NEET MDS Lessons
Oral and Maxillofacial Surgery
Fixation of Condylar Fractures
Condylar fractures of the mandible can be challenging to manage due to their location and the functional demands placed on the condylar region. Various fixation techniques have been developed to achieve stable fixation and promote healing. Below is an overview of the different methods of fixation for condylar fractures, including their advantages, disadvantages, and indications.
1. Miniplate Osteosynthesis
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Overview:
- Miniplate osteosynthesis involves the use of condylar plates and screw systems designed to withstand biochemical forces, minimizing micromotion at the fracture site.
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Primary Bone Healing:
- Under optimal conditions of stability and fracture reduction, primary bone healing can occur, allowing new bone to form along the fracture surface without the formation of fibrous tissue.
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Plate Placement:
- High condylar fractures may accommodate only one plate with two screws above and below the fracture line, parallel to the posterior border, providing adequate stability in most cases.
- For low condylar fractures, two plates may be required. The posterior plate should parallel the posterior ascending ramus, while the anterior plate can be angulated across the fracture line.
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Mechanical Advantage:
- The use of two miniplates at the anterior and posterior borders of the condylar neck restores tension and compression trajectories, neutralizing functional stresses in the condylar neck.
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Research Findings:
- Studies have shown that the double mini plate method is the only system able to withstand normal loading forces in cadaver mandibles.
2. Dynamic Compression Plating
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Overview:
- Dynamic compression plating is generally not recommended for condylar fractures due to the oblique nature of the fractures, which can lead to overlap of fragment ends and loss of ramus height.
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Current Practice:
- The consensus is that treatment is adequate with miniplates placed in a neutral mode, avoiding the complications associated with dynamic compression plating.
3. Lag Screw Osteosynthesis
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Overview:
- First described for condylar fractures by Wackerbauer in 1962, lag screws provide a biomechanically advantageous method of fixation.
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Mechanism:
- A true lag screw has threads only on the distal end, allowing for compression when tightened against the near cortex. This central placement of the screw enhances stability.
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Advantages:
- Rapid application of rigid fixation and close approximation of fractured parts due to significant compression generated.
- Less traumatic than miniplates, as there is no need to open the joint capsule.
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Disadvantages:
- Risk of lateralization and rotation of the condylar head if the screw is not placed centrally.
- Requires a steep learning curve for proper application.
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Contraindications:
- Not suitable for cases with loss of bone in the fracture gap or comminution that could lead to displacement when compression is applied.
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Popular Options:
- The Eckelt screw is one of the most widely used lag screws in current practice.
4. Pin Fixation
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Overview:
- Pin fixation involves the use of 1.3 mm Kirschner wires (K-wires) placed into the condyle under direct vision.
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Technique:
- This method requires an open approach to the condylar head and traction applied to the lower border of the mandible. A minimum of three convergent K-wires is typically needed to ensure stability.
5. Resorbable Pins and Plates
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Overview:
- Resorbable fixation devices may take more than two years to fully resorb. Materials used include self-reinforced poly-L-lactide screws (SR-PLLA), polyglycolide pins, and absorbable alpha-hydroxy polyesters.
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Indications:
- These materials are particularly useful in pediatric patients or in situations where permanent hardware may not be desirable.
Management and Treatment of Le Fort Fractures
Le Fort fractures require careful assessment and management to restore facial anatomy, function, and aesthetics. The treatment approach may vary depending on the type and severity of the fracture.
Le Fort I Fracture
Initial Assessment:
- Airway Management: Ensure the airway is patent, especially if there is significant swelling or potential for airway compromise.
- Neurological Assessment: Evaluate for any signs of neurological injury.
Treatment:
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Non-Surgical Management:
- Observation: In cases of non-displaced fractures, close monitoring may be sufficient.
- Pain Management: Analgesics to manage pain.
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Surgical Management:
- Open Reduction and Internal Fixation (ORIF): Indicated for displaced fractures to restore occlusion and facial symmetry.
- Maxillomandibular Fixation (MMF): May be used temporarily to stabilize the fracture during healing.
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Postoperative Care:
- Follow-Up: Regular follow-up to monitor healing and occlusion.
- Oral Hygiene: Emphasize the importance of maintaining oral hygiene to prevent infection.
Le Fort II Fracture
Initial Assessment:
- Airway Management: Critical due to potential airway compromise.
- Neurological Assessment: Evaluate for any signs of neurological injury.
Treatment:
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Non-Surgical Management:
- Observation: For non-displaced fractures, close monitoring may be sufficient.
- Pain Management: Analgesics to manage pain.
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Surgical Management:
- Open Reduction and Internal Fixation (ORIF): Required for displaced fractures to restore occlusion and facial symmetry.
