Neurosensory disturbance with rigid fixation of the bilateral sagittal split osteotomy

J Oral Maxillofac 45:20-26,

Surg

1987

Neurosensory Disturbance with Rigid Fixation of the Bilateral Sagittal Split Osteo tomy GARY J. NISHIOKA, DMD,* MONTE K. ZYSSET, DDS,t AND JOSEPH E. VAN SICKELS, DDS$ Twenty-one patients who underwent bilateral sagittal split osteotomies using rigid fixation were evaluated by neurosensory testing. Neurosensory tests included light touch (LT), brush stroke direction (BSD), two-point discrimination (2-P), and temperature (T). Tests were conducted using the two-alternate forced choice method. The density of neurosensory disturbance was examined as well as the incidence of neurosensory disturbance as it correlated with age of the patient. The incidence of neurosensory disturbance was 45.2% (19/42) to LT, 52.4% (22142) to BSD, 33.3% (14142) to 2-P and 7.1% (3142) to T. The majority of demonstrable neurosensory disturbances were not dense. Increased age was associated with an increased incidence of neurosensory disturbance.

The transoral bilateral sagittal split osteotomy (BSSO) is a versatile technique to advance and setback the mandible. Since its introduction, this procedure has undergone a number of modifications in attempts to improve the original method. Traditionally, the proximal and distal fragments have been stabilized with wire osteosynthesis. In 1974, Spiesslt introduced rigid fixation with compression osteosynthesis using lag screws. Since then, several modifications have been presented including varying the size and type of screws used,2J and bone plating.4 Advocates of rigid fixation feel there are several advantages over non-rigid wire fixation. Among these are early mobilization of the jaws,1-3*5 preservation of maximum interincisal opening,‘j and a decreased incidence of relapse. 1,2,5,7-9Despite many apparent advantages of rigid fixation, the possibility of an increased neurosensory disturbance of

the inferior alveolar nerve by the compression employed with these techniques has been raised. Paulus and Steinhauser’O presented data suggesting that rigid fixation is associated with a slightly higher incidence of neurosensory disturbance than non-rigid fixation. Two groups of patients undergoing a BSSO were evaluated two years after surgery. Of 83 patients, 57% of those with screw osteosynthesis and 50% of those with wire osteosynthesis had a neurosensory disturbance of the inferior alveolar nerve. No statistical analysis was presented. Other authors do not agree that rigid fixation is associated with increased neurosensory disturbance.tg3q5 Souyris2 followed 25 patients who underwent a BSSO with bicortical screw rigid fixation and noted only one patient with a permanent neurosensory disturbance of the inferior alveolar nerve. SpiessLs stressing technique used to split the mandible, reported a reduction from 63% to 25% in neurosensory disturbance in patients who underwent BSSOs. Other workers also feel that neurosensory injuries are technique sensitive.“-I3 These conflicting reports make the clinical picture unclear as to the incidence of disturbed sensibility with rigid fixation of a BSSO. The purpose of this study was to evaluate the incidence and type of neurosensory disturbances with this procedure. Specific neurosensory tests were employed in a strict psychometric format to eliminate test and ob-

Received from The University of Texas Health Science Center, San Antonio, Texas. * Resident, Department of Oral and Maxillofacial Surgery. ? Resident, Department of General Practice. $ Associate Professor, Co-Director of the Dentofacial Deformity Clinic. Department of Oral and Maxillofacial Surgery. Address correspondence and reprint requests to Dr. Van Sickels: Dentofacial Deformity Clinic, The University of Texas Health Science Center, 7703 Floyd Ave Drive, San Antonio, TX 78284- 7903. 0278-2391187 $0.00 + .25

