J Oral Maxillofac Surg59:237-240, 2001

A Modified Mandibular Ramus Osteotomyfor Orthognathic Surgery

William Weber, DMD*

Several procedures have been described for correc-tion of orthognathic deformities of the mandible. Cur-rently, the bilateral sagittal split osteotomy (BSSO)maintains its popularity because of its versatility andits amenability to rigid fixation techniques. The distalsegment of the mandible can be repositioned in allplanes of space, and the bony interface along theosteotomy results in predictable healing. However,there are well-known disadvantages to the procedure,which include neurosensory disturbance,1-9 condylardisplacement,10-13 and unfavorable splits.14-17

The vertical oblique osteotomy can be used in casesof horizontal mandibular excess. It is not as easilyfixed with plates or screws and therefore requires aperiod of maxillomandibular fixation, which most pa-tients prefer to avoid if possible. Difficulty in control-ling the proximal segment,18 delayed or nonunion,and condylar displacement and relapse19-24 are otherdrawbacks of the procedure. The inverted “L” osteot-omy has also been used to retrude the mandible.Generally, a period of 6 to 8 weeks of maxilloman-dibular fixation (MMF) is required with this proce-dure. Paulus and Steinhauser25 described the place-ment of 2 lag screws as a rigid fixation technique forthe inverted “L” osteotomy and noted technical diffi-culty placing any greater number. Van Sickels et al26

described a method for plating an inverted “L” osteot-omy that has a beveled medial cut to produce greaterbony overlap. Their technique also involved the useof a condylar positioning plate and was used formandibular setbacks only. The condylar positioningplate was used because of concerns regarding condy-lar torque with rigid fixation.

This report describes a modified ramus osteotomythat is relatively easy and predictable to perform. Itcan be used in mandibular excess or deficiency cases,is amenable to the application of rigid fixation, places

the neurovascular bundle at less risk than the BSSO,and does not tend to cause large condylar deflections.The use of a condylar positioning plate or device hasnot been necessary.

Procedure

The location of the mandibular foramen and canalare noted and traced on the panoramic and lateralcephalometric radiographs. The osteotomies are thentraced, and the predicted movements are simulated toevaluate the relative segment positions at surgery.Measurements from the model surgery and predictiontracings are correlated.

The dissection is the same as for the conventionalBSSO and includes exposure of the lateral aspect ofthe ramus and posterior border inferiorly. The cutbasically resembles the inverted “L” but is extremelysagittal or beveled in nature. First, the lateral cut ismade with an extreme bevel. It proceeds from infe-rior to superior just anterior to the antilingula ormidramus point (Fig 1). A fissure bur or sagittal sawcan be used to mark the cut before making the os-teotomy. The angulation of the cutting instrument issuch that the cut will exit just at the medial aspect ofthe posterior border (Fig 2). A Bauer retractor isplaced into the sigmoid notch, and a small channelretractor is placed around the inferior aspect of theposterior border. The cut is made with a reciprocat-ing saw beginning inferiorly and proceeding superi-orly, with the saw blade facing upward. It has anextreme bevel, which is easily accomplished giventhe access provided by the dissection. The cut shouldbe made full thickness in the first pass, making surethat the exit point is just medial to the posteriorborder. It is brought superiorly to within 1 to 2 mm ofthe antilingula. The tip of the saw blade is tippedupward to complete the cut posteriorly.

To make the medial cut, the location of the man-dibular foramen is verified, and the cut is begun ap-proximately 10 mm above it, using a reciprocatingsaw. The medial cut is beveled, proceeding inferiorlyas the saw passes into the ramus from medial tolateral. The location of the foramen divides the cutinto posterior and anterior halves. The posterior halfof the cut is carried back to just short of the posteriorborder and is monocortical only (Fig 2). From theforamen forward, the medial cut is carried completely

*Oral and Maxillo-Facial Surgery Associates of Manhattan, P.C.;

Attending, Department of Oral and Maxillofacial Surgery, Mount

Sinai Medical Center, New York, NY.

Address correspondence and reprint requests to Dr Weber: Oral

and Maxillofacial Surgery Associates of Manhattan, P.C., 41 E 57th

St, Suite 1204, New York, NY 10022; e-mail: omaxillo@aol.com.

© 2001 American Association of Oral and Maxillofacial Surgeons

0278-2391/01/5902-0023$35.00/0

doi:10.1053/joms.2001.20510

237

through the ramus. The saw blade exits on the lateralcortex at the level of the mandibular foramen andjoins the lateral cut just below and anterior to theantilingula (Fig 1). Retraction over the coronoid isaccomplished with a notched right angle retractor. Aself-retaining coronoid retractor should not be used atthis point, because inadvertent coronoid fracture canoccur before the osteotomy is completed.

