TMJ Ankylosis

Temporomandibular Joint (TMJ) ankylosis is a condition characterized by the abnormal fusion of the mandibular condyle to the temporal bone, leading to restricted jaw movement. This condition can significantly impact a patient's ability to open their mouth and perform normal functions such as eating and speaking.

Causes and Mechanisms of TMJ Ankylosis

1. Condylar Injuries:

   • Most cases of TMJ ankylosis result from condylar injuries sustained before the age of 10. The unique anatomy and physiology of the condyle in children contribute to the development of ankylosis.

2. Unique Pattern of Condylar Fractures in Children:

   • In children, the condylar cortical bone is thinner, and the condylar neck is broader. This anatomical configuration, combined with a rich subarticular vascular plexus, predisposes children to specific types of fractures.
   • Intracapsular Fractures: These fractures can lead to comminution (fragmentation) and hemarthrosis (bleeding into the joint) of the condylar head. A specific type of intracapsular fracture known as a "mushroom fracture" occurs, characterized by the comminution of the condylar head.

3. Formation of Fibrous Mass:

   • The presence of a highly osteogenic environment (one that promotes bone formation) following a fracture can lead to the organization of a fibrous mass. This mass can undergo ossification (the process of bone formation) and consolidation, ultimately resulting in ankylosis.

4. Trauma from Forceps Delivery:

   • TMJ ankylosis can also occur due to trauma sustained during forceps delivery, which may cause injury to the condylar region.

Etiology and Risk Factors

Laskin (1978) outlined several factors that may contribute to the etiology of TMJ ankylosis following trauma:

1. Age of Patient:

   • Younger patients have a significantly higher osteogenic potential and a more rapid healing response. The articular capsule in younger individuals is not as well developed, allowing for easier displacement of the condyle out of the fossa, which can damage the articular disk. Additionally, children may exhibit a greater tendency for prolonged self-imposed immobilization of the mandible after trauma.

2. Type of Fracture:

   • The condyle in children has a thinner cortex and a thicker neck, which predisposes them to a higher proportion of intracapsular comminuted fractures. In contrast, adults typically have a thinner condylar neck, which usually fractures at the neck, sparing the head of the condyle within the capsule.

3. Damage to the Articular Disk:

   • Direct contact between a comminuted condyle and the glenoid fossa, either due to a displaced or torn meniscus (articular disk), is a key factor in the development of ankylosis. This contact can lead to inflammation and subsequent bony fusion.

4. Period of Immobilization:

   • Prolonged mechanical immobilization or muscle splinting can promote orthogenesis (the formation of bone) and consolidation in an injured condyle. Total immobility between articular surfaces after a condylar injury can lead to a bony type of fusion, while some movement may result in a fibrous type of union.

Excision of Lesions Involving the Jaw Bone

When excising lesions involving the jaw bone, various terminologies are used to describe the specific techniques and outcomes of the procedures.

1. Enucleation

• Enucleation refers to the separation of a lesion from the bone while preserving bone continuity. This is achieved by removing the lesion along an apparent tissue or cleavage plane, which is often defined by an encapsulating or circumscribing connective tissue envelope derived from the lesion or surrounding bone.
• Key Characteristics:
  • The lesion is contained within a defined envelope.
  • Bone continuity is maintained post-excision.

2. Curettage

• Curettage involves the removal of a lesion from the bone by scraping, particularly when the lesion is friable or lacks an intact encapsulating tissue envelope. This technique may result in the removal of some surrounding bone.
• Key Characteristics:
  • Indicates the inability to separate the lesion along a distinct tissue plane.
  • May involve an inexact or immeasurable thickness of surrounding bone.
  • If a measurable margin of bone is removed, it is termed "resection without continuity defect."

3. Marsupialization

• Marsupialization is a surgical procedure that involves the exteriorization of a lesion by removing overlying tissue to expose its internal surface. This is done by excising a portion of the lesion bordering the oral cavity or another body cavity.
• Key Characteristics:
  • Multicompartmented lesions are rendered unicompartmental.
  • The lesion is clinically cystic, and the excised tissue may include bone and/or overlying mucosa.

4. Resection Without Continuity Defect

• This term describes the excision of a lesion along with a measurable perimeter of investing bone, without interrupting bone continuity. The anatomical relationship allows for the removal of the lesion while preserving the integrity of the bone.
• Key Characteristics:
  • Bone continuity is maintained.
  • Adjacent soft tissue may be included in the resection.

5. Resection With Continuity Defect

•  This involves the excision of a lesion that results in a defect in the continuity of the bone. This is often associated with more extensive resections.
• Key Characteristics:
  • Bone continuity is interrupted.
  • May require reconstruction or other interventions to restore function.