20

NISHIOKA

21

El‘ AL

server variability seen in other studies. The results obtained should provide a baseline for future comparison studies. Materials

and Methods

Twenty-one patients treated in the Department of Oral and Maxillofacial Surgery at The University of Texas Health Science Center at San Antonio were retrospectively studied. These patients had previously undergone a BSSO using rigid fixation with three 2 mm bicortical screws, as described by Jeter et a1.3 There were 14 females and seven males ranging from 15 to 43 years (mean age, 28 years). Sixteen patients underwent advancements, four with concomitant genioplasties. and five patients underwent setbacks. No maxillary surgical procedures were performed. The mean period from surgery to neurosensory testing was 21.2 months (Range: six to 38 months). All data were collected by a single investigator. Prior to neurosensory testing, patients answered a short questionnaire which was verbally administered by the interviewer (Table 1). These questions were intended to elicit subjective information about general satisfaction with the surgical procedure, presence or absence of a neurosensory disturbance, and the degree of improvement since surgery (if such a disturbance existed). Additionally, impact of the neurosensory disturbance (if present) on the quality of life, and impression of the cost: benefit ratio of surgery. using neurosensory disturbance as the single variable of cost were also assessed. After answering the questionnaire, patients underwent a battery of neurosensory tests consisting of light t-ouch (LT), brush stroke direction (BSD). two-point discrimination (2-P), and temperature CT). The first two tests (LT. BSD) selectively discriminate for large myelinated, quickly adapting, A alpha nerve fibers which comprise 90% of the A axons.14 Two-point discrimination selects for large myelinated, slowly adapting, A alpha nerve fibers Table 1.

Patient Questionnaire

I, What complaint

do you have.

if any. about

your

surgery?

2. Do you, have any numbness of your lower hp. chin. or tongue (unilateral/bilateral)‘? Does the numbness effect daily function speech, eating, etc.‘? 3. a) Did you have any numbness b) Has this numbness

improved

immediately

after surgery’?

since the time of surgery?

4. a) Would you have the surgery again knowing know now about the possible numbness’? b) Would you have the surgery again surgery that your present numbness

what

you

if you knew prior to would be permanent’?

FIGURE I. Dotted area test sites.

areas

outline

the infraorbital

and

mental

which comprise the remaining 10% of the A axons.t4 Temperature selects for small myelinated and unmyelinated A delta and C nerve fibers.t4-l6 A total of six sites were tested (Fig. 1). The mental region, corresponding to the inferior alveolar nerve distribution, was divided into four quadrants, upper and lower right, and upper and lower left. Two sites on the upper lip, corresponding to the right and left infraorbital nerve distributions, served as controls for the respective sides. To minimize patient bias due to variable psychologic motivational parameters, the two-alternate forced choice method of testing was employed for LT. BSD. and temperature. This method eliminates the need for patients to rely on an absolute internal standard of yes responses, seen in yes/no testing. t7 With their eyes closed, patients were presented two time intervals several seconds apart. cued by the interviewer’s voice saying “one” (pause) “two”. During the first or second interval, a stimulus that was previously described and demonstrated to the patient, was delivered to the test site. Patients were then “forced” to choose the period in which the stimulus was delivered. The interval in which the known stimulus was presented was selected randomly by coin toss and indicated on the test sheet prior to testing. Each site was tested in blocks of 1.5 forced choice trials. The re-

