Genioplasty

Genioplasty of the mandible

1. GENIOPLASTY Pesented by KANIMOZHIY SENGUTTUVAN 2 nd year post graduate Thaimoogambigai Dental College and Hospital

2. INTRODUCTION Genioplasty is the surgical procedure used to alter the size and morphology of the bony chin with concomitant changes in the surrounding soft tissues. It can be used as a single procedure or it can be used as an adjunctive procedure along with other major osteotomies of the jaw.

3. • Successful treatment of the orthognathic surgical patient is dependent on careful diagnosis. • Cephalometrics can be an aid in the diagnosis of skeletal and dental problems and a tool for simulating surgery and orthodontics treatment.

4. While patients seeking about facial cosmetic surgery often focus on structures such as the nose, the eyes, and the laxity of their skin, but the lower third of the face is an area that could be surgically modified to improve overall facial appearance and harmony. The profile of a patient can be significantly altered with either a chin augmentation or reduction procedure. This, in turn, has a significant effect on overall facial symmetry. Chin deformity can be corrected by genioplasty approaches.

5. History of Genial Procedures Hofer (1942) first described horizontal sliding osteotomy- extraoral incision Converse( 1950), discussed the feasibility of bone grafts introduced through intraoral approaches Trauner and Obwegeser , (1957), used the horizontal osteotomy through an intraoral incision with de--gloving of the anterior mandible. Converse and Wood-Smith described various applications and versatility of, the horizontal osteotomy

6. Reichenbach and colleagues (1965)proposed wedge osteotomy and vertical shortening of the chin . Hinds and Kent( 1969) realize the importance off maintaining the soft tissue attachment along the inferior segment and the role of these attachments in achieving maximal soft tissue change.

7. CHIN • The chin should, however, be evaluated in all three dimensions. The width of the chin should be assessed in relation to the overall facial shape . • A narrow chin often has a knobby appearance, and if surgical advancement of the chin is planned, widening of the chin should be contemplated . • The labiomental fold, chin shape, relation to the dental midline, symmetry, and cant of the lower border should be considered.

8. SURGICAL ANATOMY The primary sensory innervation to the chin area is from the paired mental nerves that exit the body of the mandible near the apices of the premolar teeth.

9. The primary motor component to the muscles associated with the anterior aspect of the chin are from the buccal and marginal mandibular branches of the facial nerve . These muscles include the depressor labii inferioris , depressor anguli oris , mentalis and orbicularis oris muscles.

10. The primary muscle involved with the genioplasty procedure itself is the mentalis muscle , which provides the primary vertical support to the lower lip . The depth of labiomental fold may dictate which technique is suitable. The mentolabial sulcus becomes less pronounced in a vertical lengthening of the chin . Position of mental foramen is utmost importance during surgery. The mentalis muscle elevates the chin at a place just below the tooth roots . The arterial supply to the muscles of the chin area is from the inferior labial arteries , which are terminal extensions from the facial arteries.

11. CLASSIFICATION OF CHIN DEFORMITIES Class I macrogenia a. Horizontal b. Vertical c. Combination of both Class II microgenia a. Horizontal b. Vertical c. Combination of both Class III combined a. Horizontal macrogenia with vertical microgenia b. Horizontal microgenia with vertical macrogenia

12. Class IV assymmetric chin a. Short anterior facial height b. Normal anterior facial height c. Long anterior facial height Class V Witch’s chin(soft tissue ptosis ) Class VI pseudomacrogenia Class VII pseudomicrogenia

13. INDICATIONS • Surgical goals include creating an aesthetically pleasing facial contour and establishing proportionate facial height.

14. CONTRAINDICATIONS Carefully evaluate the teeth and the height of the mandible prior to surgery . Long teeth with a short mandibular height is a relative contraindication for an osseous genioplasty or an aggressive bony reduction .

