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Cleft maxillary distraction versus orthognathic surgery—which one is more stable in 5 years?
Vol. 109 No. 6 June 2010
ORAL AND MAXILLOFACIAL SURGERY
Editor: James R. Hupp
Cleft maxillary distraction versus orthognathic surgery—which one is more stable in 5 years? Hannah Daile P. Chua, DDM, MA, MDS, PhD,a Margareta Bendeus Hägg, DDS, FHKAM (DS), FCDSHK (Orthod),b and Lim Kwong Cheung, BDS, FRACDS (OMS), PhD,c Hong Kong SAR, China THE UNIVERSITY OF HONG KONG
Objective. The objective of this study was to compare the long-term stability of distraction osteogenesis (DO) and conventional orthognathic surgery (CO) in patients with cleft lip and palate (CLP). Study design. CLP patients requiring maxillary advancement of 4 to 10 mm were randomized and assigned to either CO or DO. In the CO group, the maxilla was fully mobilized to the preplanned position and fixed using titanium miniplates. In the DO group, the maxilla was mobilized to a limited extent and distractors were fixed on each side of the maxilla. Serial lateral cephalographs were taken for the assessment of stability at different postoperative periods up to 5 years. Results. In the CO group, the maxilla relapsed backward and upward, whereas in the DO group, it advanced more forward and downward over 5 years. Conclusions. Distraction of the cleft maxilla can achieve better long-term skeletal stability in maintaining its advanced position than CO. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;109:803-814)
Patients with cleft lip and palate (CLP) usually present with depressed midface and narrow maxillary dental arch as a result of dentofacial anomaly, combined with scar tissue from the early surgical repair of CLP.1 Many of these cases require combined orthodontic and orthognathic surgery to correct the dentofacial deformity.2 The aim of treatment is to align the teeth in the alveolar process followed by advancement of the maxilla to a normal position in relation to the cranium. Numerous studies have been made about the longterm stability of maxillary advancement with a Le Fort This clinical study was supported by the Competitive Earmarked Research Grant from the Hong Kong Research Grant Council (Reference code: HKU 7577/05M). a Post-doctoral fellow, Discipline of Oral & Maxillofacial Surgery, Faculty of Dentistry, The University of Hong Kong, China. b Part-time lecturer, Discipline of Orthodontics, Faculty of Dentistry, The University of Hong Kong, China. c Chair Professor, Discipline of Oral and Maxillofacial Surgery, Faculty of Dentistry, The University of Hong Kong, China. Received for publication Jul 21, 2009; returned for revision Oct 5, 2009; accepted for publication Oct 21, 2009. 1079-2104/$ - see front matter © 2010 Mosby, Inc. All rights reserved. doi:10.1016/j.tripleo.2009.10.056
I osteotomy.3 The amount of relapse in noncleft patients with maxillary hypoplasia has been reported to be around 10%.4 In patients with CLP, the relapse rates are much higher, ranging from 25% up to 50%.3 Distraction osteogenesis has opened a new perspective for the treatment of various skeletal anomalies, particularly for the patient with CLP. Our center has published the first randomized, controlled trial in comparing the clinical morbidities and skeletal relapse of patients with CLP receiving either distraction osteogenesis (DO) or conventional orthognathic surgery (CO).5 The results of our study showed that there were no major differences in the clinical morbidities between CO and DO groups. However, DO provided better skeletal stability, whereas there was a significant amount of skeletal relapse in the first 12 weeks following CO. To our knowledge, there is no randomized controlled trial evaluating the long-term stability of CO and DO in patients with CLP reaching 5 years. The aim of this study was to compare the long-term stability of maxillary Le Fort I advancement in patients with CLP by either distraction with internal distractors or immediate transposition with titanium plate fixation. 803
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MATERIAL AND METHODS Patient selection Eligible subjects were selected from patients with CLP needing Le Fort I osteotomy for correction of maxillary retrusion with moderate severity. For inclusion, patients had to be aged 16 or older and with complete bony fusion of the radial epiphysis confirmed by hand-wrist radiographs. The maxillary alveolar clefts had to have been grafted and each patient had undergone presurgical arch alignment and dental decompensation by fixed orthodontics at the University Cleft Lip and Palate Center. All patients underwent a standard surgical assessment, dental model surgery, and prediction tracing. Patients who required maxillary advancement ranging from 4 to 10 mm based on the model surgery movement measured from the upper incisal tip were included in the study. Syndromic patients and those who presented with systemic diseases were excluded. Patients who required maxillary advancement of more than 10 mm were treated by DO, whereas those who needed advancement of less than 4 mm were treated by CO. These latter 2 groups were excluded from the study. Patients who satisfied the inclusion criteria were randomly assigned to 2 surgical groups for treatment by distraction with internal maxillary distractors or by conventional orthognathic surgery with miniplate fixation, respectively. A senior investigator (L.K.C.) with extensive experience in both distraction and orthognathic surgery performed the clinical assessment and was in charge of the randomization of the patients by using a table of random numbers generated from a computer. The study was approved by the Faculty Ethics Committee and all the patients involved in the study provided written consent. The surgery was carried out between June 2002 and January 2008 in the Discipline of Oral and Maxillofacial Surgery, Faculty of Dentistry. Surgical technique A continuous maxillary incision 5 mm above the mucogingival margin from the right first molar to the left first molar was made. The buccal tissue was reflected to expose the bony alveolus and zygoma. The buccal osteotomy was completed anteriorly from the pyriform rim to reach the pterygomaxillary junction posteriorly. The nasal septum was transected at its base by a septal osteotome. Any maxillary impacted wisdom tooth was elevated and the tuberosities of both sides were osteotomized by a wedge osteotome.6 The maxillae were downfractured with finger pressure and the maxilla was fully mobilized. The maxillary sinus walls and nasal septum were then excised according to the model surgery. Maxillary segmentalization was per-
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formed in both groups, if necessary, according to the dental model surgical plan. In the CO group, the maxilla was mobilized fully with the use of a pterygoid osteotome and transposed to the preplanned position with little tension guided by a custom-made occlusal wafer. The arch bars were ligated to both the maxillary and mandibular dental arches. The teeth were placed in the occlusal wafer to determine the anteroposterior (AP) movement and then placed together in intermaxillary fixation (IMF). The maxillary vertical markings were checked to ensure vertical movement made according to the dental model surgery. The mobilized maxilla was fixed with 2 titanium miniplates on each side at the zygomatic buttress and the pyriform region. Sheets of bone grafts harvested from the medial nasal walls or septum were used to cover any bony gaps in the lateral maxillary walls and in the segmentalized osteotomy gaps. IMF and the occlusal wafer were removed, and the accuracy of the dental interdigitation was checked. A standardized technique of maxillary distraction with the use of internal distractors was developed for the DO group. A similar vestibular incision to the orthognathic surgical exposure was made. The buccal tissue was reflected to expose the bony alveolus and zygoma. An internal bone-borne maxillary distractor (Synthes, West Chester, PA) was bent and adapted to the contour of the maxillary alveolus and zygomatic buttress. The planned buccal cut of the Le Fort I osteotomy was marked out to ensure clearance from between the 2 distractor footplates. Thereafter, the distractors were removed and a similar osteotomy procedure to that of the orthognathic surgery group was performed. In distraction, the maxilla was also fully mobilized, but not transposed to the final occlusal position. The maxillary occlusal plane was oriented according to the vertical markings established at model surgery and any bony interference was removed. In cases where segmentalization of the maxilla was performed, the segments were bridged with titanium miniplates and screws. The distractors were then reinserted in their predetermined positions. The distractor body on either side was made parallel to the wire orientation in the vector guidance splint.7 Once the distractors were fixed in their 3-dimensional orientation, IMF was cut and the vector guidance splint removed. The distractors on either side were activated for a few millimeters to check the correctness of maxillary transport and then rewound back to good bone contact position. The mucosal wound was then closed by continuous suturing to leave the activator rod external to the mucosal wound for later activation. To improve the accuracy of measurement of maxillary movement and relapse, 2 additional 1.0-mm tita-
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nium microscrews (Synthes) were inserted in both groups. One microscrew was placed at the most concave part of the anterior maxilla at the midline (Apoint) and another was fixed at the posterior maxilla above the mesial root of the first molar (P-point). Mandibular osteotomies were performed in the same surgery, if needed, according to the skeletal diagnosis (e.g., mandibular dentoalveolar protrusion in AP direction, mandibular protrusion in AP direction, asymmetric mandibular protrusion in AP direction). After a latency of 3 days, activation was commenced at 1 mm per day in 2 rhythms with an activating key by the patients themselves or their relatives until a class I incisal relationship was achieved. Light orthodontic elastic was applied to control the occlusion in both groups during the early postoperative period. The distractors were removed after the third postoperative month. The patients were reviewed at regular postoperative intervals of 2 and 8 weeks; 3 and 6 months; and 1, 2, 3, 4, and 5 years. Lateral cephalometric assessment Standardized lateral cephalographs were taken on all patients enrolled in this study both shortly before the operation and postoperatively at 2 and 8 weeks; 3 and 6 months; and 1, 2, 3, 4, and 5 years. All the lateral cephalographs were taken using the same orthopantomograph machine (Philips Orthoralix SD, Monza, Italy) with the patients in natural head position and centric occlusion with the lips in repose. The method of analysis was a modification advocated by Cheung et al.8 A horizontal (X) reference line was constructed at 7 degrees from a linear line connecting the sella (S) and nasion (N) points (SN line). The vertical (Y) reference line was a line drawn perpendicular to the horizontal reference line passing through the sella. The lateral cephalographs were traced on high-quality matte acetate overlay sheets (Orthotrace, Rocky Mountain Orthodontics Inc., Denver, CO) to provide details of the soft- and hard-tissue landmarks. All tracings were superimposed using the sella, nasion, and cranial base structures using a method of anatomic best fit. The linear movements of the landmarks were measured using an electronic digital caliper (Digit Cal, Tesa, Switzerland) with accuracy up to 2 decimal points. For the angular changes, a college protractor (Staedtler Inc., Chatsworth, CA) was used. Each reading was taken 3 times and a mean value was recorded. Stability assessment Changes in the stability of the maxilla were based on the movement of the microscrew at A-point and P-point
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S
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Fig. 1. Reference lines and landmarks used for the cephalometric analysis of maxillary stability. S, sella; N, nasion; A, subspinale A-point; P, micro-screw above the mesial root of the upper 1st molar.
