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sensory nerve disturbance following le fort i osteotomy
Copyright 9 Munksgaard 1996
Int..L Oral Maxillofac. Surg. 1996; 25:13-19 Printed in Denmark. All rights reserved
InternationalJournalof
Ord &
MaxillofacialSurgery ISSN 0901-5027
Aestheticand reconstructivesurgery
Sensory nerve disturbance following Le Fort I osteotomy
O. E Shehab AI-Din 1, K.M. Coghlan 2, P. Magennis s 1joint Department of Oral and Maxillofacial Surgery, Eastman Dental and University College Hospitals, London; 2Department of Oral and Maxillofacial Surgery, Royal Hospitals Trust, London; aDepartment of Oral and Maxillofacial Surgery, London Hospital Medical College Dental Institute, London, UK
O. F. Shehab Al-Din, K. M. Coghlan, P. Magennis: Sensory nerve disturbance following Le Fort I osteotomy. Int. J. Oral Maxillofac. Surg. 1996; 25: 13-19. 9 Munksgaard, 1996 Abstract. This study assessed sensory nerve disturbance after Le Fort I osteotomy using the electric pulp test, pin-prick sensation, fine touch, and cold sensation. After 6 months, 78% of teeth positive preoperatively to an electric pulp tester regained sensitivity. Return of palatal sensation was affected by whether or not the greater palatine nerve (GPN) was divided during surgery. After 6 months, where the G P N was intact, all patients had fine touch sensation (88% at the preoperative level), and all had pin-prick sensation (97% at preoperative level). When the G P N was divided, all patients had fine touch sensation (13% at preoperative level), and all had pin-prick sensation (63% at preoperative level). The differences in the return to preoperative sensation were significant for fine touch (P=0.0001) and for pin-prick (P=0.03) by chi-square analysis. Sensation returned more quickly and more completely in the two cases where the contralateral G P N was intact. In the buccal mucosa, 95% of patients regained some fine touch sensation after 6 months, but none returned to the preoperative level. Similarly, 85% regained some pin-prick sensation, but none achieved preoperative levels. Cold sensation, pin-prick sensation, and fine touch on the face returned to the preoperative level in all patients by 6 weeks postoperatively.
The Le Fort I maxillary osteotomy was first performed by CHEEVER in 1867 to provide surgical access to a nasopharyngeal tumour 15. The main role of the Le Fort I osteotomy today is in the management of dentofacial deformity. The downfracture technique has gained wide acceptance, and it is now the most frequently performed midface osteotomy. During Le Fort I osteotomy, the nasopalatine nerve; the anterior, middle, and posterior superior alveolar nerves; and the small terminal nerves in the buccal mucosa along the incision line between the upper first molars are always divided. This loss of continuity is further increased by moving the fragment in horizontal and vertical planes.
Movement may also stretch or divide the greater palatine nerves, or they may be electively sectioned to facilitate larger movements. The infraorbital nerve may be injured indirectly by pressure, retraction, or fixation with plates or screws. The sensory nerve supply of the maxilla and face is provided solely by the maxillary division of the trigeminal nerve (except the anterior part of the nasal septum and the lateral nasal wall supplied by the first division). It is surprising that patients do not more frequently complain of numbness after surgery which divides so many branches of the maxillary division. Animal studies 4 have shown that the trigeminal nerve is not the only source of sensation
Key words: osteotomy; Le Fort I; sensory deficit. Accepted for publication21 June 1995
in these areas. DENNY-BRoWN & YANAhave demonstrated the importance of the descending trigeminal tract in modifying the intensity of sensation in any one part of the trigeminal or cervical segments. The purpose of this study was to assess prospectively the sensory morbidity associated with the Le Fort I osteotomy and record any recovery of sensation over a period of 6 months. GISAWA4
Material and methods
Twenty adults (15 women and five men, average age 25 years (range 18-42 years)) undergoing bimaxillary surgery involving Le Fort I downfracture of the maxilla were entered into the study. They were consecutive cases treated in the unit over 6 months.
14
A l - D i n et al.
Modalities of sensation tested included fine touch, pin-prick, and cold. All sensory testing was carried out by a single operator (O.ES.A.) preoperatively, at 2 days, 6 weeks, 3 months, and 6 months postoperatively. Preoperative testing allowed direct comparison to be made, with patients acting as their own control. In an attempt to avoid bias during the postoperative tests, patients were not asked about any subjective loss of sensation; they were asked only to cooperate with the examination.
Surgical procedure Surgery was performed by two consultant surgeons. With a standard upper buccal sulcus incision from the maxillary left first molar to the maxillary right first molar, bone cuts at the Le Fort I level were made by a saw above the apices of the maxillary teeth. The pterygoid plates and the nasal septum were separated by osteotome. After .downfracture and mobilization, the maxilla was placed in the final position as planned and fixed by four miniplates. The following data were recorded: 1) exposure, direct tf~uma, or traction of the infraorbital nerve; 2) preservation or division of the greater palatine nerve (GPN); 3) direct damage to the apices of the teeth.
Methods of testing sensation Pulp testing. A monopolar electric pulp tester was used for the electric stimulation of the teeth after isolating them from the saliva with cotton rolls. This pulp tester applied a constant current of up to 150/zA, fulfilling the criteria of MATTHEWS &; SEARL 16. The response was recorded as either positive or negative. Fine touch. Fine touch was recorded with von Frey hair fibres. These are a set of six nylon threads of different thickness and length. When the tip of the hair is applied gently to the skin or mucosa, each hair bends at a particular force representing pressures of 15-25 g/m2. Each area was tested 10 times and perception of touch eight or more times was taken as a positive result. The lightest yon Frey hair to be perceived during the test was recorded as the light-touch threshold. If, in the postoperative period, a different hair was required to stimulate a response, this was recorded as a change in light touch sensation. Pin prick. Sensitivity of the palatal and buecal mucosa and the skin of the face was assessed with a spring algesimeter. Pressure on the needle point compresses a spring and the force applied to the needle point is graduated from 2 to 10 g. The patient was asked to indicate when the sensation became sharp rather than dull. Each area was tested 10 times, and the values from the algesimeter were recorded along with their mean and range. Where the postoperative mean and the range fell outside
the preoperative measurements, this was recorded as a change in pin-prick sensation. Cold sensation. Only skin was tested for cold sensitivity because the size of the apparatus precluded its use in the mouth. Cold sensation was measured with a microcomputercontrolled thermode system by which test stimuli take the form of discrete ramps of temperature change 6. As the rate of temperature change at the thermode is constant (I~ s), the magnitude of each stimulus is determined by the time for which power is applied. This time was determined by the computer. The shortest time which produced a positive response was recorded. After each area had been tested 10 times, the presence of eight or more responses was recorded as a positive result. If the time altered postoperatively, this was recorded as a change in sensation.
Protocols for testing Teeth. The central incisors, the first premolars, and the first molars were examined with an electric pulp tester. Where a tooth was missing, bore a crown, was root-filled, or did not respond to the electric pulp tester preoperatively, an adjacent tooth supplied by the same nerve branch was examined instead. Patients were examined preoperatively and postoperatively at 2 days, 6 weeks, 3 months, and 6 months. Palatal mucosa. Mucosa was tested for fine touch and pin-prick sensation. Two sites were tested on each side of the palate; adjacent to the first molars and behind the central incisors. If either area had abnormal postoperative sensation, this side was recorded as an abnormal "hemipalate". Patients were examined preoperatively and at 2 days, 6 weeks, 3 months, and 6 months postoperatively. Recording sensation on the palate at 2 days and 6 weeks was not always possible because of the presence of intermaxillary fixation.
