j. max.-fac. Surg. 9 (1981) ] 5 ]

J. max.-fac. Surg. 8 (1981) 151-165 © 1981 Georg Thieme Verlag Stuttgart • New York

Experience with the Sagittal Osteotomy of the Mandibular Ramus: A 13-Year Review* Robert Bruce Macintosh

Department of Oral and Maxillo-Facial Surgery (Director of Graduate Educa- tion: B. Macintosh, D.D.S.) School of Dentistry University of Detroit and Sinai Hospital Detroit, Michigan, USA

The intraoral ramus sagittal os teotomy as commonly exer- cised today owes its popular i ty to the ingenuity and educa- tional efforts of Professor Hugo L. Obwegeser. Whatever educational value this paper may have is dedicated to Professor Obwegeser on the occasion of his 60th bi r thday and the 25th Anniversary of his Zurich Clinic.

Introduct ion

The technique which provides the substance of this report owes its inception to Schuchardt's suggestion (1942, 1955) of intra-oral ly sectioning the ramus obliquely in the sagittal plane to effect a greater area of overlapping bone than was provided by the earlier horizontal ramus osteotomies. Mathis amplified this technique in 1956, but it was Obwe- geser, first in German in 1955 and then in English in 1957, who popular ized the sagittal step-wise technique in the ascending ramus, which in itself and with various modifica- tions has maintained its posit ion of eminence in the man- agement of mandibular deformities to this day. The major modification, one which increased the amount of overlap- ping bone by as much as 100 %, was suggested by DalPont in 1959; various other authors have suggested modifica- tions to assist stability, simplify fixation, or hopefully reduce the rate of relapse or the intensity of physiological insult at the surgical site (DalPont 1961, Hunsuck 1968, Gallo et al. 1976, Epker 1977). This survey reviews the author ' s experience in the manage- ment of 236 of his own cases operated between 1965 and 1978, 155 of which could be consistently evaluated at a minimum of 2 years postoperat ively and an addi t ional several dozen cases in which he served as resident, teacher, or consultant. All cases were operated on in a fashion routinely employed by the Zurich School up until 1976, with the bone cut made in the pat tern of the classic DalPont modification; since 1976, surgeons in Zurich have reverted to the original Obwegeser technique for the management of prognathia as described in Freihofer's excellent review (1976).

* Dedicated to Prof. Dr. H. C. Obwegeser on the occasion of his 60th anniversary

Summary

This repor t surveys the experience in 236 patients operated on by the author, of whom 155 provided records complete enough to provide information on all the elements of postoperat ive evaluation. Patients were evaluated at a minimum of 2 years after surgery. The patients had an average age of 23 years, and were predominant ly female in a ratio of more than 4 : 1. No intraoperat ive or postoperat ive physiologically threatening problems as elsewhere described in the literature, such as profound blood loss, a i rway obstruc- tion, or gross loss of bone substance, were encountered. An immediate postoperat ive paraesthesia incidence of almost 85 % was observed, which diminished to 9 % 1 year postoperatively. The prolonged paraesthesias were most common in patients over 40 years of age; simi- larly, healing was prolonged in patients over 40, p rompt ing the author 's recommendat ion that 8 weeks intermaxil lary fixation rather than 6 be employed in these patients. The overall relapse rate was approxi- mately 30 %; this was clinically significant in approxi- mately 12 % of patients, and required reoperat ion in 4 patients. Relapse was most marked in apertognathic patients, demonstrat ing, in the author ' s opinion, that the sagittal ramus osteotomy should not be used, in general, in open-bite cases. The part iculars of the technique and the author 's views on regression are presented.

Key-Words

Sagittal ramus osteotomy Regression; Paraesthesia.

- Operat ive problems -

Description of Technique

All patients operated in this review underwent the procedure under nasoendotracheal anaesthesia. In the standard procedure, pressor- containing local anaesthetic solution is infiltrated into the peri-ramal soft tissues. The vertical incision terminates infero-laterally in the looser gingival tissues away from the necks of the teeth to ensure sufficient tissue on either side of the incision for proper closure. No attempt is made to avoid the buccal artery; its transected ends are appropriately clamped and ligated. The fat pad is occasionally encoun- tered and, if so, is displaced laterally by appropriate positioning of a gauze sponge. The soft tissues are elevated off the entire lateral aspect of the ramus and posterior portion of the mandibular body in sub- periosteal fashion, as are the fascial sling along the posterior and inferior borders, and the tissues on the medial aspect of the ramus between the levels of the mandibular foramen and depth of the coronoid notch. The latter are elevated all the way to the posterior border. Bone cuts are made in accord with the DalPont modification with long, medium, and short Lindemann burs. Because of anatomical variance, one cannot make definite rules as to the depth of the cuts except to ensure that they go through the entire thickness of the cortical bone; an exception to this is the instance of an extremely thin ramus in which case the medial cut must be at least deep, sharp, and distinct enough to score the cortex. The bone is next divided with osteotomes struck sharply with the surgical mallet. A sharp fracturing of the segments, in the author's hands, ensures a higher probability of desired sectioning than does a slower, cutting, wedging technique; the contention that the latter technique is a better guarantee against lasting paraesthesia is, in the

0301-0503/81 1400-0151 $ 03.00 © 1981 Georg Thieme Verlag Stuttgart . New York

152 J. max.-fac. Surg. 9 (1981) R.B. Macintosh

Fig. 1 a

Fig. 2 a

Fig. 1 b

Fig. 2 ~

Fig. 1 Application of splitting force; a) forceful insensitive grasp of mallet and osteotome which delivers a blunt cutting force to the bone; b) more sensitive light- fingered grasp of the instruments which allows a sharp splitting force to be applied.

Fig. 2 Left osteotomy site; a) osteotome inserted directly into the sagittal osteotomy, resulting in division of the bone medio-post- eriorly only to the region of the mandibular foramen; b) osteotome directed laterally in the sagittal cut to ensure sectioning of the bone through the angle.

d

Fig. 3a Fig. 3 b

Fig. 3 Passage of the circumferential bone wire; a) improper perpendicular approach with the awl, which makes access difficult and poses potential dangers to the structures of the neck and medial aspect of the man- dible; b) more correct parallel approach of the awl to the lateral face and neck facilitating uncomplicated placement of the wire.

Experience with the Sagittal Osteotorny J. max.-fac. Surg. 9 (1981) 153

DISTRIBUTION (By Diagnosis)

1236 CASES]

IPROGNATHIA I[RETROGNATHIA J

55.8% 38.5% 72.9% with an 72.5% with an anc i l lary anc i l la ry diagnosis diagnosis involving: involying:

1, Maxil la 2. Apertognathia 3. Condyle 4. Mandibular asymmetry 5. Mandibular alveolus

[ APERTOGNATHIA } I B/ILATERAL/ i 5.8%

Fig. 4 Distribution of 236 cases by diagnosis.