in horizontal and vertical planes in relation to the X and Y reference lines, respectively. The intersecting angle formed between the central axes of the maxillary central incisor to the SN line was also measured to determine any changes of the incisal angulation in both treatment groups (Fig. 1). The time between the postoperative intervals of 2 to 8 weeks was assigned as T1, 8 to 12 weeks as T2, 3 to 6 months as T3, 6 to 12 months as T4, 1 to 2 years as T5, 2 to 3 years as T6, 3 to 4 years as T7, and 4 to 5 years as T8. The stability results were compared between the DO and CO group by Student 2-sample t test and the threshold of significance was set at P less than .05. Error analysis on lateral cephalograph measurements The errors of cephalometric readings were calculated based on the measurements of 40 lateral cephalographs randomly selected from 20 patients. Landmark identification of the hard- and soft-tissue points was made and the points were digitized. The same measurement was repeated 1 week later. Reliability and random error analyses on the 2 sets of measurements were performed. The reliability of the measurements was eval-
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Fig. 2. Clinical changes of a 23-year-old female with unilateral CLP who underwent conventional orthognathic surgery. Preoperative: a, frontal view showed incompetent lips and flaring of left ala; b, lateral view showed severe retrusion of the maxilla and protrusion of the mandible with eversion of the lower lip; c, lateral cephalograph confirmed retrusion of the maxilla and protrusion of the mandible; d, intraoral view showed class III malocclusion and e, negative overjet. Postoperative 6 months:
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uated by paired t test with a 5% level of significance (SPSS Inc., Chicago, IL). The reproducibility of random error is important because it determines the metric differences between the 2 measurements and the acceptability of the differences. Dahlberg’s formula9 was used to determine the random error. RE ⫽
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兺 d2 2n
RE ⫽ Random error n ⫽ sample size d ⫽ difference between the 2 measurements
To determine whether there is any significant error in measuring the surgical changes between 2 postoperative time points, which form the basis of comparison between the treatment groups, the postoperative lateral cephalographs (postoperative 3 and 6 months) of 10 randomly selected patients were also chosen. The mean differences in the surgical stability of the maxilla were recorded. The same measurement was repeated 1 week later. The reliability analysis using paired t tests confirmed no significant difference between 2 tracings carried out at separate occasions in both landmark identification and surgical movement changes. The random error analysis confirmed a small metric difference in measurements, but it was within the clinically acceptable limit of 1.0 mm. RESULTS Twenty-two of the 47 patients who participated in the study underwent distraction with internal maxillary distractors, whereas the other 25 had conventional orthognathic surgery. Typical cases of CO and DO with follow-up of 5 years are illustrated in Fig. 2 and Fig. 3, respectively. Based on the planned model surgery movement measured from the upper incisal tip, the mean maxillary advancement for the DO group was 6.59 mm, with a standard deviation (SD) of 1.93. For the CO group, the maxilla was advanced a mean of 6.46 mm, with an SD of 1.60. There was no statistically significant difference in the surgical movement between the 2 groups (P ⫽ .82). In the CO group, 24 patients had double-jaw surgery and 1 had surgery on the maxilla only. Segmentalization of the Le Fort I maxilla was performed in 13 of the 25 cases. There was no statistically significant difference between patients who had double-jaw surgery
and those who had single-jaw surgery (P ⫽ .73). In addition, there was no statistically significant difference between the patients who had segmentalization and nonsegmentalization of the Le Fort I osteotomy (P ⫽ .68). In the DO group, 17 patients had double-jaw surgery and 1 had single-jaw surgery. Segmentalization of the Le Fort I maxilla was performed in 4 cases. We also did not find any statistically significant difference between patients who had double-jaw surgery and those who had single-jaw surgery (P ⫽ .70). With regard to the segmentalized maxilla, there was no significant difference between the patients who had segmentalization and nonsegmentalization (P ⫽ .84). To determine the horizontal and vertical movements achieved during the surgery, a superimposition of the lateral cephalographs taken preoperatively and at 2 weeks postoperatively were performed. Because there was no radiographic marker found on the preoperative lateral cephalographs, the method of anatomic best fit of the maxilla was used to transfer the position of both microscrews found on the postoperative lateral cephalographs to the preoperative lateral cephalographs. The changes in the horizontal and vertical movements of both microscrews in relation to the horizontal and vertical reference lines of the lateral cephalographs were then recorded and analyzed. The mean horizontal movement of A-point (advancement) in the DO and CO groups was found to be 7.04 mm and 6.84 mm with SDs of 1.70 and 1.77, respectively. The mean horizontal movement of P-point (advancement) in the DO and CO groups was 7.07 mm and 6.91 mm, with SDs of 1.68 and 1.89. The mean vertical movement of A-point and P-point in the CO group was 1.16 mm (SD ⫽ 2.33) and 0.88 mm (SD ⫽ 1.91); for the DO group, the movements were 1.31 mm (SD ⫽ 2.98) and 0.88 mm (SD⫽ 2.74). Independent t tests revealed that there were no statistically significant differences between the mean advancement of the maxilla based on the model surgery and horizontal movement of A-point measured from the lateral cephalographs in both groups (DO group: P ⫽ .43; CO group: P ⫽ .27). Skeletal stability Horizontal changes. The horizontal and vertical movements of both A- and P-points in the DO and CO groups at each time period were compared. The statisti-
f, frontal view showed a balanced face; g, improvement of the facial profile and lip contour; h, lateral cephalograph showed the advanced maxilla fixed with titanium internal fixation; i, postoperative class I and j, positive overjet. Postoperative 5 years: k-o, stable facial esthetics and occlusal outcome comparable to postoperative 6 months.
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Fig. 3. Clinical changes of a 24-year-old male with bilateral CLP who underwent distraction osteogenesis with intraoral maxillary distracters. Preoperative: a, preoperative views showed incompetent lips; b, retrusion of the maxilla, protrusion of the mandible, and severe lower lip protrusion; c, lateral view showed severe retrusion of the maxilla and protrusion of the mandible; d, oral views showed negative overjet and e, class III malocclusion and presence of anterior open bite. Postoperative 3 months: f, postoperative
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Table I. The mean horizontal A-point changes of the cleft maxilla by distraction osteogenesis and orthognathic surgery based on serial cephalometric analyses Changes in the horizontal movement of A-point Postoperative period 2-8 weeks (T1) (n) DO ⫽ 22, CO ⫽ 25 8-12 weeks (T2) (n) DO ⫽ 21, CO ⫽ 25 3-6 months (T3) (n) DO ⫽ 21, CO ⫽ 25 6-12 months (T4) (n) DO ⫽ 20, CO ⫽ 24 1-2 years (T5) (n) DO ⫽ 18, CO ⫽ 21 2-3 years (T6) (n) DO ⫽ 17, CO ⫽ 17 3-4 years (T7) (n) DO ⫽ 15, CO ⫽ 12 4-5 years (T8) (n) DO ⫽ 7, CO ⫽ 9 Total backward (⫺) movement Total forward (⫹) movement
Distraction osteogenesis ⴙ 1.53 mm (1.21) ⴙ 0.76 mm (1.04) ⫹ 0.10 mm (0.71) ⴙ 0.06 mm (0.39) ⫹ 0.03 mm (0.75) ⫺ 0.58 mm (0.44) ⴙ 0.28 mm (0.33) ⫹ 0.09 mm (0.13) 0.58 2.85
ⴙ 21.73% ⴙ 10.79% ⫹ 1.42% ⴙ 0.85% ⫹ 0.43% ⫺ 8.24% ⴙ 3.98% ⫹ 1.28% 8.24% 40.48%
Orthognathic surgery ⴚ 0.48 mm (0.35) ⴚ 0.32 mm (1.22) ⫺ 0.19 mm (0.87) ⴚ 0.52 mm (0.60) ⫺ 0.06 mm (0.60) ⫺ 0.40 mm (0.70) ⴚ 0.16 mm (0.23) ⫺ 0.40 mm (0.57) 2.53 —
ⴚ 7.02% ⴚ 4.68% ⫺ 2.78% ⴚ 7.60% ⫺ 0.88% ⫺ 5.85% ⴚ 2.34% ⫺ 5.85% 31.0% —
P value .0001* .007* .273 .002* .701 .538 .039* .352
Values in parentheses are standard deviations. Percentages were computed based on the mean horizontal movement of A-point DO (7.04 mm), CO (6.84 mm). The dashes in the orthognathic surgery percent row mean that there is a backward movement of the maxilla. Values in bold face indicate there is a statistically significant difference found between the two groups. *P ⬍ .05. DO, distraction osteogenesis; CO, conventional orthognathic surgery; ⫹, further maxillary forward movements, ⫺, backward maxillary movement (relapse).
Table II. The mean horizontal P-point changes of the cleft maxilla by distraction osteogenesis and orthognathic surgery based on serial cephalometric analyses Changes in the horizontal movement of P-point Postoperative period 2-8 weeks (T1) (n) DO ⫽ 22, CO ⫽ 25 8-12 weeks (T2) (n) DO ⫽ 21, CO ⫽ 25 3-6 months (T3) (n) DO ⫽ 21, CO ⫽ 25 6-12 months (T4) (n) DO ⫽ 20, CO ⫽ 24 1-2 years (T5) (n) DO ⫽ 18, CO ⫽ 21 2-3 years (T6) (n) DO ⫽ 17, CO ⫽ 17 3-4 years (T7) (n) DO ⫽ 15, CO ⫽ 12 4-5 years (T8) (n) DO ⫽ 7, CO ⫽ 9 Total backward (⫺) movement Total forward (⫹) movement
Distraction osteogenesis ⴙ 2.08 mm (3.14) ⫹ 0.43 mm (1.45) ⫺ 0.02 mm (0.52) ⫺ 0.06 mm (0.73) ⫺ 0.03 mm (0.71) ⫺ 0.57 mm (0.71) ⫹ 0.38 mm (0.54) ⫹ 0.30 mm (0.42) 0.68 3.19
ⴙ 29.42% ⫹ 6.08% ⫺ 0.28% ⫺ 0.85% ⫺ 0.42% ⫺ 8.06% ⫹ 5.37% ⫹ 4.24% 9.61% 45.11%
Orthognathic surgery ⴚ 0.45 mm (0.54) ⫺ 0.04 mm (1.09) ⫺ 0.23 mm (0.99) ⫺ 0.50 mm (0.92) ⫺ 0.11 mm (0.77) ⫺ 0.13 mm (0.79) ⫺ 0.99 mm (2.07) ⫺ 0.00 mm (0.00) 2.45 —
ⴚ 6.51% ⫺ 0.58% ⫺ 3.33% ⫺ 7.23% ⫺ 1.59% ⫺ 1.88% ⫺ 14.33% ⫺ 0.00% 35.45% —
P value .003* .274 .404 .113 .778 .298 .175 .423
Values in parentheses are standard deviations. Percentages were computed based on the mean horizontal movement of P-point DO (7.07 mm), CO (6.91 mm). The dashes in the orthognathic surgery percent row mean that there is a backward movement of the maxilla. Values in bold face indicate there is a statistically significant difference found between the two groups. *P ⬍ .05. DO, distraction osteogenesis; CO, conventional orthognathic surgery; ⫹, further maxillary forward movement; ⫺, backward maxillary movement (relapse).
cally significant results between the 2 groups (P ⬍ .05) are highlighted in Tables I to IV, and are further elaborated as follows. Regarding the horizontal movement of A-point (Table I), it was noted that the DO group had further forward movement of 21.73%, 10.79%, 0.85%, and
3.98% at T1, T2, T4, and T7. In contrast, a relapse (backward movement) of 7.02%, 4.68%, 7.60%, and 2.34% was recorded in the CO group during the same period. Figure 4, a, shows the relapse trend in the horizontal movement of A-point. The graph shows that in the DO group, there was a gradual increase in the
views showed a balance face and competent lip; g, considerable transformation of the facial profile and lip contour; h, intraoral distractors fixed on each side of the maxilla using mini-screws; i, postoperative class I; and j, positive overjet. Postoperative 5 years: k-m, stable facial esthetics comparable to postoperative 3 months; n-o, slight decrease in overjet and overbite in occlusion when compared with postoperative 3 months but remained functional.