6. Disarticulation

•  Disarticulation is a special form of resection that involves the temporomandibular joint (TMJ) and results in a continuity defect.
• Key Characteristics:
  • Involves the removal of the joint and associated structures.
  • Results in loss of continuity in the jaw structure.

7. Recontouring

•  Recontouring refers to the surgical reduction of the size and/or shape of the surface of a bony lesion or bone part. The goal is to reshape the bone to conform to the adjacent normal bone surface or to achieve an aesthetic result.
• Key Characteristics:
  • May involve lesions such as bone hyperplasia, torus, or exostosis.
  • Can be performed with or without complete eradication of the lesion (e.g., fibrous dysplasia).

Types of Head Injury

1. Extradural Hematoma (EDH)

Overview

• Demographics: Most common in young male patients.
• Association: Always associated with skull fractures.
• Injured Vessel: Middle meningeal artery.
• Common Site of Injury: Temporal bone at the pterion (the thinnest part of the skull), which overlies the middle meningeal artery.
• Location of Hematoma: Between the bone and the dura mater.

Other Common Sites

1. Frontal fossa
2. Posterior fossa
3. May occur following disruption of major dural venous sinus.

Classical Presentation

• Initial Injury: Followed by a lucid interval where the patient may only complain of a headache.
• Deterioration: After minutes to hours, rapid deterioration occurs, leading to:
  • Contralateral hemiparesis
  • Reduced consciousness level
  • Ipsilateral pupillary dilatation (due to herniation)

Imaging

• CT Scan: Shows a lentiform (lens-shaped or biconvex) hyperdense lesion between the brain and skull.

Treatment

• Surgical Intervention: Immediate surgical evacuation via craniotomy.
• Mortality Rate: Overall mortality is 18% for all cases of EDH, but only 2% for isolated EDH.

2. Acute Subdural Hematoma (ASDH)

Overview

• Location: Accumulates in the space between the dura and arachnoid.
• Injury Mechanism: Associated with cortical vessel disruption and brain laceration.
• Primary Brain Injury: Often associated with primary brain injury.

Presentation

• Consciousness: Impaired consciousness from the time of impact.

Imaging

• CT Scan: Appears hyperdense, with hematoma spreading diffusely and having a concavo-convex appearance.

Treatment

• Surgical Intervention: Evacuation via craniotomy.
• Mortality Rate: Approximately 40%.

3. Chronic Subdural Hematoma (CSDH)

Overview

• Demographics: Most common in patients on anticoagulants and antiplatelet agents.
• History: Often follows a minor head injury weeks to months prior.
• Pathology: Due to the tear of bridging veins leading to ASDH, which is clinically silent. As the hematoma breaks down, it increases in volume, causing mass effect on the underlying brain.

Clinical Features

• Symptoms may include:
  • Headache
  • Cognitive decline
  • Focal neurological deficits (FND)
  • Seizures
• Important to exclude endocrine, hypoxic, and metabolic causes in this group.

Imaging

• CT Scan Appearance:
  • Acute blood (0–10 days): Hyperdense
  • Subacute blood (10 days to 2 weeks): Isodense
  • Chronic (> 2 weeks): Hypodense

Treatment

• Surgical Intervention: Bur hole evacuation rather than craniotomy.
• Anesthesia: Elderly patients can often undergo surgery under local anesthesia, despite comorbidities.

4. Subarachnoid Hemorrhage (SAH)

Overview

• Causes: Most commonly due to aneurysms for spontaneous SAH, but trauma is the most common cause overall.
• Management: Conservative treatment is often employed for trauma cases.

5. Cerebral Contusions

Overview

• Definition: Bruising of the brain tissue due to trauma.
• Mechanism: Often occurs at the site of impact (coup) and the opposite side (contrecoup).
• Symptoms: Can range from mild confusion to severe neurological deficits depending on the extent of the injury.

Imaging

• CT Scan: May show areas of low attenuation (hypodense) or high attenuation (hyperdense) depending on the age of the contusion.

Treatment

• Management: Depends on the severity and associated injuries; may require surgical intervention if there is significant mass effect.

Neuromuscular Blockers in Cardiac Anesthesia

In  patient on β-blockers, the choice of neuromuscular blockers (NMBs) is critical due to their potential cardiovascular effects. Here’s a detailed analysis of the implications of using fentanyl and various NMBs, particularly focusing on vecuronium and its effects.

Key Points on Fentanyl and β-Blockers

• Fentanyl:

  • Fentanyl is an opioid analgesic that can cause bradycardia due to its vagolytic activity. While it has minimal hemodynamic effects, the bradycardia it induces can be problematic, especially in patients already on β-blockers, which reduce heart rate and blood pressure.

• β-Blockers:

  • These medications reduce heart rate and blood pressure, which can compound the bradycardic effects of fentanyl. Therefore, careful consideration must be given to the choice of additional medications that may further depress cardiac function.

