ORIGINAL ARTICLE
Cephalometric Outcomes of Orthognathic Surgery in Hemifacial Microsomia Adel Y. Fattah, PhD, FRCS(Plast),* Camila Caro, DDS,Þ David Y. Khechoyan, MD,* Bryan Tompson, DDS, DOrth,Þ Christopher R. Forrest, MD, MSc,* and John H. Phillips, MD, FRCSC* Abstract: Hemifacial microsomia is a hypoplastic disorder of the first and second branchial arches that significantly impacts on the development of the jaws, leading to malocclusion and facial asymmetry. There is little in the literature regarding the application of orthodontic/orthognathic approaches to the correction of these deformities and the stability of the surgical results. To address this, a retrospective chart review of 10 patients with complete orthodontic records and greater than 1 year of follow-up was performed. Posteroanterior cephalograms were assessed by modified Grummons analysis to determine mandibular offset (deviation of the chin point from the skeletal midline) and occlusal cant. These measurements were performed at 3 time points (T1: preoperative, T2: immediate postoperative, T3: follow-up) to elucidate the surgical movement (T2YT1), the postoperative relapse (T3YT2), and the net gain movement (T3YT1). Maxillary movements were quantified, and the occlusal cant was expressed as a ratio between vertical heights of the maxilla at the first molar on each side. One sample t test demonstrated statistically significant surgical movement and net gain. Relapse was statistically insignificant. Repeated-measures analysis of variance demonstrated similar results for chin point position relative to the putative midline. Our results suggest that a combined orthodontic/orthognathic approach at skeletal maturity delivers improved occlusal outcomes in the long term as assessed by chin point deviation and occlusal cant, but secondary surgery rates are higher than those for orthognathic surgery in other patient groups. We advocate limiting surgery to skeletal maturity whenever possible to achieve stable long-term results while limiting morbidity and number of procedures. Key Words: Hemifacial microsomia, orthognathic, orthodontic, occlusion (J Craniofac Surg 2014;00: 00Y00)
H
emifacial microsomia (HFM; craniofacial microsomia) is a disorder causing hypoplasia of the first and second branchial
From the *The Centre for Craniofacial Care and Research, Division of Plastic Surgery, and †Division of Orthodontics, Hospital for Sick Children, Toronto, Ontario, Canada. Received January 20, 2013. Accepted for publication August 12, 2013. Address correspondence and reprint requests to Adel Y. Fattah, PhD, FRCS(Plast), The Centre for Craniofacial Care and Research, Division of Plastic Surgery, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8; E-mail: [email protected] The authors report no conflicts of interest. Copyright * 2014 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/01.SCS.0000435808.91512.58
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arch derivatives leading to facial asymmetry. It comprises a spectrum of severity ranging from preauricular skin tags and microtia to bilaterally asymmetric abnormalities of the craniofacial complex together with extracranial anomalies.1 The phenotype expresses myriad dysmorphologies neatly summarized by the OMENS classification,2,3 chief among which is the jaw hypoplasia affecting the skeletal and soft tissue components of this functional unit. This leads to diminished anteroposterior, vertical, and transverse dimensions of the face on the affected side with contralateral secondary deformities resulting in facial imbalance, asymmetric class II malocclusion with anterior open bite, an occlusal cant, and deviation of the chin to the affected side. This has ramifications for mastication as well as for speech and may significantly impact on the body image of the patient.4 As a result, surgical correction of the deformity is frequently sought. Patients with HFM presenting to the Hospital for Sick Children Centre for Craniofacial Care and Research undergo a treatment protocol that consists of a combined approach to their dentofacial difference. Patients undergo a multidisciplinary team assessment including dental, speech, orthodontic, and plastic surgical consultations. Those patients with severe mandibular hypoplasia may require a free rib graft at an early age in addition to other surgeries such as ear reconstruction. However, we have previously noted that the deformity does not increase with time,5 and we therefore aimed to perform correction at skeletal maturity whenever possible to achieve stable results. The final correction of occlusion is achieved by using a combined orthodontic/orthognathic approach, but this is often challenging because of previous surgery, poor bone stock, and soft tissue deficiency. The aims of orthognathic surgery in this population were to level the occlusal cant, to align the dental midline to that of the face, and to achieve an Angle class I occlusal relationship on a skeletal class I base. An initial phase of presurgical orthodontics is performed to decompensate the dentition in readiness for the surgical movement. Cephalometric planning and model surgery are performed in the standard fashion to generate acrylic surgical registration splints to guide the positioning of the osteotomy segments. Bimaxillary surgery (Le Fort I and bilateral sagittal split osteotomies T genioplasty) is performed and followed by postoperative orthodontics to refine the occlusal result. Objective cephalometric and outcome analysis is difficult, and there is little in the literature that examines the outcomes of orthognathic correction of occlusion in HFM. Our purpose was to retrospectively determine the cephalometric outcome of orthognathic surgery in this challenging patient group, specifically examining the stability of the surgical movement more than 1 year after surgery.
MATERIALS AND METHODS A retrospective review of all cases of HFM treated with orthognathic surgery by the senior author (J.P.) between 1993 and 2006 was performed. Both unilateral and bilateral cases were included, where the side of greater deformity was termed the affected
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side for the purpose of this analysis. Patients were included if complete posterior-anterior (PA) cephalometric and orthodontic records at 3 time points were available (T1: Presurgical, T2: immediate postsurgical, and T3: at least 1 year after surgery). Patients were excluded if they had other craniofacial abnormalities (eg, craniosynostosis or cleft lip/palate) or underwent distraction osteogenesis of the mandible. The mandibular deformity was graded according to the modified Pruzansky classification.6 In general, our institution waits until skeletal maturity to perform bimaxillary surgery comprising a Le Fort I osteotomy and bilateral sagittal split osteotomies of the mandible without bone grafting. Costochondral grafts at 5 to 7 years are used only if there is no articulation with the nascent glenoid fossa. By contrast, most cases have some putative articulation whereby the hypoplastic mandible ‘‘buttresses’’ against the skull base, and in these cases, a sagittal split osteotomy to lengthen the mandible is performed later. Lateral cephalograms cannot be used to accurately assess orthognathic movements in individuals with significant asymmetry. To determine the movement of the occlusal plane in such an individual, PA cephalograms were assessed by a modified Grummons analysis7 (Fig. 1) using the Dentofacial planning software version 7.02 (Dentofacial Research Inc, Toronto, Canada). Because the goal was to assess the movement of the Le Fort I segment and mandible relative to a fixed skeletal point, a plane was chosen, which
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connected the points on each lateral orbital rim at the inner aspect of the frontozygomatic suture; this was termed the Z-plane. At the crista galli, a perpendicular to the Z-plane was drawn and this was considered to be the putative midline. To reflect the movements of the chin relative to this midline, the mandibular offset (distance of the menton from this midline) was measured. The distance of the buccal cusp of the first maxillary molar along a perpendicular to the Z-plane was measured to determine the vertical position of the Le Fort I segment on each side. This was termed the Z-A6 height; the difference of which reflected the occlusal cant. In addition, to express the occlusal cant numerically, a ratio was determined by dividing the ZA6 height of the affected side by that of the unaffected side. These measurements were performed for each of the 3 time points to elucidate the surgical movement (T2YT1), the postoperative relapse (T3YT2), and the net gain in surgical movement (T3YT1). Statistical analyses were performed using SAS 9.3 statistical software (SAS, Toronto, Canada).
