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By:Nour-Eldin A. Nour-Eldin Mohammed
Normal Anatomy
Mandibular condyle (head)
Glenoid fossa
Articular tubercle (eminence)
Lateral pterygoid muscle raphe
Lower head of lateral pterygoid muscle
Anterior band of articular disc
Mandibular condyle (head)
Posterior band of articular disc
Posterior disc attachment
Mandibular condyle (head)
Articular disc
MRI and autopsy sections: upper row oblique sagittal MRI, asymptomatic volunteer: left lateral, middle medial, rightopened 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
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”)
Internal Derangements
lateral sections central sections open-mouth
Partial anterior disc displacement at baseline
Complete anterior disc displacement
Open-mouth MRI
medial section Autopsy
Lateral disc displacement and normal bone
Medial disc displacement
Oblique coronal MRIcoronal MRI
Posterior disc displacement
OsteoarthritisDefinition 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 AbnormalitiesDefinition 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 fromcondyle 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 advancedosteoarthritis without osteonecrosis, or osteonecrosis
ArthritidesDefinition 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. Oblique coronal and oblique sagittal CT images show punched-out erosion in lateral part of condyle (arrow).
Psoriatic arthropathy. MRI shows contrast enhancementwithin bone erosion and in joint space, consistent with thickened synovium/pannus formation. OpenmouthMRI shows reduced condylar translation but normallylocated disc (and normal bone in this section)
Inflammatory arthritis
AnkylosesDefinitionFibrous or bony union between joint components.
Growth Disturbances (Anomalies)Definition
Abnormal growth of mandibular condyle; overgrowth, undergrowth, or bifid appearance.
Normal TMJ
Condylar Hypoplasia
Condylar hypoplasia and facial asymmetry
Bifid condyle.
Inflammatory or Tumor-like ConditionsCalcium Pyrophosphate
Dehydrate CrystalDeposition Disease (Pseudogout)
Benign TumorsSynovial 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
OsteochondromaDefinitionBenign tumor characterized by normal bone and cartilage, near growth zones.
Osteoma
Malignant Tumors
Osteosarcoma mandible; 18-yearold female
Malignant tumor, mandible; 70- year-old male with metastasis from lung cancer
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