Abstract
The purpose of this study was to compare postoperative changes in maxillary stability after Le Fort I osteotomy in three groups: with an unsintered hydroxyapatite (u-HA)/poly- l -lactic acid (PLLA) plate; a PLLA plate; and a titanium plate. Subjects comprised 60 Japanese patients diagnosed with mandibular prognathism. All patients underwent Le Fort I osteotomy and bilateral sagittal split ramus osteotomy. All patients were randomized in groups of 20 to a u-HA/PLLA group, a PLLA plate group and a titanium plate group. Changes in postoperative time intervals between the plate groups were compared using lateral and posteroanterior cephalography. The uHA/PLLA group had significantly larger values than the PLLA group regarding change of mx1-S perpendicular to SN between 3 and 12 months (T3) ( P = 0.0269). The uHA/PLLA group had a significantly larger value than the PLLA group regarding change of S–A perpendicular to SN between baseline and 1 month (T1) ( P = 0.0257). There was no significant difference in the other measurements. This study suggests that maxillary stability with satisfactory results could be obtained in the u-HA/PLLA, PLLA plate and titanium plate groups, although there was a slight difference between the u-HA/PLLA and PLLA plate systems in Le Fort I osteotomy.
Comparison of the stability of Le Fort I advancement using biodegradable poly-p-diaxanon thread with titanium miniplates demonstrated good stability of both fixation devices in the anterior–posterior plane, but a tendency to relapse in the vertical dimension.
Poly- l -lactic acid (PLLA) is one of the various absorbable materials that has 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 a previous study, the authors 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. The fixation plate system (Super-FIXSORB ® -MX, Takiron Co., Ltd., Osaka, Japan) has been newly developed for use in orthopaedic or cranio-facial, 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 can 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 material character and strength of each plate were different so it is difficult to make comparisons with other studies that used different plate systems. Therefore, it is important to compare different types of plate systems in a study. In the previous study on stability after SSRO, there were no significant differences in postoperative time-course changes between the u-HA/PLLA plate system, PLLA plate system and conventional titanium plate system. There is no report of a study that examined the stability after Le Fort I osteotomy using the u-HA/PLLA plate system. The present study compared time-course changes in maxillary stability after Le Fort I osteotomy with the u-HA/PLLA plate system, PLLA plate system and conventional titanium plate system.
Patients and methods
The subjects comprised 60 Japanese adults (16 men, 44 women) presenting with jaw deformities diagnosed as mandibular prognathism with maxillary retrognathism. At the time of orthognathic surgery, the patients were 16–48 years of age, with a mean age and standard deviation of 23.9 ± 6.9 years. The operations took place between August 2001 and April 2010. Patients were selected for this study if their pre- and postoperative cephalograms could be obtained and other procedures were not performed. The adequate total sample number calculated by power analysis software (G*Power Version 3.12; program written by Franz Faul, University Kiel, Germany) was more than 54, when the effect size was 0.25. The sample size of 60 in the repeated measure ANOVA in this study was considered to be valid as a prospective study. Informed consent was obtained from the patients and the study was approved by Kanazawa University Hospital. This study was performed according to the guideline of the Helsinki Declaration.
All 60 patients underwent Le Fort I osteotomy and bilateral SSRO (by the Obwegeser method) to advance the maxilla with and without impaction and set back the mandible. The distribution in the direction and amount of maxillary advancement in the three groups was not significantly different. All patients received orthodontic treatment before and after surgery from two orthodontists. All patients underwent surgery performed by two surgeons (K.U. and K.N.).
In 20 (men 9, women 11) of the 60 patients, 2 uHA/PLLA L-type mini-plates (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 advanced maxilla and 2 uHA/PLLA mini-plates (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 (u-HA/PLLA group). The patients in the u-HA/PLLA group ranged in age from 16 to 48 years (mean 26.4 ± 8.6 years).
In 20 patients (men 4, women 16), 2 PLLA L-type mini-plates (10 mm × 22 mm × 1.5 mm with 4 screws (2 mm × 8 mm), Fixorb ® -MX; Takiron Co., Osaka, Japan) and 2 straight PLLA plates (28 mm × 4.5 mm × 1.5 mm with 4 screws (2 mm × 8 mm), Fixorb ® -MX; Takiron Co.) were used to fix the advanced maxilla and 2 PLLA mini-plates (28 mm × 4.5 mm × 1.5 mm with 4 screws (2 mm × 8 mm), Fixorb ® -MX; Takiron Co.) were used for bilateral internal fixation of the mandible (PLLA group). The patients in the PLLA group ranged in age from 16 to 34 years (mean 23.8 ± 6.4 years).