RESULTS Twenty patients with HFM who underwent orthognathic surgery were identified, of which 10 met the strict inclusion criteria (Table 1). The mean age at surgery was 17.8 years (range, 12.8Y20.9 y) and the mean length of follow-up was 3.1 years (range, 1.1Y4.75 y). In this group, 6 patients were right-sided; 2, left-sided; and 2, with bilateral cases. All patients underwent bimaxillary surgery, with 1 receiving a genioplasty as part of the primary treatment protocol (Table 1; Fig. 2). Two patients had sagittal split osteotomy on a previously placed costochondral rib graft. One patient underwent a surgically assisted rapid palatal expansion 3 years before definitive orthognathic surgery.
Surgical Movements As part of the surgical plan in all patients, the maxilla was advanced, with a mean advancement of 4.4 mm (range, 0Y7.5 mm). With regard to the affected side, in 3 patients, the maxilla was impacted asymmetrically to level the occlusion; in 6 patients, the affected side was extruded in concert with a contralateral impaction; in 1 patient, there was a minimal change to the vertical height, relying on the impaction of the unaffected side to level the occlusion. The mandibular deviation was addressed with bilateral sagittal split osteotomies using differential movements aiming to direct the chin to the median; in 8 patients, this was achieved with bilateral advancements, with the affected side being advanced to a greater degree to correct the chin deviation. On the basis of the surgical plan, the mean mandibular advancement on the affected side was 16 mm (range, 3Y24 mm), whereas the mean advancement on the unaffected side was 8 mm (range, 2Y13 mm). Of the other 2 patients, correction of deviation was accomplished using a differential setback in 1 individual and the other required advancement on the unaffected side and setback on the other because of overgrowth of the costochondral rib graft.
Occlusal Cant FIGURE 1. The modified Grummons frontal asymmetry analysis. This focuses on the occlusal cant and the chin location. Above, The Z-plane is the fixed skeletal reference plane from which the measurements are derived. From this plane, a perpendicular is dropped from the crista galli. This constitutes the sagittal reference plane from which the distance to the menton is measured; this is termed the mandibular offset. On each side, the Z-A6 height is measured from the buccal cusp of the first maxillary molar along a perpendicular to the Z-plane. A ratio of the 2 heights reflects the occlusal cant. Below, Time points at which analysis was performed to determine the surgical movement, relapse, and net gain from surgical repositioning. T1: preoperative, T2: immediate postoperative, T3: follow-up of more than 1 year.
2
The mean (SD) surgical movement (Table 2) on the affected side was 1.04 (4.93) mm of extrusion coupled with 3.53 (8.23) mm of mean impaction of the unaffected side. The mean (SD) net extrusion at follow-up was 1.98 (5.63) mm on the affected side and the mean (SD) net impaction of the unaffected side was 3.69 (6.89) mm. The wide values for the standard deviation reflect that each side was impacted or extruded to achieve leveling of the occlusal cant while simultaneously correcting facial height. Therefore, an alternative method to express the occlusal cant would be to calculate a ratio of the Z-A6 heights of the affected to unaffected sides. By doing so, a mathematical expression of the occlusal cant (Z-A6 ratio) can be obtained and statistically * 2014 Mutaz B. Habal, MD
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TABLE 1. Patient Demographics, Surgical Movements, and Secondary Surgery Patient No. 1 2 3 4 6 8 9 10 11 14
Diagnosis Goldenhar sy (left) Left hemifacial microsomia Right hemifacial microsomia Right hemifacial microsomia Bilateral HFM (Rt 9 Lt) Right hemifacial microsomia Goldenhar sy (Rt 9 Lt) Right hemifacial microsomia Right hemifacial microsomia Right hemifacial microsomia
Prusansky Previous Surgery Age at Class /Other Comorbidity Surgery III
Left costochondral graft and SSO V
IIb
V
IIb IIb
SARPE
Procedure
Follow-up
18.3
Bimax
3.3
17.3
Bimax
1.8
13.6
Bimax
3.3
20.9
Bimax
2.7
17.7
4.1
III (Rt) Vertical maxillary IIb (Lt) excess IIb V
12.8
Bimax and genioplasty Bimax
I (both)
17.2
Bimax
1.1
C-spine fusion
4.6
Iia
V
19.6
Bimax
3.7
I
V
20.5
Bimax
1.4
Right costochondral rib graft
20.7
Bimax
4.8
III
Secondary Surgery
Surgical Movements’ Surgical Movements’ Affected Side Unaffected Side
Genioplasty
Impct + adv, setback SSO IMF, mandibular Extr+adv; nonunion adv SSO Genioplasty Extr+adv; adv SSO Genioplasty Extr+adv; before T3 adv SSO IMF Impct+adv; adv SSO V Extr+adv; adv SSO IMF, mandibular Impct+adv; implants adv SSO IMF Extr+adv; setback SSO Malar and mandibular Extr+adv; implants adv SSO Genioplasty Adv only; adv SSO
Impct+adv; adv SSO Impct+adv; lesser adv SSO Impct+adv; lesser adv SSO Impct+adv; lesser adv SSO Impct more + adv; lesser adv SSO Impct+adv; lesser adv SSO Impct more + adv; lesser adv SSO Impct+adv and SSO setback Impct+adv; lesser adv SSO Impct+adv; lesser adv SSO
Ages and follow-up are expressed as years. Adv indicates advancement; Bimax, bimaxillary surgery; Extr, extrusion; Impct, impaction; Lt, left; Rt, right; SARPE, surgically assisted rapid palatal expansion; SSO, sagittal split mandibular osteotomy; sy, syndrome.
compared with perfect symmetry (‘‘normal’’). The mean ratios were compared with normal using a 1-sample t test at each time point. Before the surgery (T1), the Z-A6 ratio deviated from perfect symmetry as expected (P = 0.002). Immediately after the surgery (T2), this asymmetry was no longer statistically significant (P = 0.33) and remained so at the long-term follow-up (T3; P = 0.59). To determine whether impaction or extrusion was a more stable movement, we compared the degree of surgical movement to the degree of relapse for each. The mean (SD) relapse after impaction was 2.11 (5.35) mm. Similarly, the mean (SD) relapse after extrusion was 1.39 (5.96) mm. A 2-sample t test was found to have no significant difference in the degree of relapse between impaction and extrusion (P = 0.756).
