Applied anatomy of tmj

The applied anatomy of temporomandibular joint has many significant applications in maxillofacial surgery. Understanding these important anatomic relations- variations enables surgeons to perform the surgical procedures safely. Knowledge of these concepts helps us to recognize the problems and complications as and when they occur and manage them accordingly.

1. GOOD MORNING

2. Presented by : Dr. Samarth Johari (P.G 1 st year) Guided by : Dr. Gagan Khare (Professor) TEMPOROMANDIBULAR JOINT (Department of Oral & Maxillofacial Surgery)

3. CONTENTS Introduction Unique Features of TMJ Components Of TMJ Vasculature Of TMJ Relation Of TMJ Surgical Approaches To TMJ Conclusion References

4. INTRODUCTION TMJ is a ginglymoarthroidal joint ginglymus + arthrodia Hinge joint allowing backward & forward motion only Joint that allows gliding motion of the surfaces

5. Diarthroidal joint Synovial joint Has fibrous connective tissue capsule tightly attached to bones Compound joint composed of 4 articulating surfaces

6. Anatomically – Diarthroidal Joint : Discontinuous articulation of 2 bones Permitting free movement produced by associated muscles & limited by Ligaments Synovial Joint : Lined by synovial membrane on inner aspect which secretes synovial fluid Acts as a lubricant and provides metabolic & nutritional needs of non vascularized internal joint structures

7. Funtionally – Composed of 4 articulating surfaces : Articular facets of temporal bone Mandibular condyle Superior surface of articular disc Articular Disc Inferior surface of articular disc Divides the joint into 2 compartments Lower compartment – permits hinge motion & rotation ( ginglymoid ) Superior compartment – permits sliding/ transltory motion ( arthroidal ) Ginglymoarthroidal joint

8. UNIQUE FEATURES OF TMJ Bilateral diarthrosis – right & left function together Articular surfaces covered by fibrocartilage instead of hyaline cartilage Only joint of human body having rigid endpoint of closure (teeth making occlusal contact) Last joint to start developing (in 7 th week of I.U life)

9. COMPONENTS OF TMJ Mandibular Condyle Articular Surfaces Of Temporal Bone Cartilage and Synovium Articular Disk Muscular Components Ligaments

10. MANDIBULAR CONDYLE : An ovoid process located above the mandibular neck It is the articulating surface of the mandible Convex in all directions but wider latero -medially (15-20 mm) than antero -posteriorly (8-10 mm) Has a medial & lateral pole

11. Medial Pole Directed more posteriorly If long axes of 2 condyles are extended medially, they meet at basion on anterior limit of foramen magnum Forms an angle ranging from 145º to 160º Extends sharply inward from plane of ramus

12. Lateral pole Rough, bluntly pointed Articular surface lies on its antero -superior aspect, facing posterior slope of articular eminence of temporal bone Projects moderately form plane of ramus

13. II. ARTICULAR SURFACE OF TEMPORAL BONE : Situated on inferior aspect of temporal squama anterior to tympanic plate Comopsed of 3 parts – a.) Articular fossa or mandibular fossa b.) Articular eminence c.) Preglenoid plane

14. Mandibular Fossa Largest Concave structure extending from posterior slope of articular eminence to psotglenoid fossa (ridge between fossa & external acoustic meatus) Surface is thin Not a major stress bearing area

15. Articular Eminence Transverse bony prominence that is continuous across articular surface mediolaterally Thick & serves as major functional component

16. It is a flattened area anterior to the articular eminence Preglenoid Plane Articular tubercle is a nonarticulating process on lateral aspect of zygomatic root of temporal bone Serves as point of attachment of collateral ligaments

17. CARTILAGE AND SYNOVIUM : Inner aspect of the joint is lined by two types of tissues : a.) Articular C artilage b.) Synovium Space bound by these two structures synovial cavity filled with synovial fluid

18. Both articular surfaces of temporal bone & condyle are covered by dense articular fibrocartilage Capacity to regenerate & to remodel under functional stress