Buccal mucosa. Two sites were tested for fine touch and pin-prick sensation on each side, in the premolar region, and above the incisors. If any of these four sites differed from the preoperative level, it was recorded as an abnormal level of buccal sensation. Patients were examined preoperatively and at 2 days, 6 weeks, 3 months, and 6 months postoperatively. Skin. The skin was tested for fine touch, pinprick, and cold sensation in three areas on each side; two lateral to the ala of the nose and one area over the upper lip. If any of the areas differed from preoperative measurements, this was recorded. Patients were examined preoperatively and at 2 days, 6 weeks, 3 months, and 6 months postoperatively.
Results Teeth A total o f 119 teeth were examined: 39 incisors, 40 premolars, a n d 40 molars. N o n e were subjected to a n y direct t r a u m a d u r i n g the operation. N o n e developed c o l o u r changes or periapical lesion postoperatively. After 2 days, n o teeth r e s p o n d e d to the electric p u l p tester. A t 6 weeks, eight (7%) teeth; at 3 m o n t h s , 33 (28%) teeth; a n d at 6 m o n t h s , 93 (78%) teeth responded.
Palate: Intact greater palatine bundles In five patients, the greater p a l a t i n e bundles were sectioned; three bilaterally a n d two unilaterally. These eight " h e m i palates" with recorded division o f the greater p a l a t i n e nerve ( G P N ) were analysed a p a r t f r o m the 32 " h e m i p a l a t e s " where the nerve was grossly intact. I n
Table 1. Palatal sensation where greater palatine nerve was grossly intact after Le Fort I osteotomy
Time postoperatively
2 days
6 weeks
3 months
6 months
No. of hemipalates examined Fine touch sensation present Fine touch sensation at preoperative level Pin-prick sensation present Pin-prick sensation at preoperative level
4 4 (100%) 3 (75%) 3 (75%) 2 (50%)
18 16 (89%) 15 (83%) 16 (89%) 15 (83%)
32 30 (94%) 26 (81%) 32 (100%0) 25 (78%)
32 28 32 31
32 (100%) (88%) (100%) (97%)
Table 2. Palatal sensation where greater palatine nerve was divided during Le Fort I osteotomy
Time postoperatively
2 days
6 weeks
3 months
6 months
No. of hemipalates examined Fine touch sensation present Fine touch sensation at preoperative level Pin-prick sensation present Pin-prick sensation at preoperative level
6 2 (33%) 0 (0%) 1 (17%) 0 (0%)
8 3 (38%) 0 (0%) 1 (13%) 0 (0%)
8 4 (50%) 0 (0%) 3 (38%) 2 (25%)
8 8 (100%) 1 (13%) 8 (100%) 5 (63%)
Sensory disturbance after osteotomy all cases, the nasopalatine nerve was divided. The results for the sensation in "hemipalates" where the G P N was grossly intact after Le Fort I osteotomy are summarized in Table 1, and those where the G P N was divided in Table 2.
Fine touch. At 2 days, only four "hemipalates" could be examined. In all of these, sensation was present; in three, the sensation was at preoperative levels. Six weeks postoperatively, 18 sides were examined; of these, sensation was present in 16 (89%) and at the preoperative level in 15 (83%). At 3 months, 32 sides were examined; of these, 30 (94%) had sensation, 26 (81%) at the preoperative level. At 6 months, all "hemipalates" had sensation and 28 (88%) were at the preoperative level. Pin prick. Of the four "hemipalates" examined at 2 days, three had pin-prick sensation and in two the sensation was at the preoperative level. At 6 weeks, of 18 sides examined, 16 (89%) had sensation and in 15 (83%) this was at the preoperative level. At 3 months postoperatively, of 32 sides examined, all had some sensation, and 25 (78%) had normal sensation. At 6 months, 31 (97%) of the 32 "hemipalates" where the greater palatine nerve was grossly intact after osteotomy had full return of preoperative pin-prick sensation. Palate: divided greater palatine nerve
Fine touch. At day 2, six "hemipalates" were examined; of these, two had sensation but none had sensation at the preoperative level. After 6 weeks, eight "hemipalates" were examined; of these three (38%) had sensation, but, again, none of these were at the preoperative level. At 3 months, of the eight "hemipalates", four (50%) had sensation and still none had full return of sensation. After 6 months, all "hemipalates" responded to fine touch, and in one (13%) this was at the preoperative level. Pin prick. After 2 days, six "hemipalates" were examined; of these, one had sensation (17%), but it was not at the preoperative level. At 6 weeks, eight were tested and one had sensation (13%), again at less than the preoperative level. After 3 months, three "hemipalates" (38%) had sensation; in two cases (25%), this was at the preoperative level. At the 6-month review, some sensation had returned in all cases; in five
(63%), this was at the preoperative level. It is interesting to note that the "hemipalates" which recovered sensation most quickly were the two where the contralateral greater palatine nerve was intact. Buccal glngivae
Table 3 summarizes the sensation present in the buccal mucosa, below the incision line, after Le Fort I osteotomy.
Fine touch. N o patients recovered fine touch sensation in their buccal mucosa to the preoperative level. At day 2, seven (35%) patients had some response to fine touch. At 6 weeks, eight patients (40%) had some response to fine touch; at 3 months, 15 (75%) and at 6 months, 19 (95%) responded to fine touch. Pin prick. At 2 days, 6 weeks, and 3 months, no patient had recovered normal pin-prick sensation. After 6 months, 15 (75%) had regained normal sensationl As for partial recovery of pin-prick sensation, at 2 days two patients (10%) had regained some response to pin prick, and at six weeks three (15%), at 3 months 10 (50%), and at 6 months 17 (85%) had demonstrated response to pin-prick stimuli. Skin of face
Table 4 summarizes facial sensation after Le Fort I osteotomy.
Fine touch. At 2 days, 16 (80%) patients responded to fine touch; in 11 patients (55%), sensation was at the preoperative
15
level. At 6 weeks, 3 months, and 6 months, all patients responded to fine touch at the preoperative level.
Pin prick. A t 2 days, 17 (85%) patients responded to pin prick, 13 (65%) at the preoperative level. After 6 weeks, all patients responded to pin prick, 19 (95%) responding at the preoperative level. At 3 months and 6 months, all patients responded at their preoperative level. CoM sensation. At 2 days, 15 (75%) patients responded to thermode stimulation, and 14 (70%) responded at the preoperative level. After 6 weeks, all patients responded to cold with 18 (90%) at the preoperative level. At 3 months and 6 months, all patients responded at the preoperative level. Sensation modalitles across anatomic areas
Pin-prick sensation. The recovery of pin-prick sensation to preoperative levels for each area is shown in Fig. 1. When we examined the return of normal pin-prick sensation across the anatomic areas, we found that it recovered most quickly and most completely on the face. Where the G P N was intact, palatal sensation returned to normal in all but one "hemipalate". When we compared two areas where nerves were divided, that is, the buccal mucosa and palatal mucosa, with a divided GPN, we found that pin-prick sensation took longer to begin recovery in the buccal mucosa, but more patients had fully recovered at 6 months compared to the palate.
Table 3. Sensation in buccal mucosa, below incision line, after Le Fort I osteotomy Time postoperatively 2 days 6 weeks 3 months 6 months No. of patients Buccal fine touch sensation present Buccal fine touch sensation at preoperative levels Buccal pin-prick sensation present Buccal pin-prick sensation at preoperative levels
20 7 (35%) 0 (90%) 2 (10%) 0 (0%)
Table 4. Facial sensation after Le Fort I osteotomy 2 days
Time postoperatively
No. of patients examined Fine touch sensation present Fine touch sensation at preoperative level Pin-prick sensation present Pin-prick sensation at preoperative level Cold sensation present Cold sensation at preoperative level
20 16 (80%) 11 (55%) 17 (85%) 13 (65%) 15 (75%) 14 (70%)
20 8 (40%) 0 (0%) 3 (15%) 0 (0%)
20 20 15 (75%) 19 (95%) 0 (0%) 0 (0%) 10 (50%) 17 (85%) 0 (0%) 15 (75%)
6 weeks
3 months
6 months
20 20 (100%) 20 (100%) 20 (100%) 19 (95%) 20 (100%) 18 (90%)
20 20 (100%) 20 (100%) 20 (100%) 20 (100%) 20 (lOO%) 20 (100%)
20 20 (100%) 20 (100%) 20 (100%) 20 (100%) 20 (lOO%) 20 (100~
16
Al-Din et al. o
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Fig. 1. Return o f pin-prick sensation to preoperative level after Le Fort I osteotomy.