Mandibular Offset The mean (SD) surgical movement toward the normal side was 12.32 (8.11) mm with a mean (SD) relapse of 3.19 (9.3) mm. The net surgical gain (SD) was 10.45 (7.19) mm. Given the large standard deviation of the mean and to determine the statistical significance of these movements, a repeated-measures analysis of variance was performed using procmixed in SAS 9.3. This demonstrated that the mean surgical movement toward the midline (P = 0.0002) and net surgical gain (P = 0.0008) was significant, whereas the relapse away from the midline was not (P = 0.48). This analysis excluded the 1 patient who underwent a secondary genioplasty between T2 and T3 (Table 1, patient 4). In the group, 1 patient had a slight worsening of the occlusal cant as judged by the Z-A6 ratio and 1 patient ended up with the chin point more deviated than the initial situation; this was not clinically significant (Fig. 3).
Secondary Surgery Four patients required postoperative intermaxillary fixation (IMF) for 2 to 6 weeks. Four individuals underwent a subsequent genioplasty, and 2 patients had implants to augment the lateral mandibular body and achieve a more aesthetic mandibular border.
One patient underwent surgery for debridement of a sequestrum and treatment of a mandibular nonunion on the unaffected side (Table 1; Fig. 3).
DISCUSSION Surgical Philosophy and Stability of Results Our approach to the management of the occlusion in this patient population is based on the premises that the deformity does not worsen with age and that surgical results are most stable when performed on skeletally mature patients.8,9 Previous methods of correction have included a 2-stage approach comprising vertical ramus osteotomies at the mixed dentition stage and, subsequently, at maturity10 because of relapse. We do not believe that early surgery ‘‘unlocks the growth’’6,11 and therefore limit the number of surgeries by delaying definitive reconstruction until skeletal maturity whenever possible. As a result, we avoid early distraction because of the lack of data advocating its efficacy as an isolated treatment modality12 and limit our use of costochondral grafts to those patients who lack a ‘‘functional’’ articulation with the skull base, that is, the
FIGURE 2. Typical result after bimaxillary surgery and genioplasty (patient 6). A, Significant preoperative asymmetry is observed with an occlusal cant clearly visible in repose. B, Postoperative appearance at 4 years demonstrates corrected occlusal cant and improved facial balance. C, Incisor midline is malaligned with the left anterior open bite. D, Improved occlusal relationships with small residual left open bite.
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TABLE 2. Table of Cephalometric Data Mandibular Offset Patient No. 1 2 3 4 6 8 9 10 11 14
T1 j9.7 j12.8 j7.5 j25 j8.9 j16.1 j5.1 j14.8 j3.5 j23.9
T2 j8.7 10.6 3.5 j5.6 j0.7 j15.6 2.4 j1.7 14.5 j2.8
T3 3.1 j14.7 2.8 j7.8 j1 j13 0.8 j5.4 16.6 j4.2
T2YT1
T3YT2
1 23.4 11 19.4 8.2 0.5 7.5 13.1 18 21.1
11.8 25.3 j0.7 j2.2 j0.3 2.6 j1.6 j3.7 2.1 j1.4
T3YT1 12.8 j1.9 10.3 17.2 7.9 3.1 5.9 9.4 20.1 19.7
Affected Side Z-A6 Patient No.
T1
T2
T3
T2YT1
T3YT2
1 2 3 4 6 8 9 10 11 14
80.1 72.6 64.2 75 86.3 59 84.2 70.8 74.4 62.4
79.1 76.3 69.8 80.3 81.4 59.7 75.1 73.7 80.8 62.8
86.1 81.3 68.7 69.8 90.1 63.4 74.3 76.3 76.2 62.6
j1 3.7 5.6 5.3 j4.9 0.7 j9.1 2.9 6.4 0.4
7 5 j1.1 j10.5 8.7 3.7 j0.8 2.6 j4.6 j0.2
T2jT1
T3jT2
T3YT1 6 8.7 4.5 j5.2 3.8 4.4 j9.9 5.5 1.8 0.2
Unaffected Z-A6 Patient No.
T1
T2
T3
1 2 3 4 6 8 9 10 11 14
80.3 86.8 69.8 85.5 87.9 62.4 85.3 83.9 81.4 70
84.6 70.8 66.6 76.4 83.2 64.5 73.5 76.5 93.4 68.5
83.9 79.3 69.4 67.9 88.3 60.9 72.5 80.7 84.2 69.3
4.3 j16 j3.2 j9.1 j4.7 2.1 j11.8 j7.4 12 j1.5
j0.7 8.5 2.8 j8.5 5.1 j3.6 j1 4.2 j9.2 0.8
T3jT1 3.6 j7.5 j0.4 j17.6 0.4 j1.5 j12.8 j3.2 2.8 j0.7
Z-A6 Ratio Patient No.
T1 Ratio
T2 Ratio
T3 Ratio
$ T3 j T1 Ratio
1 2 3 4 6 8 9 10 11 14
0.998 0.836 0.92 0.877 0.982 0.946 0.987 0.844 0.914 0.891
0.935 1.078 1.048 1.051 0.978 0.926 1.02 0.96 0.865 0.917
1.026 1.025 0.99 1.028 1.02 1.041 1.025 0.945 0.905 0.903
Overcorrected Overcorrected Improvement Overcorrected Overcorrected Overcorrected Overcorrected Improvement Worsened Improvement
The values (in millimeters) at time points T1, T2, and T3 are presented with the surgical movements (as described in Fig. 1) for mandibular offset, the Z-A6 height for the affected and unaffected side, together with the Z-A6 ratio.
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of the PA cephalograms demonstrates a scoliosis of the face concave to the affected side. Thus, the original technique described by Grummons whereby the midsagittal reference passes from the crista galli and through the anterior nasal spine would result in a midline that is artificially deviated toward the affected side (Fig. 1). In this series, any asymmetry in the orbits was minimal; therefore, the Z-plane allows us to reference our measurements to an area of the craniofacial skeleton least affected in these patients. We argue that dropping a line perpendicular to the Z-plane affords a better approximation to the true midline than the midsagittal reference of Grummons. FIGURE 3. Result after bimaxillary surgery complicated by infection and mandibular nonunion (patient 2). A, Significant facial asymmetry with occlusal cant and deviation of the chin to the affected side. B, Improved occlusal appearance and facial balance, but a mild occlusal cant and deviation of the chin point remains at 21 months after the surgery. In this instance, the mandibular offset was objectively worse after the surgery than before the surgery. C, Significant right anterior open bite with otherwise good arch form and alignment. D, Improved occlusion with remaining mild right open bite.
absence of the ascending ramus and temporomandibular joint with compromised mouth opening (Fig. 4). When performing the bimaxillary surgery, we avoid the use of bone grafts (none were used in this series) on the basis of the senior author’s experience that they add to the morbidity of the procedure and that relapse is no less when they are used. No patients were placed in IMF ‘‘on table’’ to facilitate airway protection in the acute phase of postoperative edema. However, in those patients where the movements were considered large and unstable in nature or a malocclusion was developing, then a decision was made to subsequently place the patient in IMF.
