Temporomandibular Joint presentation.pptx

Temoromandibular joint

1. Biomechanics of Temporomandibular joint 1

2. Contents : Introduction Structure Articular surface Articular disk Capsule and ligaments Functions Mandibular motions Control of the disk Muscular control of TMJ Pathomechanics of TMJ 2

3. Introduction: TMJ is formed Condyle (head) of the mandible Articular eminence of the temporal bone An interposed articular disk Synovial joint which permits a wide range of rotation as well as translation The articular surface are covered by dense collagenous tissue: fibrocartilage 3

4. 4 Fibrocartilage has a great capacity to remodel in response to physiological load. It is required because TMJ is subjected to tremendous forces everyday, e.g. during biting. It gets its nutrition from the synovial fluid present inside the joint.

5. The disk separates the TMJ Upper joint Lower joint Upper joint: Gliding joint Translatory movements Lower joint: Hinge joint Rotatory movements Very oftenly used joint in the body 5

6. Structure: Articular surface: 1.Mandible : distal or moving segment of TMJ Body 2 rami Angle of the jaw : body and ramus join Mandibular condyles end of the ramus posterio- superior aspect. Each condyle protrudes medially 15-20 mm from the ramus. Mandibular condyle Medial pole Lateral pole 6

7. 7 Portion of condyle which can be readily palpated is the lateral pole. It lies just in front of external auditory meatus . Medial pole is deep and cannot be palpated. Posterior aspect of condyle can be palpated if a fingertip is placed in external auditory meatus and pushed anteriorly . As the jaw is opened & closed, the movement felt is that of mandibular condyle .

8. 8 Lines following the axis of mediolateral poles of each condyle will intersect just anterior to the foramen magnum.

9. Mandible Ant portion of the condyle is composed of trabecular bone and is the articular portion of the condyle. There is another projection located Ant to the condyle coronoid process It serves as an attachment for the temporalis muscle. 9

10. 2. Temporal bone: proximal or stationary segment of TMJ The condyles glenoid fossa of the temporal bone. Glenoid fossa the post glenoid spine and the articular eminence of the temporal bone. The articular eminence, however has a major area of trabecular bone and serves as primary articular surface. The articular surface of the condyle and the articular eminence of temporal bone are covered with fibrocartilage . 10

11. The articular collagen fibers are aligned perpendicular to the bony surface in the deep layers. Fibers near the surface of the articular covering are aligned in a parallel arrangement to facilitate gliding of the joint surface. 11

12. Articular disk: It is biconcave It allows the convex surface of the condyle and convex surface of the articular eminence to remain congruent throughout the motion. Disk is attached to the medial/lateral pole of the condyle disk to rotate freely in ant-post direction. Thickness of the articular disk: Anterior: 2mm Intermediate:1mm Posterior:3mm 12

13. 13 Anterior and posterior surface is vascular and innervated but the middle part is avascular and not innervated Middle portion is force accepting segment. Middle portion receives its nutrition from synovial fluid. Disk does not have the ability to repair and remodel.

14. Disk is divided into: Posterior: convex superior & concave inferior Intermediate: concave inferior & flat superior Anterior: flat inferior & slightly concave superior 14

15. Posterior region of disc attaches: Capsule Retrodiskal pad. Two bands Sup: post attached to tympanic plate Inf : neck of condyle . Anterior region of disc attaches: Capsule of TMJ. Tendon of the superior head of the lateral pterygoid muscle. 15

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17. Structure of superior laminae: Made of elastic fibers It allows the disk to translate anteriorly along the articular eminence during mouth opening. It also helps in repositioning the disk posteriorly during mouth closing. Inferior laminae: It is attached to the neck of the condyle and is inelastic. It limits forward translation. Between the 2 lamina there is a loose areolar connective tissue rich in arterial and neural supply. 17

18. Disk function: It provides congruence of the joint surface through a wide range of positions. Thick-thin-thick arrangement provides a self centering mechanism for the disk on the condyle . Increases stability of joint. Normally the disc slides with the translating condyle & movement is governed by: intraarticular pressure, muscle force & by collateral ligaments 18

19. Capsular & ligamentous structure TMJ and the disc is surrounded by loose fibrous capsule. Capsular fibers run from temporal bone disk and from the disk neck of the condyle. Capsule above the disk is loose whereas below the disk is tight. Consequently, disk is attached more firmly to condyle below, and is freer to move on articular eminence above. 19

20. 20 Capsule is highly vascularized and innervated Capsule supports the joint and provides information about position and movement. Capsule is attached: Sup: rim of mandibular fossa , as far ant as articular eminence Inf : collateral ligaments that forms the periphery of the articular disc Ant: tendon of sup head lat pterygoid muscle. Capsule is thin and loose in its anterior, medial and posterior aspects, but lateral aspect is stronger and is reinforced with longer fibers.

