J Oral Maxillofac

SurQ

49:1081-106S,l991

,5Sc,

DDS,* AND J.M. SYMINGTON,

5DS,

SC, PHD, FDS,

Computed tomography (CT) was used postoperatively to assess the pterygomaxillary region in 12 orthognathic surgery patients who had had a Le Fort I osteotomy. Although pterygomaxillary separation was successful in afl cases, in only 41.6% of the sides did fractures of the plate not occur. The incidence of low pterygoid plate fracture was 37.5% and that of high pterygoid plate fracture was 25%; 4.2% of sides showed a maxillary tubers&y fracture. Multiple fractures were observed in 6.3% of separated plates. Of 17 pterygoid plates judged clinically to be intact, only IQ were intact as assessed by CT. The significance of these findings and application of CT to evaluation of modifications to the Le Fort I osteotomy is discussed.

detail by many authors.5-7 Increased knowledge of the basic biology of the Le Fort I osteotomy,8Z9 development of instrumentation tailored to t ation, and use of controlled hypotensive anesthesia has dramatically reduced operating time and morbidity. Complications, although UHBC(B~~QP$, ds oc-

Osteotomy at the Le Fort I level was first described by Von Langenbacb in 1859,’ years before the publications of Gubren and Le Fort. In the 1920s, Wassmund2 began to use the Le Fort I osteotomy for correction of midface deformity. At that time, horizontal osteotomies were performed in the maxilla, but the maxilla was not surgically separated from the pterygoid plates. Rather, it was pulled into the desired position using postoperative elastic traction Schuchardt and Axhausen354 later advised that the pterygomaxillary junction be separated with an osteotome, and the basic surgical technicme has bad relatively few modifications since. The Le Fort I has become a standard procedure for management of dentofacial deformities, besides providing surgical access for other operations. The versatility of this procedure has been described in

CUT.

Many of the complications of the Le Fort I osteotomy have been attributed to unfavorable dysjunction of the pterygoid plates from the posterior maxillary wall. Excessive bleeding,‘O~” cranial nerve injury, 12-14and carotid artery injury”‘-r7 have all been reported. When the Le Fort I osteotomy is performed, the bony maxillary antral walls are first cut; ,tbe nasal septum is then detached from the nasal crest of the maxilla. The only bony attachments then preventing mobilization of the maxilla are the vertical process of the palatine bone and the junction formed between the maxillary tuberosity, the pterygoid plates of the sphenoid bone, and the pyramidal pro cess of the palatine bone. This bomy fusion appears to form during adolescence, before synostosis of the spbenobasilar synchondrosis.‘8 ‘The correct PQsitioning of the curved osteotome for controlled separation of pterygomaxillary junction and a review of the regional anatomy was described by Turvey and Fonseca.i9 Sicher and Du 13ru120have described a system of reinforcing pillars in the maxilla and the pterygoid

Received from the Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, University of Toronto, and The Toronto Hospital, Toronto, Ontario, Canada. * Senior Resident. t Professor and Head. Address correspondence and reprint requests to Dr Symington: Professor and Head, Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, University of Toronto, 124 Edward St, Toronto, Ontario, M.56 I%, Canada. 0 1991 American

Association

of Oral and Maxillofacial

Sur-

geons 0278-2391191/4910-0006$3.00/O

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1062

CT STIJDY 49F PTERYGOMAXILLARY

processes. Although, hypothetically, these pillars should resist horizontal fracture of the plates during osteotomy of the pterygomaxillary junction, horizontal fractures have been observed intraoperatively and documented experimentally. Wikkeling and Koppendraaier’* performed the Le Fort I osteotomy on 11 formalin-fixed half-heads using a curved osteotome as described by Obwegeser. In seven cases, ideal junctional separation occurred. In two cases the osteotomy occurred through the maxillary tuberosity, and in two cases a near horizontal pterygoid process fracture occurred. Wikkeling and Tacoma21 then repeated the experiment using a self-designed swan neck osteotome designed to deliver a blow into the pterygomaxillary junction at a more optimal angle without the compounding interference of the soft tissues of the cheek. In 11 half-heads, 18 ideal separations occurred. A single tuberosity fracture occurred. There were no palatine neurovascuiar injuries. Each of 12 surgical patients had ideal separation, Wikkeling and Tacoma’s investigation appeared to show that unpredictable fractures of the pterygomaxillary region can occur and that their incidence is reduced with use of the swan neck osteotome. Robinson and Hendy22 argued that use of fixed cadaver heads was very different from the clinical sitTable 1.