- Maxillomandibular Fixation (MMF): May be used to stabilize the fracture during healing.
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Postoperative Care:
- Follow-Up: Regular follow-up to monitor healing and occlusion.
- Oral Hygiene: Emphasize the importance of maintaining oral hygiene to prevent infection.
Le Fort III Fracture
Initial Assessment:
- Airway Management: Critical due to potential airway compromise and significant facial swelling.
- Neurological Assessment: Evaluate for any signs of neurological injury.
Treatment:
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Non-Surgical Management:
- Observation: In cases of non-displaced fractures, close monitoring may be sufficient.
- Pain Management: Analgesics to manage pain.
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Surgical Management:
- Open Reduction and Internal Fixation (ORIF): Essential for restoring facial anatomy and occlusion. This may involve complex reconstruction of the midface.
- Maxillomandibular Fixation (MMF): Often used to stabilize the fracture during healing.
- Craniofacial Reconstruction: In cases of severe displacement or associated injuries, additional reconstructive procedures may be necessary.
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Postoperative Care:
- Follow-Up: Regular follow-up to monitor healing, occlusion, and any complications.
- Oral Hygiene: Emphasize the importance of maintaining oral hygiene to prevent infection.
- Physical Therapy: May be necessary to restore function and mobility.
General Considerations for All Le Fort Fractures
- Antibiotic Prophylaxis: Consideration for prophylactic antibiotics to prevent infection, especially in open fractures.
- Nutritional Support: Ensure adequate nutrition, especially if oral intake is compromised.
- Psychological Support: Address any psychological impact of facial injuries, especially in pediatric patients.
Pterygomandibular Space is an important anatomical area in the head and neck region, particularly relevant in dental and maxillofacial surgery. Understanding its boundaries, contents, and clinical significance is crucial for procedures such as local anesthesia, surgical interventions, and the management of infections. Here’s a detailed overview of the pterygomandibular space:
Boundaries of the Pterygomandibular Space
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Laterally:
- Medial Surface of the Ramus of the Mandible: This boundary is formed by the inner aspect of the ramus, which provides a lateral limit to the space.
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Medially:
- Lateral Surface of the Medial Pterygoid Muscle: The medial boundary is defined by the lateral aspect of the medial pterygoid muscle, which is a key muscle involved in mastication.
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Posteriorly:
- Deep Portion of the Parotid Gland: The posterior limit of the pterygomandibular space is formed by the deep part of the parotid gland, which is significant in terms of potential spread of infections.
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Anteriorly:
- Pterygomandibular Raphe: This fibrous band connects the pterygoid muscles and serves as the anterior boundary of the space.
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Roof:
- Lateral Pterygoid Muscle: The roof of the pterygomandibular space is formed by the lateral pterygoid muscle. The space just below this muscle communicates with the pharyngeal spaces, which is clinically relevant for the spread of infections.
Contents of the Pterygomandibular Space
The pterygomandibular space contains several important structures:
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Nerves:
- Lingual Nerve: This nerve provides sensory innervation to the anterior two-thirds of the tongue and is closely associated with the inferior alveolar nerve.
- Mandibular Nerve (V3): The third division of the trigeminal nerve, which supplies sensory and motor innervation to the lower jaw and associated structures.
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Vessels:
- Inferior Alveolar Artery: A branch of the maxillary artery that supplies blood to the lower teeth and surrounding tissues.
- Mylohyoid Nerve and Vessels: The mylohyoid nerve, a branch of the inferior alveolar nerve, innervates the mylohyoid muscle and the anterior belly of the digastric muscle.
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Connective Tissue:
- Loose Areolar Connective Tissue: This tissue provides a supportive framework for the structures within the pterygomandibular space and allows for some degree of movement and flexibility.
Clinical Significance
- Local Anesthesia: The pterygomandibular space is a common site for administering local anesthesia, particularly for inferior alveolar nerve blocks, which are essential for dental procedures involving the lower jaw.
- Infection Spread: Due to its anatomical connections, infections in the pterygomandibular space can spread to adjacent areas, including the parotid gland and the pharyngeal spaces, necessitating careful evaluation and management.
- Surgical Considerations: Knowledge of the boundaries and contents of this space is crucial during surgical procedures in the mandible and surrounding areas to avoid damaging important nerves and vessels.
Axial Compression in Bone Fixation
Axial compression refers to a surgical technique used in the fixation of fractured bones, where the bony ends are brought into close proximity, minimizing the inter-fragmentary gap. This technique is crucial for achieving stable fixation and promoting optimal healing of fractures, particularly in the context of internal fixation using plates and screws.