19. Lining of capsular ligament – synovial membrane thin, smooth, richly innervated vascular tissue without epithelium Synovium is capable of rapid & complete regeneration following injury Synovial fluid contains high concentration of hyaluronic acid (reason for viscous nature of fluid) Other contents of fluid – high % of albumin & low % of -2-globulin, alkaline phosphatase, leucocytes (<200/cubic mm)

20. Functions Of Synovial Fluid Lubrication of joint Phagocytosis of particulate debris Nourishment of articular cartilage

21. ARTICULAR DISK : Composed of dense fibrous connective tissue Non-vascularized & non-innervated Adapted to resist pressure 3 anatomic parts of disk as viewed from lateral aspect- a.) anterior band b.) central intermediate zone c.)posterior band

22. Intermediate zone is thinnest & generally the area of function between mandibular condyle and temporal bone Disk is flexible & adapts to functional demands of articular surfaces Attached to capsular ligament anteriorly, posteriorly, medially & laterally Some fibres of superior head of lateral pterygoid muscle insert on the disk at its medial aspect This stabilizes the disk to mandibular condyle during function

23. V. MUSCULAR COMPONENTS : Total 12 bilateral muscles influence mandibular motion & are divided into 2 groups by anatomic position - SUPRAMANDIBULAR GROUP Attaches to ramus & condylar neck Consists of : a.) temporalis b.) masseter c.) medial pterygoid d.) lateral pterygoid Predominantly acts as elevator, however, lateral pterygoid has depressor action also

24. INFRAMANDIBULAR GROUP Attaches to body & symphyseal area & hyoid bone Consists of : I. suprahyoid muscles (attach to both hyoid bone & mandible) - a.) digastric b.) geniohyoid c.) mylohyoid d.) stylohyoid II. Infrahyoid muscles – a.) sternohyoid b.) omohyoid c.) sternothyroid d.) thyrohyoid Suprahyoid muscles depress mandible when hyoid bone is fixed & elevate hyoid bone when mandible is fixed Infrahyoid muscles fix hyoid bone during depressive movements of mandible

25. LATERAL PTERYGOID & MEDIAL PTERYGOID MUSCLES

26. MASSETER MUSCLE TEMPORALIS MUSCLE

27. VI. LIGAMENTS : Composed of collagen Act as restraints to motion of condyle & disk

28. FUNCTIONAL LIGAMENTS Serve as major anatomic components of joints Types of functional ligaments : Collateral Capsular Temporomandibular ACCESSORY LIGAMENTS Serve as passive restraints on mandibular motion Types of accessory ligaments : Sphenomandibular Stylomandibular

29. COLLATERAL LIGAMENTS k/a diskal ligaments Attaches disk to lateral & medial poles of each condyle Function – restrict movement of disk away from condyle Permit rotation of condyle but also forces disk to accompany condyle during translatory motion

30. CAPSULAR LIGAMENTS Attaches joint superiorly to temporal bone (mandibular fossa & eminence) & inferiorly to neck of condyle (along edge of articular facet) Surrounds joint spaces & disk Attaches anteriorly, posteriorly, medially, laterally Blends with collateral ligaments Function – resist medial, lateral & inferior forces Contains synovial fluid in superior & inferior joint spaces

31. TEMPOROMANDIBULAR LIGAMENTS k/a lateral ligaments Located on lateral aspect of each TMJ Single structures that function in paired manner with corresponding ligament on opposite TMJ Divided into – outer oblique portion inner horizontal portion

32. SPHENOMANDIBULAR LIGAMENTS Arises from spine of sphenoid bone Descends into fan like insertion on lingual & lower portion of medial side of condylar neck Serves as point of rotation during activation of lateral pterygoid muscle Helps in translation of mandible

33. STYLOMANDIBULAR LIGAMENTS Descends from styloid process to posterior border of angle of mandible Blends with fascia of medial pterygoid muscle Functions similar to sphenomandibular ligament Limits excessive protrusion of mandible

