Mandibular range of motion with rigid/nonrigid fixation Steven B. Aragon, D.D.S.,* and Joseph E. Van Sickels, D.D.S.,** San Antonio, Texas

UNIVERSITY OF TEXAS HEALTH SCIENCE CENTER AT SAN ANTONIO

Decreased mandibular range of motion that followed orthognathic surgery and that was treated by wire osteosynthesis and 6 weeks of maxillomandibular fixation (MMF) has been previously documented. The present study evaluated maximum interincisal opening (MIO) in 49 subjects undergoing a bilateral sagittal ramus osteotomy (BSRO) with advancement or a BSRO with advancement and a concomitant LeFort I maxillary osteotomy with the patients having either rigid or nonrigid fixation. The group with rigid fixation had early function and mild physiotherapy. The nonrigid group had wire osteosynthesis, MMP that was maintained for 6 weeks, and no postoperative physiotherapy. Patients who underwent a BSRO with rigid fixation experienced a 3.5 mm decrease in MI0 (6.9%). Those who had a BSRO and a LeFort I osteotomy with rigid fixation had a 3.3 mm decrease in MI0 (6.6%). In contrast, nonrigidly fixed BSRO subjects had a 16.6 mm decrease (29.6%), while those who underwent a combined BSRO and LeFort I osteotomy had a 13.9 mm decrease (26.1 %I. This study showed that rigid fixation combined with early function and mild physiotherapy resulted in improved MI0 postoperatively, as compared to the MI0 in a group in which these treatments were not used. (ORAL SURG. ORAL MED. ORAL PATHOL. 1987;63:408-11)

R ecently, several studies have shown decreased mandibular range of motion in patients who had orthognathic surgery.‘,* Storum and Bell,’ while evaluating several surgical procedures, noted a mean postoperative maximal interincisal opening (MIO) of 35.1 mm in patients who underwent bilateral sagittal ramus osteotomy (BSRO) to advance the mandible. This was a significant reduction in com- parison to a control group with a mean MI0 of 54.8 mm.3

Aragon and colleagues2 studied patients undergo- ing a variety of surgical procedures. Those who underwent a BSRO with advancement of the mandi- ble experienced a 16.8 mm reduction in MIO, while subjects who underwent a BSRO with mandibular advancement and a concomitant maxillary LeFort I osteotomy experienced a reduction of 13.9 mm. In these studies, wire osteosynthesis was used along with a 6-week period of maxillomandibular fixation (MMF). To combat hypomobility during 6 weeks of MMF following orthognathic surgery, a vigorous

*In private practice, San Antonio, Texas. **Associate Professor, Department of Oral & Maxillofacial Surgery.

physiotherapy protocol has been suggested and shown to be effective.4+S

Early function following rigid fixation of an osteo- tomy has been advocated as an advantage of this type of osteosynthesis. However, it has not been shown whether this will prevent the hypomobility noted to occur with wire osteosynthesis and MMF. The pur- pose of this study was to examine the effects of rigid fixation, early function, and mild physiotherapy on the mandibular opening following maxillary osteoto- my and BSRO with mandibular advancement or only a BSRO for advancement of the mandible. The results were compared to a previous sample group that had undergone the same operations and been treated by wire osteosynthesis and a 6-week period of MMF.

METHODS

Patients were divided into two groups. Group I included those who had rigid fixation, early function, and mild physiotherapy. This group was further subdivided into a group that had a BSRO with mandibular advancement (BSRO-RF) and a group that had a LeFort I maxillary osteotomy and con- comitant BSRO advancement (BSRO/LFI-RF). Bicortical screws measuring 2 mm in diameter were

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Mandibular range of motion with rigid/nonrigid fixation 409

Table I. Demographic data on patients

Surgical procedures

Group I BSRO-RF BSRO/LFI-RF Group II BSRO-NR BSRO/LFI-NR

No. of Age patienis W

15 25.1 11 24.9

12 29.1 11 27.6

M:F F/U ratio Wl

5:lO 10.1 I:10 8.2

4:8 13.0 3:8 15.6

used to rigidly fix the mandibular osteotomy.6 Bony plates were used for stabilization in the maxillary procedures, as described by Van Sickels and col- leagues.’ The diet for patients in this group was as follows: weeks 1 to 2, liquids and soups; weeks 2 to 4, foods such as scrambled eggs and oatmeal (minimal chewing); weeks 4 to 8, progressive increase in food consistency (for example, sandwiches); week 8, a regular diet as tolerated.*

