Comprehensive Clinical Guide to Orthognathic Surgery and Dentofacial Deformities

Classification and Pathogenesis of Dentofacial Deformities

• Acquired Deformities: These are classified by a rapid onset. A specific event occurs suddenly—described as "bam"—leading to the immediate manifestation of an issue.

• Developmental Deformities: These occur slowly over an extended period. A primary named example is thumb sucking, which creates a deformity gradually through repetitive behavior.

• Functional Impacts: Dentofacial deformities affect multiple systems, including:

  • Mastication: The primary process of chewing.

  • Speech: Articulation and vocalization patterns.

  • TMJ and TMD: Issues related to the Temporomandibular Joint and disc issues, though surgical intervention is not always the immediate use-case for these specifically.

Maxillary Osteotomy: The LeFort Procedures

• Historical Context: The procedures are named after Renee Forte, who studied skull fracture patterns by throwing or smashing skulls to identify consistent lines of breakage.

• LeFort Classification:

  • LeFort I: The most common surgical modality used to correct the maxilla. It occurs at the level of the maxilla and nose, passing through the sinuses.

  • LeFort II: A fracture or surgical cut involving the nose.

  • LeFort III: Involves the entire facial complex.

• Surgical Procedure for LeFort I:

  • Access: An incision is made through the mucosa and muscle to reach the bone.

  • Osteotomy: A sagittal saw is used to cut through the bones at the LeFort I level.

  • Down Fracturing: A chisel is used to gently "tap tap tap" the back of the maxilla. This involves breaking very thick bones to mobilize the segment.

  • Pterygoid Plate (Transcript: aragoid plate): A "blind chisel" is placed back at the junction of the maxilla and the aragoid to fracture the plate.

  • Mobilization: After the bony cuts, row disinfaption forceps are used to gently mobilize and loosen the maxilla from its remaining attachments.

  • Fixation: Once positioned, the maxilla is secured using Grade 5 medical grade titanium plates. These are not active metals.

  • Custom Plates: Referred to as "surgery for dummies" by the speaker, custom plates use guides with pre-drilled holes, making the placement of the maxilla more precise and simple for complex cases like down positioning.

Surgical Assisted Rapid Palatal Expansion (SAP/SARPE)

• Purpose: Specifically used to address the transverse dimension (width) of the maxilla only. It is indicated for patients with a narrow maxilla where the suture has already fused.

• Procedure:

  • Surgical cuts are made similar to a LeFort procedure, but the maxilla is not down-fractured.

  • A palatal expander, similar to those used by orthodontists in children, is placed.

• Distraction Osteogenesis: The expansion occurs slowly, approximately $1\,mm$ per day. This process involves making a cut and allowing a callus to form. As the bone is slowly distracted, the body forms both new bone and soft tissue.

• Limitations and Capabilities:

  • Maxillary advancement via LeFort is typically limited to a maximum of approximately $14\,mm$.

  • Transverse expansion via SAP is usually between $6-10\,mm$.

Mandibular Procedures: BSSO and Others

• Bilateral Sagittal Split Osteotomy (BSSO) (Transcript: bilateral sido spodoscia): The most common procedure for the mandible. It separates the tooth-bearing portion of the mandible from the portion containing the condyle.

• Nerve Safety: A critical aspect of the procedure is protecting the inferior ovular nerve (transcript term). The surgeon finds the lingula where the nerve enters the bone and initiates the cut above it.

• Procedure Steps:

  • Dissection to reach the mandible and retract tissues including the lip and the matrix (retractor).

  • A cut is made through the cortex, followed by a "controlled fracture" using a chisel.

  • The jaw is opened and the nerve is freed in a "dance" of opening and retracting to avoid cutting or traumatizing the nerve.

• Mandibular Adjustments: The mandible can be moved forward (advancement) or backward (setback). It is then secured with titanium plates, screws, or a combination of both.