DISTRIBUTION CBy Site)

1236 CASES I

95.9%

I UNIlATERaL i

4.1%

I ASSOCIATED ORTHOGNIA~IHIc, SURGERY I

In Maxi l la: 39.0%

In Mandible: 30.0%

Fig. 5 Distribution of 236 cases by site.

OPERATIVE PROBLEMS (Sect ioning)

DISTRIBUTION [By Age & Sex)

12'36 CAS'ES ~

Average: 250 years/months Female: 72.1

Range: 135 - 533 years/months Male: 17.9

Fig. 6 Distribution of 236 cases by age and sex.

author's judgment, debatable (Freihofer 1976). The inclination of the osteotome is critical, however. It must be held so as to direct the splitting force laterally within the sagittal osteotorny to ensure section- ing of the ramus along its posterior border; directing the force directly into the vertical plane of the osteotomy will effect a medial fracture no further posteriorly than the position of the lingula, leave the medial cortex proximal to that point intact on the proximal segment, and diminish significantly the amount of overlapping bone (Figs. 1 and 2). Any impacted 3rd molars are removed after the ramus is completely sectioned. Residual fascial attachments along the inferior border of either frag- ment are next elevated with the curved periosteal elevators. This elevation on the medial fragment is, of course, limited and represents the only safe approach to the internal pterygoid muscle with this technique. Complete mobilization of the proximal segment ensures good visibility, less chance for impingement of the neurovascular bundle, and better control of the segments at the time of fixation. Following full mobilization of the distal mandible, circumferential 26- gauge stainless steel wires are passed around the segments in either wound with the use of the zygomatic awl introduced through a submandibular perfacial puncture site anterior to the pregonial notch (Fig. 3). This technique is simplified by extending the neck and turning the patient's head away from the operative side; this ensures that neither the operator nor the awl are impeded by the patient's ipsilateral shoulder, and that the awl is introduced parallel to the inner table of the mandible, rather than perpendicular to it and the other structures of the neck. Once the appropriate intermaxillary fixation has stabilized the mandible, and any bony contours which impede flat apposition of

I DIFFICULT 1 SECTIONING__]

11.5% of Patients (5,9% of Sites)

I IMPERFECT S ECTIONZNG 1

7.4% of Patients (3.8% of Sites)

I FRACTURE OF SEGMENTS I

6.6% of Patients (3.3% of Sites)

25.5% of Patients (12.9% of Sites)

Fig. 7 Difficulties in sectioning the posterior body and ramus.

the segments have been removed, the circumferential wires are tight- ened so as to appose the two segments firmly, but not absolutely rigidly. The proximal segments are then grasped with Kocher or tonsil clamps and moderate, but not excessive, pressure applied so as to stabilize the condyles within the fossae as the circumferential wires are tightened. The wounds are copiously flooded with topical antibio- tic solution prior to closure, and the wound margins reapproximated with 3-0 silk. A thin rubber catheter is inserted into the lower end of either wound to facilitate drainage for 24 hours. A pressure head dressing is applied so as to produce a moderate degree of pressure directly over the lateral aspects of the rami. This dressing is left in position for 48 hours. Since 1976, steroid therapy, usually dexamethasone in 4 nag. b.i.d. dosage, has been initiated immediately before surgery and given through the first postoperative day to diminish postoperative oedema. Since the initiation of steroid therapy, prophylactic antibiotics have been given routinely, as well; penicillin G or penicillin V, 500 mg, 6 h. for 10 days, is the usual regimen, when circumstances allow. Intermaxillary wire fixation remains in place for 6 weeks in patients under 40 years of age, and for 8 weeks in those over 40. Patients begin an oral diet, usually by the beginning of the second postoperative day, designed to deliver 1800-2500 calories and 100-150 grams of protein daily. They begin oral rinses of 1 : 1 hydrogen peroxide and commer- cial mouthwash on the first postoperative day, and maintain oral hygiene with this solution usually with home water spray devices throughout the period of fixation. The patients return for out-patient examination within 1 week after release from the hospital, and at 10-14 day intervals thereafter until termination of intermaxillary

154 J. max.-fac. Surg. 9 (1981) R.B. Macintosh

) 3

Fig. 8 Difficulties in bone sectioning arranged in order of decreasing frequency; 1 ) sectioning of the bone on the lingual aspect anterior to the posterior border and superior to the inferior border; 2) fracture of the antero-superior corner of the proximal segment; 3) preservation of the neurovascular bundle in the proximal segment (bundle not necessarily transected); 4) inferior border left intact on distal segment; 5) lateral fracture proximal to the vertical osteotomy, usually resulting from excessive lateral inclination of the osteotome; 6) medial sectioning superior to the angle, leaving the inferior border intact on the proximal segment; 7) horizontal fracture of the lateral cortex along the line of medial horizontal osteotomy,

fixation. A single light training elastic is placed on either side and left in position for 4-6 weeks after the intermaxillary wires are removed to encourage maintenance of the new mandibular position as function returns. Patients return for 3, 4, 8, 12, and 26-week recall visits through the second postoperative year, and thereafter, ideally, for 3 years on an annual basis.

Description of Review

The records of 236 patients operated on between the years 1965 and 1978 were reviewed. Of these, 155 had records complete enough to allow an objective preoperative, intra- operative, and postoperative review. Those patients of the remaining 81 who had obtainable but incomplete records were included in the survey for those elements of the review for which the records did provide usable data.

A. Distribution The distribution of the population by diagnosis, site, and age and sex, is shown in Figs. 4, 5, and 6. The 3 major classifying diagnoses were prognathism, retrognathia, and skeletal apertognathia independent of the other 2 diag- noses. As will be noted in Fig. 4, approximately 73 % of the prognathic and retrognathic patients had ancillary diag- noses, among them apertognathia. These ancillary prob- lems account for the percentage of concomitant or sup- plementary operations carried out in these patients noted in Fig. 5. The sex distribution is consistent with the author's general experience for orthognathic surgery. Approxi- mately 61% of patients underwent orthodontic care, reflecting a contrast to much of the European writing and emphasizing the great interest that American orthodontics has taken in the treatment of maxillo-mandibular dishar- mony.