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Fig. 2. Return o f pin-prick sensation at any level after Le Fort I osteotomy.
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In comparison to the return of preoperative levels of sensation, the return of any level of pin-prick sensation in the four areas tested was more complete. On the face and on the palate where the GPN was intact, all patients had some pin-prick sensation at 3 months. The return of pin-prick sensation is shown in Fig. 2. At 6 months, palates with divided and intact GPN had some pinprick sensation, but three patients did not have any pin-prick sensation in their buccal sulcus. When the differences between "hemipalates" with intact and divided G P N were compared with the chi-square test, the differences in the return to preoperative levels of pin-prick sensation (P=0.03) were significant. The difference in the return of any pin-prick sensation between these two groups did not reach significance.
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sensation is illustrated in Fig. 3. It returned to preoperative levels less quickly and less completely than pinprick sensation. The skin of the face was the only area which recovered completely. Palatal mucosa where the G P N was intact recovered slightly less over the 6 months studied, palatal mucosa with a divided GPN recovered markedly less, and buccal mucosa did not recover normal levels of fine touch in any case. When simply the presence of any level of fine touch sensation was examined, it was found to follow a pattern similar to the return of any level of pinprick sensation. This is illustrated in Fig. 4. On the face, in the palate with grossly intact GPN, and in the palate with a divided GPN, all patients regained some fine touch sensation. In the buccal mucosa, all but one patient regained some fine touch sensation. The difference in the return of preoperative fine touch sensation between "hemipalates" with intact and divided greater palatine nerve was significant when assessed by the chi-square test (P=0.0001). The differences between the return of any level of fine touch did not achieve significance.
20%
Discussion
10%
When we reviewed the literature on sensory morbidity after orthognathic surgery, we found t h a t mandibular osteotomies have been more widely investigated 1'2'17'22 than those in the max-
0%' t0
15
20
25
Weeks post-op
Fig. 3. Return o f fine t o u c h sensation at preoperative level after Le Fort I osteotomy.
Sensory disturbance after osteotomy 100%- ~
90%-
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"~" ~
9
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20% -
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I 5
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151
10
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Weeks post-op
Fig. 4. Return of fine touch sensation at any level after Le Fort I osteotomy.
ilia. Most previous studies of sensory nerve supply in the maxilla after osteotomy relate to segmental procedures 8,9,12,13,18, and these studies have focused on the vitality of the teeth. Few researchers have studied sensation in soft tissues3,1~ ' Furthermore, in these last studies, pin-prick sensation was either recorded imprecisely, with a dental probe rather than an algesimeter 3'1~ or not recorded at all 11,19. This study used reliable objective means of testing for sensory modalities, the preoperative measures being used as a control. The follow-up period was 6 months, and relevant surgical details were recorded prospectively in all cases. Teeth
Animal studies have been carried out on the effects of segmental surgery on the nerve supply of the teeth. POSWmLO2~ carried out an experimental study on two monkeys (Macaca irus) with open bite treated by maxillary segmental surgery. At 2, 3, 4, and 6 months postoperatively, a tooth was removed from the repositioned segment by sectional excision of an enclosing block of alveolus and examined microscopically. The early microscopic examination of the teeth in the repositioned segment showed fibrosis of the pulp and loss of nerves and the odontoblast layer. At 6 months, the teeth had viable pulps without sensory nerves. In contrast, ROBINSON21 demonstrated that mandibular canines are reinnervated by regenerating inferior alveolar nerve fibres despite repositioning of the segments and insertion of a bone
graft at the osteotomy site. The regenerating fibres were capable of crossing a gap between the bone ends containing an organizing haematoma and passing through, or around, bone graft. However, electromicroscopic examination of the apices of the teeth showed reduction in the number of axons, and the myelinated axons were smaller and had thinner myelin sheaths. HOLLAND & ROBINSON7, again using cats as a model, confirmed that reinnervation of the teeth occurred, but the reinnervated myelinated axons were fewer in number, smaller in size, and had thinner myelin sheaths. The nonmyelinated fibres had fewer axons per fibre. Turning to studies on human subjects, many authors 8,9,12A3A8 have published papers on the sensory response of teeth after maxillary segmental osteotomies and a smaller number3,1~ after Le Fort I osteotomy. All reported varying degrees of sensory loss in teeth which recovered with time. L~mOLD et al) 2 found the maxillary canines to be more frequently nonresponsive after segmental osteotomy, attributing this to the high position of the apices which made them more vulnerable to periapical surgical trauma. DE JONGH et al. 3 compared electric and thermal pulp testing of 10 patients after Le Fort I osteotomy with 10 matched controls who had not undergone osteotomy. The mean time after surgery was 14 months, and at this time 71% of the 128 teeth were responsive to thermal and electric pulp stimulation, as opposed to 93% of 136 teeth in the controls. However, it is difficult to draw
17
any conclusions, as differences between the two small groups may be due to sampling error. KAHNBERG (~ ENGSTR6M10 followed up 30 patients who had Le Fort I osteotomies for 18 months, and their results are consistent with the present study. Tooth response was lost immediately postoperatively in almost all of the patients; at 2 months, 9.7% of the teeth were responsive to electric pulp stimulation; at 6 months, 78.7%; and at 18 months over 90%. TAJIMA23 studied response to electric pulp testing in 27 cases of Le Fort osteotomy and Le Fort fracture. In this series, 23% of teeth were responsive at 6 months and 71% at 14 months, the canines recovering sensation quicker and more completely than molars, premolars, and incisors. In contrast to LEIBOLD et al. 1 2 , K A H N B E R G r163 E N G S T R O M 10 found canines slower to recover. D I e t al. 5 carried out a histologic examination on 17 maxillary third molars, which were extracted from 10 patients who had Le Fort I osteotomies. The mean follow-up was 40 months. They found that 60% of the completely developed teeth had normal pulpal architecture with an intact odontoblastic layer. There was no evidence of pulpal necrosis, and the peripheral plexus of nerve bundles was seen clearly in most of the sections. None of the teeth in this study were subjected to direct trauma during surgery, as the bone cuts were located at a minimum of 5 mm above the apices. The amount of bone covering the apices was therefore sufficient to allow re-establishment of both the vascular and nerve supply ~8. JOHNSON(~ HINDS9 pointed out that an adequate blood supply is essential for vitality. It has been proposed that cut nerves regenerate in an area where the blood supply has been preserved 13. There is no single vessel essential in maintaining the circulation in the Le Fort I osteotomy because of the abundant anastomoses provided by the maxillary artery 5. The percentage of teeth regaining sensitivity to the electric pulp tester and the rate of return in this study are consistent with these previous studies. Buccal m u c o s a
In the current paper, sensation was tested on the buccal mucosa just above the attached gingiva and below the line of the incision. One previous study 3
18
AI-D& et al.
