Five-Year Experience Comparing Resorbable to Titanium Miniplate Osteosynthesis in Cleft Lip and Palate Orthognathic Surgery

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1 Five-Year Experience Comparing Resorbable to Titanium Miniplate Osteosynthesis in Cleft Lip and Palate Orthognathic Surgery Constantin A. Landes, M.D., D.M.D., Alexander Ballon, D.M.D. Objective: To evaluate 5-year outcome stability and complications in orthognathic surgery using resorbable versus titanium osteofixation. Patients, Methods: Twenty-two cleft lip and palate maxillary retrognathia cases were operated on using either poly (70L-lactide-co-30DL-lactide) or titanium miniplate osteofixation. All had two-piece Le Fort I maxillary advancement osteotomy, 11 had simultaneous mandibular setback, and 13 had alveolar bone grafts. Results: Average operative movement and postoperative instability recorded for maxillary horizontal movement (A-point-) were 2.5 mm and 2.1 mm for the study group, compared with 6.3 mm and 1.9 mm for the control group. For maxillary vertical movement (ANS-), measured values were 4.9 and mm for the study group and and 0.9 mm for the controls. For mandibular horizontal movement, measured values were 10.7 mm and 2.8 mm for the study group and 1.9 mm and mm for the controls. Gonial angle measures were 7.1 and 3.5 for the study group and 6.7 and 3.1 for the controls. Foreign body granuloma and fistulation occurred in 1 (9%) member of the study group, but was treated successfully with debridement; implant palpability subsided after 24 months. Three (27%) controls required plate removal, but the remaining plates were palpable. Conclusion: In the study group, horizontal maxillary stability appeared inferior to vertical stability, but mandibular stability was more reliable. Because groups were not matched for magnitude or direction of movement, the results of this study are preliminary and should be interpreted cautiously. KEY WORDS: maxillary retrognathia, midfacial hypoplasia, miniplate osteosynthesis, occlusal relapse, orthognathic surgery, poly (70L-lactideco-30DL-lactide), resorbable plates, skeletal relapse Le Fort I osteotomies became standard procedures during the last half of the 20th century and were definitive treatment for conditions such as vertical maxillary excess, midfacial hypoplasia, and anterior open-bite (Poole et al., 1986; Houston and James, 1989; Posnick and Ewing, 1990; Posnick and Tompson, 1995). In cleft lip and palate (CLP) patients, the basic etiology responsible for maxillary retrognathia and class III occlusion is the developmental embryological malformation of oral, palatal, and pharyngeal tissues, combined with scarring after surgical procedures (Adlam et al., 1989; Witzel, 1989; Hochban et al., 1993). Over the course of development, CLP patients also can develop abnormal structural relationships in the oral cavity due to the incomplete alveolar ridge and palate, Dr. Landes is Consultant and Dr. Ballon is Research Fellow, Department of Maxillofacial and Plastic Facial Surgery, Johann-Wolfgang Goethe University Medical Center, Frankfurt, Germany. Submitted November 2004; Accepted March Address correspondence to: Dr. Constantin A. Landes, Kiefer und Plastische Gesichtschirurgie, Haus 21 G, Theodor Stern Kai 7, Frankfurt am Main, Germany. c.landes@lycos.com. oronasal fistulae, a constricted maxillary arch, and crossbite. These structural abnormalities create a combination of specific problems found in CLP patients before orthognathic surgery. These factors may contribute to the difficulties in achieving a stable result (Witzel, 1989; Posnick and Taylor, 1994; Posnick, 2000). erative relapse is a known phenomenon in orthognathic surgery, and depending on its magnitude, may compromise the operative result. This phenomenon is more common in patients with CLP than in other patients with dento-facial deformities (Epker and Wolford, 1976; Freihofer, 1977; Champy, 1980). Plate-fixation and bone grafting to the osteotomy gap have therefore been recommended for better stability in maxillary advancements (Champy, 1980; Adlam et al., 1989; Posnick and Ewing, 1990; Posnick and Taylor, 1994). Resorbable plate osteosyntheses, frequently applied in otherwise dysgnathic collectives (Haers and Sailer, 1998; Edwards et al., 2001a, 2001b; Turvey et al., 2002; Laine et al., 2004) were reported only in a small previous sample that comprised CLP and other malformations with a 2-year follow-up (Landes and Kriener, 2003). These alternative osteosyntheses were not ap- 67

