Abstract
The purpose of this study was to compare retrospectively postoperative differences in maxillary stability after Le Fort I osteotomy and fixation with an unsintered hydroxyapatite (u-HA)/poly- l -lactic acid (PLLA) plate with or without self-setting α-tricalcium phosphate (Biopex ® ) as interpositional material. Subjects comprised 45 patients diagnosed with mandibular prognathism with maxillary retrognathism and mandibular prognathism with bimaxillary asymmetry. All patients underwent Le Fort I osteotomy and bilateral sagittal split ramus osteotomy with fixation by uHA/PLLA plates. Patients were divided into 4 groups consisting of 9 maxillary impaction cases with Biopex ® (group 1) to fill the gap between the bone segments, 14 maxillary advancement cases with Biopex ® (group 2), 8 maxillary impaction cases without Biopex ® (group 3) and 14 maxillary advancement cases without Biopex ® (group 4). Changes in cepahalometric parameters at time intervals (1, 3 and 12 months) between the groups were compared. Results showed that stability did not depend on the use or otherwise of Biopex ® .
This is a retrospective study of 45 Japanese adults (18 men, 27 women) presenting with mandibular prognathism with maxillary retrognathism and mandibular prognathism with bimaxillary asymmetry. Poly- l -lactic acid (PLLA) is one of the various types of absorbable materials that have been used for fixation after Le Fort I osteotomy and sagittal split ramus osteotomy (SSRO). PLLA miniplates promote osteosynthesis of the oral and maxillofacial skeleton, and PLLA screws have been used in patients undergoing orthognathic surgery. In the authors’ previous study, they found that PLLA plates and screws (Fixorb ® -MX, Takiron Co., Osaka, Japan) were useful in Le Fort I osteotomy with SSRO and intraoral vertical ramus osteotomy (IVRO), as well as the conventional titanium plate system. A fixation plate system (Super-FIXSORB ® -MX. Takiron Co. Ltd, Osaka, Japan) has been developed for use in orthopaedic or craniofacial, oral and maxillofacial or plastic and reconstructive surgeries. These devices are made from composites of uncalcined and unsintered hydroxyapatite (u-HA) particles and PLLA. They are produced by a forging process, which is a unique compression moulding and machining treatment. They have a modulus of elasticity close to that of natural cortical bone, and retain high strength during the period required for bone healing. They can also show optimal degradation and resorption behaviour, osteoconductivity, and bone bonding capability. The previous study suggested that there were no significant differences in postoperative time-course changes between u-HA/PLLA, PLLA and conventional titanium plate systems in orthognathic surgery.
The previous study showed that bony healing could occur in spaces between the segments of the maxilla and pterygomaxillary regions as well as the region of the anterior and lateral walls in the maxilla, but it is not always complete within 1 year after Le Fort I osteotomy.
To obtain long-term stability, the use of various alternative materials between segments should be considered. Autogenous bone from the iliac crest or rib has been recommended, although freeze dried bone, proplast blocks, and the solid-block form of HA have also been advocated. Recently, self-setting α-tricalcium phosphate (Biopex ® ) (Pentax Co., Tokyo, Japan) has been recognized as a useful bone alternative material.
No comparative study regarding maxillary stability with absorbable plates in combination with bone substitute material has been reported. The purpose of this study was to compare postoperative changes in maxillary stability after Le Fort I osteotomy between groups using a u-HA/PLLA plate with self-setting α-tricalcium phosphate (Biopex ® ) and groups using uHA/PLLA without Biopex ® .
Patients and methods
Subjects comprised 45 Japanese adults (18 men, 27 women) presenting with jaw deformities diagnosed as mandibular prognathism with maxillary retrognathism and mandibular prognathism with bimaxillar asymmetry. At the time of orthognathic surgery, mean patient age ranged from 16 to 48 years, with a mean age and standard deviation of 25.5 ± 7.6 years. This study was retrospective. Informed consent was obtained from the patients and the study was approved by Kanazawa University Hospital.
All 45 patients underwent Le Fort I osteotomy and bilateral SSRO (by the Obwegeser method) to advance or impact the maxilla and set back the mandible. The patients were divided into 4 groups on the basis of movement in A-point that consisted of 9 maxillary impaction cases with Biopex ® (group 1), 14 maxillary advancement cases with Biopex ® (group 2), 8 maxillary impaction cases (group 3) and 14 maxillary advancement cases without material (group 4). The cases in which the postoperative A-point moved anteriorly parallel to the SN plane were defined as advanced cases, and the cases in which the postoperative A-point moved posteriorly parallel and superiorly perpendicular to the SN plane were defined as impaction cases. The impaction cases were diagnosed as mandibular prognathism with bimaxillary asymmetry. These cases underwent unilateral maxillary vertical excess shortening to correct the occlusal cant.
