NEET MDS Lessons
Oral and Maxillofacial Surgery
Surgical Gut (Catgut)
Surgical gut, commonly known as catgut, is a type of absorbable suture material derived from the intestines of animals, primarily sheep and cattle. It has been widely used in surgical procedures due to its unique properties, although it has certain limitations. Below is a detailed overview of surgical gut, including its composition, properties, mechanisms of absorption, and clinical applications.
Composition and Preparation
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Source: Surgical gut is prepared from:
- Submucosa of Sheep Small Intestine: This layer is rich in collagen, which is essential for the strength and absorbability of the suture.
- Serosal Layer of Cattle Small Intestine: This layer also provides collagen and is used in the production of surgical gut.
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Collagen Content: The primary component of surgical gut is collagen, which is treated with formaldehyde to enhance its properties. This treatment helps stabilize the collagen structure and prolongs the suture's strength.
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Suture Characteristics:
- Multifilament Structure: Surgical gut is a capillary multifilament suture, meaning it consists of multiple strands that can absorb fluids, which can be beneficial in certain surgical contexts.
- Smooth Surface: The sutures are machine-ground and polished to yield a relatively smooth surface, resembling that of monofilament sutures.
Sterilization
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Sterilization Methods:
- Ionizing Radiation: Surgical gut is typically sterilized using ionizing radiation, which effectively kills pathogens without denaturing the protein structure of the collagen.
- Ethylene Oxide: This method can also be used for sterilization, and it prolongs the absorption time of the suture, making it suitable for specific applications.
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Limitations of Autoclaving: Autoclaving is not suitable for surgical gut because it denatures the protein, leading to a significant loss of tensile strength.
Mechanism of Absorption
The absorption of surgical gut after implantation occurs through a twofold mechanism primarily involving macrophages:
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Molecular Bond Cleavage:
- Acid hydrolytic and collagenolytic activities cleave the molecular bonds in the collagen structure of the suture.
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Digestion and Absorption:
- Proteolytic enzymes further digest the collagen, leading to the gradual absorption of the suture material.
- Foreign Body Reaction: Due to its collagenous composition, surgical gut stimulates a significant foreign body reaction in the implanted tissue, which can lead to inflammation.
Rate of Absorption and Loss of Tensile Strength
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Variability: The rate of absorption and loss of tensile strength varies depending on the implantation site and the surrounding tissue environment.
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Premature Absorption: Factors that can lead to premature absorption include:
- Exposure to gastric secretions.
- Presence of infection.
- Highly vascularized tissues.
- Conditions in protein-depleted patients.
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Strength Loss Timeline:
- Medium chromic gut loses about 33% of its original strength after 7 days of implantation and about 67% after 28 days.
Types of Surgical Gut
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Plain Gut:
- Characteristics: Produces a severe tissue reaction and loses tensile strength rapidly, making it less useful in surgical applications.
- Applications: Limited due to its inflammatory response and quick absorption.
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Chromic Gut:
- Treatment: Treated with chromium salts to increase tensile strength and resistance to digestion while decreasing tissue reactivity.
- Advantages: Provides a more controlled absorption rate and is more suitable for surgical use compared to plain gut.
Handling Characteristics
- Good Handling: Surgical gut generally exhibits good handling characteristics, allowing for easy manipulation during surgical procedures.
- Weakness When Wet: It swells and weakens when wet, which can affect knot security and overall performance during surgery.
Disadvantages
- Intense Inflammatory Reaction: Surgical gut can provoke a significant inflammatory response, which may complicate healing.
- Variability in Strength Loss: The unpredictable rate of loss of tensile strength can be a concern in surgical applications.
- Capillarity: The multifilament structure can absorb fluids, which may lead to increased tissue reaction and complications.
- Sensitivity Reactions: Some patients, particularly cats, may experience sensitivity reactions to surgical gut.
Clinical Applications
- Use in Surgery: Surgical gut is used in various surgical procedures, particularly in soft tissue closures where absorbable sutures are preferred.
- Adhesion Formation: The use of surgical gut is generally unwarranted in situations where adhesion formation is desired due to its inflammatory properties.
