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Pterygoid plate fractures caused by the Le Fort I osteotomy
British Jourrd of Ord and Mruillofuciul 0 1986 The British Association of Oral
PTERYGOID
PLATE
Surgcr-y (1986) 24, 198-202 and
Maxillofacial
FRACTURES
Surgeons
CAUSED
BY
THE
LE
FORT
I
OSTEOTOMY P. P. ROBINSON and Department
C. W.
of Oral Surger:,!, John
HENDY
Radcliffe
Hospital,
Oxford
Summary. Le Fort 1 ostcotomies have been carried out on eight cadavers to dctcrmine whether pterygomaxillary dysjunction with a curved chisel causes fractures of the pterygoid plates. Fractures occurred on I2 of the I6 sides. wcrc either at the lcvcl of the osteotomy cut or near to the hasc of the skull. and were sometimes multiple. There was no apparent correlation between the presence. type or extent of pterygoid plate fracture and whether or not that side of the ostcotomy was completed first.
Introduction The standard technique used for Le Fort I osteotomy requires the separation of the maxillary tuberosities from the pterygoid plates by striking a curved chisel placed in the pterygomaxillary fissure (Bell et cd., 1980). Using this method it seems unlikely that uncomplicated separation of the maxilla from the pterygoid plates would always occur as the angulation of the chisel in relation to the pterygomaxillary fissure is unfavourable and results in force being exerted in a posterior direction on the pterygoid plates. Fractures of the pterygoid plates and subsequent disruption in the pterygopalatine fossa may be responsible for some of the complications which can occur during this operation, such as severe haemorrhage (Turvey & Fonseca, 1980: Newhousc (‘I a/., 1082: Lanigan & West, 1984) or unexplained nerve injury (Tomasetti er al., 1976; Watts, 1984). A study carried out on cadavers by Wikkeling and Koppendraaier (1973) suggested that pterygoid plate fractures do occur but their investigation was performed on fixed, hemisected heads after dividing the cheek tissue to gain access: somewhat different from the clinical situation. We have therefore carried out a further study using intact, unfixed cadavers to establish whether. as intended, the pterygoid plates remain intact and attached to the base of the skull. Methods A Le Fort 1 level osteotomy was carried out on eight intact, unfixed cadavers. The ages of the cadavers ranged from 2&82, four having an almost complete upper dentition and four being edentulous (Table 1). A standard osteotomy technique was used; a mucoperiosteal flap was raised in the buccal sulcus between the molar region and the midline on both sides, the lateral wall of the maxilla was cut with a bur and the nasal septum and lateral nasal walls were sectioned with a chisel. Care was taken to ensure that these bone cuts were complete before separation of the maxilla from the pterygoid plates. A curved pterygoid chisel (Fig. 1) was placed in the pterygomaxillary fissure with the upper edge of the blade at the level of the bur cut, the instrument parallel to the occlusal plane and the handle as far laterally as the oral commissure would allow. Sharp taps were applied to the osteotome with a mallet until the blade could be felt by a finger palpating on the palatal aspect.
199
In half of the cadavers the left side was completed first and in the other half the right side was completed first. The maxilla was then downfractured and mobilised using finger pressure only. In five specimens the maxilla and pterygoid region was carefully excised, the soft tissues removed by maceration in water at 65°C for 7 days and the bone fragments examined. In the other three specimens the pterygoid plates were examined by careful removal of the soft tissues in situ. Results
The results are summarised in Table I. The pterygoid plates were completely separated from the maxillary tuberosity on 14 of the 16 sides, the other two having small fragments of the medial and lateral plates still attached. The pterygoid plates remained completely intact and attached to the base of the skull on only 4 of the 16 sides, the plates being fractured into two or more fragments on the other 12 sides. The pterygoid plate fractures could be divided into two groups; those which occurred at the level of the osteotomy cut (low level fractures; Fig. 2A) and those which occurred at or near to the base of the skull (high level fractures; Fig. 2B). There were seven low level fractures and five high level fractures. In three specimens there were two or more fractures passing through the pterygoid plates.