In the remaining 20 patients (men 4, women 16), 2 L-type titanium mini-plates and 2 straight titanium mini-plates (4 holes/thickness 0.55 mm with 4 screws (2 mm × 5 mm), Würzburg titanium miniplate system; Leibinger Co., Freiburg, Germany) were used to fix the advanced maxilla and 2 titanium mini-plates (4 holes/thickness 0.55 mm with 4 screws (2 mm × 7 mm), Würzburg titanium miniplate system, Leibinger Co.) were used for bilateral internal-fixation of mandible (titanium group). The patients in the titanium group ranged in age from 16 to 32 years (mean 21.6 ± 4.4 years).
After a few days of inter maxillary fixation (IMF), elastic was placed to maintain an ideal occlusion in the same manner in all the groups.
All patients underwent lateral and posteroanterior (PA) cephalography to assess skeletal changes at 1, 3, and 12 postoperative months ( Fig. 1 ). 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 digitization to minimize errors and this was acceptable for the purposes of this study. Error analysis by digitization and re-measurement 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.
The lateral cephalometric analysis involved the following measurements. S–A parallel to SN: distance between point A and sella parallel to SN plane. S–A perpendicular to SN: distance between point A and sella perpendicular to SN plane. S–PNS parallel to SN: distance between the arbitrary PNS and sella parallel to SN plane. S–PNS perpendicular to SN: distance between the arbitrary PNS and sella perpendicular to SN plane. mx1–S parallel to SN: distance between the incisor edge and sella parallel to SN plane. mx1–S perpendicular to SN: distance between the incisor edge and sella perpendicular to SN plane. S–ANS parallel to SN: distance between the arbitrary ANS and sella parallel to SN plane. S–ANS perpendicular to SN: distance between the arbitrary ANS and sella perpendicular to SN plane.
The PA cephalometric analysis involved the following measurements. Mx–Md midline: angle between the ANS-Menton line and the line perpendicular to the bilateral zygomatic frontal suture line. Right mx6 to Zy–Zy: distance between the most buccal point at the right molar crown and the line connecting the most lateral points of the bilateral zygomatic arches (Zy–Zy). Left mx6 to Zy–Zy: distance between the most buccal point at the left molar crown and Zy–Zy. Occlusal cant: 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 analysed with StatView software, version 4.5 (ABACUS Concepts, Inc., Berkeley, CA, USA). Each serial period was defined, and the differences between measurements were calculated as: T1 (baseline to 1 month); T2 (1 month to 3 months); T3 (3 months to 1 year).
The statistical calculation with repeated measure analysis of variance (ANOVA) was performed using class category (uHA/PLLA group, PLLA group and titanium group) and time-course (T1, T2 and T3). Comparisons between the three groups in each time period (T1, T2 and T3) were performed using Scheffe’s method. 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. There was no significant difference between the three groups in the distribution of men and women using the χ 2 test. There was no significant difference between the three groups in age using the χ 2 test ( Table 1 ). Mean setback was 6.5 ± 3.5 mm on the right and 6.1 ± 3.7 mm on the left in the uHA/PLLA group, 5.9 ± 3.1 mm on the right and 6.1 ± 2.5 mm on the left in the PLLA group, and 6.3 ± 3.5 mm on the right and 6.0 ± 2.6 mm on the left in the titanium group. There was no significant difference between the three groups using Student’s t -test.
| Number | Age (years) | ||||||
|---|---|---|---|---|---|---|---|
| Total | Men | Women | Mean | SD | Minimum | Maximum | |
| uHA/PLLA group | 20 | 9 | 11 | 26.4 | 8.6 | 16 | 48 |
| PLLA group | 20 | 4 | 16 | 23.8 | 6.4 | 16 | 34 |
| Titanium group | 20 | 4 | 16 | 21.6 | 4.4 | 16 | 32 |
From the results of repeated measure ANOVA, significant differences were identified among the three groups in S–A perpendicular to SN (between subjects; F = 11.310; df = 2; P < 0.0001), mx1–S perpendicular to SN (between subjects; F = 5.712; df = 2; P = 0.0055) and S–ANS perpendicular to SN (between subjects; F = 4.867; df = 2; P = 0.0112) ( Fig. 1 and Tables 2 and 3 ).
