J Oral Maxillofac 49.12931296,
Surg
1991
A Comparative Study of Bicortical Screws and Suspension Wires Versus Bicortical Screws in Large Mandibular Advancements JOSEPH E. VAN SICKELS,
DDS*
Relapse with large mandibular advancements treated by bicortical position screws has been documented in the literature. This study compares stability seen with two groups of patients; one treated with bicortical position screws and allowed to function, the second treated with bicortical position screws, skeletal wires, and 1 week of maxillomandibular fixation. Both groups had large advancements. The screw group was advanced an average of 10.9 mm, whereas the screw and wire group was advanced 12.2 mm. The screw group relapsed an average of 2 mm in the first 6 weeks, with further relapse occurring after that point. In contrast, the screw and wire group relapsed an average of 0.6 mm in the first 6 weeks, followed by a small advancement in the long term. Differences between the two groups were significant in the first 6 weeks and from the initial postoperative period to the long-term examination point. While stability was markedly improved with up to 13 mm of advancement in the group with screws and wires, relapse was noted after that amount of advancement. Methods to keep larger advancements stable are reviewed.
ear movement at the osteotomy site.‘0-‘4 Both clinical and animal studies have shown that relapse with wire osteosynthesis can be prevented or minimized with skeletal suspension wires and a 6- to S-week period of maxillomandibular fixation (MMF). 14-” Knowing that relapse occurs with large advancements treated with bicortical screws, based on the previous studies,14“7 it seems reasonable to assume that such relapse may be prevented with skeletal fixation and a period of MMF. The purpose of this article is to compare stability seen in two groups of patients with large advancements treated with bicortical screws. One group was treated with three bicortical screws per side and was allowed to function immediately after surgery. The second also had skeletal wires used and was placed in MMF for approximately 1 week.
Rigid fixation with bicortical screws after a bilateral sagittal ramus osteotomy with mandibular advancement has been well established in the literature.le3 Early reports noted excellent stability with little or no relapse4+ however, with larger advancements, relapse has been noted to occur.437,8 In a recent article, a segment of patients treated with bicortical screws had 25% or greater relapse; the majority of relapse was noted to occur at the osteotomy site in the first 6 weeks.’ Studies evaluating relapse with large advancements treated by wire osteosynthesis have likewise noted relapse to occur early, with rotatory and lin* Professor, Director of Dentofacial Deformities Clinic, Department of Oral and Maxillofacial Surgery, University of Texas Health Science Center, San Antonio. Address correspondence and reprint requests to Dr Van Sickels: Department of Oral and Maxillofacial Surgery, The University of Texas Health Science Center. 7703 Floyd Curl Dr, San Antonio, TX 78284-7908. 0 1991 American
Association
of Oral and Maxillofacial
Materials and Methods
Sur-
The cephalometric records of mandibular advancement patients treated by a bilateral sagittal
geons 0278-2391/91/4912-0006$3.00/O
1293
1294
COMPARISON OF SUSPENSION
ramus osteotomy by one surgeon at the University of Texas Health Science Center at San Antonio were retrospectively reviewed. Preoperative cephalometric tracings were made and compared with an initial corrected postoperative film. The latter film was corrected for splint thickness by superimposing a template on the mandible and rotating it on condylion until the teeth touched. The Sella-Nasion line was traced. A horizontal reference line from SN was likewise traced (HP). From HP a vertical reference line was drawn. The amount of advancement at the chin point (pogonion) was then measured. Advancements of less than 7 mm were not included. All advancements of 7 mm or greater were evaluated. Two groups were generated. One group had three 2 mm bicortical position screws placed at the osteotomy sites. They were allowed to function with splints in place, with three box elastics allowing immediate function. The elastics were placed bilaterally in the premolar-molar region and anteriorly in the central incisor region. These training elastics were generally used for 2 to 3 weeks. A second group of patients had three 2-mm bicortical position screws placed at the osteotomy site, skeletal suspension, and approximately 1 week of MMR. Splints were also used in this group. Skeletal suspension consisted of a 24-gauge wire placed bilaterally at the piriform fossa tied to the splint and two circumferential mandibular wires tied over the orthodontic arch wire bilaterally in the premolar region. Maxillomandibular fixation was applied by tying a 24 gauge wire from the splint in the region of the maxillary skeletal suspension wires to the circumferential mandibular wires. This was left for about 1 week. Training elastics were used following removal of fixation for about 2 weeks. Splints were removed in both groups at 2 weeks. Cephalometric radiographs were available for both groups preoperatively (Tl), initial postoperative (T2), 6 weeks postoperative (T3), and long-term postoperative (T4) (a minimum of 6 months). T4 in the no wire group ranged from 6 months to 4 years Table 1.
WIRES AND SCREWS VS SCREWS
(2.1 year average). T4 in the wire group ranged from 6 months to 6 years (1.6 year average). Once the radiographs were traced, they were superimposed for a best fit on anterior and posterior cranial base landmarks. Pogonion was chosen on each successive radiograph by superimposing on the chin point from the Tl radiographic tracing. All radiographs were then digitized and linear measurements were calculated using Dentofacial Planner Software (Toronto, Canada). Unpaired t tests were used to compare the amount of movement seen at the different time intervals (Tl-T2, T2-T3, T3-T4, T2-T4) between the two groups. In addition, movement within groups during the time intervals of T2-T3, T3-T4, and T2-T4 were compared against zero change using paired t tests. Results Eleven patients were advanced 10.9 + 3 mm (range, 6.6 to 15.5 mm) in the group fixed by position screws and allowed to function immediately. Of these, 6 had advancement genioplasties, and 5 did not. Fifteen patients were advanced 12.2 * 4 mm (range, 6.8 to 23.9 mm) in the group fixed by position screws and kept in fixation an average of 6 days. Twelve of these patients had advancement genioplasties, and 3 did not. There was no significant difference between the amount of advancement in the two groups (P < .39) (Table 1). Amount of relapse in the screw group in the first 6 weeks (T2-T3) was significant 2.0 ‘- 1.7, (P < .003) with further relapse occurring long term (Fig 1). The amount seen in the time interval T2-T3 in the group fixed with screws and stabilizing suspension wires was not significant 0.6 -+ 1.5, (P < .16) followed by a small advancement (Fig 2). The difference between the two groups was significant at P < .05 at both T2-T3 and T2-T4, but not at the T3-T4 time interval. Scattergrams of the two groups (Fig 3) show how the individual patients performed.
Comparative Results, Large Advancements Wires (n = 15)
No Wire (n = 11) Change
Mean(mm)
Preoperative to initial postoperative Initial postoperative to 6 weeks postoperative Initial postoperative to long-term postoperative 6 Weeks postoperative to long-term postoperative
10.9
SD(mm)
Rang-e Change(mm)
P
3.0
6.6 to 15.5
.oool
-2.0
1.7
-5 to 1.1
.003
-3.7
2.9
-8.6 to 2.2
.004
-1.6
2.9
-8.3 to 1.1
.159
Mean (mm)
12.2
SD(mm)
Range Change(mm)
P
Wire vs No Wire P Value
4.0
6.8 to 23.9
.OOOl
.39
-0.6
1.5
-3.2 to 2.1
.162
.032
-0.5
2.4
-6.5 to 2.6
.405
.006
1.7
- 3.9 to 2.3
.824
.067
0.1
1295
JOSEPH E. VAN SICKELS
1210-
a64E 20 -2-4-10,
-6-1 No Wires (Ti-T2)
No Wires (T2-T3)
No Wires (T3-T4)
No Wires (T2-T4)
(
(
,
10 15 No Wires (Tl-T2) (mm)
B5
20
FIGURE 1. Movement seen and standard error in the different time intervals with the group of patients treated with three bicortical screws alone.
Discussion This was not a prospective randomly designed study, as the patients included were treated over slightly different time intervals. The group of patients treated by screws alone were managed earlier in the experience of the author. While the two groups broadly overlap, as more experience was gained with rigid fixation the need for an auxiliary technique to manage large advancements was noted. Hence, around 1987 to 1988, advancements of the mandible larger than 6 to 7 mm were treated with three bicortical screws, suspension wires, and approximately 1 week of MMF. Nonetheless, there are many points that can be gleaned from these data. Perusal of the scattergram for the group with just bicortical screws (Fig 3A) shows that at about 6 ‘41 12lo-
a: 642O-2J Wire (Tl -T2)
Wires (T2-T3)
Wires (T3-T4)
Wires (T2-T4)
FIGURE 2. Movement seen and standard error in the different time interval with the group of patients treated with three bicortical screws, suspension wires, and approximately 1 week of MMF.
lo
Wires (TitT2) (mm)
2o
25
FIGURE 3. A, Scattergram for position screw only (no wire) group. Initial advancement on x axis, long-term advancement result only. B, Scattergram for position screw suspension and MMF group (wire). x and y axis the same.
to 7 mm, the patients showed relapse when the initial advancement was compared with the long-term position at pogonion. This was similar to the previous reports from this institution.798 In contrast, the second group did much better, not showing relapse until 13 to 14 mm of initial advancement (Fig 3B). What is worrisome in comparing Figures 1 and 2 is that the group with immediate function showed further instability after 6 weeks, in contrast to the fixation and skeletal wire group, which did not. Where the late relapse occurred is speculative. While instability at the osteotomy site has been shown to account for early relapse,’ long-term instability is thought to be secondary to condylar resorption and/ or remodeling. 18,19 Although magnitude of advancement is an important factor in relapse, many other causes have been suggested. These include technical factors, high angle cases, condylar resorption, condylar distraction, proximal segment control, and density of bone.9“4*18-20A review of both scatter-grams shows
1296
COMPARISON OF SUSPENSION
that individual patients did not follow the same pattern. This suggests that other factors played a role in the results seen in both groups. It is interesting that in the group with suspension wires and MMF there is a closer clustering of the patients. Perhaps suspension wires and MMF negate more than one of the factors involved in relapse. The primary question asked in this study was answered in that use of skeletal wires combined with MMF gives better stability than use of position screws alone. Although relapse may have multiple causes, large advancements, with their concomitant stretch on the surrounding soft tissue of the mandible, require that the neuromuscular apparatus adapt to the new position. Reynolds et al” showed that with large advancement, major adaptations occur at the muscle-bone and muscle-tendon interfaces and within the belly of the anterior digastric muscle. Furthermore, they showed that these changes occur early, within the first few weeks. Our patients who had position screws and skeletal wires placed with MMF showed greater short- and long-term stability when advanced up to 13 mm. This suggests that these auxiliary procedures are helpful in allowing the neuromuscular apparatus to adapt to change in mandibular position. However, even in this group, the amount of advancement eventually put too much tension on the system and relapse was seen. Two questions remain: 1) What can be done for cases with very large advancements?, and 2) Which auxiliary technique is important in preventing relapse, MMF or skeletal wires? The answer to the first question is related to the second. Larger screws, plates, and overadvancements are all possible ways to solve the problem. An increased period of MMF may also help; however, one must weight the disadvantages of MMF in the presence of rigid fixation.*“** Although skeletal wires in the pattern used have been shown to be effective, an alternative pattern of three wires may be more effective.23 The answer to the second question is speculative. Maxillomandibular fixation alone has not been shown to prevent relapse with wire osteosynthesis.10-12,14-17 However, there are no studies showing what happens to stability when screws are combined with MMF. Nitzan and Dolwick2’ believed that 6 to 8 weeks of MMF should not be used with rigid fixation, and reported on five cases with joint fibrous following this therapy. A lesser period of time, however, may not be detrimental. Skeletal wires, in contrast, have been shown to be very effective when combined with MMF.13-” Whether they would be equally effective if used with elastic traction is unknown. Ideally, each of the questions should be answered in a prospective study.
WIRES AND SCREWS VS SCREWS
References 1. Spiessl B: The sagittal splitting osteotomy for correction of mandibular nronnathism. Clin Plast Sum 9:491. 1982 2. Jeter TS, Van Sickels JE, Dolwick MF: Modified techniques for internal fixation of sagittal ramus osteotomies. J Oral Maxillofac Surg 42:270, 1984 3. Niederdellmann H, Shetty V, Collins FJV: Controlled osteosynthesis utilizing the position screw. Int J Adult Orthod Orthognath Surg 2:159, 1987 4. Thomas PM, Tucker MR, Prewitt JR, et al: Early skeletal and dental changes following mandibular advancement and rigid internal fixation. Int J Adult Orthod Orthognath Surg 1:171, 1986 5. Van Sickels JE, Flanary CM: Stability associated with mandibular advancement treated by rigid osseous fixation. J Oral Maxillofac Surg 43:338, 1985 6. Kirkpatrick TB, Woods, MG, Swift JQ, et al: Skeletal stability following mandibular advancement and rigid tixation: J Oral Maxillofac Surg 45572, 1987 7. Van Sickels JE. Larsen AJ. Thrash WJ: Relanse of rieidlv fixated mandibular advancements: Contributing fact&. J Oral Maxillofac Surg 44:698, 1986 8. Van Sickels JE, Larsen AJ, Thrash WJ: Retrospective study of relapse in rigidly fixated sagittal split osteotomies: Contributing factors. Am J Orthod Dentofacial Orthop 93:413, 1988 9. Gassmann CS, Van Sickels JE, Thrash WJ: Causes, location and timing of relapse following rigid fixation after mandibular advancement. J Oral Maxillofac Surg 48:450, 1990 10. Lake SL, McNeil RW, Little RM, et al: Surgical mandibular advancement: A cephalometric analysis of treatment response. Am J Orthod 80~376, 1981 11. Will LA, Joondeph DR, Hohl TH, et al: Condylar position following mandibular advancement: Its relationship to relapse. J Oral Maxillofac Surg 42:578, 1984 12. Smith GC, Maloney FB, West RA: Mandibular advancement surgery. A study of the lower border wiring technique for osteosynthesis. Oral Surg Oral Med Oral Path01 60:467, 1985 13. Epker BN, Wessburg GA: Mechanisms of early skeletal relapse following surgical advancement of the mandible. Br J Oral Surg 20:172, 1982 14. Schendel SA, Epker BN: Results after mandibular advancement surgery: An analysis of 87 cases. J Oral Surg 38:265, 1980 15. Reynolds ST, Ellis E, Carlson D: Adaptation of the suprahyoid muscle complex to large mandibular advancements. J Oral Maxillofac Surg 46: 1077, 1986 16. Ellis E, Gallo WJ: Relapse following mandibular advancement with dental plus skeletal maxillomandibular fixation. J Oral Maxillofac Surg 44:509, 1980 17. Mayo KH, Ellis E: Stability of the mandible after advancement and use of dental plus skeletal maxillomandibular fixation: An experiment in investigation in macaca mulatta. J Oral Maxillofac Surg 45:245, 1987 18. Sesenna E, Raffaini M: Bilateral condylar atrophy after combined osteotomy for correction of mandibular retrusion. J Maxillofac Surg 13:263, 1985 19. O’Rvan FS: Comnlications of orthonnathic surgery. Part I: Mandibular surgery. Se1 Read Oral Maxillofac Surg 1:1, 1989 20. Greebe RB, Tuinzing DB: Mandibular advancement procedures: Predictable stability and relapse. Oral Surg Oral Med Oral Path01 57:13, 1984 21. Nitzan DW, Dolwick MF: Temporomandibular joint fibrous ankylosis following orthognathic surgery: report of eight cases. Int J Adult Orthod Orthognath Surg 4:7, 1989 22. Ellis E, Carlson DS: The effects ofmandibuiar immobilization of the masticatory system: A review. Clin Plast Surg 16:133, 1989 23. Bays RA, Van Sickels JE, Tiner BD: Peralveolar suspension wires: A simplified technique of skeletal fixation. J Oral Maxillofac Surg (submitted)
Surg
1991
A Comparative Study of Bicortical Screws and Suspension Wires Versus Bicortical Screws in Large Mandibular Advancements JOSEPH E. VAN SICKELS,
DDS*
Relapse with large mandibular advancements treated by bicortical position screws has been documented in the literature. This study compares stability seen with two groups of patients; one treated with bicortical position screws and allowed to function, the second treated with bicortical position screws, skeletal wires, and 1 week of maxillomandibular fixation. Both groups had large advancements. The screw group was advanced an average of 10.9 mm, whereas the screw and wire group was advanced 12.2 mm. The screw group relapsed an average of 2 mm in the first 6 weeks, with further relapse occurring after that point. In contrast, the screw and wire group relapsed an average of 0.6 mm in the first 6 weeks, followed by a small advancement in the long term. Differences between the two groups were significant in the first 6 weeks and from the initial postoperative period to the long-term examination point. While stability was markedly improved with up to 13 mm of advancement in the group with screws and wires, relapse was noted after that amount of advancement. Methods to keep larger advancements stable are reviewed.
ear movement at the osteotomy site.‘0-‘4 Both clinical and animal studies have shown that relapse with wire osteosynthesis can be prevented or minimized with skeletal suspension wires and a 6- to S-week period of maxillomandibular fixation (MMF). 14-” Knowing that relapse occurs with large advancements treated with bicortical screws, based on the previous studies,14“7 it seems reasonable to assume that such relapse may be prevented with skeletal fixation and a period of MMF. The purpose of this article is to compare stability seen in two groups of patients with large advancements treated with bicortical screws. One group was treated with three bicortical screws per side and was allowed to function immediately after surgery. The second also had skeletal wires used and was placed in MMF for approximately 1 week.
Rigid fixation with bicortical screws after a bilateral sagittal ramus osteotomy with mandibular advancement has been well established in the literature.le3 Early reports noted excellent stability with little or no relapse4+ however, with larger advancements, relapse has been noted to occur.437,8 In a recent article, a segment of patients treated with bicortical screws had 25% or greater relapse; the majority of relapse was noted to occur at the osteotomy site in the first 6 weeks.’ Studies evaluating relapse with large advancements treated by wire osteosynthesis have likewise noted relapse to occur early, with rotatory and lin* Professor, Director of Dentofacial Deformities Clinic, Department of Oral and Maxillofacial Surgery, University of Texas Health Science Center, San Antonio. Address correspondence and reprint requests to Dr Van Sickels: Department of Oral and Maxillofacial Surgery, The University of Texas Health Science Center. 7703 Floyd Curl Dr, San Antonio, TX 78284-7908. 0 1991 American
Association
of Oral and Maxillofacial
Materials and Methods
Sur-
The cephalometric records of mandibular advancement patients treated by a bilateral sagittal
geons 0278-2391/91/4912-0006$3.00/O
1293
1294
COMPARISON OF SUSPENSION
ramus osteotomy by one surgeon at the University of Texas Health Science Center at San Antonio were retrospectively reviewed. Preoperative cephalometric tracings were made and compared with an initial corrected postoperative film. The latter film was corrected for splint thickness by superimposing a template on the mandible and rotating it on condylion until the teeth touched. The Sella-Nasion line was traced. A horizontal reference line from SN was likewise traced (HP). From HP a vertical reference line was drawn. The amount of advancement at the chin point (pogonion) was then measured. Advancements of less than 7 mm were not included. All advancements of 7 mm or greater were evaluated. Two groups were generated. One group had three 2 mm bicortical position screws placed at the osteotomy sites. They were allowed to function with splints in place, with three box elastics allowing immediate function. The elastics were placed bilaterally in the premolar-molar region and anteriorly in the central incisor region. These training elastics were generally used for 2 to 3 weeks. A second group of patients had three 2-mm bicortical position screws placed at the osteotomy site, skeletal suspension, and approximately 1 week of MMR. Splints were also used in this group. Skeletal suspension consisted of a 24-gauge wire placed bilaterally at the piriform fossa tied to the splint and two circumferential mandibular wires tied over the orthodontic arch wire bilaterally in the premolar region. Maxillomandibular fixation was applied by tying a 24 gauge wire from the splint in the region of the maxillary skeletal suspension wires to the circumferential mandibular wires. This was left for about 1 week. Training elastics were used following removal of fixation for about 2 weeks. Splints were removed in both groups at 2 weeks. Cephalometric radiographs were available for both groups preoperatively (Tl), initial postoperative (T2), 6 weeks postoperative (T3), and long-term postoperative (T4) (a minimum of 6 months). T4 in the no wire group ranged from 6 months to 4 years Table 1.
WIRES AND SCREWS VS SCREWS
(2.1 year average). T4 in the wire group ranged from 6 months to 6 years (1.6 year average). Once the radiographs were traced, they were superimposed for a best fit on anterior and posterior cranial base landmarks. Pogonion was chosen on each successive radiograph by superimposing on the chin point from the Tl radiographic tracing. All radiographs were then digitized and linear measurements were calculated using Dentofacial Planner Software (Toronto, Canada). Unpaired t tests were used to compare the amount of movement seen at the different time intervals (Tl-T2, T2-T3, T3-T4, T2-T4) between the two groups. In addition, movement within groups during the time intervals of T2-T3, T3-T4, and T2-T4 were compared against zero change using paired t tests. Results Eleven patients were advanced 10.9 + 3 mm (range, 6.6 to 15.5 mm) in the group fixed by position screws and allowed to function immediately. Of these, 6 had advancement genioplasties, and 5 did not. Fifteen patients were advanced 12.2 * 4 mm (range, 6.8 to 23.9 mm) in the group fixed by position screws and kept in fixation an average of 6 days. Twelve of these patients had advancement genioplasties, and 3 did not. There was no significant difference between the amount of advancement in the two groups (P < .39) (Table 1). Amount of relapse in the screw group in the first 6 weeks (T2-T3) was significant 2.0 ‘- 1.7, (P < .003) with further relapse occurring long term (Fig 1). The amount seen in the time interval T2-T3 in the group fixed with screws and stabilizing suspension wires was not significant 0.6 -+ 1.5, (P < .16) followed by a small advancement (Fig 2). The difference between the two groups was significant at P < .05 at both T2-T3 and T2-T4, but not at the T3-T4 time interval. Scattergrams of the two groups (Fig 3) show how the individual patients performed.
Comparative Results, Large Advancements Wires (n = 15)
No Wire (n = 11) Change
Mean(mm)
Preoperative to initial postoperative Initial postoperative to 6 weeks postoperative Initial postoperative to long-term postoperative 6 Weeks postoperative to long-term postoperative
10.9
SD(mm)
Rang-e Change(mm)
P
3.0
6.6 to 15.5
.oool
-2.0
1.7
-5 to 1.1
.003
-3.7
2.9
-8.6 to 2.2
.004
-1.6
2.9
-8.3 to 1.1
.159
Mean (mm)
12.2
SD(mm)
Range Change(mm)
P
Wire vs No Wire P Value
4.0
6.8 to 23.9
.OOOl
.39
-0.6
1.5
-3.2 to 2.1
.162
.032
-0.5
2.4
-6.5 to 2.6
.405
.006
1.7
- 3.9 to 2.3
.824
.067
0.1
1295
JOSEPH E. VAN SICKELS
1210-
a64E 20 -2-4-10,
-6-1 No Wires (Ti-T2)
No Wires (T2-T3)
No Wires (T3-T4)
No Wires (T2-T4)
(
(
,
10 15 No Wires (Tl-T2) (mm)
B5
20
FIGURE 1. Movement seen and standard error in the different time intervals with the group of patients treated with three bicortical screws alone.
Discussion This was not a prospective randomly designed study, as the patients included were treated over slightly different time intervals. The group of patients treated by screws alone were managed earlier in the experience of the author. While the two groups broadly overlap, as more experience was gained with rigid fixation the need for an auxiliary technique to manage large advancements was noted. Hence, around 1987 to 1988, advancements of the mandible larger than 6 to 7 mm were treated with three bicortical screws, suspension wires, and approximately 1 week of MMF. Nonetheless, there are many points that can be gleaned from these data. Perusal of the scattergram for the group with just bicortical screws (Fig 3A) shows that at about 6 ‘41 12lo-
a: 642O-2J Wire (Tl -T2)
Wires (T2-T3)
Wires (T3-T4)
Wires (T2-T4)
FIGURE 2. Movement seen and standard error in the different time interval with the group of patients treated with three bicortical screws, suspension wires, and approximately 1 week of MMF.
lo
Wires (TitT2) (mm)
2o
25
FIGURE 3. A, Scattergram for position screw only (no wire) group. Initial advancement on x axis, long-term advancement result only. B, Scattergram for position screw suspension and MMF group (wire). x and y axis the same.
to 7 mm, the patients showed relapse when the initial advancement was compared with the long-term position at pogonion. This was similar to the previous reports from this institution.798 In contrast, the second group did much better, not showing relapse until 13 to 14 mm of initial advancement (Fig 3B). What is worrisome in comparing Figures 1 and 2 is that the group with immediate function showed further instability after 6 weeks, in contrast to the fixation and skeletal wire group, which did not. Where the late relapse occurred is speculative. While instability at the osteotomy site has been shown to account for early relapse,’ long-term instability is thought to be secondary to condylar resorption and/ or remodeling. 18,19 Although magnitude of advancement is an important factor in relapse, many other causes have been suggested. These include technical factors, high angle cases, condylar resorption, condylar distraction, proximal segment control, and density of bone.9“4*18-20A review of both scatter-grams shows
1296
COMPARISON OF SUSPENSION
that individual patients did not follow the same pattern. This suggests that other factors played a role in the results seen in both groups. It is interesting that in the group with suspension wires and MMF there is a closer clustering of the patients. Perhaps suspension wires and MMF negate more than one of the factors involved in relapse. The primary question asked in this study was answered in that use of skeletal wires combined with MMF gives better stability than use of position screws alone. Although relapse may have multiple causes, large advancements, with their concomitant stretch on the surrounding soft tissue of the mandible, require that the neuromuscular apparatus adapt to the new position. Reynolds et al” showed that with large advancement, major adaptations occur at the muscle-bone and muscle-tendon interfaces and within the belly of the anterior digastric muscle. Furthermore, they showed that these changes occur early, within the first few weeks. Our patients who had position screws and skeletal wires placed with MMF showed greater short- and long-term stability when advanced up to 13 mm. This suggests that these auxiliary procedures are helpful in allowing the neuromuscular apparatus to adapt to change in mandibular position. However, even in this group, the amount of advancement eventually put too much tension on the system and relapse was seen. Two questions remain: 1) What can be done for cases with very large advancements?, and 2) Which auxiliary technique is important in preventing relapse, MMF or skeletal wires? The answer to the first question is related to the second. Larger screws, plates, and overadvancements are all possible ways to solve the problem. An increased period of MMF may also help; however, one must weight the disadvantages of MMF in the presence of rigid fixation.*“** Although skeletal wires in the pattern used have been shown to be effective, an alternative pattern of three wires may be more effective.23 The answer to the second question is speculative. Maxillomandibular fixation alone has not been shown to prevent relapse with wire osteosynthesis.10-12,14-17 However, there are no studies showing what happens to stability when screws are combined with MMF. Nitzan and Dolwick2’ believed that 6 to 8 weeks of MMF should not be used with rigid fixation, and reported on five cases with joint fibrous following this therapy. A lesser period of time, however, may not be detrimental. Skeletal wires, in contrast, have been shown to be very effective when combined with MMF.13-” Whether they would be equally effective if used with elastic traction is unknown. Ideally, each of the questions should be answered in a prospective study.
WIRES AND SCREWS VS SCREWS
References 1. Spiessl B: The sagittal splitting osteotomy for correction of mandibular nronnathism. Clin Plast Sum 9:491. 1982 2. Jeter TS, Van Sickels JE, Dolwick MF: Modified techniques for internal fixation of sagittal ramus osteotomies. J Oral Maxillofac Surg 42:270, 1984 3. Niederdellmann H, Shetty V, Collins FJV: Controlled osteosynthesis utilizing the position screw. Int J Adult Orthod Orthognath Surg 2:159, 1987 4. Thomas PM, Tucker MR, Prewitt JR, et al: Early skeletal and dental changes following mandibular advancement and rigid internal fixation. Int J Adult Orthod Orthognath Surg 1:171, 1986 5. Van Sickels JE, Flanary CM: Stability associated with mandibular advancement treated by rigid osseous fixation. J Oral Maxillofac Surg 43:338, 1985 6. Kirkpatrick TB, Woods, MG, Swift JQ, et al: Skeletal stability following mandibular advancement and rigid tixation: J Oral Maxillofac Surg 45572, 1987 7. Van Sickels JE. Larsen AJ. Thrash WJ: Relanse of rieidlv fixated mandibular advancements: Contributing fact&. J Oral Maxillofac Surg 44:698, 1986 8. Van Sickels JE, Larsen AJ, Thrash WJ: Retrospective study of relapse in rigidly fixated sagittal split osteotomies: Contributing factors. Am J Orthod Dentofacial Orthop 93:413, 1988 9. Gassmann CS, Van Sickels JE, Thrash WJ: Causes, location and timing of relapse following rigid fixation after mandibular advancement. J Oral Maxillofac Surg 48:450, 1990 10. Lake SL, McNeil RW, Little RM, et al: Surgical mandibular advancement: A cephalometric analysis of treatment response. Am J Orthod 80~376, 1981 11. Will LA, Joondeph DR, Hohl TH, et al: Condylar position following mandibular advancement: Its relationship to relapse. J Oral Maxillofac Surg 42:578, 1984 12. Smith GC, Maloney FB, West RA: Mandibular advancement surgery. A study of the lower border wiring technique for osteosynthesis. Oral Surg Oral Med Oral Path01 60:467, 1985 13. Epker BN, Wessburg GA: Mechanisms of early skeletal relapse following surgical advancement of the mandible. Br J Oral Surg 20:172, 1982 14. Schendel SA, Epker BN: Results after mandibular advancement surgery: An analysis of 87 cases. J Oral Surg 38:265, 1980 15. Reynolds ST, Ellis E, Carlson D: Adaptation of the suprahyoid muscle complex to large mandibular advancements. J Oral Maxillofac Surg 46: 1077, 1986 16. Ellis E, Gallo WJ: Relapse following mandibular advancement with dental plus skeletal maxillomandibular fixation. J Oral Maxillofac Surg 44:509, 1980 17. Mayo KH, Ellis E: Stability of the mandible after advancement and use of dental plus skeletal maxillomandibular fixation: An experiment in investigation in macaca mulatta. J Oral Maxillofac Surg 45:245, 1987 18. Sesenna E, Raffaini M: Bilateral condylar atrophy after combined osteotomy for correction of mandibular retrusion. J Maxillofac Surg 13:263, 1985 19. O’Rvan FS: Comnlications of orthonnathic surgery. Part I: Mandibular surgery. Se1 Read Oral Maxillofac Surg 1:1, 1989 20. Greebe RB, Tuinzing DB: Mandibular advancement procedures: Predictable stability and relapse. Oral Surg Oral Med Oral Path01 57:13, 1984 21. Nitzan DW, Dolwick MF: Temporomandibular joint fibrous ankylosis following orthognathic surgery: report of eight cases. Int J Adult Orthod Orthognath Surg 4:7, 1989 22. Ellis E, Carlson DS: The effects ofmandibuiar immobilization of the masticatory system: A review. Clin Plast Surg 16:133, 1989 23. Bays RA, Van Sickels JE, Tiner BD: Peralveolar suspension wires: A simplified technique of skeletal fixation. J Oral Maxillofac Surg (submitted)
