Intraosseous wiring in ramus osteotomy

J Oral Maxillofac Surg 41:789-794,1983

Intraosseous Wiring in Ramus Osteotomy PER ASTRAND, DDS, PHD, OLaF ECKERDAL, DDS, PHD, AND GORAN SUND, DDS The value of intraosseous wiring of the fragments after oblique osteotomy of the mandibular rami was studied. A wired group (14 patients) and a nonwired group (15 patients) were compared cephalometrically. There were only small differences between the groups but there was a tendency toward a smaller postoperative posterior rotation of the mandible in the wired group. It was concluded that in routine cases of mandibular prognathism wiring is not necessary.

Some preoperative cephalometric characteristics of the patients' are shown in Table 2 (see Fig. 1 for a diagram of the reference points and lines used) . The osteotomies were performed by an extraoral technique described in an earlier paper.f After repositioning of the mandible, the proximal fragment was always pressed upward into the fossa. In the wired group, a hole was drilled through the anterior fragment (Fig 2). A groove was made on the posterior border of the proximal fragment at the same level as the hole or just beneath it. A O.4-mm stainless steel wire was passed through the hole and tightencd around the proximal fragment. The patients were placed in maxillomandibular fixation with wires. In six cases orthodontic appliances or arch bars were used in combination with an interocclusal splint. In all other cases capsplints with an occlusal index were used. No skeletal fixation was used. The patients were followed with clinical and radiographic examinations at the following intervals:

The oblique osteotomy of the mandibular rami is widely used for the correction of mandibular prognathism. Some authors l - 5 have proposed the use of an intraosseous wire for control of the relationship between the fragments following this procedure , while others'
Twenty-nine patients were included in the study. They comprised all patients treated for mandibular prognathism with a bilateral oblique osteotomy between September 1977 and October 1979 at the Maxillofacial Unit, Oral Surgery Department, University of Urnea. No other surgical procedures were performed in these patients. They were randomly divided into two groups; one group received intraosseous wiring (w-group; II = 14) and one did not (nw-group; II = 15). The age and sex distribution of the patient population is shown in Table 1.

1. Preoperatively 2. One to three days after surgery 3a. Seven to eight weeks after surgery (with maxiIlomandibular fixation still in place) 3b. Seven to eight weeks after surgery (maxillomandibular fixation removed and preliminary occlusal adjustment performed) 4. Six months after surgery 5. Eighteen months after surgery

The only exception to this schedule was that three patients (two patients from the w-group and one patient from the nw-group) were not radiographed seven to eight weeks after the operation with fixation still in place (3a). The postoperative positional changes of the man-

Rece ived from the Dep artments of Oral Surgery and Oral Roentgenology, University of Urnea, Urnea, Sweden, and the Department of Oral Roentgenology, The Institute for Postgrad uate Dental Education, Jonkoping, Sweden . Address correspondence and reprint reque sts to Dr. Astrand: Dep artment of Oral Surgery, Univ ersity of Umea, S-901 87 Umea, Sweden.

789

790

WIRING OF RAMUS OSTEOTOMY

Table 1. Age and Sex Distribution of Osteotomy Patient Population with and without Postoperative Intraosseous Wiring Males Wired

Age 16-20 years 21-25 years 26-30 years 31-35 years 36-40 years >40 years Total

Females

Total

Not Wired

Wired

Not Wired

0 4 2

4

2 3

5

I

2

I

2

2 3 2

8

14

3

Wired

7

dible were evaluated on lateral cephalograms using the reference points and lines described in Figure 1. 11 The measurements were performed using a computer-aided analysis systern.P In every cephalogram, 81 anatomic points were identified and recorded using a Hewlett Packard 9847 A Digitizere. The coordinates of these points were transferred to a Hewlett Packard 9845 A ® computer, where angles and distances were calculated. The changes between the different examination periods and the differences between the w-group and the nw-group were tested with Student's t-test. Results CLINICAL OBSERVATIONS

The use of intraosseous wiring caused a slight increase in operation time but did not cause any surgical problems. 'Postoperatively, one of the 14 wired patients complained of discomfort in one of the wired areas. This discomfort disappeared within a few weeks. There were no other clinical disadvantages of the wiring and in no case was there an indication to remove the wire. At the follow-up examinations, attention was directed toward symptoms of the temporomandibular joints. Tenderness of the masticatory muscles was found in three patients (two patients in the w-group and one patient in the nw-group) during the earlier examinations but had disappeared in all three by the 18-month examination after adjustments of occlusion. Clicking from the temporomandibular joints was still present in two patients from the wgroup at the final examination. Two patients who before surgery had had mandibular dysfunction symptoms were relieved of their symptoms after the operation.