34. VASCULATURE OF TMJ Nerve supply of TMJ : a.) Auriculotemporal Nerve – ( i ) runs below and behind the joint (ii) supplies posterior, medial & lateral parts of joint

35. b.) Nerve To Masseter – sends a twig to the joint

36. c.) Deep Temporal Nerve – supplies anterior parts of the joint

37. Arterial Supply Of TMJ : only superficial blood supply of the joint is present no blood supply inside the capsule takes nourishment from synovial fluid superficial blood supply is by branches of external carotid artery – a.) Superficial Temporal Artery b.) Deep auricular Artery c.) Anterior Tympanic Artery d.) Maxillary Artery e.) Ascending Pharyngeal Artery

38. Venous Supply Of TMJ : a.) Maxillary Vein b.) Transverse Facial Vein c.) Superficial Temporal vein

39. RELATION OF TMJ Anteriorly : Mandibular notch Lateral pterygoid Masseteric nerve & artery

40. Applied Anatomy Of Masseteric Nerve 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 = 3mm Journal of Oral and Maxillofacial Surgery. 2009;67 (2) : 369–371

41. Posteriorly : a) Superficial temporal vessels (ligated during pre-auricular approaches) b) Parotid gland c) Auriculotemporal nerve

42. Laterally : Skin & fascia Parotid gland Temporal branches of facial nerve

43. Applied Anatomy Of Facial Nerve Exits skull at stylomastoid formen Incise the superficial layer of temporalis fascia & periosteum over arch within 8mm boundary, to prevent damage to branches of upper trunk Classic Article By Alkayat & Bramely (1980)

44. Medially : Tympanic plate (separates from ICA) Spine of sphenoid Auriculotemporal & chorda tympani nerve Middle meningeal artery

45. Applied Anatomy Of Auriculotemporal Nerve 1 st branch of 3 rd division of trigeminal nerve Exits from foramen ovale Runs medial to lateral behind neck of condyle Sensory supply to skin in temporal & preauricular region & innervates capsule of TMJ Can be damaged while approaching to TMJ

46. SURGICAL APPROACHES TO TMJ

47. Preauricular Endaural Postauricular Rhytidectomal Retromandibular Intraoral Types Of Surgical Approaches To TMJ

48. Basic incision given by Dingman in 1951 No extensive shaving is required Margin of only 1cm from superior aspect of incision is adequate Inverted hockey stick incision that follows natural crease in front of tragus Preauricular Approach

49. Cosmetic modification or preauricular approach Incision is placed on prominence of tragus itself Tragal cartilage has to be protected to prevent perichondritis Endaural Approach

50. Popularised by Walter’s & Geist in 1983 Disadvantages : ( i ) Auricular Stenosis (ii) Can not be used in cases of joint infection & chronic otitis externa Advantages : ( i ) Excellent exposure to complete joint (ii) Ability to camouflage scar Postauricular Approach

51. Used in cases where extensive joint exposure is required e.g major tumor resections Endaural incision is extended in curvilinear fashion around mastoid tip & S - shaped incision ending in submandibular incision Allows access to posterior border of mandible & allows to locate main trunk of facial nerve Rhytidectomy Approach

52. Used for neck of condyle & ramus region Supplemets different TMJ approaches for tunneling through soft tissue for placing grafts Marginal mandibular branch of facial nerve & retromandibular vein have to be protected Retromandibular Approach

53. CONCLUSION The applied anatomy of temporomandibular joint has many significant applications in maxillofacial surgery. Understanding these important anatomic relations- variations enables surgeons to perform the surgical procedures safely. Knowledge of these concepts helps us to recognize the problems and complications as and when they occur and manage them accordingly.

54. REFERENCES Colour Atlas Of Temporomandibular Joint Surgery by Peter D. Quinn Oral Anatomy by Sicher and DuBrul Gray’s Anatomy Oral & M axillofacial Surgery by Fonseca Atlas of Operative Maxillofacial Trauma Surgery by Springer Peterson’s Principles Of Oral & Maxillofacial Surgery