B. Operative Difficulties Fig. 7 describes the difficulties experienced in sectioning the bone in this series. In 11.5 % of patients, tenacity of the bone, difficulty in placing the osteotomes, or anatomical irregularities made division of the bone particularly time-

consuming and/or physically difficult, though proper sec- tioning ultimately ensued. In more than 7 % of patients, however, the splits did not correspond precisely to the lines of Obwegeser-DaIPont sectioning. In an additional 6.6 % of patients, there was actual fracture of the proximal seg- ment, though in some cases the sagittal sectioning was nonetheless executed in the desired fashion. The imperfec- tions occurring in the total of 14 % of patients and 7.1% of sites are demonstrated in Fig. 8 in order of decreasing incidence. Fig. 9 lists the other operative difficulties. Bleeding seen in 10.7% of patients proved problematic in the sense of obstructing vision or being time-consuming in its control. There were no instances of threat to life by operative bleeding. Several cases of previously undiagnosed minor bleeding diatheses became manifest in this group. A calamitous episode of bleeding resulted from transfusion of mismatched blood in one patient. Most of the 5.7% of patients receiving blood transfusions were operated on between 1966 and 1972 when, in one particular institution, blood loss over 1,000 cc. almost automatically entailed whole blood or packed red cell replacement. Inferior alveolar nerve transection occurred only rarely when the ramus was sectioned properly. Miscellaneous problems included poor access to the opera- tive field (due most commonly to antero-posterior concav- ity of the ramus, position of the maxilla, or prominence of the buccal fat pad), difficulty in fixation wire placement, rotation of the short-side proximal segment in asymmetric cases, and cardiac arhythmias associated with the injection of local anaesthetic solutions.

C. Postoperative Difficulties The major postoperative considerations in the ramus sagit- tal osteotomy are those of paraesthesia, more particular to this procedure itself, and regression, a problem in mandibu- lar procedures, in general. The incidence of these difficulties is shown in Figs. 10, 11 and 12. Evaluation of paraesthesia was made in simple light pin- prick fashion with no attempt at quantitative evaluation.

Experience with the Sagittal Osteotorny J. max.-fac. Surg. 9 (1981) 155

OPERATIVE PROBLEMS (Other)

I PROBLEMATIC BLEEDING i 10.7%

I PATIENTS REQUIRING TRANSFUSION i 5.7%

NOTE: Average Blood Loss 1454 cc I (140-2000 cc)

[NERVE TRANSECTION I 1.6%

I MISCELLANEOUS I :>1%

Fig. 9 Operative difficulties other than those associated with divi- sion of the bone.

PARAESTHESlAS

II~EDIATE] F ~ ( I year postoperatively)

Bilateral Unilateral Bilateral Unilateral

I ROLE OF AGE I

387 years/months (" J

Fig. 10 Incidence of paraesthesia in relation to time, site, and age.

The labial gingiva, the mucosal surface of the lower lip, and the skin surface of the lower lip were evaluated indepen- dently, and all obviously or questionably positive responses were recorded as evidence of paraesthesia. The long-term evaluations were made with the patient's eyes closed to minimize the influence of subjective optimism or anticipa- tion on the part of the patient. An unquestionable relation- ship between age, in patients 40 and older, and protracted paraesthesia was evident. Relapse was evaluated both radiographically with cephalograms and clinically by tooth position. Radio- graphic evaluation entailed superimposition of preoperative and postoperative cephalograms, the latter taken a minimum of 6 months, and, in most cases, between 10 and 14 months postoperatively. The cephalometric references were pogonion and B point, and, where necessary for better definition, their relationships to their various tangents (N-B line, B-incisal angle, mandibular plane angle, etc.). As is obvious, the accuracy of discrepancies of i mm., even when the tracings are repeated by the same or other investigators, remains open to question. Discrepancy at the occlusal level was determined by com- parative measurements on the surgical models, in those cases in which the surgeon was satisfied that the immediate surgical result corresponded to that predicted, or on mod- els made within 3 weeks of the removal of the intermaxil- lary fixation in those cases in which he had some uncer- tainty as to the surgery reflecting the prediction models, with models mounted in centric relation a minimum of 1 year postoperatively. The accuracy of such measurements is rather easy to ensure, but a major potential variable is the accuracy of the postsurgical mounting, particularly in those patients undergoing post-surgical orthodontics. A signifi- cant number of patients did undergo such care, even up to 12 months postoperatively. The possibility of dental move- ment secondary to orthodontics being interpreted as true relapse particularly in those patients classified as +1 regressive, is quite real. Attempts to record the progressive changes in postoperative orthodontics with check models or progressive linear measurements became too inconsistent and/or problematic to be of value, and so were abandoned. Fig. 11 describes the evaluative criteria and overall inci- dence of regression in this series. Fig. 12 records the regres- sion rate by diagnosis; the prominence of apertognathia in

this regard, both as an isolated and an ancillary diagnosis, is readily evident. Fig. 13 lists the problems seen postoperatively to a lesser degree or more transient extent. Most notable is the inci- dence of anxiety, related primarily to the intermaxillary fixation. These problems were all diagnosed through the usual clinical, radiographic, or laboratory means, and are discussed independently in subsequent pages.

Discussion and Conclusions

The mandibular sagittal ramus osteotomy must certainly be the most "cussed" and discussed single procedure in all the history of orthognathic surgery. Despite the great interest, there are only a few long-term evaluations of significant numbers of patients operated on with the technique (Egyedi 1965, White et al. 1969, Cook and Hinrichsen 1973, Vija- yaraghavan et al. 1974, Wang and Waite 1974 and 1975, Freihofer and Petresevic 1975, Broadbent and Woolf 1977, Souyris 1978, Pepersack and Chausse 1978, J6nsson et al. 1979). At the 1980 meeting of the German Society for Maxillofacial Surgery, several authors reported long-term studies but these results are not yet published. Unquestionably, the most oft-quoted article in the Ameri- can literature is that of Behrman (1972). This paper sur- veyed cases operated on by 64 different American surgeons. In this author's opinion, the Behrman article, though well- intentioned, was premature in that it represented the short- term experience of a surgeon population generally inexperi- enced in the technique. The conclusions drawn from that survey may well have led to a distorted view of the man- dibular ramus sagittal osteotomy; the fact that the proce- dure has remained popular, however, testifies to satisfac- tion with the technique on the part of surgeons internation- ally (Vijayaraghavan et al. 1974, Wang and Waite 1975, Freihofer and Petresevic 1975, Freihofer 1976, 1977b, Epker 1977.