| Baseline | 1 month | 3 months | 1 year | |||||
|---|---|---|---|---|---|---|---|---|
| Mean | SD | Mean | SD | Mean | SD | Mean | SD | |
| uHA/PLLA group | ||||||||
| SNA (°) | 81.6 | 2.8 | 82.9 | 3.6 | 83.2 | 2.7 | 83.3 | 3.3 |
| S–A parallel to SN (mm) | 59.9 | 4.0 | 62.1 | 4.8 | 62.3 | 4.3 | 62.8 | 4.9 |
| S–A perpend to SN (mm) | 64.8 | 4.6 | 65.5 | 5.0 | 64.4 | 4.2 | 64.9 | 4.2 |
| S–PNS parallel to SN (mm) | 16.2 | 2.5 | 17.0 | 2.7 | 17.6 | 2.9 | 18.0 | 3.8 |
| S–PNS perpend to SN (mm) | 49.7 | 3.8 | 48.1 | 4.6 | 47.9 | 3.6 | 48.6 | 4.8 |
| mx1–S parallel to SN (mm) | 62.5 | 6.2 | 64.5 | 5.6 | 65.5 | 5.7 | 65.5 | 6.5 |
| mx1–S perpend to SN (mm) | 69.6 | 2.9 | 69.9 | 2.6 | 69.7 | 2.7 | 70.3 | 2.9 |
| S–ANS parallel to SN (mm) | 65.4 | 4.3 | 68.2 | 4.9 | 68.0 | 4.5 | 68.7 | 5.2 |
| S–ANS perpend to SN (mm) | 57.8 | 3.5 | 57.9 | 3.6 | 57.1 | 3.1 | 57.8 | 3.2 |
| Mx–Md midline (°) | −2.1 | 5.6 | −1.0 | 1.8 | −1.3 | 2.1 | −0.9 | 1.9 |
| Right mx6 to Zy–Zy (mm) | 49.5 | 5.9 | 46.8 | 5.3 | 47.4 | 4.2 | 48.5 | 5.5 |
| Left mx6 to Zy–Zy (mm) | 49.9 | 5.8 | 47.5 | 4.7 | 48.7 | 5.2 | 49.8 | 6.1 |
| Occlusal cant (°) | 1.4 | 2.6 | 1.5 | 1.7 | 1.9 | 2.2 | 1.9 | 2.1 |
| PLLA group | ||||||||
| SNA (°) | 80.2 | 5.2 | 81.2 | 2.7 | 82.4 | 2.9 | 82.7 | 3.8 |
| S–A parallel to SN (mm) | 54.5 | 5.7 | 57.0 | 4.9 | 57.9 | 5.1 | 56.9 | 5.0 |
| S–A perpend SN (mm) | 61.2 | 4.6 | 58.6 | 5.3 | 58.6 | 5.1 | 57.2 | 5.0 |
| S–PNS parallel to SN (mm) | 12.9 | 4.2 | 15.2 | 4.3 | 15.0 | 3.8 | 15.0 | 3.2 |
| S–PNS perpend to SN (mm) | 47.7 | 3.5 | 45.1 | 4.0 | 45.5 | 4.0 | 45.5 | 3.7 |
| mx1–S parallel to SN (mm) | 57.6 | 7.0 | 60.3 | 6.1 | 61.4 | 6.9 | 59.8 | 6.3 |
| mx1–S perpend to SN (mm) | 65.6 | 3.7 | 65.5 | 4.1 | 65.1 | 3.7 | 64.2 | 3.8 |
| S–ANS parallel to SN (mm) | 57.6 | 5.1 | 59.6 | 4.4 | 60.5 | 4.8 | 59.9 | 5.2 |
| S–ANS perpend to SN (mm) | 54.5 | 3.9 | 53.3 | 5.2 | 52.5 | 4.6 | 51.8 | 4.5 |
| Mx–Md midline (°) | 1.5 | 4.5 | 0.1 | 2.0 | 0.2 | 2.0 | 0.2 | 2.3 |
| Right mx6 to Zy–Zy (mm) | 47.3 | 5.1 | 45.1 | 5.7 | 44.3 | 5.6 | 43.6 | 5.9 |
| Left mx6 to Zy–Zy (mm) | 48.1 | 4.6 | 46.5 | 5.7 | 45.9 | 4.6 | 44.6 | 6.7 |
| Occlusal cant (°) | −0.1 | 2.4 | 2.4 | 2.8 | 2.1 | 3.0 | 2.4 | 1.8 |
| Titanium group | ||||||||
| SNA (°) | 80.7 | 3.6 | 82.9 | 4.0 | 83.2 | 4.1 | 83.5 | 3.7 |
| S–A parallel to SN (mm) | 58.1 | 6.6 | 60.8 | 6.6 | 61.2 | 6.4 | 61.3 | 6.0 |
| S–A perpend to SN (mm) | 62.7 | 4.0 | 61.8 | 4.7 | 62.6 | 5.0 | 63.0 | 4.5 |
| S–PNS parallel to SN (mm) | 14.1 | 3.7 | 15.9 | 3.6 | 15.7 | 3.4 | 14.9 | 2.6 |
