Journal of Cranio-Maxillo-Facial Surgery xxx (2015) 1e7
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Evaluation of bone formation after sagittal split ramus osteotomy using different fixation materials Koichiro Ueki*, Yuri Ishihara, Kunio Yoshizawa, Akinori Moroi, Hiroumi Ikawa, Ran Iguchi, Akihiko Kosaka, Asami Hotta, Takamitsu Tsutsui, Yuriko Saida Department of Oral and Maxillofacial Surgery, Division of Clinical Medicine, Graduate Faculty of Interdisciplinary Research, University of Yamanashi, 1110, Shimokato, Chuoshi 409-3821, Japan
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 28 January 2015 Accepted 9 March 2015 Available online xxx
Purpose: The purpose of this study was to evaluate bony change between the proximal and distal segments after sagittal split ramus osteotomy (SSRO) using different fixation materials. Subjects and methods: The subjects consisted of 74 patients (21 male and 53 female; 148 sides) who underwent SSRO with and without Le Fort I osteotomy. They were divided into five groups: (1) an MT group, mono-cortical titanium plate fixation (26 sides); (2) an MA group, mono-cortical absorbable plate fixation (48 sides); (3) a BA group, bi-cortical absorbable plate fixation (22 sides); (4) an MAa group, mono-cortical plate absorbable fixation with a-tricalcium phosphate (36 sides); and (5) a BAa group, bi-cortical plate absorbable fixation with atricalcium phosphate (16 sides). Ramus square (RmS), ramus width (RmM-RmL) and ramus length (RmA-RmP) at the horizontal plane under the mandibular foramen were assessed pre-operatively, immediately after surgery, and at 1 year after surgery by computed tomography (CT). Results: There were significant differences among the groups regarding change over time in RmS (p ¼ 0.0126) and RmM-RmL (p ¼ 0.0001). However, there was no significant difference among the groups regarding change over time in RmA-RmP. Conclusion: These results suggest that the use of different fixation materials leads to significant differences in the bone healing process after SSRO. © 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Sagittal split ramus osteotomy Fixation material Bone formation Computed tomography
1. Introduction Sagittal split ramus osteotomy (SSRO) is the most common surgical method used for correcting jaw deformities (Trauner and Obwegeser, 1957). We previously used bent plates to secure fragments without a positioning device and found that the bent plate increased the incidence of postoperative temporomandibular dysfunction (TMD) and did not change skeletal or occlusal stability (Ueki et al., 2001, 2008). In this method, the gap between the proximal and distal segments is created by a bent plate, preventing the formation of a large area of bony contact. In setback surgery, especially with asymmetry, fixation between segments can be performed without bony contact to prevent large changes in condylar position and
* Corresponding author. Tel.: þ81 55 273 1111; fax: þ81 55 273 8210. E-mail address: [email protected] (K. Ueki).
angle. The following study showed that the gap between the proximal and distal segments can fill with new bone after SSRO, even when there is little bony contact between segments (Ueki et al., 2009). Recently, an absorbable plate system has been used in orthognathic surgery as well as the titanium plate system, and there have been many studies that proved the usefulness and skeletal stability of the absorbable plate (Ueki et al., 2005, 2006, 2011). However, the absorbable plate system was used in cases where there was a wide space between the bony segments, and also considered whether proper rigidity and stability can be achieved; the combined use of segmental fixation with the absorbable plate system and filling in of the space between the segments were assumed to be clinically necessary. Our previous study using animals proved that the use of an absorbable plate in combination with Biopex (Pentax Co. Tokyo, Japan) was useful in providing adequate bone regeneration (Okabe et al., 2010). The clinical study suggested that inserting Biopex in the gap between the proximal and distal segments was useful for
http://dx.doi.org/10.1016/j.jcms.2015.03.009 1010-5182/© 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Ueki K, et al., Evaluation of bone formation after sagittal split ramus osteotomy using different fixation materials, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.009
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K. Ueki et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2015) 1e7
new bone formation after SSRO with bent plate fixation (Ueki et al., 2012). However, there is no report that compared the bone healing process using different fixation materials. The purpose of this study was to evaluate bony morphological change between the proximal and distal segments after SSRO using various fixation materials. 2. Patients and methods 2.1. Patients The 74 Japanese adults (men: 21, women: 53) enrolled in this study presented with jaw deformities diagnosed as mandibular prognathism with and without maxillary deformity. At the time of orthognathic surgery, the patients ranged in age from 16 to 58 years, with a mean age of 29.7 (standard deviation, 11.1). Although this study was retrospective, informed consent was obtained from the patients and the study was approved by Kanazawa University Hospital and Yamanashi University Hospital. 2.2. Surgery The study sample of 74 patients (148 sides) with mandibular prognathism was divided into five groups: (1) MT group, monocortical titanium plate fixation (26 sides); (2) MA group, monocortical absorbable plate fixation (48 sides); (3) BA group, bicortical absorbable plate fixation (22 sides); (4) MAa group, mono-cortical absorbable plate fixation with a-tricalcium phosphate (36 sides); and (5) BAa group, bi-cortical absorbable plate fixation with a-tricalcium phosphate (16 sides). Although the subjects were divided into five groups according to the fixation methods and materials used in this study, they have changed from 2000 to 2014. In short, the fixation methods and materials used varied over time; this dictated the allocation of patients to a particular group, so the sample numbers for the groups vary. Before surgery, lateral, frontal, and submentalevertex (SeV) cephalograms were obtained as described previously (Ueki et al., 2001). All patients underwent bilateral sagittal split osteotomy (BSSO) setback by the Obwegeser method. Of the 74 patients, 26 underwent Le Fort osteotomy. In the MT group, mono-cortical titanium plate fixation, a long miniplate (4 holes, burr 8 mm, thickness 1.0 mm) and 4 screws (2 14 mm and 2 5 mm) (Universal Mandible fixation module, Stryker Leibinger Co, Freiburg, Germany) were placed in the mandibular angle region. In the MA group, mono-cortical uHA/ PLLA plate fixation, a miniplate (28 4.5 1.5 mm) and 4 screws (2 8 mm) (Fixorb-MX, Takiron Co, Osaka, Japan) were placed in the same region and manner. In the BA group, bi-cortical uHA/PLLA plate fixation, a miniplate (28 4.5 1.5 mm) and 4 screws (2 8 mm) (Fixorb-MX, Takiron Co, Osaka, Japan) were placed in the same region and manner, and 1 screw (2 16 mm) (Fixorb-MX, Takiron Co, Osaka, Japan) was also placed. In the MAa group, monocortical uHA/PLLA plate fixation with a-tricalcium phosphate, a miniplate (28 4.5 1.5 mm) and 4 screws (2 8 mm) (FixorbMX, Takiron Co, Osaka, Japan) were placed in the same region and manner; and a-tricalcium phosphate (Biopex, Pentax Co. Tokyo, Japan) was inserted at the anterior part of the gap between the segments after plate fixation. In the BAa group, bi-cortical uHA/ PLLA plate fixation with a-tricalcium phosphate, miniplate (28 4.5 1.5 mm) and 4 screws (2 8 mm) (Fixorb-MX, Takiron Co, Osaka, Japan) were placed in the same region and manner, and 1 screw (2 16 mm) (Fixorb-MX, Takiron Co, Osaka, Japan) was also -tricalcium phosphate (Biopex) was inserted at the placed; and a anterior part of the gap between the segments after plate fixation.
