Jnt. J. Oral Surg. 1981: 10: 81-86

(Key words: osteotomy, sagil/al split; surgery, orthogna/hie; mandible, prognuthic; prognathism)

Problems encounteredin the sagittal split operation

WILLIAM SIMPSON

Department of Oral Surgery, University Hospital of South Manchester,Manchester, England

ABSTRACT - The sagittal split mandibular osteotomy is a technicallydifficult operation. This article discusses some of the problems en­countered in a series of over 100 cases and describes the instrumenta­tion developed over the years to help overcome the technical difficul­ties.

(Received for publication 25 August, accepted 15 September 1980;

A great deal has been written about thesagittal split mandibular osteotomy over thelast 20 years, particularly with regard to thelong term results achieved by this operationfor treatment of both the prognathic andretrognathic mandible. It is now generallyaccepted as a standard procedure in theoral surgeon's repertoire, but it is agreedthat technically it is a difficult operation.

It is proposed to discuss the technicalproblems encountered with this operationover the last 10 years and to show some ofthe instrumentation developed to overcomethese technical difficulties, in over 100sagittal split operations for both the prog­nathic and retrognathic mandible. Thethree main areas to be discussed are asfollows:

1. Access and illumination.2. The bone cuts ancI bone split.3. The position of the mandibular frag­

ments following the split.

Access to the ascending ramus is difficultand certainly where there is any trismuspresent it is preferable to use some othertechnique. However, in a patient with rea­sonable mandibular movement in which theoperation is to be used, it is preferable toget the maximum access possible bp strip­ping masseter completely from the buccalaspect of the ascending ramus and most ofthe insertion of temporalis from the coro­noid process.

With extreme stripping of the temporalisit is difficult to retract the sof,t tissue fromthe superior aspect of the operative fieldand the coronoid retractor (Fig. 1) hasbeen found useful to retract these tissuesinclUding the buccal pad of fat. Fig. 2shows a buccal retractor which is extremelyuseful both to expose the buccal aspect ofthe mandible and to protect the soft tissueswhen the buccal cut is being made eitherat the angle or the lower border of man-

0300-9785/81/020081-06$02.50/0 @ 1981 Munksgaard, Copenhagen

82 SIMPSON

Fig. 1. Coronoid retractor.

dible. Access to the lingual side of the man­dible is of course a problem and it is usefulto use the Banerjee lingual retractor, which

is placed just superior to the lingula and thecurved end of the retractor hooks round theposterior aspect of the ascending ramus

Fig. 2.Buccal retractor.

PROBLEMS IN SAGITIAL SPLIT 83

Fig. 3. Lingual retractor.

(Fig. 3). The operator again has some pro­tection of the soft tissues when the lingualcut is being made. This retractor is ofcourse somewhat similar to other lingualretractors but offers the operator greaterprotection.

Lighting is also a major problem, particu­larly on the lingual side of the mandibleand to overcome this problem a fibre lightattachment to the Banerjee lingual retrac­tor was devised which gives much improved

Fig. 4. Fibre light attachments.

illumination on the lingual side of themandible. The fibre light stem can be in­serted either before or after the lingualretractor has been placed in position. A setof instruments with fibre light attachmentshas been available on a commercial basisfor some time (Fig. 4) (SIMPSON & STAN­

LEy6).

Having achieved adequate retraction andillumination the standard bone cuts aremade with a Hall air drill, using a Meis­singer surgical bur for the lingual cut.While it is preferable to take the lingualcut back to the posterior border of themandible, there are a number of caseswhere this is difficult because of the severepost lingular depression. The concavity canbe so great and the ascending ramus sothin in this region that the lingual cut mayhave to stop at the lingula as suggested byDAL PoNTi! and HUNSUCK4. An assessmentof the width of the ascending ramus shouldbe made pre-operatively and usually a sub­menta vertical view of the ascending ramiis sufficient although a tomographic exam­ination of the ascending rami has beensuggested by some authorities. However, areview of a number of cases where it wasonly possible to finish the lingual cut at thelingula, showed that the split in the major­ity of these cases dips down below the post

Fig. 5. Bone splits following short lingual cuts.

84 SIMPSON

Fig. 6. Comminution of mandible followingsagittal split.

Iingular depression and eventually runsback to the posterior aspect of the ascend­ing ramus. (Fig. 5) (SnvlpsoN5).

The DAL PONT2 modification of the buc­cal cut is now popular and of course pre­ferable in surgery for the retrognathicmandible. However, the original buccal cutis easier to make and <it also allows for aneasier split of the mandible. While thevertical cut is straightforward it is impor­tant that the vertical cut should run freelyinto the lingual and buccal cuts.