7

2 7 2 2 2

I I

I

7

Not Wired

15

Results POSITIONAL CHANGES OF THE MANDIBLE OBSERVED IN THE CEPHALOGRAMS

Period of maxillomandibular fixation (2-3a) The gnathion moved in a posterior and inferior direction in relation to the SN-line (Table 3, Fig. 3). The mean positional changes of the x-coordinate of the gnathion were 2.4 mm in the w-group and 4.2 mm in the nw-group. The positional change of the x coordinate was significantly greater in the nwgroup, while there was no significant differences between the groups with regard to the y coordinate. The angle SNB, which had decreased at surgery for both groups, (mean decrease of w-group, 5.9 degrees; mean decrease of nw-group, 6.3 degrees) Table 2. Preoperative Cephalometric Characteristics of 29 Osteotomy Patients Wired (n = 14)

Not Wired (n = 15)

X

SD

X

SD

SNA

79.4

3.7

8\.9

4.3

SNB

85.3

3.8

88.1

5.4

SNPg

87.0

3.9

89.2

5.3

SNBa

129.0

4.0

129.1

7.3

ML-SN

3 \.4

4.5

29.9

5.8

RL-ML

13".1

6.2

130.5

6.8

I-SN

102.2

7.8

106.8

7.3

I-ML

75.8

6.9

76.1

7.9

2.2

2.1

2.0

2.5

-5.1

3.1

-6.02

4.6

Overbite Overjet

791

ASTRAND AND SUND

continued to decrease during the fixation period by another 0.5 degrees in the w-group and 1.2 degrees in the nw-group (Table 3). The decrease was significantly greater in the nw-group (P < 0.01). The angle ML-SN increased during the fixation period in both groups (P < 0.001) Table 3). The mean increases were 3.9 degrees in the w-group and 5.2 degrees in the nw-group. The difference between the groups was not statistically significant (P = 0.057). Posterior facial height (Go-SN) decreased during the fixation period (Table 3). The mean decreases were 2.6 mm in the w-group (P < 0.01) and 3.8 mm in the nw-group (P < 0.001). The difference between the groups was not statistically significant. Release of Fixation to Six Months (3b-4) Between examination periods 3b when fixation was released and 4, a horizontal relapse occurred in both groups, with a forward movement of the gnathion at a mean increase of 1.2 mm in the wgroup and 2.1 mm in the nw-group (Table 3). There was no significant difference between the groups. The gnathion moved upward in the vertical direction during the same period. This movement was slightly greater in the nw-group. The angle SNB had increased slightly between the end of the fixation period and the six-month

x __--+f---t'--~:---T----r~SN

FIGURE 2.

Illustration of intraosseous wiring procedure. A

OA-mm stainless steel wire was passed through a hole in the

distal fragment and tightened around the proximal fragment.

examination (Table 3). There was no significant difference between the groups with regard to this variable. The angle ML-SN had increased in both groups by examination 3b compared with preoperative measurements, with mean increases of 2.7 degrees in the w-group and 4.1 degrees in the my-group. The difference between the groups was not significant. However, no further change in angle occurred between examinations 3b and 4 (Table 3). Posterior facial height (Go-SN) had decreased in both groups by examination 3b compared with the preoperative values, with a mean decrease of 4.1 mm in the w-group and of 4.0 mm in the nw-group. Between examinations 3b and 4 no significant change in the posterior facial height took place in either group (Table 3). Eighteen months (5) Only small positional changes of the mandible occurred during this period (Table 3). A slight further relapse occurred but no differences between the groups were seen. POSITIONAL CHANGES OF THE ANTERIOR TEETH OBSERVED IN THE CEPHALOGRAMS

y

FIGURE I. Reference points and lines used in the cephalometric evaluation.

The upper incisor inclination (I-SN) decreased at surgery from preoperative values; the differences by examination 3b were 2.3 degrees in the w-group and 4.4 degrees in the my-group (Table 3). The difference between the groups was significant. During

792

WIRING OF RAMUS OSTEOTOMY

Table 3. Observed Changes of the Position of the Mandible of Osteotomy Patients with (n and without (n = 15) Intraosseus Wiring'" Not Wired

Wired Mean

Level

Mean Difference from Baseline Values

4.1 mm 1.5 mm 1.4 mm 1.4 mm 1.7 mm

P < 0.001 P < 0.001 P< 0.01 ns P < 0.001

-12.1 mm -4.2 mm 2.1 mm 1.0 mm 3.1 mm

1.4 mm -l.lmm 0.5 mm -0.7 mm -0.1 mm

1.9 mm 1.5mm 0.8 mm 1.1 mm 0.3 mm

P P P P

Difference from Baseline Values

x coordinate of gnathiont Examinations 1-2 - 10.4 mm -2.4 mm Examinations 2-3a Examinations 3b-4 1.2 mm 0.4 mm Examinations 4-5 2.0mm Examinations 3b-5