Before surgery, an SeV cephalogram was obtained for all patients followed by simulation. First, a distal segment including the lower dental arch was set back according to the position of the upper dental arch on the SeV cephalometric trace. When the proximal and distal segments are fixed with straight plates after BSSO, proximal segments containing the condylar head cause internal rotation. To prevent internal rotation of the proximal segments, overlapped cortical bone at the anterior edge of the proximal segment was not removed to keep the contact area between the proximal and distal segments and was fixed with a bent plate and screws in each side of the mandible. At the posterior part, a 3e7 mm gap was maintained between the proximal and distal segments (Ueki et al., 2001, 2008) (Fig. 1). After surgery, elastic traction was placed to maintain ideal occlusion. All patients received orthodontic treatment before and after surgery. CT was taken for all patients pre-operatively, immediately after surgery, and 1 year after surgery. The patients were placed in the gantry with the tragalecanthal line perpendicular to the ground for CT scanning. They were instructed to breathe normally and to avoid swallowing during the scanning process. CT scans were obtained in the radiology department by skilled radiology technicians using a high-speed, advantage-type CT generator (Light Speed Plus; GE Healthcare, Milwaukee, WI, USA) with each sequence taken 1.25 mm apart for 3D reconstruction (120 kV, average 150 mA, 0.7 s/rotation, helical pitch 0.75). The resulting images were stored in the attached workstation computer (Advantage workstation version 4.2; GE Healthcare) and the 3D reconstruction was performed using the volume rendering method. Simplant (Materialise, Leuven, Belgium) was used for morphologic measurements. 2.2.1. Measurements of ramus using CT The RL line was determined as the line between the most anterior points of the auricles bilaterally. The horizontal plane under the mandibular foramen parallel to the FH plane was identified, and ramus area was measured pre- and postoperatively and bilaterally (Ueki et al., 2009) (Figs. 2 and 3).
pre post
Gap
Gap
Fig. 1. Simulation of plate bending. The plates were bent to prevent the proximal segments from rotating internally. Note the gap between the osteotomy surfaces on both sides.
Please cite this article in press as: Ueki K, et al., Evaluation of bone formation after sagittal split ramus osteotomy using different fixation materials, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.009
K. Ueki et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2015) 1e7
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Fig. 2. Measurement of the ramus square (RmS) on a horizontal CT image. A) Pre-operation, RmS shows r1; B) Immediately after surgery, RmS shows r1 and r2; C) After 1 year, RmS shows r1.
1) Ramus square (RmS): the square gave the total area of the proximal plus distal segments, when the image immediately after surgery was measured. 2) Ramus width (RmM-RmL): the distance between the most medial point and the cross point (RmL) between the lateral outline of ramus and the line through the most medial point parallel to the RL line. 3) Ramus length (RmA-RmP): the distance between the most anterior point (RmA) and the most posterior point (RmP) of ramus. All CT images were measured by an author. Fifteen patients were selected randomly and CT images were measured again 10 days later. A paired t-test was applied to the first and second measurements. The difference between the first and second CT measurements was insignificant (p 0.05). 2.3. Statistical analysis Data were statistically analyzed with StatView software, version 4.5 (ABACUS Concepts, Inc., Berkeley, CA, USA) and Dr. SPSSII (SPSS
Japan Inc., Tokyo, Japan). Total change over time, from preoperation to 1 year after surgery was examined by analysis of variance (ANOVA). Comparisons between the groups in each time period were performed and adjusted using the Bonferroni correction. The differences were considered significant at p < 0.05. 3. Results No patients had post-surgical wound infection or dehiscence, bone instability or non-union, or long-term malocclusion. The mean setback amount was 11.5 ± 2.0 mm on the right side and 10.3 ± 3.5 mm on the left side in the MT group, 7.0 ± 2.5 mm on the right side and 6.6 ± 3.1 mm on the left side in the MA group, 7.1 ± 2.8 mm on the right side and 5.9 ± 1.0 mm on the left side in the BA group, 7.0 ± 2.7 mm on the right side and 7.2 ± 2.6 mm on the left side in the MAa group, and 5.6 ± 2.1 mm on the right side and 5.9 ± 1.4 mm on the left side in the BAa group. There was a significant difference among the groups regarding the change in RmS over time (between subject, F ¼ 3.309, df ¼ 4, p ¼ 0.0126, within subject, F ¼ 56.502, df ¼ 2, p < 0.0001). There
Fig. 3. Measurements of ramus length (RmA-RmL) and ramus width (RmM-RmL) on a horizontal CT image. RmA-RmP shows m2. RmM-RmL shows m1. A) Pre-operation; B) Immediately after surgery; C) After 1 year.
Please cite this article in press as: Ueki K, et al., Evaluation of bone formation after sagittal split ramus osteotomy using different fixation materials, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.009
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K. Ueki et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2015) 1e7
was no significant difference among the groups regarding change in RmA-RmP over time. There was a significant difference among the groups regarding change in RmM-RmL over time (between subject, F ¼ 2.936, df ¼ 4, p ¼ 0.0227, within subject, F ¼ 98.955, df ¼ 2, p < 0.0001). In the comparison among the groups in each period, there were significant differences between the MT group and MAa group (p ¼ 0.0013), between the BA group and MAa group (p ¼ 0.0106), and between the MA group and MAa group (p ¼ 0.0069) immediately after surgery in RmS. After 1 year, there was a significant difference between the MA group and MAa group in RmS (p ¼ 0.0050). There was no significant difference in RmM-RmL in any of the periods. Pre-operatively, there was significant difference between the MA group and MAa group in RmA-RmP (p ¼ 0.0022). Immediately after surgery, there were significant differences between the BA group and MAa group (p ¼ 0.0233), and between the MA group and MAa group in RmA-RmP (p ¼ 0.0031). After 1 year, there were significant differences between the BA group and MAa group (p ¼ 0.0092), and between the MA group and MAa group in RmA-RmP (p ¼ 0.0005). In the comparison between time periods in each group, RmS in the MT group showed no significant difference between the preoperative value and that immediately after surgery. However, the value after 1 year was significantly higher than those preoperatively (p ¼ 0.0003) and immediately after surgery (p < 0.0001). Regarding RmM-RmL in the MT group, the value immediately after surgery was significantly higher than that preoperatively (p < 0.0001). The value after 1 year was significantly higher than those pre-operatively (p < 0.0001) and immediately after surgery (p ¼ 0.0177). Regarding RmA-RmP in the MT group, there was no significant difference between the values preoperatively and after 1 year. However, the value immediately after surgery was significantly higher than those pre-operatively (p < 0.0001) and after 1 year (p < 0.0001). Regarding RmS in the MA group, there was no significant difference between the value immediately after surgery and that after 1 year. However, the value pre-operatively was significantly lower than those immediately after surgery (p ¼ 0.0026) and after 1 year (p ¼ 0.0004). Regarding RmM-RmL in the MA group, the value pre-operatively was significantly lower than those immediately after surgery (p < 0.0001) and after 1 year (p < 0.0001). The value after 1 year was significantly higher than that immediately after surgery (p < 0.0001). Regarding RmA-RmP in the MA group, there was no significant difference between the values pre-operatively and after 1 year. However, the value immediately after surgery was significantly higher than those pre-operatively (p < 0.0001) and after 1 year (p < 0.0001). Regarding RmS in the BA group, the value after 1 year was significantly higher than that pre-operatively (p ¼ 0.0006). Regarding RmM-RmL in the BA group, pre-operation values were significantly lower than those immediately after surgery (p < 0.0001) and after 1 year (p ¼ 0.0001). The value immediately after surgery was significantly higher than that after 1 year (p ¼ 0.0025). Regarding RmA-RmL in the BA group, the value immediately after surgery was significantly higher than those preoperatively (p ¼ 0.0041) and after 1 year (p ¼ 0.0002). Regarding RmS in the MAa group, the value pre-operatively was significantly lower than those immediately after (p < 0.0001) and after 1 year (p < 0.0001). Regarding RmM-RmL in the MAa group, the value preoperative was significantly lower than those immediately after surgery (p < 0.0001) and after 1 year (p < 0.0001). The value immediately after surgery was significantly higher than that after 1 year (p < 0.0001). Regarding RmA-RmP in the MAa group, the value pre-operatively was significantly lower than those immediately after surgery (p < 0.0001) and after 1 year (p ¼ 0.0071). The value immediately after surgery was significantly higher than that after 1
year (p < 0.0001). Regarding RmS in the BAa group, the value preoperative was significantly lower than that after 1 year (p ¼ 0.0095). Regarding RmM-RmL in the BAa group, the value preoperative was significantly lower than those immediately after surgery (p ¼ 0.0015) and after 1 year (p ¼ 0.0101). The value immediately after surgery was significantly higher than that after 1 year (p ¼ 0.0246). Regarding RmA-RmP in the BAa group, the value immediately after surgery was significantly higher than those preoperative (p ¼ 0.0137) and after 1 year (p ¼ 0.0011) (Figs. 4e6; Tables 1e3). 4. Discussion Sagittal split ramus osteotomy (SSRO) is used most frequently to correct jaw deformities (Trauner and Obwegeser, 1957). One of the advantages of this method is that formation of a large area of bony contact is possible after either advancement or retrusion of the distal segment. Fixation between segments after SSRO was one of the most discussed and investigated subjects in a previous study (Van Sickels and Richardson, 1996). Various fixation methods, including bicortical screws (Chou et al., 2005; Van Sickels, 1991; Ochs, 2003), miniplates with monocortical screws (Chung et al., 2008; Stoelinga and Borstlap, 2003; Ueki et al., 2001), and a combination of these two techniques (hybrid technique) (Schwartz and Relle, 1996; Tucker and Ochs, 1988) have been reported for bilateral SSRO. Gap healing is intermediate between primary and secondary bone healing (Hutzschenreuter et al., 1969). In the mandible, gap healing is characterized by a plug of healing lamellar bone oriented at a right angle to the long axis of the jaw and derived from the endosteum. A periosteal reaction (external callus) is entirely absent if the bones are rigidly fixed and increases in proportion to the degree of interfragmentary mobility. Gap healing occurs in cortical and cancellous bone when rigid fixation is used and a very small defect exists. Gap healing with endosteal bone proved consistently stronger than secondary bone healing with considerable quantities of periosteal bone. Although no differences could be detected
Pre-operation Immediately after
(mm2) 450
After 1 year
**
**
*
**
*
400 350
300 250 200 150 100
50 0 MT group MA group BA group
MAα group
BAα group
Fig. 4. The result of ramus square (RmS). Error bars show standard deviation. *Significant difference at p 0.05.