SEPARATION

uation and therefore performed Le Fort I osteotomies on eight intact unfixed cadavers, using a curved pterygoid osteotome in the standard fashion. They observed seven plate fractures at the level of tbe osteotomy, five plate fractures above this level, and four fractures of the posterior sirms wall. On two sides, portions of the plates remained attached to the maxilla, and in only four of 16 sides was separation of the plates uncomplicated. This investigation appeared to provide evidence that the incidence of unfavorable fractures in the clinical situation may actually be higher than that shown in Wikkeling’s study of fixed specimens. The results of these investigations prompted us to document the pattern of pterygoid plate fractures in orthognathic surgical patients undergoing a Le Fort I osteotomy for correction of dentofacial deformity using computed tomography (CT). Materiak

am! Methods

A consecutive series of patients admitted to the oral surgery service for orthognathic surgery, where a Le Fort I osteotomy was one of the proposed corrective procedures was studied. The age and sex of each patient and the nature of their deformity are shown in Table 1.

Clinical Data and CT Observations

Patient

Sex/Age (Yr)

1

Ml19

2

Ml20

3

F/36

4

Ml19

5

F/23

6

M/21

7

M/21

g

F/S2

9

F/26

10

Ml23

11

Ml23

12

M/19

Abbreviations:

Deformity Asymmetry, mandibular retro Transverse discrepancy Transverse discrepancy Facial asymmetry, mandibular retro Apertognathia mandibular prognathia transverse discrepancy Apertognathia mandibular retro Apertognathia VME, mandibular retro Mandibular retro maxillary hypoplasia Asymmetry, mandibular retro Maxillary hypoplasia Asymmetry, mandibular retro

CT, computed tomography;

Retro, retrognathia;

Clinical Impression of Plates Intact Intact Intact R, low no.; L, intact Intact

Intact R, low no.; L, low no. Intact R, low no.; L, intact R, tuberosity no.; L, intact R, low no.; L, low no. R, intact; L, low no. VME, vertical maxillary excess.

CT Observation R, bigb no., L, high no. Intact R, intact; L, low no. R, intact; L, low no. R, intact; L, low no. R, low no.; L, intact R, low no.; L, low no. R, intact; L, high no. R, high no.; L, intact R, tuberosity no., high no.; L, intact R, intact; L, low no. R, low no., high no.; L, 10.~ no.

RENICK AND SYMHNGTON

During the course of each Le Fort I osteotomy, the pterygomaxillary junction was separated in a standard fashion with a curved osteotome manipulated subperiosteally from a transoral approach (Fig 1). The tip of the osteotome was inserted into the junction and malleted while a palpating finger was placed intraorally over the hamular process. The dysjunctions were performed after completion of osteotomies sf the antral walls and nasal septum and immediately before digitally downfracturing the maxilla. Between I and 7 days after surgery, CT of the head was performed with a General Electric (Milwaukee, Wl) CT 9800-Quick scanner. Images in the axial plane were taken perpendicular to the Frankfort horizontal from sella to the occlusal plane. In the coronal plane, imaging was performed with a -20” tilt and with the neck maximally extended. Views were produced from the anterior maxilla posteriorly to the foramen magnum; 3.0-mm slices were generated in both planes using an exposure of 120 kV and 178 mA for 2.0 seconds. These views replaced the postoperative plain films.

The CT observations are summarized in Table 1, along with the clinical impression of the pterygoid plate integrity at the time of surgery. In compiling the CT data, fractures of the pterygoid plate were termed BQWif they occurred inferior to the Le Fort I horizontal osteotomy and high if they occurred superior to this level. In 9 of 24 sides, low horizontal fractures were observed, an incidence of 37.5%. In 6 of 24 sides, high horizontal fractures occurred, an incidence of 25%. There was a single case of posterior tuberosity fracture (Fig 2). On two sides, multiple fractures were observed. NQ patients exhibited fractures

FIGURE i. Positicming of the curved osteotome for separation of the pterygomaxillary junction.

FIGURE 2. plates.

CT scan of IQWhorizontal fracture of the pterygoid

other than Qf the pterygoid berosity.

plates or maXillaI-y tu-

The Le Fort I osteotomy and downfracture of the maxilla offers tremendous versatility in management of dentofacid deformities. Total mobilization of the maxilla requires separation of the pterypmaxillary junction, which is usually performed with a curved osteotome introduced subperiosteally from a transoral approach. Ideal positioning of this instrument is often compromised owing to Nrestriction by the cheek OF extreme medial location of the plates. Fractures of the pterygoid plates have been implicated in many of the complications reported with this procedure. ‘*-r7 Although extensive fractures Q$ the pterygoid plates and abberant separation of the plates from the posterior maxilla have been observed in cadaver studies,1s~21122the pattern offracture and dysjunction in surgical patients does not appear to have been dobumented. This study shows that efforts to initiate ideal separation of the pterygomaxillary junction are usually unsuccessful. Although the junction was separatedin allc%ses,in most patients fractures of the plates could be documented by CT scan. Many of these fr&tures were’ not appreciated clinically at the time ofsurgery. Of 17 plates judged to be intact at surgej, only 108 were observed to be intact by CT. The’integrify of the plates during surgery therefore should not ex-

1064

FIGURE 3.