• External IVRO (Transcript: external EBRO): An Intraoral Vertical Ramus Osteotomy involving a cut behind the lingula. This is used to lengthen the ramus in patients with a very short ramus.

• Historical Methods: In the past, jaws were cut behind the nerve and wired shut. This is rarely done now due to the advent of rigid internal fixation (plates and screws).

Genioplasty and Genioglossus Advancement

• Genioplasty (Geneoplasty): A procedure performed on the chin itself to balance facial aesthetics.

  • The mental nerve is located, and a cut is made approximately $5\,mm$ below it.

  • The bone segment can be moved forward, backward, or have a wedge removed.

• Genioglossus Advancement: Used in sleep apnea cases to address the tongue's position.

  • The surgeon captures the tubercle (genial tubercle) where the Junior gloss (transcript term for genioglossus) muscle attaches.

  • This segment is pulled forward to prevent the tongue from collapsing and obstructing the posterior airway during sleep.

Clinical Protocols and Recovery (UAS/ERAS)

• UAS/ERAS Protocol: A specific protocol that allows for outpatient orthognathic surgery. Patients can go home a few hours after the procedure.

• Key Elements of the Protocol:

  • Minimizing fluids and narcotics.

  • Encouraging early movement.

  • No longer wiring the jaws shut; instead, light rubber bands are used.

• Recovery Timeline:

  • Six Weeks: The time required for the broken bone to fuse; no chewing or pressure is allowed during this phase.

  • Two to Three Weeks: Typical time off work, though many recover within a couple of weeks.

  • Swelling: Peak swelling lasts about a week or two, followed by a "puffy" phase.

  • Numbness: A common side effect of touching the nerves; it helps with initial pain but takes time to wear off. Sensation typically returns, especially in younger patients.

Case Studies and Specific Outcomes

• Developmental Distraction Case: A patient born early who swallowed noconium (transcript term) was intubated for $8$ months, resulting in an upper jaw that did not grow. A $20\,mm$ advancement was achieved using distraction plates and a stereolithic model to plan the vector. He also had underdeveloped lungs.

• Middle-Aged Advancement: A woman in her mid-$40s$ or $50s$ who underwent a large maxillary advancement. The speaker noted that for older women, this provides a "reverse facelift" by restoring lip support and facial projection.

• Sleep Apnea Case: A $35$-year-old male with an AHI of $118-130$ times per hour. He underwent a two-piece LeFort for expansion and advancement, plus a mandibular advancement. The total advancement at the pogonian (transcript term) was $30\,mm$, which is the speaker's maximum recorded advancement.

• Adolescent Surgery: Two cases of $15$-year-olds were shown. Surgery was performed early for psychosocial reasons despite the risk of future growth. One patient returned at age $22$ for a second surgery after further growth occurred.

• Asymmetry and Canting: A patient with a short right mandible and a canted maxilla was treated with a combination of BSSO, custom maxillary plates, bone grafting (from the septum, mandible, or iliac crest block), and a camouflage genioplasty.

• Invisalign (Visoline) Cases: Braceless surgery is possible. Small buttons are used during surgery, and temporary screws are placed in the jaw to hold guiding rubber bands post-operatively.

Questions & Discussion

• Q: Does the sinus get disrupted during a LeFort I?

• A: Yes, the surgeon cuts right through the sinus. During down-fracturing, the floor of the nose and the sinus are visible and the structures are essentially reproduced.

• Q: How do you reattach the masseter muscle?

• A: Typically, the masseter, medial teragoid, and lateral erogoid (transcript terms) do not need manual reattachment. The body is amazing and the muscles reattach themselves in the new position naturally. It is only required in cases of tumor removal with large defects.

• Q: Can you free-hand a genioplasty or do you need a guide?

• A: It can be free-handed, which the speaker likes because it allows for artistic adjustment. However, custom guides ("surgery for dummies" guides) are available but cost significant amounts of money. Guides are necessary for complex cases like a crooked chin that cannot be accurately free-handed.