200
BRIrISH
JOURNAL
OF
ORAL
&
MAXILLOFACIAL
SURGERY
Table I No
Age
I
68
Dentate
2
78
_
3
x2
_
3
41
+
5
67
_
6
49
+
7
53
+
8
“Side
20
of obteotomy
+
complctcd
Side
Maxilla completely separate from pterygoid plates
L.’ R L R-’ L’ R L R’ L R” L., R L R L* R
+ + + + + + + _ + + + + + + +
Pterygoid plates intact
High level fractures
Low level fractures
_ _
_ -
+ + + -
+ _ _ _
_ + + _ + _ _
+ _ + _ + + _ + _ _ -
+ + _ _ _ _ + +
Multiple fractures
_ + + _ _ + _ _ _
_ _ _
first.
dividing them into several fragments (e.g. Fig. 2A). Four specimens also revealed additional fractures on the posterior wall of the maxillary sinus (Fig. 2A). There was no apparent correlation between the presence, type or extent of pterygoid plate fracture and whether or not that side of the osteotomy was completed first. Discussion This investigation shows that separation of the maxillary tuberosity from the pterygoid plates with a chisel during a Le Fort I osteotomy gives rise to extensive fractures of the pterygoid plates. The most notable difference between our results and those of the previous cadaver study of Wikkeling and Koppendraaier (1973) using fixed hemisected heads was the much higher incidence of pterygoid plate fractures in our specimens. We presume that this is due to differences between the resultant forces applied in fixed hemisected cadaver heads and in the unfixed intact specimens which we have used. Although several of the cadavers were elderly and edentulous and might have been expected to respond to pterygo-maxillary dysjunction in a different way from young dentate cadavers, we did not find this to be the case. We found that the fractures could be divided into those which occurred at the level of the osteotomy cut and those which occurred at a higher level, near to the base of the skull, but the positron and extent of the fractures was not consistent or related to the side of the osteotomy which was completed first. This inevitably makes this part of the operation unpredictable in its effect. Our results would appear to be important in several respects. First, if fragments of the pterygoid plates and their attached muscles are drawn forward with an anteriorly repositioned maxilla, it seems likely that this would contribute to
PTERYGOID
PLAI
Fig.
E
FRACTURES
2
Figure 2 (A)-A diagram of the pterygoid plate lracturcs in one spccimcn. These fractures wcrc at the lcvcl of the ostcotomy cut (low lcvcl fractures) and divided the pterygoid plates into several fragments. Additional fracture lines were seen in the posterior wall of the maxillary sinus. (B) A diagram of the pterygoid plate fractures in a specimen in which they occurred at a higher level than the osteotomy cut (high Icvel fractures).
BRITISH
202
JOURNAL
OF
ORAL
&
MAXILLOFACIAI.
SURGEKY
post-operative relapse. Secondly, the practise of inserting a bone graft into the space created between the maxillary tuberosity and the pterygoid plates to stabilise the fragments (Obwegeser, 1969) would seem to have little foundation if the pterygoid plates are themselves freely mobile. Thirdly, and most importantly, the unpredictable nature of the fractures which may extend to the base of the skull makes the occurrence of complications likely. A case of life-threatening haemorrhage from Le Fort 1 osteotomy has been attributed to laceration of the internal carotid artery by a sharp bony fragment from detached pterygoid plates (Newhouse et al., 1982). Many other cases of severe post-operative haemorrhage requiring transfusion were recently reviewed by Lanigan and West (1984) and were attributed largely to damage to the internal maxillary artery during pterygoid plate separation. Loss of lacrimal gland function in a case reported by Tomasetti et a/. (1976) and unilateral abducent nerve palsy reported by Watts (1984) were also both attributed to trauma during pterygoid plate separation. How may these complications be avoided? Turvey and Fonseca (1980) emphasise the use of a careful technique, ensuring that the lower edge of the chisel is at the bottom of the pterygomaxillary fissure and that the chisel is not directed superiorly. Two alternative approaches have, however, been proposed. Wikkeling and Tacoma (1975) designed a ‘Swan’s neck’ shaped chisel which allows force to be transmitted in a posterolateral to anteromedial direction whilst the curved handle of the instrument accommodates the cheek. They carried out a trial on cadavers with this instrument, using fixed hemisected heads as in their previous study. and reported encouraging results. Others have suggested that the pterygomaxillary fissure should be avoided by making the posterior osteotomy cut through the maxillary tuberosity using a chisel inserted either through the cheek (DuPont ef al.. 1974) or intra-orally (Trimble er ml., 1983). Our results would suggest that thcsc alternative approaches are likely to be preferable to the standard technique.
