NEET MDS Lessons
Oral and Maxillofacial Surgery
- Cribriform plate: Roof of olfactory region
- Nasolacrimal duct: Opens into inferior meatus; post – DCR → middle meatus
- Ethmoidal nerves:
- Anterior: Nasal septum, mucosa, skin
- Posterior: Ethmoidal & sphenoidal sinuses
- Infraorbital fissure: ~20 mm from orbital rim
- Superior orbital fissure: ~35 mm from frontozygomatic suture
- Optic canal: ≥42 mm from anterior lacrimal crest
Nasogastric Tube (Ryles Tube)
A nasogastric tube (NG tube), commonly referred to as a Ryles tube, is a medical device used for various purposes, primarily involving the stomach. It is a long, hollow tube made of polyvinyl chloride (PVC) with one blunt end and multiple openings along its length. The tube is designed to be inserted through the nostril, down the esophagus, and into the stomach.
Description and Insertion
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Structure: The NG tube has a blunt end that is inserted into the nostril, and it features multiple openings to allow for the passage of fluids and air. The open end of the tube is used for feeding or drainage.
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Insertion Technique:
- The tube is gently passed through one of the nostrils and advanced through the nasopharynx and into the esophagus.
- Care is taken to ensure that the tube follows the natural curvature of the nasal passages and esophagus.
- Once the tube is in place, its position must be confirmed before any feeds or medications are administered.
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Position Confirmation:
- To check the position of the tube, air is pushed into the tube using a syringe.
- The presence of air in the stomach is confirmed by auscultation with a stethoscope, listening for the characteristic "whoosh" sound of air entering the stomach.
- Only after confirming that the tube is correctly positioned in the stomach should feeding or medication administration begin.
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Securing the Tube: The tube is fixed to the nose using sticking plaster or adhesive tape to prevent displacement.
Uses of Nasogastric Tube
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Nutritional Support:
- Enteral Feeding: The primary use of a nasogastric
tube is to provide nutritional support to patients who are unable to
take oral feeds due to various reasons, such as:
- Neurological conditions (e.g., stroke, coma)
- Surgical procedures affecting the gastrointestinal tract
- Severe dysphagia (difficulty swallowing)
- Enteral Feeding: The primary use of a nasogastric
tube is to provide nutritional support to patients who are unable to
take oral feeds due to various reasons, such as:
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Gastric Lavage:
- Postoperative Care: NG tubes can be used for gastric lavage to flush out blood, fluids, or other contents from the stomach after surgery. This is particularly important in cases where there is a risk of aspiration or when the stomach needs to be emptied.
- Poisoning: In cases of poisoning or overdose, gastric lavage may be performed using an NG tube to remove toxic substances from the stomach. This procedure should be done promptly and under medical supervision.
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Decompression:
- Relieving Distension: The NG tube can also be used to decompress the stomach in cases of bowel obstruction or ileus, allowing for the removal of excess gas and fluid.
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Medication Administration:
- The tube can be used to administer medications directly into the stomach for patients who cannot take oral medications.
Considerations and Complications
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Patient Comfort: Insertion of the NG tube can be uncomfortable for patients, and proper technique should be used to minimize discomfort.
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Complications: Potential complications include:
- Nasal and esophageal irritation or injury
- Misplacement of the tube into the lungs, leading to aspiration
- Sinusitis or nasal ulceration with prolonged use
- Gastrointestinal complications, such as gastric erosion or ulceration
Approaches to the Oral Cavity in Oral Cancer Treatment
In the management of oral cancer, surgical approaches are tailored to the location and extent of the lesions. The choice of surgical technique is crucial for achieving adequate tumor resection while preserving surrounding structures and function. Below are the primary surgical approaches used in the treatment of oral cancer:
1. Peroral Approach
- Indication: This approach is primarily used for small, anteriorly placed lesions within the oral cavity.
- Technique: The surgeon accesses the lesion directly through the mouth without external incisions. This method is less invasive and is suitable for superficial lesions that do not require extensive resection.
- Advantages:
- Minimal morbidity and scarring.
- Shorter recovery time.
- Limitations: Not suitable for larger or posterior lesions due to limited visibility and access.
2. Lip Split Approach
- Indication: This approach is utilized for posteriorly based lesions in the gingivobuccal complex and for performing marginal mandibulectomy.
- Technique: A vertical incision is made through the lip, allowing for the elevation of a cheek flap. This provides better access to the posterior aspects of the oral cavity and the mandible.
- Advantages:
- Improved access to the posterior oral cavity.
- Facilitates the removal of larger lesions and allows for better visualization of the surgical field.
- Limitations: Potential for cosmetic concerns and longer recovery time compared to peroral approaches.
3. Pull-Through Approach
- Indication: This technique is particularly useful for lesions of the tongue and floor of the mouth, especially when the posterior margin is a concern for peroral excision.
- Technique: The lesion is accessed by pulling the tongue or floor of the mouth forward, allowing for better exposure and resection of the tumor while ensuring adequate margins.
- Advantages:
- Enhanced visibility and access to the posterior margins of the lesion.
- Allows for more precise excision of tumors located in challenging areas.
- Limitations: May require additional incisions or manipulation of surrounding tissues, which can increase recovery time.
4. Mandibulotomy (Median or Paramedian)
- Indication: This approach is indicated for tongue and floor of mouth lesions that are close to the mandible, particularly when achieving a lateral margin of clearance is critical.
- Technique: A mandibulotomy involves making an incision through the mandible, either in the midline (median) or slightly off-center (paramedian), to gain access to the oral cavity and the lesion.
- Advantages:
- Provides excellent access to deep-seated lesions and allows for adequate resection with clear margins.
- Facilitates reconstruction if needed.