Please cite this article in press as: Ueki K, et al., Evaluation of bone formation after sagittal split ramus osteotomy using different fixation materials, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.009
K. Ueki et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2015) 1e7
Pre-operation
Table 1 Ramus square measurements (RmS).
Immediately after
(mm) 25
RmS
(mm2)
Preoperation
Immediately after
After 1 year
MT group
Mean SD Mean SD Mean SD Mean SD Mean SD
224.1 53.0 233.9 66.8 230.7 57.4 231.4 38.9 258.2 57.5
238.2 84.1 257.1 60.8 246.2 66.6 314.8 73.3 277.4 52.4
293.4 85.6 258.0 65.1 274.1 61.9 318.7 73.6 289.1 58.6
After 1 year
* * *
* * *
* * *
* * *
5
*
* *
MA group BA group
20
MAa group BAa group
15
SD indicates standard deviation.
10 Table 2 Ramus width measurements (RmM-RmL).
5 0 MT group MA group BA group
MAα group
BAα group
RmM-RmL
(mm)
Preoperation
Immediately after
After 1 year
MT group
Mean SD Mean SD Mean SD Mean SD Mean SD
11.9 1.7 13.2 2.6 12.2 2.5 12.6 2.4 12.7 2.7
16.4 2.4 17.3 3.5 16.6 2.7 17.0 2.8 15.7 1.8
15.1 2.5 15.0 2.2 14.8 2.5 15.3 2.6 14.3 1.9
MA group BA group
Fig. 5. The result of ramus width (RmM-RmL). Error bars show standard deviation. *Significant difference at p 0.05.
MAa group BAa group
histologically in the quality of the callus, the density of the new bone and the directional orientation of the collagen fibers provide a clue to the differences found in biometric strengths of the healing sites (Reitzik and Schoorl, 1983). Bone healing of setback SSRO seemed to gap healing in nature. A previous study reported that the gap between the proximal and distal segments could fill with new bone after SSRO with titanium or absorbable plates, even if there were few bony contacts between segments (Ueki et al., 2009). The gap between segments in this
Pre-operation Immediately after
(mm) 50
After 1 year
* *
* *
* *
45
* **
* *
40
35
SD indicates standard deviation.
study might be larger than that seen in previous studies, and reflects bone regeneration more than bone healing because of the intentional 3e7 mm gap and the increased square of the ramus. Guided bone regeneration is a surgical procedure that uses barrier membranes to direct growth of new bone at sites with insufficient volumes or dimensions to function or for prosthesis placement (Miloro, 2004). If healing of the periosteal membrane at the incision area is complete, it can prevent invasion of mucosal endothelial cells into the gap between segments. In addition, when bilateral SSRO setback surgery is performed, the overlapped cortical bone decreases in thickness and the cortical bone step disappears by bone remodeling after 1 year, even if the cortical bone is not removed at the anterior site of the proximal segment. In short, it is not always necessary to fit the lateral surface of the distal and proximal segments and remove the step of the cortical bone at the osteotomy line in SSRO (Ueki et al., 2014). Recently, resorbable bone fixation devices (Super-FIXSORB-MX, Takiron Co. Ltd, Osaka, Japan) have been developed for use in
30 Table 3 Ramus length measurements (RmA-RmP).
25 20 15
10
RmA-RmP
(mm)
Preoperation
Immediately after
After 1 year
MT group
Mean SD Mean SD Mean SD Mean SD Mean SD
32.1 3.4 31.2 2.9 31.9 3.9 34.2 3.0 33.0 3.9
35.5 4.9 34.3 4.5 34.1 5.7 38.6 4.6 34.7 4.6
32.6 4.3 31.4 3.9 31.4 5.4 35.7 4.0 32.7 3.8
MA group
5
BA group
0 MT group MA group BA group
MAα group
BAα group
Fig. 6. The result of ramus length (RmA-RmP). Error bars show standard deviation. *Significant difference at p 0.05.
MAa group BAa group
SD indicates standard deviation.
Please cite this article in press as: Ueki K, et al., Evaluation of bone formation after sagittal split ramus osteotomy using different fixation materials, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.009
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K. Ueki et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2015) 1e7
orthopedic or craniofacial, oral and maxillofacial or plastic and reconstructive surgery (Shikinami and Okuno, 1999, 2001; Shikinami and Matsusue Nakamura, 2005). These devices are made from composites of uncalcined and unsintered hydroxyapatite (u-HA) particles and poly-L-lactide (PLLA), and they are produced by a forging process, which is a unique compression molding and machining treatment. They have a modulus of elasticity close to that of natural cortical bone, and they can retain a high strength during the period required for bone healing. They can also show optimal degradation and resorption behavior, osteoconductivity, and bone bonding capability. On the other hand, Monma et al. (1988) have originally developed a self-setting cement-type calcium phosphate material consisting of a-TCP, dicalcium phosphate dibasic (DCPD) and tetracalcium phosphate monoxide (TeCP). According to their extensive studies, this cement-type material could be refined, demonstrating better biocompatibility and direct integration to bone without any participation of peripheral soft tissue (Kurashina et al., 1997a,b; Miyamoto et al., 1995; Yuan et al., 2000). As it is free from infiltration over time of residual monomers of methacrylate resin, which has long been used for orthopedic treatment, this selfsetting cement came to be rapidly targeted for clinical use in Japan. Use of a plate and screw system alone was enough to fix the segments and maintain stability, according to previous reports (Ueki et al., 2001, 2008). However, the absorbable plate system was used in cases where the space between the bony segments was wide, and whether proper rigidity and stability can be achieved was also questioned. Therefore, combined use of segmental fixation with the absorbable plate system and filling in the space between the segments were assumed to be clinically necessary. Our previous study using rabbits suggested that the use of an absorbable plate (Super FIXSORB-MX) in combination with Biopex was useful and both Super FIXSORB-MX and Biopex could provide adequate bone regeneration and maintain strength and stability in the surgical bone space (Okabe et al., 2010; Ueki et al., 2012). In this study, ramus length and width increased immediately after surgery and decreased after 1 year. However, the ramus square increased immediately after surgery, and had increased further after 1 year. This result was due to the measurement method used. Although medial and distal segments were measured in each immediately after surgery, the new bone space between the medial and distal segments was also included in the ramus square after 1 year. Furthermore, the temporary increase in ramus width might be related to the overlapped cortical bone and artificial positioning of the anterior site of the proximal segment with a bent plate. In this study, the decrease in ramus length at 1 year after surgery suggested that the absorption might occur by set back surgery. In contrast, ramus width increased. This indicated that the space between the proximal and distal segments was filled with new bone. This fixation method could not induce a compressive force between the proximal and distal segments. In the previous study (Ueki et al., 2010), although the anterior length was increased by set back of the distal segment, post-operative posterior length was significantly shorter than the pre-operative value in all levels. This suggested that the posterior portion of the ramus could be absorbed after one year. Ramus square measurements in the MAa group were higher than those in the MT, MA and BA groups immediately after surgery. Moreover, the MAa group showed a higher value than the MA group after 1 year. Ramus length in the MAa group was higher than those in the MA and BA groups immediately after surgery. Moreover, the MAa group showed a higher value than the BA group after 1 year. These results might be due to use of Biopex. The ramus square in the groups where Biopex was used was significantly larger than that of the other groups immediately after surgery and
