1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56

CRANIOMAXILLOFACIAL DEFORMITIES/COSMETIC SURGERY

Influence of Osteotomy Design on Bilateral Mandibular Ramus Sagittal Split Osteotomy Larry M. Wolford, DMD

Q5 Q2

--Ó 2015 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg -:1-11, 2015 The mandibular ramus sagittal split osteotomy is the most popular procedure for repositioning the mandible for orthognathic surgery. Compared with other techniques, such as a vertical ramus osteotomy or inverted L-osteotomy, the sagittal split osteotomy provides a better bony interface to supplement healing and allows easier adaption of rigid fixation. Since the introduction of the intraoral sagittal split osteotomy by Trauner and Obwegeser in 1955,1-3 many modifications of this procedure have been performed. I have been requested to comment on the report by Verweij et al,4 titled ‘ The Angled Osteotomy Design Aimed to Influence the Lingual Fracture Line in Bilateral Sagittal Split Osteotomy: A Human Cadaveric Study.’’ Historically, the ‘ angled osteotomy’’ design was introduced and used for many years by Hugo Obwegeser and others.1-3 Verweij et al4 conducted a study on 28 cadaveric dentulous mandibles using 2 mandibular ramus sagittal split osteotomy modifications: the ‘ conventional’’ and the ‘ angled osteotomy’’ design. The ‘ conventional’’ osteotomy design was based on modifications by Dal Pont5 and Hunsuck.6 The design includes the following steps: Step 1. A medial monocortical osteotomy above the lingula and extending posterior to it Step 2. A cut down the ascending ramus stopping distal to the second molar Step 3. A vertical monocortical osteotomy from distal of the second molar perpendicular to the inferior border of the mandible, with the cut extending through the lingual cortex of the inferior border The authors’ ‘ angled osteotomy’’ technique uses the same basic design for steps 1 and 2; however, for step 3, the buccal monocortical osteotomy was angled

inferoposterior toward the masseteric tubercles with a cut through the lingual cortex of the inferior border. The basic difference in these 2 designs is that the ‘ angled osteotomy’’ eliminates a significant length of the lingual cortical bone fracture required to complete the sagittal split, thus reducing the amount of torque force necessary to complete the separation of the proximal and distal segments and resulting in a lower rate of unfavorable fractures. Also, the involvement (entrapment) of the inferior alveolar nerve (IAN) is less in the proximal segment such as commonly occurs with the ‘ conventional’’ osteotomy in which the IAN can be incased within the lingual cortical bone attached to the proximal segment. It is sometimes quite difficult to release the IAN from the proximal segment and can lead to nerve injury during the release process. Because the ‘ angled osteotomy’’ lingual cortical cut can be located posterior to the lingula and inferior alveolar nerve canal, the lingual fracture commonly occurs more posteriorly, resulting in less risk of damage to the IAN compared with the ‘ conventional’’ technique. The present study shows the advantages of the ‘ angled osteotomy’’ compared with the ‘ conventional’’ technique in 2 specific areas: 1) decreased occurrence of an unfavorable fracture and 2) decreased entrapment and potential injury of the IAN. The ‘‘conventional’’ osteotomy has the following unfavorable features: 1. The amount of mandibular advancement is limited but not as significant as with the ‘‘angled osteotomy’’ design. 2. Splitting the mandible requires more force compared with the ‘‘angled osteotomy.’’ 3. It results in a greater risk of unfavorable splits, usually involving fracture of the buccal cortex.

Clinical Professor, Department of Oral and Maxillofacial Surgery, Texas A&M University Health Science Center, Baylor College of

Received March 15 2015 Accepted March 15 2015

Dentistry, Dallas, TX.

