Temporomandibular joint imaging

TMJ Imaging

1. Temporomandibular Joint Imaging

2. Introduction to TMJ Imaging Modalities of TMJ Imaging of osseous structures Imaging of soft tissues Abnormal Findings in TMJ References Contents

3. TMJ is a ginglymo-diarthroidal joint that is freely mobile with superior and inferior joint spaces separated by articular disc. “ Ginglymus ” meaning a hinge joint, allowing motion only backward and forward in one plane, and “ A rthrodia ” meaning a joint of which permits a gliding motion of the surfaces Introduction

4. Components of TMJ Glenoid Fossa & Articular Eminence/Protuberance Mandibular Condyle Articular Disk & Capsule Synovial Fluid Discal Ligaments Posterior Attachment or Retrodiscal Tissue or Bilaminar Zone Ligaments associated with TMJ Muscles of Mastication Arterial Supply, Venous Drainage & Sensory Innervation of TMJ

5. Diagnostic Imaging Of TMJ The type of imaging technique depends upon the clinical problems associated, so either imaging of hard tissue (OSSEOUS ) or soft tissue is desired. Certain protocols are to be taken care before the imaging procedure: T he amount of diagnostic information available from particular imaging modality. The cost of examination The radiation dose

6. TMJ Imaging Osseous Structure Soft tissue structure Plain film radiography Panoramic Radiograph Arthrography MRI USG CT CBCT

7. IMAGING OF OSSEOUS STRUCTURES Panoramic Radiograph Plain Film Radiograph: Transcranial Projections Transpharyngeal Projections Transorbital Projections Submentovertex Projections Conventional Tomography Computed Tomography (CT)

8. Panoramic Projections

9. Panoramic machines have specific TMJ programs which are of limited usefulness. Thick image layers Oblique view/distorted view of the joints Low image quality However this imaging modality gives a gross osseous change of condyle such as:- Asymmetries Extensive erosions Large osteophytes Tumors Fractures

10. However panoramic projections doesn’t provide informations about condylar positions or function. Mild osseous changes may be obscured, and only marked changes in articular eminence morphology can be seen as a result of super imposition by the skull base and zygomatic arch. For these reasons, the panoramic view should not be considered as a sole in imaging modality and be supplemented .

11. Plain Film Imaging Modalities The plain film usually consists of combinations of following projections and allows visualization in various planes:- Transcranial Projections Transpharyngeal Projections Transorbital Projections Submentovertex Projections

12. Transcranial View It is a view that aids in visualizing the sagittal view of the lateral aspects of condyle and temporal component. It is taken in both open and close mouth positions. Indication Area of joint seen TMJ pain dysfunction syndrome Lateral aspect of Glenoid fossa Internal derangement Articular eminence Range of movement in joints Joint space Condylar head

13. Film position: flat against patients ear Centered over TM joint of interest Against facial skin parallel to sagittal plane Position of patient: H ead adjusted so sagittal plane is vertical & ala tragus line parallel to floor

14. Central Ray T he central ray is direct at an angle of 25 (+ ve angulation) from the opposite side, through the cranium and above the petrous ridge of the temporal bone. The horizontal angulation can be individually corrected for the condylar long axis, or an average 20 anterior angle may be used.

15. Closed view- size of joint space, position of head of condyle, shape & condition of glenoid fossa & articular eminence Open view- range & type of movement Comparison of both sides Disadvantages : Superimposition of ipsi -lateral petrous ridge over the condylar neck

16. Transcranial projections of the left TMJ. Degree of translatory movement between the closed view (A) and the open view(B) (A) (B)

17. Transpharyngeal View (Parma projection, Macqueen-Dell Technique) This technique provides a sagittal view of the medial pole of the condyle. It is taken in open mouth position. Indication Area of joint seen TMJ pain dysfunction syndrome Lateral view: Condylar head & neck Osteoarthritis & rheumatoid arthritis Articular surface Condylar head- Cyst or tumor Fracture of neck & condyle

18. Film placement - P atient holds the cassette flat against patients ear Centered over TM joint of interest Against facial skin parallel to sagittal plane ½ inch anterior to EAM Central ray- D irected from opp side cranially at angle(-5 to -10 degrees) Beneath the zygomatic arch, through sigmoid notch posteriorly across pharynx at the condyle Comparison of both condylar heads

19. It is taken in the open or protruded position and depicts the entire medial lateral aspect of condyle in frontal plane. Transorbital Projections

20. Film position- Behind patients head at an angle of 45 degree to sagittal pane Position of patient- -Sagittal plane vertical - Canthomeatal line should be 10 degree to the horizontal with head tipped downwards Central ray- -tube head-front of patients face -directed to joint of interest at an angle of +20 degrees to strike cassette at right angles

21. Point of entry - Pupil of the same eye-asking patient to look straight ahead Medial canthus of the same eye Disadvantage : I f the patient cannot open wide, areas of the joint articulating surfaces will be obscured because of superimposition

22. Condyle seen below articular eminence

23. Submentovertex Projections A submentovertex projections provides a view of skull base and condyles in a horizontal plane. It is often used to determine the angulations of the long axis of the condylar head so for corrected tomography. Indication Evaluating facial asymmetries Condylar displacement

24. Conventional Tomography Tomography is a radiographic technique that produces multiple thin image slices, permitting visualization of an anatomic structure essentially free of superimpositions of overlapping structures. Tomographs typically are exposed in the sagittal (lateral ) plane with several image slices in the closed (maximal intercuspation ) position and usually only one image in the maximal open position.