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22. Ligaments: Temporomandibular ligament (lateral ligament) Stylomandibular ligament Sphenomandibular ligament 22

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24. Temporomandibular ligament: 2 parts Outer oblique portion Inner portion Outer oblique portion: attached to the neck of the condyle and articular eminence. It serves as a suspensory ligament, Limits downward and posterior motion of the mandible, Limits rotation of the condyle during mouth opening 24

25. 25 Inner portion: attached to the lateral pole of the condyle , posterior portion of the disk and to the articular eminence Limits the posterior translation of the condyle Primary function is to stabilize the lateral side of the capsule. Neither of the bands limit the forward translation of condyle on disk, but they do limit lateral displacement.

26. Stylomandibular ligament: Band of deep cervical fascia that runs from styloid process of the temporal bone to the posterior border of the ramus of the mandible. It inserts between the masseter muscle and medial pterygoid muscle. It limits the protrusion of the jaw. 26

27. Sphenomandibular ligament: Attaches to the spine of the sphenoid bone and to the middle surface of the ramus of the mandible. It serves to suspend the mandible and check the mandible from extreme forward translation. 27

28. Mandibular motions: Mandibular depression (mouth opening) Mandibular elevation (mouth closing) Mandibular protrusion (jutting the chin forward) Mandibular retrusion (sliding the teeth backward) Lateral deviation (sliding the teeth to either side) 28

29. Osteokinematics : 29 Depression and Elevation: Depression of mandible: opens the mouth Max opening-yawning and singing In adult: opening is avrg around 50 mm (3 knuckles of PIP jt ) mastication :18mm- 36 mm (2 knuckles of PIP jt ) Elevation of mandible: closes the mouth Action used to grind the food during mastication

30. 30 Protrusion and Retrusion : Protrusion : when all points of mandible translates ant the same amount without significant rotation. Teeth separate Should be adequate to allow upper & lower teeth to touch edge to edge. Retrusion : reverse of protrusion when all points of mandible translates post the same amount 3mm Lateral deviation side-side translation In adult: avg 8mm Normal asymmetrical movement of jaw.

31. Arthrokinematics Mandibular elevation and depression: 31

32. 32 MANDIBULAR DEPRESSION : Symmetrical motions. One conceptual framework describes two sequential phases: rotation and glide. In the rotation phase of mouth opening, there is pure anterior rotation (spin) of the condyle on the disk in the lower joint .This has also been described as posterior rotation of the disk on the condyle . The second phase involves translation of the disk- condyle unit anteriorly and inferiorly along the articular eminence. This motion occurs in the upper joint between the disk and the articular eminence and accounts for the remainder of the opening.

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34. 34 Of normal range of motion (40-50mm), between 11 mm and 25 mm is gained from rotation of the condyle in the disk, whereas the remainder is from translation of the disk and condyle along the articular eminence. The second model , based on more recent research, argues that the components of rotation and gliding are present but occur concomitantly rather than sequentially. That is, both rotation and gliding are present throughout the range of mandibular depression and elevation, starting at the initiation of mouth opening.

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36. MANDIBULAR ELEVATION: Mandibular elevation is reverse of depression. Consists of translation of disk- condyle unit posteriorly and superiorly and of posterior rotation of condyle on disk. 36

37. CONTROL OF DISK DURING MANDIBULAR ELEVATION AND DEPRESSION: 37 Passive control : capsulo-ligamentous attachment of disk to condyle . Active control : disk’s attachment anteriorly to sup portion of lateral pterygoid muscle. MOUTH OPENING: Medial & lateral attachment of disk to condyle limit the motion between disk and condyle to rotation. During translation of condyle , biconcave shape of disk causes it to follow the condyle without any additional active or passive assistance.

