TMJ surgical anatomy and applied aspects


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TMJ surgical anatomy and applied aspects

  2. 2. The most important functions of the temporomandibular joint (TMJ) are mastication and speech and are of great interest to dentists, oral surgeons, orthodontists, clinicians, and radiologists. The TMJ is a ginglymoarthrodial joint, a term that is derived from ginglymus, meaning a hinge joint, allowing motion only backward and forward in one plane, and arthrodia, meaning a joint of which permits a gliding motion of the surfaces.
  3. 3. The right and left TMJ form a bicondylar articulation and ellipsoid variety of the synovial joints similar to knee articulation. The common features of the synovial joints exhibited by this joint include a) Disk b) Bone c) Fibrous capsule d) Fluid e) Synovial membrane f) Ligaments.
  4. 4. However, the features that differentiate and make this joint unique are: Its articular surface covered by fibrocartilage instead of hyaline cartilage
  5. 5. Bilateral diarthrosis – right & left function together Articular surface covered by fibrocartilage instead of hyaline cartilage Only joint in human body to have a rigid endpoint of closure that of the teeth making occlusal contact.
  6. 6. In contrast to other diarthrodial joints TMJ is last joint to start develop, in about 7th week in utero. Develops from two distinct blastema
  7. 7. Mandibular condyle Articular surfaces of Temporal bone Capsule Articular disc Ligaments Muscular component
  8. 8. An ovoid process seated atop a narrow mandibular neck. It’s the articulating surface of the mandible. It is convex in all directions but wider latero-medially (15 to 20 mm) than antero-posteriorly (8 to 10mm).
  9. 9. The medial pole is directed more posteriorly. Thus, if the long axes of two condyles are extended medially, they meet at approximately the basion on the anterior limit of the foramen magnum, forming an angle that opens toward the front ranging from 145° to 160° It has a medial and lateral pole
  10. 10. The lateral pole of the condyle is rough, bluntly pointed, and projects only moderately from the plane of ramus, while the medial pole extends sharply inward from this plane. The articular surface lies on its anterosuperior aspect, thus facing the posterior slope of the articular eminence of the temporal bone.
  11. 11. The articular surface of the temporal bone is situated on the inferior aspect of temporal squama anterior to tympanic plate.
  12. 12. ARTICULA R EMINENCE • This is the entire transverse bony bar that forms the anterior root of zygoma. This articular surface is most heavily traveled by the condyle and disk as they ride forward and backward in normal jaw function. ARTICULA R TUBERCLE • This is a small, raised, rough, bony knob on the outer end of the articular eminence. • It projects below the level of the articular surface and serves to attach the lateral collateral ligament of the joint.
  13. 13. PREGLENOI D PLANE •This is the slightly hollowed, almost horizontal, articular surface continuing anteriorly from the height of the articular eminence
  14. 14. E: Articular eminence; enp: entogolenoid process; t:articular tubercle; lb: lateral border of the mandibular fossa; pep: preglenoid plane; Gf: glenoid fossa
  15. 15. The articular disc is the most important anatomic structure of the TMJ. It is a biconcave fibro cartilaginous structure located between the mandibular condyle and the temporal bone component of the joint. Its functions to accommodate a hinging action as well as the gliding actions between the temporal and mandibular articular bone
  16. 16. The articular disc is a roughly oval, firm, fibrous plate. 1. anterior band = 2 mm in thickness, 2. posterior band = 3 mm thick, 3. thin in the center intermediate band of 1 mm thickness. More posteriorly there is a bilaminar or retrodiscal region.
  17. 17. It is shaped like a peaked cap that divides the joint into a larger upper compartment and a smaller lower compartment.
  18. 18. Hinging movements take place in the lower compartment and gliding movements take place in the upper compartment. The superior surface of the disc - saddle-shaped to fit into the cranial contour, The inferior surface - concave to fit against the mandibular condyle.
  19. 19. The disc is attached all around the joint capsule except for the strong straps that fix the disc directly to the medial and lateral condylar poles, which ensure that the disc and condyle move together in protraction and retraction.