Bell. W. H.. Proffit. W. R. & White. R. P. (I%(l). .Surg/cdC‘ otwc~/ior~ o/‘Denr~~ucrn/ Oc/hrmi/rrv. Vol. Philadelphia & London: Saunders. I.. pp. 2X1-287. DuPont, C., Ciaburro. H. & Prevost, Y. (1974). Simplifying the Lc Fort I type of maxillary osteotomy. Plu.sric ud Rccorz~mtc/i~~~ .Surgwy. 54, 142. Lanigan. I>. T. Kr West. R. A. (IY83). Management 01 postoperatl\c hemorrhage following the Le Fort I maxillary ostcotomy. Jowd or Orul urd ,Masdlofuc~icrl Sutpr~. 42, 167. Newhouac. R. F.. Schow. $G.R.. Kraut, R. A. & Price, J. C. (lYX2). Life-thrcatcning hemorrhage l’l-on1 a Le Fort I oateotomy. Jourmd of Ord and Muxillo/titicrl Sur,qcrv, 40, I 17. Obwegeser, 11. L. (IY6Y). Surgical correction 01 small or rctrodisplaccd maxilla. ‘I‘hc “dish-face” 43, 35 I deformity. f/rr.\lic, end R~,~o/l.crr[lc,rril,P Surgery. Tomasctti. B. J.. Brontsah. M.. Gormley. M. K: Jarrctt. W. (lY76). I.ack OC tearing alter Lc Fort I ostcotomy. Jourr~ul “/ Ord Surgcvy. 34. IOYS. Trimhlc. L. D.. ‘Tideman. H. Kr Stoelinga. P. J. W. (IYX.7). A modification of the ptcrygoid plate separation in low-lcvcl maxillary ostcotomles. Jorrrrd (!I Or-d md Ma.ri//o/i~iu/ .S~wgcry. 41, 541. T. A. Cy: Fonscca, K. J. (IYXO). The anatomy 01 the internal maxillary artcry in the Turvcy. ptcrygopalatinc l'ossa: its relationship to maxillary aurgcry. Joumul o/’ Or-u/ .Surgcrv. 3X. Y2. Watts. P. G. (10X3). Unilateral abducent ncrvc palsy: ;I rare complication lollowing a Lc Fort I maxillary ostcotomy. Rrdth Jourd of Oral md Muillo/ncicrl S’~r~cr~‘. 22. 2 12. Wikkeling. 0. M. E. & Koppendraaier. J. (1973). In vitro \tudtc\ on lint\ of odcotom! in the ptcryfold i-cgion. .Jourd of .Mtr.vrllo/kirrl Sur,cyrJ. I, 2OY. Wikkcling. 0. M. E. & l’;lconl;~. J. ( 1075). O\tcotomy 01 the pt~rygom;lwlllaI_v junctmn. /ti/ermdiod Jourtwl
or Owl
.Sur,fyr~.
4. YY.
PTERYGOID
PLATE
Surgcr-y (1986) 24, 198-202 and
Maxillofacial
FRACTURES
Surgeons
CAUSED
BY
THE
LE
FORT
I
OSTEOTOMY P. P. ROBINSON and Department
C. W.
of Oral Surger:,!, John
HENDY
Radcliffe
Hospital,
Oxford
Summary. Le Fort 1 ostcotomies have been carried out on eight cadavers to dctcrmine whether pterygomaxillary dysjunction with a curved chisel causes fractures of the pterygoid plates. Fractures occurred on I2 of the I6 sides. wcrc either at the lcvcl of the osteotomy cut or near to the hasc of the skull. and were sometimes multiple. There was no apparent correlation between the presence. type or extent of pterygoid plate fracture and whether or not that side of the ostcotomy was completed first.
Introduction The standard technique used for Le Fort I osteotomy requires the separation of the maxillary tuberosities from the pterygoid plates by striking a curved chisel placed in the pterygomaxillary fissure (Bell et cd., 1980). Using this method it seems unlikely that uncomplicated separation of the maxilla from the pterygoid plates would always occur as the angulation of the chisel in relation to the pterygomaxillary fissure is unfavourable and results in force being exerted in a posterior direction on the pterygoid plates. Fractures of the pterygoid plates and subsequent disruption in the pterygopalatine fossa may be responsible for some of the complications which can occur during this operation, such as severe haemorrhage (Turvey & Fonseca, 1980: Newhousc (‘I a/., 1082: Lanigan & West, 1984) or unexplained nerve injury (Tomasetti er al., 1976; Watts, 1984). A study carried out on cadavers by Wikkeling and Koppendraaier (1973) suggested that pterygoid plate fractures do occur but their investigation was performed on fixed, hemisected heads after dividing the cheek tissue to gain access: somewhat different from the clinical situation. We have therefore carried out a further study using intact, unfixed cadavers to establish whether. as intended, the pterygoid plates remain intact and attached to the base of the skull. Methods A Le Fort 1 level osteotomy was carried out on eight intact, unfixed cadavers. The ages of the cadavers ranged from 2&82, four having an almost complete upper dentition and four being edentulous (Table 1). A standard osteotomy technique was used; a mucoperiosteal flap was raised in the buccal sulcus between the molar region and the midline on both sides, the lateral wall of the maxilla was cut with a bur and the nasal septum and lateral nasal walls were sectioned with a chisel. Care was taken to ensure that these bone cuts were complete before separation of the maxilla from the pterygoid plates. A curved pterygoid chisel (Fig. 1) was placed in the pterygomaxillary fissure with the upper edge of the blade at the level of the bur cut, the instrument parallel to the occlusal plane and the handle as far laterally as the oral commissure would allow. Sharp taps were applied to the osteotome with a mallet until the blade could be felt by a finger palpating on the palatal aspect.