A. Operative Considerations The sagittal ramus osteotomy is not a blind procedure (Wang and Waite 1975, Hull and Smith 1976). With proper instrumentation, the operator views the field and controls the segments certainly as well as he does with other ramus techniques from the extraoral approach, and perhaps, better than he can with the condylar or vertical

156 J. max.-fac. Surg. 9 (1981) R. B. Macintosh

RELAPSE

I OCCL USAL i

+1 Up to 1.0 mm. 18% anteroposter ior and/or ver t i ca l change from recon- structed occlusion

+2 From 1.0 - 2.5 mm. 8% anteroposter ior and/or ve r t i ca l change from recon- structed occlusion

+3 More than 2,5 mm. 3.2% anteroposter ior and/or vertCcal change from recon- structed occlusion

I ESTHETIC I

Up to 1,0 mm. 11% change in chin pos i t ion (pogonion and/or sof t t issue) on la te ra l cephalogram

From 1.0 - 4,0 mm. 2.5% change in chin pos i t ion (pogonion and/or sof t t issue) on l a te ra l cephalogram

More than 4.0 mm. 0% change in chin pos i t ion (pogonion and/or sof t t issue) on l a te ra l cephalogram

Fig. 11 Description of the evaluative criteria and incidence of occlusal and aesthetic regression.

+1

+2

+3

Fig. 12

OCCLUSAL RELAPSE(By Diagnosis)

I PROGNATHIA ] I RETROGNATHIA[ [APERTOGNATHIA}

20.3% 16.7% 0%

10.2% 6.25% 33,0%

1.45% 6.25% 0%

31.9% 29.2% 33%

~ W i t h a / concomitant diagnosis of

[APERTOGNATHIA-~

Distribution of occlusal regression by diagnosis.

POST-OPERATIVE DIFFICULTIES (Exclusive of Paraesthesias and Regression)

Anxiety 14.7 % Delayed Union 5.7 % Wound Infection 5.7 % Fixation Wire Perforation 5.7 % Prominent Proximal Segment 2.5 % Malpositioned Condyle 2.5 % Fibrotic Scar 1 •6 % Miscellaneous 2.5 %

Fig. 13 Postoperative difficulties less severe and/or less frequently encountered than paraesthesia or relapse•

ramus techniques from the intraoral approach. If any technique demands a particularly sophisticated instrumen- tation, the MSRO does. The original retractors, or accept- able variations thereof, to control the temporalis muscle, relieve the periosteum, protect the inferior alveolar neurovascular bundle, provide visualization to the medial aspect of the ramus, and provide quick, distinct, cutting of the bone, are mandatory. While access is good, however, the technique is not without operative difficulty.

Bleeding: At the time of incision, the cut ends of the buccal artery should be immediately identified and ligated. It is possible for the transected buccal artery to become con- stricted through the action of the injected vasopressor, and, if left unclamped, to begin bleeding again as the effect of the vasopressor is expended. The author has had the experience of wasting over 20 minutes at the completion of a case seeking out a buccal artery in this exact circumstance. Inadvertent bleeding from the inferior alveolar vessels can- not be as easily controlled from this approach without damage to the inferior alveolar nerve. Such bleeding has arisen on a few occasions, and, in most cases, has been

controlled with digital pressure in the lateral pharynx and/ or tamponade with a sponge in the wound itself; in 3 cases it was better controlled with catgut ligation. Absolute trans- ection of the inferior alveolar artery or vein has not been encountered knowingly; on 2 occasions, however, low- grade but persistent oozing from this site was significant enough to necessitate leaving a pressure sponge in position in the medial wound, after the case was otherwise fully completed, for 2-3 days postoperatively, at which time it was carefully removed, the wound irrigated with antibiotic solution, and the incision finally closed. In one case, the facial vein was torn during the stripping of the periosteum along the inferior border of the mandible; bleeding was controlled with pressure until the torn vessel could be appropriately dissected and ligated. In the case of a potentially calamitous puncturing of the retromandibular vein, one would not have as ready access to the upper course of this vessel from the intraoral approach. The author has never encountered this problem. The average and extremes of blood loss in this series are shown in Fig. 9, as are the percentage of patients requiring packed cell or whole blood transfusions. The blood loss is essentially similar to that reported elsewhere (Guernsey and DeChamplain 1971, Vijayaraghavan et al. 1974, Byrne and Hinds 1974). Several of the cases of greater blood loss in this series represent the patient's undisclosed use of aspirin for an unrelated problem immediately preoperatively. Four cases of nondescript marginal coagulopathy were disco- vered postoperatively, as was 1 case of true von Wille- brand's Disease. In patients with known or suspected his- tories of coagulopathies, and even in those young, appa- rently healthy individuals who have never been challenged surgically, a prothrombin time, partial thromboplastin time, platelet count, bleeding time, and fibrinogen level determination are part of the routine preoperative labora- tory evaluations. As mentioned earlier, most of the patients receiving transfused blood were operated on prior to 1972 under policies necessitating blood replacement in losses over 1,000 cc. Blood loss in the patient receiving mis-

Experience with the Sagittal Osteotomy J. max.-fac. Surg. 9 (1981) l 5 7

Fig. 14 Position of the bur in placement of the lateral vertical osteotomy; a) proper placement of the bur in vertical fashion with the tip at or just lateral to the height of curvature of the inferior border; b) bur inclined too severely to the lingual aspect, with resultant cut through the inferior border and probable imperfect sagittal sectioning of the bone.

Fig. 15 Anterior displacement of the condyle as a result of the proximal segment being insufficiently stabilized as the circumferential fixation wire was tightened.

Fig. 16 Postoperative view of a mandibular condyle uncomfortably displaced posteriorly in the fossa in a patient in whom an alveolar level fixation wire was utilized.

matched blood was incalculable, and is not included in this average; though she ultimately survived, the patient was 1 of 2 contracting hepatitis in this survey group. The opera- tive procedure was also compromised, wound infection and partial necrosis of the proximal segment on one side ensued, but reoperation 5 weeks after the initial procedure led to a successful repositioning of the mandible.

