Abstract
The purpose of this study was to evaluate the stability of rigid internal fixation in orthognathic surgery with either bioabsorbable or titanium osteosynthesis. Orthognathic surgery was performed on 101 patients. Bilateral sagittal ramus osteotomy was performed on 55 patients using bioabsorbable osteosynthesis in 26 and titanium osteosynthesis in 29 patients. Le Fort I osteotomy was performed on 28 patients with bioabsorbable and titanium osteosynthesis in 17 and 11 patients, respectively. Bimaxillary osteotomies were performed on 18 patients (8 were fixated with bioabsorbable and 10 with titanium osteosynthesis). Poly-70 l /30 dl -lactide copolymer (PLDLA) consisting of 70% l -lactide and 30% dl -lactide was used as the bioabsorbable osteosynthesis material. These plates and screws were compared with corresponding titanium materials. Statistically a clear relapse tendency was seen in skeletal measurements in all patient groups but without clinical importance. Radiological follow-up time was at least 18.3 months and clinical follow-up time at least 6.3 years. The materials used did not cause any adverse reaction except in three cases, one in the bioabsorbable group and two in the titanium group where fistula in connection with the osteosynthesis material was noted resulting in removal of the materials.
The use of bioabsorbable plates and screws as internal fixation devices has gained popularity in orthognathic surgery . Some disadvantages, such as intracranial migration and growth inhibition in paediatric patients and palpability in all patient categories, have been reported when metallic osteosynthesis materials have been used . Interference with imaging techniques and radiation therapy, which has been reported with metallic fixation devices, also provides a rationale to using a bioabsorbable polymer fixation system.
The use of titanium osteosynthesis material for the fixation of mandibular fractures has been associated with an incidence of 12% or higher for plate removal. After maxillary osteotomies in orthognathic surgery, 11% of patients needed plate removal for reasons such as pain, palpability, sinusitis, temperature sensitivity, infection or other requests by patients . Other studies have reported lower removal rates . The plates and screws are often removed under general anaesthesia. Such extra surgical interventions should be avoided, from a socio-economic as well as medical point of view.
Internal rigid fixation of maxillary Le Fort I osteotomies is stable when maxillary advancement can be performed with solid bony contact . Some differences in vertical stability between bioabsorbable and titanium osteosynthesis have been reported during the first 6 postoperative weeks in patients with Le Fort I maxillary impaction. There were no differences in morbidity between these groups . A study of fixation of Le Fort I advancement found that biodegradable poly-p-dioxanone and titanium miniplates were equally stable in the anteriorposterior plane, but a tendency to relapse in the vertical dimension was noticed in both groups . Rigid fixation has provided good skeletal stability in mandibular surgery according to several authors . In mandibular setback surgery, bioabsorbable plates have provided stable fixation in the horizontal dimension, but have allowed an increase of vertical relapse . Bioabsorbable devices have been used for stabilization of mandibular advancement with comparable outcome to other forms of rigid internal fixation . In bimaxillary orthognathic surgery, bioabsorbable self-reinforced poly- l / dl -lactide (SR-PLDLA) plates and screws have been shown to give skeletal stability comparable to titanium plates and screws .
The objective of this study was to compare the stability of rigid internal fixation of maxillary and mandibular osteotomies when a bioabsorbable osteosynthesis material (Bio-SorbFX, SR-PLDLA 70/30, Conmed Linvatec, Tampere, Finland) or titanium miniplates (Leibinger, Freiburg, Germany) were used. The morbidity associated with the use of these two fixation devices was also evaluated.