CT STUDY OF PTERYGGMAXILLARY

CT scan of posterior tuberosity fracture.

elude plate fracture as a contributing factor in unexplained postoperative complications. The surprisingly high incidence of fractures of the pterygoid plate during separation of the pterygomaxillary junction observed in this study (58.4%) is similar to the results of Robinson and Hendy.22 In their experiments, using an identical separation technique, but in unfixed cadavers, separation was complicated in 75% of cases. Research using fixed specimens, published by Wikkeling and Tacoma,” yielded a much lower incidence of unfavorable separation and may not simulate the clinical situation. The difficulty in reaching the pterygomaxillary junction and directing an osteotome in the most ideal direction has been recognized for years and has led to a number of modifications of the technique proposed by Obwegeser.’ Dupont and colleagues ( 1974)23 using a transbuccal approach with a 2-mm osteotome, performed a vertical osteotomy through the maxillary tuberosity rather than attempting to separate the pterygoid plates. Trimble and associates” described a similar vertical osteotomy from an intraoral approach using straight or curved osteotomes. In neither of these publications

SEPARATION

were results of the modified techniques discussed in detail. Wikkeling and Tacoma21 in fixed cadavers and in surgical patients, appear to have obtained evidence that the incidence of unfavorable separatisn of the pterygomaxillary junction could be reduced using the swan’s neck osteotome. Hisanuma and coworkers2’ compared the strain distribution in dry skulls when the pterygoid plates were separated using either the Obwegesser osteotome or the swan’s neck osteotome. Strain was consistently less -using the latter instrument. The authors further emphasized the need to angle the tip of either osteotome anteroinferiorly to avoid posterssuperior compression of the pterygoid plates. Separation of the pterygomaxillary junction depends greatly on technique. Recently, Precious and colleagues26 described a method in which the pterygoid plates are separated from the posterior maxilla using Tessier distraction forceps applied initially at the periform rims and then later at the maxillary tuberosity, rather than an osteotome. IJncomplicated separation, as assessed clinically, was reported to have occurred in more than 508 patients. These patients were not subjected to postoperative CT assessment, however. The findings of the present study indicate that pterygomaxillary dysjunction using the classic technique is often complicated by fractures of the pterygoid plate. Many of these fractures are rmf recognized at the time of surgery bent can be documented by CT scan. Use of the swan neck osteotome and the technique described by Precious and colleagues 26 deserve further evaluation by postoperative CT imaging. Although the Ee Fort I osteotomy has proven a relatively safe operation, a refinement of the pterygomaxillary dysjunction technique may further reduce the incidence or severity of intraoperative complications. References 1. Langenbeck BV: Beitrage zur Osteoplastik-Die Osteoplastische Resektion des Oberkiefers, in Goshen A led): Deutsche Klinik. Reimer, Berlin, 1859 2. Wassmund RI: Lehrbuch der prakteschen Chirugie des Mundes und der Kiefer. Barth, Liepzig, 1939 3. Schuchardt K: Ein Beitrag zur chirurgischen Kieferorthopadie unter Berucksichtigung ihrer Bedeutung fur die Behandlung angeborener und erworbener Kiefudeformitaten bei Soldaten. Dtsch Zahn-Mund-u Kieferheilkd 9~7’3,1942 4. Axhausen G: Zur Behandlung veraheter disloziert verheilter Oberkieferbruche. Dtsch Zahn Mund-u Kieferheilkd 1:334, 1934 5. Obwegeser HL: Surgical correction of smah or retrodisplaced maxilla. The “dish-face deformity.” Plast Reconst Surg 43:351, 1969 6. Bell W, Profftt W, White R: Surgical Correction of Dento-

D.S. PRECHQUS

7.

8.

9. 10.

11.

12.

13.

14.

15.

facial Deformities, vols 1 and 2. Philadelphia, Saunders, 1980 Bell WH, Manna1 C, Luhr HG: Art and science of the Le Fort I downfracture. Int J Adult Orthod Orthognath Surg 1:23, 1988 Bell WH, Fonseca RI, Kennedy JW, Levy BM: Bone healing and revascularization after total maxillary osteotomy. J Oral Surg 33:253, 1975 Epher BN: Vascular considerations in orthognathic surgery: II. Maxillary osteotomies. Oral Surg 57:473, 1984 Newhouse RF, Schow SR, Kraut RA, Price JC: Lifethreatening hemorrhage from a Le Fort I osteotomy. J Oral Maxillofac Surg 40: 117, 1982 Reaume CE, MacNicol IBM: Complications encountered during Le Fort I osteotomy in a patient with mandibulofacial dysostosis. J Oral Maxillofac Surg 461003, 1988 Watts PG: Unilateral abducent nerve palsy: Rare complication following a Le Fort I maxillary osteotomy. Br J Oral Maxillofac Surg 22:212, 1984 Weiner S, Willoughby JH: Transient abducens nerve palsy folIowing a Le Fort I Maxillary osteotomy: Report of a case. 5 Oral Maxillofac Surg 46:699, 1988 Tomasette BJ, Broutas M, Gormley M, Jarrett W: Lack of tearing after Le Fort I osteotomy. J Oral Surg 34:1095, 1976 Lanigan DT, Tubman DE: Carotid-cavernous sinus fistula following Le Fort I osteotomy. J Oral Maxillofac Surg 45:969, 1987