22

NEUROSENSORYDISTURBANCEOF BILATERALSAGGITALSPLIT OSTEOTOMY

sults were recorded as the number of correct responses. Light touch and BSD were performed with Von Frey hairs (VFH) as the known stimulus. With LT the least stiff VFH which the patient was able to give an 80% (12/15 trials in a block) or greater correct response in the infraorbital control site, was selected. This size was then used for the mental area test sites for that side. With BSD a l-cm brush stroke was given over the infraorbital control area from right to left during one time interval and left to right during the other time interval. Patients were asked to indicate in which of the two time intervals the stroke moved from right to left. Again, the least stiff VFH with which the patient was able to give an 80% or greater correct response was selected as the test size for the mental area test sites for that side. A nerve was considered to have a neurosensory disturbance (NSD) if there was less than an 80% correct response in one or both of the mental sites. Two-point discrimination testing was accomplished using a caliper and millimeter ruler. The test was conducted by beginning with the calipers closed and progressively opening them in OS-mm increments until the patient could discriminate two points. This distance was then recorded. Care was taken to ensure that the caliper points touched the cutaneous surface at the same time. Each site was tested with a block of five trials and the values were then averaged. It was arbitrarily decided that averaged distances greater or less than 2 mm of the control value for that side would be considered abnormal. This criterion currently must be viewed with caution since no studies exist which provide baseline data for normals relating to these particular nerves. Temperature was tested using Minnesota Thermal Disks.‘5*‘6 The four materials used in the disks are polyvinyl chloride, glass, copper, and steel. Glass and polyvinyl chloride requires the greatest level of thermal discrimination among the materials, glass being slightly colder than polyvinyl chloride. These two disks were used because they were the most discriminating and consistently produced greater than 80% correct responses in the control sites. This test was conducted by using a rubber dam with a l-cm square cut in the center. The opening was placed over the test site thus blocking out thermal detection to adjacent areas. Each disk was randomly presented, one in the first time interval and the other in the second. The patient was required to identify the time interval in which the colder disk (glass) was presented. Again, a nerve was considered to have a NSD if there was less than 80% correct response in one or both of the mental test sites. The data were statistically analyzed using either

the Mann-Whitney U test, chi-square test, Pearson’s product moment correlation test.

or

Results SUBJECTIVE Fourteen of 21 patients (66.7%,) had positive comments about the surgery, three (14.3%) had negative comments, and four (19%) had no comments. Positive comments varied from improved esthetics to improved bite to fewer headaches; there was no trend. Negative comments were generally related to NSD. Fifteen of 21 patients (71.4%) reported having a NSD. Thirteen of these patients (86.7%) stated the NSD did not affect their quality of life. The remaining two patients (13.3%) stated their quality of life was adversely affected, and only one patient reported no NSD immediately after surgery. Of the remaining 20 patients who reported a NSD immediately after surgery. 19 (95%) stated their NSD had improved since surgery. Only one patient (5%) reported no improvement. When the patients who reported having a NSD were asked if they would have the surgery again if they had known prior to surgery their present NSD would never improve, 13 (86.6%) said yes, one (6.7%) said no, and one (6.7%) was unsure. Neurosensory

testing

results

Forty-two inferior alveolar nerves were tested (Table 2). All patients with NSDs were found to be hypoesthetic except patient 11 and 20. Patient 11 was anesthetic, and patient 20 subjectively reported sensations suggestive of a hyperesthesia. It was difficult to ascertain from hospital records if in any of the cases the nerves were visibly injured. Interestingly, the purported hyperesthetic patient had a normal neurosensory examination by all test modalities. One patient (number 7) had no NSD after surgery and had all normal test responses. A NSD to LT, BSD, or T singularly or in combination, was demonstrated in 71.4% (15/21) of the patients. This correlated significantly with the subjective incidence of reported NSD (P < 0.05). However, one patient reported no NSD, although a NSD could be demonstrated by neurosensory testing. When examining the incidence of NSD by numbers of nerves instead of by patients, 61.9% (26/42) of the nerves demonstrated a NSD, to LT, BSD, or T singularly or in combination. Light

touch

A neurosensory disturbance to LT was demonstrated in 45.2% (19/42) of the nerves, which was

23

NISHIOKA

ET AL.

Table 2.

Summary of Collected Data

Pt. No.

BSSO

Time (mob

Subjective NSD

NL Exam BSD

NL

Objective NSD

Quality of Life

Light Touch

BSD

TwoPoint

Tempera-

ture

Exam LT

Age

Sex

I

30

M

Adv

36

+

t

No

R-nl L-abn

R-abn L-abn

R-nl L-nl

R-nl L-nl

Ltl

Ri3 L-t?-

2

32

F

Adv

29

+

+

Yes

R-abn L-abn

R-abn L-abn

R-abn L-abn

R-nl L-abn

R+ I L+I

R-t L+

I I

3

36

F

Adv

32

+

t

No

R-abn L-abn

R-abn L-nl

R-abn L-nl

R-nl L-nl

R+l L+ I

R+

I

4

43

M

Adv

25

+

+

No

R-abn L-abn

R-abn L-abn

R-nl L-nl

R-nl L-nl

R+ I 1, 3. 1 I

R+3 L+l

5

38

F

Set back

27

+

+

No

R-abn L-nl

R-abn L-nl

R-nl L-nl

R-nl L-nl

R +- I

Rt

6

30

M

Adv (genie)