after 1 year. This suggests that insertion of Biopex in the anterior part of the ramus increased the total volume of the ramus and that it can prevent invasion of mucosal endothelial cells into the gap between segments. In a previous study, the Biopex could be absorbed and replaced with new bone. However, the presence of remnant Biopex after 1 year also suggested that the resorption of the Biopex was comparatively slow. 5. Conclusion This study suggested that there were significant differences in the bone healing process after SSRO when using different fixation materials. This result might depend on the use of Biopex much more than the differences between titanium and absorbable plates, and between mono-l and bi-cortical fixation. Competing interests None declared. Ethical approval Not required. References Chou JI, Fong HJ, Kuang SH: A retrospective analysis of the stability and relapse of soft and hard tissue change after bilateral sagittal split osteotomy for mandibular setback of 64 Taiwanese patients. J Oral Maxillofac Surg 63: 355e361, 2005 Chung IH, Yoo CK, Lee EK, Ihm JA, Park CJ, Lim JS, et al: Postoperative stability after sagittal split ramus osteotomies for a mandibular setback with monocortical plate fixation or bicortical screw fixation. J Oral Maxillofac Surg 66: 446e452, 2008 Hutzschenreuter P, Steinemann S, Perren SM: Some effects of rigidity of internal fixation on the healing pattern of osteotomies. Injury 1: 77e81, 1969 Kurashina K, Kurita H, Hirano M, Kotani A, Klein CP, de Groot K: In vivo study of calcium phosphate cements: implantation of an alpha-tricalcium phosphate/ dicalcium phosphate dibasic/tetracalcium phosphate monoxide cement paste. Biomaterials 18: 539e543, 1997a Kurashina K, Kurita H, Kotani A, Takeuchi H, Hirano M: In vivo study of a calcium phosphate cement consisting of alpha-tricalcium phosphate/dicalcium phosphate dibasic/tetracalcium phosphate monoxide. Biomaterials 18: 147e151, 1997b Miloro M: Peterson's principles of oral and maxillofacial surgery, 2nd ed. Hamilton: BC Decker Inc, 2004 Miyamoto Y, Ishikawa K, Fukao H, Sawada M, Asaoka: In vivo setting behavior of fast-setting calcium phosphate cement. Biomaterials 16: 855e860, 1995 Monma H, Ohta K, Takahashi S: A study of the newly developed a-tricalcium phosphate cement. FC Rep 6: 475, 1988 Ochs MW: Bicortical screw stabilization of sagittal split osteotomies. J Oral Maxillofac Surg 61: 1477e1484, 2003 Okabe K, Ueki K, Marukawa K, Mukozawa A, Miyazaki M, Nakagawa K: An experimental study of use of absorbable plate in combination with self-setting alphatricalcium phosphate for orthognathic surgery. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 110: 560e569, 2010 Reitzik M, Schoorl W: Bone repair in the mandible: a histological and biometric comparison between rigid and semi-rigid fixation. J Oral Maxillofac Surg 41: 215e218, 1983 Schwartz HC, Relle RJ: Bicortical-monocortical fixation of the sagittal mandibular osteotomy. J Oral Maxillofac Surg 54: 234e235, 1996 Shikinami Y, Okuno M: Bioresorbable devices made of forged composites of hydroxyapatite (HA) particles and poly-l-lactide (PLLA): part I. Basic characteristics. Biomaterials 20: 859e877, 1999 Shikinami Y, Okuno M: Bioresorbable devices made of forged composites of hydroxyapatite (HA) particles and poly-l-lactide (PLLA): part II. Practical properties of miniscrews and miniplates. Biomaterials 22: 3197e3211, 2001 Shikinami Y, Matsusue Nakamura T: The complete process of bioresorption and bone replacement using devices made of forged composite of raw hydroxyapatite particles/poly L-lactide (F-u-HA/PLLA). Biomaterials 26: 5542e5551, 2005 Stoelinga PJ, Borstlap WA: The fixation of sagittal split osteotomies with miniplates: the versatility of a technique. J Oral Maxillofac Surg 61: 1471e1476, 2003 Trauner R, Obwegeser H: The surgical correction of mandibular prognathism and retrognathia and consideration of genioplasty: surgical procedures to correct mandibular prognathism and reshaping the chin. Oral Surg Oral Med Oral Pathol 10: 677e689, 1957 Tucker M, Ochs M: Use of rigid internal fixation for management of intraoperative complications of mandibular sagittal split osteotomy. Int J Adult Orthodon Orthognath Surg 3: 71e80, 1988
Please cite this article in press as: Ueki K, et al., Evaluation of bone formation after sagittal split ramus osteotomy using different fixation materials, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.009
K. Ueki et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2015) 1e7 Ueki K, Degerliyurt K, Hashiba Y, Marukawa K, Nakagawa K, Yamamoto E: Horizontal changes in the condylar head after sagittal split ramus osteotomy with bent plate fixation. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 106: 656e661, 2008 Ueki K, Hashiba Y, Marukawa K, Okabe K, Nakagawa K, Alam S, et al: Evaluation of bone formation after sagittal split ramus osteotomy with bent plate fixation using computed tomography. J Oral Maxillofac Surg 67: 1062e1068, 2009 Ueki K, Marukawa K, Moroi A, Sotobori M, Ishihara Y, Iguchi R, et al: Evaluation of overlapped cortical bone area after modified plate fixation with bent plate in sagittal split ramus osteotomy. J Craniomaxillofac Surg 42: e210ee216, 2014 Ueki K, Marukawa K, Shimada M, Nakagawa K, Alam S, Yamamoto E: Maxillary stability following Le Fort I osteotomy in combination with sagittal split ramus osteotomy and intraoral vertical ramus osteotomy: a comparative study between titanium miniplate and poly-L-lactic acid plate. J Oral Maxillofac Surg 64: 74e80, 2006 Ueki K, Nakagawa K, Marukawa K, Takazakura D, Shimada M, Takatsuka S, et al: Changes in condylar long axis and skeletal stability after bilateral sagittal split ramus osteotomy with poly-L-lactic acid or titanium plate fixation. Int J Oral Maxillofac Surg 34: 627e634, 2005
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Ueki K, Nakagawa K, Takatsuka S, Yamamoto E: Plate fixation after mandibular osteotomy. Int J Oral Maxillofac Surg 30: 490e496, 2001 Ueki K, Okabe K, Marukawa K, Mukozawa A, Moroi A, Miyazaki M, et al: Effect of self-setting a-tricalcium phosphate between segments for bone healing and hypoaesthesia in lower lip after sagittal split ramus osteotomy. J Craniomaxillofac Surg 40: e119ee124, 2012 Ueki K, Okabe K, Miyazaki M, Mukozawa A, Moroi A, Marukawa K, et al: Skeletal stability after mandibular setback surgery: comparisons among unsintered hydroxyapatite/poly-L-lactic acid plate, poly-L-lactic acid plate, and titanium plate. J Oral Maxillofac Surg 69: 1464e1468, 2011 Ueki K, Okabe K, Miyazaki M, Mukozawa A, Marukawa K, Nakagawa K, et al: Position of mandibular canal and ramus morphology before and after sagittal split ramus osteotomy. J Oral Maxillofac Surg 68: 1795e1801, 2010 Van Sickels: A comparative study of bicortical screws and suspension wires versus bicortical screws in large mandibular advancements. J Oral Maxillofac Surg 49: 1293e1298, 1991 Van Sickels JE, Richardson DA: Stability of orthognathic surgery: a review of rigid fixation. Br J Oral Maxillofac Surg 34: 279e285, 1996 Yuan H, Li T, de Bruijn JD, de Groot K, Zhang X: Tissue response of calcium phosphate cement: a study in dogs. Biomaterials 21: 1283e1290, 2000