Bone Sectioning: In sectioning the bone, proper angulation of the osteotome is particularly important. In this author's opinion, the instrument should be held lightly but firmly in the fingers, and struck firmly and sharply with the mallet against counter-traction to direct full force precisely at the tip of the instrument. If the osteotome is held in a tight fist, the blow is dampened, and, similarly, if the mallet is held in a full grasp and the force delivered in blunt fashion, the osteotome will be driven into the bone as a cutting tool, and will not crisply split the bone along the desired planes (Fig. 1). The osteotome is best introduced first at the junc- tion of the buccal and sagittal osteotomies, directed at an obvious lateral tangent (Fig. 2). Additional osteotomes are

advanced sequentially along the line of the sagittal osteotomy following each blow. Two or three properly directed strokes are usually sufficient to divide the mand- ible. Obtaining the proper lateral inclination of the osteotome is sometimes difficult because of the arch form of the upper teeth; in these cases, care must be taken to avoid damage to these teeth as the osteotome is struck. A maxil- lary central incisor was fractured because of an oversight in this regard in a patient in this series. Mercier (1973) has nicely demonstrated the mechanics of the ideal sagittal split. Even with the most careful precau- tions, however, less than perfect division of the bone is not uncommon. JSnsson (1979) reports only a 13 % incidence of ideal sectioning in his series of 28 patients. The percen- tages of this report (87,1%, Fig. 7) are somewhat more encouraging in this regard, and may reflect emphasis on the angulation of the osteotome mentioned above, and avoi- dance of carrying the lower end of the buccal bone cut too far medially on the inferior surface of the mandible. If this cut is made too deeply, the inferior border and/or angle of the mandible will almost invariably remain intact on the

158 J. max.-fac. Surg. 9 (1981) R. B. Macintosh

. . . .

Fig. 17a

Fig. 17b

Fig. 17 improperly placed circumferential fixation wires; a) postoperative panoramic view demonstrating a properly placed wire on the left side and an improperly placed wire on the right, in this case without detrimental effect; b) postoperative view of mal- positioned proximal segment resulting from placement of the circumferential wire right at the angle of the proximal segment and com- pletely above the angle of the distal segment.

proximal segment (Fig. 14). As Fig. 8 indicates, the most common imperfect sectioning follows the line of osteotomy as originally suggested by Perthes in 1922, described for intraoral usage by DalPont in 1959 and 1961, and later emphasized by Hunsuck (1968), Simpson (1972), and Epker (1977).

Condylar Seating and Fixation: Probably the 2 potential difficulties of most lasting significance in this procedure are improper condylar positioning and improper application of the fixation wires. Freihofer (1976) has recommended intraoperative radiographic evaluation of condylar position to ensure its correctness; this suggestion doubtless has merit if logistically feasible, and not only for the sagittal section- ing technique, but this author has no significant experience in this regard. Our experience has been that a gentle but firm elevation of the proximal segment into the fossa, and its firm stabilization in this position as the fixation wire is applied, is sufficient to ensure condylar position within physiologically normal bounds. Leonard (1976) and Zecha et al. (1978) have described mechanical aids for stabiliza- tion of the condyles. The film of Fig. 15 illustrates a case in which this procedure was not followed well, and Fig. 16 demonstrates a case, outside this series, in which efforts to position the condyle properly were carried to forceful excess. The latter patient suffered from retrognathia and, in an effort to ensure maintenance of condylar position as the mandible was advanced, an alveolar fixation wire was applied in upward traction fashion to ensure seating of the condyle. The seating force was sufficient to compress or

displace the disc in the posterior fossa to the degree noted in the radiograph. Postoperatively, the patient complained of temporomandibular joint pain alleviated only by protru- sion out of her refined Class I malocclusion into a Class III relationship; the condition could only be alleviated by reoperation on the patient for correction of her iatrogenic mandibular prognathism. This forceful, rigid, displacement of the condyle is one of the author's two major dissatisfactions with the alveolar level intraosseous fixation wire. The other is the fact that the alveolar wire, particularly when it is drawn tightly to produce a fine-line interface along the superior aspect of the osteotomy, may result, and has, in a divergence of the segments along the inferior border, resulting in unnecces- sary lateral displacement of the condyle and delayed union. The third, more minor difficulty is that of access for place- ment of the burholes for this wire, particularly in cases of marked prognathia. Gallo et al. (1976) have suggested a lateral wiring modification which reduces this problem. Because of the difficulties with alveolar level wiring, the segments in all but a few cases in this series were stabilized with circumferential stainless steel wires (Obwegeser 1964, Freihofer 1976). When these wires are appropriately placed, they provide secure adaption of the surfaces, but enough movement, as muscle reattachment and wire stretching occur in the postoperative weeks, to allow phy- siological adaption of condylar position within the fossae. This wire can be inappropriately placed, however. When positioned superior to the angle, as shown in Fig. 17, it is immediately less effective in apposing the bony surfaces,

Experience with the Sagittal Osteotomy J. max.-fac. Surg. 9 (1981) 159

ROLE OF AGE IN SIGNIFICANT POST-OPERATIVE PROBLEMS

Delayed Union 32.7 Years

Late Paresthesias 38.6 Years

Regression + 2 24.8 Years + 3 19.3 Years

Fig. 18 The relationship of age to the incidence of delayed post- operative difficulties, ages expressed as averages; delayed union is defined as incomplete healing at the 6th postoperative week, late paresthesias are those still present 12 months postoperatively, criteria for regression are described in Fig. 11.

Fig. 19 Undesirable displacement of the proximal segment on the short side, the patient's left, in a case of asymmetrical mandibular prognathia; film taken 24 hours postoperatively, drains still in position.

can actually act to displace the condyle as it is tightened, and may ultimately slip superior to the medial horizontal osteotomy. In only one patient of this series was an operated site left without an adaption wire. This was done on a trial basis, and, once the resultant poor segmental adaption became obvious on the postoperative film, an alveolar level wire was placed under local anaesthesia. This was done on the 3rd postoperative day, and the degree of muscle influence on the proximal segment by that date, as the patient spoke during the wiring procedure, was remarkable.

Splints: In edentulous patients, in those with mutilated dentitions, those with occlusions not yet orthodontically refined, and those in whom the mandible is intentionally being positioned into a malocclusive relationship, use of acrylic splints is routine. In those patients in whom the desired occlusal relationship is readily discernible however, we do not use splints. A properly made, well-fitting, splint unquestionably shortens the time of operation; too often, however, in the author's experience, splints require consid- erable adjustment in the operating room, and their forceful seating can result in displacement of the segments. In the best circumstances they do not allow direct visualization of the occlusal relationship during the postoperative period; we much prefer to view the occlusion directly, in order to intercept and correct, if possible, undesirable shifts as they become evident.

Miscellaneous: If the buccal fat pad is encountered in the initial incision, as it can be even when the incision is kept on the medial aspect of the anterior border of the ramus, it has been the author's experience that forced displacement of

the pad with a gauze sponge is preferable to trying to control and/or avoid the structure with instrumentation throughout the rest of the procedure. As in all deep wounds, however, care must be taken to ensure a proper sponge count periodically during the proce- dure. In one of the cases in this study the presence of a retained sponge in the medial aspect of the wound was not discovered until the completion of the case and necessitated reopening of the wound. The author is familiar with another case, outside this survey, in which a sponge was not recovered from a wound until 10 weeks postoperatively and then only with great good fortune on the second attempt. In one case, a long Lindemann bur was fractured on the inner aspect of the mandible, and required considerable time and radiographic assistance for its recovery; it had been broken at the level of the horizontal osteotomy, and, within minutes, had been drawn superiorly to the level of the condyle by elements of the internal pterygoid muscle.