Ó 2015 American Association of Oral and Maxillofacial Surgeons

Address correspondence and reprint requests to Dr Wolford:

0278-2391/15/00273-6

Department of Oral and Maxillofacial Surgery, Texas A&M University

http://dx.doi.org/10.1016/j.joms.2015.03.023

Health Science Center, Baylor College of Dentistry, Dallas, TX 75246; e-mail: [email protected]

1 SCO 5.2.0 DTD  YJOMS56710_proof  16 April 2015  4:32 pm  CE BD

57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112

113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168

2

INFLUENCE OF OSTEOTOMY DESIGN MANDIBULAR RAMUS SAGITTAL SPLIT OSTEOTOMY

4. The risk of IAN involvement and injury is greater. 5. It is difficult to control the position of the proximal segment and keep it in its original anatomic position, because the segment will tend to rotate upward and forward with no positional reference, particularly with significant mandibular advancement. 6. Notching will occur at the inferior border of the mandible with any significant mandibular advancement because the lingual cortex is absent from the distal segment, creating a clinically evident unesthetic soft tissue and bony defect. 7. It can be difficult to perform concomitant temporomandibular joint (TMJ) and orthognathic surgery secondary to the complexity of controlling the condyle and proximal segment positions. The ‘‘angled osteotomy’’ has the following unfavorable features: 1. The amount of mandibular advancement is significantly limited by the osteotomy design. 2. It can be difficult to control the position of the proximal segment and keep it in its original anatomic position, because it will tend to rotate upward and forward with no positional reference, particularly with significant mandibular advancement. 3. Notching will occur at the inferior border of the mandible with any significant mandibular advancement, leaving a noticeable esthetic soft tissue and bony defect, although Verweij et al4 stated that the masseter muscle will hide the defect. 4. It can be more challenging to apply rigid fixation. If rigid fixation is applied intraorally, the screws must be inserted at an angle (instead of perpendicular to the bone). This can result in a shift between the segments, which will affect the mandibular position and occlusion. 5. Small extraoral incisions might be required to accommodate a transcutaneous trocar for placement of bone screws and/or plates to facilitate screw insertion perpendicular to the bone. 6. In the ramus area of the ‘‘angled osteotomy,’’ the IAN bundle is closer to the buccal cortex and further away from the lingual cortex. This increases the risk of IAN injury using conventional cutting instruments such as the bone saw or drill bit. Verweij et al4 used a piezoelectric cutting instrument, which might decrease the injury risk. 7. It can be difficult to perform concomitant TMJ and orthognathic surgery secondary to the complexity of controlling the condyle and proximal segment positions. For mandibular setbacks, both techniques will require bony recontouring (removal) of the lingual

cortex on the medial side of the proximal segment above the medial cut, at the inferior and posterior borders, and bone removal from the anterior aspect of the proximal segment to eliminate bony interferences and provide unimpeded approximation of the proximal and distal segments. For larger setbacks, removal of bone from the anterior aspect of the ascending ramus of the proximal segment might be required, such that the second molars do not become ‘‘buried’’ medial and posterior to the anterior border of the mandibular ramus. The limitations of the ‘‘conventional’’ and ‘‘angled osteotomy’’ techniques indicate the need to review another mandibular sagittal split osteotomy design that might have advantages compared with those included in the study by Verweij et al.4

Wolford Inferior Border Osteotomy Modification of the Mandibular Ramus Sagittal Split Procedure The Wolford inferior border osteotomy modification of the sagittal split procedure might address a number of the unfavorable features associated with the ‘‘conventional’’ and the ‘‘angled osteotomy’’ designs. This technique incorporates an inferior border osteotomy into the sagittal split design and provides a method to reposition the mandible with an effective method for easier splitting, greater advancement capabilities, decreased IAN involvement, positional control of the condyle and proximal segment, and easy application of rigid fixation.7-9 A description of the technique follows: 1. The medial monocortical osteotomy is performed through the lingual cortex just above the lingula, extending posterior to the lingula and mandibular foramen, using a short Lindenman bur. 2. After initiating the vertical ramus cut with a no. 701 fissure bur, a thin bladed reciprocating saw is used to perform the osteotomy down the ascending ramus, adjacent to the buccal cortex and stopping just distal to the second molar (Fig 1A). 3. A horizontal monocortical osteotomy is made with a no. 701 fissure bur, directed perpendicular to the buccal cortex, 8 to 10 mm below the alveolar crest (Fig 1A, green arrow; Fig 2A), and is extended anteriorly 8 mm more than the amount of intended mandibular advancement (Fig 1A, red arrow). This cut subsequently creates a bony ledge on the distal segment, which provides a vertical stop to control the position of the proximal segment and an area to apply a bone plate. For counterclockwise rotation of the mandible, the buccal