15. PREOPERATIVE EVALUATION • Cephalometric evaluation • Soft TissueAnalysis Lip competence Facial height Facial symmetry Lip–chin relationship Cervicomental angle Nose–chin evaluation • The skin of the lower face

16. CEPHALOMETRIC EVALUATION

17. A combination of Down’s, Steiner’s and Tweed’s analysis is used to assess the relationships of skeletal and dental structures so that an accurate diagnosis of dental and facial anomalies can be made. The information obtained from this analysis is considered when performing sagittal or vertical changes in chin position.

18. SOFT TISSUE EVALUATION GONZALEZ – ULOA & STEVEN’S ANALYSIS A line is dropped from the soft tissue Nasion perpendicular to Frankfort horizontal plane This line is called zero meridian Ideally Soft tissue pogonion of the chin should be at or just posterior to the zero meridean

19. Merrifield’s ‘Z’ angle is a line from the soft tissue chin tangent to the most procumbent lip, which forms an angle with the Frankfort horizontal plane. Normal range- 70 to 80 degrees

20. RICKETTS LIP ANALYSIS Reference line connects NOSE TIP TO SOFT TISSUE POGONION- E LINE Lip are analyzed depending on the distance of the lips from the line NORMAL VALUES UPPER : 2-3 mm LOWER: 1-2 mm

21. A line connecting the midpoint of the columella of the nose to the soft tissue pogonion . According to C.C. Steiner, the lips should fall on this line and any deviation shows prominence or flatness of the lip. S-LINE (ESTHETIC PLANE OF STEINER)

22. • Lastly, the skin of the lower face should be examined in both frontal and profile views, noting the quality, thickness, and laxity as well as any irregularities. • Because these factors can impact outcome, a patient’s expectations should be managed by discussing these factors in the preoperative setting .

23. SURGICAL PROCEDURE

24. STEP 1: INFILTRATION OF SOFT TISSUE WITH A VASOCONSTRICTOR Infiltrate the area of dissection with 2 mL of local anesthetic containing a vasoconstrictor (epinephrine in a concentration of 1:100,000) 10 minutes before surgery.

25. STEP 2: MUCOSAL INCISION Make the first soft tissue incision through the labial mucosa of the mandible from just distal to the canine to a similar point on the contralateral side. Branches of the mental nerve can often be identified in the submucosal tissue laterally. Leave at least 5 mm of non-keratinized mucosa superiorly to make later suturing easier.

26. STEP 3: SUBMUCOSAL INCISION Make the second incision through the submucosal tissue and periosteum onto the bone, avoiding damage to the mental nerve at the lateral aspects of the incision. This incision is angled at 45 degrees to the bone so that more submucosal tissue and periosteum remain at the superior aspect, which will make later suturing easier The soft tissue incision is angled to maintain more submucosal tissue for later ease of suturing.

27. STEP 4: MUCOPERIOSTEAL DISSECTION Start the mucoperiosteal dissection from the center , and dissect laterally and inferiorly. Identify the mental nerves bilaterally. Also elevate the mucoperiosteum at the superior aspect to make later suturing easier. Subperiosteal dissection is carried downward and laterally to identify the mental nerve. The mucoperiosteum at the superior aspect is also elevated to make reapproximation of the mentalis muscle and mucosa easier.

28. STEP 5: ESTABLISHING REFERENCE POINTS Use a 701 bur to mark the dental midline on the bone superiorly and inferiorly to the intended osteotomy. Make small, shallow holes, keeping the roots of the incisors in mind , and score a line into the cortex to connect the holes. The dental midline is marked on the bone. Two vertical reference lines are placed lateral to this line.

29. Deepen the inferior hole by angling the bur superiorly and extending the hole well through the cortex. This hole is intended for the placement of a positioning wire later in the procedure. Place the hole in thick bone to ensure that the wire will not pull through. For accurate repositioning of the chin, place reference marks approximately 15 mm lateral to the midline to assist with symmetric repositioning. A superiorly angled hole is drilled in the midline below the intended osteotomy line. A positioning wire will be placed through this hole once the chin has been mobilized.