B. Postoperative Considerations The transient and/or infrequent postoperative difficulties are shown in order of decreasing frequency in Fig. 13.

Anxiety: Almost 15 % of the patients demonstrated anxiety in regard to intermaxillary fixation, and many of these required mild sedative medication to prevent detrimental stretching of the fixation wires during bruxing. The inci- dence of anxiety in these patients probably compares with its frequency in intermaxillary fixation for other reasons.

Infection: Wound infections were infrequently encoun- tered, and in most instances responded to local irrigations,

160 J. max.-fac. Surg. 9 (1981) R.B. Macintosh

Fig. 20 a Fig. 20 b

Fig. 20 Unacceptable scarring along the line of incision; a) prominence of the scar approximately 18 months post-operatively with the tissues subject to repeated mechanical trauma; b) status of the tissues one week following corrective Z-plasty, sutures marking the configuration of the repair.

Fig. 21 Radiograph taken 5 weeks post- operatively indicating resorption along the line of horizontal osteotomy with unaccept- able displacement of the condylar segment (re-operation required).

systemic antibiotics, and supportive care. The 2 cases of sequestration noted in this series resulted from obvious wound sepsis. Excepting 1 case of predominantly Proteus growth, the causative organisms were overwhelmingly streptococci and staphylococci.

Delayed Union: Cook and Hinrichsen (1973) report fixa- tion periods of approximately 4 weeks, with no evidence of delayed union in their series of 34 patients. The usual period of fixation for the sagitta] ramus osteotomy in our hands, however, is 6 weeks. Any clinical evidence of incom- plete healing at this point is considered the result of delayed physiological union. This occurred in 5.7 % of cases in this study, and in all but 2 cases was restricted to patients over 40 years of age. For this reason, patients over 40 now remain in fixation for 8 weeks. One female patient with delayed union at 6 weeks was only 19 years old; she also demonstrated resorption along the line of horizontal osteotomy with resultant spontaneous fracture at this site and dislocation of the condylar segment. At reoperation 12 weeks after the first procedure, delayed union at both sites

was unexplicably evident; intermaxillary fixation for 9 weeks following the second surgery resulted in good union and jaw position. This 1 patient brought the average age of those patients demonstrating delayed union down to 32.7 years (Fig. 18). This one prominent case, and several less obvious instances of delayed healing, might suggest a detri- mental role of intensive, albeit short-term, postoperative steroid therapy. J6nsson et al. (1979) have pointed out a broad area of overlap does not necessarily mean a broad area of contact between the segments, and, in fact, because of rotary angu- lation in asymmetrical cases, can actually mean less con- tact; this is a point that may well be more critical in patients over 40 years of age.

Malpositioned Condyle: The clinical significance of a real- positioned condyle is not always immediately evident after the removal of fixation. In this series, however, it did become evident in 5 cases within the first week postopera- tively. The resultant mandibular malposition was sufficient to require reoperation in 3 of these cases. In 4 of the 5 cases,

Experience with the Sagittal Osteotomy J. max.-fac. Surg. 9 (1981) 161

Fig. 22 a Fig. 22 b

Fig. 22 An instance of significant angular change following uneventful sectioning of the ramus; a) preoperative status; b) film taken 30 months postoperatively; segment rotation could not be entirely excluded as at least a partial cause of the change in gonial angulation.

the condylar displacement could be directly attributed to surgical technique in that the particulars of stabilization of the proximal segment and application of the circumferen- tial wire as described previously were not followed; the 5th case was that of the 19-year-old girl with delayed healing of obscure aetiology in which the proximal segment resorbed along the line of the horizontal osteotomy and became displaced. The incidence of postoperative temporomandibular joint noise, pain, or other dysfunction was not recorded consis- tently enough to allow legitimate conclusions. Such prob- lems have arisen to a minimal degree occasionally, but there has been no necessity for either invasive or extensive dental measures to correct such complaints. Cases of asymmetric prognathia requiring rotation for correction can result in significant lateral dislodgement of the short-side proximal segment when operated on with the sagittal ramus osteotomy. This has been demonstrated experimentally (Freihofer 1977 a). Fig. 19 describes a clinical example; this patient experienced moderate joint sounds in the left tem- poromandibular joint for several months postoperatively but did not complain of discomfort.

Bone, Scar and Wire Difficulties: In a few cases, the promi- nence of the proximal segment in the posterior buccal sulcus following healing was obtrusive enough to produce a food trap with the molar teeth and/or be a consistent point of irritation in toothbrushing, mastication, etc. In 2 cases, such prominences required subsequent surgical reduction. A similar problem arises occasionally along a fibrotic scar at the site of incision. This can generally be avoided by terminating the lower end of the incision well into the unattached mucosa away from the necks of the teeth, but can be corrected with an out-patient Z-plasty (Fig. 20). The circumferential fixation wires are routinely left in position

permanently unless they subsequently perforate the mucosa or become otherwise bothersome. In these instances, they are removed intraorally on an out-patient basis, and this has been necessary in approximately 6 % of patients.

Miscellaneous Infrequent Difficulties: Additional miscel- laneous postoperative difficulties have arisen in very small numbers, and include seromas or haematomas requiring drainage, patient difficulties in accommodating to the liquid diet, and a single case of transient facial nerve paresis (Behrman 1972, Dendy 1973). Hepatitis arose in one patient who had undergone blood transfusion because of unusual operative blood loss, and in the patient adminis- tered mismatched blood. Both cases resolved under the usual therapeutic regimen.