SCO 5.2.0 DTD  YJOMS56710_proof  16 April 2015  4:32 pm  CE BD

Q1

169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224

3

225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280

print & web 4C=FPO

LARRY M. WOLFORD

FIGURE 1. A, Outline of the Wolford modification of the mandibular ramus sagittal split osteotomy. The green arrow indicates the horizontal cut 8 to 10 mm below the alveolar bone crest; red arrow, horizontal osteotomy extended 8 mm longer than the amount of mandibular advancement to provide a bony interface between the proximal and distal segments. B, Medial side of ramus showing position of the medial horizontal cut and the fracture line. (Fig 1 continued on next page.) Larry M. Wolford. Influence of Osteotomy Design Mandibular Ramus Sagittal Split Osteotomy. J Oral Maxillofac Surg 2015.

SCO 5.2.0 DTD  YJOMS56710_proof  16 April 2015  4:32 pm  CE BD

281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336

INFLUENCE OF OSTEOTOMY DESIGN MANDIBULAR RAMUS SAGITTAL SPLIT OSTEOTOMY

print & web 4C=FPO

337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392

4

FIGURE 1 (cont’d). C, The mandible has been advanced. The red circle indicates the bony interface between the proximal and distal segments; the red arrow points to the inferior border cortex remaining attached to the distal segment; and the green arrow indicates the direction of gentle upward pressure to seat the condyle into the fossa. D, Application of a 6-hole Z-plate to stabilize the segments. Larry M. Wolford. Influence of Osteotomy Design Mandibular Ramus Sagittal Split Osteotomy. J Oral Maxillofac Surg 2015.

SCO 5.2.0 DTD  YJOMS56710_proof  16 April 2015  4:32 pm  CE BD

393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448

5

449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504

print & web 4C=FPO

LARRY M. WOLFORD

FIGURE 2. A, Transection through the distal portion of the first molar. The green arrow indicates horizontal bone cut, perpendicular to buccal cortex, and at a level 8 to 10 mm below the alveolar bone crest. The red arrow indicates the position of the inferior border osteotomy. (Fig 2 continued on next page.) Larry M. Wolford. Influence of Osteotomy Design Mandibular Ramus Sagittal Split Osteotomy. J Oral Maxillofac Surg 2015.

horizontal osteotomy can be curved to facilitate better approximation of the segments. 4. The posterior aspect of the horizontal cut is connected to the anterior aspect of the ascending ramus cut with a no. 701 fissure bur. 5. A vertical cut is made through the buccal cortex from the anterior aspect of the horizontal cut, directed perpendicular to the inferior border of the mandible using a no. 703 fissure bur (Fig 1A). The inferior border is only cut halfway through; not completely through such as in the ‘‘conventional’’ or ‘‘angled osteotomy’’ designs. 6. The inferior border osteotomy is performed with specially designed reciprocating inferior border osteotomy saw blades (Figs 2, 3) manufactured by 2 companies: Stryker, Inc., Kalamazoo, MI, and Hall Surgical Division of Zimmer, Largo, FL. The osteotomy is initiated at the anterior

vertical buccal cortical osteotomy and directed posterior to merge on the lingual side at the posterior aspect of the gonial notch (Figs 2B, 3C,D). This inferior border osteotomy significantly decreases the torque forces required for separation of the proximal and distal segments, reducing the risk of an unfavorable fracture, and provides a more predictable path of lingual fracture to occur similar to the vertical fracture seen in the authors’ ‘ angled osteotomy,’’ decreasing involvement of the IAN (Fig 1B). With the split at the inferior border of the mandible, as the mandible is advanced, the lingual cortex remains in place on the distal segment (Fig 1C, red arrow), eliminating the notching that commonly occurs with the ‘ conventional’’ or ‘ angled osteotomy’’ design, particularly for larger advancements.

SCO 5.2.0 DTD  YJOMS56710_proof  16 April 2015  4:32 pm  CE BD

505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560

INFLUENCE OF OSTEOTOMY DESIGN MANDIBULAR RAMUS SAGITTAL SPLIT OSTEOTOMY

print & web 4C=FPO

561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616

6

FIGURE 2 (cont’d). B, View of the right inferior border of the mandible. The orange arrow points to the inferior border of the mandible; blue arrow, the angle of the mandible; green arrow, the inferior border saw initiating the osteotomy anteriorly adjacent to the buccal vertical osteotomy (red arrow). Larry M. Wolford. Influence of Osteotomy Design Mandibular Ramus Sagittal Split Osteotomy. J Oral Maxillofac Surg 2015.