2 68 Cleft Palate Craniofacial Journal, January 2006, Vol. 43 No. 1 plied out of concern for pronounced relapses. The previous report (Landes and Kriener, 2003) neither differentiated relapse-patterns, dependent on operative movement direction and dimension, nor included a control group. The goal of this pilot study was to evaluate maxillary and mandibular stability in patients with CLP who had undergone resorbable fixation of maxillary and mandibular osteotomies. The outcomes were compared with those of a control group that had undergone a similar procedure with titanium fixation. PATIENTS AND METHODS This study compared preoperative, postoperative, and follow-up maxillary and mandibular craniofacial conformation in 22 dysgnathic CLP patients who required orthognathic surgery. All patients underwent maxillary advancement and some simultaneous mandibular setback between 1993 and All received preoperative and postoperative orthodontic treatment for several years. Nine individuals had left-sided unilateral CLP (UCLP), 4 had bilateral CLP (BCLP), and 9 had rightsided UCLP; none had isolated cleft palate or submucous cleft palate. The assignment for resorbable (study group) or titanium (control group) osteosynthesis after 1999, when resorbable implants were available, was exclusively patient-driven. It was mandatory to inform every patient of the two options and to allow a free decision. This approach was decided upon with our institution s board of ethics, because resorbables had proven reliable in other orthognathic surgery cases but were to be first applied to a pilot collective of dysgnathic CLP patients. All patients were thoroughly informed of the benefits (avoidance of metal exposure and removal) and risks (clinically apparent foreign body reaction, instability and relapse, or incomplete disintegration) of resorbable osteosyntheses. All patients except those with severe maxillary retrognathia ( 10-mm sagittal incisal distance) were invited to participate (beginning in 1999), but some preferred standard titanium. Only those patients who accepted the risks were treated with resorbable osteosyntheses; all others received standard titanium miniplates. All patients were available for follow-up; 12 were male (6 in each group) and 10 female (5 in each group). Patient ages ranged from 16 to 37 years at surgery. Eleven (50%) patients had two-piece Le Fort I maxillary advancement only, and 11 (50%) received simultaneous mandibular setback, according to occlusal and esthetic facial proportion. Nine patients received late alveolar bone grafting from resected mandibular cortex, four from the iliac crest. Resorbable Maxillary Osteosynthesis Resorbable maxillary osteosynthesis was accomplished with poly (70L-lactide-co-30DL-lactide) resorbable plates and 2- mm strong screws (3 patients: MacroSorb, MacroPore, San Diego, CA; 8 patients: PolyMax, Synthes, Oberdorf, Switzerland). The brand was changed due to availability problems when the first manufacturer changed distribution politics. Both brands have identical copolymer-basis, identical dimensions, tensile strength, and elastic modulus (see Claes et al., 1996). Alternatively, titanium miniplates and 2-mm strong screws (Leibinger-mini, Tuttlingen, Germany) were used. The operative procedure was performed with 4- to 6-hole L-plates paranasal and at the bilateral infrazygomatic crest, fixed to each segment with two to three 6-mm screws. Two-piece advancement in the study group was supported by an infranasal horizontal plate as a cross-brace with one or two 6-mm-long screws retaining the bone transplant (Fig. 1A through 1D). Mandibular osteosyntheses were fixed by a single plate, proximally with two to three 6-mm screws and distally with 8-mm screws. After the fifth patient, the protocol for mandibular osteosynthesis was changed. The revised protocol entailed the use of two plates rather than one. This change took place because the investigators had noted clinical instability in a different group of patients with dento-facial deformities who had undergone a similar procedure. No bone transplants will further bridge osteotomy gaps as these may falsify the retentive force evinced by the osteosyntheses. Simultaneous late alveolar bone-grafts may, however, be performed. Titanium-osteosynthesis Titanium-osteosynthesis was accomplished with the use of four 4-hole miniplates. The plates were placed at paranasal areas and infrazygomatic crests bilaterally, and fastened with 6-mm screws. MacroSorb included a battery-powered, sterile, single-use heating pen for local plate molding in situ. Sterile warming saline basins (55 C/131 F MacroSorb; 