| S–PNS perpend to SN (mm) | 49.3 | 4.0 | 48.0 | 4.6 | 48.2 | 4.2 | 48.6 | 4.4 |
| mx1–S parallel to SN (mm) | 61.8 | 6.6 | 64.6 | 7.1 | 65.4 | 7.6 | 65.0 | 7.3 |
| mx1–S perpend to SN (mm) | 61.4 | 7.1 | 60.8 | 7.3 | 60.7 | 7.9 | 61.0 | 7.3 |
| S–ANS parallel to SN (mm) | 61.1 | 7.5 | 63.4 | 7.1 | 63.6 | 6.8 | 63.9 | 6.5 |
| S–ANS perpend to SN (mm) | 56.9 | 3.9 | 56.1 | 4.2 | 56.7 | 4.5 | 57.0 | 4.3 |
| Mx–Md midline (°) | 2.6 | 7.5 | 1.2 | 2.0 | 0.7 | 2.0 | 1.5 | 1.7 |
| Right mx6 to Zy–Zy (mm) | 45.8 | 5.8 | 44.4 | 6.9 | 46.2 | 5.4 | 45.1 | 5.9 |
| Left mx6 to Zy–Zy (mm) | 47.4 | 7.2 | 45.9 | 6.8 | 46.7 | 5.0 | 46.4 | 5.1 |
| Occlusal cant (°) | −0.2 | 3.5 | 1.5 | 1.9 | 1.2 | 2.0 | 0.8 | 1.6 |
| Degree of freedom | Sum of squares | Mean sum of squares | F -Value | P -Value | |
|---|---|---|---|---|---|
| S–A perpendicular to SN | |||||
| Class | 2 | 79.950 | 39.975 | 11.310 | <0.0001 * |
| Groups residual | 57 | 201.474 | 3.535 | ||
| Category for time course | 2 | 24.161 | 12.080 | 1.076 | 0.344 |
| Category for time course × class | 4 | 102.999 | 25.750 | 2.294 | 0.064 |
| Category for time course × groups residual | 114 | 1279.000 | 11.224 | ||
| mx1–S perpendicular to SN | |||||
| Class | 2 | 15.311 | 7.655 | 5.712 | 0.0055 * |
| Groups | 57 | 76.394 | 1.340 | ||
| Category for time course | 2 | 2.473 | 1.239 | 0.311 | 0.733 |
| Category for time course × class | 4 | 22.060 | 5.515 | 1.384 | 0.244 |
| Category for time course × groups residual | 114 | 454.192 | 3.984 | ||
| ANS–S perpendicular to SN | |||||
| Class | 2 | 34.846 | 17.423 | 4.867 | 0.0112 * |
| Groups | 57 | 204.053 | 3.580 | ||
| Category for time course | 2 | 15.921 | 7.961 | 1.019 | 0.364 |
| Category for time course × class | 4 | 30.563 | 7.641 | 0.978 | 0.423 |
| Category for time course × groups residual | 114 | 890.612 | 7.812 | ||
* Significant differences (between subjects) were identified among the three groups.
From the multiple comparison in each time period, the uHA/PLLA group had a significantly larger value than the PLLA group regarding change of mx1–S perpendicular to SN between 3 and 12 months (T3) ( P = 0.0269). The uHA/PLLA group had a significantly larger value than the PLLA group regarding change of S–A perpendicular to SN between baseline and 1 month (T1) ( P = 0.0257).
No significant differences were identified among the three groups in the other measurements on lateral cephalometric analysis and in all measurements in the PA cephalometric analysis ( Fig. 1 and Tables 2 and 4 ).