Bone Necrosis: Behrrnan (1972) reported resorption and necrosis of bone, and recent experimental evidence in ani- mals suggests that ischaemia in the proximal segment might account for these clinical findings (Grarnmer et al. 1974, Path et al. 1977, Bell and Schendel 1977, Grammer and Carpenter 1979). It has been suggested, on the basis of this experimental evidence, that limited elevation of the muscu- lature sufficient only to allow placement of the osteotomies, as originally described by Obwegeser (1957) and subse- quently mentioned by others (Hunsuck 1968, Epker 1977) is preferable to full relief of the soft tissues. Bell and Schendel (1977) demonstrated, in monkeys, reduced blood flow to the bone following complete strip- ping of the muscular sling; Path et al. (1977) described similar bone changes, with increased flow to the associated masticatory musculature. Grarnrner and Carpenter (1979) described necrosis of the proximal fragment following mus- cle stripping in animals. JiSnsson et al. (1979) described radiographic evidence of exaggerated decalcification in the

162 J. max.-fac. Surg. 9 (1981) R.B. Macintosh

ramal segments, but reported no evidence of associated delayed or imperfect healing; these workers attributed the decalcification to normal fracture resorption in this unusu- ally thin site, to the effects of momentary disuse atrophy because of lysis of muscle attachment or to immediately postoperative interference with blood supply. This same group described some degree of increased obtuseness in the gonial angle postoperatively in 75 % of 57 operated rami, and suggested that the changes might be due to resorption at the angle resulting from ischaemia; they also mentioned rotation of the proximal segment as a possible source of the problem. Cook and Hinrichsen (1973) also noted an increase in the gonial angle postoperatively, but attributed it to an increase in the mandibular plane angle as over- closed, prognathic mandibles were repositioned posteriorly into the proper plane of occlusion with the maxillae. Aside from the Behrrnan article, review of the literature reveals no other suggestion of clinically significant resorp- tion, necrosis, and/or malunion due to masticatory muscle stripping. Phillips and Bell's report (1978) of condylar necrosis following sagittal ramus osteotomy, without involvement of the rest of the ramus, would appear to be due to other causes, as the authors themselves suggest. In the present series, there were 2 cases of minor sequestra- tion of a portion of the proximal fragment, unquestionably due to infection. The only case of unusual resorption noted in this series was that of the 19-year-old female patient who demonstrated sufficient resorption along the line of horizontal osteotomy to separate the proximal segment at that point (Fig. 21). The author has had the opportunity to examine a patient not included in this series in whom there was an obvious clinical and radiographic flattening of the gonial angle postoperatively (Fig. 22). In light of the otherwise negative findings of this review in regard to bone resorption, necrosis, or angle change, this author assumes that the ischaemia demonstrated in animals experimentally is clinically insignificant, and that the change in gonial angle noted by J6nsson is most probably due to subtle rotation at the time of fixation, more extreme rotation effected by the muscles in cases of imperfect fixa- tion, or remodelling of the angle under the influence of the readapted musculature answering new functional demands. The apparent clinical irrelevance of any ischaemia due to muscle stripping may reflect Stringa's (1957) laboratory finding of early revascularization of ischaemic bone sur- faces. We continue to reflect the muscle and fascia com- pletely off the proximal segment and off the inferior border of the distal segment; this manoeuvre provides better visi- bility of the surgical field, more efficient and complete control of the segments at the time of placement of the fixation wires, and lysis of the disruptive effects of muscle function in the early post-operative period.

Paraesthesia: Certainly the most disturbing postoperative effect more peculiar to the ramus sagittal osteotomy than to other ramus techniques is paraesthesia. Various authors have commented on this (White et al. 1969, Dendy 1973, Wang and Waite 1974, Freihofer and Petresevic 1975, Hall et al. 1975, Bell and Schende11977, Broadbent and Woolf 1977, Pepersack and Chausse 1978). Fig. 10 describes an 85 % incidence of paraesthesia immediately postopera- tively, and a residual 9 % incidence 1 year after surgery. This is considerably less than the incidence reported by Pepersack and Chausse (1978), and may reflect our routine

use of steroids postoperatively in many patients of this series, and/or a less sophisticated method of evaluating sensibility. Sensory function was determined with a simple pin-prick method on the gingiva, lip mucosa, and lip skin with no attempt at pressure quantification or semantic qualification; the question was simply whether or not the examiner could objectively demonstrate compromised sen- sation, and/or whether the patient could describe the feel- ing as in any way abnormal. The persistence of paraesthesia 1 year postoperatively was overwhelmingly more prominent in the over-40 age group; the mean age for those patients with disturbed sensory function 12 months after surge~ was 38.6 years (Fig. 18). In one 48-year-old patient, a unilateral moderate degree of paraesthesia persisted 2 years postoperatively, at which time she was lost to follow-up. Unilateral, near-total anaes- thesia, persisted in a 44-year-old female patient, who had initially demonstrated delayed union bilaterally, when she was lost to follow-up 2 years postoperatively. Paraesthesia persists in a 20-year-old female patient unilaterally 2 years after surgery. The latter patient was i of 4 in this series who had suffered complete transection of the nerve at the time of surgery; the others regained essentially normal function within a year. It has been this author's experience that patients clearly advised preoperatively of the probability of postoperative paraesthesia both accept and adapt to the difficulty very well; nonetheless, except in cases of marked retrognathia, we no longer utilize the sagittal ramus osteotomy in patients over 40 years of age.

Relapse: Probably the most problematic issue in orthog- nathic surgery is that of relapse. The parameters for measuring regression in this study are seen in Fig. 11. The postoperative change was measured at the occlusal level millimetrically and usually at the cuspid position; in cases of obvious postoperative dental change, usually orthodon- tic, at this site, other dental reference points were chosen. The initial hope to relate postoperative linear change to original linear surgical movement proved so difficult and inconsistent in practice as to be meaningless. Review of Fig. 12 indicates an essentially similar overall relapse rate in the cases of retrognathia and prognathia in the series at the occlusal level. More careful inspection of the information, however, shows two differences of some significance: The incidence of + 3 occlusal relapse is over 4 times as common in the retrognathic patients as the prog- nathic, and 50 % of the patients with relapse in retrog- nathic cases also had a diagnosis of apertognathia. With one exception, all of the retrognathic patients with +3 relapse also demonstrated skeletal open-bite. The fact that 63.5 % of all regressive cases, prognathic and retrognathic, demonstrated skeletal apertognathia has led to our aban- donment of the sagittal osteotomy in particular, and ramus surgery, in general, for apertognathic patients with vertical discrepancies of more than 2-3 mm. The most frequently employed alternatives are total maxillary or total mandibu~ lar alveolar surgery (Macintosh 1974, 1975, 1980). In none of the cases with + 1 relapse was retreatment either surgically or orthodontically objectively necessary or requested by the patient. In several of the + 2 cases, orthodontic revision was indicated. Of the 6 patients with + 3 regression, 3 underwent subsequent corrective surgery, 1 more should have, but for various reasons could not, and