In all patients, 2 uHA/PLLA L-type miniplates (10 mm × 22 mm × 1.4 mm with 4 screws (2 mm × 8 mm), Super-Fixorb ® -MX; Takiron Co., Osaka, Japan) and 2 straight uHA/PLLA plates (28 mm × 4.5 mm × 1.4 mm with 4 screws (2 mm × 8 mm), Super-Fixorb ® -MX; Takiron Co.) were used to fix the maxilla and 2 uHA/PLLA miniplates (28 mm × 4.5 mm × 1.5 mm with 4 screws (2 mm × 8 mm), Super-Fixorb ® -MX; Takiron Co.) were used for bilateral internal fixation of the mandible (the u-HA/PLLA group). In groups 1 and 2, Biopex ® was inserted and covered at the anterior and lateral part of the gap between the segments after plate fixation ( Fig. 1 ). After a few days of inter maxillary fixation (IMF), an elastic was placed to maintain ideal occlusion in the same manner in all the groups.
Cephalographic assessment
All patients underwent lateral and posteroanterior (PA) cephalography to assess skeletal changes at 1, 3, and 12 months postoperative ( Fig. 2 ). To assess maxillary stability, arbitrary points for the anterior nasal spine (ANS), and posterior nasal spine (PNS), point A and incisor edge were defined and measured from the preoperative images, and subsequently transferred to all remaining radiographs. One skilled observer performed all the digitizations to minimize errors in the cephalometric method and that was acceptable for the purposes of this study. Error analysis by digitization and remeasurement of 10 randomly selected cases generated an average error of less than 0.4 mm for the linear measurements and 0.5° for the angular measurements.
Lateral cephalometric analysis included the following measurements: S-A parallel to SN, the distance between point A and sella parallel to the SN plane; S-A perpendicular to SN, the distance between point A and sella perpendicular to the SN plane; S-PNS parallel to SN, the distance between the arbitrary PNS and sella parallel to the SN plane; S-PNS perpendicular to SN, the distance between the arbitrary PNS and sella perpendicular to the SN plane; Mx1-S parallel to SN, the distance between the incisor edge and sella parallel to the SN plane; Mx1-S perpendicular to SN, the distance between the incisor edge and sella perpendicular to the SN plane; S-ANS parallel to SN, the distance between the arbitrary ANS and sella parallel to the SN plane; and S-ANS perpendicular to SN, the distance between the arbitrary ANS and sella perpendicular to the SN plane.
PA cephalometric analysis included: Mx-Md midline, the angle between the ANS-menton line and the line perpendicular to the bilateral zygomatic frontal suture line; and occlusal cant, the angle between Zy-Zy and the line from the most buccal point at the right first molar crown to the most buccal point at the left molar crown.
Statistical analysis
Data were statistically analyzed with StatView software, version 4.5 (ABACUS Concepts, Inc., Berkeley, CA, USA). Each serial period was defined (T1, baseline to 1 month; T2, 1–3 months; T3, 3–12 months) and the differences between measurements were calculated as shown below. Time-dependent changes in the cephalometric measurements were examined using analysis of variance (ANOVA). The data between the groups were analyzed by the multiple comparison method in each period. Differences were considered significant at P < 0.05.
Results
After surgery, no patient experienced complications such as wound infection or dehiscence, bone instability, or long-term malocclusion. Mean setback was 4.6 ± 3.2 mm on the right and 3.5 ± 3.4 mm on the left in group 1, 5.4 ± 4.6 mm on the right and 6.5 ± 4.5 mm on the left in group 2, 6.1 ± 4.0 mm on the right and 3.6 ± 3.4 mm on the left in group 3, and 7.3 ± 2.7 mm on the right and 5.8 ± 3.0 mm on the left in group 4. There was no significant difference between the four groups. Each cephalometric value of T1 showed the detail degree of movement in each site of maxilla ( Tables 1 and 2 ).