  20. 20. The anterior extension of the disc is attached to a fibrous capsule superiorly and inferiorly. In between it gives insertion to the lateral pterygoid muscle where the fibrous capsule is lacking and the synovial membrane is supported only by loose areolar tissue.
  21. 21. The anterior and posterior bands have predominantly transversal running fibers, while the thin intermediate zone has anteroposteriorly oriented fibers. Posteriorly, the bilaminar region consists of two layers of fibers separated by loose connective tissue.
  22. 22. The upper layer or temporal lamina is composed of elastin and is attached to the postglenoid process, medially extended ridge, which is the true posterior boundary of the joint. It prevents slipping of the disc while yawning. The inferior layer of the fibers or inferior lamina curve down behind the condyle to fuse with the capsule and back of the condylar neck at the lowest limit of the joint space. It prevents excessive rotation of the disc over the condyle.
  23. 23. In between the two layers, an expansile, soft pad of blood vessels and nerves are sandwiched and wrapped in elastic fibers that aid in contracting vessels and retracting disc in recoil of closing movements The volume of retrodiscal tissue must increase instantaneously when the condyle translates anteriorly.
  24. 24. Thin sleeve of tissue completely surrounding the joint. Extends from the circumference of the cranial articular surface to the neck of the mandible.
  25. 25. anterolaterally to the articular tubercle, laterally to the lateral rim of the mandibular fossa, posterolaterally to the postglenoid process, posteriorly to the posterior articular ridge, medially to the medial margin of the temporal fossa, anteriorly it is attached to the preglenoid plane
  26. 26. MANDIBULAR NECK - Laterally- the lateral condylar pole but Medially - dips below the medial pole. On the lateral part of the joint, the capsule is a well-defined structure that functionally limits the forward translation of the condyle.
  27. 27. This capsule is reinforced more laterally by an external TMJ ligament, which also limits the distraction and the posterior movement of the condyle. Medially and laterally- blends with the condylodiscal ligaments.
  28. 28. Anteriorly, the capsule has an orifice through which the lateral pterygoid tendon passes. This area of relative weakness in the capsular lining becomes a source of possible herniation of intra-articular tissues, and this, in part, may allow forward displacement of the disk.
  29. 29. The synovial membrane lining the capsule covers all the intra-articular surfaces except the pressure-bearing fibrocartilage. There are four capsular or synovial sulci situated at the posterior and anterior ends of the upper and lower compartments. These sulci change shape during translatory movements, which requires the synovial membrane to be flexible.
  30. 30. The ligament on each side of the jaw is designed in two distinct layers.  The wide outer or superficial layer is usually fan-shaped and arises from the outer surface of the articular tubercle and most of the posterior part of the zygomatic arch. There is often a roughened, raised bony ridge of attachment on this area.
  31. 31. The ligamentous fascicles run obliquely downward and backward to be inserted on the back, behind, and below the mandibular neck. Immediately medial to this layer, a narrow ligamentous band arises from the crest of the articular tubercle continuously, with attachment of the outer portion at this site.  This narrow inner or deep band runs horizontally back as a flap strap to the lateral pole of the condyle. An upper part of this band continues on to attach to the back of the disk, lateral to the condylar pole.
  32. 32. Arises from the angular spine of the sphenoid and petrotympanic fissure. Runs downward and outward. Insert on the lingula of the mandible.
  33. 33. 1. Laterally - lateral pterygoidmuscle. 2. posteriorly - auriculotemporal nerve. 3. anteriorly - maxillary artery. 4. Inferiorly - the inferior alveolar nerve and vessels a lobule of the parotid gland. 5. Medially - medial pterygoid with the chorda tympani nerve and the wall of the pharynx with fat and the pharyngeal veins intervening.
  34. 34. The ligament is pierced by the myelohyoid nerve and vessels. This ligament is passive during jaw movements, maintaining relatively the same degree of tension during both opening and closing of the mouth.
