A comparative study of stabitity

A comparative study of stabitity after mandibular advancement surgery Ekaterina Douma,* M. M. Kuftinec,** and Farhad M6shiri*** Louisville, Ky., and Athens, Greece.

The postsurgical stability of two groups of patients treated with different fixation techniques after mandibular advancement was evaluated retrospectively. Sixteen patients (group 1) underwent rigid osseous fixation, and another group of 16 patients (group 2) underwent intraosseous wiring fixation.

Our findings suggested that skeletal and dental changes occurred in both groups as a result of adaptation to the altered functional equilibrium. Relapse resulting in a percentage loss of the initial advancement occurred primarily 6 to 8 weeks postsurgically. No statistically significant difference was found to exist in,the short-term and long-term rates between the two groups. For the population studied, relative stability after mandibular advancement surgery was affected more by individual variability than by the fixation technique. (AM J ORTHODDENTOFACORTHOP1991 ;100:141-55.)

The application of combined surgicalorthodontic procedures for the treatment of major facial deformities and associated malocclusions has become an increasingly prevalent treatment modality over the past 2 decades. Development of sound conjoint treatment principles made possible the correction of skeletal and dental dysplasias that were unyielding to either surgical or orthodontic treatment alone? "2 The orthognatbic surgery option gives a clinician the ability to correct skeletal dysplasias in nongrowing patients, as well as to treat severe progressive deformities in adolescents and young adults. 3 Skeletal Class II malocclusions resulting from mandibular retrognathism often require a combined orthodontic-surgical approach for optimal function and best esthetic results. The sagittal split ramus osteotomy is currently one of the most favored surgical techniques for the management of mandibular retrognathism. 2 The technique has been successfully used by many clinicians over the years. Despite its popularity, however, one factor still remains a major concern in the surgical correction of mandibular retrognathism: its potential for relapse3 In fact, several investigations have shown that skeletal relapse is the most often encountered sequela of mandibular advancement surgery; it usually occurs early in the postsurgical period. *Former resident, now in practice in Athens, Greece. **Professor of Orthodontics, Director of Postgraduate Program, University of Louisville, Louisville, Ky. ***Clinical Professor of Orthodontics, University of Louisville, Louisville, Ky. 8/1/21619

Although skeletal relapse seems to be a multifactorial phenomenon, according to short-term and longterm follow-up of clinical cases, different.studies have suggested a link between certain etiologic factors. Positional change of the proximal segment was found to be the most important parameter in determining stability of the advanced mandible. According to recent studies,58 intraoperative distraction of the mandibular condyles from their functional position in the glenoid fossae results in a dramatic skeletal relapse immediately on release of intermaxillary fixation. The relapse occurs because a large discrepancy between the functional occlusal position and the terminal hinge position is created. Paramandibular connective tissue tension from the skin, interstitial connective tissue components, and enveloping periosteum have also been reported as etiologic factors in relapse. Recent reports indicate that the relapse seen after mandibular advancement surgery is a result of paramandibular connective tissue tension, lack of control of the proximal segment during surgery, condylar distraction, inadequate fixation periods, magnitude of advancement, t/nfavorable growth postsurgically, and preexisting internal derangement of the temporomandibular joints. 9'2 To minimize relapse, intraosseous fixation of the bone segments with stainless steel wires was used for a period of 6 to 8 weeks after surgery.

Histologic studies have shown that wiring of the proximal and distal segments provide semirigid fixation at best. 13~7 The patient with an osteotomy is at risk of relapse for as long as 25 weeks after surgery. In an effort to prevent intersegment movement and to promote primary bone healing, a technique for rigid approxi141

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Douma, Kttftinec, atzd Moshiri

Am. J. Orthod. Dentofac. Orthop.

August 1991

Po

(3

Or

G~

Me

Fig. 1. Hard tissue cephalometric landmarks used in study.

mation and fixation of the bony segments has evolved.