70 C/158 F PolyMax) were used to bend entire plates. These remained flexible for 5 to 7 seconds at glass temperature (50 C/125 F to 70 C/158 F). Burholes were drilled conventionally with a 2.0 mm-diameter burr, and a thread was tapped. Thread and screw diameter were 2.0 mm, plate thickness was 1.2 mm, and plate width was 6 mm. Though the PolyMax tap can be self-drilling in upper and midface craniofacial osteosyntheses, this did not work with the mandibular cortex. Titanium plates were plied for passive fit and fixated conventionally. Patients were left with a soft diet for 6 weeks. From the 7th week, all kinds of food that did not require intense mastication were allowed. No rigid intermaxillary fixation was applied. From the second postoperative day, two to four rubber bands were suspended between canine brackets over an occlusal wafer, to maintain guided occlusion for 4 weeks. Cephalometric analyses compared the preoperative craniofacial conformation (Burstone et al., 1978) with the postoperative situation, 6 months thereafter and every subsequent year (see Figs. 2 through 4). Standard landmarks (Sella,, Porion, Orbitale, Anterior Nasal Spine, Posterior Nasal Spine [the most dorsal projection from the bilateral hard-palate ending, due to absence of a spine and two-piece osteotomy a rather insecure landmark], A-point, B-point, Pogonion, Gnathion, Gonion, Articulare) were defined. For horizontal measurements, landmarks were projected perpendicular to the facial horizontal and their distances measured parallel to the facial horizontal in milli-

3 Landes and Ballon, RESORBABLE OSTEOSYNTHESES IN CLEFT-ASSOCIATED ORTHOGNATHIC SURGERY 69 FIGURE 1 A: Two-piece Le-Fort I advancement with four L-plates bridging the advancement gap at the anterior maxillary sinus wall, with an additional infranasal plate bridging the alveolar defect as a cross-brace in this BCLP situation that was considerably wider on the right side. On the left side, earlier alveolar grafting was successful and the alveolus is continuous. B: Another advancement, similar to 1A. An additional infranasal plate bridged the bilateral alveolar defect as a cross-brace in a wide BCLP situation. C: Identical situation with the transversal plate retaining bilateral cortical bone grafts. D: Lateral aspect of the patient in 1B and 1C showing the right osteosynthesis at the infrazygomatic crest before bone grafting to the alveolar defect. meters. Vertical measurements were performed from the specific landmark parallel to the facial vertical, perpendicular to the facial horizontal. All cephalometries were performed by the second author, who did not perform the surgery, to avoid observer bias. Retest reliability (absolute and relative error in intraindividual measurement) was assessed by having the second author measure all cephalograms twice in a single blind evaluation. The measurement averages were used for further calculation; 20 cephalograms were evaluated by both authors for interindividual absolute and relative error assessments. Effective operative maxillary horizontal movement was defined as the absolute difference between the pre- and postoperative A-point- distance. erative effective instability was assessed from the absolute difference between the followup and the postoperative value. This was done also for PNS- in the dorsal maxilla. For assessment of vertical maxillary movement (impaction or elongation), vertical ANS- and PNS- were used; for horizontal mandibular movement, B-point- and Pogonion- were used; and for change in intrinsic mandibular bend and postoperative assessment of the angular instability, Articulare-Gonion-Gnathion (Gonial angle) was used. All radiograms were made with the identical cephalostat (Phillips Medical Systems, The Netherlands). The analysis software used was OrthoPlan (Orthognathic Treatment Planner, Pacific Coast Software, Moreno Valley, CA) and spreadsheet analyses were performed with Excel RESULTS Eleven bimaxillary procedures (9 study, 2 control group) and 11 isolated Le Fort I osteotomies (9 control, 2 study group) have been followed. Intraindividual standard and relative errors in cephalometric analysis were 1.2 mm and 3.6%, respectively, whereas interindividual errors were 1.6 mm and 4.9%, respectively. Because transversal jaw rotation in lateral cephalograms is difficult to evaluate and does not lend itself to comprehensive data collection, jaw movements were reduced to four two-dimensional vectors. Operative movements for the study group are shown in Table 1, with corresponding values for the control group shown in Table 2.