26

+

+

No

R-abn L-abn

R-abn L-abn

R-nl L-nl

R-nl L-nl

R+?. 1. + I

R> I2 L+3

7

21

F

Set back

19

_

_

No

R-nl L-nl

R-nl L-nl

R-nl L-nl

R-nl L-nl

8

41

F

Adv (genie)

24

+

+

No

R-nl L-abn

R-abn L-abn

R-nl L-nl

R-nl L-nl

1, + I

R+l L+I

9

34

F

Adv

39

+

+

No

R-nl L-abn

R-n1 L-nl

R-nl L-n1

R-nl L-nl

L+

I

IO

24

M

Set back

11

+

+

No

R-abn L-nl

R-abn L-abn

R-nl L-nl

R-nl L-nl

R+

I

I1

29

F

Adv (genie)

II

+

+

Yes

R-abn L-abn

R-abn L-abn

R-abn L-abn

R-abn L-abn

I2

I6

F

Adv

I9

_

_

No

R-nl L-n1

R-nl L-nl

R-nl L-nl

R-nl L-nl

13

19

F

Adv

I5

+

+

No

R-abn L-abn

R-nl L-abn

R-nl L-nl

R-nl L-nl

14

31

F

Set back

35

_

+

No

R-nl L-nl

R-nl L-nl

R-abn L-abn

R-nl L-nl

I5

15

F

Adv

6

_

+

No

R-nl L-n1

R-nl L-nl

R-abn L-abn

R-n1 L-nl

16

31

F

Adv (genie)

30

+

+

No

R-abn L-nl

R-abn L-abn

R-abn L-abn

R-nl L-nl

I7

16

M

Adv

I8

+

+

No

R-nl L-nl

R-n1 L-abn

R-abn L-n1

R-nl L-nl

18

27

M

Set back

11

+

+

No

R-n1 L-abn

R-nl L-n1

R-abn L-abn

R-nl L-nl

19

17

F

Adv

20

-

_

No

R-nl L-nl

R-nl L-nl

R-nl L-nl

R-nl L-nl

20

29

F

Adv

6

+

_

No

R-nl L-n1

R-nl L-nl

R-nl L-nl

R-nl L-nl

21

28

M

Adv

6

_

+

No

R-nl L-nl

R-abn L-abn

R-nl L-n1

R-nl L-nl

Anesthesia

Rt L+

1

I I

Anesthesia

R+2 L+2

L+l

R+l

R+5 L+5 L+9

L+

I

R+2 L+2

Abbreviations: (genie) = concomitant genioplasty procedure; R = right; L = left; abn = abnormal; nl = normal; adv = advancement; + II = Von Frey Hair size above test size needed to produce a normal examination; and >n = largest Von Frey Hair size used without obtaining a normal examination.

significant when compared to the control area (P < 0.001). When patients with genioplasties were eliminated, 841.2% (14/34) of the nerves were found to be abnormal; this was also significant (P < 0.001).

Brush Stroke Direction A neurosensory response to BSD was noted in 52.4% (22/42) of the nerves (P < 0.001). When pa-

24

NELJROSENSORY DISTClRBANCE OF BILATERAL.SAGGITAL.St'l.l~I OS'I‘kOTOMY

tients with genioplasties were eliminated, 38.3% (13134) of the nerves were found to be abnormal, which was also significant (P < 0.001). Although a general correlation between NSD and perception of LT and BSD was noted, some disparity did exist. Four nerves abnormal to LT were normal to BSD. Conversely, six nerves were normal to LT but were abnormal to BSD. TWO-POINT DISCRIMINATION(2-P)

nerves produced a normal examination. resulting in a further significant reduction in NSD as measured by BSD to 21.47~ (9142) (P < 0.01). When patients who underwent a concomitant genioplasty procedure were eliminated, only 17.6%’ (6134) of the nerves demonstrated a NSD by increasing the VFH one size. This reduction in NSD was significant at the P < 0.05level. Increasing the VFH two sizes significantly reduced the incidence of NSD as measured by BSD to its lowest value of 8.8% (3134) (P