Methodology We present the outcomes from a series of skeletally mature patients, on average, 3 years after undergoing orthognathic surgery to correct malocclusion and facial imbalance secondary to HFM. Because of the difficulty in quantifying outcomes, there is little in the literature examining outcomes of orthognathic surgery in this patient population. Some authors have presented quantitative results: Vargervik et al13 presented their experience with 28 patients both growing and skeletally mature. They used horizontal ramus osteotomies with bone grafting and IMF for 8 weeks to maintain occlusion and demonstrated that, in growing patients, ‘‘relapse’’ occurred as the normal side continued to grow more effectively than the operated side did. In contrast, their results in mature patients were more stable. Their assessment was based on measurements from the condylion to the geniohyoid tubercles (a composite of PA and lateral measurements) from oblique cephalograms. Such measurements are subject to parallax as a consequence of projection onto the x-ray film, and small alterations in head position may lead to larger errors. In contrast, we believe that standardized PA films are more reliable6 and are not subject to differences in apparent length. The surgical movements used to correct the deformity of HFM occur in 3 dimensions, and although linear measurements cannot accurately determine the true three-dimensional movement of the jaws, we attempted to define 2 specific parameters that most accurately reflect the changes caused by the surgery: specifically, the Z-A6 ratio that reflects occlusal cant and the mandibular offset as an expression of mandibular movement. We accept that these simply act as a proxy for the complex three-dimensional repositioning of both jaws. Our selection of the Z-plane as a reference was based on the need to use fixed skeletal points that would not be altered during the surgery. Because we are using this plane to compare differences in measurements over time, the actual distances measured from this plane to the teeth are immaterial. The use of a perpendicular line from the crista galli is the best approximation of the midline available. Careful examination
Surgical Movements Correction of occlusal cant was achieved using a combination of impaction and extrusion tailored to the patient. Such variability in the movements created large standard deviations that rendered statistical analysis demanding. By creating a ratio, a numerical expression of the occlusal cant that was statistically compared with perfect symmetry was created. By doing so, we determined that stable correction of the maxillary occlusal cant was achieved. It was noted that the mean Z-A6 height recorded at long-term follow-up was greater than that immediately after the surgery. This is explained by the fact that the occlusion continued to extrude after the surgery. Our treatment plans incorporate a degree of posterior open bite that is subsequently closed by postoperative orthodontic finishing, resulting in the increased Z-A6 height during these time points. Indeed, using our combined approach, alterations in the Z-A6 height are a result of orthognathic movement and orthodontic manipulation. This is appropriate to analyze our end point viz, occlusal cant, but not as a specific measure of maxillary movement alone. This could explain the results comparing the relapse between impaction and extrusion, where mechanical principles would suggest that an impaction should be more stable than extrusion. Alternatively, this may be a consequence of performing statistical analysis in a small group of patients.
Secondary Surgery Despite surgery at skeletal maturity, we reveal significant rates of secondary procedures required in this complex patient group, primarily to refine the facial aesthetic result after correction of the occlusion. Mandibular movements effectively corrected the chin point with minimal relapse, and in most cases, a genioplasty was built into the initial treatment plan. However, once the bimaxillary osteotomies had been completed, there was a significant amount of facial swelling, which would make the accurate positioning of an osseous genioplasty demanding. Therefore, the decision was made to defer the genioplasty
FIGURE 4. Example of buttressing the condyle. This patient has a hypoplastic ramus and condyle but with good mandibular function. A, Preoperative three-dimensional computed tomographic scan. B, Postoperative three-dimensional computed tomographic scan performed after T3 and genioplasty. The sagittal split osteotomy has allowed the condyle to be driven up against the skull base (buttressed), creating a brace against which the occlusion is supported.
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(if required) to a later date, contributing to the apparently high rate of secondary genioplasty. Two patients had custom implants to augment the mandibular border after the study period. Obwegeser14 reported the requirement of lateral onlay grafts to mask lateral hypoplasia of the mandible, and such surgery improves the lower facial balance. Although facial aesthetics were not specifically examined as part of this study, subjective assessment by the patients and the authors indicate improved appearance because the treatment protocol.
CONCLUSIONS This study determines that orthognathic surgery at skeletal maturity delivers improved occlusal outcomes in the long term as assessed by chin point deviation and occlusal cant. However, postoperative IMF and secondary surgery are more common than in other groups undertaking orthognathic surgery and this should be discussed with the patient. We advocate limiting surgery to skeletal maturity whenever possible to achieve stable long-term results while minimizing morbidity and number of procedures.
ACKNOWLEDGEMENTS The authors thank Dr Derek Stephens, MSc, PhD, from the Institute of Biostatistics, Design, and Analysis, for performing the statistical evaluation.
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3. Horgan JE, Padwa BL, LaBrie RA, et al. OMENS-Plus: analysis of craniofacial and extracraniofacial anomalies in hemifacial microsomia. Cleft Palate Craniofac J 1995;32:405Y412 4. Lefebvre A, Barclay S. Psychosocial impact of craniofacial deformities before and after reconstructive surgery. Can J Psychiatry 1982;27:579Y584 5. Munro IR, Phillips JH, Griffin G. Growth after construction of the temporomandibular joint in children with hemifacial microsomia. Cleft Palate J 1989;26:303Y311 6. Kaban LB, Mulliken JB, Murray JE. Three-dimensional approach to analysis and treatment of hemifacial microsomia. Cleft Palate J 1981;18:90Y99 7. Grummons DC, Kappeyne van de Coppello MA. A frontal asymmetry analysis. J Clin Orthod 1987;21:448Y465 8. Phillips JKB, Ross R. Hemifacial microsomia. In: Greenberg A, Prein J, eds. Craniomaxillofacial Reconstructive and Corrective Bone Surgery: Principles of Internal Fixation using AO/ASIF Technique. New York: Springer-Verlag, 2002:727Y737 9. Posnick JC. Hemifacial microsomia: evaluation and treatment. In: Posnick JC, ed. Craniofacial and Maxillofacial Surgery in Children and Young Adults. Vol. 1. Saunders, 1999:1Y14 10. Converse JM, Horowitz SL, Coccaro PJ, et al. The corrective treatment of the skeletal asymmetry in hemifacial microsomia. Plast Reconstr Surg 1973;52:221Y232 11. Kaban LB, Moses MH, Mulliken JB. Correction of hemifacial microsomia in the growing child: a follow-up study. Cleft Palate J 1986;23(suppl 1):50Y52 12. Nagy K, Kuijpers-Jagtman AM, Mommaerts MY. No evidence for long-term effectiveness of early osteodistraction in hemifacial microsomia. Plast Reconstr Surg 2009;124:2061Y2071 13. Vargervik K, Ousterhout DK, Farias M. Factors affecting long-term results in hemifacial microsomia. Cleft Palate J 1986;23(suppl 1):53Y68 14. Obwegeser HL. Correction of the skeletal anomalies of oto-mandibular dysostosis. J Maxillofac Surg 1974;2:73Y92