The objective was tO prevent a major source of relapse while simultaneously reducing the length of intermaxillary dental fixation. Rigid fixation after sagittal split osteotomy for mandibular advancement was accomplished by means of compression screws, usually inserted through a small skin incision at a 90 째 angle to the osteotomy site. z8-2~ Recent investigations of rigid fixation reported a good postsurgical stability, with a capability o f e a r l y masticatory function, improved nutrition, and a faster rate of recovery. When the relapse rates in intermaxillary and rigid fixation groups were compared, skeletal changes in the rigid fixation group were statistically smaller than those in the intermaxillary group. The relatively new technique was thus reported to be effective and stable. However, sufficient clinical documentation to support the theoretical concepts is not readily available.

The purpose o f this study was to investigate any significant differences between rigid and intraosseous wiring fixation techni~tues in patients treated with bi-

lateral sagittal split ramus osteotomy for mandibular advancement. Comparisons were to be made of any short-term and long-term skeletal and dental changes between the two groups.

METHOD AND MATERIALS

Two groups of 16 patients each who underwent mandibular advancement by means of bilateral sagittal split ramus osteotomy for correction of mandibular retrognathism were selected for this study. Patients who had any additional surgery (e.g., genioplasty or two jaw procedures) were not included in our sample. All the surgical procedures were performed by two "members of the same oral surgery group in an attempt to eliminate major technical differences. No maxillary surgical procedures were performed in any of the patients. The cephalograms were taken in norma lateralis, on the same cephalometers, so that magnification factors would remain constant, and reasonable comparisons could be made.22.23 Group 1 consisted of 14 females and 2 males with a mean age of 30.68 years (range, 14 to 50 years). Stabilization of the segments was achieved postsurgically by means of bone compression screws, which were consistently placed through

Stability after mandibular advancement surgery

Volume 100 Number 2

o \

143

1

UFH

:L

L~L

I

Fig. 2. Soft tissue landmarks and constructed parameters (after Moshiri F. J Clin Orthod 1982;16:3759): UFH, upper face height; NLA, nasolabial angle; ULL, upper lip length; LLL, lower lip length; FCA, facial contour angle.

Table I. P e r c e n t a g e s o f r e l a p s e

Group 1 (rigid fi.ration) Mean (SD)

Group 2 (wire firation) Mean (SD)

Group 1 to group 2

20.7 (21.6)

17.6 (20.2)

0.70 (NS)

10.1 (17.8)

6.1 (20.4)

0.62 (NS)

31.4 (30.4)

23.0 (31.5)

0.49 (NS)

t tests

Short-term relapse (Ar - PgT,) - (Ar - PgT0 *100 (Ar - PgT2) - (Ar - PgT0

Long-term relapse (Ar - PgT3) - (Ar - PgT4)*100 (Ar - PgT2) - (Ar - PgT0

Total relapse (Ar - PgT2) - (Ar - PgT4) *100 (Ar - PgTz) - (Ar - PgTO No'rE: For explanation of T, - T4, see Fig. 3.

an intraoral approach. Interdental fixation with an occlusal splint in place was u s e d for up to 2 weeks. 2' G r o u p 2 c o n s i s t e d o f 13 female and 3 male patients w h o also u n d e r w e n t m a n d i b u l a r a d v a n c e m e n t t h r o u g h bilateral sagittal split r a m u s o s t e o t o m y . In this group, inferior border

intraosseous wiring o f the b o n y s e g m e n t s was e m p l o y e d to a s s u r e stability a n d e n s u r e a g a i n s t m a j o r skeletal relapse. 2~ In addition, interdental fixation with an acrylic occlusal splint w a s routinely m a i n t a i n e d for a period o f 6 to 8 weeks.

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GROUP RIGID

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2.15 MOSII.071 1 4

T4 LONG-TERM

11.15 MOSI3.601 7 18

Fig. 3. A, Regimen of sampling and descriptive statistics for rigid fixation group.

Cephalometric analysis

RESULTS

Nine hard tissue anatomic landmarks (Fig. 1) and five soft tissue landmarks (Fig. 2) were located on each tracing.