< 0.01). A significant NSD to 2-P discimination in 33.3% Patient II, due to the extremely dense NSD to all (14/42) of the nerves was demonstrated (P < 0.001). test modalities, underwent evaluation by measureNo discernible pattern existed correlating 2-P disment of brainstem evoked potentials. The braincrimination to LT or BSD. stem evoked potential shortly after the patient was TEMPERATURE(T) found to be anesthetic by neurosensory testing recorded an elevated threshold, but a normal latency Neurosensory disturbance to thermal discriminaand amplitude. When the patient was retested aption was seen in 7.1% (3142) of the nerves. Patient proximately two months later there wab a 100% re1I, who was found to be anesthetic by all testing duction in threshold (8 to 4 mA). Clinically. this modalities. accounted for two of these nerves. Temcorrelated with recovery of some thermal discrimiperature discimination was significantly preserved, nation. The patient was now also able to discrimieven when a NSD could be demonstrated in the nate between polyvinyl chloride and copper with same nerve using other testing modalities (P < the Minnesota Thermal Disks. With a longer time 0.05). interval perhaps, her NSD will show further improvement. DENSITY OF INJURY The incidence of NSD in patients who underwent a concomitant genioplasty procedure was 75% (6/X) Density of injury was measured by the density of when measured by LT, 100% (818) when measured the NSD to both LT and BSD. Progressive inby BSD, 50% (4/8) in response to 2-P, and 25% (318) creases in size of VFHs beyond the test size to T measurement. needed to produce a normal neurosensory examinaWhen the incidence of NSD to LT. BSD. and T tion, revealed that these neurosensory disturbances (excluding 2-P) was correlated with age there was a were generally not very dense. When a dense NSD remarkable decrease in response to LT and BSD existed. it was often associated with a concomitant with increasing age. The incidence of NSD when genioplasty procedure. measured by either LT or BSD was 30’;: (3110) in When the VFH was increased one size above the patients less than 30 years: 58c/r (7112) in patients test size, 13 previously abnormal nerves demon20-30 years: 75% (12/16) in patients 30-40 years: strated a normal neurosensory examination to LT. and 100% (414) in patients older than 40 years. This resulted in a significant decrease in NSD as measured LT from 45.2%’ (19/42) to 14.3% (6/42) When patients with concomitant genioplasties were excluded, this same trend in NSD was seen. The (P < 0.01). Increasing the VFH two sizes resulted in three additional previously abnormal nerves proincidence of NSD measured by either LT or BSD ducing a normal examination. This significantly dewas 30% (3110) in patients less than 20 years: 50% (5110) in patients 20-30 years: 66.7% (8112) in pacreased the NSD to LT even further to 7. I% (3142) (P < 0.001). With the three remaining abnormal tients 30-40 years; and 100%’(213) in patients older than 40. The increase in NSD with increasing age nerves a normal neurosensory examination to LT was significant at the P < 0.05level. Temperature could not be obtained using VFHs 10 sizes larger discrimination tended to be well maintained than the original test VFH size. Two of these three throughout the entire age range of our patient popunerves were in patients who had a concomitant gelation. nioplasty. By increasing the VFH one size, IO previously abnormal nerves demonstrated a normal examinaDiscussion tion to BSD. This resulted in a significant decrease in NSD as measured by BSD from 52.45% (22142) to A potential drawback of this study was the use of the unoperated infraorbital nerve distribution as a 28.6% (12/42) (P < 0.05). Increasing the VFH two sizes, an additional three previously abnormal control. To our knowledge, data does not exist

NISHIOKA

ET AL.