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Table III. The mean vertical A-point changes of the cleft maxilla by distraction osteogenesis and orthognathic surgery based on serial cephalometric analyses Changes in the vertical movement of A-point Postoperative period 2-8 weeks (T1) (n) DO ⫽ 22, CO ⫽ 25 8-12 weeks (T2) (n) DO ⫽ 21, CO ⫽ 25 3-6 months (T3) (n) DO ⫽ 21, CO ⫽ 25 6-12 months (T4) (n) DO ⫽ 20, CO ⫽ 24 1-2 years (T5) (n) DO ⫽ 18, CO ⫽ 21 2-3 years (T6) (n) DO ⫽ 17, CO ⫽ 17 3-4 years (T7) (n) DO ⫽ 15, CO ⫽ 12 4-5 years (T8) (n) DO ⫽ 7, CO ⫽ 9 Total upward (⫺) movement Total downward (⫹) movement
Distraction osteogenesis ⴙ 1.26 mm (1.95) ⫹ 0.51 mm (1.51) ⴚ 0.43 mm (0.73) ⫺ 0.11 mm (0.59) ⫹ 0.13 mm (1.20) ⴙ 0.64 mm (0.96) ⫹ 0.22 mm (0.95) ⫺ 1.13 mm (1.60) 1.67 38.21
ⴙ 96.18% ⴙ 38.93% ⴚ 32.82% ⫺ 8.40% ⫹ 9.92% ⴙ 48.85% ⫹ 16.79% ⫺ 86.25% 127.47% 210.67%
Orthognathic surgery ⴙ 0.16 mm (0.78) ⫺ 0.18 mm (1.24) ⴙ 0.13 mm (0.75) ⫹ 0.07 mm (1.22) ⫺ 0.18 mm (1.14) ⴚ 0.21 mm (0.47) ⫺ 0.18 mm (0.27) ⫺ 0.01 mm (0.00) 0.76 0.36
ⴙ 13.79% ⫺ 15.52% ⴙ 11.21% ⫹ 6.03% ⫺ 15.52% ⴚ 18.10% ⫺ 15.52% ⫺ 0.86% 65.52% 31.03%
P value .037* .134 .023* .556 .452 .025* .337 .424
Values in parentheses are standard deviations. Percentages were computed based on the mean horizontal movement of A-point DO (1.31 mm), CO (1.61 mm). *P ⬍ .05. DO, distraction osteogenesis; CO, conventional orthognathic surgery; ⫹, further maxillary downward movement; ⫺, upward maxillary movement (relapse).
Table IV. The mean vertical P-point changes of the cleft maxilla by distraction osteogenesis and orthognathic surgery based on serial cephalometric analyses Changes in the vertical movement of P-point Postoperative period 2-8 weeks (T1) (n) DO ⫽ 22, CO ⫽ 25 8-12 weeks (T2) (n) DO ⫽ 21, CO ⫽ 25 3-6 months (T3) (n) DO ⫽ 21, CO ⫽ 25 6-12 months (T4) (n) DO ⫽ 20, CO ⫽ 24 1-2 years (T5) (n) DO ⫽ 18, CO ⫽ 21 2-3 years (T6) (n) DO ⫽ 17, CO ⫽ 17 3-4 years (T7) (n) DO ⫽ 15, CO ⫽ 12 4-5 years (T8) (n) DO ⫽ 7, CO ⫽ 9 Total upward (⫺) movement Total downward (⫹) movement
Distraction osteogenesis ⴙ 1.20 mm (1.88) ⴙ 0.57 mm (1.31) ⴚ 1.11 mm (2.37) ⫺ 0.13 mm (0.56) ⫹ 0.11 mm (1.08) ⴙ 0.35 mm (0.63) ⫺ 0.10 mm (0.45) ⫺ 0.53 mm (0.76) 1.87 2.12
ⴙ 123.71% ⴙ 58.76% ⴚ 114.43% ⫺ 13.40% ⫹ 11.34% ⴙ 36.08% ⫺ 10.31% ⫺ 54.64% 192.78% 229.89%
Orthognathic surgery ⴙ 0.12 mm (0.92) ⴚ 0.53 mm (1.62) ⴙ 0.35 mm (1.63) ⫹ 0.02 mm (1.37) ⫺ 0.35 mm (0.95) ⴚ 0.30 mm (0.41) ⫺ 0.20 mm (0.28) ⫹ 0.00 mm (0.00) 1.38 0.49
ⴙ 13.64% ⴚ 60.23% ⴙ 39.77% ⫹ 2.27% ⫺ 39.77% ⴚ 34.09% ⫺ 22.73% ⫹ 0.00% 156.82% 55.68%
P value .028* .031* .029* .635 .201 .024* .438 .423
Values in parentheses are standard deviations. Percentages were computed based on the mean horizontal movement of P-point DO (0.97 mm), CO (0.88 mm). *P ⬍ .05. DO, distraction osteogenesis; CO, conventional orthognathic surgery; ⫹, further maxillary downward movement; ⫺, upward maxillary movement (relapse).
horizontal movement of A-point at T1 and T2. A slight decrease (relapse) was noted only at T6. In the CO group, an immediate downward (relapse) trend of the A-point was noted from T1 to T4. This downward movement of A-point starts to slow at T5 until T8. The longitudinal changes were highly significant at time points from T2 to T8 with the DO group being more stable than the CO group. In the horizontal movement of P-point (Table II), the DO group achieved further forward movement of 29.54% at T1, whereas in the CO group, a relapse (backward movement) of 6.51% was observed. In the continuing changes of P-point (Fig. 4, b), the DO group showed an abrupt increase in its horizontal movement at T1, and a slight increase at T2. A similar trend as the A-point can
also be observed wherein there was a slight dip noted at T6, after which a minimal increase could be observed up to T8. In the CO group, a small drop was found at T1. This downward trend continued from T2 until T8. The longitudinal changes of P-point were also highly significant and are similar to A-point (Fig. 4, a and b). Vertical changes. Regarding the vertical movement of A-point in the DO group (Table III), a downward movement of 96.18% and 48.85% at T1 and T6 was noted. However, at T3, there was an upward movement of 32.82%. The opposite was noted in the CO group. There was an initial downward movement of 13.79% and 11.21% during T1 and T3. At T6, there was a relapse (upward movement) of 18.10%. In Fig. 4, c, presenting the longitudinal changes, both the CO and
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T6
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-50 -100
Percentage relapse
Percentage relapse
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0
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20
-40
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100
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50 0
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-50 -100
-150
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Time points
Time points
Fig. 4. Continuing changes of the cleft maxilla following distraction osteogenesis and orthognathic surgery over 5 years of follow-up. a, Horizontal changes at A-point; b, horizontal changes at P-point; c, vertical changes at A-point; d, vertical changes at P-point.
the DO groups showed an upward trend in the vertical movement of A-point at T1, although the increase for the DO group was twice as much as that of the CO group. From T2 onward, it was noted that the movements achieved by the CO and DO groups were reversed. At T2, the DO group had a further increase; however, the CO group dropped. A slight drop was noted in the DO group, and an increase in the CO group, at both T3 andT4. Thereafter, the DO group started to have an increased trend until T7, and started to drop at T8. In contrast, the CO group was slightly dropping from T4 onward up to T8. In the vertical movement of P-point in the DO group (Table IV), a further downward movement of 123.71%, 58.76%, and 36.08% was noted at T1, T2, and T6. At T3, a relapse (upward movement) of 114.43% was found. In the CO group, further downward movement of 13.64% and 39.77% was noted at T1 and T3. In contrast, there was a relapse (upward movement) of 60.23% and 34.09 at T2 and T6. The percentage relapse for the vertical movement of P-point followed a similar trend when compared with the vertical movement of A-point (Fig. 4, d). The overall correlation between the extent of advancement and relapse of the A-point and P-point
were noted to be low. However, we found that the maxillary advancement was significantly correlated with the amount of relapse at certain postoperative time points: CO group ●
Horizontal relapse of P-point at 2 years postop (P ⫽ .026; r ⫽ ⫺0.522) DO group
● ● ●
Horizontal relapse of A-point at 1 year postop (P ⫽ .019; r ⫽ 0.560) Vertical relapse of A-point at 1 year postop (P ⫽ .008; r ⫽ 0.621) Vertical relapse of P-point at 1 year postop (P ⫽ .028; r ⫽ 0.533)
Angular changes of upper central incisors. There was a gradual increase in the U1 to SN angulation in the CO group (Table V). The U1 to SN angulation of CO became significantly different from DO at the first postoperative year and beyond. This was likely related to the postoperative skeletal relapse and orthodontic compensation wherein the U1 of the CO group became more proclined when compared with the DO group.
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Table V. Angular changes of the upper central incisors (U1) in relation to the Sella-Nasion line (SN) Angular changes of U1 to SN Postoperative period 2 8 3 6 1 2 3 4 5
weeks (n) DO ⫽ 22, CO ⫽ 25 weeks (n) DO ⫽ 21, CO ⫽ 25 months (n) DO ⫽ 21, CO ⫽ 25 months (n) DO ⫽ 20, CO ⫽ 24 years (n) DO ⫽ 18, CO ⫽ 21 years (n) DO ⫽ 17, CO ⫽ 17 years (n) DO ⫽ 15, CO ⫽ 12 years (n) DO ⫽ 15, CO ⫽ 12 years (n) DO ⴝ 7, CO ⴝ 9
Distraction osteogenesis
Orthognathic surgery
P value
104.33° (3.93) 103.89° (3.57) 104.83° (3.27) 104.67° (3.58) 104.85° (2.54) 104.75° (2.14) 105.10° (1.52) 105.11° (1.50) 105.00° (1.49)
105.66° (8.39) 105.58° (7.92) 107.67° (7.87) 108.04° (7.93) 109.30° (8.74) 109.92° (9.12) 112.87° (7.39) 115.28° (5.66) 115.80° (5.72)
.515 .407 .144 .086 .041* .043* .004* .002* .022*
Values in parentheses are standard deviations. *P ⬍ .05. DO, distraction osteogenesis; CO, conventional orthognathic surgery.