tried to assess fine touch inside the mouth but abandoned this part of the study as cotton wool proved to be "too unreliable". We found that none of the patients had regained preoperative levels of fine touch sensation in the buccal gingivae at 6 months. After 6 months, one patient had no perception of fine touch at all, the remaining 19 having some sensation but at a reduced level. POSN]CK et al. 19 tested upper lip mucosa 1 year after Le Fort I osteotomy. Fine touch sensation was assessed with Semmes-Weinstein monofilaments, twopoint discrimination with the MacKinnon-Dellon Disk Criminator, and vibration sense with the Biothesiometer. This study found decreased levels of sensation in all modalities compared to preoperative levels. Although there was an objective reduction in sensation, the patients were unaware of any alteration of sensory function. Turning to pin-prick sensation in the buccal mucosa, two other studies have examined this with a dental probe rather than an algesimeter. KAHNBERG & ENGSTR6M1~ noted that in the labiobuccal mucosa, pin-prick sensation was markedly diminished after the vestibular incision during the first 2 months, but was re-established by 6 months. In a survey of 10 patients who underwent maxillary osteotomy a mean of 1 year prior to examination, DE JONGH et al. 3 found that the buccal tissues were less responsive than a control group who had not had surgery. This difference was more marked posteriorly than in anterior sites. In the present study, 17 patients regained some pin-prick sensation at 6 months, and in most of these (15) it was at the same level as preoperatively. Palatal mucosa
In the present study, pin-prick sensation in the palate returned in all cases, in spite of the division of the nasopalatine nerve, provided the greater palatine nerves remained grossly intact at operation. Of the 32 "hemipalates" with an intact GPN, 31 recovered pin-prick sensation to the preoperative level. Other series examined pin prick with a dental probe rather than an algesimeter3,1~ MAGENNIS TM found that palatal sensation, including pin-prick, was not affected by division of the nasopalatine nerve during removal or exposure of maxillary canines. KArrNaERG & ENG-
STROM10 did not detect any reduction in
sensation except in a few patients with previous cleft palate surgery. In contrast, DE JONGH et at. 3 found that pinprick sensation was reduced compared to a control group 14 months postoperatively even though the greater palatine nerves had not been divided. No previous study has examined fine touch on the palate. The current study found fine touch sensation returned in all patients where the GPN was grossly intact, and in 88% sensation had returned to the preoperative level. No previous study has examined patients in whom the greater palatine nerve was divided during surgery. The number of patients with sectioned GPN in this study was small, three patients having the GPN divided bilaterally and two unilaterally, yielding eight "hemipalates" whose nerve was sectioned. All eight "hemipalates" regained some level of pin-prick and fine touch sensation at 6 months. In only one of these "hemipalates" did fine touch sensation return to the preoperative levels, and in this case the contralateral GPN was intact. Five "hemipalates" returned to a preoperative level of pin-prick sensation, and the two cases with an intact contralateral GPN were in this group. Where only unilateral GPN division occurred, sensation seemed to return more quickly on the ipsilateral side than in cases where both GPNs were divided. This suggests some crossover sensation from the intact contralateral nerve, but the numbers are too small for firm conclusions to be drawn. Face
Sensation in the face is rarely affected for any length of time after Le Fort I osteotomy. KAHNBERG • ENGSTR()M10 recorded that infraorbital pin-prick sensation was reduced in all patients where suspension wires had been attached to the infraorbital rims, but noted a return sensation at 2-6 months postoperatively. KARAS et al. 11 examined sensation before and after surgery in 13 patients having Le Fort I osteotomy and 20 patients having mandibular osteotomies. They assessed static light touch with von Frey hairs, moving touch with a no. 2 sable-hair brush, and two-point discrimination with the Boley gauge. In those having maxillary surgery, sensory deficits were detected immediately postoperatively in 49%. After 3 months, all
patients achieved a full return to preoperative levels of fine touch. Moving touch also showed a similar pattern and two-point discrimination improved postoperatively. POSNICK et al. 19 assessed fine touch, two-point discrimination, and vibration sense on the face and lip after Le Fort I osteotomy, but they did not examine the palate. No significant differences could be found in fine touch and vibration sense 12 months postoperatively. In contrast to the findings of KARAS et al. 11, there was an increase in mean postoperative two-point discrimination values in all areas and in all patient groups, but this approached significance only in anterior cheek skin in the patients with unilateral cleft lip. The patients did not complain of any subjective loss of sensation in spite of the increased two-point discrimination distance. All patients in the current study showed a return to normal sensation in all modalities examined within the period of follow-up. This was expected as injury to the infraorbital nerve was due to traction only.
Conclusion
The Le Fort I osteotomy caused alteration of sensation in the maxillary teeth, buccal and palatal mucosa, and the skin of the face. Some of this sensory loss was subtle and may represent an objective alteration in the threshold of sensation rather than subjective numbness or paraesthesia. Sensation, in terms of cold sensation, pin-prick, fine touch, and pulp sensitivity returns to all tissues in spite of division or damage of many nerves serving the area. However, this return of sensation does not always reach preoperative levels. Patients undergoing Le Fort I osteotomy should be warned of the potential for sensory morbidity, particularly if the movement planned suggests that division of the greater palatine nerve may be necessary.
References
1. BRUSATIR, FIAMMINGHIL, SESENNAE, GAZZOTTIA. Functional disturbance of the inferior alveolar nerve after sagittal osteotomy of the mandibular ramus: operating technique for prevention. J MaxFac Surg 1981: 9: 123-5. 2. COGLANKM, IRVINEGH. Neurological
Sensory disturbance after osteotomy damage after sagittal split osteotomy. Int J Oral Maxillofac Surg 1986: 15: 369-71. 3. DE JONGH M, BARNARDD, BIRNIE D. Sensory nerve morbidity following Le Fort I osteotomy. J Max-Fac Surg 1986: 14: 1013. 4. DENNY-BROWN D, YANAGISAWAN. The descending trigeminal tract as a mechanism for inter-segmental sensory facilitation. Trans Am Neurol Assoc 1970: 95: 129-31. 5. DI S, BELL WO, MANNAI C, et al. Long term evaluation of human teeth after Le Fort I osteotomy: a histologic and developmental study. Oral Surg 1988: 65: 37986. 6. FOWLER C J, CARROLL MB, BURNS D, HOWE N, ROBINSON K. A portable system for measuring cutaneous thresholds for warming and cooling. J Neurol Neurosurg Psychiatry 1987: 50: 1211-15. 7. HOLLAND GR, ROBINSON PP. Reinnervation of teeth after segmental osteotomy. Int J Oral Maxillofac Surg 1986: 15: 437-43. 8. HUTCHINSON ND, MACGREGOR AJ. Tooth survival following various methods of sub-apical osteotomy. Int J Oral Surg 1972: 1:81 6. 9. JOHNSON JV, HINDS EG. Evaluation of teeth vitality after subapical osteotomy. J Oral Surg 1969: 27: 256.
10. KAHNBERG KE, ENGSTROM H. Recovery of maxillary sinus and tooth sensibility after Le Fort I osteotomy. Br J Oral Maxillofac Surg 1987: 25: 68-73. 11. KARASND, BOYD SB, SINN DE Recovery of neurosensory function following orthognathic surgery. J Oral Maxillofac Surg 1990: 48: 124-34. 12. LEIBOLD DG, TILSON HB, RASK KR. A subjective evaluation of the re-establishment of the neurovascular supply of teeth involved in anterior maxillary osteotomy procedure. Oral Surg 1971: 32: 531-43. 13. MACGREGORA. Histology of a pulp following segmental alveolotomy. Br J Oral Surg 1970-1: 8: 292. 14. MAGENNISE Sensory loss associated with palatal flaps fact or fiction? J Irish Dent Assoc 1990: 36: 60-1. 15. MALONEYF, WORTHINGTONP. The origin of the Le Fort I maxillary osteotomy: Cheever's operation. J Oral Surg 1981: 39: 731-4. 16. MATTHEWS B, SEARLE BN. Electrical stimulation of teeth. Pain 1976: 2: 245. 17. PEPERSACKWJ, CHAUSSEJM. Long term follow-up of the sagittal split technique for correction of mandibular prognathism. J Max-Fac Surg 1978: 6: 136-9. 18. PEPERSACK WJ. Tooth vitality after alveolar segmental osteotomy. J Max-Fac Surg 1973: 1: 85-91.