Key Concepts of Axial Compression
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Close Proximity of Bony Ends:
- In axial compression, the fractured ends of the bone are aligned closely together, which is essential for effective healing. The minimal inter-fragmentary gap allows for direct contact between the bone surfaces, facilitating the healing process.
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Functional Dynamic Forces:
- During normal activities, such as chewing (masticatory function), dynamic forces are generated. These forces can create stress at the fracture site, which must be countered by the static forces provided by the fixation devices (plates and screws).
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Static Forces from Plates and Screws:
- The stability of the fracture fixation relies on the ability of the plates and screws to provide sufficient static forces to counteract the dynamic forces generated during function. This is critical for maintaining the alignment of the fracture and preventing displacement.
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Plate and Screw Specifications:
- Plate Thickness: Plates with a thickness of 2 mm are commonly used, as they provide adequate strength and stability while minimizing soft tissue irritation.
- Screw Specifications: Bi-cortical screws with a diameter of 2.7 mm are typically employed. These screws engage both cortices of the bone, enhancing stability and fixation strength.
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Principle of Inclined Plane:
- The design of the holes in the plate and the head of the screws operates on the principle of an inclined plane. This design allows for the application of compressive forces when the screws are tightened, effectively drawing the bony fragments together.
- As the screws are tightened, they create a compressive force that helps to stabilize the fracture and maintain the alignment of the bone fragments.
Advantages of Axial Compression
- Enhanced Stability: By minimizing the inter-fragmentary gap and providing strong static forces, axial compression enhances the stability of the fracture fixation.
- Promotes Healing: Close approximation of the bony ends facilitates the healing process by allowing for direct contact and reducing the risk of non-union or malunion.
- Functional Restoration: Effective axial compression allows patients to regain function more quickly, as the fixation can withstand the dynamic forces generated during normal activities.
Surgical Considerations for the Submandibular and Parotid Glands
When performing surgery on the submandibular and parotid glands, it is crucial to be aware of the anatomical structures and nerves at risk to minimize complications. Below is an overview of the key nerves and anatomical landmarks relevant to these surgical procedures.
Major Nerves at Risk During Submandibular Gland Surgery
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Hypoglossal Nerve (CN XII):
- This nerve is responsible for motor innervation to the muscles of the tongue. It lies deep to the submandibular gland and is at risk during surgical manipulation in this area.
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Marginal Mandibular Nerve:
- A branch of the facial nerve (CN VII), the marginal mandibular nerve innervates the muscles of the lower lip and chin. It runs just deep to the superficial layer of the deep cervical fascia, below the platysma muscle, making it vulnerable during submandibular gland surgery.
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Lingual Nerve:
- The lingual nerve provides sensory innervation to the anterior two-thirds of the tongue and carries parasympathetic fibers to the submandibular gland via the submandibular ganglion. It is located in close proximity to the submandibular gland and is at risk during dissection.
Anatomical Considerations for Parotid Gland Surgery
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Parotid Fascia:
- The parotid gland is encased in a capsule of parotid fascia, which provides a protective layer during surgical procedures.
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Facial Nerve (CN VII):
- The facial nerve is a critical structure to identify during parotid
gland surgery to prevent injury. Key landmarks for locating the facial
nerve include:
- Tympanomastoid Suture Line: This is a reliable landmark for identifying the main trunk of the facial nerve, which lies just deep and medial to this suture.
- Tragal Pointer: The nerve is located about 1 cm deep and inferior to the tragal pointer, although this landmark is less reliable.
- Posterior Belly of the Digastric Muscle: This muscle provides a reference for the approximate depth of the facial nerve.
- Peripheral Buccal Branches: While following these branches can help identify the nerve, this should not be the standard approach due to the risk of injury.
- The facial nerve is a critical structure to identify during parotid
gland surgery to prevent injury. Key landmarks for locating the facial
nerve include:
Submandibular Gland Anatomy
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Location:
- The submandibular gland is situated in the submandibular triangle of the neck, which is bordered by the mandible and the digastric muscles.
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Mylohyoid Muscle:
- The gland wraps around the mylohyoid muscle, which is typically retracted anteriorly during surgery to provide better exposure of the gland.
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CN XII:
- The hypoglossal nerve lies deep to the submandibular gland, making it important to identify and protect during surgical procedures.
Odontogenic Keratocyst (OKC)
The odontogenic keratocyst (OKC) is a unique and aggressive cystic lesion of the jaw with distinct histological features and a high recurrence rate. Below is a comprehensive overview of its characteristics, treatment options, and prognosis.
Characteristics of Odontogenic Keratocyst
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Definition and Origin:
- The term "odontogenic keratocyst" was first introduced by Philipsen in 1956. It is believed to originate from remnants of the dental lamina or basal cells of the oral epithelium.