DISCUSSION The instability of the Le Fort I maxillary segment in patients with CLP by either distraction or orthognathic surgery manifests skeletally as retrusion of the maxilla because the main direction of surgical movement is forward and downward. Therefore, the backward and upward changes of the maxilla are considered as relapse and, dentally, this relapse in the backward direction will change the preplanned incisal class I occlusion to class III malocclusion. Dental relapse in the upward direction will manifest as loss of incisal show at rest and reduced anterior lower facial height. During the postoperative orthodontic phase, orthodontists normally compensate for the backward dental relapse by proclining the maxillary anterior teeth forward attempting to maintain the teeth in a class I incisal relationship, which was manifested by our finding of an increase in incisal angulation to SN. In this study, 3 of 25 CO patients and only 1 of 22 DO patients relapsed into clinical class III malocclusion despite orthodontic intervention or surgical repositioning. It is worthy to note that there was a significantly larger increase in postsurgical incisal angulation to SN in postoperative year 1 and beyond in the CO group than in the DO group. This occlusal complication correlates well with the more significant backward movement of the maxilla measured cephalometrically on the CO group when compared with the DO group. This study, for the first time in the literature, confirms that DO is more stable than CO by direct comparison with a sufficient sample of cases at different time points up to 5 years. To improve the accuracy of the cephalometric measurement on surgical changes, microscrews were placed in 2 locations of the maxilla for consistent localization of the maxillary landmarks. The precision of this method was confirmed by the cephalometric error analyses. Because the measure-
ment of changes is quite small, extra precautions were taken in the error analyses by evaluating both the reliability and reproducibility of landmark identification and the measurement of surgical movement between 2 selected time periods. This supports the good precision on the point-to-point comparison results between the CO and DO groups, as well as the longitudinal changes of the maxilla between the groups. The surgical relapse of the cleft CO has been well studied and our meta-analysis published in 2005 highlighted that significant relapse can occur in both horizontal and vertical planes.10 The results of our cleft CO cases showed a similar trend with significant relapse occurring within the first postoperative year. The cumulative percentage relapse of the CO group at 5 years in the horizontal plane was 36.99% (Table I). A similar finding was observed by Erbe et al.11 after evaluating 11 patients who received maxillary osteotomy. After a postoperative follow-up of 59 months, they found a relapse rate of 38% to 44%. A number of factors have been correlated with the cause of relapse in patients with CLP. Hochban et al.12 acknowledged that the extent of maxillary deficiency and occlusal disharmony form the main contributing factors for relapse. They also acknowledged that cleft maxilla presented a greater variation in anatomy and requirement for more complicated orthodontic treatment as compared to noncleft patients. Scarring from previous surgery of the lip, alveolus, palate, and pharyngeal repair can inhibit the mobilization of the maxilla during the operation, causing the maxilla to more likely contract after the surgery. In contrast, there are few studies reporting the relapse rate on cleft DO and most have small sample sizes and short follow-up.4 In the literature, the relapse rate reported was much smaller than the CO. This study provides evidence to support that the distracted maxilla
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is stable in patients with CLP and we found that the maxilla actually came farther forward and downward during the initial postoperative period. The stability was maintained in the long term of up to 5 years. In the DO group, the A-point relapsed only 8.24% horizontally at T6. The relapse in the DO group did not seem to have such a great effect because, as we can see from Table I, there was a much larger cumulative forward movement of the maxilla from T1 to T5 and from T7 toT8. When we look at the overall relapse rate, we found a statistically significant difference in the horizontal plane of both the A- and P-points between the CO and DO groups. It showed that the relapse rate of the CO group was higher than in the DO group at 5 years postoperatively (P ⬍ .05). This forward movement of the maxilla could be attributed to the use of elastic traction to control the occlusion during the consolidation period of distraction, when the regenerated callus remains malleable. Lauwers et al.13 reported that elastic can protract the maxilla further forward by 3 mm and provide better occlusion, and it was possible within the first 3 months. Caution is needed when using orthodontic elastics because they may accidentally pull the maxilla downward, which may result in excessive incisal show and incompetent lips.5 The reasons for the significantly smaller relapse in DO when compared with CO is likely related to the gradual surgical movement of the maxilla, which causes less counterforce to pull the maxilla back to the original position. The stability of the distractors also plays a role in resisting the backward and upward pull from the posterior maxillary musculature or scars in the early postoperative period. We believe that the internal distractor, which we selected for this study, is one of the main factors contributing to this success. This is highlighted in the literature. The relapse rate as reported by Rachmiel et al.,14 in a long-term study of cleft maxillary hypoplasia, found a relapse rate of 7.32% after 2 years with the use of internal distractors. Figueroa et al.20 performed the first long-term study over 3 years on maxillary advancement using rigid external distractors (RED) in 17 patients with CLP. They presented the relapse as a change in incisal angulation gained rather than the metric changes in the horizontal and vertical planes. The 10.2° gained in the SNA angle after distraction had gradually decreased 23.5% during the postoperative period. Baek et al.15 conducted a clinical study by comparing the stability between DO and Le Fort I osteotomy in 29 cleft patients with maxillary hypoplasia. In this study, 14 patients had maxillary advancement with Le Fort I osteotomy (group 1), and 11 patients had maxillary distraction using the RED system (group 2). They found that the average amount of relapse in the first and
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second groups was 24% and 21%, respectively. The use of the RED device did not bring any advantage in significantly reducing the relapse rate. This evidence indicates better long-term stability of the transposed maxilla with intraoral distractors than extraoral distractors. This may be related to the way that distraction forces are delivered. Extraoral distractors pull the maxilla forward, whereas intraoral distractors transpose the maxilla forward. We hypothesize that when the extraoral distractors are removed, the tension accumulated from the pulling force tends to rebound resulting in a higher relapse rate. This does not occur with the intraoral distracters, which transpose the maxilla slowly forward with transverse screws on both sides. Hence, intraoral distractors are more stable. Many studies in the literature include children in the distraction groups.14,16 The true extent of relapse in the study reported by Baek et al.15 was unpredictable, as 45.5% of the samples were young patients with incomplete mandibular growth. Because they included both children and mature adults, it was difficult to separate the long-term changes of the maxillary position resulting in surgical relapse from those of facial growth. In addition, if distraction is performed during the growth period, relapse can be exaggerated as a result of continuing mandibular growth. Many of the patients would therefore require another surgery of either CO or DO after the jaw growth matures.17 In our study, this confusion has been eliminated from our research design because all of our patients were considered skeletally mature, having reached age 16 or older and demonstrated radial epiphysis fusion on the hand-wrist radiographs. In children receiving DO, there were reports of some further growth from the distracted maxilla. Harada et al.18 examined the long-term skeletal and dental changes in 2 children and 1 adult with CLP who underwent maxillary distraction using RED. They reported that the long-term skeletal and dental stability was relatively well maintained in the adult patients. Further maxillomandibular growth was observed in the reported children after maxillary distraction. In a follow-up study with a larger sample of children by the same investigators, they confirmed that the maxillary growth was in an inferior direction and the mandibular growth would continue in the AP direction. They recommended that in maxillary distraction of children, the maxillary advancement needs to be overcorrected to reach the estimated adult position to accommodate for the continuing antero-inferior growth of the mandible. The masticatory function of these distracted children would markedly deteriorate for many years until mandibular growth catches up to reach a rea-
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sonably stable dental occlusion. Predicting the mandibular growth of an individual child is impossible with any degree of precision. Hence, a future corrective surgery is likely needed when growth matures. We would not recommend maxillary distraction in children with CLP unless the maxillary retrusion is so severe that it constricts the nasopharyngeal airway presenting as sleep apnea or when children are psychologically depressed. In this study, all the patients with cleft alveolus received alveolar bone grafting at the age of 9 to 10. However, it is possible to conduct distraction in patients with residual alveolar clefts as long as the individual cleft segments are bridged together by miniplates as proposed by Rachmiel et al.19 Otherwise, the buccal segment of the cleft alveolus will move forward hinging on the alveolar cleft space forming a transversely widened dental arch rather than moving the full maxilla forward. CONCLUSION In summary, we have evaluated the long-term stability of DO and CO in patients with CLP up to 5 years. Both techniques can effectively transpose the cleft maxilla forward and downward in correction of moderate maxillary retrusion. The cleft maxilla in the CO group relapsed backward and upward, whereas in the DO group, it advanced more forward and downward over 5 years. The upper incisor angulation following CO increased, whereas following DO, it stayed the same with significant difference between the 2 groups beyond the first postoperative year.
6.
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9. 10.
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We thank our patients who were so willing to participate in this study and their committed follow-up attendance. We would also like to acknowledge the contributions of Ms. Vicki Yip, for her assistance with the illustrations, and Mr. Shadow Yeung, who provided statistical assistance.
18.
19.
REFERENCES 1. Ross RB. Treatment variables affecting facial growth in complete unilateral cleft lip and palate. Cleft Palate J 1987;24:5-77. 2. Adlam DM, Yau CK, Banks P. A retrospective study of the stability of midface osteotomies in cleft lip and palate patients. Br J Oral Maxillofac Surg 1989;27:265-76. 3. Thongdee P, Samman N. Stability of maxillary surgical movement in unilateral cleft lip and palate with preceding alveolar bone grafting. Cleft Palate Craniofac J 2005;42(6):664-74. 4. Hoffman GR, Brennan PA. The skeletal stability of one-piece Le Fort 1 osteotomy to advance the maxilla; Part 2. The influence of uncontrollable clinical variables. Br J Oral Maxillofac Surg 2004;42(3):226-30. 5. Cheung LK, Chua HDP, Hagg MB. Cleft maxillary distraction
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versus orthognathic surgery: clinical morbidities and surgical relapse. Plast Reconstr Surg 2006;118:996-1008. Cheung LK, Fung SC, Li T, Samman N. Posterior maxillary anatomy: implications for Le Fort I osteotomy. Int J Oral Maxillofac Surg 1998;27:346-51. Cheung LK, Chua HD, Lo J, Luk WKH. Vector guidance splint for internal maxillary distraction: a technical note. J Oral Maxillofac Surg 2007;65:1852-6. Cheung LK, Samman N, Hui E, Tideman H. The 3-dimensional stability of maxillary osteotomies in cleft lip and palate patients with residual alveolar clefts. Br J Oral Maxillofac Surg 1994; 32:6-12. Houston WJB, The analysis of errors in orthodontic measurements. Am J Orthod 1983;83(5):382-9. Cheung LK, Chua HDP. A meta-analysis of cleft maxillary osteotomy and distraction osteogenesis. Int J Oral Maxillofac Surg 2005;35(1):14-24. Erbe M, Stoelinga PJW, Leenen RJ. Long-term results of segmental repositioning of the maxilla in cleft palate patients without previously grafted alveolo-palatal clefts. J Craniomaxillofac Surg 1996;24:109-17. Hochban W, Ganss C, Austermann KH. Long-term results after maxillary advancement in patients with clefts. Cleft Palate Craniofac J 1993;30(2):237-43. Lauwers F, Mayorca-Guilliani M, Lopez R, Woisard-Bassols V. Maxillofacial intraoral distraction osteogenesis followed by elastic traction in cleft maxillary deformity. Int J Oral Maxillofac Surg 2005; 34:85-8. Rachmiel A, Aizenbud D, Peled M. Long-term results in maxillary deficiency using intraoral devices. Int J Oral Maxillofac Surg 2005;34(5):473-9. Baek SH, Lee JK, Lee JH, Kim MJ, Kim JR. Comparison of treatment outcome and stability between distraction osteogenesis and Le Fort I osteotomy in cleft patients with maxillary hypoplasia. J Craniofac Surg 2007;18(5):1209-15. Polley JW, Figueroa AA. Management of severe maxillary deficiency in childhood and adolescence through distraction osteogenesis with an external adjustable, rigid distraction device. Plast Reconstr Surg 1997;8(3):181-5. Baker SB, Reid RR, Burkey B, Bartlett SP. Rapid maxillary distraction protocol utilizing the halo distraction system and rigid internal fixation. Cleft Palate Craniofac J 2007;44(5):476-81. Harada K, Sato M, Omura K. Maxillary distraction in patients with cleft deformity using a rigid external distraction device: a pilot study on the distraction ratio of the maxilla to the device. Scand J Plast Reconstr Surg Hand Surg 2004;38:277-80. Rachmiel A. Treatment of maxillary cleft palate: distraction osteogenesis versus orthognathic surgery-part one: maxillary distraction. J Oral Maxillofac Surg 2007;65(4):753-7. Figueroa AA, Polley JW, Friede H, Ko EW. Long-term skeletal stability after maxillary advancement with distraction osteogenesis using a rigid external distraction device in cleft maxillary deformities. Plast Reconstr Surg 2004;114:1382-92.