19
19. POSNICKJC, AL-QUATTANMM, PITONG. Facial sensibility in adolescents with and without clefts 1 year after undergoing Le Fort I osteotomy. Plast Reconstr Surg 1994: 94: 431-5. 20. POSWILLO DE. Early pulp changes following reduction of open bite by segmental surgery. Int J Oral Surg 1972: 1: 87-97. 21. ROBINSON PE Reinnervation of teeth after segmental osteotomy in the cat. Int J Oral Maxillofac Surg 1986: 15: 152-9. 22. SVARTXZK, ArlLBOR~ G, FINI,m K, NETHANDERG. Nerve disturbance after sagittal split osteotomy. Int J Oral Surg 1983: 12: 279-80. 23. TAJIMAS. k longitudinal study on electrical pulp testing following Le Fort I and Le Fort type fracture. J Max-Fac Surg 1975: 3: 74-80.
Address:
K. M. Coghlan Department of Oral and Maxillofacial Surgery Royal London Hospital Whitechapel, London E1 1BB UK
Int..L Oral Maxillofac. Surg. 1996; 25:13-19 Printed in Denmark. All rights reserved
InternationalJournalof
Ord &
MaxillofacialSurgery ISSN 0901-5027
Aestheticand reconstructivesurgery
Sensory nerve disturbance following Le Fort I osteotomy
O. E Shehab AI-Din 1, K.M. Coghlan 2, P. Magennis s 1joint Department of Oral and Maxillofacial Surgery, Eastman Dental and University College Hospitals, London; 2Department of Oral and Maxillofacial Surgery, Royal Hospitals Trust, London; aDepartment of Oral and Maxillofacial Surgery, London Hospital Medical College Dental Institute, London, UK
O. F. Shehab Al-Din, K. M. Coghlan, P. Magennis: Sensory nerve disturbance following Le Fort I osteotomy. Int. J. Oral Maxillofac. Surg. 1996; 25: 13-19. 9 Munksgaard, 1996 Abstract. This study assessed sensory nerve disturbance after Le Fort I osteotomy using the electric pulp test, pin-prick sensation, fine touch, and cold sensation. After 6 months, 78% of teeth positive preoperatively to an electric pulp tester regained sensitivity. Return of palatal sensation was affected by whether or not the greater palatine nerve (GPN) was divided during surgery. After 6 months, where the G P N was intact, all patients had fine touch sensation (88% at the preoperative level), and all had pin-prick sensation (97% at preoperative level). When the G P N was divided, all patients had fine touch sensation (13% at preoperative level), and all had pin-prick sensation (63% at preoperative level). The differences in the return to preoperative sensation were significant for fine touch (P=0.0001) and for pin-prick (P=0.03) by chi-square analysis. Sensation returned more quickly and more completely in the two cases where the contralateral G P N was intact. In the buccal mucosa, 95% of patients regained some fine touch sensation after 6 months, but none returned to the preoperative level. Similarly, 85% regained some pin-prick sensation, but none achieved preoperative levels. Cold sensation, pin-prick sensation, and fine touch on the face returned to the preoperative level in all patients by 6 weeks postoperatively.
The Le Fort I maxillary osteotomy was first performed by CHEEVER in 1867 to provide surgical access to a nasopharyngeal tumour 15. The main role of the Le Fort I osteotomy today is in the management of dentofacial deformity. The downfracture technique has gained wide acceptance, and it is now the most frequently performed midface osteotomy. During Le Fort I osteotomy, the nasopalatine nerve; the anterior, middle, and posterior superior alveolar nerves; and the small terminal nerves in the buccal mucosa along the incision line between the upper first molars are always divided. This loss of continuity is further increased by moving the fragment in horizontal and vertical planes.
Movement may also stretch or divide the greater palatine nerves, or they may be electively sectioned to facilitate larger movements. The infraorbital nerve may be injured indirectly by pressure, retraction, or fixation with plates or screws. The sensory nerve supply of the maxilla and face is provided solely by the maxillary division of the trigeminal nerve (except the anterior part of the nasal septum and the lateral nasal wall supplied by the first division). It is surprising that patients do not more frequently complain of numbness after surgery which divides so many branches of the maxillary division. Animal studies 4 have shown that the trigeminal nerve is not the only source of sensation
Key words: osteotomy; Le Fort I; sensory deficit. Accepted for publication21 June 1995
in these areas. DENNY-BRoWN & YANAhave demonstrated the importance of the descending trigeminal tract in modifying the intensity of sensation in any one part of the trigeminal or cervical segments. The purpose of this study was to assess prospectively the sensory morbidity associated with the Le Fort I osteotomy and record any recovery of sensation over a period of 6 months. GISAWA4
Material and methods
Twenty adults (15 women and five men, average age 25 years (range 18-42 years)) undergoing bimaxillary surgery involving Le Fort I downfracture of the maxilla were entered into the study. They were consecutive cases treated in the unit over 6 months.
14
A l - D i n et al.
Modalities of sensation tested included fine touch, pin-prick, and cold. All sensory testing was carried out by a single operator (O.ES.A.) preoperatively, at 2 days, 6 weeks, 3 months, and 6 months postoperatively. Preoperative testing allowed direct comparison to be made, with patients acting as their own control. In an attempt to avoid bias during the postoperative tests, patients were not asked about any subjective loss of sensation; they were asked only to cooperate with the examination.
Surgical procedure Surgery was performed by two consultant surgeons. With a standard upper buccal sulcus incision from the maxillary left first molar to the maxillary right first molar, bone cuts at the Le Fort I level were made by a saw above the apices of the maxillary teeth. The pterygoid plates and the nasal septum were separated by osteotome. After .downfracture and mobilization, the maxilla was placed in the final position as planned and fixed by four miniplates. The following data were recorded: 1) exposure, direct tf~uma, or traction of the infraorbital nerve; 2) preservation or division of the greater palatine nerve (GPN); 3) direct damage to the apices of the teeth.
Methods of testing sensation Pulp testing. A monopolar electric pulp tester was used for the electric stimulation of the teeth after isolating them from the saliva with cotton rolls. This pulp tester applied a constant current of up to 150/zA, fulfilling the criteria of MATTHEWS &; SEARL 16. The response was recorded as either positive or negative. Fine touch. Fine touch was recorded with von Frey hair fibres. These are a set of six nylon threads of different thickness and length. When the tip of the hair is applied gently to the skin or mucosa, each hair bends at a particular force representing pressures of 15-25 g/m2. Each area was tested 10 times and perception of touch eight or more times was taken as a positive result. The lightest yon Frey hair to be perceived during the test was recorded as the light-touch threshold. If, in the postoperative period, a different hair was required to stimulate a response, this was recorded as a change in light touch sensation. Pin prick. Sensitivity of the palatal and buecal mucosa and the skin of the face was assessed with a spring algesimeter. Pressure on the needle point compresses a spring and the force applied to the needle point is graduated from 2 to 10 g. The patient was asked to indicate when the sensation became sharp rather than dull. Each area was tested 10 times, and the values from the algesimeter were recorded along with their mean and range. Where the postoperative mean and the range fell outside
the preoperative measurements, this was recorded as a change in pin-prick sensation. Cold sensation. Only skin was tested for cold sensitivity because the size of the apparatus precluded its use in the mouth. Cold sensation was measured with a microcomputercontrolled thermode system by which test stimuli take the form of discrete ramps of temperature change 6. As the rate of temperature change at the thermode is constant (I~ s), the magnitude of each stimulus is determined by the time for which power is applied. This time was determined by the computer. The shortest time which produced a positive response was recorded. After each area had been tested 10 times, the presence of eight or more responses was recorded as a positive result. If the time altered postoperatively, this was recorded as a change in sensation.
Protocols for testing Teeth. The central incisors, the first premolars, and the first molars were examined with an electric pulp tester. Where a tooth was missing, bore a crown, was root-filled, or did not respond to the electric pulp tester preoperatively, an adjacent tooth supplied by the same nerve branch was examined instead. Patients were examined preoperatively and postoperatively at 2 days, 6 weeks, 3 months, and 6 months. Palatal mucosa. Mucosa was tested for fine touch and pin-prick sensation. Two sites were tested on each side of the palate; adjacent to the first molars and behind the central incisors. If either area had abnormal postoperative sensation, this side was recorded as an abnormal "hemipalate". Patients were examined preoperatively and at 2 days, 6 weeks, 3 months, and 6 months postoperatively. Recording sensation on the palate at 2 days and 6 weeks was not always possible because of the presence of intermaxillary fixation.