199
In half of the cadavers the left side was completed first and in the other half the right side was completed first. The maxilla was then downfractured and mobilised using finger pressure only. In five specimens the maxilla and pterygoid region was carefully excised, the soft tissues removed by maceration in water at 65°C for 7 days and the bone fragments examined. In the other three specimens the pterygoid plates were examined by careful removal of the soft tissues in situ. Results
The results are summarised in Table I. The pterygoid plates were completely separated from the maxillary tuberosity on 14 of the 16 sides, the other two having small fragments of the medial and lateral plates still attached. The pterygoid plates remained completely intact and attached to the base of the skull on only 4 of the 16 sides, the plates being fractured into two or more fragments on the other 12 sides. The pterygoid plate fractures could be divided into two groups; those which occurred at the level of the osteotomy cut (low level fractures; Fig. 2A) and those which occurred at or near to the base of the skull (high level fractures; Fig. 2B). There were seven low level fractures and five high level fractures. In three specimens there were two or more fractures passing through the pterygoid plates.
200
BRIrISH
JOURNAL
OF
ORAL
&
MAXILLOFACIAL
SURGERY
Table I No
Age
I
68
Dentate
2
78
_
3
x2
_
3
41
+
5
67
_
6
49
+
7
53
+
8
“Side
20
of obteotomy
+
complctcd
Side
Maxilla completely separate from pterygoid plates
L.’ R L R-’ L’ R L R’ L R” L., R L R L* R
+ + + + + + + _ + + + + + + +
Pterygoid plates intact
High level fractures
Low level fractures
_ _
_ -
+ + + -
+ _ _ _
_ + + _ + _ _
+ _ + _ + + _ + _ _ -
+ + _ _ _ _ + +
Multiple fractures
_ + + _ _ + _ _ _
_ _ _
first.
dividing them into several fragments (e.g. Fig. 2A). Four specimens also revealed additional fractures on the posterior wall of the maxillary sinus (Fig. 2A). There was no apparent correlation between the presence, type or extent of pterygoid plate fracture and whether or not that side of the osteotomy was completed first. Discussion This investigation shows that separation of the maxillary tuberosity from the pterygoid plates with a chisel during a Le Fort I osteotomy gives rise to extensive fractures of the pterygoid plates. The most notable difference between our results and those of the previous cadaver study of Wikkeling and Koppendraaier (1973) using fixed hemisected heads was the much higher incidence of pterygoid plate fractures in our specimens. We presume that this is due to differences between the resultant forces applied in fixed hemisected cadaver heads and in the unfixed intact specimens which we have used. Although several of the cadavers were elderly and edentulous and might have been expected to respond to pterygo-maxillary dysjunction in a different way from young dentate cadavers, we did not find this to be the case. We found that the fractures could be divided into those which occurred at the level of the osteotomy cut and those which occurred at a higher level, near to the base of the skull, but the positron and extent of the fractures was not consistent or related to the side of the osteotomy which was completed first. This inevitably makes this part of the operation unpredictable in its effect. Our results would appear to be important in several respects. First, if fragments of the pterygoid plates and their attached muscles are drawn forward with an anteriorly repositioned maxilla, it seems likely that this would contribute to
PTERYGOID
PLAI
Fig.
E
FRACTURES
2
Figure 2 (A)-A diagram of the pterygoid plate lracturcs in one spccimcn. These fractures wcrc at the lcvcl of the ostcotomy cut (low lcvcl fractures) and divided the pterygoid plates into several fragments. Additional fracture lines were seen in the posterior wall of the maxillary sinus. (B) A diagram of the pterygoid plate fractures in a specimen in which they occurred at a higher level than the osteotomy cut (high Icvel fractures).
BRITISH
202
JOURNAL
OF
ORAL
&
MAXILLOFACIAI.