Reprint requests: Lim Kwong Cheung, BDS, FRACDS (OMS) Oral & Maxillofacial Surgery 2/F Prince Philip Dental Hospital 34 Hospital Road Hong Kong SAR, China [email protected]
ORAL AND MAXILLOFACIAL SURGERY
Editor: James R. Hupp
Cleft maxillary distraction versus orthognathic surgery—which one is more stable in 5 years? Hannah Daile P. Chua, DDM, MA, MDS, PhD,a Margareta Bendeus Hägg, DDS, FHKAM (DS), FCDSHK (Orthod),b and Lim Kwong Cheung, BDS, FRACDS (OMS), PhD,c Hong Kong SAR, China THE UNIVERSITY OF HONG KONG
Objective. The objective of this study was to compare the long-term stability of distraction osteogenesis (DO) and conventional orthognathic surgery (CO) in patients with cleft lip and palate (CLP). Study design. CLP patients requiring maxillary advancement of 4 to 10 mm were randomized and assigned to either CO or DO. In the CO group, the maxilla was fully mobilized to the preplanned position and fixed using titanium miniplates. In the DO group, the maxilla was mobilized to a limited extent and distractors were fixed on each side of the maxilla. Serial lateral cephalographs were taken for the assessment of stability at different postoperative periods up to 5 years. Results. In the CO group, the maxilla relapsed backward and upward, whereas in the DO group, it advanced more forward and downward over 5 years. Conclusions. Distraction of the cleft maxilla can achieve better long-term skeletal stability in maintaining its advanced position than CO. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;109:803-814)
Patients with cleft lip and palate (CLP) usually present with depressed midface and narrow maxillary dental arch as a result of dentofacial anomaly, combined with scar tissue from the early surgical repair of CLP.1 Many of these cases require combined orthodontic and orthognathic surgery to correct the dentofacial deformity.2 The aim of treatment is to align the teeth in the alveolar process followed by advancement of the maxilla to a normal position in relation to the cranium. Numerous studies have been made about the longterm stability of maxillary advancement with a Le Fort This clinical study was supported by the Competitive Earmarked Research Grant from the Hong Kong Research Grant Council (Reference code: HKU 7577/05M). a Post-doctoral fellow, Discipline of Oral & Maxillofacial Surgery, Faculty of Dentistry, The University of Hong Kong, China. b Part-time lecturer, Discipline of Orthodontics, Faculty of Dentistry, The University of Hong Kong, China. c Chair Professor, Discipline of Oral and Maxillofacial Surgery, Faculty of Dentistry, The University of Hong Kong, China. Received for publication Jul 21, 2009; returned for revision Oct 5, 2009; accepted for publication Oct 21, 2009. 1079-2104/$ - see front matter © 2010 Mosby, Inc. All rights reserved. doi:10.1016/j.tripleo.2009.10.056
I osteotomy.3 The amount of relapse in noncleft patients with maxillary hypoplasia has been reported to be around 10%.4 In patients with CLP, the relapse rates are much higher, ranging from 25% up to 50%.3 Distraction osteogenesis has opened a new perspective for the treatment of various skeletal anomalies, particularly for the patient with CLP. Our center has published the first randomized, controlled trial in comparing the clinical morbidities and skeletal relapse of patients with CLP receiving either distraction osteogenesis (DO) or conventional orthognathic surgery (CO).5 The results of our study showed that there were no major differences in the clinical morbidities between CO and DO groups. However, DO provided better skeletal stability, whereas there was a significant amount of skeletal relapse in the first 12 weeks following CO. To our knowledge, there is no randomized controlled trial evaluating the long-term stability of CO and DO in patients with CLP reaching 5 years. The aim of this study was to compare the long-term stability of maxillary Le Fort I advancement in patients with CLP by either distraction with internal distractors or immediate transposition with titanium plate fixation. 803
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MATERIAL AND METHODS Patient selection Eligible subjects were selected from patients with CLP needing Le Fort I osteotomy for correction of maxillary retrusion with moderate severity. For inclusion, patients had to be aged 16 or older and with complete bony fusion of the radial epiphysis confirmed by hand-wrist radiographs. The maxillary alveolar clefts had to have been grafted and each patient had undergone presurgical arch alignment and dental decompensation by fixed orthodontics at the University Cleft Lip and Palate Center. All patients underwent a standard surgical assessment, dental model surgery, and prediction tracing. Patients who required maxillary advancement ranging from 4 to 10 mm based on the model surgery movement measured from the upper incisal tip were included in the study. Syndromic patients and those who presented with systemic diseases were excluded. Patients who required maxillary advancement of more than 10 mm were treated by DO, whereas those who needed advancement of less than 4 mm were treated by CO. These latter 2 groups were excluded from the study. Patients who satisfied the inclusion criteria were randomly assigned to 2 surgical groups for treatment by distraction with internal maxillary distractors or by conventional orthognathic surgery with miniplate fixation, respectively. A senior investigator (L.K.C.) with extensive experience in both distraction and orthognathic surgery performed the clinical assessment and was in charge of the randomization of the patients by using a table of random numbers generated from a computer. The study was approved by the Faculty Ethics Committee and all the patients involved in the study provided written consent. The surgery was carried out between June 2002 and January 2008 in the Discipline of Oral and Maxillofacial Surgery, Faculty of Dentistry. Surgical technique A continuous maxillary incision 5 mm above the mucogingival margin from the right first molar to the left first molar was made. The buccal tissue was reflected to expose the bony alveolus and zygoma. The buccal osteotomy was completed anteriorly from the pyriform rim to reach the pterygomaxillary junction posteriorly. The nasal septum was transected at its base by a septal osteotome. Any maxillary impacted wisdom tooth was elevated and the tuberosities of both sides were osteotomized by a wedge osteotome.6 The maxillae were downfractured with finger pressure and the maxilla was fully mobilized. The maxillary sinus walls and nasal septum were then excised according to the model surgery. Maxillary segmentalization was per-
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formed in both groups, if necessary, according to the dental model surgical plan. In the CO group, the maxilla was mobilized fully with the use of a pterygoid osteotome and transposed to the preplanned position with little tension guided by a custom-made occlusal wafer. The arch bars were ligated to both the maxillary and mandibular dental arches. The teeth were placed in the occlusal wafer to determine the anteroposterior (AP) movement and then placed together in intermaxillary fixation (IMF). The maxillary vertical markings were checked to ensure vertical movement made according to the dental model surgery. The mobilized maxilla was fixed with 2 titanium miniplates on each side at the zygomatic buttress and the pyriform region. Sheets of bone grafts harvested from the medial nasal walls or septum were used to cover any bony gaps in the lateral maxillary walls and in the segmentalized osteotomy gaps. IMF and the occlusal wafer were removed, and the accuracy of the dental interdigitation was checked. A standardized technique of maxillary distraction with the use of internal distractors was developed for the DO group. A similar vestibular incision to the orthognathic surgical exposure was made. The buccal tissue was reflected to expose the bony alveolus and zygoma. An internal bone-borne maxillary distractor (Synthes, West Chester, PA) was bent and adapted to the contour of the maxillary alveolus and zygomatic buttress. The planned buccal cut of the Le Fort I osteotomy was marked out to ensure clearance from between the 2 distractor footplates. Thereafter, the distractors were removed and a similar osteotomy procedure to that of the orthognathic surgery group was performed. In distraction, the maxilla was also fully mobilized, but not transposed to the final occlusal position. The maxillary occlusal plane was oriented according to the vertical markings established at model surgery and any bony interference was removed. In cases where segmentalization of the maxilla was performed, the segments were bridged with titanium miniplates and screws. The distractors were then reinserted in their predetermined positions. The distractor body on either side was made parallel to the wire orientation in the vector guidance splint.7 Once the distractors were fixed in their 3-dimensional orientation, IMF was cut and the vector guidance splint removed. The distractors on either side were activated for a few millimeters to check the correctness of maxillary transport and then rewound back to good bone contact position. The mucosal wound was then closed by continuous suturing to leave the activator rod external to the mucosal wound for later activation. To improve the accuracy of measurement of maxillary movement and relapse, 2 additional 1.0-mm tita-
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nium microscrews (Synthes) were inserted in both groups. One microscrew was placed at the most concave part of the anterior maxilla at the midline (Apoint) and another was fixed at the posterior maxilla above the mesial root of the first molar (P-point). Mandibular osteotomies were performed in the same surgery, if needed, according to the skeletal diagnosis (e.g., mandibular dentoalveolar protrusion in AP direction, mandibular protrusion in AP direction, asymmetric mandibular protrusion in AP direction). After a latency of 3 days, activation was commenced at 1 mm per day in 2 rhythms with an activating key by the patients themselves or their relatives until a class I incisal relationship was achieved. Light orthodontic elastic was applied to control the occlusion in both groups during the early postoperative period. The distractors were removed after the third postoperative month. The patients were reviewed at regular postoperative intervals of 2 and 8 weeks; 3 and 6 months; and 1, 2, 3, 4, and 5 years. Lateral cephalometric assessment Standardized lateral cephalographs were taken on all patients enrolled in this study both shortly before the operation and postoperatively at 2 and 8 weeks; 3 and 6 months; and 1, 2, 3, 4, and 5 years. All the lateral cephalographs were taken using the same orthopantomograph machine (Philips Orthoralix SD, Monza, Italy) with the patients in natural head position and centric occlusion with the lips in repose. The method of analysis was a modification advocated by Cheung et al.8 A horizontal (X) reference line was constructed at 7 degrees from a linear line connecting the sella (S) and nasion (N) points (SN line). The vertical (Y) reference line was a line drawn perpendicular to the horizontal reference line passing through the sella. The lateral cephalographs were traced on high-quality matte acetate overlay sheets (Orthotrace, Rocky Mountain Orthodontics Inc., Denver, CO) to provide details of the soft- and hard-tissue landmarks. All tracings were superimposed using the sella, nasion, and cranial base structures using a method of anatomic best fit. The linear movements of the landmarks were measured using an electronic digital caliper (Digit Cal, Tesa, Switzerland) with accuracy up to 2 decimal points. For the angular changes, a college protractor (Staedtler Inc., Chatsworth, CA) was used. Each reading was taken 3 times and a mean value was recorded. Stability assessment Changes in the stability of the maxilla were based on the movement of the microscrew at A-point and P-point
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S
7°
P Vertical reference line
N Horizontal reference line
A
Fig. 1. Reference lines and landmarks used for the cephalometric analysis of maxillary stability. S, sella; N, nasion; A, subspinale A-point; P, micro-screw above the mesial root of the upper 1st molar.