Sixteen variables were selected to facilitate quantitative interpretation of customarily reported clinical parameters. 23'~27

Skeletal changes

Statistical analysis Statistical computations were made and analyzed with an SPSS package on an IBM 3081-D computer. Means and standard deviations were recorded for 16 variables, the change in each variable for both groups at four different times (TI, T2, T3, and 'I"4) as shown in Fig. 3. The significance of changes over the four points in time was determined by the Student t test for paired data. Spearman's rank order correlation coefficient (p) was used to test significant relationships between variables. Statistical significance was established at p = 0.05 and a correlation of r = 0.6 Was considered of clinical significance. Errors in landmark identification and digitizing were evaluated statistically, suggesting a linear error of approximately 0.02 mm and an angular error of 0.2".

Skeletal changes were demonstrable postsurgically in both groups. Short-term relapse was found to be comparable at 20.7% and 17.6% for group 1 and group 2, respectively. Similarly, a long-term relapse was 10.1% and 6.1% for the same respective groups.

A mean total relapse of 31.4% for group 1 and 23% for group 2 was Observed (Table I). Overall, changes expressed in inillimeter values were relatively small, measuring 1.4 m m and 1.8 mm for the two groups, respectively. Relapse rates were compared at all four time intervals by the Student t test, and differences were found to be statistically significant.

Magnitude of advancement Overall, the two groups had a similar amount of surgical advancement (5.6 mm and 7.0 mm, respectively). Associations between the magnitude o f ad-

Volume I00 Number 2

Stability after mandibular advancenzent s,+rgery GROUP

2

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22.85 MOS 111.091 12 46

Fig. 3. B, Regimen of sampling and descriptive statistics for intermaxi~lary fixation group.

Posterior facial height

vancement measured at pogonion and the total relapse were calculated for both groups by means of Pearson's correlation coefficient. Fig. 4 indicates a moderate association between the variables, indicating that as the magnitude of advancement increased, a tendency for postsurgical relapse was also likely to increase.

The surgical change in posterior facial height resulted in a slight net decrease in both groups. The mean long-term loss in posterior facial height was 0.9 mm for the rigid fixation group and 2.5 mm for the intermaxillary fixation group (Fig. 7).

Mandibular plane angle

Dental changes

A weak association was shown between mandibular plane angle and postsurgical relapse in group 1 and a moderate association in group 2 (Fig. 5). In both groups greater postsurgical skeletal relapse occurred in the high-angle cases than in the low-angle cases.

A slight posterior decompensatory movement of the maxillary incisors was achieved in preparation for surgery in both groups. The net long-term change was 0.7 째 and 2.6 째 for the two groups, respectively (Fig. 8). The pattern of dental decompensation for the mandibular incisors after surgery differed in the two groups, but some proclination of the mandibular incisors was seen in most of the patients in both of the groups (Fig. 9).

Although the occurrence of dental changes has been reported to compensate for postsurgical skeletal changes, such conclusions should be made with caution because of the large individual variability and also be-

Anterior facial height Both groups showed a demonstrable degree of anteroinferior surgical advancement of the distal segment, resulting in an increase in anterior facial height, which was sustained after surgery (Fig. 6). The differences between the groups showed no statistical significance.

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August 1991

SURGICAL ADVANCEMENT VS. RELAPSE Group i - R i g i d F i x a t i o n X

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Volume I00 Number 2

Stability after mandibular advancement surgery

147

HANDIBULAR PLANE ANGLE VS. RELAPSE Group I - Rtgld Flxatlan

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cause of the effect of orthodontic treatment on the dentition.

Soft tissue c h a n g e s

As expected, the facial profiles of all patients in both groups became less convex after the surgery. As

a result, facial contour angle was reduced an average of 5.6 ° and 7.2 ° for the two groups. The net result after retention was a decrease of 8.3 ° and 4.9 °, respectively, for the two groups (Fig. 10). The soft tissue response did not show any evidence of statistically significant difference between the two groups.

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Am. J. Orthod. Dentofac. Orthop.

Augztst 1991

ANTERIOR FACIAL HEIGHT C H A N G E S Group 1 - Rigid FlxuUon

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~,blume I00

Number 2

Stability after mandibular adrancenmnt surgery

POSTERIOR FACIAL HEIGHT I ยง

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149

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Domna, Kuftinec, and Moshiri

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MAXILLARY INCISOR ANGULATION Oroup

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Voh,me 100

Stabilit)" after mandibular advancement surgery

Number 2

INCISOR A N G U L A T I O N

MANDIBULAR

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Fig. 9. Changes in angulation of mandibular incisors for rigid fixation group (6,) and for intermaxillary fixation group (B).