SCO 5.2.0 DTD  YJOMS56710_proof  16 April 2015  4:32 pm  CE BD

617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672

7

673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728

print & web 4C=FPO

LARRY M. WOLFORD

FIGURE 3. The inferior border saw blades are designed for the A, right side and B, left side. C, The inferior border osteotomy is initiated anteriorly adjacent to the vertical buccal osteotomy. The vertical shaft of the blade is positioned against the lateral cortical plate of the mandibular body. The blade has a vertical stop and can only penetrate about 5 mm into the inferior border. D, The saw blade is seated in the osteotomy and directed toward the lingual plate at the posterior aspect of the gonial notch. Larry M. Wolford. Influence of Osteotomy Design Mandibular Ramus Sagittal Split Osteotomy. J Oral Maxillofac Surg 2015.

7. The proximal and distal segments are completely separated using the Smith angled separating instruments and a 3-prong Smith spreader (W. Lorenz Surgical, Jacksonville, FL). No chisels or mallets are generally required in executing the sagittal split osteotomies, thereby minimizing the chances of unfavorable fracture or inadvertent nerve damage during instrumentation. In the unusual occurrence of the IAN remaining adherent to the proximal segment, it is usually related to the cortical bone of the canal incasing the nerve. The IAN should be carefully removed from the segment, which sometimes requires removal of the residual canal bone. 8. If third molars are present, they should be removed, whether impacted or erupted, after the split has been completed.

9. The medial side of the proximal segment is smoothed with a reciprocating bone file, removing the remnants of the medullary bone and IAN canal to minimize subsequent injury to the IAN when the segments are realigned. 10. For mandibular setback, the lingual cortical bone on the proximal segment above the medial osteotomy and at the inferior border/ angle/posterior border usually requires removal for the segments to be passively approximated. This bone can be removed with a reciprocating saw or bone file or bone bur (Fig 4A). 11. The excessive overlapping bone at the anterior aspect of the proximal segment relative to the distal segment is removed. Any other areas of bony interference are removed (Fig 4B). For large mandibular setback, bone removal might

SCO 5.2.0 DTD  YJOMS56710_proof  16 April 2015  4:32 pm  CE BD

729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784

INFLUENCE OF OSTEOTOMY DESIGN MANDIBULAR RAMUS SAGITTAL SPLIT OSTEOTOMY

print & web 4C=FPO

785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840

8

FIGURE 4. A, Medial side of the ramus illustrating where bone will need to be removed for mandibular setbacks. Bone will need to be removed above the medial horizontal cut and at the inferior and posterior borders of the ramus for the segments to sit passively together. (Fig 4 continued on next page.) Larry M. Wolford. Influence of Osteotomy Design Mandibular Ramus Sagittal Split Osteotomy. J Oral Maxillofac Surg 2015.

12. 13.

14.

15.

be required from the anterior ramus of the proximal segment to ensure that the second molars are not ‘‘buried’’ posterior to the anterior aspect of the ramus. The mandible is mobilized and intermaxillary fixation (IMF) applied. The anterior aspect of the proximal segment is then positioned beneath the ledge of the distal segment (Fig 1C, red circle). This point of the fulcrum allows easy setting of the condyle into the fossa, with gentle pressure applied vertically at the angle of the mandible (Fig 1C, green arrow). Rigid fixation is applied. A 4-hole or 6-hole Z-plate can be used (Fig 1D); however, the surgeon has several options to provide rigid fixation. The surgical areas are thoroughly irrigated and incisions closed, and the IMF is removed.