= 14)

Significance

SD

Significance Level

SD

< 0.001 < 0.001

Difference Between Groups

4.7mm 1.7 mm 2.1 mm 1.6 mm 1.8 mm

P P P P P

<0.01 < 0.05 < 0.001

(ns) -1.7 (P < 0.01) (ns) (ns) (ns)

2.7mm 1.7 mm 1.3 mm 1.1 mm 2.0mm

ns P < 0.01 P < 0.001 ns P < 0.05

(ns) (ns) -0.9 (P < 0.05) (ns) - \.2 (P < 0.05)

2.10

P < 0.001 P < 0.001 P < 0.05 ns

(ns) 0.7 (P < 0.0l) (ns) (ns)

y coordinate of gnathion

Examinations 1-2 Examinations 2-3a Examinations 3b-4 Examinations 4-5 Examinations 3b-5

< < < <

0.05 0.05 0.05 0.05 ns

0.4 - \.7 1.5 -0.2 \.3

SNB Examinations Examinations Examinations Examinations

1-2 2-3a 3b-4 4-5

-5.9 0 -0.5 0 0.6° 0.3 0

1.50 O.SO 0.5° 0.50

P< P< P< P<

0.001 0.01 0.001 0.05

-6.3 0 -1.2 0 0.8 0 0.4 0

ML-SN Examinations Examinations Examinations Examinations

1-2 2-3a 3b-4 4-5

-0.3 0 3.9 0 0.4 0 -0.5 0

2.90 IS 1.20 1.00

ns P < 0.001 ns ns

-0.4 0 5.2 0 -0.6° -0.4 0

Go-SN Examinations Examinations Examinations Examinations

1-2 2-3a 3b-4 4-5

-1.1 mm -2.6 mm -0.9 mm 1.5 mm

2.8mm 2.2 mm 1.3 mm 1.0 mm

ns P< 0.01 P < 0.05 P < 0.001

-2.3°

2.7 0

o.r

0

mm mm mm mm mm

o.r 1.1° 0.8 0

o.r

ns P < 0.001 ns P < 0.05

(ns) (ns) (ns) (ns)

-0.02 mm -3.8 mm -1.0 mm 0.6mm

3.2mm 1.7 mm 1.8 mm 1.7 mm

ns P < 0.001 ns ns

(ns) (ns) (ns) (ns)

0.1 0

1.4 1.40

P< 0.01 ns ns

-4.4 0 3.0 0 1.10

2.10 3S 2.90

P < 0.001 P < 0.01 ns

I-ML Examinations 1-3b Examinations 3b-4 Examinations 4-5

-2.80 1.10 0.6°

2.8 0 3S 2.1°

P < 0.01 ns ns

-1.0 0 0.6 0 1.3°

4.5 0 2.10 1.8°

ns ns P < 0.05

ii-ML Examinations 1-3b Examinations 3b-4 Examinations 4-5

0.7 mm -0.2 mm -0.03 mm

0.8 mm 0.5 mm

P < 0.01 ns ns

1.5 mm -0.8 mm -0.02 mm

0.9mm 0.7mm 0.5 mm

P < 0.001 P < 0.001 ns

I-SN Examinations 1-3b Examinations 3b-4 Examinations 4-5

3.00 1.80 1.50

2.1 (P < 0.05) -2.7 (P < 0.05) (ns) (ns) (ns) (ns) -0.8 (P < 0.05) 0.6 (P < 0.05) (ns)

* See Fig. I for a diagram of the reference points and lines used. Negative values of the y-coordinate equal inferior movement. t The x axis is parallel with the SN line. the period from examination 3b to examination 4 a proclination occurred that was greater in the nwgroup than in the w-group. The lower incisor inclination (I-ML) also decreased between the preoperative examination and examination 3b (Table 3). No difference between the groups was demonstrated. The distance ii-Ml, increased in both groups initially (from examination I to 3b), indicating an extrusion of the incisors

(Table 3). The extrusion was significantly greater in the nw-group. Between examinations 3b and 4 there was a slight intrusion, which was also greater in the nw-group,

Discussion

The patients in this study were, as previously mentioned, randomly distributed into the wired and