Materials and methods
This study was approved by the ethical committee of the Central Hospital of Central Finland Health Care District, number Dnro K-S shp 29/2001. Hundred and one consecutive voluntary patients with maxillary or mandibular growth disturbances, scheduled for (non-segmentalized) maxillary Le Fort I osteotomy, mandibular bilateral sagittal split osteotomy (BSSO) or both, were recruited for the study over 2 years and 5 months. Hundred and ninety-two osteotomies were performed by the same senior surgeon with standard techniques for LeFort I and BSSO osteotomies. Bilateral sagittal ramus osteotomy was carried out on 55 patients using bioabsorbable osteosynthesis in 26 and titanium osteosynthesis in 29 patients. Le Fort I osteotomy was performed on 28 patients with bioabsorbable and titanium osteosynthesis in 17 and 11 patients, respectively. Bimaxillary osteotomies were performed on 18 patients of which 8 were fixated with bioabsorbable and 10 with titanium osteosynthesis. Patient details are shown in Table 1 .
| Le Fort I | BSSO | Bimaxillary | All | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Male | Female | Male | Female | Male | Female | Male | Female | |||||||||
| Mean age | n | Mean age | n | Mean age | n | Mean age | n | Mean age | n | Mean age | n | Mean age | n | Mean age | n | |
| Titanium | 42.3 | 3 | 30.1 | 8 | 34.4 | 8 | 38.0 | 21 | 36.0 | 3 | 32.0 | 7 | 36.4 | 14 | 35.1 | 36 |
| PLDLA | 24.1 | 8 | 34.8 | 9 | 30.0 | 7 | 35.8 | 19 | 23.0 | 3 | 38.8 | 5 | 26.2 | 18 | 34.5 | 33 |
| All | 33.5 | 11 | 32.6 | 17 | 32.3 | 15 | 37.0 | 40 | 29.5 | 6 | 30.7 | 12 | 30.7 | 32 | 34.8 | 69 |
| Mean age (years) | 31.2 | 35.7 | 30.28 | 33.5 | ||||||||||||
| All ( N ) | 28 | 55 | 18 | 101 | ||||||||||||
Inclusion criteria were planned maxillary advancement or/and impaction, mandibular advancement or both in healthy patients aged 16–60 years. Patients who were pregnant or were unable to return for long-term follow-up were excluded from the study as well as patients with insufficient quantity or quality of bone. To be included in the study, solid contacts were required between the bony segments during surgery. Patients fulfilling these criteria were accepted on the study after being given written and oral information and providing informed consent.
All patients were prospectively and consecutively randomized to two study groups: bioabsorbable or titanium fixation. The randomization to the bioabsorbable or titanium fixation groups occurred as the patients presented for operative treatment, so the numbers in each group are different. Radiological examinations were scheduled 1 day postoperatively, 6 months postoperatively and at a minimum of 12 months postoperatively ( Table 2 ). Clinical examinations were carried out on days 1 and 2 postoperatively, 1 and 2 weeks postoperatively and at all postoperative orthodontic visits. All patients were followed up clinically for at least 3 years after their last radiological examination.
| Material | Titanium | PLDLA | ||
|---|---|---|---|---|
| Operation | Mean (min–max) | Std | Mean (min–max) | Std |
| BSSO | 28.5 (5.9–64.7) | 17.8 | 21.1 (5.7–64) | 14.8 |
| Le Fort I | 19.2 (7.4–49.3) | 12.8 | 18.6 (6.1–50.2) | 12.9 |
| Bimaxillary | 18.3 (6.5–54.3) | 4.9 | 21.2 (5.1–52.2) | 15.2 |
| Total | 24.7 (5.9–64.7) | 15.6 | 20.2 (5.1–64) | 13.9 |
Fixation materials
In group A, the bioabsorbable material used was SR-PLDLA 70/30 copolymer (Biosorb FX, Conmed Linvatec, Tampere, Finland). There were no changes in the fabrication or composition of the resorbable material over the study period. The plates can be bent with pliers at room temperature without any warming. In the body, the material is hydrolyzed and further metabolized (via Krebs’ cycle) to carbon dioxide and water. The material is completely absorbed within 9–15 months. The initial mechanical strength of the polymer is comparable to titanium and the flexion strength after 6 weeks is 70% of the initial level. The BioSorb fixation system has been approved by the FDA in the USA and is CE marked in Europe. Maxillary osteotomies were fixated bilaterally with 0.8 mm strut plates paranasally (plate in two rows with 6–8 holes) and 2–3 hole plates in the zygomatic buttress area. The screws used were 2.4 mm in diameter and 6–8 mm in length. Mandibular osteotomies were fixated bilaterally with three positional screws (diameter 2.8 mm, length 14–16 mm).
