NEET MDS Lessons
Oral and Maxillofacial Surgery
Hemostatic Agents
Hemostatic agents are critical in surgical procedures to control bleeding and promote wound healing. Various materials are used, each with unique properties and mechanisms of action. Below is a detailed overview of some commonly used hemostatic agents, including Gelfoam, Oxycel, Surgical (Oxycellulose), and Fibrin Glue.
1. Gelfoam
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Composition: Gelfoam is made from gelatin and has a sponge-like structure.
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Mechanism of Action:
- Gelfoam does not have intrinsic hemostatic properties; its hemostatic effect is primarily due to its large surface area, which comes into contact with blood.
- When Gelfoam absorbs blood, it swells and exerts pressure on the bleeding site, providing a scaffold for the formation of a fibrin network.
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Application:
- Gelfoam should be moistened in saline or thrombin solution before application to ensure optimal performance. It is essential to remove all air from the interstices to maximize its effectiveness.
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Absorption: Gelfoam is absorbed by the body through phagocytosis, typically within a few weeks.
2. Oxycel
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Composition: Oxycel is made from oxidized cellulose.
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Mechanism of Action:
- Upon application, Oxycel releases cellulosic acid, which has a strong affinity for hemoglobin, leading to the formation of an artificial clot.
- The acid produced during the wetting process can inactivate thrombin and other hemostatic agents, which is why Oxycel should be applied dry.
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Limitations:
- The acid produced can inhibit epithelialization, making Oxycel unsuitable for use over epithelial surfaces.
3. Surgical (Oxycellulose)
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Composition: Surgical is a glucose polymer-based sterile knitted fabric created through the controlled oxidation of regenerated cellulose.
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Mechanism of Action:
- The local hemostatic mechanism relies on the binding of hemoglobin to oxycellulose, allowing the dressing to expand into a gelatinous mass. This mass acts as a scaffold for clot formation and stabilization.
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Application:
- Surgical can be applied dry or soaked in thrombin solution, providing flexibility in its use.
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Absorption: It is removed by liquefaction and phagocytosis over a period of one week to one month. Unlike Oxycel, Surgical does not inhibit epithelialization and can be used over epithelial surfaces.
4. Fibrin Glue
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Composition: Fibrin glue is a biological adhesive that contains thrombin, fibrinogen, factor XIII, and aprotinin.
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Mechanism of Action:
- Thrombin converts fibrinogen into an unstable fibrin clot, while factor XIII stabilizes the clot. Aprotinin prevents the degradation of the clot.
- During wound healing, fibroblasts migrate through the fibrin meshwork, forming a more permanent framework composed of collagen fibers.
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Applications:
- Fibrin glue is used in various surgical procedures to promote hemostasis and facilitate tissue adhesion. It is particularly useful in areas where traditional sutures may be challenging to apply.
Surgical Approaches in Oral and Maxillofacial Surgery
In the management of tumors and lesions in the oral and maxillofacial region, various surgical approaches are employed based on the extent of the disease, the involvement of surrounding structures, and the need for reconstruction. Below is a detailed overview of the surgical techniques mentioned, along with their indications and reconstruction options.
1. Marginal / Segmental / En Bloc Resection
Definition:
- En Bloc Resection: This technique involves the complete removal of a tumor along with a margin of healthy tissue, without disrupting the continuity of the bone. It is often used for tumors that are well-defined and localized.
Indications:
- No Cortical Perforation: En bloc segmental resection is indicated when there is no evidence of cortical bone perforation. This allows for the removal of the tumor while preserving the structural integrity of the surrounding bone.
- Tumor Characteristics: This approach is suitable for benign tumors or low-grade malignancies that have not invaded surrounding tissues.
2. Partial Resection (Mandibulectomy)
Definition:
- Mandibulectomy: This procedure involves the resection of a portion of the mandible, typically performed when a tumor is present.
Indications:
- Cortical Perforation: Mandibulectomy is indicated when there is cortical perforation of the mandible. This means that the tumor has invaded the cortical bone, necessitating a more extensive surgical approach.