  35. 35. This is a specialized dense, local concentration of deep cervical fascia extending from the apex and being adjacent to the anterior aspect of the styloid process and the stylohyoid ligament to the mandible’s angle and posterior border.
  36. 36. This ligament then extends forward as a broad fascial layer covering the inner surface of the medial pterygoid muscle. The anterior edge of the ligament is thickened and sharply defined.
  37. 37. It is lax when the jaws are closed and slackens noticeably when the mouth is opened because the angle of the mandible swings up and back while the condyle slides downward and forward. This ligament becomes tense only in extreme protrusive movements. Thus, it can be considered only as an accessory ligament of uncertain function.
  38. 38. The synovial fluid comes from two sources: first, from plasma by dialysis, and second, by secretion from type A and B synoviocytes with a volume of not more than 0.05 ml.  However, contrast radiography studies have estimated that the upper compartment could hold approximately 1.2 ml of fluid without undue pressure being created, while the lower has a capacity of approximately 0.5 ml.
  39. 39. It is clear, straw-colored viscous fluid. It diffuses out from the rich cappillary network of the synovial membrane. Contains: Hyaluronic acid which is highly viscous May also contain some free cells mostly macrophages.
  40. 40. Functions: Lubricant for articulating surfaces. Carry nutrients to the avascular tissue of the joint. Clear the tissue debris caused by normal wear and tear of the articulating surfaces.
  41. 41. The way the teeth fit together may affect the TMJ complex. A stable occlusion with good tooth contact and interdigitation provides maximum support to the muscles and joint, while poor occlusion (bite relationship) may cause the muscles to malfunction and ultimately cause damage to the joint itself. Instability of the occlusion can increase the pressure on the joint, causing damage and degeneration.
  42. 42. Branches of External Carotid Artery 1. Superficial temporal artery 2. Deep auricular artery 3. Anterior tympanic artery 4. Ascending pharyngeal artery 5. Maxillary artery
  43. 43. The Blood supply to TMJ is only Superficial, i.e. there is no blood supply inside the capsule TMJ takes its nourishment from Synovial fluid
  44. 44. venous plexus maxillary vein Tranverse facial vein. Superficial temporal vein.
  45. 45. Auriculotemporal Deep temporal Massetric nerve
  46. 46. Anteriorly - Mandibular notch Lateral pterygoid Masseteric nerve and artery
  47. 47. A careful dissection of 16 intact human cadaveric head specimens revealed The location of the masseteric artery was then determined in relation to 3 points process: 1) the anterior-superior aspect of the condylar neck = 10.3 mm; 2) the most inferior aspect of the articular tubercle = 11.4 mm; 3) the inferior aspect of the sigmoid notch = 3 mm. Journal of Oral and Maxillofacial Surgery. 2009;67 (2) : 369–371
  48. 48. Posteriorly - parotid gland Superficial temporal vessels Auriculotemporal nerve
  49. 49. Laterally – Skin and fascia Parotid gland Temporal branches of facial nerve Medially - Tympanic plate (separates from ICA) spine of sphenoid Auriculotemporal & chorda tympani nerve middle meningeal artery maxillary artery
  50. 50. Superiorly – middle cranial fossa middle meningeal vessels Inferiorly – maxillary artery & vein
  51. 51. Rotational / hinge movement in first 20- 25mm of mouth opening Translational movement after that when the mouth is excessively opened.
  52. 52. Translatory movement – in the superior part of the joint as the disc and the condyle traverse anteriorly along the inclines of the anterior tubercle to provide an anterior and inferior movement of the mandible.
  53. 53. Hinge movement – the inferior portion of the joint between the head of the condyle and the lower surface of the disc to permit opening of the mandible.