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Cephalometric Outcomes of Orthognathic Surgery in Hemifacial Microsomia Adel Y. Fattah, PhD, FRCS(Plast),* Camila Caro, DDS,Þ David Y. Khechoyan, MD,* Bryan Tompson, DDS, DOrth,Þ Christopher R. Forrest, MD, MSc,* and John H. Phillips, MD, FRCSC* Abstract: Hemifacial microsomia is a hypoplastic disorder of the first and second branchial arches that significantly impacts on the development of the jaws, leading to malocclusion and facial asymmetry. There is little in the literature regarding the application of orthodontic/orthognathic approaches to the correction of these deformities and the stability of the surgical results. To address this, a retrospective chart review of 10 patients with complete orthodontic records and greater than 1 year of follow-up was performed. Posteroanterior cephalograms were assessed by modified Grummons analysis to determine mandibular offset (deviation of the chin point from the skeletal midline) and occlusal cant. These measurements were performed at 3 time points (T1: preoperative, T2: immediate postoperative, T3: follow-up) to elucidate the surgical movement (T2YT1), the postoperative relapse (T3YT2), and the net gain movement (T3YT1). Maxillary movements were quantified, and the occlusal cant was expressed as a ratio between vertical heights of the maxilla at the first molar on each side. One sample t test demonstrated statistically significant surgical movement and net gain. Relapse was statistically insignificant. Repeated-measures analysis of variance demonstrated similar results for chin point position relative to the putative midline. Our results suggest that a combined orthodontic/orthognathic approach at skeletal maturity delivers improved occlusal outcomes in the long term as assessed by chin point deviation and occlusal cant, but secondary surgery rates are higher than those for orthognathic surgery in other patient groups. We advocate limiting surgery to skeletal maturity whenever possible to achieve stable long-term results while limiting morbidity and number of procedures. Key Words: Hemifacial microsomia, orthognathic, orthodontic, occlusion (J Craniofac Surg 2014;00: 00Y00)
H
emifacial microsomia (HFM; craniofacial microsomia) is a disorder causing hypoplasia of the first and second branchial
From the *The Centre for Craniofacial Care and Research, Division of Plastic Surgery, and †Division of Orthodontics, Hospital for Sick Children, Toronto, Ontario, Canada. Received January 20, 2013. Accepted for publication August 12, 2013. Address correspondence and reprint requests to Adel Y. Fattah, PhD, FRCS(Plast), The Centre for Craniofacial Care and Research, Division of Plastic Surgery, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8; E-mail: [email protected] The authors report no conflicts of interest. Copyright * 2014 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/01.SCS.0000435808.91512.58
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arch derivatives leading to facial asymmetry. It comprises a spectrum of severity ranging from preauricular skin tags and microtia to bilaterally asymmetric abnormalities of the craniofacial complex together with extracranial anomalies.1 The phenotype expresses myriad dysmorphologies neatly summarized by the OMENS classification,2,3 chief among which is the jaw hypoplasia affecting the skeletal and soft tissue components of this functional unit. This leads to diminished anteroposterior, vertical, and transverse dimensions of the face on the affected side with contralateral secondary deformities resulting in facial imbalance, asymmetric class II malocclusion with anterior open bite, an occlusal cant, and deviation of the chin to the affected side. This has ramifications for mastication as well as for speech and may significantly impact on the body image of the patient.4 As a result, surgical correction of the deformity is frequently sought. Patients with HFM presenting to the Hospital for Sick Children Centre for Craniofacial Care and Research undergo a treatment protocol that consists of a combined approach to their dentofacial difference. Patients undergo a multidisciplinary team assessment including dental, speech, orthodontic, and plastic surgical consultations. Those patients with severe mandibular hypoplasia may require a free rib graft at an early age in addition to other surgeries such as ear reconstruction. However, we have previously noted that the deformity does not increase with time,5 and we therefore aimed to perform correction at skeletal maturity whenever possible to achieve stable results. The final correction of occlusion is achieved by using a combined orthodontic/orthognathic approach, but this is often challenging because of previous surgery, poor bone stock, and soft tissue deficiency. The aims of orthognathic surgery in this population were to level the occlusal cant, to align the dental midline to that of the face, and to achieve an Angle class I occlusal relationship on a skeletal class I base. An initial phase of presurgical orthodontics is performed to decompensate the dentition in readiness for the surgical movement. Cephalometric planning and model surgery are performed in the standard fashion to generate acrylic surgical registration splints to guide the positioning of the osteotomy segments. Bimaxillary surgery (Le Fort I and bilateral sagittal split osteotomies T genioplasty) is performed and followed by postoperative orthodontics to refine the occlusal result. Objective cephalometric and outcome analysis is difficult, and there is little in the literature that examines the outcomes of orthognathic correction of occlusion in HFM. Our purpose was to retrospectively determine the cephalometric outcome of orthognathic surgery in this challenging patient group, specifically examining the stability of the surgical movement more than 1 year after surgery.
MATERIALS AND METHODS A retrospective review of all cases of HFM treated with orthognathic surgery by the senior author (J.P.) between 1993 and 2006 was performed. Both unilateral and bilateral cases were included, where the side of greater deformity was termed the affected
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side for the purpose of this analysis. Patients were included if complete posterior-anterior (PA) cephalometric and orthodontic records at 3 time points were available (T1: Presurgical, T2: immediate postsurgical, and T3: at least 1 year after surgery). Patients were excluded if they had other craniofacial abnormalities (eg, craniosynostosis or cleft lip/palate) or underwent distraction osteogenesis of the mandible. The mandibular deformity was graded according to the modified Pruzansky classification.6 In general, our institution waits until skeletal maturity to perform bimaxillary surgery comprising a Le Fort I osteotomy and bilateral sagittal split osteotomies of the mandible without bone grafting. Costochondral grafts at 5 to 7 years are used only if there is no articulation with the nascent glenoid fossa. By contrast, most cases have some putative articulation whereby the hypoplastic mandible ‘‘buttresses’’ against the skull base, and in these cases, a sagittal split osteotomy to lengthen the mandible is performed later. Lateral cephalograms cannot be used to accurately assess orthognathic movements in individuals with significant asymmetry. To determine the movement of the occlusal plane in such an individual, PA cephalograms were assessed by a modified Grummons analysis7 (Fig. 1) using the Dentofacial planning software version 7.02 (Dentofacial Research Inc, Toronto, Canada). Because the goal was to assess the movement of the Le Fort I segment and mandible relative to a fixed skeletal point, a plane was chosen, which
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connected the points on each lateral orbital rim at the inner aspect of the frontozygomatic suture; this was termed the Z-plane. At the crista galli, a perpendicular to the Z-plane was drawn and this was considered to be the putative midline. To reflect the movements of the chin relative to this midline, the mandibular offset (distance of the menton from this midline) was measured. The distance of the buccal cusp of the first maxillary molar along a perpendicular to the Z-plane was measured to determine the vertical position of the Le Fort I segment on each side. This was termed the Z-A6 height; the difference of which reflected the occlusal cant. In addition, to express the occlusal cant numerically, a ratio was determined by dividing the ZA6 height of the affected side by that of the unaffected side. These measurements were performed for each of the 3 time points to elucidate the surgical movement (T2YT1), the postoperative relapse (T3YT2), and the net gain in surgical movement (T3YT1). Statistical analyses were performed using SAS 9.3 statistical software (SAS, Toronto, Canada).