- Clearance Margin: A margin of at least 1 cm of healthy bone is typically removed to ensure complete excision of the tumor and reduce the risk of recurrence.
3. Total Resection (Hemimandibulectomy)
Definition:
- Hemimandibulectomy: This procedure involves the resection of one half of the mandible, including the associated soft tissues.
Indications:
- Perforation of Bone and Soft Tissue: Hemimandibulectomy is indicated when there is both perforation of the bone and involvement of the surrounding soft tissues. This is often seen in more aggressive tumors or those that have metastasized.
- Extensive Tumor Involvement: This approach is necessary for tumors that cannot be adequately removed with less invasive techniques due to their size or location.
4. Reconstruction
Following resection, reconstruction of the jaw is often necessary to restore function and aesthetics. Several options are available for reconstruction:
a. Reconstruction Plate:
- Description: A reconstruction plate is a rigid plate made of titanium or other biocompatible materials that is used to stabilize the bone after resection.
- Indications: Used in cases where structural support is needed to maintain the shape and function of the mandible.
b. K-wire:
- Description: K-wires are thin, flexible wires used to stabilize bone fragments during the healing process.
- Indications: Often used in conjunction with other reconstruction methods to provide additional support.
c. Titanium Mesh:
- Description: Titanium mesh is a flexible mesh that can be shaped to fit the contours of the jaw and provide support for soft tissue and bone.
- Indications: Used in cases where there is significant bone loss and soft tissue coverage is required.
d. Rib Graft / Iliac Crest Graft:
- Description: Autogenous bone grafts can be harvested from the rib or iliac crest to reconstruct the mandible.
- Indications: These grafts are used when significant bone volume is needed for reconstruction, providing a biological scaffold for new bone formation.
Transoral Lithotomy: Procedure for Submandibular Duct Stone Removal
Transoral lithotomy is a surgical technique used to remove stones (calculi) from the submandibular duct (Wharton's duct). This procedure is typically performed under local anesthesia and is effective for addressing sialolithiasis (the presence of stones in the salivary glands).
Procedure
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Preoperative Preparation:
- Radiographic Assessment: The exact location of the stone is determined using imaging studies, such as X-rays or ultrasound, to guide the surgical approach.
- Local Anesthesia: The procedure is performed under local anesthesia to minimize discomfort for the patient.
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Surgical Technique:
- Suture Placement: A suture is placed behind the stone to prevent it from moving backward during the procedure, facilitating easier access.
- Incision: An incision is made in the mucosa of the
floor of the mouth, parallel to the duct. Care is taken to avoid injury
to surrounding structures, including:
- Lingual Nerve: Responsible for sensory innervation to the tongue.
- Submandibular Gland: The gland itself should be preserved to maintain salivary function.
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Blunt Dissection:
- After making the incision, blunt dissection is performed to carefully displace the surrounding tissue and expose the duct.
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Identifying the Duct:
- The submandibular duct is located, and the segment of the duct that contains the stone is identified.
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Stone Removal:
- A longitudinal incision is made over the stone within the duct. The stone is then extracted using small forceps. Care is taken to ensure complete removal to prevent recurrence.
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Postoperative Considerations:
- After the stone is removed, the incision may be closed with sutures, and the area is monitored for any signs of complications.
Complications
- Bacterial Sialadenitis: If there is a secondary infection following the procedure, it can lead to bacterial sialadenitis, which is an inflammation of the salivary gland due to infection. Symptoms may include pain, swelling, and purulent discharge from the duct.
Mandibular Tori
Mandibular tori are bony growths that occur on the mandible, typically on the lingual aspect of the alveolar ridge. While they are often asymptomatic, there are specific indications for their removal, particularly when they interfere with oral function or prosthetic rehabilitation.
Indications for Removal
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Interference with Denture Construction:
- Mandibular tori may obstruct the proper fitting of full or partial dentures, necessitating their removal to ensure adequate retention and comfort.
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Ulceration and Slow Healing:
- If the mucosal covering over the torus ulcerates and the wound exhibits extremely slow healing, surgical intervention may be required to promote healing and prevent further complications.