J Oral Maxillofac 49:1065-1066,

16. Habal MB: A carotid cavernous sinus fistula after maxillary osteotomy. Plast Reconstr Surg 77:981, 1986 17. Lanigan DT: Injuries to the internal carotid artery following orthognathic surgery. Int J Adult Orslaod Grthognath Surg 4:215, 1988 18. Wikkeling OME, Koppendraaier J: In vitro studies on lines of osteotomy in the pterygoid region. J Maxillofac Surg 1:209, 1973 19, Turvey TA, Fonseca RJ: The anatomy of the internal maxillary artery in the pterygopalatine fossa: Its relationship to maxillary surgery. 9 Oral Surg 3892, 1980 20. Sicher H, Du Brul L: Oral Anatomy. St Louis, Mosby, 1970 21. Wikkeling OME, Tacoma 9: Osteotomy of the pterygomaxillary junction. Int J Oral Surg 4~99~1975 22. Rob&on PP, Hendy CW: Pterygoid plate fractures caused by the Le Fort I osteotomy. Br J Gral Maxillofac Surg 24:19x, 1986 23. DuPont C, Ciaburro II, Prevost Y: Simplifying the Le Fort I type of maxillary osteotomy. Plast Reconstr Surg 54:149, 1974 24. Trimble LD, Tideman H, Steelinga PJW: A modification of the pterygoid plate separation-in low level maxillary osteotomies. .I Oral Maxillofac Sure 41544. 1983 25. Hiranuma Y, Yamamoto Y, Iizuko~Stram distribution during separation of the pterygomaxillary suture by osteotomes. J Cranio Maxillofac Surg 16~13, 1988 26. Precious DS, Morrison A, Ricard D: Pterygomaxillary separation without the use of an osteotome. J Gral Maxillofac Surg 49:98, 1991

Surg

1991

Discussion Postaperatire Computed Tomography Study of Pterygomaxillary Separation During the ke Fort I Osteotomy D.S. Precious, IDS, Msc, FRCD Dalhousie

University, Halifax, Nova Scotia

This article describes the incidence and anatomic pattern of pterygoid plate fractures in 12 patients who underwent Le Fort I osteotomy. The fractures were diagnosed using computed tomography (CT) scans that were taken no later than 7 days postsurgery. The authors report 15 fractured pterygoid plates from a total of 24 operated sides. The article is interesting for three main reasons: the observed high incidence of unwanted fractures of the pterygoid plates, tbe use of postoperative CT scans to make the diagnosis of the fractures, and the fact that many of the fractures that were evident on CT scans were not recognized at surgery. Implicit in the article is the conclusion that fractured pterygoid plates cause intraoperative complications. Robinson and Hendy’ reported an even higher rate of fracture of the pterygoid plates (12 fractured plates in 16 operated sides) in their study of Le Fort I osteotomies in eight fresh cadavers, the surgical technique of which was very similar with that used by Drs Renick and Symington. Although fractured pterygoid plates have been implicated

as the cause of both severe hemorrhage and nerve injury, the frequency of these complications is much lower than that of fracture. The authors state that “separation of the pterygomaxillary junction is very technique dependent” but no reference is given to comparative studies that actually document the superiority of one technique over anotber. Furthermore, Drs Renick and Symington seem to suggest, based on an article by Hiranuma et aL2 .that use of the swan’s neck chisel may be superior to use of the Obwegeser osteotome. In fact, Hiranuma reported, “Since no statistically significant difference was found between the mean values of the two groups, accidental fractures are likely to occur at final separation regardless of the type of osteotome used.” In our clinical experience, we have abandoned the use of a pterygomaxillary osteotome because we have found that it is not necessary to achieve pterygomaxihary separation.3 I believe it is reasonable to assume that some unwanted fractures of the pterygoid plates that go unrecognized at surgery occur with this technique, but the clinical significance (df this remains unclear. The patient sample in this study is extremely small. For this reason, one must guard against making a direct causal relationship between fractured pterygoid plates and intraoperative complications or even postoperative complications. Seversal questions remain to be answered: ¶. Is the use or nonuse of a pterygoid chisel the cause of fractured pterygoid plates?