The physiotherapy was self-administered by the patient. During the first 2 weeks, patients were instructed not to exercise, but to continue their diet progression as described. During weeks 2 to 4, they were instructed to increase their opening with very mild nonassisted active range of motion exercises. An MI0 of 25 to 30 mm by week 4 was arbitrarily established as the goal. During weeks 4 to 8, the patient was told to be more aggressive in exercising, gradually incorporating digital assistance. If 40 mm of MI0 was not achieved by week 8, the patient was told to become more vigorous in active digital assis- tance to increase the MI0 close to preoperative levels.

Group II patients, as reported previously,2 had nonrigid wire osteosynthesis and MMF for at least 6 weeks. They underwent no postoperative rehabilita- tion. This group was also subdivided into those patients who had an isolated BSRO with mandibular advancement (BSRO-NR) and those who underwent a concomitant LeFort I osteotomy and a bilateral sagittal ramus osteotomy (BSRO/LFI-NR). A supe- rior border wire with a high distal and low proximal orientation was placed as described by Epker.9 Tran- sosseous wires were used for stabilization in the LeFort I osteotomy procedures. The MI0 was mea- sured before surgery and a minimum of 6 months after surgery in all patients.

The MI0 was defined as the greatest distance from the incisal edge of the maxillary central incisors to the incisal edge of the mandibular central incisors while the jaw was open. The measurement was then corrected to take into account overbite or open bite.

Table II. Preoperative and postoperative maximal interincisal opening (MIO)

Group I BSRO-RF 52.6 + 4.9 49.1 f 6.5 3.5 BSRO/LFI-RF 41.6 ic 5.6 44.3 k 1.2 3.3 Group II BSRO-NR 56.1 + 1.2 39.9 * 6.8 16.8 BSRO/LFI- 49.8 -i- 5.2 35.9 +- 1.7 13.9

NR

For example, if the patient had a 2 mm overbite and an uncorrected MI0 of 50 mm, then the corrected MI0 would be 52 mm. Similarly, if the patient had a 2 mm open bite with an uncorrected MI0 of 50 mm, then the corrected MI0 would be 48 mm. The preoperative and postoperative means for MIO, the mean reduction in MIO, and standard deviations were calculated for each subgroup. The data were analyzed by using Student’s t test for paired observa- tion, and also by using the one-way analysis of variance followed by Newman-Keuls multiple com- parison test to compare the mean reductions between the groups. Correlations between the change in MI0 and the amount of surgical advancement, the follow- up period, and age were evaluated with Pearson’s coefficient correlation. Only differences of p < 0.05 were considered significant.

RESULTS

The demographic information regarding the patient sample is provided in Table I. A mean advancement of 5.7 mm (range 4 to 9 mm) was recorded for Group I patients (BSRO-RF). The mean preoperative MI0 of 52.6 mm was reduced by 3.5 mm to 49.1 mm (Table II) postoperatively (p < 0.05). There was no significant correlation between the amount of reduction in MI0 and the amount of advancement (r = -0.3110) or the length of follow-up (r = 0.2057). Likewise, there was no correlation between the MI0 reduction and age of the patient (r = 0.2743). The average length of MMF was 1.9 days.

A mean advancement of 4.7 mm (range 2 to 7 mm) was recorded for the BSRO/LFI-RF subgroup. The MI0 was decreased 3.3 mm from 47.6 mm to 44.3 mm (p < 0.05). The MI0 reduction was not significantly correlated to the amount of advance- ment (r = 0.0557), length of follow-up (r = 0.2152),

410 Aragon and Van Sickels Oral Surg. April, 1987

0, 1 , ’ , ’ I ’ I ’ I

0 5 IO 15 20 25

Time (wks) Fig. 1. Trend in maximal interincisal opening: sagittal split (RF).

or age of the patient (r = 0.1943). The mean dura- tion of MMF was 4.6 days.

For the 12 BSRO-NR patients in Group II, an average advancement of 7.3 mm (range 4 to 12 mm) was recorded, with the procedure followed by 6 weeks of MMF. The MI0 was reduced 16.8 mm from 56.7 to 39.9 mm (p < 0.05). There was no significant correlation between the MI0 reduction and the amount of surgical advancement (r = 0.5067), follow-up time in months (r = 0.3030), or patient’s age (r = 0.0438).