Experience with the Sagittal Osteotomy J. max.-fac. Surg. 9 (1981) ! 63

the remainder were refined through equilibration, orthodontic, and/or restorative measures to acceptable appearance and function. If one accepts at least a + 1 occlusal relapse as acceptable functionally, the remaining 11.2 % of cases with + 2 or + 3 relapse is essentially the same as the significant regression reported by Broadbent and Woolf (1977) and Pepersack and Chausse (1978), and is somewhat less than that reported by Freihofer (1975, 1977 b). Souyris (1978) found significant relapse in 2 of 18 prognathic patients in which the segments were stabilized with bone plates, and in 4 of 16 stabilized with wires. Cook and Hinrichsen (1973) reported an almost 50 % relapse rate in their series of 34 prognathic patients, in whom 5 of the 16 regressive patients demonstrated "significant compromise"; all of these patients were under 19 years of age. The role of age in relapse in the present series requires further analysis, but may be unsignificant: Only 13 % of the patients here surveyed were younger than 18 years of age (Fig. 18). Review of Fig. 11 indicates a discrepancy between the degree of occlusal relapse and cephalometric/aesthetic relapse. The criteria for change in the latter regard were differences in hard tissue pogonion, B point, and the most anterior soft tissue chin contour, in the rest position on superimposed preoperative and minimum 1-year post- operative cephalograms. The soft chin contour measure- ment is perhaps the most significant, since it represents what the patient notices; the hard tissue measurements simply substantiate or support the clinical impression. The overall most significant clinical fact drawn from this com- parison is simply that aesthetic compromise is not as fre- quently significant as is functional compromise. In no case was a profile change of more than 4 ram. noted, and while occlusal changes of more than 1 ram. ( + 2 and + 3) were evident in 11.2 % of the patients, aesthetic profile changes of more than I ram. were evident in only 2.5 % of the patients. This is in contrast to Freihofer's (1977b) finding of a general coordination between the two mo- dalities of measurement. The findings in the present series, however, are in accord with Freihofer's observation of there being no patient with radiographic regression without clini- cal regression. Egyedi (1965) calculated a higher incidence of relapse in his review of 14 prognathic cases than is seen in the present series, but emphasized the difficulties in evaluating his patients radiographically. Vijayaraghaven et al. (1974) described a relapse rate of approximately 50% in their cephalometric evaluation of 16 prognathic patients; 6 of these patients demonstrated +3 relapse by our standards and 2 of them +2; only 2 patients over 20 years of age showed any change at all. This group used horizontal alveolar level wiring of the segments and cap-splint inter- maxillary fixation; it may be that one or both of these factors contributed to the unusually high incidence of relapse. This same group was the first to describe the fact of actual condylar growth following osteotomy, a factor which cer- tainly contributed to their findings of postoperative shift. The significance of condylar growth was, not surprisingly, greater in the 14-19 year age group. Postoperative condylar growth as a factor in relapse had been originally suggested by Obwegeser (1964) and later by Egyedi (1965), referring to Trueta and Trias' work (1961). Rowe (1960) also alluded to post-surgical growth in general.

Probably the most often suggested source of relapse has been that of muscle influence (Steinhduser 1973, Wang and Waite 1974, Freihofer 1976). Obwegeser (1957), and later others, suggested that the masseter and pterygoid muscles be left intact in all but those areas where reflection is necessary for placement of the osteotomies (Hunsuck 1968, Epker 1977); Obwegeser did, however, emphasize incision of the periosteum on the inner aspect of the pterygomas- seteric sling. Total detachment of the muscles leaves the bone segments passive and free from muscle distortion in the early postoperative weeks, and, ultimately, subject to muscle function only in the new desired position; leaving an essentially intact fibromuscular apparatus, on the other hand, is less of a physiological insult, perhaps leaves the masseter and internal pterygoid muscles in a more static position postoperatively, and might therefore be less likely to distort the rearranged bony anatomy. Unfortunately, clinical proof of the validity of either argument in relation to relapse has as yet not been forthcoming. The potentially disruptive role of the suprahyoid muscula- ture, particularly in cases of retrognathia or apertognathia, has been discussed by Steinhduser (1973). He suggested myotomy of these muscles to neutralize their theoretically detrimental effect on the repositioned mandible. Steinhduser had no long-term information on his patients operated on in this fashion and did not assert, unequivoc- ally, that myotomy would reduce the tendency toward regression. To date, the literature does not indicate evidence from any source that it does. In this author's view, relapse has very little to do directly with the way in which masticatory and suprahyoid muscles are handled surgically nor does it depend directly upon the type or position of the osteotomies in the ramus. Neither does it depend, as an essential cause, upon habit or tongue function; exceptions to the latter may be causes of true skeletal apertognathia, in accord with the thinking of Prof- fitt and Norton (1970), or those patients with prognathia or retrognathia who demonstrate abnormally large ton- gues.

It is our view that the essential impetus for relapse comes from a proprioceptive drive to re-establish the preoperative dento-oro-facial environment, and that the site of most active proprioceptive stimulus is within the condylo-ramus- masticatory muscle complex; that under the influence of the proprioceptive drive, bone can be remodelled, as shown by McNeill (1973), even though the teeth remain in intermax- illary fixation; that bone can grow, as shown by Vija- yaraghaven et al. (1974); and that the tongue and other musculature can respond to the proprioceptive demands by assuming functions and taking positions to reapproximate the preoperative alignment of the teeth. The adolescent years are important in this mechanism because propriocep- rive patterns are immature at that time, jaw and muscle habits and masticatory patterns are incompletely learned, the dental occlusion is under dynamic change (particularly in orthodontic patients), bone maturation is incomplete, and residual individual growth capabilities are uncertain. Clinically, this hypothesis is supported by the recognized stability of mandibular body and alveolar procedures which do not disrupt the condylo-ramns-masticatory muscle com- plex. To date, however, this concept has not been proven, though it is presently the subject of studies at our institu- tion.

164 J. max.- fac. Surg. 9 (1981) R . B . M a c i n t o s h

It is because of the uncer ta int ies in regard to the ae t io logy of relapse that this author , as a general rule, avoids opera t ing on pat ients unti l af ter the 18th bi r thday, avoids using inter-occlusal splints wheneve r possible to achieve immedia te denta l con tac t in the new pos i t ion for wha t eve r p ropr iocep t ive effect this may have (in add i t ion to the o ther reasons a l ready recounted) , and does no t " o v e r - c o r r e c t " , because of the uncertaint ies concern ing the degree a n d / o r symmet ry of any regression, except in those cases in which o r t h o d o n t i c considera t ions necessi tate such managemen t . Early func t ion in the new occlusion, as long as stabili ty can be assured, might well have mer i t in regard to p ropr iocep- tive relearning; the results of those surgeons w h o espouse the use of bone plates, Souyris ( I978) a m o n g others , are wor thy of a t tent ion in this regard.

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