Most Frequent Intra – orbital Fracture
Location: Orbital floor medial to infraorbital canal Pattern:
- Confined to medial portion of floor
- Lower portion of medial orbital wall Consequence:
- Orbital soft tissue displacement into maxillary/ethmoidal sinuses
- Increased orbital volume
Diplopia Types
Binocular Diplopia
- More common in trauma
- Causes: Proptosis, enophthalmos (globe position alteration)
Monocular Diplopia
- Retinal detachment
- Dislocated lens
- Foreign body
- Uncorrected refractive error
- Cataract
- Corneal opacity
Superior Orbital Fissure Syndrome
- Mechanism: Compression of superior orbital fissure contents
Orbital Apex Syndrome
- Cause: Usually retrobulbar hematoma
- Mechanism: Compression of optic canal + superior orbital fissure contents
NOE FRACTURES
Bowstring Test
- Purpose: Assess medial canthal ligament status
- Technique: Lateral traction on lateral canthus while palpating medial canthal region
- Positive test: Confirms telecanthus
Subciliary Incision
- Major complication: Greatest propensity for ectropion or scleral show
Marsupialization
Marsupialization, also known as decompression, is a surgical procedure used primarily to treat cystic lesions, particularly odontogenic cysts, by creating a surgical window in the wall of the cyst. This technique aims to reduce intracystic pressure, promote the shrinkage of the cyst, and encourage bone fill in the surrounding area.
Key Features of Marsupialization
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Indication:
- Marsupialization is indicated for large cystic lesions that are not
amenable to complete excision due to their size, location, or proximity
to vital structures. It is commonly used for:
- Odontogenic keratocysts
- Dentigerous cysts
- Radicular cysts
- Other large cystic lesions in the jaw
- Marsupialization is indicated for large cystic lesions that are not
amenable to complete excision due to their size, location, or proximity
to vital structures. It is commonly used for:
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Surgical Technique:
- Creation of a Surgical Window:
- The procedure begins with the creation of a window in the wall of the cyst. This is typically done through an intraoral approach, where an incision is made in the mucosa overlying the cyst.
- Evacuation of Cystic Content:
- The cystic contents are evacuated, which helps to decrease the intracystic pressure. This reduction in pressure is crucial for promoting the shrinkage of the cyst and facilitating bone fill.
- Suturing the Cystic Lining:
- The remaining cystic lining is sutured to the edge of the oral mucosa. This can be done using continuous sutures or interrupted sutures, depending on the surgeon's preference and the specific clinical situation.
- Creation of a Surgical Window:
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Benefits:
- Pressure Reduction: By decreasing the intracystic pressure, marsupialization can lead to the gradual reduction in the size of the cyst.
- Bone Regeneration: The procedure promotes bone fill in the area previously occupied by the cyst, which can help restore normal anatomy and function.
- Minimally Invasive: Compared to complete cyst excision, marsupialization is less invasive and can be performed with less morbidity.
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Postoperative Care:
- Patients may experience some discomfort and swelling following the procedure, which can be managed with analgesics.
- Regular follow-up appointments are necessary to monitor the healing process and assess the reduction in cyst size.
- Oral hygiene is crucial to prevent infection at the surgical site.
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Outcomes:
- Marsupialization can be an effective treatment for large cystic lesions, leading to significant reduction in size and promoting bone regeneration. In some cases, if the cyst does not resolve completely, further treatment options, including complete excision, may be considered.
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.
Sjögren's Syndrome and Sialography
Sjögren's syndrome is an autoimmune disorder characterized by the destruction of exocrine glands, particularly the salivary and lacrimal glands, leading to dry mouth (xerostomia) and dry eyes (keratoconjunctivitis sicca). One of the diagnostic tools used to evaluate the salivary glands in patients with Sjögren's syndrome is sialography.
Sialography Findings in Sjögren's Syndrome
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Sialectasis: In sialography, Sjögren's syndrome is often associated with sialectasis, which refers to the dilation of the salivary gland ducts. This occurs due to the inflammatory changes and damage to the ductal system.