In a number of cases a comminuted frac­ture of the ascending ramus has resulted onsplitting the mandible as seen on Fig. 6.,and the Author firmly believes that the useof heavy osteotomes with a twisting tech­nique is the main cause of mandibularcomminution, and uses a very fine spatula­like chisel designed by BALASUBRAMANIANl

for the initial split, followed by the smallestFrench osteotome which will complete thesplit. This fine chisel has a slight curve onit, the convexity of which should face buc­cally and care should be taken not to driveit totally through the mandible, but onlyto use it as an introducer (Fig. 7).

The fine chisel already described alsohelps to avoid damage to the inferior dental

Fig. 7. Fine chisel.

bundle thus reducing bleeding from the splitand also damage to the nerve. The retentionof the retractors in position while the splitis carried out also provides protection to thesurrounding soft tissues and helps again tocut down bleeding from the soft tissues, inparticular the periosteum. Certainly with acareful split and good protective retractorsthere is little trouble with bleeding.

While most cases have initial anaesthesiaof the mental nerve, this has usually clearedby 2 months although as can be seen fromFig. 8, a number of patients do havepermanent problems. It will also be seenthat a small number of patients havesustained damage to the facial nerve, butthis has been a transient problem.

Technical problems may still ensue after

PROBLEMS IN SAGITTAL SPLIT 85

Fig. 8. Neurological involvement followingsagittal split osteotomy.

.;

Fig. 9. Bilateral facial palsy following sagittalsplit osteotomy of mandible.

Fig. 10. Posterior fragment pulled upwards andforwards.

tal split osteotomy. It was very difficult inthis case to move the mandible back intoposition and it was thought that the facialpalsy had followed oedema within the paro­tid gland with resultant pressure on thefacial nerves. Fortunately as in a number ofpreviously reported cases the bilateral facialweakness recovered completely, approximat­ely 6 weeks after surgery when the inter­maxillary fixation was removed (DENDy3).

However, if there is little space betweenmastoid and the posterior edge of the as­cending ramus and if the required pushback is more than 15 mm it is preferableto use some other technique.

Assessment of the antera-posterior widthof the mandible before operation is also im­portant and on occasions it is found thatthe AlP width of the mandible isinadequate to achieve the planned positionbecause of lack of bony contact. This lackof bony contact may also occur if theposterior fragments of mandible are pulledupwards and forwards by temporalis (Fig.10). A certain amount of movement of theposterior fragment is acceptable because ofthe large area of bony contact and the firmperiosteal and muscle bundle surroundingthe fragments. However, in this case fur­ther surgery was required to wire the frag­ments into position, as the posterior frag­ment was showing through the wound and

20'){­2%

Sagittal split osteotomiesNeurological damageMental nerveFacial nervc

successful splitting of the mandible, and ina number of cases it may be difficult tomove the prognathic mandible back into it'splanned position, particularly if there ap­pears to be little space between the posterioraspect of the mandible and the mastoidprocess. Again if the push back of themandible is more than 12-15 mm, difficul­ties may be encountered in achieving theplanned position of the mandible.

Fig. 9 shows a patient who developed abilateral facial palsy 24 hours after a sagit-

86 SIMPSON

there Was minimal bony contact betweenthe fragments.

However, the Author feels it is preferableto leave the posterior fragments free with­out wiring but this does mean adequatestripping of temporalis and masseter asdescribed earlier. Certainly by not wiringthe fragments there appear to be muchless temporomandibular joint problemspost-operatively, and one can be sure thatthe head of condyle remains in the glenoidfossa.

This paper hall described a number oftechnical problems encountered with thesagittal split mandibular osteotomy whichnevertheless is an excellent operation par­ticul'arly for the correction of the prog­nathic mandible.

Acknowledgements - My thanks are due toMrs. G. M. Taylor for her secretarial helpin preparing this paper and the Medical Illu­stration Department, U.H.8.M for the illustra­tions.

References1. BALASUBRAMANIAN, S.: Personal communica­

tion, 1971.2. DAL PONT, G.: Retromolar osteotomy for

the correction of prognathism. J. Oral Surg.1961: 19: 42-47.

3. DENDY, R. A.: Facial nerve paralysis follow­ing sagittal split mandibular osteotomy. Br.J. Oral Surg. 1973: 11: 101-105.

4. HUNSUCK, E. E.: A modified intra oral sa­gittal splitting technique for the correctionof mandibular prognathism. J. Oral Surg.1968: 26: 250-253.

5. SIMPSON, W.: The short lingual cut in thesagittal split osteotomy. J. Oral Surg. 1972:30: 811-812.

6. SIMPSON, W. & STANLEY, W.: The use offibre lighting in oral surgery. IV Interna­tional Conference on Oral Surgery. Munks­gaard, Copenhagen 1973, pp. 229-231.

Address:

Withington HospitalWest DidsburyManchester M20 8LREngland