| Baseline | 1 month | 3 months | l year | |||||
|---|---|---|---|---|---|---|---|---|
| Mean | SD | Mean | SD | Mean | SD | Mean | SD | |
| Group 1 | ||||||||
| SNA (dg) | 83.4 | 4.4 | 81.5 | 4.2 | 83.6 | 3.8 | 82.5 | 3.6 |
| S-A parallel to SN (mm) | 61.6 | 6.5 | 60.6 | 5.9 | 62.1 | 5.3 | 61.4 | 5.9 |
| S-A perpend SN (mm) | 65.0 | 3.1 | 65.3 | 3.4 | 64.2 | 2.5 | 65.0 | 3.6 |
| S-PNS parallel to SN (mm) | 17.0 | 2.4 | 16.0 | 3.3 | 17.0 | 3.4 | 16.8 | 2.5 |
| S-PNS perpend to SN (mm) | 50.8 | 3.1 | 49.0 | 2.9 | 49.0 | 2.9 | 48.8 | 2.9 |
| mxl-S parallel to SN (mm) | 63.0 | 8.3 | 62.1 | 8.1 | 63.1 | 6.4 | 61.7 | 8.2 |
| mxl-S perpend to SN (mm) | 68.8 | 2.6 | 69.8 | 2.0 | 69.1 | 2.5 | 69.6 | 2.9 |
| S-ANS parallel to SN (mm) | 67.0 | 5.8 | 67.2 | 5.6 | 68.1 | 4.7 | 67.5 | 6.2 |
| S-ANS perpend to SN (mm) | 58.2 | 2.5 | 58.9 | 3.5 | 58.1 | 3.2 | 57.9 | 3.5 |
| Mx-Md Midline (dg) | −0.1 | 4.9 | −1.4 | 1.1 | −0.8 | 1.5 | −0.5 | 1.7 |
| Occlusal cant (dg) | 0.9 | 2.5 | 2.5 | 1.3 | 2.2 | 2.0 | 1.9 | 2.0 |
| Group 2 | ||||||||
| SNA (dg) | 81.3 | 3.7 | 84.4 | 3.0 | 84.2 | 2.7 | 83.8 | 2.6 |
| S-A parallel to SN (mm) | 59.5 | 3.7 | 63.2 | 3.2 | 63.2 | 3.3 | 62.7 | 3.4 |
| S-A perpend SN (mm) | 66.6 | 3.3 | 66.1 | 5.3 | 64.7 | 5.3 | 65.6 | 4.7 |
| S-PNS parallel to SN (mm) | 14.4 | 2.8 | 17.3 | 3.1 | 18.6 | 3.2 | 18.5 | 2.0 |
| S-PNS perpend to SN (mm) | 50.1 | 3.8 | 49.2 | 4.0 | 48.8 | 3.6 | 49.5 | 4.1 |
| mxl-S parallel to SN (mm) | 60.4 | 6.4 | 64.8 | 5.5 | 65.2 | 5.8 | 63.9 | 5.7 |
| mxl-S perpend to SN (mm) | 69.2 | 2.9 | 69.5 | 2.6 | 69.5 | 2.6 | 69.6 | 2.7 |
| S-ANS parallel to SN (mm) | 66.1 | 4.1 | 69.5 | 3.4 | 69.2 | 3.9 | 68.8 | 3.5 |
| S-ANS perpend to SN (mm) | 59.3 | 3.1 | 59.0 | 5.1 | 57.3 | 3.7 | 58.4 | 3.6 |
| Mx-Md Midline (dg) | 0.9 | 6.5 | −0.7 | 1.3 | −0.3 | 1.6 | −1.0 | 1.8 |
| Occlusal cant (dg) | −0.6 | 2.7 | 1.3 | 2.0 | 1.7 | 2.4 | 2.1 | 1.6 |
| Group 3 | ||||||||
| SNA (dg) | 84.0 | 3.5 | 81.9 | 4.5 | 84.6 | 3.2 | 84.7 | 3.6 |
| S-A parallel to SN (mm) | 60.9 | 3.2 | 59.7 | 4.3 | 61.4 | 3.7 | 63.0 | 3.0 |
| S-A perpend SN (mm) | 60.4 | 6.8 | 58.5 | 5.6 | 58.8 | 6.3 | 60.4 | 6.0 |
| S-PNS parallel to SN (mm) | 17.0 | 2.8 | 17.9 | 3.1 | 16.4 | 3.4 | 18.0 | 3.1 |
