Posterior Mandibular Dislocation: Causes, Symptoms, Treatment, and Recovery

What is posterior dislocation of mandible?

Posterior dislocation of the mandible, while far less common than its anterior counterpart, is a serious and painful injury involving the backward displacement of the jawbone (mandible) from its normal articulation within the temporomandibular joint (TMJ).

Understanding the Temporomandibular Joint (TMJ)

To grasp a mandibular dislocation, it's essential to understand the TMJ. This complex joint connects the mandible (lower jawbone) to the temporal bone of the skull. It's a bilateral joint, meaning there's one on each side of the head, working in tandem to facilitate jaw movements like chewing, speaking, and yawning.

• Components of the TMJ:
  • Mandibular Condyle: The rounded upper end of the mandible that articulates with the skull.
  • Mandibular Fossa (Gelnoid Fossa): A depression in the temporal bone where the condyle rests.
  • Articular Eminence: A bony protrusion anterior to the mandibular fossa, which typically prevents posterior displacement during normal movement.
  • Articular Disc (Meniscus): A small, oval-shaped piece of cartilage located between the condyle and the fossa, acting as a shock absorber and ensuring smooth movement.
  • Ligaments and Muscles: A network of strong ligaments (e.g., temporomandibular ligament) and powerful muscles (e.g., masseter, temporalis, pterygoids) that stabilize the joint and control jaw movement.

In a healthy TMJ, the condyle sits securely within the mandibular fossa, held in place by surrounding ligaments and muscles.

What is Posterior Dislocation?

Posterior dislocation of the mandible occurs when the mandibular condyle is forced backward out of the mandibular fossa. Unlike anterior dislocations, where the condyle moves forward over the articular eminence, posterior dislocations are rare due to the inherent anatomical barriers and strong ligaments that resist backward movement. They typically require significant force and can be associated with more severe trauma and potential complications.

Causes of Posterior Mandibular Dislocation

Given the strong anatomical resistance to posterior movement, this type of dislocation is almost exclusively caused by high-impact trauma.

• Direct Blow to the Chin: The most common cause is a direct, forceful impact to the chin, especially when the mouth is closed or slightly open. This force drives the mandibular condyle posteriorly.
• Motor Vehicle Accidents: Whiplash injuries or direct facial impact during car accidents can generate sufficient force.
• Falls: Falls onto the chin or face can lead to posterior displacement.
• Sports Injuries: High-impact sports, particularly those involving contact or falls (e.g., rugby, martial arts, cycling accidents), can result in such injuries.
• Assaults: Direct blows to the jaw during an assault.

Signs and Symptoms

A posterior mandibular dislocation is an acute and painful injury, presenting with distinct signs:

• Severe Pain: Intense pain in the jaw, often localized to the ear region or the joint itself.
• Inability to Close the Mouth: The jaw may be locked in a slightly open or abnormal position, making it impossible to fully close the mouth or bring the teeth together.
• Malocclusion: The upper and lower teeth will not align correctly due to the displaced jaw.
• Swelling and Bruising: Rapid onset of swelling and potentially bruising around the joint and lower jaw.
• Difficulty Speaking and Swallowing: Due to pain and the inability to properly move the jaw.
• Palpable Deformity: In some cases, a clinician may be able to feel the displaced condyle behind its normal position.
• Ear Canal Involvement: Because of the proximity of the TMJ to the ear canal, posterior dislocation can sometimes cause bleeding from the ear or damage to the ear canal structures.

Diagnosis

Accurate diagnosis is crucial for proper treatment and to rule out associated injuries.

• Clinical Examination: A healthcare professional will take a detailed history of the injury and perform a physical examination of the jaw, assessing range of motion, pain, and any visible or palpable deformities.
• Imaging Studies:
  • X-rays: Standard X-rays (e.g., lateral oblique, panoramic, or open-mouth views) are typically the first imaging modality used to confirm the dislocation and assess for any accompanying fractures of the condyle or temporal bone.
  • Computed Tomography (CT) Scan: A CT scan provides more detailed cross-sectional images, which are invaluable for assessing the exact position of the condyle, the integrity of the articular disc, and especially for detecting subtle fractures or damage to surrounding soft tissues and structures like the ear canal.

Treatment and Management

Posterior mandibular dislocation is a medical emergency requiring prompt professional intervention.

• Immediate Medical Attention: It is critical to seek immediate medical care from an emergency room or an oral and maxillofacial surgeon.
• Manual Reduction: The primary treatment involves manually repositioning the displaced condyle back into the mandibular fossa. This procedure is performed by a trained healthcare professional (e.g., emergency physician, oral surgeon, ENT specialist) and often requires:
  • Pain Management: Administering analgesics and sometimes muscle relaxants or conscious sedation to alleviate pain and relax the jaw muscles, making reduction easier.
  • Specific Maneuvers: The clinician will use specific techniques to manipulate the jaw, guiding the condyle back into place.
• Post-Reduction Care:
  • Jaw Rest: Limiting jaw movement is crucial for initial healing. This typically involves a soft diet for several days to weeks.
  • Immobilization (Rarely): Unlike anterior dislocations, posterior dislocations rarely require prolonged immobilization, but a soft bandage or jaw support might be used for comfort and to remind the patient to limit movement.
  • Pain and Inflammation Management: Over-the-counter or prescription pain relievers and anti-inflammatory medications may be prescribed.
  • Follow-up: Regular follow-up appointments are necessary to monitor healing and assess for any long-term complications.

Potential Complications

Due to the force involved and the proximity of vital structures, posterior mandibular dislocation can lead to several complications:

• Fractures: The high impact can cause fractures of the mandibular condyle, neck, or temporal bone.
• Recurrent Dislocation: While less common than with anterior dislocations, repeated posterior dislocations can occur, particularly if underlying structural damage isn't addressed.
• TMJ Dysfunction: Chronic pain, clicking, popping, or limited jaw movement can develop due to damage to the articular disc or ligaments.
• Nerve Damage: The facial nerve (affecting facial muscle control) or the auriculotemporal nerve (affecting sensation around the ear and temple) can be injured.
• Ear Canal Damage: Direct trauma or compression can cause bleeding from the ear, damage to the external auditory canal, or even middle ear structures.
• Arthritis: Long-term TMJ dysfunction can sometimes lead to degenerative arthritis in the joint.

Recovery and Prevention

Recovery typically involves a period of rest, a soft diet, and gradual return to normal jaw function. Physical therapy may be recommended to restore full range of motion and strengthen surrounding muscles, especially if there's ongoing TMJ dysfunction.

Prevention primarily focuses on avoiding the high-impact traumas that cause these injuries:

• Protective Gear: Wearing appropriate mouthguards and headgear during contact sports.
• Seatbelt Use: Always using seatbelts in vehicles to minimize facial trauma during accidents.
• Fall Prevention: Taking precautions to prevent falls, especially for older adults or those with balance issues.

When to Seek Medical Attention

Any suspected jaw dislocation, especially after a traumatic event, warrants immediate medical attention. Do not attempt to reduce a dislocated jaw yourself, as this can cause further damage. A healthcare professional can accurately diagnose the injury, rule out associated fractures, and perform the necessary reduction safely and effectively.