38. Inf retrodiskal lamina limits forward excursion of disk. MOUTH CLOSING: Elastic nature of sup retrodiskal lamina applies posterior distractive force on disk. Sup portion of lat pterygoid shows eccentric activity and controls posterior movement of disk. 38

39. PROTRUSION and RETRUSION During protrusion, the two heads of the lateral pterygoid contract and cause the disks and condyles to slide anteriorly and inferiorly. This takes place in the upper compartment. No rotation. Retrodiskal tissue stretch 6-9mm to allow motion to occur. 39

40. 40 During mandibular retrusion , these structures slide posteriorly and superiorly while still in the superior cavity. This is accomplished by the temporalis . Tension in lateral lig limits this motion as does compression of soft tissue in retrodiskal area between condyle and posterior glenoid spine.

41. LATERAL MOVEMENT Lateral movement of the jaw requires that different movements occur concurrently in the TMJs. For e.g , through the contraction of the two heads of the left lateral pterygoid, lateral movement to the left occurs. This necessitates a rotation occurring in the left joint and an anterior gliding taking place in the right joint Functional measurement: use of width of two upper central incisors. If mandible can move full width of one of central incisors in each direction, motion is considered normal. 41

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43. 43 Another asymmetric movement is rotation of one condyle and depression of another. Chin moves downward and deviates from midline slightly towards the condyle that is spinning. Used in chewing and grinding the food.

44. Normal chewing: 44

45. MUSCLES Digastric Pterygoids Temporalis Masseter 45

46. Digastric Muscle 46

47. The digastric muscle is the muscle most responsible for opening the lower jaw (in combination with the coordinated contraction of the lateral pterygoid muscles). Composed of two portions connected in the middle by a strong tendon.  Posterior portion arises from mastoid notch Anterior portion from inferior mandible Tendon that joins two portions is attached by fibrous loop to hyoid bone in the neck. Hyoid bone must be stabilised for digastric muscle to act as a depressor of mandible. 47

48. Lateral pterygoid 48

49. 49 Two parts Upper belly inserts into the articular disk inside the TMJ.  Lower belly inserts into the neck of the condyle.  Function: Keep the articular disk always situated between the closest points of contact between the condyle and the glenoid fossa during both the rotational phase of jaw opening and the translational phase Inferior portion is depressor.

50. Temporalis 50

51. The temporalis is one of three muscles that close the jaw and clench the teeth. It's origin: periosteum (covering of the bone) of  the temporal fossa.  It forms a thick tendon which passes under the zygomatic arch and Inserts into the medial surface (the inside surface) and the anterior border of the coronoid process.  The way the muscle is leveraged gives it a great amount of power , and splinting in the temporalis can cause serious headaches 51

52. Masseter 52

53. Origin :on both the outside and inside of the zygomatic process of the maxilla and the zygomatic arch. Inserts into a broad part of the lower jaw, along the lateral surface of the coronoid process, the ramus and the angle of the mandible.    53

54. Medial Pterygoid 54

55. Origin: from the medial surfaces of the lateral pterygoid plate Inserts to the undersurface of the temporal bone.  The fibers of the medial pterygoid are directed downward and backward, just like the masseter , only on the inside of the mandible.  The insertion of this muscle is to the inside of the lower border and angle of the mandible 55

56. These two muscles are more or less "twins", the masseter acting on the outside of the lower jaw and the medial pterygoid on the inside.  56

57. 57 Protrusion of mandible: B/L contraction med and lat pterygoid and masseter Retrusion : B/L action of temporalis and anterior portion of digastric . Ipsilateral lateral excursion of mandible : U/L contraction of temporalis . Contralateral lateral deviation of mandible : Medial & lateral pterygoid .

58. Secondary muscles 58 Suprahyoid and infrahyoid muscles Suprahyoid muscles : attach between the base of cranium, hyoid, and mandible ( digastric , geniohyoid , mylohyoid , stylohyoid ) Infrahyoid muscles: attach (sup & inf ) thyroid cartilage, sternum, scapula ( omohyoid , sternohyoid , sternothyroid , thyrohyoid ) These muscles: speech, tongue movement, swallowing and controlling boluses of food before swallowing With the hyoid bone stabilized by the activation of infrahyoid muscle- suprahyoid muscles assist with depression.