Vecuronium

• Effects:

  • Vecuronium is a non-depolarizing neuromuscular blocker that has minimal cardiovascular side effects when used alone. However, it can potentiate decreases in heart rate and cardiac index when administered after fentanyl.
  • The absence of positive chronotropic effects (unlike pancuronium) means that vecuronium does not counteract the bradycardia induced by fentanyl, leading to a higher risk of significant bradycardia and hypotension.

• Vagal Tone:

  • Vecuronium may enhance vagal tone, further predisposing patients to bradycardia. This is particularly concerning in patients on β-blockers, as the combination can lead to compounded cardiac depression.

Comparison with Other Neuromuscular Blockers

1. Pancuronium:

   • Vagolytic Action: Pancuronium has vagolytic properties that can help attenuate bradycardia and support blood pressure. It is often preferred in cardiac anesthesia for its more favorable hemodynamic profile compared to vecuronium.
   • Tachycardia: While it can induce tachycardia, this effect may be mitigated in patients on β-blockers, which can blunt the tachycardic response.

2. Atracurium:

   • Histamine Release: Atracurium can release histamine, leading to hemodynamic changes such as increased heart rate and decreased blood pressure. These effects can be minimized by slow administration of small doses.

3. Rocuronium:

   • Minimal Hemodynamic Effects: Rocuronium is generally associated with a lack of significant cardiovascular side effects, although occasional increases in heart rate have been noted.

4. Cis-Atracurium:

   • Cardiovascular Stability: Cis-atracurium does not have cardiovascular effects and does not release histamine, making it a safer option in terms of hemodynamic stability.

Inflammation is the respone of the body to an irritant.

Stages of Inflammation

1. General: Temperature Raised. In severe cases bacteremia or septicemia ,rigors may occur.

2. Local: classical signs of inflammation are due to hyperemia and inflammation exudate

i) Heat:  inflammed area feels warmer than the surrounding tissues.

ii) Redness

iii) Tenderness: Due to pressure of exudate on the surrounding nerves  If the exudate is  under tension, e.g. a furuncle (boil) of the ear, pain is severe.

iv) swelling

v) Loss of function.

The termination of Inflammation

This may be by:1. Resolution 2. Suppuration 3. Ulceration 4. Ganangren s. Fibrosis

Management

i. Increase the patients resistance., Rest,  Relief of pain by analgesics,  Diet: High protein and high calorie diet with vitamins,  Antibiotics,  Prevent further contamination of wound.

Surgical measures

1. Excision: If possible as in appendicectomy.

2. Incision and drainage: If an abscess forms.

Suture Materials

Sutures are essential in surgical procedures for wound closure and tissue approximation. Various types of sutures are available, each with unique properties, advantages, and applications. Below is a summary of some commonly used suture materials, including chromic catgut, polypropylene, polyglycolic acid, and polyamide (nylon).

1. Chromic Catgut

• Description:

  • Chromic catgut is a natural absorbable suture made from collagen derived from the submucosa of sheep intestines or the serosa of beef cattle intestines. It is over 99% pure collagen.

• Absorption Process:

  • The absorption of chromic catgut occurs through enzymatic digestion by proteolytic enzymes, which are derived from lysozymes contained within polymorphonuclear leukocytes (polymorphs) and macrophages.

• Absorption Rate:

  • The absorption rate depends on the size of the suture and whether it is plain or chromicized. Typically, absorption is completed within 60-120 days.

• Applications:

  • Commonly used in soft tissue approximation and ligation, particularly in areas where a temporary support is needed.

2. Polypropylene (Proline)

• Description:

  • Polypropylene is a synthetic monofilament suture made from a purified and dyed polymer.

• Properties:

  • It has an extremely high tensile strength, which it retains indefinitely after implantation. Polypropylene is non-biodegradable, meaning it does not break down in the body.

• Applications:

  • Ideal for use in situations where long-term support is required, such as in vascular surgery, hernia repairs, and other procedures where permanent sutures are beneficial.

3. Polyglycolic Acid

• Description:

  • Polyglycolic acid is a synthetic absorbable suture formed by linking glycolic acid monomers to create a polymer.

• Properties:

  • It is known for its predictable absorption rate and is commonly used in various surgical applications.

• Applications:

  • Frequently used in soft tissue approximation, including in gastrointestinal and gynecological surgeries, where absorbable sutures are preferred.

4. Polyamide (Nylon)

• Description:

  • Polyamide, commonly known as nylon, is a synthetic non-absorbable suture that is chemically extruded and generally available in monofilament form.

• Properties:

  • Nylon sutures have a low coefficient of friction, making passage through tissue easy. They also elicit minimal tissue reaction.

• Applications:

  • Used in a variety of surgical procedures, including skin closure, where a strong, durable suture is required.