The only remaining area of bone attachment willbe approximately 1 cm2 posterior to the mandibu-lar foramen (Fig 2). The osteotomy is completedwith a thin, flat osteotome that is placed into themedial cut and run posteriorly with a few gentletaps of a mallet (Fig 3).

After separation of the segments, the osteotomy isvisualized, and it is ascertained that the neurovascularbundle is intact and fully in the distal segment (Fig 4).The patient is placed into MMF, and the condylarfragment is seated centrally in the fossa using gentleupward pressure from the inferior border. This isusually accomplished with a curved Freer elevatorand manual manipulation. Intersegmental bony pre-

maturities are reduced with an oval-shaped bur. Fix-ation usually consists of miniplates with monocorticalscrews inferiorly and sometimes one bicortical posi-tional screw or miniplate superiorly across the hori-zontal cut. Note that the screws for the plate span thecanal, minimizing the chance for injury to the neuro-vascular bundle (Figs 5, 6). Depending on the direc-tion of movement of the distal segment, the protrud-ing bony step that results at the anterior border of theramus will be either the coronoid process on theproximal segment (setback) or the external obliqueridge on the distal segment (advancement). The step

FIGURE 1. The vertical lateral cut joins the beveled bicortical portionof the medial cut at or just below and anterior to the antilingula ormidramus point.

FIGURE 2.Medial view of the osteotomy. The shaded area indicatesthe area remaining to be split after the saw cuts have been made.

FIGURE 3. A thin, flat osteotome easily completes the osteotomy.

FIGURE 4. Completed osteotomy showing bony interface and pres-ervation of neurovascular bundle.

238 MODIFIED MANDIBULAR RAMUS OSTEOTOMY

is flattened with an oval-shaped bur after placementof fixation. No postoperative MMF is placed.

Discussion

The osteotomy described has proved to be quickand easy to perform. It has been used to set back themandible on 16 sides in 9 patients and to advance themandible on 5 sides in 3 patients. Rotation with nonet anteroposterior movement occurred on 1 side in1 patient (Table 1). The initial results have been ex-cellent. However, the use of this osteotomy has beenlimited in cases of mandibular advancement to move-ments of 5 to 6 mm. The amount of bony interfacetends to be reduced considerably in advancements oflarger magnitude. However, 1 bimaxillary case with a7-mm mandibular advancement on one side was donein which the distal segment moved also superiorly,allowing the proximal segment to rotate counter-clockwise and regain some bony overlap. Because ofthe location of the cuts, the presence of third molarshas no influence on the surgery.

Rigid fixation has been very easy to apply. Thesegments tend to lie relatively flat relative to oneanother, and any bony interference or premature con-tact within the osteotomy has been easily recon-toured by using an oval-shaped bur. Large deflectionsof the proximal segment do not occur because of thebeveled nature of the cuts. There has been no signif-icant relapse in the early period (first 4 months).

There have been no cases of neurosensory distur-bance attributable to the osteotomy. The only neuro-logic problems encountered were in one case of inap-propriate fixation screw placement and one of mentalnerve retraction during genioplasty. The neurovascularbundle has not been visualized in the osteotomy in anyof the cases. In the first clinical case, there was a coro-noid process fracture after the medial saw cut wasmade. Excessive traction on the coronoid with a self-retaining bone clamp was thought to be the cause. Thishas not occurred when the lateral cut is made first.

Large condylar deflections do not tend to occur,because the proximal segment will maintain its ap-

FIGURE 5. Preoperative andpostoperative lateral cephalomet-ric radiographs of a bimaxillarycase with mandibular setback.

FIGURE 6. Postoperative pan-oramic radiograph of mandibu-lar advancement on left, setbackon right.

WILLIAM WEBER 239

proximate position mediolaterally with advancementor retrusion. With advancement, the lateral deflectionof the proximal segment at the osteotomy site thatwould tend to occur as the distal segment movesforward is countered by the medial rotation of theproximal segment as bone-to-bone contact is estab-lished along the beveled cut. The opposite is true formandibular setback.

No malocclusion or temporomandibular jointsymptoms have resulted. However, follow-up hasbeen short-term only (4 months), and prospective,long-term study is still needed. The procedure has thedisadvantage of not being generally useful in cases inwhich a large (�6 to 7 mm) movement of the distalsegment is needed.

Although detailed anatomic study of the nuances ofthis osteotomy with various mandibular movementsand long-term study of clinical results have yet to bedone, the initial experience with this technique hasbeen promising.