The patients in the BSRO/LFI-NR subgroup underwent a mean mandibular advancement of 6.8 mm (range 5 to 12 mm) with concomitant maxillary repositioning and 6 weeks of MMF. The preoperative MI0 of 49.8 mm decreased to 35.9 mm postopera- tively. No correlation was found between the amount of MI0 reduction and the amount of mandibular advancement (r = -0.4825) or follow-up time (r = -0.1283). However, a significant correlation was found between MI0 reduction and patient age (r = 0.8096).

The one-way analysis of variance revealed a signif- icant (p < 0.01) difference in the mean decrease in MI0 among the four subgroups (F = 11.7466). The BSRO-RF subgroup did not differ significantly from the BSRO/LFI-RF subgroup (3.5 and 3.3 mm, respectively), but it did differ significantly from both the BSRO-NR and BSRO/LFI-NR subgroups (16.8 and 13.9 mm, respectively). The BSRO/ LFI-RF subgroup likewise differed significantly from the BSRO-NR and BSRO/LFI-NR sub- groups.

The MI0 reduction in the BSRO-NR subgroup did not differ from the BSRO/LFI-NR subgroup, but it did differ from both the BSRO-RF and

‘0-l i

O’;‘16’ 25

Time (wks) Fig. 2. Trend in maximal interincisinal opening: sagittal split and LeFort I (RF).

BSRO/LFI-RF subgroups. The BSRO/LFI-NR subgroup showed the same results as the BSRO-NR subgroup.

DISCUSSION

All subgroups in this study showed a statistically significant reduction in MI0 postoperatively. The BSRO-RF and the BSRO/LFI-RF subgroups exhibited a 6.9% and 6.6% reduction in MIO, respec- tively. The MI0 reduction was at least four times greater for the nonrigid, nonrehabilitated group; the BSRO-NR and BSRO/LFI-NR groups had a MI0 reduction of 29.6% and 26.1% respectively. Time of follow-up was not a factor in that the mean follow-up time was less for the rigid fixation groups. MI0 reduction was not significantly correlated to the length of follow-up time beyond 6 months after surgery. With the present protocol, the rigid fixation group returned to close to preoperative MI0 levels by the end of 6 months. Figs. 1 and 2 depict the general trend for the return of normal MI0 during the first 6 months of follow-up in the rigid fixation group. Both curves show strong second-order poly- nomial relationships (Fig. 1, r = 0.948, F [2, 111 = 40.331, p < 0.0001; Fig. 2; nonrigid fixa- tion r = 0.972, F [2, lo] = 68.22, p < 0.0001). We do not have similar data for the nonrigid fixation group.

The nonrigid fixation group underwent MMF for approximately 6 weeks following surgery. In con- trast, the BSRO-RF and BSRO/LFI-RF subgroups averaged 1.9 and 4.6 days of MMF, respectively. The

Volume 63 Mandibular range of motion with rigid/nonrigid jixation 41 I Number 4

effects of immobilization on the temporomandibular joint and muscles have been studied.10-‘3 These effects include degenerative changes in the temporomandib- ular joint and atrophy of skeletal muscle. However, in experimental animals, muscular changes have been shown to be transient and reversible with the resumption of function.‘2 Similarly, the degenerative changes that follow immobilization of the temporo- mandibular joint may also be reversible.13 Surgical trauma to the mucosa, connective tissue, and mus- cles, together with immobilization and subsequent scarring, probably contributes to the decreased range of motion experienced postoperatively. Probably, wound healing during immobilization results in greater scar formation at the surgical sites in the nonrigid fixation group.

Early function may allow the wound healing to act in concert with function, thus enhancing the adaptive capacities of wound healing with the biologic requirements. Recent papers have used range of motion and dynamic exercises to enhance muscular rehabilitation following orthognathic surgery and release of MMF.4,5 While physiotherapy cannot be overemphasized in our rigid fixation groups, early function and mild physiotherapy gave promising results with respect to MIO.