RESULTS Twenty patients with HFM who underwent orthognathic surgery were identified, of which 10 met the strict inclusion criteria (Table 1). The mean age at surgery was 17.8 years (range, 12.8Y20.9 y) and the mean length of follow-up was 3.1 years (range, 1.1Y4.75 y). In this group, 6 patients were right-sided; 2, left-sided; and 2, with bilateral cases. All patients underwent bimaxillary surgery, with 1 receiving a genioplasty as part of the primary treatment protocol (Table 1; Fig. 2). Two patients had sagittal split osteotomy on a previously placed costochondral rib graft. One patient underwent a surgically assisted rapid palatal expansion 3 years before definitive orthognathic surgery.
Surgical Movements As part of the surgical plan in all patients, the maxilla was advanced, with a mean advancement of 4.4 mm (range, 0Y7.5 mm). With regard to the affected side, in 3 patients, the maxilla was impacted asymmetrically to level the occlusion; in 6 patients, the affected side was extruded in concert with a contralateral impaction; in 1 patient, there was a minimal change to the vertical height, relying on the impaction of the unaffected side to level the occlusion. The mandibular deviation was addressed with bilateral sagittal split osteotomies using differential movements aiming to direct the chin to the median; in 8 patients, this was achieved with bilateral advancements, with the affected side being advanced to a greater degree to correct the chin deviation. On the basis of the surgical plan, the mean mandibular advancement on the affected side was 16 mm (range, 3Y24 mm), whereas the mean advancement on the unaffected side was 8 mm (range, 2Y13 mm). Of the other 2 patients, correction of deviation was accomplished using a differential setback in 1 individual and the other required advancement on the unaffected side and setback on the other because of overgrowth of the costochondral rib graft.
Occlusal Cant FIGURE 1. The modified Grummons frontal asymmetry analysis. This focuses on the occlusal cant and the chin location. Above, The Z-plane is the fixed skeletal reference plane from which the measurements are derived. From this plane, a perpendicular is dropped from the crista galli. This constitutes the sagittal reference plane from which the distance to the menton is measured; this is termed the mandibular offset. On each side, the Z-A6 height is measured from the buccal cusp of the first maxillary molar along a perpendicular to the Z-plane. A ratio of the 2 heights reflects the occlusal cant. Below, Time points at which analysis was performed to determine the surgical movement, relapse, and net gain from surgical repositioning. T1: preoperative, T2: immediate postoperative, T3: follow-up of more than 1 year.
2
The mean (SD) surgical movement (Table 2) on the affected side was 1.04 (4.93) mm of extrusion coupled with 3.53 (8.23) mm of mean impaction of the unaffected side. The mean (SD) net extrusion at follow-up was 1.98 (5.63) mm on the affected side and the mean (SD) net impaction of the unaffected side was 3.69 (6.89) mm. The wide values for the standard deviation reflect that each side was impacted or extruded to achieve leveling of the occlusal cant while simultaneously correcting facial height. Therefore, an alternative method to express the occlusal cant would be to calculate a ratio of the Z-A6 heights of the affected to unaffected sides. By doing so, a mathematical expression of the occlusal cant (Z-A6 ratio) can be obtained and statistically * 2014 Mutaz B. Habal, MD
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TABLE 1. Patient Demographics, Surgical Movements, and Secondary Surgery Patient No. 1 2 3 4 6 8 9 10 11 14
Diagnosis Goldenhar sy (left) Left hemifacial microsomia Right hemifacial microsomia Right hemifacial microsomia Bilateral HFM (Rt 9 Lt) Right hemifacial microsomia Goldenhar sy (Rt 9 Lt) Right hemifacial microsomia Right hemifacial microsomia Right hemifacial microsomia
Prusansky Previous Surgery Age at Class /Other Comorbidity Surgery III
Left costochondral graft and SSO V
IIb
V
IIb IIb
SARPE
Procedure
Follow-up
18.3
Bimax
3.3
17.3
Bimax
1.8
13.6
Bimax
3.3
20.9
Bimax
2.7
17.7
4.1
III (Rt) Vertical maxillary IIb (Lt) excess IIb V
12.8
Bimax and genioplasty Bimax
I (both)
17.2
Bimax
1.1
C-spine fusion
4.6
Iia
V
19.6
Bimax
3.7
I
V
20.5
Bimax
1.4
Right costochondral rib graft
20.7
Bimax
4.8
III
Secondary Surgery
Surgical Movements’ Surgical Movements’ Affected Side Unaffected Side
Genioplasty
Impct + adv, setback SSO IMF, mandibular Extr+adv; nonunion adv SSO Genioplasty Extr+adv; adv SSO Genioplasty Extr+adv; before T3 adv SSO IMF Impct+adv; adv SSO V Extr+adv; adv SSO IMF, mandibular Impct+adv; implants adv SSO IMF Extr+adv; setback SSO Malar and mandibular Extr+adv; implants adv SSO Genioplasty Adv only; adv SSO
Impct+adv; adv SSO Impct+adv; lesser adv SSO Impct+adv; lesser adv SSO Impct+adv; lesser adv SSO Impct more + adv; lesser adv SSO Impct+adv; lesser adv SSO Impct more + adv; lesser adv SSO Impct+adv and SSO setback Impct+adv; lesser adv SSO Impct+adv; lesser adv SSO
Ages and follow-up are expressed as years. Adv indicates advancement; Bimax, bimaxillary surgery; Extr, extrusion; Impct, impaction; Lt, left; Rt, right; SARPE, surgically assisted rapid palatal expansion; SSO, sagittal split mandibular osteotomy; sy, syndrome.
compared with perfect symmetry (‘‘normal’’). The mean ratios were compared with normal using a 1-sample t test at each time point. Before the surgery (T1), the Z-A6 ratio deviated from perfect symmetry as expected (P = 0.002). Immediately after the surgery (T2), this asymmetry was no longer statistically significant (P = 0.33) and remained so at the long-term follow-up (T3; P = 0.59). To determine whether impaction or extrusion was a more stable movement, we compared the degree of surgical movement to the degree of relapse for each. The mean (SD) relapse after impaction was 2.11 (5.35) mm. Similarly, the mean (SD) relapse after extrusion was 1.39 (5.96) mm. A 2-sample t test was found to have no significant difference in the degree of relapse between impaction and extrusion (P = 0.756).