Buccal mucosa. Two sites were tested for fine touch and pin-prick sensation on each side, in the premolar region, and above the incisors. If any of these four sites differed from the preoperative level, it was recorded as an abnormal level of buccal sensation. Patients were examined preoperatively and at 2 days, 6 weeks, 3 months, and 6 months postoperatively. Skin. The skin was tested for fine touch, pinprick, and cold sensation in three areas on each side; two lateral to the ala of the nose and one area over the upper lip. If any of the areas differed from preoperative measurements, this was recorded. Patients were examined preoperatively and at 2 days, 6 weeks, 3 months, and 6 months postoperatively.
Results Teeth A total o f 119 teeth were examined: 39 incisors, 40 premolars, a n d 40 molars. N o n e were subjected to a n y direct t r a u m a d u r i n g the operation. N o n e developed c o l o u r changes or periapical lesion postoperatively. After 2 days, n o teeth r e s p o n d e d to the electric p u l p tester. A t 6 weeks, eight (7%) teeth; at 3 m o n t h s , 33 (28%) teeth; a n d at 6 m o n t h s , 93 (78%) teeth responded.
Palate: Intact greater palatine bundles In five patients, the greater p a l a t i n e bundles were sectioned; three bilaterally a n d two unilaterally. These eight " h e m i palates" with recorded division o f the greater p a l a t i n e nerve ( G P N ) were analysed a p a r t f r o m the 32 " h e m i p a l a t e s " where the nerve was grossly intact. I n
Table 1. Palatal sensation where greater palatine nerve was grossly intact after Le Fort I osteotomy
Time postoperatively
2 days
6 weeks
3 months
6 months
No. of hemipalates examined Fine touch sensation present Fine touch sensation at preoperative level Pin-prick sensation present Pin-prick sensation at preoperative level
4 4 (100%) 3 (75%) 3 (75%) 2 (50%)
18 16 (89%) 15 (83%) 16 (89%) 15 (83%)
32 30 (94%) 26 (81%) 32 (100%0) 25 (78%)
32 28 32 31
32 (100%) (88%) (100%) (97%)
Table 2. Palatal sensation where greater palatine nerve was divided during Le Fort I osteotomy
Time postoperatively
2 days
6 weeks
3 months
6 months
No. of hemipalates examined Fine touch sensation present Fine touch sensation at preoperative level Pin-prick sensation present Pin-prick sensation at preoperative level
6 2 (33%) 0 (0%) 1 (17%) 0 (0%)
8 3 (38%) 0 (0%) 1 (13%) 0 (0%)
8 4 (50%) 0 (0%) 3 (38%) 2 (25%)
8 8 (100%) 1 (13%) 8 (100%) 5 (63%)
Sensory disturbance after osteotomy all cases, the nasopalatine nerve was divided. The results for the sensation in "hemipalates" where the G P N was grossly intact after Le Fort I osteotomy are summarized in Table 1, and those where the G P N was divided in Table 2.
Fine touch. At 2 days, only four "hemipalates" could be examined. In all of these, sensation was present; in three, the sensation was at preoperative levels. Six weeks postoperatively, 18 sides were examined; of these, sensation was present in 16 (89%) and at the preoperative level in 15 (83%). At 3 months, 32 sides were examined; of these, 30 (94%) had sensation, 26 (81%) at the preoperative level. At 6 months, all "hemipalates" had sensation and 28 (88%) were at the preoperative level. Pin prick. Of the four "hemipalates" examined at 2 days, three had pin-prick sensation and in two the sensation was at the preoperative level. At 6 weeks, of 18 sides examined, 16 (89%) had sensation and in 15 (83%) this was at the preoperative level. At 3 months postoperatively, of 32 sides examined, all had some sensation, and 25 (78%) had normal sensation. At 6 months, 31 (97%) of the 32 "hemipalates" where the greater palatine nerve was grossly intact after osteotomy had full return of preoperative pin-prick sensation. Palate: divided greater palatine nerve
Fine touch. At day 2, six "hemipalates" were examined; of these, two had sensation but none had sensation at the preoperative level. After 6 weeks, eight "hemipalates" were examined; of these three (38%) had sensation, but, again, none of these were at the preoperative level. At 3 months, of the eight "hemipalates", four (50%) had sensation and still none had full return of sensation. After 6 months, all "hemipalates" responded to fine touch, and in one (13%) this was at the preoperative level. Pin prick. After 2 days, six "hemipalates" were examined; of these, one had sensation (17%), but it was not at the preoperative level. At 6 weeks, eight were tested and one had sensation (13%), again at less than the preoperative level. After 3 months, three "hemipalates" (38%) had sensation; in two cases (25%), this was at the preoperative level. At the 6-month review, some sensation had returned in all cases; in five
(63%), this was at the preoperative level. It is interesting to note that the "hemipalates" which recovered sensation most quickly were the two where the contralateral greater palatine nerve was intact. Buccal glngivae
Table 3 summarizes the sensation present in the buccal mucosa, below the incision line, after Le Fort I osteotomy.
Fine touch. N o patients recovered fine touch sensation in their buccal mucosa to the preoperative level. At day 2, seven (35%) patients had some response to fine touch. At 6 weeks, eight patients (40%) had some response to fine touch; at 3 months, 15 (75%) and at 6 months, 19 (95%) responded to fine touch. Pin prick. At 2 days, 6 weeks, and 3 months, no patient had recovered normal pin-prick sensation. After 6 months, 15 (75%) had regained normal sensationl As for partial recovery of pin-prick sensation, at 2 days two patients (10%) had regained some response to pin prick, and at six weeks three (15%), at 3 months 10 (50%), and at 6 months 17 (85%) had demonstrated response to pin-prick stimuli. Skin of face
Table 4 summarizes facial sensation after Le Fort I osteotomy.
Fine touch. At 2 days, 16 (80%) patients responded to fine touch; in 11 patients (55%), sensation was at the preoperative
15
level. At 6 weeks, 3 months, and 6 months, all patients responded to fine touch at the preoperative level.
Pin prick. A t 2 days, 17 (85%) patients responded to pin prick, 13 (65%) at the preoperative level. After 6 weeks, all patients responded to pin prick, 19 (95%) responding at the preoperative level. At 3 months and 6 months, all patients responded at their preoperative level. CoM sensation. At 2 days, 15 (75%) patients responded to thermode stimulation, and 14 (70%) responded at the preoperative level. After 6 weeks, all patients responded to cold with 18 (90%) at the preoperative level. At 3 months and 6 months, all patients responded at the preoperative level. Sensation modalitles across anatomic areas
Pin-prick sensation. The recovery of pin-prick sensation to preoperative levels for each area is shown in Fig. 1. When we examined the return of normal pin-prick sensation across the anatomic areas, we found that it recovered most quickly and most completely on the face. Where the G P N was intact, palatal sensation returned to normal in all but one "hemipalate". When we compared two areas where nerves were divided, that is, the buccal mucosa and palatal mucosa, with a divided GPN, we found that pin-prick sensation took longer to begin recovery in the buccal mucosa, but more patients had fully recovered at 6 months compared to the palate.