With this modification, the proximal segment is positionally controlled by the interface between the proximal segment and the ledge of the distal segment. These segments can then be stabilized with a bone plate or bone screws. In prognathic cases, the bone will need to be removed from the anterior aspect of the proximal segment and along the anterior superior border of the proximal segment up toward the ascending ramus, for it to fit appropriately beneath the ledge of the distal segment (Fig 4). Whether the mandible is set posteriorly or advanced 5 or 20 mm, it can usually be stabilized with a single relatively small bone plate positioned at the interface of the proximal segment with the ledge of the distal segment (Fig 1D). One advantage of the inferior border osteotomy modification is that the amount of torque force necessary to complete the sagittal split is probably similar to that of the ‘‘angled osteotomy’’ in contrast to the

SCO 5.2.0 DTD  YJOMS56710_proof  16 April 2015  4:32 pm  CE BD

Q4

841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896

9

897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952

print & web 4C=FPO

LARRY M. WOLFORD

FIGURE 4 (cont’d). B, On the lateral side, the bone will require removal from the proximal segment at the anterior aspect and interface at the posterior aspect of the ledge in the distal segment. For large setbacks, bone removal might be required from the anterior aspect of the ascending ramus such that the second molars are not ‘‘buried’’ posterior to the ramus. Larry M. Wolford. Influence of Osteotomy Design Mandibular Ramus Sagittal Split Osteotomy. J Oral Maxillofac Surg 2015.

greater torque force required with the ‘‘conventional’’ design. In addition, the lingual fracture is the same as that for the ‘‘angled osteotomy.’’ This has been supported by a recent study by Bockmann et al.10 They performed an in vitro comparison of sagittal split osteotomy on 35 mandibles using the traditional Obwegeser/Dal Pont design with 35 sides without and 35 sides with the inferior border osteotomy. The torque used to split the mandibles was measured, and the fracture line position on the medial aspect of the mandibles was recorded. The average torque for the original technique without the inferior border osteotomy was 1.38 Newton-meters (Nm) or 1.02 foot pound force (ft-lbf), with the lingual fracture line along the mandibular canal. In contrast, the average torque required to split the mandible incorporating the inferior border cut was 1.02 Nm or 0.75 ft-lbf (P < .001), with the fracture line more parallel to the posterior ramus of the mandible, seen similarly in the ‘‘angled osteotomy’’ group study by Verweij et al.4 Bockmann et al10 concluded that adding the inferior border osteotomy to the sagittal split osteotomy resulted in less torque to split the mandible, and the fracture line was more predictable.

Presence or Absence of Third Molars Our study11 evaluated the outcomes of mandibular sagittal split osteotomies in 2 patient groups relative to the presence or absence of third molars. Group 1 consisted of 250 sagittal split osteotomies with concomitant removal of the impacted third molars at surgery. Group 2 consisted of 250 sagittal split osteotomies with the absence of third molars, using the Wolford modified sagittal split technique. The surgical procedure and rigid fixation were performed the same for both groups. The occurrence of unfavorable splits was 3.2% in group 1 and 1.2% in group 2, with no statistically significant difference between the 2 groups. In group 1, unfavorable splits occurred in all adolescents, with 7 of the 8 fractures occurring at the posterior aspect of the distal segment through the third molar socket. This type of fracture is basically not an issue with the current method of rigid fixation (Fig 1D). Three fractures occurred in group 2, all involving fracture of the buccal cortex of the proximal segment. However, the sagittal splits were completed, the fractured buccal segment was restabilized to the posterior part of the proximal segment with the

SCO 5.2.0 DTD  YJOMS56710_proof  16 April 2015  4:32 pm  CE BD

953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008

1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064

10

INFLUENCE OF OSTEOTOMY DESIGN MANDIBULAR RAMUS SAGITTAL SPLIT OSTEOTOMY

bone plate, and the proximal and distal segments stabilized in the same manner as did the patients with favorable splits. The outcomes were the same for all patients relative to stability, whether favorable or unfavorable splits had occurred.

