The Tempromandibular Joint (TMJ) By: Nour-Eldin A. Nour-Eldin Mohammed

Normal Anatomy Mandibular condyle (head) Glenoid fossa Articular tubercle (eminence)

Posterior band of articular disc Anterior band of articular disc Mandibular condyle (head) Lateral pterygoid muscle raphe Lower head of lateral pterygoid muscle Posterior disc attachment

Mandibular condyle (head) Articular disc

MRI and autopsy sections: upper row oblique sagittal MRI, asymptomatic volunteer: left lateral, middle medial, right opened mouth

Internal Derangements General orthopedic term implying a mechanical fault that interferes with the smooth action of a joint The most common internal derangement is disc displacement Clinical Features Clicking sounds from joint(s) Restricted or normal mouth opening capacity Deviation on opening Pain

Internal Derangements Imaging Features Anterior disc displacement: posterior band of the disc located anterior to the superior portion of the condyle at closed mouth on oblique sagittal images Disc may have normal (biconcave) or deformed morphology In opened mouth position disc may be in a normal position (“with reduction”) or continue to be displaced (“without reduction”)

Partial anterior disc displacement at baseline lateral sections central sections open-mouth

Complete anterior disc displacement medial section Autopsy Open-mouth MRI

Lateral disc displacement and normal bone

Medial disc displacement coronal MRI Oblique coronal MRI

Posterior disc displacement

Osteoarthritis Definition Non-inflammatory focal degenerative disorder of synovial joints, primarily affecting articular cartilage and sub-condylar bone; initiated by deterioration of articular soft-tissue cover and exposure of bone. Clinical Features Crepitation sounds from joint(s) Restricted or normal mouth opening capacity Pain or no pain from joint areas and/or of mastication muscles Occasionally, joints may show inflammatory signs Women more frequent than men

anteriorly displaced and deformed, degenerated disc and irregular cortical outline with osteophytosis and sclerosis of condyle .

Advanced osteoarthritis and anterior disc displacement, with joint effusion

Bone Marrow Abnormalities Definition Bone marrow edema: serum proteins within marrow interstitium surrounded by normal hematopoietic marrow. Osteonecrosis: complete loss of hematopoietic marrow.

Imaging Features Abnormal signal on T2-weighted image from condyle marrow: increased signal indicates marrow edema; reduced signal indicates marrow sclerosis or fibrosis Combination of marrow edema signal and marrow sclerosis signal in condyle most reliable sign for histologic diagnosis of osteonecrosis Marrow sclerosis signal may indicate advanced osteoarthritis without osteonecrosis, or osteonecrosis

Arthritides Definition Inflammation of synovial membrane characterized by edema, cellular accumulation, and synovial proliferation (villous formation). Clinical Features Swelling of joint area, not frequently seen in TMJ Pain (in active disease) from joints Restricted mouth opening capacity Morning stiffness, in particular stiff neck Dental occlusion problems; “my bite doesn’t fit” Crepitation due to secondary osteoarthritis

Rheumatoid arthritis. After 1 year

Rheumatoid arthritis. A MRI shows completely destroyed disc, replaced by fibrous or vascular pannus and cortical punched-out erosion (arrow) with sclerosis in condyle.

Psoriatic arthropathy Psoriatic arthropathy. Oblique coronal and oblique sagittal CT images show punched-out erosion in lateral part of condyle (arrow). Psoriatic arthropathy. MRI shows contrast enhancement within bone erosion and in joint space, consistent with thickened synovium/pannus formation. Openmouth MRI shows reduced condylar translation but normally located disc (and normal bone in this section)

Inflammatory arthritis

Ankyloses Definition Fibrous or bony union between joint components.

Growth Disturbances (Anomalies) Definition Abnormal growth of mandibular condyle; overgrowth, undergrowth, or bifid appearance.

Condylar hypoplasia and facial asymmetry Normal TMJ

Bifid condyle.

Inflammatory or Tumor-like Conditions Calcium Pyrophosphate Dehydrate Crystal Deposition Disease (Pseudogout)

Benign Tumors Synovial Chondromatosis Benign tumor characterized by cartilaginous metaplasia of synovial membrane, usually in knee, producing small nodules of cartilage, which essentially separate from membrane to become loose bodies that may ossify.

Synovial Chondromatosis

Osteochondroma Definition Benign tumor characterized by normal bone and cartilage, near growth zones.

Osteoma

Osteosarcoma mandible; 18-yearold female Malignant Tumors Osteosarcoma mandible; 18-yearold female

Malignant tumor, mandible; 70- year-old male with metastasis from lung cancer

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