4 70 Cleft Palate Craniofacial Journal, January 2006, Vol. 43 No. 1 FIGURE 2 Superpositioned serial cephalograms, oriented by anterior cranial base alignment. Although made with the identical equipment, superpositioning interferences and landmark definition insecurities prevailed. These come from minor posture differences, in spite of head-positioning accessories. Posterior nasal spine (PNS) served the projection of the dorsal hard palate margin. FIGURE 3 Superpositioned pre- and postoperative cephalogram-blueprint, with cephalometrics for orthognathic surgery-relevant landmarks (abbreviations), distances, and the outlined Frankfort horizontal. Adequate experience rendered the handling of templates and resorbables as uncomplicated as the bending of titanium miniplates. Unlike the conventional adaptation of titanium miniplates, no extra time was required. Though the resorbable plate diameter was bigger, wound closure was unproblematic and no periosteal incisions were necessary. Screws initially broke 5% of the time, when the thread was not completely cut or was cut oblique to the plate. If a screw head broke during the insertion due to overtightening, a new burhole and thread could be cut easily into the partly inserted screw body and a replacement screw could be tightened. Both systems provided 2.4-mm emergency screws. With three patients, resorbable osteosyntheses were fixed over an osteotomy gap of 5 to 10 mm due to bone elongation and loss of continuity in cortical bend. As an additional cross-brace between the alveolar segments, the infranasal plate proved practical to retain a late alveolar graft, as well. Follow-up ranged from 6 to 137 months (average 31 months). In the study group, radiographic follow-up was (range 6 to 50) months, and clinical follow-up was (range 6 to 62) months. In the control group, radiographic follow-up was (range 12 to 73) months, and clinical follow-up was (range 14 to 137) months. All patients were available for follow-up, but due to geographical mobility and patients schedules, recall was not always regularly possible. Thus, 100% of patients attended 1-year recall; 27%, 2- year recall; 45%, 5-year recall. Patients were radiographed a maximum of 4 times to minimize individual radiation exposure. Clinical examination always took place. All of the patients had pre- and postoperative radiographs; 50% were scheduled 6 months postoperatively; 50%, 1 year postoperatively; and 50% each subsequent year. The study group had absolute postoperative instability as shown in Table 1. Resorbable osteosyntheses appeared less stable in the anterior maxillary horizontal and dorsal maxillary vertical dimension. The dorsal horizontal, anterior vertical maxillary, and the mandibular resorbable fixation appeared more reliable. The control group s corresponding values are shown in Table 2. In the controls, the dorsal maxillary horizontal and vertical position were less reliable. Because PNS is an insecure landmark, the dorsal maxillary movements have to be interpreted with caution. The Pogonion- values were influenced by a genioplasty in four individuals. Foreign body reaction, swelling and fistulation occurred in one (9%) patient with resorbable osteosynthesis, but was successfully treated with curettage and debridement, and plate palpability subsided after 24 months. Titanium plate removal due to infection, palpability, and temperature sensitivity was required in 3 (27%) patients, but remaining plates were palpable at the end of follow-up. DISCUSSION This study evaluated, within a pilot collective, whether upto-date resorbables yield comparable or acceptable outcomes in segment stability when compared with the standard method. Patients with CLP and maxillary hypoplasia are known to have

5 Landes and Ballon, RESORBABLE OSTEOSYNTHESES IN CLEFT-ASSOCIATED ORTHOGNATHIC SURGERY 71 FIGURE 4 Preoperative view of the patient from Figures 2 and 3. A: Lateral. B: Frontal occlusion. C: Six-month postoperative lateral. D: Frontal occlusion. more postoperative relapses than other patients with Angle s Class III conditions. This is due to the scars produced by previous operations (Houston and James, 1989; Posnick and Ewing, 1990; Posnick and Tompson, 1995; Hirano and Suzuki, 2001). In spite of current advances in surgery and timing of orthodontics, maxillary hypoplasia cannot be avoided completely (Ross, 1987). Although resorbable osteosyntheses have been used in orthognathic surgery since 1991 (Laine et al., 2004), detailed study of segmental instability in orthognathic surgery of CLP patients has not been published (Landes and Kriener, 2003). Due to the limited number of patients, the authors were unable to create homogenous groups regarding BCLP or UCLP, age, sex, CLP width, or other similar variables. In spite of this, this small group of patients with CLP represents the typical distribution of patients regarding gender and cleft type