| S-PNS perpend to SN (mm) | 46.1 | 5.2 | 45.0 | 3.7 | 44.7 | 4.1 | 45.3 | 3.7 |
| mxl-S parallel to SN (mm) | 64.1 | 2.7 | 64.7 | 2.9 | 65.5 | 3.4 | 66.9 | 3.3 |
| mxl-S perpend to SN (mm) | 67.1 | 3.4 | 68.0 | 3.0 | 67.2 | 3.5 | 69.2 | 2.4 |
| S-ANS parallel to SN (mm) | 65.3 | 3.9 | 63.5 | 4.7 | 65.3 | 3.8 | 67.4 | 4.2 |
| S-ANS perpend to SN (mm) | 53.7 | 5.6 | 53.0 | 5.9 | 52.4 | 6.3 | 54.4 | 5.6 |
| Mx-Md Midline (dg) | 3.1 | 4.4 | −0.3 | 2.1 | 0.3 | 2.3 | 1.4 | 3.2 |
| Occlusal cant (dg) | −1.1 | 1.9 | 2.0 | 1.7 | 0.3 | 1.9 | −1.9 | 5.3 |
| Group 4 | ||||||||
| SNA (dg) | 80.3 | 3.6 | 84.0 | 4.7 | 84.8 | 4.1 | 83.3 | 4.1 |
| S-A parallel to SN (mm) | 57.8 | 6.2 | 61.5 | 5.9 | 61.4 | 5.5 | 62.0 | 7.5 |
| S-A perpend SN (mm) | 61.6 | 4.6 | 60.8 | 5.8 | 60.2 | 5.0 | 61.5 | 5.4 |
| S-PNS parallel to SN (mm) | 15.3 | 4.1 | 16.9 | 3.6 | 17.3 | 2.7 | 17.0 | 5.2 |
| S-PNS perpend to SN (mm) | 48.0 | 3.7 | 46.9 | 4.8 | 46.3 | 4.3 | 47.4 | 5.8 |
| mxl-S parallel to SN (mm) | 61.0 | 8.3 | 64.6 | 6.8 | 64.9 | 7.2 | 65.4 | 9.7 |
| mxl-S perpend to SN (mm) | 67.9 | 5.9 | 67.8 | 5.7 | 66.8 | 6.5 | 68.9 | 6.8 |
| S-ANS parallel to SN (mm) | 62.9 | 6.2 | 66.9 | 5.8 | 65.4 | 5.8 | 66.4 | 7.9 |
| S-ANS perpend to SN (mm) | 55.3 | 3.9 | 53.5 | 4.9 | 53.1 | 4.2 | 54.6 | 5.0 |
| Mx-Md Midline (dg) | −0.9 | 4.4 | −1.1 | 1.6 | −1.1 | 2.2 | −0.4 | 1.2 |
| Occlusal cant (dg) | 1.8 | 2.9 | 1.3 | 2.0 | 1.7 | 2.2 | 1.4 | 2.0 |
| T1 | T2 | T3 | ||||
|---|---|---|---|---|---|---|
| Mean | SD | Mean | SD | Mean | SD | |
| Group 1 | ||||||
| SNA (dg) | −1.9a,b | 1.6 | 2.0c | 2.0 | −1.0 | 1.5 |
| S-A parallel to SN (mm) | −1.0e,g | 1.6 | 1.6i | 3.1 | −0.8 | 1.5 |
| S-A perpend SN (mm) | 0.3 | 3.1 | −1.1 | 1.6 | 0.8 | 2.2 |
| S-PNS parallel to SN (mm) | −1.0 | 2.1 | 0.9 | 3.8 | −0.2 | 3.2 |
| S-PNS perpend to SN (mm) | −1.8 | 2.4 | 0.0 | 2.2 | −0.2 | 2.4 |
| mxl-S parallel to SN (mm) | −1.0 | 3.3 | 1.0 | 2.1 | −1.4 | 3.4 |
| mxl-S perpend to SN (mm) | 1.1 | 1.2 | −0.7 | 1.9 | 0.4 | 2.0 |
| S-ANS parallel to SN (mm) | 0.2j,l | 2.0 | 0.9 | 3.3 | −0.6 | 3.0 |
| S-ANS perpend to SN (mm) | 0.7 | 2.7 | −0.8 | 2.7 | −0.3 | 2.7 |
| Mx-Md Midline (dg) | −1.3 | 4.5 | 0.6 | 1.1 | 0.2 | 0.8 |
| Occlusal cant (dg) | 1.6 | 3.3 | −0.3 | 2.6 | −0.2 | 1.9 |