Mandibular Offset The mean (SD) surgical movement toward the normal side was 12.32 (8.11) mm with a mean (SD) relapse of 3.19 (9.3) mm. The net surgical gain (SD) was 10.45 (7.19) mm. Given the large standard deviation of the mean and to determine the statistical significance of these movements, a repeated-measures analysis of variance was performed using procmixed in SAS 9.3. This demonstrated that the mean surgical movement toward the midline (P = 0.0002) and net surgical gain (P = 0.0008) was significant, whereas the relapse away from the midline was not (P = 0.48). This analysis excluded the 1 patient who underwent a secondary genioplasty between T2 and T3 (Table 1, patient 4). In the group, 1 patient had a slight worsening of the occlusal cant as judged by the Z-A6 ratio and 1 patient ended up with the chin point more deviated than the initial situation; this was not clinically significant (Fig. 3).
Secondary Surgery Four patients required postoperative intermaxillary fixation (IMF) for 2 to 6 weeks. Four individuals underwent a subsequent genioplasty, and 2 patients had implants to augment the lateral mandibular body and achieve a more aesthetic mandibular border.
One patient underwent surgery for debridement of a sequestrum and treatment of a mandibular nonunion on the unaffected side (Table 1; Fig. 3).
DISCUSSION Surgical Philosophy and Stability of Results Our approach to the management of the occlusion in this patient population is based on the premises that the deformity does not worsen with age and that surgical results are most stable when performed on skeletally mature patients.8,9 Previous methods of correction have included a 2-stage approach comprising vertical ramus osteotomies at the mixed dentition stage and, subsequently, at maturity10 because of relapse. We do not believe that early surgery ‘‘unlocks the growth’’6,11 and therefore limit the number of surgeries by delaying definitive reconstruction until skeletal maturity whenever possible. As a result, we avoid early distraction because of the lack of data advocating its efficacy as an isolated treatment modality12 and limit our use of costochondral grafts to those patients who lack a ‘‘functional’’ articulation with the skull base, that is, the
FIGURE 2. Typical result after bimaxillary surgery and genioplasty (patient 6). A, Significant preoperative asymmetry is observed with an occlusal cant clearly visible in repose. B, Postoperative appearance at 4 years demonstrates corrected occlusal cant and improved facial balance. C, Incisor midline is malaligned with the left anterior open bite. D, Improved occlusal relationships with small residual left open bite.
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TABLE 2. Table of Cephalometric Data Mandibular Offset Patient No. 1 2 3 4 6 8 9 10 11 14
T1 j9.7 j12.8 j7.5 j25 j8.9 j16.1 j5.1 j14.8 j3.5 j23.9
T2 j8.7 10.6 3.5 j5.6 j0.7 j15.6 2.4 j1.7 14.5 j2.8
T3 3.1 j14.7 2.8 j7.8 j1 j13 0.8 j5.4 16.6 j4.2
T2YT1
T3YT2
1 23.4 11 19.4 8.2 0.5 7.5 13.1 18 21.1
11.8 25.3 j0.7 j2.2 j0.3 2.6 j1.6 j3.7 2.1 j1.4
T3YT1 12.8 j1.9 10.3 17.2 7.9 3.1 5.9 9.4 20.1 19.7
Affected Side Z-A6 Patient No.
T1
T2
T3
T2YT1
T3YT2
1 2 3 4 6 8 9 10 11 14
80.1 72.6 64.2 75 86.3 59 84.2 70.8 74.4 62.4
79.1 76.3 69.8 80.3 81.4 59.7 75.1 73.7 80.8 62.8
86.1 81.3 68.7 69.8 90.1 63.4 74.3 76.3 76.2 62.6
j1 3.7 5.6 5.3 j4.9 0.7 j9.1 2.9 6.4 0.4
7 5 j1.1 j10.5 8.7 3.7 j0.8 2.6 j4.6 j0.2
T2jT1
T3jT2
T3YT1 6 8.7 4.5 j5.2 3.8 4.4 j9.9 5.5 1.8 0.2
Unaffected Z-A6 Patient No.
T1
T2
T3
1 2 3 4 6 8 9 10 11 14
80.3 86.8 69.8 85.5 87.9 62.4 85.3 83.9 81.4 70
84.6 70.8 66.6 76.4 83.2 64.5 73.5 76.5 93.4 68.5
83.9 79.3 69.4 67.9 88.3 60.9 72.5 80.7 84.2 69.3
4.3 j16 j3.2 j9.1 j4.7 2.1 j11.8 j7.4 12 j1.5
j0.7 8.5 2.8 j8.5 5.1 j3.6 j1 4.2 j9.2 0.8
T3jT1 3.6 j7.5 j0.4 j17.6 0.4 j1.5 j12.8 j3.2 2.8 j0.7
Z-A6 Ratio Patient No.
T1 Ratio
T2 Ratio
T3 Ratio
$ T3 j T1 Ratio
1 2 3 4 6 8 9 10 11 14
0.998 0.836 0.92 0.877 0.982 0.946 0.987 0.844 0.914 0.891
0.935 1.078 1.048 1.051 0.978 0.926 1.02 0.96 0.865 0.917
1.026 1.025 0.99 1.028 1.02 1.041 1.025 0.945 0.905 0.903
Overcorrected Overcorrected Improvement Overcorrected Overcorrected Overcorrected Overcorrected Improvement Worsened Improvement
The values (in millimeters) at time points T1, T2, and T3 are presented with the surgical movements (as described in Fig. 1) for mandibular offset, the Z-A6 height for the affected and unaffected side, together with the Z-A6 ratio.
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of the PA cephalograms demonstrates a scoliosis of the face concave to the affected side. Thus, the original technique described by Grummons whereby the midsagittal reference passes from the crista galli and through the anterior nasal spine would result in a midline that is artificially deviated toward the affected side (Fig. 1). In this series, any asymmetry in the orbits was minimal; therefore, the Z-plane allows us to reference our measurements to an area of the craniofacial skeleton least affected in these patients. We argue that dropping a line perpendicular to the Z-plane affords a better approximation to the true midline than the midsagittal reference of Grummons. FIGURE 3. Result after bimaxillary surgery complicated by infection and mandibular nonunion (patient 2). A, Significant facial asymmetry with occlusal cant and deviation of the chin to the affected side. B, Improved occlusal appearance and facial balance, but a mild occlusal cant and deviation of the chin point remains at 21 months after the surgery. In this instance, the mandibular offset was objectively worse after the surgery than before the surgery. C, Significant right anterior open bite with otherwise good arch form and alignment. D, Improved occlusion with remaining mild right open bite.
absence of the ascending ramus and temporomandibular joint with compromised mouth opening (Fig. 4). When performing the bimaxillary surgery, we avoid the use of bone grafts (none were used in this series) on the basis of the senior author’s experience that they add to the morbidity of the procedure and that relapse is no less when they are used. No patients were placed in IMF ‘‘on table’’ to facilitate airway protection in the acute phase of postoperative edema. However, in those patients where the movements were considered large and unstable in nature or a malocclusion was developing, then a decision was made to subsequently place the patient in IMF.