Neurosensory Evaluation of IAN Our study12 evaluated the neurosensory outcomes on the IAN with sagittal split osteotomies using somatosensory evoked potential (SEP) computer analysis and conventional 2-point discrimination. A total of 40 patients were evaluated who had undergone bilateral mandibular ramus sagittal split osteotomies using the Wolford modification. All subjects were evaluated postoperatively at 2 weeks, 1 and 6 months, and 1 year. At 2 weeks after surgery, virtually all the patients had abnormal IAN SEP recordings. However, at 3 months, 80% of the patients had a complete return of sensation. At 1 year, 100% of the patients had a full return of sensation. The study demonstrated that the Wolford modification, performed properly and carefully, should have no long-term deficit to the IAN. Another of our studies13 involved intraoperative SEP evaluations of 10 patients undergoing bilateral sagittal split osteotomies using the Wolford sagittal split modification. The anesthesia technique was standardized for all patients. The SEPs were recorded in surgery to identify where a potential IAN injury could occur during the operative procedure, including 1) before any bone cuts, 2) medial retraction for access for the medial bone cut, 3) cutting and splitting of the mandible, and 4) immediately after rigid fixation was applied. The greatest effect on the SEPs was medial retraction of the IAN while performing the medial cut on the ramus. No significant nerve injury was noted through the rest of the procedure. The advantages to the Wolford inferior border osteotomy modification include the following: 1. A better bony interface between the segments enhancing healing 2. Simultaneous removal of impacted or erupted third molars, if present, without a significant risk of an unfavorable split or fracture 3. Accurate control of condylar position and of the proximal segment 4. No postoperative IMF is required, providing better oral hygiene, speech, and nutrition 5. The mandible can be advanced a significantly greater distance than with the ‘‘conventional’’ or ‘‘angled osteotomy’’ designs 6. Ease of application of rigid fixation intraorally 7. TMJ surgery can be performed concomitantly with the sagittal split osteotomy14-21 8. Less risk of damage to the IAN12,13

9. Facilitates counterclockwise advancement rotation of the maxillomandibular complex22-25 The disadvantages of this technique are as follows: 1. The added expense of purchasing the inferior border saws 2. The learning curve required to master the inferior border osteotomy 3. A longer surgical time required to treat mandibular prognathism compared with the vertical ramus or inverted L osteotomies The mandibular ramus sagittal split osteotomy is a very good procedure for correcting mandibular hypoplasia (retrognathism), mandibular prognathism, and most asymmetries. The advantages of being able to correct the jaw alignment, having an excellent bony interface to promote primary bone healing, the easy application of rigid fixation for stability, having accurate control of the condylar position, and the benefits of no postoperative IMF make the sagittal split ramus osteotomy the preferred osteotomy technique compared with the others available. The Wolford inferior border osteotomy technique also facilitates performing predictable redo mandibular sagittal split osteotomies on patients requiring repeat orthognathic surgery. In conclusion, Verweij et al4 have demonstrated the advantages of the ‘‘angled osteotomy’’ over the ‘‘conventional’’ design, but both techniques have limitations relative to the amount of mandibular advancement, the unfavorable aesthetic changes that can occur by the greater difficulties controlling the position of the proximal segment, and notching at the inferior border with larger mandibular advancement. The advantages of the inferior border osteotomy modification of the mandibular ramus sagittal split osteotomy have been presented. It would be interesting if Verweij et al4 could perform the same basic study they have so nicely performed with the ‘‘conventional’’ and ‘‘angled osteotomy’’ designs but also including the inferior border osteotomy technique.

References 1. Trauner R, Obwegeser H: Zur Operationstechnik bei der progenie und anderen unterkieferanomalien. Dtsch Zahn Mund Kieferhlkd 23:1, 1955 2. Trauner R, Obwegeser H: The surgical correction of mandibular prognathism and retrognathia with consideration of genioplasty. 1. Surgical procedures to correct mandibular prognathism and reshaping of the chin. Oral Surg Oral Med Oral Pathol 10:677, 1957 3. Obwegeser HL: The sagittal splitting of the mandible procedure, in Tessier P, Obwegeser HL (eds): Mandibular Growth Anomalies. Berlin, Springer-Verlag, 2001, pp 359–384 4. Verweij JP, Mensink G, Houppermans P, Van Merkesteyn R: The angled osteotomy design aimed to influence the lingual fracture

SCO 5.2.0 DTD  YJOMS56710_proof  16 April 2015  4:32 pm  CE BD

1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120

11

LARRY M. WOLFORD

1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150

Q3

5. 6. 7.

8.

9.

10.

11.

12.

13.

14.