showing that sensibility of the infraorbital nerve is comparable to the inferior alveolar nerve. Therefore, we studied 14 normal unoperated patients. Although our sample size was small, our data show the sensibility of these two nerves is not significantly different (P < 0.25). However, there is some variability among subjects. Therefore, based on our small preliminary study, the unoperated infraorbital nerve can serve as a control. Our incidence of NSD of 71.4% (15121 patients) when measured by LT, BSD, and T combined is higher than in previous studies reported in the literature in which rigid fixation was used. Souyris2 reported a 4% (l/25 patients) incidence of disturbed sensibility., SpiessP reported a 25% (26/98 patients) incidence, and Paulus and Steinhauser’O reported a 57% (33/58 patients) incidence. Of the three test modalities, LT is the most representative standard by which to compare the incidence of NSD with the previous studies since it does not appear that BSD or T were utilized in these studies. When this is done, our percentage was less than Paulus and Steinhauser (57%),l” but is greater than that of Souyris (4%),* and Spiessl (25%).5 Whether the testing techniques used by these authors were not as sensitive as the ones used in this study, or whether other factors contributed to these differences is unknown. The question of whether osteosynthesis with rigid fixation techniques produces a higher incidence of NSD than non-rigid fixation techniques with a BSSO is difficult to assess using non-rigid fixation data from previous studies. The incidence of NSD with non-rigid fixation is extremely variable, ranging from 0% to 85% for irreversible lesions.10J2J3J*-36 Evaluation is further complicated because none of these studies used a testing method to control patient bias. Additionally, methods of non-rigid fixation varied from splint only, to transosseous wires, to circumferential wires. As with surgical technique, the method of neurosensory testing was also not standardized, Of the previous studies, Walter and Gregg’s3’ is perhaps the most comprehensive. They utilized LT, BSD, 2-P discrimination, pin tactile discrimination. heat, and pin prick (15 g of pressure) and found an 84.6% (22/26) incidence of NSD. Our incidence of 76.2 (32/42) using LT, BSD, 2-P discrimination, and T was slightly less. A disadvantage of that study was that they did not control for patient bias. Peppersack and Chaussei3 reported that 38% (15/39) of their patients who claimed no subjective loss of sensibility did, in fact, have some degree of NSD, but were unaware of it. This finding contrasts sharply with our patients who correlated significantly the incidence of subjective perception of a

25

NSD with a demonstrable NSD. Perhaps this represents a cultural bias. Interestingly, our data supported previous reports that BSD is the test most greatly affected. Bailey and Bays,37 and Frost et al.,38 both reported BSD to be the most affected test when a NSD could be demonstrated following various surgical procedures of the mandible. Frost et a1.38suggested BSD requires complex integrated sensory functions that could be lost secondary to deafferentiation changes in the synaptic integration centers accompanying loss of peripheral nerves. The duration of this type of injury is unknown. It may be that with increased time, this deficit could be corrected by learning. The maintenance of thermal discrimination in this population has several possibilities; that small fibers survive injury better; they are better able to regenerate; or our test was not sufficiently sensitive to illustrate such changes. In a previous study with visor osteotomies, this same test showed discriminatory ability. 37 Perhaps, small fibers have a greater ability to regenerate, since the distal neurilemmal tubes are constricted; this same constriction may inhibit passage of larger axon fibers.39 Undoubtedly, there is a higher incidence of neural injury with a visor osteotomy than with a BSSO. The lack of a dense NSD seen in a large percentage of our patients was an interesting finding. These data are consistent with the fact only two patients reported their NSD adversely affected their quality of life. Possible explanations for this observation include elevation of receptor threshold. decrease in receptor density, or perhaps loss of original fiber diameter.40 Although the sample size was small, our data strongly suggested concomitant genioplasty procedures increase the incidence and density of the NSD. Previous studies have suggested age may be an important variable in the incidence of NSD. MacIntosh34 found the incidence of NSD persisting at one year postoperatively was overwhelming in the patients older than 40 years. This finding was so dramatic, Macintosh further stated he no longer utilizes the BSSO in patients over 40 years of age. Schende128 found no persistent NSD occurred in 12 BSSO patients who were operated between the ages of 8- 16 years. Our data support these studies, showing that the incidence of NSD increased linearly with age. Although our sample size was small we had a 100% (4/4) incidence of NSD with patients over 40 years, and a 12.5% (l/8) incidence with patients less than 17 years (excluding 2-P discrimination data). These age related differences may relate to differences in the character of the bone and the ease with which the splits are made.