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Dozmza, Kztftinec, and Moshiri

Am. J. Orzhod. Dentofac. Orthop.

August 1991

FACIAL C O N T O U R

ANGLE

CHANGES

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Fig. I0. Changes in facial contour angle for rigidfixationgroup (A) and for intermaxiHary fixationgroup (8).

Volume 100 Number 2

DISCUSSION

In patients treated surgically for mandibular retrognathism, several investigators documented relapse by composite serial cephalometric tracings. According to many studies, relapse rates varied from 10% to more than 75%, with an average relapse of about 30% of the surgical correction .7,28The greater percentage of relapse occurred in the early postsurgical period, corresponding to pur T2-T3 period. The reported patients usually underwent intraosseous wiring, plus intermaxillary fixation with a splint for a period of 6 to 8 weeks.

Recently, two studies gave reports on postsurgical stability in patients stabilized by means of cortical compression screws or bone plates (rigid fixation), zg-~째 These studies reported good'skeletal stability. When a group of patients with rigid skeletal fixation was compared with a group with intermaxillary fixation, the skeletal changes of.the former (rigid fixation) were reported to be smaller than those seen in the latter group. 3~ In this study skeletal relapse was found to be a frequent and yet unpredictable sequela of the surgical correction. The results indicated that the duration, extent, and direction of skeletal changes were unpredictable, with large individual variations in response to surgical treatment without an apparent close correlation with the severity of the original malocclusion.

Our results support many previous reports that have found skeletal instability to be an important factor in the majority of treated patients.Z8"32-35No significant difference in the relapse rates between the two groups was found in either the short-term or the long-term followup. Of significant and noteworthy magnitude is the total relapse measured at pogonion (31.4% for the rigid fixation group and 23% for the intermaxillary fixation group), which corresponds well with that reported in earlier studies. Comparisons of composite serial cephalometric tracings show that skeletal changes occurred for most patients during the first 4 to 8 weeks after surgery.

The surgical lengthening of the mandible in both groups was achieved primarily by an anteroinferior advancement of the distal mandibular segment. 36This resuited in an increase in the anterior facial height that was sustained postsurgicalty. Confirming previous studies, a surgical increase in anterior facial height occurred in almost all cases, and a modest net long-term gain was observed.

The posterior facial height was somewhat reduced postoperatively in both groups and remained decreased throughout fixation. Empirical clinical experience indicates that surgical increase in posterior vertical dimensions is unstable and correlates with relapse. 37,3s

Stability after mandibular advancement surgery

153

For this reason, results of our study are positive and indicative of less relapse than observed in earlier reporl~.

The preoperative mandibular plane angle as a single parameter of facial form is not a reliable predictor of tile amount of p0stsurgical relapse, z,39It has been speculated that some degree of relapse is observed because of the triangulation phenomenon. If and when this phenomenon occurs, the observed relapse should correlate highly with a decreased mandibular plane angle. That did not appear to be the case in this study. In our study, the rigid fixation group showed a weak association between the mandibular plane angle and the total relapse; the correlation between the two vhriables was slightly higher in the wire fixation group.

Although some investigators deny any association between preoperative mandibular plane angle and skeletal relapse, a number of studies found less relapse in patients with low mandibular plane angles? 째'z8 A suggested explanation, which is different from the described triangulation after surgery, is that the convergent skeletal pattern freqtiently was associated with a strong vertical component of masticatory muscle function in support of the new mandibular position, with the posteriorly directed tensor forces unable to effect a large change.

Changes in the maxillary and mandibular dentition seen postoperatively in all patients were greater than skeletal differences. Compensatory changes in the dentition are said to occur as the skeletal equilibrium is being reestablished. :째.3s In this sample, both the maxillary and the mandibular incisors showed an acceptable proclination, on average, at the time of fixation. However, wide individual variations were observed.