in horizontal and vertical planes in relation to the X and Y reference lines, respectively. The intersecting angle formed between the central axes of the maxillary central incisor to the SN line was also measured to determine any changes of the incisal angulation in both treatment groups (Fig. 1). The time between the postoperative intervals of 2 to 8 weeks was assigned as T1, 8 to 12 weeks as T2, 3 to 6 months as T3, 6 to 12 months as T4, 1 to 2 years as T5, 2 to 3 years as T6, 3 to 4 years as T7, and 4 to 5 years as T8. The stability results were compared between the DO and CO group by Student 2-sample t test and the threshold of significance was set at P less than .05. Error analysis on lateral cephalograph measurements The errors of cephalometric readings were calculated based on the measurements of 40 lateral cephalographs randomly selected from 20 patients. Landmark identification of the hard- and soft-tissue points was made and the points were digitized. The same measurement was repeated 1 week later. Reliability and random error analyses on the 2 sets of measurements were performed. The reliability of the measurements was eval-
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Fig. 2. Clinical changes of a 23-year-old female with unilateral CLP who underwent conventional orthognathic surgery. Preoperative: a, frontal view showed incompetent lips and flaring of left ala; b, lateral view showed severe retrusion of the maxilla and protrusion of the mandible with eversion of the lower lip; c, lateral cephalograph confirmed retrusion of the maxilla and protrusion of the mandible; d, intraoral view showed class III malocclusion and e, negative overjet. Postoperative 6 months:
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uated by paired t test with a 5% level of significance (SPSS Inc., Chicago, IL). The reproducibility of random error is important because it determines the metric differences between the 2 measurements and the acceptability of the differences. Dahlberg’s formula9 was used to determine the random error. RE ⫽
冑
兺 d2 2n
RE ⫽ Random error n ⫽ sample size d ⫽ difference between the 2 measurements
To determine whether there is any significant error in measuring the surgical changes between 2 postoperative time points, which form the basis of comparison between the treatment groups, the postoperative lateral cephalographs (postoperative 3 and 6 months) of 10 randomly selected patients were also chosen. The mean differences in the surgical stability of the maxilla were recorded. The same measurement was repeated 1 week later. The reliability analysis using paired t tests confirmed no significant difference between 2 tracings carried out at separate occasions in both landmark identification and surgical movement changes. The random error analysis confirmed a small metric difference in measurements, but it was within the clinically acceptable limit of 1.0 mm. RESULTS Twenty-two of the 47 patients who participated in the study underwent distraction with internal maxillary distractors, whereas the other 25 had conventional orthognathic surgery. Typical cases of CO and DO with follow-up of 5 years are illustrated in Fig. 2 and Fig. 3, respectively. Based on the planned model surgery movement measured from the upper incisal tip, the mean maxillary advancement for the DO group was 6.59 mm, with a standard deviation (SD) of 1.93. For the CO group, the maxilla was advanced a mean of 6.46 mm, with an SD of 1.60. There was no statistically significant difference in the surgical movement between the 2 groups (P ⫽ .82). In the CO group, 24 patients had double-jaw surgery and 1 had surgery on the maxilla only. Segmentalization of the Le Fort I maxilla was performed in 13 of the 25 cases. There was no statistically significant difference between patients who had double-jaw surgery
and those who had single-jaw surgery (P ⫽ .73). In addition, there was no statistically significant difference between the patients who had segmentalization and nonsegmentalization of the Le Fort I osteotomy (P ⫽ .68). In the DO group, 17 patients had double-jaw surgery and 1 had single-jaw surgery. Segmentalization of the Le Fort I maxilla was performed in 4 cases. We also did not find any statistically significant difference between patients who had double-jaw surgery and those who had single-jaw surgery (P ⫽ .70). With regard to the segmentalized maxilla, there was no significant difference between the patients who had segmentalization and nonsegmentalization (P ⫽ .84). To determine the horizontal and vertical movements achieved during the surgery, a superimposition of the lateral cephalographs taken preoperatively and at 2 weeks postoperatively were performed. Because there was no radiographic marker found on the preoperative lateral cephalographs, the method of anatomic best fit of the maxilla was used to transfer the position of both microscrews found on the postoperative lateral cephalographs to the preoperative lateral cephalographs. The changes in the horizontal and vertical movements of both microscrews in relation to the horizontal and vertical reference lines of the lateral cephalographs were then recorded and analyzed. The mean horizontal movement of A-point (advancement) in the DO and CO groups was found to be 7.04 mm and 6.84 mm with SDs of 1.70 and 1.77, respectively. The mean horizontal movement of P-point (advancement) in the DO and CO groups was 7.07 mm and 6.91 mm, with SDs of 1.68 and 1.89. The mean vertical movement of A-point and P-point in the CO group was 1.16 mm (SD ⫽ 2.33) and 0.88 mm (SD ⫽ 1.91); for the DO group, the movements were 1.31 mm (SD ⫽ 2.98) and 0.88 mm (SD⫽ 2.74). Independent t tests revealed that there were no statistically significant differences between the mean advancement of the maxilla based on the model surgery and horizontal movement of A-point measured from the lateral cephalographs in both groups (DO group: P ⫽ .43; CO group: P ⫽ .27). Skeletal stability Horizontal changes. The horizontal and vertical movements of both A- and P-points in the DO and CO groups at each time period were compared. The statisti-
f, frontal view showed a balanced face; g, improvement of the facial profile and lip contour; h, lateral cephalograph showed the advanced maxilla fixed with titanium internal fixation; i, postoperative class I and j, positive overjet. Postoperative 5 years: k-o, stable facial esthetics and occlusal outcome comparable to postoperative 6 months.
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Fig. 3. Clinical changes of a 24-year-old male with bilateral CLP who underwent distraction osteogenesis with intraoral maxillary distracters. Preoperative: a, preoperative views showed incompetent lips; b, retrusion of the maxilla, protrusion of the mandible, and severe lower lip protrusion; c, lateral view showed severe retrusion of the maxilla and protrusion of the mandible; d, oral views showed negative overjet and e, class III malocclusion and presence of anterior open bite. Postoperative 3 months: f, postoperative
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Table I. The mean horizontal A-point changes of the cleft maxilla by distraction osteogenesis and orthognathic surgery based on serial cephalometric analyses Changes in the horizontal movement of A-point Postoperative period 2-8 weeks (T1) (n) DO ⫽ 22, CO ⫽ 25 8-12 weeks (T2) (n) DO ⫽ 21, CO ⫽ 25 3-6 months (T3) (n) DO ⫽ 21, CO ⫽ 25 6-12 months (T4) (n) DO ⫽ 20, CO ⫽ 24 1-2 years (T5) (n) DO ⫽ 18, CO ⫽ 21 2-3 years (T6) (n) DO ⫽ 17, CO ⫽ 17 3-4 years (T7) (n) DO ⫽ 15, CO ⫽ 12 4-5 years (T8) (n) DO ⫽ 7, CO ⫽ 9 Total backward (⫺) movement Total forward (⫹) movement
Distraction osteogenesis ⴙ 1.53 mm (1.21) ⴙ 0.76 mm (1.04) ⫹ 0.10 mm (0.71) ⴙ 0.06 mm (0.39) ⫹ 0.03 mm (0.75) ⫺ 0.58 mm (0.44) ⴙ 0.28 mm (0.33) ⫹ 0.09 mm (0.13) 0.58 2.85
ⴙ 21.73% ⴙ 10.79% ⫹ 1.42% ⴙ 0.85% ⫹ 0.43% ⫺ 8.24% ⴙ 3.98% ⫹ 1.28% 8.24% 40.48%
Orthognathic surgery ⴚ 0.48 mm (0.35) ⴚ 0.32 mm (1.22) ⫺ 0.19 mm (0.87) ⴚ 0.52 mm (0.60) ⫺ 0.06 mm (0.60) ⫺ 0.40 mm (0.70) ⴚ 0.16 mm (0.23) ⫺ 0.40 mm (0.57) 2.53 —
ⴚ 7.02% ⴚ 4.68% ⫺ 2.78% ⴚ 7.60% ⫺ 0.88% ⫺ 5.85% ⴚ 2.34% ⫺ 5.85% 31.0% —
P value .0001* .007* .273 .002* .701 .538 .039* .352
Values in parentheses are standard deviations. Percentages were computed based on the mean horizontal movement of A-point DO (7.04 mm), CO (6.84 mm). The dashes in the orthognathic surgery percent row mean that there is a backward movement of the maxilla. Values in bold face indicate there is a statistically significant difference found between the two groups. *P ⬍ .05. DO, distraction osteogenesis; CO, conventional orthognathic surgery; ⫹, further maxillary forward movements, ⫺, backward maxillary movement (relapse).