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Interference with Speech and Deglutition:
- Large tori that impede normal speech or swallowing may warrant removal to improve the patient's quality of life and functional abilities.
Surgical Technique
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Incision Placement:
- The incision should be made on the crest of the ridge if the patient is edentulous (without teeth). This approach allows for better access to the torus while minimizing trauma to surrounding tissues.
- If there are teeth present in the area, the incision should be made along the gingival margin. This helps to preserve the integrity of the gingival tissue and maintain aesthetics.
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Avoiding Direct Incision Over the Torus:
- It is crucial not to make the incision directly over the torus.
Incising over the torus can lead to:
- Status Line: Leaving a visible line on the traumatized bone, which can affect aesthetics and function.
- Thin Mucosa: The mucosa over the torus is generally very thin, and an incision through it can result in dehiscence (wound separation) and exposure of the underlying bone, complicating healing.
- It is crucial not to make the incision directly over the torus.
Incising over the torus can lead to:
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Surgical Procedure:
- After making the appropriate incision, the mucosal flap is elevated to expose the underlying bone.
- The torus is then carefully removed using appropriate surgical instruments, ensuring minimal trauma to surrounding tissues.
- Hemostasis is achieved, and the mucosal flap is repositioned and sutured back into place.
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Postoperative Care:
- Patients may experience discomfort and swelling following the procedure, which can be managed with analgesics.
- Instructions for oral hygiene and dietary modifications may be provided to promote healing and prevent complications.
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Follow-Up:
- Regular follow-up appointments are necessary to monitor healing and assess for any potential complications, such as infection or delayed healing.
Lateral Pharyngeal Space
The lateral pharyngeal space is an important anatomical area in the neck that plays a significant role in various clinical conditions, particularly infections. Here’s a detailed overview of its anatomy, divisions, clinical significance, and potential complications.
Anatomy
- Shape and Location: The lateral pharyngeal space is a
potential cone-shaped space or cleft.
- Base: The base of the cone is located at the base of the skull.
- Apex: The apex extends down to the greater horn of the hyoid bone.
- Divisions: The space is divided into two compartments
by the styloid process:
- Anterior Compartment: Located in front of the styloid process.
- Posterior Compartment: Located behind the styloid process.
Boundaries
- Medial Boundary: The lateral wall of the pharynx.
- Lateral Boundary: The medial surface of the mandible and the muscles of the neck.
- Superior Boundary: The base of the skull.
- Inferior Boundary: The greater horn of the hyoid bone.
Contents
The lateral pharyngeal space contains various important structures, including:
- Muscles: The stylopharyngeus and the superior pharyngeal constrictor muscles.
- Nerves: The glossopharyngeal nerve (CN IX) and the vagus nerve (CN X) may be present in this space.
- Vessels: The internal carotid artery and the internal jugular vein are closely associated with this space, particularly within the carotid sheath.
Clinical Significance
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Infection Risk: Infection in the lateral pharyngeal space can be extremely serious due to its proximity to vital structures, particularly the carotid sheath, which contains the internal carotid artery, internal jugular vein, and cranial nerves.
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Potential Complications:
- Spread of Infection: Infections can spread from the lateral pharyngeal space to other areas, including the mediastinum, leading to life-threatening conditions such as mediastinitis.
- Airway Compromise: Swelling or abscess formation in this space can lead to airway obstruction, necessitating urgent medical intervention.
- Vascular Complications: The close relationship with the carotid sheath means that infections can potentially involve the carotid artery or jugular vein, leading to complications such as thrombosis or carotid artery rupture.
Diagnosis and Management
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Diagnosis:
- Clinical examination may reveal signs of infection, such as fever, neck swelling, and difficulty swallowing.
- Imaging studies, such as CT scans, are often used to assess the extent of infection and involvement of surrounding structures.
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Management:
- Antibiotics: Broad-spectrum intravenous antibiotics are typically initiated to manage the infection.
- Surgical Intervention: In cases of abscess formation or significant swelling, surgical drainage may be necessary to relieve pressure and remove infected material.