Methodology We present the outcomes from a series of skeletally mature patients, on average, 3 years after undergoing orthognathic surgery to correct malocclusion and facial imbalance secondary to HFM. Because of the difficulty in quantifying outcomes, there is little in the literature examining outcomes of orthognathic surgery in this patient population. Some authors have presented quantitative results: Vargervik et al13 presented their experience with 28 patients both growing and skeletally mature. They used horizontal ramus osteotomies with bone grafting and IMF for 8 weeks to maintain occlusion and demonstrated that, in growing patients, ‘‘relapse’’ occurred as the normal side continued to grow more effectively than the operated side did. In contrast, their results in mature patients were more stable. Their assessment was based on measurements from the condylion to the geniohyoid tubercles (a composite of PA and lateral measurements) from oblique cephalograms. Such measurements are subject to parallax as a consequence of projection onto the x-ray film, and small alterations in head position may lead to larger errors. In contrast, we believe that standardized PA films are more reliable6 and are not subject to differences in apparent length. The surgical movements used to correct the deformity of HFM occur in 3 dimensions, and although linear measurements cannot accurately determine the true three-dimensional movement of the jaws, we attempted to define 2 specific parameters that most accurately reflect the changes caused by the surgery: specifically, the Z-A6 ratio that reflects occlusal cant and the mandibular offset as an expression of mandibular movement. We accept that these simply act as a proxy for the complex three-dimensional repositioning of both jaws. Our selection of the Z-plane as a reference was based on the need to use fixed skeletal points that would not be altered during the surgery. Because we are using this plane to compare differences in measurements over time, the actual distances measured from this plane to the teeth are immaterial. The use of a perpendicular line from the crista galli is the best approximation of the midline available. Careful examination
Surgical Movements Correction of occlusal cant was achieved using a combination of impaction and extrusion tailored to the patient. Such variability in the movements created large standard deviations that rendered statistical analysis demanding. By creating a ratio, a numerical expression of the occlusal cant that was statistically compared with perfect symmetry was created. By doing so, we determined that stable correction of the maxillary occlusal cant was achieved. It was noted that the mean Z-A6 height recorded at long-term follow-up was greater than that immediately after the surgery. This is explained by the fact that the occlusion continued to extrude after the surgery. Our treatment plans incorporate a degree of posterior open bite that is subsequently closed by postoperative orthodontic finishing, resulting in the increased Z-A6 height during these time points. Indeed, using our combined approach, alterations in the Z-A6 height are a result of orthognathic movement and orthodontic manipulation. This is appropriate to analyze our end point viz, occlusal cant, but not as a specific measure of maxillary movement alone. This could explain the results comparing the relapse between impaction and extrusion, where mechanical principles would suggest that an impaction should be more stable than extrusion. Alternatively, this may be a consequence of performing statistical analysis in a small group of patients.
Secondary Surgery Despite surgery at skeletal maturity, we reveal significant rates of secondary procedures required in this complex patient group, primarily to refine the facial aesthetic result after correction of the occlusion. Mandibular movements effectively corrected the chin point with minimal relapse, and in most cases, a genioplasty was built into the initial treatment plan. However, once the bimaxillary osteotomies had been completed, there was a significant amount of facial swelling, which would make the accurate positioning of an osseous genioplasty demanding. Therefore, the decision was made to defer the genioplasty
FIGURE 4. Example of buttressing the condyle. This patient has a hypoplastic ramus and condyle but with good mandibular function. A, Preoperative three-dimensional computed tomographic scan. B, Postoperative three-dimensional computed tomographic scan performed after T3 and genioplasty. The sagittal split osteotomy has allowed the condyle to be driven up against the skull base (buttressed), creating a brace against which the occlusion is supported.
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(if required) to a later date, contributing to the apparently high rate of secondary genioplasty. Two patients had custom implants to augment the mandibular border after the study period. Obwegeser14 reported the requirement of lateral onlay grafts to mask lateral hypoplasia of the mandible, and such surgery improves the lower facial balance. Although facial aesthetics were not specifically examined as part of this study, subjective assessment by the patients and the authors indicate improved appearance because the treatment protocol.
CONCLUSIONS This study determines that orthognathic surgery at skeletal maturity delivers improved occlusal outcomes in the long term as assessed by chin point deviation and occlusal cant. However, postoperative IMF and secondary surgery are more common than in other groups undertaking orthognathic surgery and this should be discussed with the patient. We advocate limiting surgery to skeletal maturity whenever possible to achieve stable long-term results while minimizing morbidity and number of procedures.
ACKNOWLEDGEMENTS The authors thank Dr Derek Stephens, MSc, PhD, from the Institute of Biostatistics, Design, and Analysis, for performing the statistical evaluation.
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3. Horgan JE, Padwa BL, LaBrie RA, et al. OMENS-Plus: analysis of craniofacial and extracraniofacial anomalies in hemifacial microsomia. Cleft Palate Craniofac J 1995;32:405Y412 4. Lefebvre A, Barclay S. Psychosocial impact of craniofacial deformities before and after reconstructive surgery. Can J Psychiatry 1982;27:579Y584 5. Munro IR, Phillips JH, Griffin G. Growth after construction of the temporomandibular joint in children with hemifacial microsomia. Cleft Palate J 1989;26:303Y311 6. Kaban LB, Mulliken JB, Murray JE. Three-dimensional approach to analysis and treatment of hemifacial microsomia. Cleft Palate J 1981;18:90Y99 7. Grummons DC, Kappeyne van de Coppello MA. A frontal asymmetry analysis. J Clin Orthod 1987;21:448Y465 8. Phillips JKB, Ross R. Hemifacial microsomia. In: Greenberg A, Prein J, eds. Craniomaxillofacial Reconstructive and Corrective Bone Surgery: Principles of Internal Fixation using AO/ASIF Technique. New York: Springer-Verlag, 2002:727Y737 9. Posnick JC. Hemifacial microsomia: evaluation and treatment. In: Posnick JC, ed. Craniofacial and Maxillofacial Surgery in Children and Young Adults. Vol. 1. Saunders, 1999:1Y14 10. Converse JM, Horowitz SL, Coccaro PJ, et al. The corrective treatment of the skeletal asymmetry in hemifacial microsomia. Plast Reconstr Surg 1973;52:221Y232 11. Kaban LB, Moses MH, Mulliken JB. Correction of hemifacial microsomia in the growing child: a follow-up study. Cleft Palate J 1986;23(suppl 1):50Y52 12. Nagy K, Kuijpers-Jagtman AM, Mommaerts MY. No evidence for long-term effectiveness of early osteodistraction in hemifacial microsomia. Plast Reconstr Surg 2009;124:2061Y2071 13. Vargervik K, Ousterhout DK, Farias M. Factors affecting long-term results in hemifacial microsomia. Cleft Palate J 1986;23(suppl 1):53Y68 14. Obwegeser HL. Correction of the skeletal anomalies of oto-mandibular dysostosis. J Maxillofac Surg 1974;2:73Y92
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