6 72 Cleft Palate Craniofacial Journal, January 2006, Vol. 43 No. 1 TABLE 1 Study Collective Dimension of Absolute Intraoperative Movement and erative ; Differences Between A-point and PNS Movement Come From Maxillary Rotation and Insecurity in PNS Definition; Differences Between B-point and Pg Come from Genioplasty* Gonial Angle ( ) Horizontal Mandibular Movement (mm) Vertical Maxillary Movement (mm) Horizontal Maxillary Movement (mm) Articulare- Gonion- Gnathion Pogonion- B-point- PNS- ANS- PNS- A-point- Patient Number Average *PNS Posterior Nasal Spine; Pg Pogonion; ANS Anterior Nasal Spine. and should allow the authors to obtain preliminary results regarding stability, biocompatibility, and possible untoward effects. Current resorbable osteofixations are made of copolymers, mainly poly L-lactide with poly DL-lactide or polyglycolide. Thus, crystallinity thought to cause very slow resorption and long-standing osteolyses (Suuronen et al., 1998; Kallela et al., 1999) is reduced. Concern regarding sufficient stability concentrated on mandibular osteofixation. In vitro (Maurer et al., 2002) and clinical reports of poly (70L-lactide-co-30DL-lactide), abbreviated P(L/DL)LA (Landes and Kriener, 2003; Laine et al., 2004), and poly (L-lactide-co-glycolide) or PLGA (Edwards et al., 2001) use demonstrated adequate stability without detailed postoperative stability analysis according to operative movement dimension and direction. This study, therefore, measured linear segmental millimeter movements. Although measurement technique is not perfectly comparable, Hirano and Suzuki (2001) advanced A-point 7 mm (range 2 to 13 mm), with a mean relapse of 1.5 mm (range, 7 mm backward relapse to 1.5 mm additional drift ; i.e., postoperative movement in the direction of operative positioning). Houston and James (1989), Hochban et al. (1993), and Posnick and Tompson (1995) reported similar results, emphasizing that instability is related to the magnitude and direction of the surgical movement. The current study group had 2.5 mm (range, to 5mm) A-point advancement and 2.1 mm average instability( 4 mm relapse to 3.8 mm drift), whereas the controls had 6.3 mm (1.4 to 11.6 mm) advancement with 1.9 mm mean instability ( 4.7 mm relapse to 3.8 mm drift). Hirano and Suzuki (2001) reported vertical operative A- point movement from 5 mm intrusion to 7 mm elongation, with 8 mm relapse to 2 mm drift. Resorbables in the current study had 4.9 mm ( 5.8 mm intrusion to 14.2 mm elongation) absolute vertical movement and mm average instability ( 6 to 2 mm), compared with the controls with mm ( 4.9 mm intrusion to 4.5 mm elongation) movement and 0.9 mm ( 0.9 to 3.4 mm) instability. Thus, maxillary advancement in resorbables was less stable than vertical elongation. Other dentofacial deformity samples using titanium osteosyntheses had 7 mm (Hoffmann and Brennan, 2004) and 10 mm (Waite et al., 1996) average maxillary advancement with less relapse: 0.7 to 1.8 mm. P(L/DL)LA osteosyntheses and mm average maxillary advancement (Haers and Sailer, 1998), with less postoperative instability ( mm), and mm average elongation, mm mean relapse, mm average impaction, and 1.2 mm additional intrusion. Similar maxillary advancements were osteosynthesized in vitro in identical manner with P(L/DL)LA (MacroSorb) plates upon polyurethane skulls; advancement gaps were not bridged (Araujo et al., 2001). Retrograde compressive relapse force was simulated by progressive loading through a material-testing machine and disclosed higher elastic resistance in the inferior-superior than the anterioposterior direction (i.e., compression after maxillary elongation was more stable than sagittal compression after advancement, as clinically seen within

7 Landes and Ballon, RESORBABLE OSTEOSYNTHESES IN CLEFT-ASSOCIATED ORTHOGNATHIC SURGERY 73 TABLE 2 Control Collective Dimension of Absolute Intraoperative Movement and erative ; Differences Between A-point and PNS Movement Come From Maxillary Rotation and Insecurity in PNS Definition; Differences Between B-point and Pg Come from Genioplasty* Gonial Angle ( ) Horizontal Mandibular Movement (mm) Vertical Maxillary Movement (mm) Horizontal Maxillary Movement (mm) Articulare- Gonion- Gnathion Pogonion- B-point- PNS- ANS- PNS- A-point- Patient Number Average *PNS Posterior Nasal Spine; Pg Pogonion; ANS Anterior Nasal Spine. this study). P(L/DL)LA revealed lower elastic stiffness compared to titanium, however, it provided adequate maxillary fixation to withstand the force of mastication, according to the authors. Bilateral double plates fixed with 2 to 3 screws in the anterior and posterior mandibular segment