- Limitations: Higher morbidity associated with mandibular manipulation, including potential complications such as nonunion or malocclusion.
Patient Factors
- Age: Younger patients have better recovery potential
- Health status: Diabetes, smoking impair healing
- Nutritional status: Adequate protein, vitamins essential
- Compliance: Follow-up and protection important
Injury Factors
- Mechanism: Sharp cuts better than crush injuries
- Timing: Earlier repair generally better
- Location: Proximal injuries may have better outcomes
- Associated damage: Soft tissue trauma affects healing
Surgical Factors
- Technique: Precise, tension-free repair crucial
- Experience: Microsurgical expertise important
- Equipment: Adequate magnification and instruments
- Tissue handling: Gentle technique minimizes trauma
Expected Outcomes
Sensory Recovery Patterns
- Protective sensation: Usually returns first
- Touch sensation: Gradual improvement
- Two-point discrimination: Last to recover, may remain impaired
- Timeline: Improvement over 6-24 months
Functional Outcomes
- Speech: Usually not significantly affected
- Chewing: May adapt to altered sensation
- Quality of life: Variable impact, counseling important
- Patient satisfaction: Related to realistic expectations
Success Rates
- Direct repair: 60-80% meaningful recovery
- Nerve grafting: 40-70% meaningful recovery
- Factors: Depend on injury severity, patient age, surgical technique
Augmentation of the Inferior Border of the Mandible
Mandibular augmentation refers to surgical procedures aimed at increasing the height or contour of the mandible, particularly the inferior border. This type of augmentation is often performed to improve the support for dentures, enhance facial aesthetics, or correct deformities. Below is an overview of the advantages and disadvantages of augmenting the inferior border of the mandible.
Advantages of Inferior Border Augmentation
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Preservation of the Vestibule:
- The procedure does not obliterate the vestibule, allowing for the immediate placement of an interim denture. This is particularly beneficial for patients who require prosthetic support soon after surgery.
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No Change in Vertical Dimension:
- Augmentation of the inferior border does not alter the vertical dimension of the occlusion, which is crucial for maintaining proper bite relationships and avoiding complications associated with changes in jaw alignment.
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Facilitation of Secondary Vestibuloplasty:
- The procedure makes subsequent vestibuloplasty easier. By maintaining the vestibular space, it allows for better access and manipulation during any future surgical interventions aimed at deepening the vestibule.
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Protection of the Graft:
- The graft used for augmentation is not subjected to direct masticatory forces, reducing the risk of graft failure and promoting better healing. This is particularly important in ensuring the longevity and stability of the augmentation.
Disadvantages of Inferior Border Augmentation
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Extraoral Scar:
- The procedure typically involves an incision that can result in an extraoral scar. This may be a cosmetic concern for some patients, especially if the scar is prominent or does not heal well.
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Potential Alteration of Facial Appearance:
- If the submental and submandibular tissues are not initially loose, there is a risk of altering the facial appearance. Tight or inelastic tissues may lead to distortion or asymmetry postoperatively.
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Limited Change in Superior Surface Shape:
- The augmentation primarily affects the inferior border of the mandible and may not significantly change the shape of the superior surface of the mandible. This limitation can affect the overall contour and aesthetics of the jawline.
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Surgical Risks:
- As with any surgical procedure, there are inherent risks, including infection, bleeding, and complications related to anesthesia. Additionally, there may be risks associated with the grafting material used.
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.
Antral Puncture and Intranasal Antrostomy
Antral puncture, also known as intranasal antrostomy, is a surgical procedure performed to access the maxillary sinus for diagnostic or therapeutic purposes. This procedure is commonly indicated in cases of chronic sinusitis, sinus infections, or to facilitate drainage of the maxillary sinus. Understanding the anatomical considerations and techniques for antral puncture is essential for successful outcomes.
Anatomical Considerations
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Maxillary Sinus Location:
- The maxillary sinus is one of the paranasal sinuses located within the maxilla (upper jaw) and is situated laterally to the nasal cavity.
- The floor of the maxillary sinus is approximately 1.25 cm below the floor of the nasal cavity, making it accessible through the nasal passages.
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Meatuses of the Nasal Cavity:
- The nasal cavity contains several meatuses, which are passageways
that allow for drainage of the sinuses:
- Middle Meatus: Located between the middle and inferior nasal conchae, it is the drainage pathway for the frontal, maxillary, and anterior ethmoid sinuses.
- Inferior Meatus: Located below the inferior nasal concha, it primarily drains the nasolacrimal duct.
- The nasal cavity contains several meatuses, which are passageways
that allow for drainage of the sinuses:
Technique for Antral Puncture
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Indications:
- Antral puncture is indicated for:
- Chronic maxillary sinusitis.
- Accumulation of pus or fluid in the maxillary sinus.
- Diagnostic aspiration for culture and sensitivity testing.
- Antral puncture is indicated for:
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Puncture Site:
- In Children: The puncture should be made through the middle meatus. This approach is preferred due to the anatomical differences in children, where the maxillary sinus is relatively smaller and more accessible through this route.
- In Adults: The puncture is typically performed through the inferior meatus. This site allows for better drainage and is often used for therapeutic interventions.
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Procedure:
- The patient is positioned comfortably, usually in a sitting or semi-reclined position.
- Local anesthesia is administered to minimize discomfort.
- A needle (often a 16-gauge or larger) is inserted through the chosen meatus into the maxillary sinus.
- Aspiration is performed to confirm entry into the sinus, and any fluid or pus can be drained.
- If necessary, saline may be irrigated into the sinus to help clear debris or infection.
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Post-Procedure Care:
- Patients may be monitored for any complications, such as bleeding or infection.
- Antibiotics may be prescribed if an infection is present or suspected.
- Follow-up appointments may be necessary to assess healing and sinus function.