodeling (zone III): advancing fields of bone resorption and apposition, increased number of osteoclasts.

Zone of mature bone (zone IV): early compact cortical bone located adjacent to mature bone in unexpanded areas. Bone spicules thicker, less longitudinal orientation.

When are chondrocytes present during distraction osteogenesis?