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Biological Behavior:
- OKCs exhibit aggressive behavior and have a recurrence rate of 13% to 60%. They are considered to have a neoplastic nature rather than a purely developmental origin.
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Histological Features:
- The cyst lining is typically 6 to 10 cells thick, with a palisaded basal cell layer and a surface of corrugated parakeratin.
- The epithelium may produce orthokeratin (10%), parakeratin (83%), or both (7%).
- No rete ridges are present, and mitotic activity is frequent, contributing to the cyst's growth pattern.
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Types:
- Orthokeratinized OKC: Less aggressive, lower recurrence rate, often associated with dentigerous cysts.
- Parakeratinized OKC: More aggressive with a higher recurrence rate.
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Clinical Features:
- Age: Peak incidence occurs in individuals aged 20 to 30 years.
- Gender: Predilection for males (approximately 1:5 male to female ratio).
- Location: More commonly found in the mandible, particularly in the ramus and third molar area. In the maxilla, the third molar area is also a common site.
- Symptoms: Patients may be asymptomatic, but symptoms can include pain, soft-tissue swelling, drainage, and paresthesia of the lip or teeth.
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Radiographic Features:
- Typically appears as a unilocular lesion with a well-defined peripheral rim, although multilocular varieties (20%) can occur.
- Scalloping of the borders is often present, and it may be associated with the crown of a retained tooth (40%).
Treatment Options for Odontogenic Keratocyst
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Surgical Excision:
- Enucleation: Complete removal of the cyst along with the surrounding tissue.
- Curettage: Scraping of the cyst lining after enucleation to remove any residual cystic tissue.
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Chemical Cauterization:
- Carnoy’s Solution: Application of Carnoy’s solution (6 ml absolute alcohol, 3 ml chloroform, and 1 ml acetic acid) after enucleation and curettage can help reduce recurrence rates. It penetrates the bone and can assist in freeing the cyst from the bone wall.
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Marsupialization:
- This technique involves creating a window in the cyst to allow for drainage and reduction in size, which can be beneficial in larger cysts or in cases where complete excision is not feasible.
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Primary Closure:
- After enucleation and curettage, the site may be closed primarily or packed open to allow for healing.
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Follow-Up:
- Regular follow-up is essential due to the high recurrence rate. Patients should be monitored for signs of recurrence, especially in the first few years post-treatment.
Prognosis
- The prognosis for OKC is variable, with a significant recurrence rate attributed to the aggressive nature of the lesion and the potential for residual cystic tissue.
- Recurrence is not necessarily related to the size of the cyst or the presence of satellite cysts but is influenced by the nature of the lesion itself and the presence of dental lamina remnants.
- Multilocular lesions tend to have a higher recurrence rate compared to unilocular ones.
- Surgical technique does not significantly influence the likelihood of relapse.
Associated Conditions
- Multiple OKCs can be seen in syndromes such as:
- Nevoid Basal Cell Carcinoma Syndrome (Gorlin-Goltz Syndrome)
- Marfan Syndrome
- Ehlers-Danlos Syndrome
- Noonan Syndrome
Danger Space: Anatomy and Clinical Significance
The danger space is an anatomical potential space located between the alar fascia and the prevertebral fascia. Understanding this space is crucial in the context of infections and their potential spread within the neck and thoracic regions.
Anatomical Extent
- Location: The danger space extends from the base of the skull down to the posterior mediastinum, reaching as far as the diaphragm. This extensive reach makes it a significant pathway for the spread of infections.
Pathway for Infection Spread
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Oropharyngeal Infections: Infections originating in the oropharynx can spread to the danger space through the retropharyngeal space. The retropharyngeal space is a potential space located behind the pharynx and is clinically relevant in the context of infections, particularly in children.
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Connection to the Posterior Mediastinum: The danger space is continuous with the posterior mediastinum, allowing for the potential spread of infections from the neck to the thoracic cavity.
Mechanism of Infection Spread
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Retropharyngeal Space: The spread of infection from the retropharyngeal space to the danger space typically occurs at the junction where the alar fascia and visceral fascia fuse, particularly between the cervical vertebrae C6 and T4.
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Rupture of Alar Fascia: Infection can spread by rupturing through the alar fascia, which can lead to serious complications, including mediastinitis, if the infection reaches the posterior mediastinum.
Clinical Implications
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Infection Management: Awareness of the danger space is critical for healthcare providers when evaluating and managing infections of the head and neck. Prompt recognition and treatment of oropharyngeal infections are essential to prevent their spread to the danger space and beyond.
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Surgical Considerations: Surgeons must be cautious during procedures involving the neck to avoid inadvertently introducing infections into the danger space or to recognize the potential for infection spread during surgical interventions.