793

ASTRAND AND SUND

nonwired groups. Preoperative cephalometric variables were compared (Table 2). No significant differences were found between the groups in t-tests of the group means and F-tests of the variances. A retrospective comparison between the groups with regard to the surgical setback of the mandible (Table 3; examinations 1-2) indicated a slightly greater mean setback in the nw-group than in the w-group. Statistical analyses of this difference, as well as of the preoperatively calculated surgical movements, demonstrated no statistically significant difference between the groups. On the basis of these analyses it seems warranted to make comparisons between the groups. From earlier studies 11 we know that certain positional changes of the mandible regularly take place after oblique osteotomy of the rami. During the fixation period there is a posterior rotation of the mandible with a decrease in posterior facial height. This movement is usually accompanied by decreases in the incisor inclination and extrusion of the lower incisors. 11 If the wiring has a stabilizing effect on the relationship between the fragments, the posterior rotation should be smaller in the wgroup than in the nw-group and such a difference oughtto affect the variables SNB, ML-SN, Go-SN, I-SN, I-ML, ii-ML, and the coordinates of the gnathion during the fixation period (examinations 2 and 3a). In comparing the two patient groups, the mean values for seven of these eight variables lent support to the hypothesis that wiring may decrease the posterior rotation of the mandible. Statistical analysis demonstrated significant differences between the groups with regard to four of these variables (SNB, I-SN, ii-ML, and the x coordinate of gnathion) while the differences in the remaining four variables were not significant. From this it seems probable that the wiring may contribute to a less pronounced posterior rotation of the mandible. This result is in agreement with the statement of Robinson that wiring of the fragments should be of special value in cases where a lengthening of the ramus is intended. A subgrouping of the patients in this study to assess the effect of the wiring in such patients, however, gave groups that were too small for statistical analysis. The wiring did not seem to have any positive or negative effect on relapse after the fixation period. This result contradicts the statement by Isaacson et al. 13 that the use of intraosseous wiring should cause a greater relapse. There may be several reasons for the difference between our results. One explanation is that Isaacson et al. included several types of ramus osteotomies in their study, and they did not randomize the use of wiring in their patient population. For these reasons, the greater relapse

4

~

3a

3a

FIG URE 3. Illustration of the means of the x and y coordinates for the gnathion at the different examination periods for the two patient groups. Top, w-group; bottom, nw-group. The axes indicate millimeters.

they report may very well have been due to factors other than the wiring per se. Reports of symptoms of the temporomandibular joints or masticatory muscles by patients were rare, and in the two cases of clicking of the joints, the discomfort to the patients was of no clinical consequence. The fact that these two patients belonged to the wired group does not permit conclusions to be made about whether wiring of the fragments has a greater impact on the temporomandibular joints than an osteotomy without wiring. Possible influence of the wiring on the temporomandibular joint will therefore be studied separately. Conclusions

It is concluded that with regard to postoperative stability of the mandible, no advantages of wiring could be demonstrated. There were however, no disadvantages either. This indicates that if wiring is desirable to obtain an optimal relationship between fragments at operation, there is no contraindication to it. References I. Hall DH, Chase DC, Payor LG: Evaluation and refinement of the intraoral vertical subcondylar osteotomy. J Oral Surg 33:333, 1975 2. Rankow RM, Di Salvo N, Potter G: End results of the lateral oblique osteotomy for mandibular prognathism. III Schuchardt K, Stell mack R: Ortopadische chirurgie im KieferGesichts-Bereich, Georg Thieme Verlag, Stuttgardt 1974, p 155 3. Shira RB: Surgical correction of open bite deformities by oblique sliding osteotomy. J Oral Surg 19:275, 1961 4. Thoma KH: Oblique osteotomy of the mandibular ramus. Oral Surg 14:23, 1961

794 5. Egyedi P, Houwing M. Juten E: The oblique subcondylar osteotomy: report of results of 100 cases. J Oral Surg 39:871,1981 6. Hinds EC: Correction of prognathism by subcondylar osteotomy. J Oral Surg 16:209, 1958 7. Nordenram A, Waller A: Oral-surgical correction of mandibular protrusion. Br J Oral Surg 6:64, 1968 8. Astrand P, Bergljung L, Nord PG: Oblique sliding osteotomy of the mandibular rami in 55 patients with mandibular prognathism. Int J Oral Surg 2:89, 1973 9. Johanyson B. Kahnberg K-E. Lilja J. et al: Surgical correction of mandibular prognathism by the oblique sliding osteotomy. Scand J Plast Recon str Surg 13:453, 1979

WIRING OF RAMUS OSTEOTOMY

10. Robinson M: Osteotomy of the Mandibular Ramus. Springfield, III.• Charles C Thomas, 1977 II . Astrand P, Ridell A: Position al change s of the mandible and upper and lower anterior teeth after oblique sliding osteotomy of the mandibular rami-a roentgenocephalometric study of 55 patients. Scand J Plast Reconstr Surg 7:120,1973 12. Persson G, Lindholm B, Astr and P: Kirurgisk korrigering av kakanomalier. VII: Cephalometri och datorteknik. Tandlak tidn 73:1315, 1981 13. Isaacson RJ, Kopytov OS. Bevis RR, et al: Movement of the proximal and di stal segments after mand ibular ramus osteotomies. J Oral Surg 36:263, 1978