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Evaluation of bone formation after sagittal split ramus osteotomy using different fixation materials Koichiro Ueki*, Yuri Ishihara, Kunio Yoshizawa, Akinori Moroi, Hiroumi Ikawa, Ran Iguchi, Akihiko Kosaka, Asami Hotta, Takamitsu Tsutsui, Yuriko Saida Department of Oral and Maxillofacial Surgery, Division of Clinical Medicine, Graduate Faculty of Interdisciplinary Research, University of Yamanashi, 1110, Shimokato, Chuoshi 409-3821, Japan
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 28 January 2015 Accepted 9 March 2015 Available online xxx
Purpose: The purpose of this study was to evaluate bony change between the proximal and distal segments after sagittal split ramus osteotomy (SSRO) using different fixation materials. Subjects and methods: The subjects consisted of 74 patients (21 male and 53 female; 148 sides) who underwent SSRO with and without Le Fort I osteotomy. They were divided into five groups: (1) an MT group, mono-cortical titanium plate fixation (26 sides); (2) an MA group, mono-cortical absorbable plate fixation (48 sides); (3) a BA group, bi-cortical absorbable plate fixation (22 sides); (4) an MAa group, mono-cortical plate absorbable fixation with a-tricalcium phosphate (36 sides); and (5) a BAa group, bi-cortical plate absorbable fixation with atricalcium phosphate (16 sides). Ramus square (RmS), ramus width (RmM-RmL) and ramus length (RmA-RmP) at the horizontal plane under the mandibular foramen were assessed pre-operatively, immediately after surgery, and at 1 year after surgery by computed tomography (CT). Results: There were significant differences among the groups regarding change over time in RmS (p ¼ 0.0126) and RmM-RmL (p ¼ 0.0001). However, there was no significant difference among the groups regarding change over time in RmA-RmP. Conclusion: These results suggest that the use of different fixation materials leads to significant differences in the bone healing process after SSRO. © 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Sagittal split ramus osteotomy Fixation material Bone formation Computed tomography
1. Introduction Sagittal split ramus osteotomy (SSRO) is the most common surgical method used for correcting jaw deformities (Trauner and Obwegeser, 1957). We previously used bent plates to secure fragments without a positioning device and found that the bent plate increased the incidence of postoperative temporomandibular dysfunction (TMD) and did not change skeletal or occlusal stability (Ueki et al., 2001, 2008). In this method, the gap between the proximal and distal segments is created by a bent plate, preventing the formation of a large area of bony contact. In setback surgery, especially with asymmetry, fixation between segments can be performed without bony contact to prevent large changes in condylar position and
* Corresponding author. Tel.: þ81 55 273 1111; fax: þ81 55 273 8210. E-mail address: [email protected] (K. Ueki).
angle. The following study showed that the gap between the proximal and distal segments can fill with new bone after SSRO, even when there is little bony contact between segments (Ueki et al., 2009). Recently, an absorbable plate system has been used in orthognathic surgery as well as the titanium plate system, and there have been many studies that proved the usefulness and skeletal stability of the absorbable plate (Ueki et al., 2005, 2006, 2011). However, the absorbable plate system was used in cases where there was a wide space between the bony segments, and also considered whether proper rigidity and stability can be achieved; the combined use of segmental fixation with the absorbable plate system and filling in of the space between the segments were assumed to be clinically necessary. Our previous study using animals proved that the use of an absorbable plate in combination with Biopex (Pentax Co. Tokyo, Japan) was useful in providing adequate bone regeneration (Okabe et al., 2010). The clinical study suggested that inserting Biopex in the gap between the proximal and distal segments was useful for
http://dx.doi.org/10.1016/j.jcms.2015.03.009 1010-5182/© 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Ueki K, et al., Evaluation of bone formation after sagittal split ramus osteotomy using different fixation materials, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.009
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new bone formation after SSRO with bent plate fixation (Ueki et al., 2012). However, there is no report that compared the bone healing process using different fixation materials. The purpose of this study was to evaluate bony morphological change between the proximal and distal segments after SSRO using various fixation materials. 2. Patients and methods 2.1. Patients The 74 Japanese adults (men: 21, women: 53) enrolled in this study presented with jaw deformities diagnosed as mandibular prognathism with and without maxillary deformity. At the time of orthognathic surgery, the patients ranged in age from 16 to 58 years, with a mean age of 29.7 (standard deviation, 11.1). Although this study was retrospective, informed consent was obtained from the patients and the study was approved by Kanazawa University Hospital and Yamanashi University Hospital. 2.2. Surgery The study sample of 74 patients (148 sides) with mandibular prognathism was divided into five groups: (1) MT group, monocortical titanium plate fixation (26 sides); (2) MA group, monocortical absorbable plate fixation (48 sides); (3) BA group, bicortical absorbable plate fixation (22 sides); (4) MAa group, mono-cortical absorbable plate fixation with a-tricalcium phosphate (36 sides); and (5) BAa group, bi-cortical absorbable plate fixation with a-tricalcium phosphate (16 sides). Although the subjects were divided into five groups according to the fixation methods and materials used in this study, they have changed from 2000 to 2014. In short, the fixation methods and materials used varied over time; this dictated the allocation of patients to a particular group, so the sample numbers for the groups vary. Before surgery, lateral, frontal, and submentalevertex (SeV) cephalograms were obtained as described previously (Ueki et al., 2001). All patients underwent bilateral sagittal split osteotomy (BSSO) setback by the Obwegeser method. Of the 74 patients, 26 underwent Le Fort osteotomy. In the MT group, mono-cortical titanium plate fixation, a long miniplate (4 holes, burr 8 mm, thickness 1.0 mm) and 4 screws (2 14 mm and 2 5 mm) (Universal Mandible fixation module, Stryker Leibinger Co, Freiburg, Germany) were placed in the mandibular angle region. In the MA group, mono-cortical uHA/ PLLA plate fixation, a miniplate (28 4.5 1.5 mm) and 4 screws (2 8 mm) (Fixorb-MX, Takiron Co, Osaka, Japan) were placed in the same region and manner. In the BA group, bi-cortical uHA/PLLA plate fixation, a miniplate (28 4.5 1.5 mm) and 4 screws (2 8 mm) (Fixorb-MX, Takiron Co, Osaka, Japan) were placed in the same region and manner, and 1 screw (2 16 mm) (Fixorb-MX, Takiron Co, Osaka, Japan) was also placed. In the MAa group, monocortical uHA/PLLA plate fixation with a-tricalcium phosphate, a miniplate (28 4.5 1.5 mm) and 4 screws (2 8 mm) (FixorbMX, Takiron Co, Osaka, Japan) were placed in the same region and manner; and a-tricalcium phosphate (Biopex, Pentax Co. Tokyo, Japan) was inserted at the anterior part of the gap between the segments after plate fixation. In the BAa group, bi-cortical uHA/ PLLA plate fixation with a-tricalcium phosphate, miniplate (28 4.5 1.5 mm) and 4 screws (2 8 mm) (Fixorb-MX, Takiron Co, Osaka, Japan) were placed in the same region and manner, and 1 screw (2 16 mm) (Fixorb-MX, Takiron Co, Osaka, Japan) was also -tricalcium phosphate (Biopex) was inserted at the placed; and a anterior part of the gap between the segments after plate fixation.