| T1 | T2 | T3 | ||||
|---|---|---|---|---|---|---|
| Mean | SD | Mean | SD | Mean | SD | |
| uHA/PLLA group | ||||||
| SNA (°) | 1.3 | 2.6 | 0.3 | 1.9 | 0.0 | 2.0 |
| S–A parallel to SN (mm) | 2.2 | 1.6 | 0.2 | 2.0 | 0.5 | 2.7 |
| S–A perpend to SN (mm) | 0.6 * | 3.2 | −1.1 | 2.1 | 0.4 | 1.9 |
| S–PNS parallel to SN (mm) | 0.8 | 2.3 | 0.6 | 2.9 | 0.4 | 4.2 |
| S–PNS perpend to SN (mm) | −1.6 | 1.9 | −0.1 | 1.9 | 0.6 | 2.1 |
| mx1–S parallel to SN (mm) | 2.0 | 1.9 | 1.1 | 2.0 | 0.0 | 3.1 |
| mx1–S perpend to SN (mm) | 0.3 | 1.2 | −0.3 | 1.5 | 0.6 * | 1.7 |
| S–ANS parallel to SN (mm) | 2.8 | 1.8 | −0.2 | 2.5 | 0.6 | 2.6 |
| S–ANS perpend to SN (mm) | 0.1 | 2.1 | −0.8 | 1.7 | 0.7 | 1.7 |
| Mx–Md midline (°) | 1.1 | 5.2 | −0.3 | 2.0 | 0.4 | 1.9 |
| Right mx6 to Zy–Zy (mm) | −2.7 | 4.9 | 0.6 | 3.2 | 1.1 | 3.1 |
| Left mx6 to Zy–Zy (mm) | −2.4 | 5.2 | 1.2 | 3.9 | 1.1 | 4.2 |
| Occlusal cant (°) | 0.2 | 3.0 | 0.3 | 2.5 | 0.0 | 2.2 |
| PLLA group | ||||||
| SNA (°) | 1.1 | 4.5 | 1.2 | 2.5 | 0.3 | 2.3 |
| S–A parallel to SN (mm) | 2.5 | 2.6 | 0.8 | 3.2 | −1.0 | 1.3 |
| S–A perpend to SN (mm) | −2.6 * | 4.7 | 0.0 | 2.1 | −1.4 | 1.5 |
| S–PNS parallel to SN (mm) | 2.3 | 3.5 | −0.2 | 2.7 | 0.0 | 2.3 |
| S–PNS perpend to SN (mm) | −2.7 | 2.9 | 0.4 | 1.2 | 0.1 | 1.1 |
| mx1–S parallel to SN (mm) | 2.8 | 3.3 | 1.0 | 3.0 | −1.5 | 2.2 |
| mx1–S perpend to SN (mm) | −0.1 | 2.9 | −0.4 | 1.1 | −0.9 * | 1.6 |
| S–ANS parallel to SN (mm) | 2.0 | 2.2 | 0.9 | 3.0 | −0.7 | 2.1 |
| S–ANS perpend to SN (mm) | −1.3 | 4.1 | −0.8 | 2.5 | −0.8 | 1.6 |
| Mx–Md midline (°) | −1.4 | 3.9 | 0.1 | 1.6 | −0.1 | 1.9 |
| Right mx6 to Zy–Zy (mm) | −2.2 | 4.5 | −0.8 | 2.9 | −0.7 | 6.3 |
| Left mx6 to Zy–Zy (mm) | −1.6 | 5.1 | −0.6 | 3.7 | −1.3 | 6.6 |
| Occlusal cant (°) | 2.5 | 3.8 | −0.3 | 3.1 | 0.2 | 2.5 |
| Titanium group | ||||||
| SNA (°) | 2.2 | 2.9 | 0.3 | 3.5 | 0.3 | 2.7 |
| S–A parallel to SN (mm) | 2.7 | 2.6 | 0.4 | 3.5 | 0.2 | 3.1 |
| S–A perpend to SN (mm) | −0.8 | 2.9 | 0.7 | 3.2 | 0.4 | 3.6 |
| S–PNS parallel to SN (mm) | 1.8 | 4.0 | −0.2 | 2.8 | −0.8 | 2.2 |
| S–PNS perpen to SN (mm) | −1.3 | 2.1 | 0.2 | 1.3 | 0.4 | 2.1 |
| mx1–S parallel to SN (mm) | 2.9 | 2.6 | 0.7 | 3.9 | −0.4 | 2.8 |
| mx1–S perpend to SN (mm) | −0.6 | 1.8 | −0.1 | 1.3 | 0.3 | 2.1 |
| S–ANS parallel to SN (mm) | 2.2 | 2.6 | 0.2 | 3.4 | 0.4 | 2.6 |
| S–ANS perpend to SN (mm) | −0.8 | 2.4 | 0.6 | 3.2 | 0.3 | 2.6 |
| Mx–Md midline (°) | −1.4 | 6.7 | −0.4 | 2.1 | 0.8 | 1.9 |
| Right mx6 to Zy–Zy (mm) | −1.4 | 7.1 | 1.7 | 4.3 | −1.0 | 4.1 |
| Left mx6 to Zy–Zy (mm) | −1.5 | 8.6 | 0.7 | 4.7 | −0.3 | 3.8 |
| Occlusal cant (°) | 1.6 | 3.5 | −0.3 | 2.3 | −0.4 | 2.0 |
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