SUMMARY AND CONCLUSIONS

A sample of 32 patients with significant retrognathism was evaluated after mandibular advancement surgery. Sixteen patients were stabilized by means of bicortical bone screws (rigid fixation), and 16 patients had standardized intraosseous wiring of the bony segments. Analysis of longitudinal cephalometric measurements demonstrated skeletal and dental adaptations to the altered functional equilibrium. Multiple parameters were analyzed to determine factors contributing to postoperative changes and to compare the results between the two groups. Findings from this study can be summarized as follows: 1. Skeletal changes were seen after surgery in both groups, resulting in some loss of the initial mandibular advancement. The percentages of short-term and long-term relapse between the

154

Dottma, Kuftinec, and Moshiri

2.

3.

4.

5.

groups w e r e not found to be significantly different.

T h e m a g n i t u d e o f a d v a n c e m e n t was found to be a factor in postsurgical mandibular stability fn both groups. A s the m a g n i t u d e o f a d v a n c e m e n t increased, there was a tendency for the fiet a m o u n t o f relapse to increase.

A w e a k association b e t w e e n the preoperative m a n d i b u l a r plane angle and the total a m o u n t o f relapse was found in the rigid fixation group.

Patients with h i g h m a n d i b u l a r plane angles s e e m e d to s h o w m o r e relapse than patients with either normal or low angles.

Alterations o f the relationships b e t w e e n m a x illary and n~andibular s e g m e n t s o c c u r r e d postoperatively as a result o f adaptation to the functional e q u i l i b r i u m and orthodontic m e c h a n o therapy.

N o statistically significant differences b e t w e e n the rigid fixation and intermaxillary fixation groups w e r e found in the skeletal and dental changes o b s e r v e d at the f o u r time intervals studied.

We thank Dr. Kenneth Rotskoff of St. Louis, Missouri, for graciously allowing us to peruse his cases for this study.

REFERENCES 1. Kiyak HA, West RA, Hohl T, McNeil RW. The psychological impact of orth~nathic surgery: a nine-month follow-up. AM J ORTHOD 1982;81:404-12.

2. Obwegeser H. The indications for surgical correction of mandibular deformity by the sagittal splitting technique. Br J Oral Surg 1964;1:i57-66.

3. Dal Pont G. Retromolar osteotomy for the correction of prognathism. J Oral Surg 1961;26:249-52.

4. Kundert M, Hadjianghelou O. Condylar displacement after sagittal splitting of the mandibular rami. J Oral Maxillofac Surg 1980;8:278-97.

5. Booth DF. Control of the proximal segment by lower border wiring in the sagittal split osteotomy. J Oral Maxillofae Surg 1981;9:126-8.

6. Ellis E, Gallo WJ. Relapse following mandibular advancement with dental plus skeletal maxillomandibular fixation. J Oral Maxillofac Surg 1986;44:509-15.

7. Epker BN, Wessberg GA. Mechanisms of early skeletal relapse following surgical advancement of the mandible. Br J Oral Surg 1982;20:175-82.

8. Jeter TS, Van Sickels JE, Dolwick MF. Modified techniques for internal fixation of sagittal ramus osteotomies. J Oral Maxillofac Surg 1984;42:270-2.

9. Fish LC, Epker BN. Prevention of relapse in surgical-orthodontic treatment. Part I. Mandibular procedures. J Clin Orthod 1986; 20:826-41.

10. Kohn MW. Analysis of relapse after mandibular advancement surgery. J Oral Surg 1978;36:676-84. !1. Martis CS. Complications after mandibular sagittal split osteotomy. J Oral Maxillofac Surg 1987;42:101-7.

Am. J. Orthod. Dentofac. Orthop.

August 1991

12. Van Sickels JE, Flanary CM. Stability associated with mandibular advancement treatment by rigid osseous fixation. J Oral Maxillofac Surg 1985;43:338-41.

13. Ellis E, Carlson DS. Stability two years after mandibular advancement with and without suprahyoid myotomy: an experimental study. J Oral Maxillofac Surg 1983;41:426-37.

14. Gingrass DJ, Messer El. Rigid noncompressive pin fixation of the mandibular sagittal split osteotomy. J Oral Maxillofac Surg 1986;44:413-6.

15. Greebe FC, Tuinzing DB. Mandibular advancement procedures: predictable stability and relapse. Oral Surg Oral Med Oral Pathol 1984;57: ! 3-6.