59. Muscles of mastication 59 Primary muscles Secondary muscles Masseter Suprahyoid Temporalis Infrahyoid Medial pterygoid Lateral pterygoid

60. Actions of muscle of mastication on mandible: Muscle Elevation Depression Lat. Excursion Protrusion Retrusion Masseter Strong --------- Weak (ipsilateral ) Weak -------- Medial pterygoid Strong -------- Strong (contralateral) Weak ---------- Lateral pterygoid (sup) Stabilizer ---------- Strong (contralateral) Strong ---------- Lat pterygoid ( inf ) --------- Strong Strong (contralateral) Strong ----------- Temporalis Strong ---------- Weak (ipsilateral) --------- Strong 60

61. The resting position of the TMJ is with the mouth slightly open, the lips together and the teeth not in contact. When the teeth are clenched, the TMJs are in their closed packed position. 61

62. RELATIONSHIP WITH CERVICAL SPINE 62 Many muscles that attach to mandible also attach to cranium, hyoid & clavicle. Thus muscles may act not only on mandible, but also on atlanto -occipital joint & cervical spine. Proper posture minimizes the force produced by the cervical extensors and other cervical muscles necessary to support the weight of the head. Poor cervical posture over time may lead to adaptive shortening or lengthening in muscles around the head and cervical spine, affecting range of motion, muscular force production capacity, and joint morphology in the involved region.

63. 63 Many of the symptoms reported by a person with TM joint dysfunction are similar to the symptoms reported by a person with primary cervical spine problems. With the intimate relationship of these two areas, any client being seen for complaints in one area should have the other examined as well

64. TM/CERVICAL JOINT INTERRELATIONSHIPS 64 A forward head posture frequently involves extension of the occiput and the upper cervical spine, leading to compensatory flattening of the lower cervical spine and upper thoracic spine to achieve a level head position. With the occiput extended on the atlas (C1), the suboccipital tissues adapt and shorten .

65. 65 The suboccipital tissues include the anterior atlantoaxial and atlanto -occipital ligaments ( cephalad continuations of the ligamentum flavum ), the posterior belly of the digastric muscles, the stylohyoid muscles, and the upper fibers of the upper trapezius , semispinalis capitis , and splenius capitis muscles. The forces necessary to maintain the head against gravity with a poor cervical posture and forward head result in muscle imbalance and altered movement patterns. Such alterations typically lessen the capacity of particular structures to meet the thresholds for adaptive responses to physical stresses.

66. 66 Increased tension from shortening of the suboccipital tissues may lead to headaches that originate in the suboccipital area, limitation in active range of motion of the upper cervical spine, and TM joint dysfunction. Furthermore, pain in the TM region may be referred from the cervical region . Thus, it is proposed that cervical posture should be normalized to successfully treat dysfunction in the TM joint complex

67. TM/RESPIRATORY/CERVICAL DYSFUNCTION 67 A person who has difficulty breathing through the nose will often hyperextend the upper cervical spine to more fully open the upper respiratory tract. Such a cervical posture places the upper and lower teeth in contact with each other and may affect the resting position of the TM joint. In turn, the muscles surrounding the TM joint complex expend greater energy to maintain this posture.

68. 68 Resistance to inspiration may also lead to use of accessory muscles of respiration (scalene and sternocleidomastoid muscles) to assist with breathing. Use of these accessory muscles may lead to a forward head posture. Such a posture contributes over time to a cycle of increasing musculoskeletal dysfunction, including repeated episodes of TM inflammation that can result in fibrosis of the TM joint capsule.

69. DENTITION 69 32 teeth. Divided into 4 quadrants Central incisors: maxillary & mandibular Occlusal position Freeway space Helps in reducing intra- articular pressure, stress on articular structures, and the tissues of the area are able to rest & repair.

70. AGE RELATED CHANGES IN TMJ: 70 Disk shows perforations, roughness, and thinning. Osteoarthritis may be expected. Degeneration seen in X ray or MRI not necessarily associated with symptoms or dysfunctions. In deranged disks, collagen fibers run more irregularly as compared to controls.

71. Pathomechanics / Dysfunction: 71

72. Causes of dysfunction: 72 Direct trauma Poor posture Bruxism (grinding of teeth)

73. Inflammatory Conditions 73 Capsulitis Synovitis (effusion in synovial membrane of joint) Causes of inflammation : Rheumatoid arthritis is the most common cause of such inflammatory conditions, but gout, psoriatic arthritis, ankylosing spondylitis , etc. Result of inflammatory conditions : pain & diminished mandibular depression.