25. In "corrected“ sagittal tomography, the condylar long axis with respect to the midsagittal plane is determined using an SMV projection The patient's head is then rotated to this angle, permitting alignment of image slices perpendicular to the condylar long axis. This minimizes geometric distortion of the joint and allows accurate assessment of condylar position.

26. Computed Tomography (CT ) I ndicated when more information is needed about the three-dimensional shape and internal structure of the osseous components of the joint or if information regarding the surrounding soft tissues is required. Multiple image slices are made in both the axial and coronal planes, although the coronal images are the more useful. Three dimensional reformatted images also can be produced .

27. These are useful for assessing osseous deformities of the jaws or surrounding structures. CT cannot produce accurate images of the articular disk . CT may be considered for determining the presence and extent of ankylosis and neoplasms and the extent of bone involvement

28. Indications: Extent of ankylosis N eoplasms-bone involvement Complex fractures Complications - polytetrafluoroethylene or silicon sheet implants -erosions into the middle cranial fossa Heterotopic bone growth

29. CBCT is the recent technology developed for angiography in 1982 and subsequently applied to maxillofacial imaging. CBCT has the advantage of reduced patient overdose compared to medial CT and is likely to replace Conventional Tomography. In CBCT the patient is scanned in closed position and low resolution scan done in open or other positions . CBCT

30. Soft tissue imaging is indicated when the TMJ pain and dysfunction are present and when clinical findings suggest disk displacement along with symptoms that are unresponsive to conservative therapy. Imaging should be prescribed only when the anticipated results are expected to influence the treatment plan. The imaging modalities for soft tissues are: Arthrography Magnetic Resonance Imaging (MRI)

31. Arthrography Norgaard (1940) It is a technique in which an indirect image of the disk is obtained by injecting a radiopaque contrast agent into the joint spaces under fluoroscopic guidance. However MRI has replaced Arthrography in todays context and is now the imaging technique of choice for soft tissues.

32. Indications: Position and function of disk -pain and dysfunction- long standing History of locking-persistent Perforations of the disk and retrodiskal tissue. Joint dynamics Disc displacement-ant/ anteromedial Contraindications: Infections in the preauricular region. Patients allergic to contrast media. Patients with bleeding disorders and on anticoagulant therapy

33. Contrast Media Arthroscopes Arthroscopic sheath Arthroscopic biopsy

34. Vascular injury Extravasation of irrigation fluid into the surrounding tissue Broken instruments in the joint Intracranial damage Infection Nerve injury Complications

35. Magnetic Resonance Imaging (MRI)

36. Uses Magnetic field and radiofrequency pulses Bilateral dual surface coils- 0.5 to 2 tesla-Improve image resolution MRI produces excellent image qualities so is the principle imaging choice for soft tissue . Oblique sagittal/oblique coronal scans with t1, t2 Closed mouth, partially open and fully open positions

37. I mages in the sagittal and coronal planes without repositioning the patient T1-weighted images best –osseous & diskal tissues T2-weighted images- inflammation and joint effusion. Motion MRI studies-during opening and closing the patient open in a series of stepped distances and using rapid image acquisition. ("fast scan ")

38. Disk is of low signal intensity (dark grey or black) and can be distinguished from surrounding tissue that has high signal intensity. Posterior disk attachment (PDA) shows higher than the disk and the junction between the posterior band of the disk and PDA is distinct . Medial disk displacements-best seen

39. MRI of a normal TMJ. A. Closed view showing the condyle and temporal component. The biconcave disk is located with its posterior band (arrow) over the condyle . B. Coronal image showing the osseous components and disk (arrows) superior to the condyle. A. B.

40. This sagittal MR image shows anterior disk displacement in the closed mouth position. Disc is deformed

41. Advantages of CT Direct delineation of bony structures-surgical anatomy Some soft tissues-lateral pterygoid muscle 3-D images from any angle Disadvantages- -high radiation exposure -soft tissues cant be appreciated Advantages of MRI Soft tissues- esp disk and its association Information in short acquisition time Disadvatages - -expensive - claustophobia

42. Applied Aspect

43. Abnormal TMJ Findings Developmental Soft tissue related Remodeling & Arthritis Trauma Tumors

44. Thank You 