30. STEP 6: OSTEOTOMY DESIGN The osteotomy should be performed at least 5 mm below the roots of the incisors and 5 mm below the mental foramen . View and mark the angle of the osteotomy as planned on the surgical visual treatment objective. The angle and position of the osteotomy is seen. The position of the mental nerve and the roots of the incisors and canines should be kept in mind

31. Most genioplasty procedures are performed to improve the anteroposterior position of the chin . However, consideration must be given to the angulation of the osteotomy because variations in the angle will lead to changes in the vertical dimension of the chin, with obvious esthetic consequences. The angle of the osteotomy creates a plane along which the bony segment will slide. The change of the angulation of the osteotomy and its effects on the vertical dimension after repositioning are demonstrated.

32. The steepness of the angle of the osteotomy will be influenced by the esthetic requirements, the roots of the incisors and canines, and the position of the mental foramen. Keep in mind that the course of the mental nerve prior to its exit through the mental foramen is approximately 5 mm inferior and anterior to the foramen.

33. STEP 7: OSTEOTOMY OF THE CHIN Perform the osteotomy with an oscillating saw by starting in the centre and cutting laterally . Ensure that both cortices are osteotomized. Failure to include the lower border in the osteotomy will lead to an unfavourable fracture at the inferior border of the bone segment and thus inaccurate repositioning of the chin (unless contoured ).

34. STEP 8: MOBILIZATION OF THE CHIN After completion of the osteotomy, the chin segment should be mobile. However , it may be necessary to finally mobilize it with a light tap and then rotate a small osteotome in the osteotomy line. The need for excessive force to mobilize the chin indicates that the osteotomy is not completely through both cortices or the inferior border of the mandible, which may lead to an unpredicted fracture of the lower border. When the genioplasty is combined with a bilateral sagittal split osteotomy of the mandible , it is preferable to perform the genioplasty after completing the sagittal split osteotomy .

35. At this stage, the mandible is still held in position by maxillomandibular fixation. Performing the genioplasty at this point allows the surgeon to evaluate the esthetics and, if necessary, make small positional changes to the chin to improve the appearance. Keeping the teeth in occlusion while performing the genioplasty provides the added advantage of supporting the mandible and reducing the forces on the rigid fixation screws that were recently placed.

36. STEP 9: ENGAGING THE POSITIONING WIRE Place a 26 gauge wire through the hole drilled in the osteotomized segment during marking, and attach a wire twister to it. This wire will be helpful both during the mobilization and in accurate repositioning of the chin.

37. STEP 10: FINAL MOBILIZATION OF THE CHIN SEGMENT Place a Howarth elevator behind the lingual cortex, and pull the chin forward by stretching the soft tissue (the suprahyoid muscles and periosteum ). Adequate mobilization of the segment will facilitate easy and accurate repositioning of the chin. Mobilizing the chin. A Howarth elevator is placed behind the chin segment while the chin is pulled forward by the positioning wire.

38. STEP 11: REFINEMENT OF THE OSTEOTOMY Check the posterior aspect of the osteotomized segment for any sharp or irregular edges , and remove the interferences using a large round vulcanite bur. Failure to smooth any irregularities will prevent accurate repositioning of the chin. Interferences are often found at the postero -lingual area of the mobilized segment and the soft tissue; the sublingual salivary gland, facial artery, mentalis nerve, and geniohyoid muscles should also be protected during removal of these bony interferences. All bony interferences should be removed and irregularities smoothed prior to repositioning. Special attention should be given to the posterior area of the chin segment .

39. Use the positioning wire and extraoral digital pressure to accurately reposition the chin according to the treatment plan. Although a golden rule in orthognathic surgery is “Never change your treatment plan on the operating table,” genioplasty may be the exception. The surgeon may use clinical judgment at the time of surgery to slightly alter the repositioning of the chin for a better esthetic result. The chin segment is placed in its planned position via the positioning wire.