Before surgery, an SeV cephalogram was obtained for all patients followed by simulation. First, a distal segment including the lower dental arch was set back according to the position of the upper dental arch on the SeV cephalometric trace. When the proximal and distal segments are fixed with straight plates after BSSO, proximal segments containing the condylar head cause internal rotation. To prevent internal rotation of the proximal segments, overlapped cortical bone at the anterior edge of the proximal segment was not removed to keep the contact area between the proximal and distal segments and was fixed with a bent plate and screws in each side of the mandible. At the posterior part, a 3e7 mm gap was maintained between the proximal and distal segments (Ueki et al., 2001, 2008) (Fig. 1). After surgery, elastic traction was placed to maintain ideal occlusion. All patients received orthodontic treatment before and after surgery. CT was taken for all patients pre-operatively, immediately after surgery, and 1 year after surgery. The patients were placed in the gantry with the tragalecanthal line perpendicular to the ground for CT scanning. They were instructed to breathe normally and to avoid swallowing during the scanning process. CT scans were obtained in the radiology department by skilled radiology technicians using a high-speed, advantage-type CT generator (Light Speed Plus; GE Healthcare, Milwaukee, WI, USA) with each sequence taken 1.25 mm apart for 3D reconstruction (120 kV, average 150 mA, 0.7 s/rotation, helical pitch 0.75). The resulting images were stored in the attached workstation computer (Advantage workstation version 4.2; GE Healthcare) and the 3D reconstruction was performed using the volume rendering method. Simplant (Materialise, Leuven, Belgium) was used for morphologic measurements. 2.2.1. Measurements of ramus using CT The RL line was determined as the line between the most anterior points of the auricles bilaterally. The horizontal plane under the mandibular foramen parallel to the FH plane was identified, and ramus area was measured pre- and postoperatively and bilaterally (Ueki et al., 2009) (Figs. 2 and 3).
pre post
Gap
Gap
Fig. 1. Simulation of plate bending. The plates were bent to prevent the proximal segments from rotating internally. Note the gap between the osteotomy surfaces on both sides.
Please cite this article in press as: Ueki K, et al., Evaluation of bone formation after sagittal split ramus osteotomy using different fixation materials, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.009
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Fig. 2. Measurement of the ramus square (RmS) on a horizontal CT image. A) Pre-operation, RmS shows r1; B) Immediately after surgery, RmS shows r1 and r2; C) After 1 year, RmS shows r1.
1) Ramus square (RmS): the square gave the total area of the proximal plus distal segments, when the image immediately after surgery was measured. 2) Ramus width (RmM-RmL): the distance between the most medial point and the cross point (RmL) between the lateral outline of ramus and the line through the most medial point parallel to the RL line. 3) Ramus length (RmA-RmP): the distance between the most anterior point (RmA) and the most posterior point (RmP) of ramus. All CT images were measured by an author. Fifteen patients were selected randomly and CT images were measured again 10 days later. A paired t-test was applied to the first and second measurements. The difference between the first and second CT measurements was insignificant (p 0.05). 2.3. Statistical analysis Data were statistically analyzed with StatView software, version 4.5 (ABACUS Concepts, Inc., Berkeley, CA, USA) and Dr. SPSSII (SPSS
Japan Inc., Tokyo, Japan). Total change over time, from preoperation to 1 year after surgery was examined by analysis of variance (ANOVA). Comparisons between the groups in each time period were performed and adjusted using the Bonferroni correction. The differences were considered significant at p < 0.05. 3. Results No patients had post-surgical wound infection or dehiscence, bone instability or non-union, or long-term malocclusion. The mean setback amount was 11.5 ± 2.0 mm on the right side and 10.3 ± 3.5 mm on the left side in the MT group, 7.0 ± 2.5 mm on the right side and 6.6 ± 3.1 mm on the left side in the MA group, 7.1 ± 2.8 mm on the right side and 5.9 ± 1.0 mm on the left side in the BA group, 7.0 ± 2.7 mm on the right side and 7.2 ± 2.6 mm on the left side in the MAa group, and 5.6 ± 2.1 mm on the right side and 5.9 ± 1.4 mm on the left side in the BAa group. There was a significant difference among the groups regarding the change in RmS over time (between subject, F ¼ 3.309, df ¼ 4, p ¼ 0.0126, within subject, F ¼ 56.502, df ¼ 2, p < 0.0001). There
Fig. 3. Measurements of ramus length (RmA-RmL) and ramus width (RmM-RmL) on a horizontal CT image. RmA-RmP shows m2. RmM-RmL shows m1. A) Pre-operation; B) Immediately after surgery; C) After 1 year.
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was no significant difference among the groups regarding change in RmA-RmP over time. There was a significant difference among the groups regarding change in RmM-RmL over time (between subject, F ¼ 2.936, df ¼ 4, p ¼ 0.0227, within subject, F ¼ 98.955, df ¼ 2, p < 0.0001). In the comparison among the groups in each period, there were significant differences between the MT group and MAa group (p ¼ 0.0013), between the BA group and MAa group (p ¼ 0.0106), and between the MA group and MAa group (p ¼ 0.0069) immediately after surgery in RmS. After 1 year, there was a significant difference between the MA group and MAa group in RmS (p ¼ 0.0050). There was no significant difference in RmM-RmL in any of the periods. Pre-operatively, there was significant difference between the MA group and MAa group in RmA-RmP (p ¼ 0.0022). Immediately after surgery, there were significant differences between the BA group and MAa group (p ¼ 0.0233), and between the MA group and MAa group in RmA-RmP (p ¼ 0.0031). After 1 year, there were significant differences between the BA group and MAa group (p ¼ 0.0092), and between the MA group and MAa group in RmA-RmP (p ¼ 0.0005). In the comparison between time periods in each group, RmS in the MT group showed no significant difference between the preoperative value and that immediately after surgery. However, the value after 1 year was significantly higher than those preoperatively (p ¼ 0.0003) and immediately after surgery (p < 0.0001). Regarding RmM-RmL in the MT group, the value immediately after surgery was significantly higher than that preoperatively (p < 0.0001). The value after 1 year was significantly higher than those pre-operatively (p < 0.0001) and immediately after surgery (p ¼ 0.0177). Regarding RmA-RmP in the MT group, there was no significant difference between the values preoperatively and after 1 year. However, the value immediately after surgery was significantly higher than those pre-operatively (p < 0.0001) and after 1 year (p < 0.0001). Regarding RmS in the MA group, there was no significant difference between the value immediately after surgery and that after 1 year. However, the value pre-operatively was significantly lower than those immediately after surgery (p ¼ 0.0026) and after 1 year (p ¼ 0.0004). Regarding RmM-RmL in the MA group, the value pre-operatively was significantly lower than those immediately after surgery (p < 0.0001) and after 1 year (p < 0.0001). The value after 1 year was significantly higher than that immediately after surgery (p < 0.0001). Regarding RmA-RmP in the MA group, there was no significant difference between the values pre-operatively and after 1 year. However, the value immediately after surgery was significantly higher than those pre-operatively (p < 0.0001) and after 1 year (p < 0.0001). Regarding RmS in the BA group, the value after 1 year was significantly higher than that pre-operatively (p ¼ 0.0006). Regarding RmM-RmL in the BA group, pre-operation values were significantly lower than those immediately after surgery (p < 0.0001) and after 1 year (p ¼ 0.0001). The value immediately after surgery was significantly higher than that after 1 year (p ¼ 0.0025). Regarding RmA-RmL in the BA group, the value immediately after surgery was significantly higher than those preoperatively (p ¼ 0.0041) and after 1 year (p ¼ 0.0002). Regarding RmS in the MAa group, the value pre-operatively was significantly lower than those immediately after (p < 0.0001) and after 1 year (p < 0.0001). Regarding RmM-RmL in the MAa group, the value preoperative was significantly lower than those immediately after surgery (p < 0.0001) and after 1 year (p < 0.0001). The value immediately after surgery was significantly higher than that after 1 year (p < 0.0001). Regarding RmA-RmP in the MAa group, the value pre-operatively was significantly lower than those immediately after surgery (p < 0.0001) and after 1 year (p ¼ 0.0071). The value immediately after surgery was significantly higher than that after 1
year (p < 0.0001). Regarding RmS in the BAa group, the value preoperative was significantly lower than that after 1 year (p ¼ 0.0095). Regarding RmM-RmL in the BAa group, the value preoperative was significantly lower than those immediately after surgery (p ¼ 0.0015) and after 1 year (p ¼ 0.0101). The value immediately after surgery was significantly higher than that after 1 year (p ¼ 0.0246). Regarding RmA-RmP in the BAa group, the value immediately after surgery was significantly higher than those preoperative (p ¼ 0.0137) and after 1 year (p ¼ 0.0011) (Figs. 4e6; Tables 1e3). 4. Discussion Sagittal split ramus osteotomy (SSRO) is used most frequently to correct jaw deformities (Trauner and Obwegeser, 1957). One of the advantages of this method is that formation of a large area of bony contact is possible after either advancement or retrusion of the distal segment. Fixation between segments after SSRO was one of the most discussed and investigated subjects in a previous study (Van Sickels and Richardson, 1996). Various fixation methods, including bicortical screws (Chou et al., 2005; Van Sickels, 1991; Ochs, 2003), miniplates with monocortical screws (Chung et al., 2008; Stoelinga and Borstlap, 2003; Ueki et al., 2001), and a combination of these two techniques (hybrid technique) (Schwartz and Relle, 1996; Tucker and Ochs, 1988) have been reported for bilateral SSRO. Gap healing is intermediate between primary and secondary bone healing (Hutzschenreuter et al., 1969). In the mandible, gap healing is characterized by a plug of healing lamellar bone oriented at a right angle to the long axis of the jaw and derived from the endosteum. A periosteal reaction (external callus) is entirely absent if the bones are rigidly fixed and increases in proportion to the degree of interfragmentary mobility. Gap healing occurs in cortical and cancellous bone when rigid fixation is used and a very small defect exists. Gap healing with endosteal bone proved consistently stronger than secondary bone healing with considerable quantities of periosteal bone. Although no differences could be detected
Pre-operation Immediately after
(mm2) 450
After 1 year
**
**
*
**
*
400 350
300 250 200 150 100
50 0 MT group MA group BA group
MAα group
BAα group
Fig. 4. The result of ramus square (RmS). Error bars show standard deviation. *Significant difference at p 0.05.