Table 3. Sensation in buccal mucosa, below incision line, after Le Fort I osteotomy Time postoperatively 2 days 6 weeks 3 months 6 months No. of patients Buccal fine touch sensation present Buccal fine touch sensation at preoperative levels Buccal pin-prick sensation present Buccal pin-prick sensation at preoperative levels
20 7 (35%) 0 (90%) 2 (10%) 0 (0%)
Table 4. Facial sensation after Le Fort I osteotomy 2 days
Time postoperatively
No. of patients examined Fine touch sensation present Fine touch sensation at preoperative level Pin-prick sensation present Pin-prick sensation at preoperative level Cold sensation present Cold sensation at preoperative level
20 16 (80%) 11 (55%) 17 (85%) 13 (65%) 15 (75%) 14 (70%)
20 8 (40%) 0 (0%) 3 (15%) 0 (0%)
20 20 15 (75%) 19 (95%) 0 (0%) 0 (0%) 10 (50%) 17 (85%) 0 (0%) 15 (75%)
6 weeks
3 months
6 months
20 20 (100%) 20 (100%) 20 (100%) 19 (95%) 20 (100%) 18 (90%)
20 20 (100%) 20 (100%) 20 (100%) 20 (100%) 20 (lOO%) 20 (100%)
20 20 (100%) 20 (100%) 20 (100%) 20 (100%) 20 (lOO%) 20 (100~
16
Al-Din et al. o
100%,
90%. 80% 9
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',
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Fig. 1. Return o f pin-prick sensation to preoperative level after Le Fort I osteotomy.
100% -
Fine touch. The recovery of fine touch
1 90% 80%-
f
i
9
/ /
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i
,
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Fig. 2. Return o f pin-prick sensation at any level after Le Fort I osteotomy.
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90% 80%
i
70%
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E
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=
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In comparison to the return of preoperative levels of sensation, the return of any level of pin-prick sensation in the four areas tested was more complete. On the face and on the palate where the GPN was intact, all patients had some pin-prick sensation at 3 months. The return of pin-prick sensation is shown in Fig. 2. At 6 months, palates with divided and intact GPN had some pinprick sensation, but three patients did not have any pin-prick sensation in their buccal sulcus. When the differences between "hemipalates" with intact and divided G P N were compared with the chi-square test, the differences in the return to preoperative levels of pin-prick sensation (P=0.03) were significant. The difference in the return of any pin-prick sensation between these two groups did not reach significance.
IP
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sensation is illustrated in Fig. 3. It returned to preoperative levels less quickly and less completely than pinprick sensation. The skin of the face was the only area which recovered completely. Palatal mucosa where the G P N was intact recovered slightly less over the 6 months studied, palatal mucosa with a divided GPN recovered markedly less, and buccal mucosa did not recover normal levels of fine touch in any case. When simply the presence of any level of fine touch sensation was examined, it was found to follow a pattern similar to the return of any level of pinprick sensation. This is illustrated in Fig. 4. On the face, in the palate with grossly intact GPN, and in the palate with a divided GPN, all patients regained some fine touch sensation. In the buccal mucosa, all but one patient regained some fine touch sensation. The difference in the return of preoperative fine touch sensation between "hemipalates" with intact and divided greater palatine nerve was significant when assessed by the chi-square test (P=0.0001). The differences between the return of any level of fine touch did not achieve significance.
20%
Discussion
10%
When we reviewed the literature on sensory morbidity after orthognathic surgery, we found t h a t mandibular osteotomies have been more widely investigated 1'2'17'22 than those in the max-
0%' t0
15
20
25
Weeks post-op
Fig. 3. Return o f fine t o u c h sensation at preoperative level after Le Fort I osteotomy.
Sensory disturbance after osteotomy 100%- ~
90%-
~.
J
~.
~ , ~
"~" ~
9
80% -
9
f
/ /
i
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i
/
i 60% -
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- - Palate - intact GPN
30% -
9~ K = Palate - divided GPN
20% -
10% -
0% 0
I 5
I
151
10
I 20
I 25
Weeks post-op
Fig. 4. Return of fine touch sensation at any level after Le Fort I osteotomy.
ilia. Most previous studies of sensory nerve supply in the maxilla after osteotomy relate to segmental procedures 8,9,12,13,18, and these studies have focused on the vitality of the teeth. Few researchers have studied sensation in soft tissues3,1~ ' Furthermore, in these last studies, pin-prick sensation was either recorded imprecisely, with a dental probe rather than an algesimeter 3'1~ or not recorded at all 11,19. This study used reliable objective means of testing for sensory modalities, the preoperative measures being used as a control. The follow-up period was 6 months, and relevant surgical details were recorded prospectively in all cases. Teeth
Animal studies have been carried out on the effects of segmental surgery on the nerve supply of the teeth. POSWmLO2~ carried out an experimental study on two monkeys (Macaca irus) with open bite treated by maxillary segmental surgery. At 2, 3, 4, and 6 months postoperatively, a tooth was removed from the repositioned segment by sectional excision of an enclosing block of alveolus and examined microscopically. The early microscopic examination of the teeth in the repositioned segment showed fibrosis of the pulp and loss of nerves and the odontoblast layer. At 6 months, the teeth had viable pulps without sensory nerves. In contrast, ROBINSON21 demonstrated that mandibular canines are reinnervated by regenerating inferior alveolar nerve fibres despite repositioning of the segments and insertion of a bone
graft at the osteotomy site. The regenerating fibres were capable of crossing a gap between the bone ends containing an organizing haematoma and passing through, or around, bone graft. However, electromicroscopic examination of the apices of the teeth showed reduction in the number of axons, and the myelinated axons were smaller and had thinner myelin sheaths. HOLLAND & ROBINSON7, again using cats as a model, confirmed that reinnervation of the teeth occurred, but the reinnervated myelinated axons were fewer in number, smaller in size, and had thinner myelin sheaths. The nonmyelinated fibres had fewer axons per fibre. Turning to studies on human subjects, many authors 8,9,12A3A8 have published papers on the sensory response of teeth after maxillary segmental osteotomies and a smaller number3,1~ after Le Fort I osteotomy. All reported varying degrees of sensory loss in teeth which recovered with time. L~mOLD et al) 2 found the maxillary canines to be more frequently nonresponsive after segmental osteotomy, attributing this to the high position of the apices which made them more vulnerable to periapical surgical trauma. DE JONGH et al. 3 compared electric and thermal pulp testing of 10 patients after Le Fort I osteotomy with 10 matched controls who had not undergone osteotomy. The mean time after surgery was 14 months, and at this time 71% of the 128 teeth were responsive to thermal and electric pulp stimulation, as opposed to 93% of 136 teeth in the controls. However, it is difficult to draw
17
any conclusions, as differences between the two small groups may be due to sampling error. KAHNBERG (~ ENGSTR6M10 followed up 30 patients who had Le Fort I osteotomies for 18 months, and their results are consistent with the present study. Tooth response was lost immediately postoperatively in almost all of the patients; at 2 months, 9.7% of the teeth were responsive to electric pulp stimulation; at 6 months, 78.7%; and at 18 months over 90%. TAJIMA23 studied response to electric pulp testing in 27 cases of Le Fort osteotomy and Le Fort fracture. In this series, 23% of teeth were responsive at 6 months and 71% at 14 months, the canines recovering sensation quicker and more completely than molars, premolars, and incisors. In contrast to LEIBOLD et al. 1 2 , K A H N B E R G r163 E N G S T R O M 10 found canines slower to recover. D I e t al. 5 carried out a histologic examination on 17 maxillary third molars, which were extracted from 10 patients who had Le Fort I osteotomies. The mean follow-up was 40 months. They found that 60% of the completely developed teeth had normal pulpal architecture with an intact odontoblastic layer. There was no evidence of pulpal necrosis, and the peripheral plexus of nerve bundles was seen clearly in most of the sections. None of the teeth in this study were subjected to direct trauma during surgery, as the bone cuts were located at a minimum of 5 mm above the apices. The amount of bone covering the apices was therefore sufficient to allow re-establishment of both the vascular and nerve supply ~8. JOHNSON(~ HINDS9 pointed out that an adequate blood supply is essential for vitality. It has been proposed that cut nerves regenerate in an area where the blood supply has been preserved 13. There is no single vessel essential in maintaining the circulation in the Le Fort I osteotomy because of the abundant anastomoses provided by the maxillary artery 5. The percentage of teeth regaining sensitivity to the electric pulp tester and the rate of return in this study are consistent with these previous studies. Buccal m u c o s a
In the current paper, sensation was tested on the buccal mucosa just above the attached gingiva and below the line of the incision. One previous study 3
18
AI-D& et al.
