NEET MDS Lessons
Oral and Maxillofacial Surgery
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.
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.
| Method | Details |
|---|---|
| Hot air oven | 160°C – 2 hrs; 120°C – 6 hrs |
| Boiling water | 100°C – 10 mins; spores may survive |
| Sodium carbonate (2%) | Elevates boiling point |
| Autoclaving | 250°F, 15 lb, 20 – 30 mins |
| Antiseptic | Applied to skin/mucosa |
| Disinfectant | Used on non – vital surfaces |
Sutures
Sutures are an essential component of oral surgery, used to close wounds, secure grafts, and stabilize tissues after surgical procedures. The choice of suture material and sterilization methods is critical for ensuring effective healing and minimizing complications. Below is a detailed overview of suture materials, specifically focusing on catgut and its sterilization methods.
Types of Suture Materials
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Absorbable Sutures: These sutures are designed to be broken down and absorbed by the body over time. They are commonly used in oral surgery for soft tissue closure where long-term support is not necessary.
- Catgut: A natural absorbable suture made from the intestinal mucosa of sheep or cattle. It is widely used in oral surgery due to its good handling properties and ability to promote healing.
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Non-Absorbable Sutures: These sutures remain in the body until they are removed or until they eventually break down. They are used in situations where long-term support is needed.
Catgut Sutures
Sterilization Methods: Catgut sutures must be properly sterilized to prevent infection and ensure safety during surgical procedures. Two common sterilization methods for catgut are:
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Gamma Radiation Sterilization:
- Process: Catgut sutures are sterilized using gamma radiation, typically at a dose of 2.5 mega-rads. This method effectively kills bacteria and other pathogens without compromising the integrity of the suture material.
- Preservation: After sterilization, catgut sutures are preserved in a solution of 2.5 percent formaldehyde and denatured absolute alcohol. This solution helps maintain the sterility of the sutures while preventing degradation.
- Packaging: The sutures are stored in spools or foils to protect them from contamination until they are ready for use.
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Chromic Acid Method:
- Process: In this method, catgut sutures are immersed in a solution containing 20 percent chromic acid and five parts of 8.5 percent glycerin. This process not only sterilizes the sutures but also enhances their durability.
- Benefits: The chromic acid treatment helps to secure a longer stay in the pack, meaning that the sutures can maintain their strength and integrity for a more extended period before being used. This is particularly beneficial in surgical settings where sutures may need to be stored for some time.
Characteristics of Catgut Sutures
- Absorbability: Catgut sutures are absorbable, typically losing their tensile strength within 7 to 14 days, depending on the type (plain or chromic).
- Tensile Strength: They provide good initial tensile strength, making them suitable for various surgical applications.
- Biocompatibility: Being a natural product, catgut is generally well-tolerated by the body, although some patients may have sensitivities or allergic reactions.
- Handling: Catgut sutures are easy to handle and tie, making them a popular choice among surgeons.
Applications in Oral Surgery
- Soft Tissue Closure: Catgut sutures are commonly used for closing incisions in soft tissues of the oral cavity, such as after tooth extractions, periodontal surgeries, and mucosal repairs.
- Graft Stabilization: They can also be used to secure grafts in procedures like guided bone regeneration or soft tissue grafting.
- NEO trauma: ↑ intercanthal distance
- Frontal bar fracture: ↑ interpupillary distance
- EDCP plate: For cases without tension band; provides compression
- Outer oblique hole: Rotational movement → superior border compression
- More difficult to apply than standard plates
| Peeling Type | Agent |
|---|---|
| Superficial | Trichloroacetic acid, Alpha hydroxy acids |
| Medium | Phenol |
| Deep | Baker – Gordon formula (Croton oil) |
- Subdural hemorrhage: Due to cortical vessel disruption or brain laceration.
- Hypertensive intracranial bleed: Most common site is putamen.
- Skin graft survival (48 hrs): Via plasma imbibition.
- Necrotizing fasciitis: Rapid bacterial infection sparing muscle.
- Psammoma bodies: Seen in papillary carcinoma.
- Follicular carcinoma treatment: Hemithyroidectomy.
- Nitroglycerin sublingual route: Ensures fast absorption & action.
- LeFort I osteotomy blood supply: Maintained by ascending pharyngeal artery.
- Sequestrum in osteomyelitis: Appears more radiopaque.