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K. Ueki et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2015) 1e7
Pre-operation
Table 1 Ramus square measurements (RmS).
Immediately after
(mm) 25
RmS
(mm2)
Preoperation
Immediately after
After 1 year
MT group
Mean SD Mean SD Mean SD Mean SD Mean SD
224.1 53.0 233.9 66.8 230.7 57.4 231.4 38.9 258.2 57.5
238.2 84.1 257.1 60.8 246.2 66.6 314.8 73.3 277.4 52.4
293.4 85.6 258.0 65.1 274.1 61.9 318.7 73.6 289.1 58.6
After 1 year
* * *
* * *
* * *
* * *
5
*
* *
MA group BA group
20
MAa group BAa group
15
SD indicates standard deviation.
10 Table 2 Ramus width measurements (RmM-RmL).
5 0 MT group MA group BA group
MAα group
BAα group
RmM-RmL
(mm)
Preoperation
Immediately after
After 1 year
MT group
Mean SD Mean SD Mean SD Mean SD Mean SD
11.9 1.7 13.2 2.6 12.2 2.5 12.6 2.4 12.7 2.7
16.4 2.4 17.3 3.5 16.6 2.7 17.0 2.8 15.7 1.8
15.1 2.5 15.0 2.2 14.8 2.5 15.3 2.6 14.3 1.9
MA group BA group
Fig. 5. The result of ramus width (RmM-RmL). Error bars show standard deviation. *Significant difference at p 0.05.
MAa group BAa group
histologically in the quality of the callus, the density of the new bone and the directional orientation of the collagen fibers provide a clue to the differences found in biometric strengths of the healing sites (Reitzik and Schoorl, 1983). Bone healing of setback SSRO seemed to gap healing in nature. A previous study reported that the gap between the proximal and distal segments could fill with new bone after SSRO with titanium or absorbable plates, even if there were few bony contacts between segments (Ueki et al., 2009). The gap between segments in this
Pre-operation Immediately after
(mm) 50
After 1 year
* *
* *
* *
45
* **
* *
40
35
SD indicates standard deviation.
study might be larger than that seen in previous studies, and reflects bone regeneration more than bone healing because of the intentional 3e7 mm gap and the increased square of the ramus. Guided bone regeneration is a surgical procedure that uses barrier membranes to direct growth of new bone at sites with insufficient volumes or dimensions to function or for prosthesis placement (Miloro, 2004). If healing of the periosteal membrane at the incision area is complete, it can prevent invasion of mucosal endothelial cells into the gap between segments. In addition, when bilateral SSRO setback surgery is performed, the overlapped cortical bone decreases in thickness and the cortical bone step disappears by bone remodeling after 1 year, even if the cortical bone is not removed at the anterior site of the proximal segment. In short, it is not always necessary to fit the lateral surface of the distal and proximal segments and remove the step of the cortical bone at the osteotomy line in SSRO (Ueki et al., 2014). Recently, resorbable bone fixation devices (Super-FIXSORB-MX, Takiron Co. Ltd, Osaka, Japan) have been developed for use in
30 Table 3 Ramus length measurements (RmA-RmP).
25 20 15
10
RmA-RmP
(mm)
Preoperation
Immediately after
After 1 year
MT group
Mean SD Mean SD Mean SD Mean SD Mean SD
32.1 3.4 31.2 2.9 31.9 3.9 34.2 3.0 33.0 3.9
35.5 4.9 34.3 4.5 34.1 5.7 38.6 4.6 34.7 4.6
32.6 4.3 31.4 3.9 31.4 5.4 35.7 4.0 32.7 3.8
MA group
5
BA group
0 MT group MA group BA group
MAα group
BAα group
Fig. 6. The result of ramus length (RmA-RmP). Error bars show standard deviation. *Significant difference at p 0.05.
MAa group BAa group
SD indicates standard deviation.
Please cite this article in press as: Ueki K, et al., Evaluation of bone formation after sagittal split ramus osteotomy using different fixation materials, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.009
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K. Ueki et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2015) 1e7
orthopedic or craniofacial, oral and maxillofacial or plastic and reconstructive surgery (Shikinami and Okuno, 1999, 2001; Shikinami and Matsusue Nakamura, 2005). These devices are made from composites of uncalcined and unsintered hydroxyapatite (u-HA) particles and poly-L-lactide (PLLA), and they are produced by a forging process, which is a unique compression molding and machining treatment. They have a modulus of elasticity close to that of natural cortical bone, and they can retain a high strength during the period required for bone healing. They can also show optimal degradation and resorption behavior, osteoconductivity, and bone bonding capability. On the other hand, Monma et al. (1988) have originally developed a self-setting cement-type calcium phosphate material consisting of a-TCP, dicalcium phosphate dibasic (DCPD) and tetracalcium phosphate monoxide (TeCP). According to their extensive studies, this cement-type material could be refined, demonstrating better biocompatibility and direct integration to bone without any participation of peripheral soft tissue (Kurashina et al., 1997a,b; Miyamoto et al., 1995; Yuan et al., 2000). As it is free from infiltration over time of residual monomers of methacrylate resin, which has long been used for orthopedic treatment, this selfsetting cement came to be rapidly targeted for clinical use in Japan. Use of a plate and screw system alone was enough to fix the segments and maintain stability, according to previous reports (Ueki et al., 2001, 2008). However, the absorbable plate system was used in cases where the space between the bony segments was wide, and whether proper rigidity and stability can be achieved was also questioned. Therefore, combined use of segmental fixation with the absorbable plate system and filling in the space between the segments were assumed to be clinically necessary. Our previous study using rabbits suggested that the use of an absorbable plate (Super FIXSORB-MX) in combination with Biopex was useful and both Super FIXSORB-MX and Biopex could provide adequate bone regeneration and maintain strength and stability in the surgical bone space (Okabe et al., 2010; Ueki et al., 2012). In this study, ramus length and width increased immediately after surgery and decreased after 1 year. However, the ramus square increased immediately after surgery, and had increased further after 1 year. This result was due to the measurement method used. Although medial and distal segments were measured in each immediately after surgery, the new bone space between the medial and distal segments was also included in the ramus square after 1 year. Furthermore, the temporary increase in ramus width might be related to the overlapped cortical bone and artificial positioning of the anterior site of the proximal segment with a bent plate. In this study, the decrease in ramus length at 1 year after surgery suggested that the absorption might occur by set back surgery. In contrast, ramus width increased. This indicated that the space between the proximal and distal segments was filled with new bone. This fixation method could not induce a compressive force between the proximal and distal segments. In the previous study (Ueki et al., 2010), although the anterior length was increased by set back of the distal segment, post-operative posterior length was significantly shorter than the pre-operative value in all levels. This suggested that the posterior portion of the ramus could be absorbed after one year. Ramus square measurements in the MAa group were higher than those in the MT, MA and BA groups immediately after surgery. Moreover, the MAa group showed a higher value than the MA group after 1 year. Ramus length in the MAa group was higher than those in the MA and BA groups immediately after surgery. Moreover, the MAa group showed a higher value than the BA group after 1 year. These results might be due to use of Biopex. The ramus square in the groups where Biopex was used was significantly larger than that of the other groups immediately after surgery and