tried to assess fine touch inside the mouth but abandoned this part of the study as cotton wool proved to be "too unreliable". We found that none of the patients had regained preoperative levels of fine touch sensation in the buccal gingivae at 6 months. After 6 months, one patient had no perception of fine touch at all, the remaining 19 having some sensation but at a reduced level. POSN]CK et al. 19 tested upper lip mucosa 1 year after Le Fort I osteotomy. Fine touch sensation was assessed with Semmes-Weinstein monofilaments, twopoint discrimination with the MacKinnon-Dellon Disk Criminator, and vibration sense with the Biothesiometer. This study found decreased levels of sensation in all modalities compared to preoperative levels. Although there was an objective reduction in sensation, the patients were unaware of any alteration of sensory function. Turning to pin-prick sensation in the buccal mucosa, two other studies have examined this with a dental probe rather than an algesimeter. KAHNBERG & ENGSTR6M1~ noted that in the labiobuccal mucosa, pin-prick sensation was markedly diminished after the vestibular incision during the first 2 months, but was re-established by 6 months. In a survey of 10 patients who underwent maxillary osteotomy a mean of 1 year prior to examination, DE JONGH et al. 3 found that the buccal tissues were less responsive than a control group who had not had surgery. This difference was more marked posteriorly than in anterior sites. In the present study, 17 patients regained some pin-prick sensation at 6 months, and in most of these (15) it was at the same level as preoperatively. Palatal mucosa
In the present study, pin-prick sensation in the palate returned in all cases, in spite of the division of the nasopalatine nerve, provided the greater palatine nerves remained grossly intact at operation. Of the 32 "hemipalates" with an intact GPN, 31 recovered pin-prick sensation to the preoperative level. Other series examined pin prick with a dental probe rather than an algesimeter3,1~ MAGENNIS TM found that palatal sensation, including pin-prick, was not affected by division of the nasopalatine nerve during removal or exposure of maxillary canines. KArrNaERG & ENG-
STROM10 did not detect any reduction in
sensation except in a few patients with previous cleft palate surgery. In contrast, DE JONGH et at. 3 found that pinprick sensation was reduced compared to a control group 14 months postoperatively even though the greater palatine nerves had not been divided. No previous study has examined fine touch on the palate. The current study found fine touch sensation returned in all patients where the GPN was grossly intact, and in 88% sensation had returned to the preoperative level. No previous study has examined patients in whom the greater palatine nerve was divided during surgery. The number of patients with sectioned GPN in this study was small, three patients having the GPN divided bilaterally and two unilaterally, yielding eight "hemipalates" whose nerve was sectioned. All eight "hemipalates" regained some level of pin-prick and fine touch sensation at 6 months. In only one of these "hemipalates" did fine touch sensation return to the preoperative levels, and in this case the contralateral GPN was intact. Five "hemipalates" returned to a preoperative level of pin-prick sensation, and the two cases with an intact contralateral GPN were in this group. Where only unilateral GPN division occurred, sensation seemed to return more quickly on the ipsilateral side than in cases where both GPNs were divided. This suggests some crossover sensation from the intact contralateral nerve, but the numbers are too small for firm conclusions to be drawn. Face
Sensation in the face is rarely affected for any length of time after Le Fort I osteotomy. KAHNBERG • ENGSTR()M10 recorded that infraorbital pin-prick sensation was reduced in all patients where suspension wires had been attached to the infraorbital rims, but noted a return sensation at 2-6 months postoperatively. KARAS et al. 11 examined sensation before and after surgery in 13 patients having Le Fort I osteotomy and 20 patients having mandibular osteotomies. They assessed static light touch with von Frey hairs, moving touch with a no. 2 sable-hair brush, and two-point discrimination with the Boley gauge. In those having maxillary surgery, sensory deficits were detected immediately postoperatively in 49%. After 3 months, all
patients achieved a full return to preoperative levels of fine touch. Moving touch also showed a similar pattern and two-point discrimination improved postoperatively. POSNICK et al. 19 assessed fine touch, two-point discrimination, and vibration sense on the face and lip after Le Fort I osteotomy, but they did not examine the palate. No significant differences could be found in fine touch and vibration sense 12 months postoperatively. In contrast to the findings of KARAS et al. 11, there was an increase in mean postoperative two-point discrimination values in all areas and in all patient groups, but this approached significance only in anterior cheek skin in the patients with unilateral cleft lip. The patients did not complain of any subjective loss of sensation in spite of the increased two-point discrimination distance. All patients in the current study showed a return to normal sensation in all modalities examined within the period of follow-up. This was expected as injury to the infraorbital nerve was due to traction only.
Conclusion
The Le Fort I osteotomy caused alteration of sensation in the maxillary teeth, buccal and palatal mucosa, and the skin of the face. Some of this sensory loss was subtle and may represent an objective alteration in the threshold of sensation rather than subjective numbness or paraesthesia. Sensation, in terms of cold sensation, pin-prick, fine touch, and pulp sensitivity returns to all tissues in spite of division or damage of many nerves serving the area. However, this return of sensation does not always reach preoperative levels. Patients undergoing Le Fort I osteotomy should be warned of the potential for sensory morbidity, particularly if the movement planned suggests that division of the greater palatine nerve may be necessary.
References
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10. KAHNBERG KE, ENGSTROM H. Recovery of maxillary sinus and tooth sensibility after Le Fort I osteotomy. Br J Oral Maxillofac Surg 1987: 25: 68-73. 11. KARASND, BOYD SB, SINN DE Recovery of neurosensory function following orthognathic surgery. J Oral Maxillofac Surg 1990: 48: 124-34. 12. LEIBOLD DG, TILSON HB, RASK KR. A subjective evaluation of the re-establishment of the neurovascular supply of teeth involved in anterior maxillary osteotomy procedure. Oral Surg 1971: 32: 531-43. 13. MACGREGORA. Histology of a pulp following segmental alveolotomy. Br J Oral Surg 1970-1: 8: 292. 14. MAGENNISE Sensory loss associated with palatal flaps fact or fiction? J Irish Dent Assoc 1990: 36: 60-1. 15. MALONEYF, WORTHINGTONP. The origin of the Le Fort I maxillary osteotomy: Cheever's operation. J Oral Surg 1981: 39: 731-4. 16. MATTHEWS B, SEARLE BN. Electrical stimulation of teeth. Pain 1976: 2: 245. 17. PEPERSACKWJ, CHAUSSEJM. Long term follow-up of the sagittal split technique for correction of mandibular prognathism. J Max-Fac Surg 1978: 6: 136-9. 18. PEPERSACK WJ. Tooth vitality after alveolar segmental osteotomy. J Max-Fac Surg 1973: 1: 85-91.
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19. POSNICKJC, AL-QUATTANMM, PITONG. Facial sensibility in adolescents with and without clefts 1 year after undergoing Le Fort I osteotomy. Plast Reconstr Surg 1994: 94: 431-5. 20. POSWILLO DE. Early pulp changes following reduction of open bite by segmental surgery. Int J Oral Surg 1972: 1: 87-97. 21. ROBINSON PE Reinnervation of teeth after segmental osteotomy in the cat. Int J Oral Maxillofac Surg 1986: 15: 152-9. 22. SVARTXZK, ArlLBOR~ G, FINI,m K, NETHANDERG. Nerve disturbance after sagittal split osteotomy. Int J Oral Surg 1983: 12: 279-80. 23. TAJIMAS. k longitudinal study on electrical pulp testing following Le Fort I and Le Fort type fracture. J Max-Fac Surg 1975: 3: 74-80.
Address:
K. M. Coghlan Department of Oral and Maxillofacial Surgery Royal London Hospital Whitechapel, London E1 1BB UK