26

NEUROSENSORY

DISTURBANCE

Summary The results of this study, when compared to the literature, do not support the contention that rigid fixation with the BSSO causes a higher incidence of NSD than non-rigid fixation. In contrast to the findings of Peppersack et al..i3 patients in this study who subjectively reported a NSD almost always had a demonstrable NSD by neurosensory testing. Similar to findings from Bailey and Bays,37 and Frost et al.,38 BSD was the test most affected. The most remarkable findings of this study were: 1) the preservation of thermal discrimination in patients with a NSD to other test modalities; 2) lack of a dense NSD in a large percentage of patients with a demonstrable NSD; 3) an increase in incidence and density of NSD in patients who underwent a concomitant genioplasty procedure; and 4) association of increased age with an increased incidence of NSD. References 1. Spiessl B: Osteosynthese bei sagittaler osteotomie nach Obwegeser-Dal Pont. Schuschardt. Fortschritte der Kieferund Gesichtschirurgie. 18:145, 1974 2. Souyris F: Sagittal splitting and bicortical screw fixation of the ascending ramus. J Maxillofac Surg 6: 198. 1978 3. Jeter TS, Van Sickels JE. Dolwick MF: Modified techniques for internal fixation of sagittal ramus osteotomies. J Oral Maxillofac Surg 42:270. 1984 4. Luhr GH: Luhr Mini-Compression System. For surgery of the mid-face skeleton and orthognathic surgery. Howmedica Brochure. 1985. pp 18-19 5. Spiessl B: The sagittal splitting osteotomy for correction of mandibular prognathism. Clin Plast Surg (Symp Maxillofac) 9:491, 1982 6. Aragon SB. Van Sickels JE: Effects of early physiotherapy on mandibular opening following orthognathic surgery. J Dent Res 64:216, 1985 (abstr 373) 7. Schmoker R. Spiessl B. Gensheimer TH: Funktionsstabile osteosynthese und simulographie bei der sagittalen osteotomie des aufsteigenden astes. Eine Vergleichende Linische Unterschung. 86:582. 1976 8. Hadjianghelou 0: Zurcher erfahrungen mit der zugschraubenosteosynthese bei der sagittalen splatung der ramus. Fortschr. Kiefer-Gesichtschir 26:94, 1981 9. Van Sickels JE, Flanary CM: Stability associated with mandibular advancement treated by rigid osseous fixation. J Oral Maxillofac Surg 43:338. 1985 _ 10. Paulus GW. Steinhauser EW: A comnarative studv of wire osteosynthesis versus bone screws in the treatment of mandibular prognathism. Oral Surg 54:2. 1982 1I. Brusati R, Fiamminghi L, Sesenna E, et al: Functional disturbances of the inferior alveolar nerve after sagittal osteotomy of the mandibular ramus: operating technique for prevention. J Maxillofac Surg 9: 123, 1981 12. Fiamminghi L. Aversa C: Lesions of the inferior alveolar nerve in sagittal osteotomy of the ramus. J Maxillofac Surg 7: 125. 1979 13. Peppersack WJ. Chausse JM: Long term follow-up of the sagittal splitting technique for correction of mandibular prognathism. J Maxillofac Surg 6: 117, 1978 14. Wilgis EFS: Techniques for diagnosis of peripheral nerve loss. Clin Orthop 163:8. 1982 IS. Dyck PJ, Thomas PK. Lambert EH. et al: Peripheral Neuropathy, 2nd ed. Philadelphia, WB Saunders, 1984, pp 1103-1138