  54. 54. Depression Of Mandible Lateral pterygoid Digrastric Geniohyoid Mylohyoid
  55. 55. Elevation of Mandible Temporalis Masseter Medial Pterygoids
  56. 56. Protrusion of Mandible Lateral Pterygoids Medial Pterygoids
  57. 57. Retraction of Mandible Posterior fibres of Temporalis
  58. 58. Mainly 4 forms are seen- 1. Convex-58% 2. Flat- 25% 3. Pointed-12% 4. Round- 3% ( mainly in children)
  59. 59. A. Early development: Develops relatively late compared to large joints of extremities. At 7th prenatal week jaw joint lacks condylar growth cartilage joint cavities, synovial tissue & articular capsule.
  60. 60. B. Condylar cartilage development Between 8-12 wk of I.U life cartilagenous condyles develop anteriorly to malleus incus articulation. Then altered by endochondral bone formation & fuses to posterior part of bony body of mandible. By 12th wk condyle consists of large mass of hyaline cartilage covered by a fibrous cap.
  61. 61. C . Articular disc formation; In 12th wk first appearance of TMJ cavity is seen & first of 2 compartments inferior or mandibular compartment is formed. A split appear in synovial mesenchyme & temporal or superior compartment is formed in next wk. Presence of both sup & inf compartment develops articular disc.
  62. 62. D . Fate of meckle’s cartilage; As mandible enlarges remnants of meckles cartilage becomes relatively smaller. At 18-20 i.u life it loses its function & disappears.
  63. 63. Occurs in 14th I.U life . Condyle grows by both interstitial & appositional growth of condylar cartilage. Formation of temporal fossa starts with development of heavy spicule of temporal bone superior to forming articular disc. Articular disc takes its characteristic shape & blends into articular capsule at 26th wk.
  64. 64. At 18-20 prenatal wk TMJ starts functioning. The condylar bone increases in size & density , & mandible undergoes changes in shape & size associated with differentiation & functioning of muscles of mastication.
  65. 65. Growth continues in 2nd decade of postnatal life a. Temporal fossa deepens as bone forms laterally & articular tubercle enlarges. b. Dense fibrous nature of disc & capsule becomes apparent. c. condyles continue endochondral like growth . Perichondral covering of condyle consists of 2 layers. -portion lying next to cartilage which is highly cellular & -outer layer which is fibrous.
  66. 66. Preauricular Dingman’s, Blair’s, Thoma’s,Al-kayat and Bramley’s, Popowitch’s Postauricular . Endaural approach Post ramal/ Hind’s approach Submandibular/Risdon’s approach Hemicoronal bicoronal
  67. 67. Basic incision given by Dingman(1951) Most basic & standard approach to tmj.
  68. 68. Blair & Ivy (1936) – “Inverted hockey stick “ incision. Facilities exposure of arch along with condylar area.
  69. 69. Thoma in 1958 Angulated vertical incision. -carried out across zygomatic arch infront of ear to avoid main trunk of facial nerve.
  70. 70. 1979. Modified preauricular approach. Facial nerve divides in front of auditory canal as near as 0.8cm & as far as 3.5cm Protection achieved by making incision through temporal fascia& periosteum down to arch not more than 0.8cm.
  71. 71. Hoops et al (1970), Alexander and James (1975) Highly cosmetic incision Disadvantage- poor access & visibility,the risk of external auditory meatus stenosis, infection & deformity of the auricle.
  72. 72. Lempart (1938) Short facial skin incision extending in to ext. auditory meatus Excellent cosmetics Disadvantage- Meatal stenosis or chondritis, injury to the branches of the facial nerve
  73. 73. Indication – surgeries of condylar neck & ramus area. Incision- 1cm behind ramus of mand. and extends 1cm below the lobe of ear. Highly cosmetic, excellent visibility and accessibility. Injury may occur to posterior facial vein and main trunk of facial nerve.
  74. 74. Risdon (1934) Mainly used for neck of condyle & ramus region. supplement to different tmj approaches for tunneling through the soft tissues to place a graft
  75. 75. Hemicoronal (unilateral) or bicoronal (bilateral) approach is used. More extensive but versatile approach for upper & middle regions of facial skeleton, zygomatic arch & TMJ. Advantage- scar is hidden in the hairline.