Table II. The mean horizontal P-point changes of the cleft maxilla by distraction osteogenesis and orthognathic surgery based on serial cephalometric analyses Changes in the horizontal movement of P-point Postoperative period 2-8 weeks (T1) (n) DO ⫽ 22, CO ⫽ 25 8-12 weeks (T2) (n) DO ⫽ 21, CO ⫽ 25 3-6 months (T3) (n) DO ⫽ 21, CO ⫽ 25 6-12 months (T4) (n) DO ⫽ 20, CO ⫽ 24 1-2 years (T5) (n) DO ⫽ 18, CO ⫽ 21 2-3 years (T6) (n) DO ⫽ 17, CO ⫽ 17 3-4 years (T7) (n) DO ⫽ 15, CO ⫽ 12 4-5 years (T8) (n) DO ⫽ 7, CO ⫽ 9 Total backward (⫺) movement Total forward (⫹) movement
Distraction osteogenesis ⴙ 2.08 mm (3.14) ⫹ 0.43 mm (1.45) ⫺ 0.02 mm (0.52) ⫺ 0.06 mm (0.73) ⫺ 0.03 mm (0.71) ⫺ 0.57 mm (0.71) ⫹ 0.38 mm (0.54) ⫹ 0.30 mm (0.42) 0.68 3.19
ⴙ 29.42% ⫹ 6.08% ⫺ 0.28% ⫺ 0.85% ⫺ 0.42% ⫺ 8.06% ⫹ 5.37% ⫹ 4.24% 9.61% 45.11%
Orthognathic surgery ⴚ 0.45 mm (0.54) ⫺ 0.04 mm (1.09) ⫺ 0.23 mm (0.99) ⫺ 0.50 mm (0.92) ⫺ 0.11 mm (0.77) ⫺ 0.13 mm (0.79) ⫺ 0.99 mm (2.07) ⫺ 0.00 mm (0.00) 2.45 —
ⴚ 6.51% ⫺ 0.58% ⫺ 3.33% ⫺ 7.23% ⫺ 1.59% ⫺ 1.88% ⫺ 14.33% ⫺ 0.00% 35.45% —
P value .003* .274 .404 .113 .778 .298 .175 .423
Values in parentheses are standard deviations. Percentages were computed based on the mean horizontal movement of P-point DO (7.07 mm), CO (6.91 mm). The dashes in the orthognathic surgery percent row mean that there is a backward movement of the maxilla. Values in bold face indicate there is a statistically significant difference found between the two groups. *P ⬍ .05. DO, distraction osteogenesis; CO, conventional orthognathic surgery; ⫹, further maxillary forward movement; ⫺, backward maxillary movement (relapse).
cally significant results between the 2 groups (P ⬍ .05) are highlighted in Tables I to IV, and are further elaborated as follows. Regarding the horizontal movement of A-point (Table I), it was noted that the DO group had further forward movement of 21.73%, 10.79%, 0.85%, and
3.98% at T1, T2, T4, and T7. In contrast, a relapse (backward movement) of 7.02%, 4.68%, 7.60%, and 2.34% was recorded in the CO group during the same period. Figure 4, a, shows the relapse trend in the horizontal movement of A-point. The graph shows that in the DO group, there was a gradual increase in the
views showed a balance face and competent lip; g, considerable transformation of the facial profile and lip contour; h, intraoral distractors fixed on each side of the maxilla using mini-screws; i, postoperative class I; and j, positive overjet. Postoperative 5 years: k-m, stable facial esthetics comparable to postoperative 3 months; n-o, slight decrease in overjet and overbite in occlusion when compared with postoperative 3 months but remained functional.
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Table III. The mean vertical A-point changes of the cleft maxilla by distraction osteogenesis and orthognathic surgery based on serial cephalometric analyses Changes in the vertical movement of A-point Postoperative period 2-8 weeks (T1) (n) DO ⫽ 22, CO ⫽ 25 8-12 weeks (T2) (n) DO ⫽ 21, CO ⫽ 25 3-6 months (T3) (n) DO ⫽ 21, CO ⫽ 25 6-12 months (T4) (n) DO ⫽ 20, CO ⫽ 24 1-2 years (T5) (n) DO ⫽ 18, CO ⫽ 21 2-3 years (T6) (n) DO ⫽ 17, CO ⫽ 17 3-4 years (T7) (n) DO ⫽ 15, CO ⫽ 12 4-5 years (T8) (n) DO ⫽ 7, CO ⫽ 9 Total upward (⫺) movement Total downward (⫹) movement
Distraction osteogenesis ⴙ 1.26 mm (1.95) ⫹ 0.51 mm (1.51) ⴚ 0.43 mm (0.73) ⫺ 0.11 mm (0.59) ⫹ 0.13 mm (1.20) ⴙ 0.64 mm (0.96) ⫹ 0.22 mm (0.95) ⫺ 1.13 mm (1.60) 1.67 38.21
ⴙ 96.18% ⴙ 38.93% ⴚ 32.82% ⫺ 8.40% ⫹ 9.92% ⴙ 48.85% ⫹ 16.79% ⫺ 86.25% 127.47% 210.67%
Orthognathic surgery ⴙ 0.16 mm (0.78) ⫺ 0.18 mm (1.24) ⴙ 0.13 mm (0.75) ⫹ 0.07 mm (1.22) ⫺ 0.18 mm (1.14) ⴚ 0.21 mm (0.47) ⫺ 0.18 mm (0.27) ⫺ 0.01 mm (0.00) 0.76 0.36
ⴙ 13.79% ⫺ 15.52% ⴙ 11.21% ⫹ 6.03% ⫺ 15.52% ⴚ 18.10% ⫺ 15.52% ⫺ 0.86% 65.52% 31.03%
P value .037* .134 .023* .556 .452 .025* .337 .424
Values in parentheses are standard deviations. Percentages were computed based on the mean horizontal movement of A-point DO (1.31 mm), CO (1.61 mm). *P ⬍ .05. DO, distraction osteogenesis; CO, conventional orthognathic surgery; ⫹, further maxillary downward movement; ⫺, upward maxillary movement (relapse).
Table IV. The mean vertical P-point changes of the cleft maxilla by distraction osteogenesis and orthognathic surgery based on serial cephalometric analyses Changes in the vertical movement of P-point Postoperative period 2-8 weeks (T1) (n) DO ⫽ 22, CO ⫽ 25 8-12 weeks (T2) (n) DO ⫽ 21, CO ⫽ 25 3-6 months (T3) (n) DO ⫽ 21, CO ⫽ 25 6-12 months (T4) (n) DO ⫽ 20, CO ⫽ 24 1-2 years (T5) (n) DO ⫽ 18, CO ⫽ 21 2-3 years (T6) (n) DO ⫽ 17, CO ⫽ 17 3-4 years (T7) (n) DO ⫽ 15, CO ⫽ 12 4-5 years (T8) (n) DO ⫽ 7, CO ⫽ 9 Total upward (⫺) movement Total downward (⫹) movement
Distraction osteogenesis ⴙ 1.20 mm (1.88) ⴙ 0.57 mm (1.31) ⴚ 1.11 mm (2.37) ⫺ 0.13 mm (0.56) ⫹ 0.11 mm (1.08) ⴙ 0.35 mm (0.63) ⫺ 0.10 mm (0.45) ⫺ 0.53 mm (0.76) 1.87 2.12
ⴙ 123.71% ⴙ 58.76% ⴚ 114.43% ⫺ 13.40% ⫹ 11.34% ⴙ 36.08% ⫺ 10.31% ⫺ 54.64% 192.78% 229.89%
Orthognathic surgery ⴙ 0.12 mm (0.92) ⴚ 0.53 mm (1.62) ⴙ 0.35 mm (1.63) ⫹ 0.02 mm (1.37) ⫺ 0.35 mm (0.95) ⴚ 0.30 mm (0.41) ⫺ 0.20 mm (0.28) ⫹ 0.00 mm (0.00) 1.38 0.49
ⴙ 13.64% ⴚ 60.23% ⴙ 39.77% ⫹ 2.27% ⫺ 39.77% ⴚ 34.09% ⫺ 22.73% ⫹ 0.00% 156.82% 55.68%
P value .028* .031* .029* .635 .201 .024* .438 .423
Values in parentheses are standard deviations. Percentages were computed based on the mean horizontal movement of P-point DO (0.97 mm), CO (0.88 mm). *P ⬍ .05. DO, distraction osteogenesis; CO, conventional orthognathic surgery; ⫹, further maxillary downward movement; ⫺, upward maxillary movement (relapse).
horizontal movement of A-point at T1 and T2. A slight decrease (relapse) was noted only at T6. In the CO group, an immediate downward (relapse) trend of the A-point was noted from T1 to T4. This downward movement of A-point starts to slow at T5 until T8. The longitudinal changes were highly significant at time points from T2 to T8 with the DO group being more stable than the CO group. In the horizontal movement of P-point (Table II), the DO group achieved further forward movement of 29.54% at T1, whereas in the CO group, a relapse (backward movement) of 6.51% was observed. In the continuing changes of P-point (Fig. 4, b), the DO group showed an abrupt increase in its horizontal movement at T1, and a slight increase at T2. A similar trend as the A-point can
also be observed wherein there was a slight dip noted at T6, after which a minimal increase could be observed up to T8. In the CO group, a small drop was found at T1. This downward trend continued from T2 until T8. The longitudinal changes of P-point were also highly significant and are similar to A-point (Fig. 4, a and b). Vertical changes. Regarding the vertical movement of A-point in the DO group (Table III), a downward movement of 96.18% and 48.85% at T1 and T6 was noted. However, at T3, there was an upward movement of 32.82%. The opposite was noted in the CO group. There was an initial downward movement of 13.79% and 11.21% during T1 and T3. At T6, there was a relapse (upward movement) of 18.10%. In Fig. 4, c, presenting the longitudinal changes, both the CO and
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Fig. 4. Continuing changes of the cleft maxilla following distraction osteogenesis and orthognathic surgery over 5 years of follow-up. a, Horizontal changes at A-point; b, horizontal changes at P-point; c, vertical changes at A-point; d, vertical changes at P-point.
the DO groups showed an upward trend in the vertical movement of A-point at T1, although the increase for the DO group was twice as much as that of the CO group. From T2 onward, it was noted that the movements achieved by the CO and DO groups were reversed. At T2, the DO group had a further increase; however, the CO group dropped. A slight drop was noted in the DO group, and an increase in the CO group, at both T3 andT4. Thereafter, the DO group started to have an increased trend until T7, and started to drop at T8. In contrast, the CO group was slightly dropping from T4 onward up to T8. In the vertical movement of P-point in the DO group (Table IV), a further downward movement of 123.71%, 58.76%, and 36.08% was noted at T1, T2, and T6. At T3, a relapse (upward movement) of 114.43% was found. In the CO group, further downward movement of 13.64% and 39.77% was noted at T1 and T3. In contrast, there was a relapse (upward movement) of 60.23% and 34.09 at T2 and T6. The percentage relapse for the vertical movement of P-point followed a similar trend when compared with the vertical movement of A-point (Fig. 4, d). The overall correlation between the extent of advancement and relapse of the A-point and P-point
were noted to be low. However, we found that the maxillary advancement was significantly correlated with the amount of relapse at certain postoperative time points: CO group ●
Horizontal relapse of P-point at 2 years postop (P ⫽ .026; r ⫽ ⫺0.522) DO group
● ● ●
Horizontal relapse of A-point at 1 year postop (P ⫽ .019; r ⫽ 0.560) Vertical relapse of A-point at 1 year postop (P ⫽ .008; r ⫽ 0.621) Vertical relapse of P-point at 1 year postop (P ⫽ .028; r ⫽ 0.533)
Angular changes of upper central incisors. There was a gradual increase in the U1 to SN angulation in the CO group (Table V). The U1 to SN angulation of CO became significantly different from DO at the first postoperative year and beyond. This was likely related to the postoperative skeletal relapse and orthodontic compensation wherein the U1 of the CO group became more proclined when compared with the DO group.