References1. Pratt CA: Labial sensory function following sagittal split osteot-

omy. Br J Oral Maxillofac Surg 34:75, 19962. Posnick J: Alteration in facial sensibility in adolescents follow-

ing sagittal split and chin osteotomies of the mandible. PlastReconstr Surg 97:920, 1996

3. Lemke RR: Effects of hypesthesia on oral behaviors of the orthog-nathic surgery patient. J Oral Maxillofac Surg 56:153, 1998

4. Jacks SC: A retrospective analysis of lingual nerve sensorychanges after mandibular bilateral sagittal split osteotomy.J Oral Maxillofac Surg 56:700, 1998

5. Fujioka M: Comparative study of inferior alveolar disturbancerestoration after sagittal split osteotomy by means of bicorticalversus monocortical osteosynthesis. Plast Reconstr Surg 102:37, 1998

6. Blomqvist JE: Sensibility following sagittal split osteotomy inthe mandible: A prospective clinical study. Plast Reconstr Surg102:325, 1998

7. August M: Neurosensory deficit and functional impairmentafter sagittal ramus osteotomy: A long-term follow-up study.J Oral Maxillofac Surg 56:1231, 1998

8. Westermark A: Inferior nerve function after mandibular osteot-omies. Br J Oral Maxillofac Surg 36:425, 1998

9. Westermark A: Inferior alveolar nerve function after sagittalsplit osteotomy of the mandible: Correlation with degree ofintraoperative nerve encounter and other variables in 496 op-erations. Br J Oral Maxillofac Surg 36:429, 1998

10. Magalh-aes AE: Changes in condylar position following bilateralsagittal split ramus osteotomy with setback. Int J Adult OrthoOrthognath Surg 10:137, 1995

11. Van Sickels JE: Condylar torque as a possible cause of hypo-mobility after sagittal split osteotomy: Report of three cases.J Oral Maxillofac Surg 55:398, 1997

12. Nishimura A: Positional changes in the mandibular condyle andamount of mouth opening after sagittal split ramus osteotomywith rigid or nonrigid osteosynthesis. J Oral Maxillofac Surg55:672, 1997

13. Van Sickels JE: Condylar position with rigid fixation versuswire osteosynthesis of a sagittal split advancement. J OralMaxillofac Surg 57:31, 1999

14. Martis CS: Complications of the mandibular sagittal split osteot-omy. J Oral Maxillofac Surg 42:101, 1984

15. Van Sickels JE, Jeter JE, Theriot BA: Management of an unfa-vorable lingual fracture during a sagittal split osteotomy. J OralMaxillofac Surg 43:808, 1985

16. Turvey TA: Intraoperative complications of sagittal osteotomyof the mandibular ramus: Incidence and management. J OralMaxillofac Surg 43:504, 1985

17. Marquez IM: Modification of the sagittal split osteotomy toavoid unfavorable fracture around impacted third molars. Int JAdult Ortho Orthognath Surg 13:183, 1998

18. Rosenquist B: Medial displacement of proximal segments: Acomplication to oblique sliding osteotomy of the mandibularrami. Int J Oral Maxillofac Surg 19:226, 1990

19. Moose SM: Surgical correction of mandibular prognathism byintraoral subcondylar osteotomy. J Oral Surg 22:197, 1964

20. Hall HD, Chase DC, Payor LG: Evaluation and refinement of theintraoral subcondylar osteotomy. J Oral Surg 33:333, 1975

21. Tuinzing DB, Greebe RB: Complications related to the intraoralvertical ramus osteotomy. Int J Oral Surg 14:319, 1985

22. Rosenquist B: Stability of the osteotomy site after obliquesliding osteotomy of the mandibular rami: A stereometric andplain radiographic study. J Craniomaxillofac Surg 15:14, 1987

23. Rostkoff KS: Consequences of orthognathic surgery for thetemporomandibular joint. Oral Maxillofac Surg Clin North Am1:261, 1989

24. Petersson A, Willmar-Hogeman, K: Radiographic changes ofthe temporomandibular joint after oblique sliding osteotomy ofthe mandibular rami. Int J Oral Maxillofac Surg 18:27, 1989

25. Paulus GW, Steinhauser EW: A comparative study of wireosteosynthesis versus bone screws in the treatment of mandib-ular prognathism. Oral Surg Oral Med Oral Pathol 54:2, 1982

26. Van Sickels JE, Tiner BD, Jeter TS: Rigid fixation of the intraoralinverted “L” osteotomy. J Oral Maxillofac Surg 48:894, 1990

Table 1. LIST OF PROCEDURES DONE WITHMOVEMENTS

Patient No.Age(yr) Sex Side A-P Movement mm

1 51 F R Setback �3L Setback �3

2 34 F R Setback �4L Setback �2

3 24 F R Setback �3L Advancement �2

4 34 M R Setback �3L Rotation 0

5 27 F R Advancement �7L Advancement �5

6 35 M R Setback �5L Setback �7

7 28 M R Setback �3L Setback �5

8 43 M R Setback �6L Setback �6

9 36 F R Advancement �3L Advancement �4

10 23 M R Setback �4L Setback �4

11 26 M R Setback �4L Setback �5

240 MODIFIED MANDIBULAR RAMUS OSTEOTOMY