40. When tri-cortical bone screw fixation is contemplated, countersink two holes in the buccal cortex approximately 8 mm on either side of the marked midline of the osteotomized segment. Position the countersunk holes at least 5 mm from the superior edge of the segment to accommodate the head of the screw. A countersink hole is placed to accommodate the head of the screw. Step 13: Counter sinking holes for tri-cortical screw fixation

41. Drill the holes, and place the bone screws while the assistant holds the chin in its planned position using the holding wire and digital pressure. Drill the holes into the center of the countersunk holes using a trocar to protect the soft tissue, and simultaneously guide the drill at an appropriate angle to engage all three cortices. Ensure that the screw is long enough to engage all three cortices. A trocar is used to place a tricortical screw to fixate the chin segment . At least two screws should be placed to secure the bone segment. STEP 14: PLACEMENT OF TRICORTICAL SCREWS A hole is drilled through all three cortices using a trocar to protect the soft tissue.

42. Use a prefabricated chin fixation plate, an X- or H-shaped bone plate, or two straight bone plates with two screws on either side of the osteotomy . The positioning wire and digital pressure help stabilize the chin segment in its planned position while the bone plates are bent to fit accurately and passively. Avoid damaging the roots of the incisors with the screws. It is recommended that fixation be placed on each side of the midline. STEP 15: BONE PLATE FIXATION AS AN ALTERNATIVE TO SCREW FIXATION As an alternative to tricortical screw fixation, bone plates may be used as rigid fixation.

43. Position the chin using extraoral digital pressure, check the position of the bone using a caliper , and use a prefabricated chin fixation plate or bend the appropriate plate to fit accurately and passively. Step 16: Anteroposterior reduction of the chin For setback procedures of the chin, bone plate fixation is the method of choice. In setback procedures, the use of a positioning wire is impractical.

44. When the chin is set back, the postero -lingual area often has a palpable step defect at the inferior border of the mandible, which may concern the patient. To contour this area, the osteotomized segment is pulled downward and forward, and the postero -lingual aspect of the chin segment is contoured. Protect the soft tissue at all times during this step. The medial aspect of the posterior area of the chin segment is removed to prevent a palpable step defect on the lower border of the mandible (arrow).

45. Anteroposterior reduction of the chin may result in flattening of the labiomental fold . The sharp anterior edge on the superior aspect may be contoured to counter this effect and enhance the depth of the labiomental fold and chin shape. The labiomental fold is enhanced by contouring the anterior edge on the superior aspect of the mandible.

46. Using a 701 fissure bur, drill reference holes recording the vertical dimensions of the chin . To maintain the symmetry of the chin, the reference marks should be made in the midline as well as approximately 15 mm lateral to the midline and the distances between them recorded. Place a bone plate while the assistant uses the positioning wire and an instrument wedged between the segments to maintain the required space between the bony segments. STEP 17: VERTICAL INCREASE OF THE CHIN

47. At least two screws should be placed superiorly and inferiorly to the osteotomy using an H- or X-shaped plate or two straight plates to secure the segment and maintain the vertical height. It is recommended that a bone graft be placed in the defect however, do not force the bone graft into the defect because doing so might displace or mobilize the chin segment. Vertical increase of the chin. The chin segment is held at the planned height with a positioning wire. Two bone plates are then placed to fixate the segment. Finally, the defect is grafted.

48. Drill reference marks recording the vertical dimensions of the chin. To maintain symmetry of the chin, place the marks in the midline and approximately 15 mm lateral to the midline, and record the distances between them. Perform the first osteotomy low enough to facilitate performing the second osteotomy from the superior aspect. Complete the lower osteotomy, and mobilize the chin. STEP 18: VERTICAL REDUCTION OF THE CHIN Vertical reduction of the chin. The lower osteotomy is performed first, and the planned amount of bone is then removed superiorly.

49. Mark the amount and shape of bone to be removed, and then complete the superior osteotomy. The shape of the ostectomized bone will influence the final anteroposterior position of the tip of the chin ; that is, if the ostectomy is wider anteriorly, the chin will rotate anteriorly, whereas an ostectomy that is wider posteriorly will rotate the chin posteriorly. Maintain as much soft tissue attachment to the chin as possible to ensure good blood supply to the repositioned bone and to reduce dead space. This will also yield a more predictable esthetic result.