OF BILATERAL SAGGITAL SPLIT OSTEOTOMY

16. Dyck PJ, Curtis DJ. Bushek W. et al: Discription of “Minnesota Thermal Disks” and normal values of cutaneous discrimination in man. Neurology 24:325. 1974 17. Sekular R, Nash D. Armstrong R: Sensitive. objective procedure for evaluating response to light touch. Neurology 23:1282. 1973 18. Kole H: Results, experience, and problems in the operative treatment of anomalies with reverse overbite (mandibular protrusion). Oral Surg 19:427, 1965 19. White RP Jr, Peters PB. Costich ER. et al: Evaluation of sagittal split-ramus osteotomy in 17 patients. J Oral Surg 27:85 I. 1969 20. Guernsey LH. DeChamplain RW: Sequelae and complications of the intraoral sagittal osteotomy in the mandibular rami. Oral Surg 32:176, 1971 21. Grimm VG. Beitlich E: Kritische bewertung der operationsergebnisse von IO1 progeniefallen unter besonderer berucksichtigung des verfahrens nach Obwegeser-Dal Pont. Dtsch Zahn Mund und Kieferheil 61:295, 1973 22. Niederdellmann H, Dieckmann J: Neurologische storungen nach chirurgischer korrektur der progenie und mikrogenie. Schuschardt K: Fortschr Kiefer Gesichtschir 18:186. 1974 23. Koblin 1. Reil B: Die sensibilitat der unterlippe nach schonung bzw. durchtrennung des nervus alveolaris inferior bei Progenieoperationen. Schuschardt K: Fortsch Kiefer Gesitschir 18: I5 I, 1974 24. Wang JH, Waite DE: Evaluation of the surgical procedure of sagittal split osteotomy of the mandibular ramus. Oral Surg 38: 167. 1974 25. Freihofer HPM Jr. Petresevic D: Late results after advancing the mandible by sagittal splitting of the rami. J Maxillofac Surg 3:250, 1975 26. Jonsson E. Ahlborg G. Nystrom 0. et al: The sagittal splitting technique-a follow-up study. Int J Oral Surg 5: 172, 1976 27. Broadbent TR. Woolf RM: Our experience with sagittal split osteotomy for retrognathia. Plast Reconstr Surg 59:860. I977 28. Schendel SA, Wolford LM. Epker BN: Mandibular deficiency syndrome. J Oral Surg 45:364. 1978 29. Hovinga J, Kradl ER. Roorda LAM: A follow-up of osteotomies for dysgnathia. J Maxillofac Surg 7:271. 1979 30. Willmar K. Hogeman K-E. Thiseus S: Sagittal split osteotomy in our experience. Stand J Plast Reconstr 13:445. I979 31. Walter JM, Gregg JM: Analysis of postsurgical neurologic alteration in the trigeminal nerve. J Oral Surg 37:410. 1979 32. Schendel SA, Epker BN: Results after mandibular advancement surgery: an analysis of 87 cases. J Oral Surg 38:265. 1980 33. Simpson W: Problems encountered in the sagittal split operation. Int J Oral Surg 10:8l, 1981 34. Macintosh RB: Experience with the sagittal orteotomy of the mandibular ramus: a 13-year review. J Maxillofac Surg 8:151, 1981 35. Martis CS: Complications after mandibular sagittal split osteotomy. J Oral Maxillofac Surg 42: 101. 1984 36. Zaytoun HS Jr. Phillips C, Terry BC: Long-term neurosensory deficits following transoral vertical ramus and sagittal split osteotomies for mandibular prognathism. J Oral Maxillofac Surg 44: 193. 1986 37. Bailey PH. Bays RA: Evaluation of long-term sensory changes following mandibular augmentation procedures. J Oral Maxillofac Surg 42:722. 1984 38. Frost DE, Gregg JM. Terry BC. Fonseca RJ: Mandibular interpositional and onlay bone grafting for treatment of mandibular bony deficiency in the edentulous patient. J Oral Maxillofac Surg 40:353. 1982 39. Choukas NC, Todo PD, Nolan RE: A histologic study of the regeneration of the inferior alveolar nerve. J Oral Surg 32:347. 1974 40. Gutman E, Sanders FK: Recovery of fiber numbers and diameters in the regeneration of peripheral nerves. J Physiol 101:489, 1943