In group B, the titanium miniplates and screws were provided by Leibinger (Freiburg, Germany). Maxillary osteotomies were fixated bilaterally with 1.0 mm plates paranasally (plate in two rows with 6–8 holes) and a 2–3 hole plate in the zygomatic buttress area. The screws used were 2 mm in diameter and 6–8 mm in length. Mandibular osteotomies were fixated bilaterally with three positional screws (diameter 2.0 mm, length 14–16 mm).
Surgery
Surgery was performed using modified surgical techniques described by Epker and Wolford for maxillary Le Fort I osteotomy and for mandibular surgery sagittal ramus osteotomy . Bony reductions were made in the lingual region of the mandible to avoid interference with the bony segments . Bony reductions were made in the maxilla bilaterally in the region of the descending palatine arteries and posterior nasal spine to maximize the mobilization of the maxilla. Stable contacts were achieved between the bony segments. A surgical splint with temporary intermaxillary fixation was used for positioning the jaws. Osteosynthesis was performed bilaterally using one strut plate paranasally (plate in two rows with 6–8 holes) and one straight plate at the zygomatic buttress with a total of 12–16 screws in the maxilla. Three bicortical positional screws were routinely used in the mandible except in 10 patients, in whom only two screws were used, on one or both sides, due to anatomical reasons ( Figs. 1–4 ). Antibiotics, analgesics and corticosteroids were given and continued according to the authors’ protocol. This consisted of preoperative doses of 10 mg dexamethasone (Oradexon, Oss, The Netherlands) and 2 million I.U. benzylpenicillin (Geepenil, Espoo, Finland). Dexamethasone was continued 24 h postoperatively with a doses of 5 mg every 8 h and benzylpenicillin 2 million I.U. every 12 h. Once the patient was able to take per os medication, the antibiotic was continued as v-penicillin (V-pen Mega, Espoo, Finland) 1 million I.U. every 8 h for 7 days. The postoperative analgesic used was naproxen sodium (Pronaxen, Espoo, Finland) 500 mg every 12 h and paracetamol 1.0 g (Panadol, Dungarvan, Ireland) every 8 h. Chlorhexidine 0.2% (Corsodyl, Herouville, France) mouthrinse was used every 12 h for 14 days. Patients whose maxilla was operated on received xylometazoline hydrochloride nasal spray (Otrivin, Espoo, Finland) for a maximum of 7 days for nasal stuffiness. Postoperative guiding elastics were used in all cases immediately after surgery.
Clinical and radiological examination
Wound healing was assessed during the postoperative period. All adverse reactions or complications were recorded.
The same cephalostat was used for cephalograms. Cephalometric analysis was performed by one experienced orthodontist. SN/ML, SN/NL and ML/NL angles were used for vertical measurements and SNA, SNB and ANB for sagittal ones. Overjet and overbite values were measured. Radiographs were taken 1 day postoperatively, 6 months postoperatively and at least 12 months postoperatively. In the first radiographs, the patients were still wearing their splints.
Statistical analysis
Statistical analysis was performed and checked by a biomathematician. Statistical analysis of the mean differences between the groups on cephalograms was performed by SPSS. The mean differences between the first postoperative day and with postoperative controls at 6 and a minimum of 12 months following surgery were tested with general linear models repeated measurements.
Results
The postoperative healing period was uneventful in most patients. Osteosynthesis material was removed in 3 patients because of fistula and some discomfort.
Some osteolysis could be seen in the mandible of the bioabsorbable group on radiographic examination after 12 months, but these changes seemed to resolve ( Fig. 5 ). Bioabsorbable material was removed from one maxilla and titanium osteosynthesis material from two mandibles. The mean radiological follow-up time was 18.3 months with a range of 5.1–64.7 months. The mean clinical follow-up was 6.3 years with a range of 4.8–7.5 years ( Tables 2 and 3 ).