50. Drill reference holes recording the dimensions of the chin. For lateral movement of the chin , the dental midline is marked on the superior aspect of the osteotomy line whereas the midline of the chin is marked on the inferior aspect. When correction of asymmetry requires vertical change as well, marks are placed lateral to the midline to record vertical dimensions on both the left and right sides. Step 19: Correction of asymmetry of the chin Lateral movement of the chin. The midline of the chin is marked below the osteotomy line and the facial midline above the osteotomy line. After mobilization of the chin, the chin segment is moved laterally until the lines coincide.

51. Large cants in the chin contour ( eg , in unilateral condylar hyperplasia or hypoplasia) may have to be corrected by a propeller osteotomy . The first osteotomy is performed superior and parallel to the occlusal plane or interpupillary plane. A second osteotomy is performed parallel to the lower border of the chin. Propeller osteotomy. A first osteotomy (1) is performed parallel to the interpupillary Line . A second osteotomy (2) is then performed parallel to the lower border of the chin.

52. The small, triangular segment is rotated 180 degrees while its muscle attachment is maintained. The inferior segment can now be secured by rigid fixation. The triangular segment, pedicled to the hyoid muscles, is rotated 180 degrees. The two segments are secured by rigid fixation.

53. STEP 20: ALTERING THE WIDTH OF THE CHIN Using a 701 fissure bur, drill reference marks recording the pre-surgical chin dimensions. WIDENING OR NARROWING THE POSTERIOR DIMENSION OF THE CHIN To widen the chin, perform a midline osteotomy through the buccal and lingual cortex, and complete the osteotomy with a small osteotome . Before the chin is mobilized, a four-hole straight plate fixation is done horizontally across the midline to the labial cortex of the chin. The chin can now be widened by using the bone plate as a hinge. Widening the posterior dimension of the chin. A midline osteotomy is performed through the chin segment after placement of a bone plate on the anterior surface. The plate is now used as a hinge, widening the posterior chin, and a small bone graft is placed in the midline defect.

54. To narrow the chin, perform a triangular midline ostectomy on the lingual aspect of the chin segment, again using the bone plate as a hinge. Once the desired shape of the chin has been achieved, additional fixation can be placed . Fixation should be placed on both sides of the midline osteotomy. Narrowing the posterior dimension of the chin. A bone plate is placed on the anterior surface of the chin and a triangular midline ostectomy performed. The segment is now bent medially to narrow the chin.

55. In widening the chin, a predetermined width can be achieved by performing a midline osteotomy and increasing the anterior width by moving the segments laterally. Secure the graft between the segments with a bone plate before fixation of the segments to the mandible. WIDENING OR NARROWING THE ANTERIOR DIMENSION OF THE CHIN After increasing the anterior width of the chin, a bone graft is placed between the segments. Widening the anterior dimension of the chin. An osteotomy is performed in the center of the chin segment.

56. To narrow the chin, a predetermined amount of bone is ostectomized from the mobilized segment. To simplify the removal of the ostectomized bone from the center of the chin, complete all the osteotomies before mobilizing the segments. Narrowing the anterior dimension of the chin. A midline ostectomy is performed in the center part of the chin. After removal of the ostectomized bone, the lateral segments are moved medially

57. STEP 21: SUTURING THE SUBMUCOSAL TISSUE Place an interrupted midline suture to accurately re-establish midline soft tissue alignment . Then use a continuous 3-0 chromic suture to re-approximate the periosteum and muscle. Accurate re-approximation of the mentalis muscle is of the utmost importance in maintaining the soft tissue contour. To achieve the best esthetic results, it is mandatory that the mentalis muscles be accurately re-approximated . Mucosal suturing should follow.

58. STEP 22: SUTURING THE MUCOSA Place a single midline 4-0 chromic suture to maintain lip symmetry . Use a continuous suture to secure the rest of the mucosa .

59. STEP 23: APPLYING A PRESSURE DRESSING Vertical and horizontal pressure is applied to the chin via a pressure bandage . Postoperative hematoma formation and swelling is limited by keeping the bandage in place for approximately 3 days.