SURGEKY
post-operative relapse. Secondly, the practise of inserting a bone graft into the space created between the maxillary tuberosity and the pterygoid plates to stabilise the fragments (Obwegeser, 1969) would seem to have little foundation if the pterygoid plates are themselves freely mobile. Thirdly, and most importantly, the unpredictable nature of the fractures which may extend to the base of the skull makes the occurrence of complications likely. A case of life-threatening haemorrhage from Le Fort 1 osteotomy has been attributed to laceration of the internal carotid artery by a sharp bony fragment from detached pterygoid plates (Newhouse et al., 1982). Many other cases of severe post-operative haemorrhage requiring transfusion were recently reviewed by Lanigan and West (1984) and were attributed largely to damage to the internal maxillary artery during pterygoid plate separation. Loss of lacrimal gland function in a case reported by Tomasetti et a/. (1976) and unilateral abducent nerve palsy reported by Watts (1984) were also both attributed to trauma during pterygoid plate separation. How may these complications be avoided? Turvey and Fonseca (1980) emphasise the use of a careful technique, ensuring that the lower edge of the chisel is at the bottom of the pterygomaxillary fissure and that the chisel is not directed superiorly. Two alternative approaches have, however, been proposed. Wikkeling and Tacoma (1975) designed a ‘Swan’s neck’ shaped chisel which allows force to be transmitted in a posterolateral to anteromedial direction whilst the curved handle of the instrument accommodates the cheek. They carried out a trial on cadavers with this instrument, using fixed hemisected heads as in their previous study. and reported encouraging results. Others have suggested that the pterygomaxillary fissure should be avoided by making the posterior osteotomy cut through the maxillary tuberosity using a chisel inserted either through the cheek (DuPont ef al.. 1974) or intra-orally (Trimble er ml., 1983). Our results would suggest that thcsc alternative approaches are likely to be preferable to the standard technique.
Bell. W. H.. Proffit. W. R. & White. R. P. (I%(l). .Surg/cdC‘ otwc~/ior~ o/‘Denr~~ucrn/ Oc/hrmi/rrv. Vol. Philadelphia & London: Saunders. I.. pp. 2X1-287. DuPont, C., Ciaburro. H. & Prevost, Y. (1974). Simplifying the Lc Fort I type of maxillary osteotomy. Plu.sric ud Rccorz~mtc/i~~~ .Surgwy. 54, 142. Lanigan. I>. T. Kr West. R. A. (IY83). Management 01 postoperatl\c hemorrhage following the Le Fort I maxillary ostcotomy. Jowd or Orul urd ,Masdlofuc~icrl Sutpr~. 42, 167. Newhouac. R. F.. Schow. $G.R.. Kraut, R. A. & Price, J. C. (lYX2). Life-thrcatcning hemorrhage l’l-on1 a Le Fort I oateotomy. Jourmd of Ord and Muxillo/titicrl Sur,qcrv, 40, I 17. Obwegeser, 11. L. (IY6Y). Surgical correction 01 small or rctrodisplaccd maxilla. ‘I‘hc “dish-face” 43, 35 I deformity. f/rr.\lic, end R~,~o/l.crr[lc,rril,P Surgery. Tomasctti. B. J.. Brontsah. M.. Gormley. M. K: Jarrctt. W. (lY76). I.ack OC tearing alter Lc Fort I ostcotomy. Jourr~ul “/ Ord Surgcvy. 34. IOYS. Trimhlc. L. D.. ‘Tideman. H. Kr Stoelinga. P. J. W. (IYX.7). A modification of the ptcrygoid plate separation in low-lcvcl maxillary ostcotomles. Jorrrrd (!I Or-d md Ma.ri//o/i~iu/ .S~wgcry. 41, 541. T. A. Cy: Fonscca, K. J. (IYXO). The anatomy 01 the internal maxillary artcry in the Turvcy. ptcrygopalatinc l'ossa: its relationship to maxillary aurgcry. Joumul o/’ Or-u/ .Surgcrv. 3X. Y2. Watts. P. G. (10X3). Unilateral abducent ncrvc palsy: ;I rare complication lollowing a Lc Fort I maxillary ostcotomy. Rrdth Jourd of Oral md Muillo/ncicrl S’~r~cr~‘. 22. 2 12. Wikkeling. 0. M. E. & Koppendraaier. J. (1973). In vitro \tudtc\ on lint\ of odcotom! in the ptcryfold i-cgion. .Jourd of .Mtr.vrllo/kirrl Sur,cyrJ. I, 2OY. Wikkcling. 0. M. E. & l’;lconl;~. J. ( 1075). O\tcotomy 01 the pt~rygom;lwlllaI_v junctmn. /ti/ermdiod Jourtwl
or Owl
.Sur,fyr~.
4. YY.