While the preliminary results of this study are promising, one should be careful when directly com- paring the two groups. The study was not a simple comparison between rigid and nonrigid fixation and their effects on mandibular range of motion. There were several variables in each group. The groups varied not only in the method of fixation and duration of MMF but also in the use of physiothera- py. Rigid fixation allowed the rigid fixation group to undergo early mobilization and mild physiotherapy. However, this physiotherapy was not aggressive. Patients were instructed on the method, but the exercises were self-administered without the pres- ence of a therapist. Therefore, some patients were more enthusiastic about exercising than others. Sub- jectively, it appeared that those patients who exhib- ited a quicker return to near preoperative MI0 were those with greater compliance to physiotherapy. We believe that more aggressive postoperative physio- therapy may lead to an even more rapid return to preoperative MI0 levels.

In another study conducted at our institution, minimal rotation of the proximal segment was shown when rigid fixation was used.14 Previous articles noted marked counterclockwise rotation of the prox- imal segment when high-low wire osteosynthesis was employed.‘5-16 Certainly, some of the hypomobility seen in the nonrigid fixation groups may have been

secondary to muscular shortening with myoatrophy resulting from immobilization.

In conclusion, patients treated by rigid fixation with early function and mild physiotherapy showed significantly less reduction in MI0 than nonrehabil- itated patients with nonrigid fixation after mandibu- lar advancement with a BSRO.

REFERENCES

1. Storum KA, Bell WH: Hypomobility after maxillary and mandibular osteotomies. ORAL SURG ORAL MED ORAL PATHOL 57: 7-l 1, 1984.

2. Aragon SB, Van Sickels JE, Dolwick MF, Flanary CM: The effects of orthognathic surgery on mandibular range of motion. J Oral Maxillofac Surg 43: 938-943, 1985.

3. Ringqvist M: Isometric bite force and its relation to dimen- sions of the facial skeleton. Acta Odontol Stand 31: 35-42. 1973.

4. Bell WH. Gonyea W, Finn RA, Storum KA, Johnson C, Throckmorton G: Muscular rehabilitation after orthognathic surgery. ORAL SURG ORAL MED ORAL PATHOL 56: 229-235, 1983.

5. Storum KA, Bell WH: The effect of physical rehabilitation on mandibular function after ramus osteotomies. J Oral Maxil- lofac Surg 44: 94-99, 1986.

6. Jeter TS, Van Sickels JE, Dolwick MF: Modified techniques for internal fixation of sagittal ramus osteotomies. J Oral Maxillofac Surg 42: 270-272, 1984.

7. Van Sickels JE, Jeter TS, Aragon SB: Rigid fixation of maxillary osteotomies: a preliminary report and technique arti- cle. ORAL SURG ORAL MED ORAL PATHOL 60: 262-265, 1985.

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Van Sickels JE, Jeter TS: Rigid osseous fixation of osteotom- ies. In Bell WH (editor): Surgical correction of dentofacial deformities, new concepts, Philadelphia, 1985, W.B. Saun- ders Company. Epker BN: Modifications in the sagittal osteotomy of the mandible. J Oral Sure 35: 157-159. 1977. Glinburg RW, Lask; DM, Bloustein DI: The effects of immobilization on the primate temporomandibular joint: a histochemical study. J Oral Maxillofac Surg 40: 3-8, 1982. Lindboe CF, Platou CS: Disuse atrophy of human skeletal muscle: an enzyme histochemical study. Acta Neuropathol (Berl) 56: 241-244, 1982. Witzmann FA, Kim DH, Fitts RH: Recovery time course in contractile function of fast and slow skeletal muscle after hindlimb immobilization. J Appl Physiol 52: 677-682, 1982. Lydiatt DD, Davis LF: The effects of immobilization on the rabbit temporomandibular joint. J Oral Maxillofac Surg 43: 188193, 1985. Van Sickels JE, Larsen AJ, Thrash WJ: Relapse of rigidly fixated mandibular advancements: contributing factors. J Oral Maxillofac Surg (In press) Will LA, Joondeph DR, Hohl TH, West RA: Condylar position following mandibular advancement: its relationship to relapse. J Oral Maxillofac Surg 4t: 578-588, 1984. Singer RS, Bays RA: A comparison between superior and inferior border wiring techniques in sagittal split ramus osteotomy. J Oral Maxillofac Surg 43: 444-449, 1985.

Reprint requests to.

Dr. Joseph E. Van Sickels Department of Oral & Maxillofacial Surgery University of Texas Health Science Center

at San Antonio 7703 Floyd Curl Dr. San Antonio, TX 78284