60. KOLE’S PROCEDURE • The procedure is done for the correction of an anterior open bite . • Hofer (1936) demonstrated an anterior mandibular alveolar osteotomy to advance anterior teeth in correction of a mandibular dento -alveolar retrusion .

61. In 1959, Kole modified this procedure employing Hofer’s osteotomy generally use some form of bone graft in the alveolar defect if significant movement of the fragment is planned.

62. TENON TECHNIQUE Michelet and associated described this techenique in 1974 . A ‘U’ shaped monocortical osteotomy is created on the center of the symphysis. Lateral extensions are developed below the mental nerves, which connect to the superior aspects of the tenon corticotomy .

63. Full thickness osteotomies are completed on the lateral extensions and only through the lingual cortex on the superior aspect of the tenon . The resultant full thickness of bone behind the tenon facilitates the mortising of the tenon and lag-screw fixation

64. RECENT ADVANCES

65. HORIZONTAL FLIP PEDICLED GENIOPLASTY

66. BOX GENIOPLASTY

67. ADVANTAGES OF CHIN OSTEOTOMY Very versatile procedure ii. Corrects vertical problems iii. Stable over time iv. Improves submental length and cervicomental angle v. Advances genial-tongue-hyoid position, of benefit in sleep apnea

68. DISADVANTAGES OF CHIN OSTEOTOMY Requires osteotomy, adding risk from surgery and anesthesia ii. Vascular injury risk iii. Airway problem risk iv. Not easily reversible v. Increased expense for anesthesia , time and fixation materials when compared to implants

69. Augmentation using implants • Autologous Calvarial bone • Metals Corrosive High rate of bone erosion • Polymers – most commonly used

70. ADVANTAGES Quick procedure Requires minimal instrumentation Less dissection than osteotomy No risk to floor of mouth vasculature “ Easily” reversible procedure Wide selection of implant options Customizable DISADVANTAGES Capsular contracture Infection Bone resorption Dislodgement/malposition Soft tissue chin pad issues Vertical changes are difficult Lower lip retraction CHIN IMPLANTS

71. COMPLICATIONS • SOFT TISSUE i . Hematoma ii. Scar iii. Wound dehiscence iv. Cellulitis v. Draining fistula vi. Capsular contracture vii. Skin bunching/dimpling viii. Skin necrosis • NERVE Hypoesthesia/dysesthesia

72. MUSCLE a. Chin ptosis b. Mentalis muscle dysfunction c. Lower lip retraction • BONE/TOOTH ABSCESS a. Tooth root damage b. Mandibular bone resorption TECHNICAL a. Implant malposition b. Under-augmentation/over-augmentation

73. CONCLUSION • Genial procedure or genioplasty afford the surgeon the ability to make small but necessary changes or dramatic alteration in the overall form of the lower third of the face . • This can be accomplished with detailed pre-operative planning and application of good surgical technique.

74. REFERENCES Fonseca vol – III Johan P Reyneke – Essentials of orthognathic surgery Guyuron B, Michelow BJ and Willis L: Practical classification of chin deformities. Aesthetic Plast Surg 19: 257, 1995 Horizontal flip pedicled genioplasty for correction of asymmetric chin in adult unilateral temperomandibular joint ankylosis . Kiran Shrikrishna Garde ,  et al , Published  2011,The Journal of craniofacial surgery An alternative option to conventional genioplasty: box genioplasty,S . Colbert, T.E.Seah , V . Ilankovan , H . Bellis, DOI:https :// doi.org/10.1016/j.bjoms.2011.04.009 Oblique sagittal split sliding genioplasty : a new techniqueDavid P. Tauroa ,∗, Uday Kiran Uppadaba The Taulin’s Clinic, Centre for Craniomaxillofacial , Plastic & Reconstructive Surgery, Banglore , India Department of Oral & Maxillofacial Surgery, Sri Sai College of Dental Surgery, Vikarabad , BJOMS

75. THANKYOU!