maintained reliable stability. In 7 resorbable mandibular osteofixations of 10.7 mm ( 23.4 mm to 4.7 mm) average operative movement at B- point, 2.8 mm ( 4 mm to 4.9 mm) instability occurred, comparable to previous reports in other dentofacial deformities mandibular setbacks (Mobarak et al., 2000); 2 controls with 2.7 mm and 1.2 mm movement did show 1.2 mm and mm relapse. P(L/DL)LA osteosyntheses in other dentofacial deformities (Haers and Sailer, 1998) showed after mm advancement at B-point mm instability. Because the resorbable and control groups were significantly different regarding the magnitude and direction of the surgical movement, differences between the groups regarding instability may be due to the differences in surgical movements. We tried to account for these differences by calculating the ratio between the instability and the surgical movement, but because the surgical movements were small for many patients, this ratio misrepresented a fairly stable clinical result; calculating ratios or percentages appeared inadequate. A statistical test could have been designed to compare instability between the groups while accounting for differences in surgical movement. One possible approach would have been to perform an analysis of covariance adjusting for pre- versus postoperative changes. Another approach would have been to assign a threshold creating two or three categories of surgical movements (e.g., minimal, moderate, large) and then to look at differences between these subgroups. Finally, another method would involve a nonparametric analysis of covariance. Although it might have been possible to develop such a test, the groups were so small that the result most likely would not have been valid. Therefore, only the absolute instability has been reported and the results of this study should be interpreted with caution, because the groups were not matched for such variables as magnitude or direction of movement, age, sex, UCLP, or BCLP. Freihofer (1977), Champy (1980), Houston and James (1989) and Hochban et al. (1993) suggest that sufficient mobilization, albeit scarring, from previous operations in the palate and retromaxillary region may be a preventive measure against relapse. Adequate mobilization and advance with little resistance that did not proportionally increase with the dimension of movement was intended, but maxillary rigidity could not be estimated preoperatively. In contrast to an alternative splint, if a planned advancement could not be reached with little resistance (Hirano and Suzuki, 2001), simultaneous mandibular setback was performed. High resistance was clinically considered to be overstrain to resorbable osteofixations, and therefore, the study group had more bimaxillary procedures. In a noncleft 10-year poly-l-lactide (abbreviated PLLA) and P(L/DL)LA review (Laine et al., 2004), 9% minor complications occurred, including infection (1%), insufficient fixation (2%), granuloma (3%), and fistulation with hyperplasic mu-

8 74 Cleft Palate Craniofacial Journal, January 2006, Vol. 43 No. 1 cosa that subsided after curettage. The current study had 1 (9%) case of foreign body granuloma, sufficiently treated with curettage, evincing sound osseous union upon inspection. Three (27%) controls had plate exposure, temperature sensitivity, or infection and had consecutive metal removal. Palpability of resorbable plates subsided after 2 years; titanium plates were palpable at the end of follow-up. Based upon the principle of orthognathic surgery improving maxillomandibular relationship and occlusion, 9 of 11 (82%) of both groups were clinical successes; 18% did not visibly improve, yet were content with the resulting incisal edge-toedge-occlusion. Hirano and Suzuki (2001) reported 4 (6%) cases, 2 BCLP and 2 UCLP, that relapsed. All had had bimaxillary surgery and relapsed within months; 3 were reoperated and later partially relapsed. Resorbable osteofixation permitted minor elastic jaw mobility up to 6 weeks postoperatively and allowed faster occlusal settling and potentially better condylar repositioning (Edwards et al., 2001; Norholt et al., 2004). Though the study group was small and a preliminary experience, the results encourage further evaluation in a bigger study for more definite instability assessment. Resorbable osteosynthesis horizontal maxillary stability appeared inferior to vertical stability and to other dysgnathic groups without CLP, whereas mandibular stability was more reliable. Because groups were not matched for magnitude or direction of movement, the results of this study should be interpreted with caution. Two-jaw surgery showed more effective relapse prevention, sound postoperative overbite, and better aesthetics. 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