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Table V. Angular changes of the upper central incisors (U1) in relation to the Sella-Nasion line (SN) Angular changes of U1 to SN Postoperative period 2 8 3 6 1 2 3 4 5
weeks (n) DO ⫽ 22, CO ⫽ 25 weeks (n) DO ⫽ 21, CO ⫽ 25 months (n) DO ⫽ 21, CO ⫽ 25 months (n) DO ⫽ 20, CO ⫽ 24 years (n) DO ⫽ 18, CO ⫽ 21 years (n) DO ⫽ 17, CO ⫽ 17 years (n) DO ⫽ 15, CO ⫽ 12 years (n) DO ⫽ 15, CO ⫽ 12 years (n) DO ⴝ 7, CO ⴝ 9
Distraction osteogenesis
Orthognathic surgery
P value
104.33° (3.93) 103.89° (3.57) 104.83° (3.27) 104.67° (3.58) 104.85° (2.54) 104.75° (2.14) 105.10° (1.52) 105.11° (1.50) 105.00° (1.49)
105.66° (8.39) 105.58° (7.92) 107.67° (7.87) 108.04° (7.93) 109.30° (8.74) 109.92° (9.12) 112.87° (7.39) 115.28° (5.66) 115.80° (5.72)
.515 .407 .144 .086 .041* .043* .004* .002* .022*
Values in parentheses are standard deviations. *P ⬍ .05. DO, distraction osteogenesis; CO, conventional orthognathic surgery.
DISCUSSION The instability of the Le Fort I maxillary segment in patients with CLP by either distraction or orthognathic surgery manifests skeletally as retrusion of the maxilla because the main direction of surgical movement is forward and downward. Therefore, the backward and upward changes of the maxilla are considered as relapse and, dentally, this relapse in the backward direction will change the preplanned incisal class I occlusion to class III malocclusion. Dental relapse in the upward direction will manifest as loss of incisal show at rest and reduced anterior lower facial height. During the postoperative orthodontic phase, orthodontists normally compensate for the backward dental relapse by proclining the maxillary anterior teeth forward attempting to maintain the teeth in a class I incisal relationship, which was manifested by our finding of an increase in incisal angulation to SN. In this study, 3 of 25 CO patients and only 1 of 22 DO patients relapsed into clinical class III malocclusion despite orthodontic intervention or surgical repositioning. It is worthy to note that there was a significantly larger increase in postsurgical incisal angulation to SN in postoperative year 1 and beyond in the CO group than in the DO group. This occlusal complication correlates well with the more significant backward movement of the maxilla measured cephalometrically on the CO group when compared with the DO group. This study, for the first time in the literature, confirms that DO is more stable than CO by direct comparison with a sufficient sample of cases at different time points up to 5 years. To improve the accuracy of the cephalometric measurement on surgical changes, microscrews were placed in 2 locations of the maxilla for consistent localization of the maxillary landmarks. The precision of this method was confirmed by the cephalometric error analyses. Because the measure-
ment of changes is quite small, extra precautions were taken in the error analyses by evaluating both the reliability and reproducibility of landmark identification and the measurement of surgical movement between 2 selected time periods. This supports the good precision on the point-to-point comparison results between the CO and DO groups, as well as the longitudinal changes of the maxilla between the groups. The surgical relapse of the cleft CO has been well studied and our meta-analysis published in 2005 highlighted that significant relapse can occur in both horizontal and vertical planes.10 The results of our cleft CO cases showed a similar trend with significant relapse occurring within the first postoperative year. The cumulative percentage relapse of the CO group at 5 years in the horizontal plane was 36.99% (Table I). A similar finding was observed by Erbe et al.11 after evaluating 11 patients who received maxillary osteotomy. After a postoperative follow-up of 59 months, they found a relapse rate of 38% to 44%. A number of factors have been correlated with the cause of relapse in patients with CLP. Hochban et al.12 acknowledged that the extent of maxillary deficiency and occlusal disharmony form the main contributing factors for relapse. They also acknowledged that cleft maxilla presented a greater variation in anatomy and requirement for more complicated orthodontic treatment as compared to noncleft patients. Scarring from previous surgery of the lip, alveolus, palate, and pharyngeal repair can inhibit the mobilization of the maxilla during the operation, causing the maxilla to more likely contract after the surgery. In contrast, there are few studies reporting the relapse rate on cleft DO and most have small sample sizes and short follow-up.4 In the literature, the relapse rate reported was much smaller than the CO. This study provides evidence to support that the distracted maxilla
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is stable in patients with CLP and we found that the maxilla actually came farther forward and downward during the initial postoperative period. The stability was maintained in the long term of up to 5 years. In the DO group, the A-point relapsed only 8.24% horizontally at T6. The relapse in the DO group did not seem to have such a great effect because, as we can see from Table I, there was a much larger cumulative forward movement of the maxilla from T1 to T5 and from T7 toT8. When we look at the overall relapse rate, we found a statistically significant difference in the horizontal plane of both the A- and P-points between the CO and DO groups. It showed that the relapse rate of the CO group was higher than in the DO group at 5 years postoperatively (P ⬍ .05). This forward movement of the maxilla could be attributed to the use of elastic traction to control the occlusion during the consolidation period of distraction, when the regenerated callus remains malleable. Lauwers et al.13 reported that elastic can protract the maxilla further forward by 3 mm and provide better occlusion, and it was possible within the first 3 months. Caution is needed when using orthodontic elastics because they may accidentally pull the maxilla downward, which may result in excessive incisal show and incompetent lips.5 The reasons for the significantly smaller relapse in DO when compared with CO is likely related to the gradual surgical movement of the maxilla, which causes less counterforce to pull the maxilla back to the original position. The stability of the distractors also plays a role in resisting the backward and upward pull from the posterior maxillary musculature or scars in the early postoperative period. We believe that the internal distractor, which we selected for this study, is one of the main factors contributing to this success. This is highlighted in the literature. The relapse rate as reported by Rachmiel et al.,14 in a long-term study of cleft maxillary hypoplasia, found a relapse rate of 7.32% after 2 years with the use of internal distractors. Figueroa et al.20 performed the first long-term study over 3 years on maxillary advancement using rigid external distractors (RED) in 17 patients with CLP. They presented the relapse as a change in incisal angulation gained rather than the metric changes in the horizontal and vertical planes. The 10.2° gained in the SNA angle after distraction had gradually decreased 23.5% during the postoperative period. Baek et al.15 conducted a clinical study by comparing the stability between DO and Le Fort I osteotomy in 29 cleft patients with maxillary hypoplasia. In this study, 14 patients had maxillary advancement with Le Fort I osteotomy (group 1), and 11 patients had maxillary distraction using the RED system (group 2). They found that the average amount of relapse in the first and
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second groups was 24% and 21%, respectively. The use of the RED device did not bring any advantage in significantly reducing the relapse rate. This evidence indicates better long-term stability of the transposed maxilla with intraoral distractors than extraoral distractors. This may be related to the way that distraction forces are delivered. Extraoral distractors pull the maxilla forward, whereas intraoral distractors transpose the maxilla forward. We hypothesize that when the extraoral distractors are removed, the tension accumulated from the pulling force tends to rebound resulting in a higher relapse rate. This does not occur with the intraoral distracters, which transpose the maxilla slowly forward with transverse screws on both sides. Hence, intraoral distractors are more stable. Many studies in the literature include children in the distraction groups.14,16 The true extent of relapse in the study reported by Baek et al.15 was unpredictable, as 45.5% of the samples were young patients with incomplete mandibular growth. Because they included both children and mature adults, it was difficult to separate the long-term changes of the maxillary position resulting in surgical relapse from those of facial growth. In addition, if distraction is performed during the growth period, relapse can be exaggerated as a result of continuing mandibular growth. Many of the patients would therefore require another surgery of either CO or DO after the jaw growth matures.17 In our study, this confusion has been eliminated from our research design because all of our patients were considered skeletally mature, having reached age 16 or older and demonstrated radial epiphysis fusion on the hand-wrist radiographs. In children receiving DO, there were reports of some further growth from the distracted maxilla. Harada et al.18 examined the long-term skeletal and dental changes in 2 children and 1 adult with CLP who underwent maxillary distraction using RED. They reported that the long-term skeletal and dental stability was relatively well maintained in the adult patients. Further maxillomandibular growth was observed in the reported children after maxillary distraction. In a follow-up study with a larger sample of children by the same investigators, they confirmed that the maxillary growth was in an inferior direction and the mandibular growth would continue in the AP direction. They recommended that in maxillary distraction of children, the maxillary advancement needs to be overcorrected to reach the estimated adult position to accommodate for the continuing antero-inferior growth of the mandible. The masticatory function of these distracted children would markedly deteriorate for many years until mandibular growth catches up to reach a rea-
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sonably stable dental occlusion. Predicting the mandibular growth of an individual child is impossible with any degree of precision. Hence, a future corrective surgery is likely needed when growth matures. We would not recommend maxillary distraction in children with CLP unless the maxillary retrusion is so severe that it constricts the nasopharyngeal airway presenting as sleep apnea or when children are psychologically depressed. In this study, all the patients with cleft alveolus received alveolar bone grafting at the age of 9 to 10. However, it is possible to conduct distraction in patients with residual alveolar clefts as long as the individual cleft segments are bridged together by miniplates as proposed by Rachmiel et al.19 Otherwise, the buccal segment of the cleft alveolus will move forward hinging on the alveolar cleft space forming a transversely widened dental arch rather than moving the full maxilla forward. CONCLUSION In summary, we have evaluated the long-term stability of DO and CO in patients with CLP up to 5 years. Both techniques can effectively transpose the cleft maxilla forward and downward in correction of moderate maxillary retrusion. The cleft maxilla in the CO group relapsed backward and upward, whereas in the DO group, it advanced more forward and downward over 5 years. The upper incisor angulation following CO increased, whereas following DO, it stayed the same with significant difference between the 2 groups beyond the first postoperative year.
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We thank our patients who were so willing to participate in this study and their committed follow-up attendance. We would also like to acknowledge the contributions of Ms. Vicki Yip, for her assistance with the illustrations, and Mr. Shadow Yeung, who provided statistical assistance.
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Reprint requests: Lim Kwong Cheung, BDS, FRACDS (OMS) Oral & Maxillofacial Surgery 2/F Prince Philip Dental Hospital 34 Hospital Road Hong Kong SAR, China [email protected]