after 1 year. This suggests that insertion of Biopex in the anterior part of the ramus increased the total volume of the ramus and that it can prevent invasion of mucosal endothelial cells into the gap between segments. In a previous study, the Biopex could be absorbed and replaced with new bone. However, the presence of remnant Biopex after 1 year also suggested that the resorption of the Biopex was comparatively slow. 5. Conclusion This study suggested that there were significant differences in the bone healing process after SSRO when using different fixation materials. This result might depend on the use of Biopex much more than the differences between titanium and absorbable plates, and between mono-l and bi-cortical fixation. Competing interests None declared. Ethical approval Not required. References Chou JI, Fong HJ, Kuang SH: A retrospective analysis of the stability and relapse of soft and hard tissue change after bilateral sagittal split osteotomy for mandibular setback of 64 Taiwanese patients. J Oral Maxillofac Surg 63: 355e361, 2005 Chung IH, Yoo CK, Lee EK, Ihm JA, Park CJ, Lim JS, et al: Postoperative stability after sagittal split ramus osteotomies for a mandibular setback with monocortical plate fixation or bicortical screw fixation. J Oral Maxillofac Surg 66: 446e452, 2008 Hutzschenreuter P, Steinemann S, Perren SM: Some effects of rigidity of internal fixation on the healing pattern of osteotomies. Injury 1: 77e81, 1969 Kurashina K, Kurita H, Hirano M, Kotani A, Klein CP, de Groot K: In vivo study of calcium phosphate cements: implantation of an alpha-tricalcium phosphate/ dicalcium phosphate dibasic/tetracalcium phosphate monoxide cement paste. Biomaterials 18: 539e543, 1997a Kurashina K, Kurita H, Kotani A, Takeuchi H, Hirano M: In vivo study of a calcium phosphate cement consisting of alpha-tricalcium phosphate/dicalcium phosphate dibasic/tetracalcium phosphate monoxide. Biomaterials 18: 147e151, 1997b Miloro M: Peterson's principles of oral and maxillofacial surgery, 2nd ed. Hamilton: BC Decker Inc, 2004 Miyamoto Y, Ishikawa K, Fukao H, Sawada M, Asaoka: In vivo setting behavior of fast-setting calcium phosphate cement. Biomaterials 16: 855e860, 1995 Monma H, Ohta K, Takahashi S: A study of the newly developed a-tricalcium phosphate cement. FC Rep 6: 475, 1988 Ochs MW: Bicortical screw stabilization of sagittal split osteotomies. J Oral Maxillofac Surg 61: 1477e1484, 2003 Okabe K, Ueki K, Marukawa K, Mukozawa A, Miyazaki M, Nakagawa K: An experimental study of use of absorbable plate in combination with self-setting alphatricalcium phosphate for orthognathic surgery. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 110: 560e569, 2010 Reitzik M, Schoorl W: Bone repair in the mandible: a histological and biometric comparison between rigid and semi-rigid fixation. J Oral Maxillofac Surg 41: 215e218, 1983 Schwartz HC, Relle RJ: Bicortical-monocortical fixation of the sagittal mandibular osteotomy. J Oral Maxillofac Surg 54: 234e235, 1996 Shikinami Y, Okuno M: Bioresorbable devices made of forged composites of hydroxyapatite (HA) particles and poly-l-lactide (PLLA): part I. Basic characteristics. Biomaterials 20: 859e877, 1999 Shikinami Y, Okuno M: Bioresorbable devices made of forged composites of hydroxyapatite (HA) particles and poly-l-lactide (PLLA): part II. Practical properties of miniscrews and miniplates. Biomaterials 22: 3197e3211, 2001 Shikinami Y, Matsusue Nakamura T: The complete process of bioresorption and bone replacement using devices made of forged composite of raw hydroxyapatite particles/poly L-lactide (F-u-HA/PLLA). Biomaterials 26: 5542e5551, 2005 Stoelinga PJ, Borstlap WA: The fixation of sagittal split osteotomies with miniplates: the versatility of a technique. J Oral Maxillofac Surg 61: 1471e1476, 2003 Trauner R, Obwegeser H: The surgical correction of mandibular prognathism and retrognathia and consideration of genioplasty: surgical procedures to correct mandibular prognathism and reshaping the chin. Oral Surg Oral Med Oral Pathol 10: 677e689, 1957 Tucker M, Ochs M: Use of rigid internal fixation for management of intraoperative complications of mandibular sagittal split osteotomy. Int J Adult Orthodon Orthognath Surg 3: 71e80, 1988
Please cite this article in press as: Ueki K, et al., Evaluation of bone formation after sagittal split ramus osteotomy using different fixation materials, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.009
K. Ueki et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2015) 1e7 Ueki K, Degerliyurt K, Hashiba Y, Marukawa K, Nakagawa K, Yamamoto E: Horizontal changes in the condylar head after sagittal split ramus osteotomy with bent plate fixation. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 106: 656e661, 2008 Ueki K, Hashiba Y, Marukawa K, Okabe K, Nakagawa K, Alam S, et al: Evaluation of bone formation after sagittal split ramus osteotomy with bent plate fixation using computed tomography. J Oral Maxillofac Surg 67: 1062e1068, 2009 Ueki K, Marukawa K, Moroi A, Sotobori M, Ishihara Y, Iguchi R, et al: Evaluation of overlapped cortical bone area after modified plate fixation with bent plate in sagittal split ramus osteotomy. J Craniomaxillofac Surg 42: e210ee216, 2014 Ueki K, Marukawa K, Shimada M, Nakagawa K, Alam S, Yamamoto E: Maxillary stability following Le Fort I osteotomy in combination with sagittal split ramus osteotomy and intraoral vertical ramus osteotomy: a comparative study between titanium miniplate and poly-L-lactic acid plate. J Oral Maxillofac Surg 64: 74e80, 2006 Ueki K, Nakagawa K, Marukawa K, Takazakura D, Shimada M, Takatsuka S, et al: Changes in condylar long axis and skeletal stability after bilateral sagittal split ramus osteotomy with poly-L-lactic acid or titanium plate fixation. Int J Oral Maxillofac Surg 34: 627e634, 2005
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Ueki K, Nakagawa K, Takatsuka S, Yamamoto E: Plate fixation after mandibular osteotomy. Int J Oral Maxillofac Surg 30: 490e496, 2001 Ueki K, Okabe K, Marukawa K, Mukozawa A, Moroi A, Miyazaki M, et al: Effect of self-setting a-tricalcium phosphate between segments for bone healing and hypoaesthesia in lower lip after sagittal split ramus osteotomy. J Craniomaxillofac Surg 40: e119ee124, 2012 Ueki K, Okabe K, Miyazaki M, Mukozawa A, Moroi A, Marukawa K, et al: Skeletal stability after mandibular setback surgery: comparisons among unsintered hydroxyapatite/poly-L-lactic acid plate, poly-L-lactic acid plate, and titanium plate. J Oral Maxillofac Surg 69: 1464e1468, 2011 Ueki K, Okabe K, Miyazaki M, Mukozawa A, Marukawa K, Nakagawa K, et al: Position of mandibular canal and ramus morphology before and after sagittal split ramus osteotomy. J Oral Maxillofac Surg 68: 1795e1801, 2010 Van Sickels: A comparative study of bicortical screws and suspension wires versus bicortical screws in large mandibular advancements. J Oral Maxillofac Surg 49: 1293e1298, 1991 Van Sickels JE, Richardson DA: Stability of orthognathic surgery: a review of rigid fixation. Br J Oral Maxillofac Surg 34: 279e285, 1996 Yuan H, Li T, de Bruijn JD, de Groot K, Zhang X: Tissue response of calcium phosphate cement: a study in dogs. Biomaterials 21: 1283e1290, 2000
Please cite this article in press as: Ueki K, et al., Evaluation of bone formation after sagittal split ramus osteotomy using different fixation materials, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.009