15.

line in bilateral sagittal split osteotomy: A human cadaveric study. J Oral Maxillofac Surg 2015 Mar 21. Dal Pont G: Retromolar osteotomy for the correction of prognathism. J Oral Surg 19:42, 1961 Hunsuck EE: A modified intraoral sagittal splitting technique for correction of mandibular prognathism. J Oral Surg 26:250, 1968 Wolford LM, Bennett MA, Rafferty CG: Modification of the mandibular ramus sagittal split osteotomy. Oral Surg Oral Med Oral Pathol 64:146, 1987 Wolford LM, Davis WM Jr: The mandibular inferior border split: A modification in the sagittal split osteotomy. J Oral Maxillofac Surg 48:92, 1990 Wolford LM: The sagittal split ramus osteotomy as the preferred treatment for mandibular prognathism. J Oral Maxillofac Surg 58:310, 2000 Bockmann R, Schon P, Neuking K, et al: In vitro comparison of the sagittal split osteotomy with and without inferior border osteotomy. J Oral Maxillofac Surg 73:316, 2015 Mehra P, Castro V, Freitas RZ, Wolford LM: Complications of the mandibular sagittal split ramus osteotomy associated with the presence or absence of third molars. J Oral Maxillofac Surg 59: 854, 2001 Jones DL, Wolford LM, Hartog JM: Comparison of methods to assess neurosensory alterations following orthognathic surgery. Int J Adult Orthodon Orthognath Surg 5:35, 1990 Jones DL, Wolford LM: Intraoperative recording of trigeminal evoked potentials during orthognathic surgery. Int J Adult Orthodon Orthognath Surg 5:167, 1990 Wolford LM, Cardenas L: Idiopathic condylar resorption: Diagnosis, treatment protocol, and outcomes. Am J Orthod Dentofacial Orthop 116:667, 1999 Wolford LM: Idiopathic condylar resorption of the temporomandibular joint in teenage girls (cheerleaders syndrome). Proc (Bayl Univ Med Cent) 14:246, 2001

16. Wolford LM, Dhameja A: Planning for combined TMJ arthroplasty and orthognathic surgery. Atlas Oral Maxillofac Surg Clin North Am 19:243, 2011 17. Wolford LM, Cottrell DA, Karras SC: Mitek mini anchor in maxillofacial surgery, in SMST-94 First International Conference on Shape Memory and Superelastic Technologies. Monterey, CA, MIAS, 1995, pp 477–482 18. Mehra P, Wolford LM: The Mitek mini anchor for TMJ disc repositioning: Surgical technique and results. Int J Oral Maxillofac Surg 30:497, 2001 19. Wolford LM, Karras S, Mehra P: Concomitant temporomandibular joint and orthognathic surgery: A preliminary report. J Oral Maxillofac Surg 60:356, 2002 20. Wolford LM: Concomitant temporomandibular joint and orthognathic surgery. J Oral Maxillofac Surg 61:1198, 2003 21. Wolford LM, Cassano DS, Gonc¸alves JR. Common TMJ disorders: Orthodontic and surgical management, in McNamara JA, Kapila SD (eds): Temporomandibular Disorders and Orofacial Pain: Separating Controversy from Consensus. Ann Arbor, MI: Department of Orthodontics and Pediatric Dentistry, University of Michigan School of Medicine; 2009, pp 159–198. 22. Gonc¸alves JR, Cassano DS, Wolford LM, et al: Postsurgical stability of counterclockwise maxillomandibular advancement surgery: Affect of articular disc repositioning. J Oral Maxillofac Surg 66:724, 1999 23. Wolford LM, Chemello PD, Hilliard F: Occlusal plane alteration in orthognathic surgery—Part I: Effects on function and esthetics. Am J Orthod Dentofacial Orthop 106:304, 1994 24. Chemello PD, Wolford LM, Buschang PH: Occlusal plane alteration in orthognathic surgery—Part II: Long-term stability of results. Am J Orthod Dentofac Orthop 106:434, 1994 25. Wolford LM, Chemello PD, Hilliard FW: Occlusal plane alteration in orthognathic surgery. J Oral Maxillofac Surg 51:730, 1993

SCO 5.2.0 DTD  YJOMS56710_proof  16 April 2015  4:32 pm  CE BD

1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180

Influence of Osteotomy Design on Bilateral Mandibular Ramus Sagittal Split Osteotomy.

Influence of Osteotomy Design on Bilateral Mandibular Ramus Sagittal Split Osteotomy. - PDF Download Free
2MB Sizes 0 Downloads 9 Views