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"Cherry Blossom" Appearance: The sialographic findings in Sjögren's syndrome can produce a characteristic appearance described as:
- "Cherry Blossom" or "Branchless Fruit Laden Tree": This appearance is due to the presence of many large dye-filled spaces within the salivary glands. The pattern resembles the branches of a tree laden with fruit, where the dye fills the dilated ducts and spaces, creating a striking visual effect.
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Mechanism: The appearance is thought to result from the dye passing through weakened or damaged salivary gland ducts, which are unable to properly transport saliva due to the underlying pathology of the syndrome. The inflammation and fibrosis associated with Sjögren's syndrome lead to ductal obstruction and dilation.
Clinical Significance
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Diagnosis: The characteristic sialographic appearance can aid in the diagnosis of Sjögren's syndrome, especially when combined with clinical findings and other diagnostic tests (e.g., labial salivary gland biopsy).
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Management: Understanding the changes in the salivary glands can help guide management strategies for patients, including the use of saliva substitutes, medications to stimulate saliva production, and regular dental care to prevent complications associated with dry mouth.
- Gow – Gates landmarks:
- Corner of mouth
- Disto – palatal cusp of maxillary 2nd molar
- Neck of condyle
- Extraoral: Lower border of tragus
- Laryngeal mask airway (LMA): Supraglottic device
- Tracheostomy incision: 4–5 cm below cricoid cartilage
- Common tracheostomy complications:
- Peri – op: Anterior jugular vein injury
- Late: Innominate artery fistula
Submasseteric Space Infection
Submasseteric space infection refers to an infection that occurs in the submasseteric space, which is located beneath the masseter muscle. This space is clinically significant in the context of dental infections, particularly those arising from the lower third molars (wisdom teeth) or other odontogenic sources. Understanding the anatomy and potential spread of infections in this area is crucial for effective diagnosis and management.
Anatomy of the Submasseteric Space
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Location:
- The submasseteric space is situated beneath the masseter muscle, which is a major muscle involved in mastication (chewing).
- This space is bordered superiorly by the masseter muscle and inferiorly by the lower border of the ramus of the mandible.
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Boundaries:
- Inferior Boundary: The extension of an abscess or infection inferiorly is limited by the firm attachment of the masseter muscle to the lower border of the ramus of the mandible. This attachment creates a barrier that can restrict the spread of infection downward.
- Anterior Boundary: The forward spread of infection beyond the anterior border of the ramus is restricted by the anterior tail of the tendon of the temporalis muscle, which inserts into the anterior border of the ramus. This anatomical feature helps to contain infections within the submasseteric space.
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Posterior Boundary: The posterior limit of the submasseteric space is generally defined by the posterior border of the ramus of the mandible.
Clinical Implications
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Sources of Infection:
- Infections in the submasseteric space often arise from odontogenic
sources, such as:
- Pericoronitis associated with impacted lower third molars.
- Dental abscesses from other teeth in the mandible.
- Periodontal infections.
- Infections in the submasseteric space often arise from odontogenic
sources, such as:
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Symptoms:
- Patients with submasseteric space infections may present with:
- Swelling and tenderness in the area of the masseter muscle.
- Limited mouth opening (trismus) due to muscle spasm or swelling.
- Pain that may radiate to the ear or temporomandibular joint (TMJ).
- Fever and systemic signs of infection in more severe cases.
- Patients with submasseteric space infections may present with:
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Diagnosis:
- Diagnosis is typically made through clinical examination and imaging studies, such as panoramic radiographs or CT scans, to assess the extent of the infection and its relationship to surrounding structures.
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Management:
- Treatment of submasseteric space infections usually involves:
- Antibiotic Therapy: Broad-spectrum antibiotics are often initiated to control the infection.
- Surgical Intervention: Drainage of the abscess may be necessary, especially if there is significant swelling or if the patient is not responding to conservative management. Incision and drainage can be performed intraorally or extraorally, depending on the extent of the infection.
- Management of the Source: Addressing the underlying dental issue, such as extraction of an impacted tooth or treatment of a dental abscess, is essential to prevent recurrence.
- Treatment of submasseteric space infections usually involves: