British Journal of Oral and Maxillofacial Surgery (2004) xxx, xxx xxx The skeletal stability of one-piece Le Fort 1 osteotomy to advance the maxilla Part 2. The influence of uncontrollable clinical variables 3 G.R. Hoffman a,1, P.A. Brennan b,c, * a Princess Alexandra Hospital, Brisbane, Qld, Australia 4 b Maxillofacial Department, Queen Alexandra Hospital, Portsmouth, Cosham, UK 5 c 6 Portsmouth Hospitals NHS Trust, Portsmouth PO6 3LY, UK 7 8 9 10 11 12 13 14 15 21 22 23 24 25 26 27 28 29 30 31 KEYWORDS Le Fort 1 osteotomy; Skeletal stability; Maxilla; Clinical variables Introduction The aim of orthognathic surgery is to correct a dental malocclusion and facial deformity. These occlusal-based facial deformities in essence are assessed and managed according to symmetry and profile evaluations. The first part of our study acknowledged that the attainment of three-dimensional skeletal stability after corrective jaw surgery remains a problem during the post-surgical period. Recent studies of post-operative skeletal stability after such surgery *Corresponding author. Tel.: +44-2392-286064; fax: +44-2392-286089. E-mail address: peter.brennan@porthosp.nhs.uk (P.A. Brennan). 1 Present address: Queen Alexandra Hospital, Portsmouth, Cosham, UK. Summary The stability of orthognathic surgery has been the subject of numerous publications over the last 20 years. It is now apparent that studies must pay attention to the homogeneity of the patients investigated and in particular, surgical techniques. In Part 2 of our study of 45 patients who had a uniform one-piece maxillary advancement with rigid fixation to advance the maxilla, we found that uncontrollable variables, including patients age, sex, the degree of advancement, and simultaneous mandibular advancement, had no effect on post-operative skeletal stability. 2004 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. have highlighted the need to promote, where prac- 32 tical, the elimination of clinical variables. 1 This is 33 to ensure that the investigation is based on a ho- 34 mogenous group of patients. 35 The second part of this study evaluated retro- 36 spectively the influence of uncontrollable clinical 37 variables on the post-surgical stability of one-piece 38 Le Fort 1 osteotomy to advance the maxilla. 39 Patients and methods 40 We studied 45 patients who were treated for 41 horizontal maxillary deficiency were studied. Pa- 42 tient selection, surgical technique, follow up and 43 cephalometric analysis have previously been doc- 44 umented in Part 1. Pearson s product moment 45 correlation and tailed paired t tests were used to 46 1 0266-4356/$ see front matter 2004 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. 2 doi:10.1016/j.bjoms.2004.01.004
2 G.R. Hoffman, P.A. Brennan Table 1 Mean (S.D.) of surgical changes (mm) and stability by sex of patient. Sex Number of patients Overall change Change at 6 weeks Change at 12 months Short-term relapse Long-term relapse Male 13 8.6 (3.65) 8.4 (3.9) 8.1 (4.3) 0.20 (0.40) 0.50 (0.97) Female 32 6.9 (2.9) 6.5 (3.0) 6.1 (2.5) 0.50 (0.80) 0.80 (1.05) Total 45 7.4 (3.3) 7.0 (3.3) 6.7 (3.2) 0.40 (0.70) 0.70 (1.03) There were no significant associations. Table 2 Crude and sex- and age-adjusted mean changes over time in 45 patients. Crude mean (S.E.) S.D. Adjusted mean (S.E.) S.D. Surgical change 7.42 (0.48) 3.2 7.78 (0.53) 3.5 Remaining at 6 weeks 7.04 (0.50) 3.3 7.45 (0.54) 3.6 Remaining at 12 months 6.71 (0.48) 3.2 7.13 (0.54) 3.6 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 find out whether there were any correlations or differences between patient variables and stability. Probabilities of less than 0.05 were regarded as statistically significant. Power of study With the observed standard deviation of the distribution of long-term differences from surgical change of 1.031 and with 45 patients studied, it was possible to detect differences over time of 0.50 or greater with 90% power at the 95% significance level. Results All results are shown in Tables 1 4. There were no correlations found between patient s ages and surgical change and stability. There were no statistically significant associations between male Table 3 Influence of simultaneous mandibular advancement on relapse in the maxilla (P = 0.27). Procedure Number of patients Mean (S.E.) S.D. Maxilla only 1 8.3 (0.6) 3.3 2 8.0 (0.6) 3.3 3 7.6 (0.58) 3.2 Maxilla and mandible 1 6.2 (1.2) 4.6 2 5.6 (1.22) 4.7 3 5.0 (1.16) 4.5 (all skewed) and female sex and surgical change (P = 0.11), 63 short-term stability (P = 0.08), or long-term stabil- 64 ity (P = 0.09) (Table 1). Accounting for differences 65 in age and sex in the repeated measures analy- 66 sis of variance did not alter the conclusion that 67 there were significant changes over time (adjusted 68 analysis F 2,41 = 3.04, P = 0.06) (Table 2). 69 Table 3 shows the influence of simultaneous 70 mandibular advancement on maxillary relapse. 71 While this revealed an overall lesser advancement 72 for patients who underwent combined maxillary 73 and mandibular advancement (6.2 mm compared 74 with 8.2 mm), there was no significant associa- 75 tion between maxillary relapse and the inclusion 76 of mandibular advancement (P = 0.27). However, 77 clinically the relapse over the 12-month period for 78 combined maxillary and mandibular advancement 79 was twice that of maxillary advancement alone 80 (1.2 mm compared with 0.6 mm), although this was 81 of little clinical significance. 82 Table 4 shows the influence of the amount of 83 maxillary advancement on maxillary relapse. Once 84 Table 4 Influence of the amount of maxillary advancement on relapse in the maxilla. Distance (mm) Number of patients Mean (S.E.) 4.8 11 3.2 (0.56) 2.9 (0.53) 4.9 7.1 12 5.4 (0.47) 4.9 (0.45) 7.2 9.4 10 7.5 (0.54) 6.9 (0.52) 9.5 12 11.1 (0.39) 10.6 (0.37)
The skeletal stability of one-piece Le Fort 1 osteotomy to advance the maxilla 3 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 again, there was no evidence to suggest that instability over time was any greater for one surgical change group compared to any other (P = 0.9). However, clinically for surgical change less than 4.8 mm, the relapse was only half as much. Further to this, the relapse for advancements greater than 4.9 mm was similar regardless of the amount of movement. Discussion The 45 patients in this study had a one-piece Le Fort 1 osteotomy without bone grafting and fixed internally to advance the maxilla, combined with orthodontic detailing. Fifteen patients also underwent simultaneous mandibular advancement. The requirement for bone grafting and its contribution to stability This remains a contentious issue. Theoretically, rigid internal fixation should, at the very least, afford short-term (and, ideally long-term) stability. However, if there is poor bone approximation at the osteotomy site, union may be delayed or even fail to occur. Relapse in such circumstances might be expected. Autogenous bone grafting may help to accelerate bony union, act as a mechanical stop, provide a matrix for secondary reconstruction and prevent soft tissue herniation into the osteotomy. 2 Wilmar 3 showed that no significant difference existed between 16 grafted maxillary osteotomies and 43 which were non-grafted, in relation to the potential for post-operative horizontal and/or vertical change. A mean surgical advancement of 7.2 mm was identified. In contrast, Araujo et al. 4 claimed improved stability of total maxillary advancement with bone grafts to a mean of 6.0 mm. Overall relapse ranged from 31 68% without bone grafts, compared to 0 5% with grafts. A shortcoming of these two studies is that they both comprised a heterogenous cohort, which included idiopathic, cleft and post-traumatic deformities as well as edentulous pre-prosthetic deformity. Nevertheless, their conclusions would seem to support the contention of bone grafting for maxillary advancements of more than 6.0 mm and certainly for those in excess of 10.0 mm. Egbert et al. 5 selected 25 patients who underwent one-piece maxillary advancement osteotomy (without vertical change) utilising a bone graft. Although 13 patients that received rigid internal fixation appeared to have somewhat better stability than 12 patients receiving combined wire osteosyn- thesis and fixation, the difference was not statisti- 135 cally significant. 136 However, the importance of the role of bone 137 grafting could not be deduced because the entire 138 cohort had bone graft placed at the osteotomy site. 139 Kerawala et al. 6 assessed the influence of bone 140 grafting on Le Fort 1 osteotomy in patients without 141 clefts. Appropriately they excluded 77 of their origi- 142 nal cohort of 189 patients on the basis of incomplete 143 records or cleft, segmental or syndromal surgery. 144 Of the remaining 112 patients, 40 involved the max- 145 illa in isolation and 72 had bimaxillary procedures. 146 Unfortunately the 112 maxillary procedures again 147 included a heterogenous group comprising anterior, 148 superior or inferior repositioning. Numerical values 149 for each of the subgroups were not included for as- 150 sessment. Superior repositioning proved to be the 151 most stable movement. Advancements were in the 152 order of 4.0 mm with relapse of 0.1 mm (2.5%). They 153 concluded that the anteriorly repositioned maxilla 154 may be more stable if a bone graft is used. 155 In our study, the maxilla was advanced an aver- 156 age of 7.42 mm (range 1.8 15.3 mm). The maxillae 157 were not bone grafted. There were no cases of de- 158 layed or non-union. 159 Does the degree of advancement contribute 160 to relapse? 161 Louis et al. 7 studied 20 patients retrospectively 162 who had rigidly fixed maxillary advancement with- 163 out bone grafts in who underwent bimaxillary ad- 164 vancement to treat (non-orthodontic) obstructive 165 sleep apnoea. In order to assess whether the mag- 166 nitude of advancement correlated with the magni- 167 tude of relapse they divided their cohort into three 168 groups (data are mean and S.D.): less than 6 mm 169 (4.7 ± 0.8; n = 4); 7 9 mm (8.2 ± 0.9; n = 9) and 170 greater than 10 mm (12.3 ± 2.8; n = 7). 171 The mean and S.D. relapses identified for each 172 group were 0 (0.6 mm) in the first group, 0.7 173 (1.5 mm) in the second and 1.9 (1.8 mm) in the 174 third. The numbers in each group were small, and 175 they concluded that statistically there was no sig- 176 nificant difference in measured relapse. However, 177 it would seem likely that the greater the advance- 178 ment the greater the relapse, not withstanding its 179 clinical insignificant nature. Of note was that two 180 patients relapsed in a positive direction (1.5 181 and 2.5 mm, respectively) and one patient relapsed 182 5.0 mm. These results are clearly clinically signif- 183 icant and undoubtedly impact on the statistical 184 analysis. The mean surgical change in our study was 185 7.4 mm (1.8 15.3 mm). The relapse rate therefore 186 is equivalent to the second group in their study. 7 187
4 G.R. Hoffman, P.A. Brennan 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 The relapse therefore seems to be comparable in maxillary advancement without bone grafts. Do the age and the sex of the patient contribute to relapse? Phillips et al. 8 evaluated 60 patients who underwent maxillary surgery. Thirty had one-piece impaction. They found that the maxilla tended to intrude slightly during the fixation period. In patients older than 19 years, there was no tendency for the maxilla to move downward in the follow-up period. In contrast, in patients less 19 years, there was an average downward movement of 2 mm, which was attributed to late vertical growth. Bishara et al. 9 studied 31 patients who underwent maxillary superior repositioning, and found no significant differences between the younger (less than 20 years) and older patients. In the same study, comparisons of the absolute and relative surgical changes (day 1), during fixation (5 weeks) and during postfixation (5 months) did not differ significantly when comparing the sex of the patient. There were 12 patients who had correction of anterior open bite. There were also no significant differences between surgical teams and differing durations of fixation. Does the influence of simultaneous mandibular advancement compromise the stability of the maxilla? The Le Fort 1 is the most frequently performed midfacial osteotomy. We have increasing tended to do maxillary advancement in isolation to treat Class III patients, obviating the need for a simultaneous mandibular set back procedure. Historically, the most frequent indication for simultaneous two-jaw surgery has been a combination of vertical maxillary excess (with or without open bite) together with horizontal mandibular deficiency. The actual degree of mandibular advancement has generally been somewhat less than expected due to the associated autorotation. In the literature it is being increasingly undertaken without orthodontics to treat obstructive sleep apnoea patients. This has resulted in larger mandibular advancements due to: (a) the initial antero-posterior discrepancy; (b) the further discrepancy resulting from simultaneous maxillary advancement; (c) a lack of autorotation because there is no planned vertical change in position of the maxilla. What has been the effect of mandibular advance- 239 ment on the stability of the maxilla in treating the 240 Class II dentofacially retrusive patient? It has been 241 stated that bimaxillary surgery may be more sta- 242 ble due to a physiologic splinting of the jaws that 243 is different from that in isolated maxillary surgery, 244 where the mandible remains intact. 10 The tendency 245 for mandibular relapse can be offset by the appli- 246 cation of light Class II intermaxillary elastic trac- 247 tion to maintain the antero-posterior position of the 248 mandible, particularly during osseous consolidation 249 at the osteotomy site. The vector and force gener- 250 ated by such manoeuvres seem to have no impact 251 on the spatial position of the maxilla. 252 What is the effect of orthodontic treatment 253 on the stability of the maxilla? 254 The principle of combined surgical and orthodon- 255 tic management of dentofacial deformity has been 256 to expand the facial profile whilst correcting the 257 relationship between the dentition and their re- 258 spective skeletal bases by orthodontic decompensa- 259 tion. As orthodontic treatment has relied on making 260 the incisors upright rather than flaring them, small 261 amounts of skeletal relapse can be offset to some 262 extent by post-surgical orthodontic detailing. The- 263 oretically, there should be no effect on the stability 264 of the skeletal elements. 265 What is the role of growth on the stability of 266 the maxilla? 267 Adverse and/or late growth of the mandible in pa- 268 tients with a true skeletal III tendency may con- 269 tribute to the re-establishment of a negative over- 270 jet but should play no role in effecting maxillary 271 stability. 272 Part 2 of the current study revealed that un- 273 controllable variables, including patients age, sex, 274 together with the magnitude of advancement and 275 the influence of simultaneous mandibular advance- 276 ment, had no effect on the post-operative skeletal 277 stability in orthodontically prepared, rigidly fixed 278 one-piece Le Fort 1 osteotomy without bone graft- 279 ing to advance the maxilla. 280 References 281 1. Costa F, Robiony M, Politi M. Stability of Le F ort 1 osteotomy 282 in maxillary advancement: review of the literature. Int J 283 Adult Orthod Orthognath Surg 1999;14:207 13. 284 2. Epker B, Schendel S. Total maxillary surgery. Int J Oral Surg 285 1980;9:1 24. 286
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