16. Paulus GW, Steinhauser EW. A comparative study of wire osteosynthesis versus bone screws in the treatment of mandibular prognathism. Oral Surg Oral Med Oral Pathol 1982;54:2-6.

17. Reitzik M, Schoorl W. Bone repair in themandible: a histologie and biometric comparison between rigid and semi-rigid fixation.

J Oral Maxillofac Surg 1983;41:215-8.

18. Epker BN. Modifications in the sagittal osteotomy of the mandible. J Oral Surg 1977;35:157-9.

19. Epker BN, Wolford LM, Fish LC. Mandibular deficiency syndrome: surgical considerations for mandibular advancement.

Oral Surg Oral Med Oral Pathol 1978;45:349-63.

20. Thomas PM, Tucker MR, Prewin JR, Proffit WR. Early skeletal and dental changes following mandibular advancement and rigid internal fixation. Int J Adult Orthod Orth~n Surg 1986; 1:171-8.

21. Van Sickels JE, Larsen AJ, Thrash WJ. Relapse after rigid fixation of mandibular advancement, J Oral Maxillofac Surg 1986; 44:698-702.

22. lye J, McNeil RW, ",,VestRA. Mandibular advancement: skeletal and dental changes during fixation. J Oral Surg 1977;35:881-6.

23. Moshiri F. Orthognathie and craniofacial surgical diagnosis and treatment planning: a visual approach. J Clin Orthod 1982;16:3759.

24. Behrman SJ. Complications of sagittal osteotomy of the mandibular ramus. J Oral Surg 1972;30:554-61.

25. Lake SL, McNeil RW, Little RM, West RA. Surgical mandibular advancement: a cephalometric analysis of treatment response.

AM J ORTHOD1981;80:376-94.

26. Singer RS, Bays RA. A comparison between superior and inferior border wiring techniques in sagittal split ramus osteotomy.

J Oral Maxillofac Surg 1985;43:321-37.

27. White RP, Proffit WR, Crammer JR, Kohn MW. A study of facial height changes after mandibular osteotomy in 46 patients.

J Oral Surg 1971;29:858-61.

28. McDonnell JP, McNeil RW, \Vest RA. Advancement genioplasty: a retrospective cephalometric analysis of osseous and soft tissue changes. J Oral Surg 1977;35:640-7.

29. Reitzik M. Mandibular advancement surgery: stability following a modified fixation technique. J Oral Surg 1980;38:893-7.

30. Souyris F. Sagittal splitting and bicortical screw fixation of the ascending ramus. J Oral Maxillofac Surg 1978;6:198-203.

31. Schendel SA, Epker BN. Results after mandibular advancement surgery: an analysis of 87 cases. J Oral Surg 1980;38:265-82.

32. Fox GL, Tilson HB. Mandibular retrognathia: a review of literature and selected cases. J Oral Surg 1976;34:53-61.

33. Freihofer HP, Petresevic D. Late results after advancing the mandible by sagittal splitting of the rami. J Oral Maxillofac Surg 1975;3:250-7.

34. Guernsey LH. Stability of treatment results in Class II malocclusion corrected by full mandibular advancement surgery. J Oral Surg 1974;37:668-87.

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Stability after mandibular advancement surge D,

Number 2

35. Worms FW, Speidel TM, Bevis RR, Waite DE. Post-treatment stability and esthetics of orthognathic surgery. Angle Orthod 1980;50:251-73.

36. Stoelinga PJW, Leenen RJ. Class It anomalies: a coordinated approach to the management of skeletal, dental, and soft tissue problems. J Oral Surg 1981;39:827-41.

37. Poulton DR, Ware WH. Increase in mandibular and chin projection with orthognathic surgery. AM J ORrnOD 1985;87:36376.

38. Proffit WR, White RP. Treatment of severe malocclusions by correlated orthodontic-surgical procedures. Angle Orthod 1970; 40:1-10.

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39. McNeil RW, West RA. Severe mandibular retrognathism:orthodontic versus surgical orthodontic treatment. AMJ ORxrtoo 1977; 72:176-82.

Reprint requests to: Dr. M. M. Kuftinec Department of Growth and Special Care School of Dentistry University of Louisville Louisville, KY 40292

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