74. 74 Rheumatoid arthritis is a chronic systemic condition with articular and extra- articular involvement. The primary symptoms of rheumatoid arthritis include pain, stiffness, edema, and warmth. This autoimmune disorder targets the capsule, ligamentous structures, and synovial lining of the joint complex, resulting in joint instability & joint deformity. Multiple bilateral joints are typically involved with this disease

75. Capsular Fibrosis 75 Inflammation can lead to adhesions that restrict the movement of the disk and limit the function of the TMJ. Arise from unresolved or chronic inflammation of the joint capsule, which results in the overproduction of fibrous connective tissue. Causes: prolonged periods of immobilization, trauma, or arthritis

76. 76 Active motion of the TM joint will typically elicit pain. Physical examination will reveal limited or altered osteokinematic motions, suggestive of a decrease in translatory motion in the involved side.

77. Osseous Mobility Conditions 77 include joint hypermobility and dislocation Joint hypermobility may be a generalized connective tissue disorder that involves all joints of the body, including the TM joints. It is a result of laxity of the joint capsules, tendons, and ligaments. Individuals seen clinically for this condition typically report the jaw “going out of place,” producing noises, or “catching” when the mouth is in the fully opened position.

78. 78 increased indentation posterior to the lateral pole. Joint noises occur at the end of mandibular depression and at the beginning of mandibular closing. These noises may be heard by the patients but are more often palpable only by the clinician. Mandibular depression will exceed 40 mm.

79. Dislocation Dislocation  of the TM Joint involves the displacement of the condyle  anterior to the articular eminence, thus “sticking” in the extreme end-range position. Once the condyle slides anterior to the articular eminence, reduction is quite difficult owing to the spasm in virtually all of the muscles of mastication.  Spasm in the masseter , temporalis and medial pterygoid muscles causes them to apply extreme upward force on the condylar head while spasm in the lateral pterygoid applies massive anterior force.  These forces lock the condyle into its anteriorly displaced position making self reduction nearly impossible. 79

80. 80 Full mouth opening results in deflection (lateral deviation) of the jaw to the contralateral side of the involved TM joint, and the inability to close the mouth. The individual may or may not experience pain with this condition.

81. Articular Disk Displacement 81 Articular disk displacement conditions include disk displacement with reduction and disk displacement without reduction . Individuals exhibiting disk displacement with reduction experience “ joint noise” at two intervals : during mandibular opening and mandibular closing. This joint noise is known as a reciprocal click and is a key sign in diagnosing disk displacement with reduction.

82. 82 In this situation, the mandibular condyle is in contact with the retrodiskal tissue at rest, rather than with the disk. On mouth opening, the condyle slips forward and under the disk to obtain a normal relationship with the disk. When the condyle slips under the disk, an audible click is often present. Once the condyle is in the proper relationship with the disk, motion continues normally through opening and closing until the condyle again slips out from under the disk, when another click is heard. A click would be expected to signify that the condyle and disk have lost a normal relationship.

83. 83 When the click occurs early in opening and late in closing, the amount of anterior displacement of the disk is relatively limited. The later the click occurs in the opening phase, the more severe the disk dislocation is. Individuals with disk displacement with reduction may remain in this state or progress rapidly to disk displacement without reduction. The posterior attachments to the disk become overstretched and unable to relocate the disk during mandibular depression, which results in the loss of the reciprocal clicks.

84. 84 Clients with acute disk displacement without reduction demonstrate limited mandibular motion as a result of the disk’s creating a mechanical obstruction to condylar motion , rather than facilitating condylar translation. Individuals with disk displacement without reduction typically describe an inability to fully depress the mandible, as well as difficulty performing functional movements involving the jaw such as chewing, talking, or yawning.

85. DEGENERATIVE CONDITIONS:Osteoarthritis & Rheumatoid Arthritis Osteoarthritis  is often found in the TMJ in older persons, although it is generally symptomless. Cartilage of the joint degenerates Cause: repeated minor trauma. Grating sensation : opening and closing of mouth Severe OA: Cannot open the mouth Jaw shifts to the affected side, unable to move it back X-Ray: reduced joint space, osteophyte formation, sclerosis, etc. 85

86. References : 86 Joint structure and function: Norkin C Kinesiology of the musculoskeletal system: Neuman D.A

87. 87 THANK YOU!