| Group 2 | ||||||
| SNA (dg) | 3.1a | 2.4 | −0.2c,d | 1.1 | −0.5 | 1.6 |
| S-A parallel to SN (mm) | 3.7e,f | 2.9 | −0.1i | 1.1 | −0.4 | 2.1 |
| S-A perpend SN (mm) | −0.5 | 3.5 | −1.4 | 2.2 | 0.9 | 2.5 |
| S-PNS parallel to SN (mm) | 2.8 | 3.2 | 1.3 | 3.1 | −0.1 | 4.2 |
| S-PNS perpend to SN (mm) | −0.9 | 1.4 | −0.4 | 1.6 | 0.7 | 1.6 |
| mxl-S parallel to SN (mm) | 4.4 | 4.7 | 0.4 | 1.6 | −1.3 | 2.7 |
| mxl-S perpend to SN (mm) | 0.4 | 1.2 | 0.0 | 1.2 | 0.1 | 1.1 |
| S-ANS parallel to SN (mm) | 3.4j,k | 2.7 | −0.4 | 1.0 | −0.4 | 2.5 |
| S-ANS perpend to SN (mm) | −0.3 | 3.1 | −1.6 | 2.3 | 1.0 | 2.0 |
| Mx-Md Midline (dg) | −1.6 | 6.1 | 0.4 | 1.4 | −0.7 | 1.8 |
| Occlusal cant (dg) | 1.9 | 2.8 | 0.4 | 1.8 | 0.4 | 2.1 |
| Group 3 | ||||||
| SNA (dg) | −2.1b | 1.7 | 2.7d | 2.4 | 0.1 | 2.0 |
| S-A parallel to SN (mm) | −1.2f,h | 1.8 | 1.7 | 2.4 | 1.6 | 3.2 |
| S-A perpend SN (mm) | −1.9 | 2.7 | 0.4 | 1.9 | 1.6 | 2.9 |
| S-PNS parallel to SN (mm) | 0.9 | 2.1 | −1.5 | 2.4 | 1.7 | 2.5 |
| S-PNS perpend to SN (mm) | −1.1 | 3.8 | −0.3 | 2.4 | 0.6 | 2.1 |
| mxl-S parallel to SN (mm) | 0.6 | 2.0 | 0.8 | 2.1 | 1.4 | 2.9 |
| mxl-S perpend to SN (mm) | 0.8 | 1.0 | −0.8 | 1.9 | 2.1 | 2.7 |
| S-ANS parallel to SN (mm) | −1.8k,m | 2.1 | 1.8n | 2.0 | 2.1 | 3.9 |
| S-ANS perpend to SN (mm) | −0.8 | 3.7 | −0.6 | 2.1 | 2.1 | 2.3 |
| Mx-Md Midline (dg) | −3.3 | 4.1 | 0.6 | 1.5 | 1.1 | 1.7 |
| Occlusal cant (dg) | 3.0 | 2.1 | −1.6 | 2.8 | −2.2 | 6.0 |
| Group 4 | ||||||
| SNA (dg) | 3.7 | 2.5 | 0.8 | 1.7 | −1.4 | 2.5 |
| S-A parallel to SN (mm) | 3.7g,h | 2.7 | −0.1 | 1.7 | 0.6 | 4.5 |
| S-A perpend SN (mm) | −0.8 | 3.7 | −0.6 | 3.0 | 1.3 | 4.3 |
| S-PNS parallel to SN (mm) | 1.7 | 2.9 | 0.3 | 2.5 | −0.3 | 4.4 |
| S-PNS perpend to SN (mm) | −1.1 | 1.8 | −0.5 | 2.0 | 1.0 | 3.8 |
| mxl-S parallel to SN (mm) | 3.6 | 5.2 | 0.3 | 2.6 | 0.5 | 6.1 |
| mxl-S perpend to SN (mm) | −0.2 | 1.6 | −0.9 | 2.1 | 2.0 | 4.1 |
| S-ANS parallel to SN (mm) | 3.9l,m | 2.6 | −1.5n | 2.8 | 1.1 | 5.3 |
| S-ANS perpend to SN (mm) | −1.7 | 3.1 | −0.4 | 2.1 | 1.5 | 4.0 |
| Mx-Md Midline (dg) | −0.1 | 4.3 | 0.0 | 2.4 | 0.7 | 2.2 |
| Occlusal cant (dg) | −0.5 | 4.0 | 0.4 | 2.7 | −0.3 | 2.6 |
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