The surgical procedure

The surgery was performed under general anaesthesia in both groups. Preoperatively, 2 g of cefazolin and 0.5 mg/kg dexamethasone were given intravenously. Another dosage of 10 mg dexamethasone was given at 8 and 16 h postoperatively. The patients in the DO group received feneticilline 500 mg three times a day for 5 days.

Bilateral sagittal split osteotomy (BSSO)

Local infiltration was performed with articaine (Ultracaine DS forte). After incision and reflection of the full-thickness mucoperiosteal flaps, a standard BSSO was performed according to the technique of Trauner and Obwegeser and as modified by Dal Pont and Hunsuck. The mandibular foramen was identified on the medial side of the ramus. The horizontal osteotomy just above the lingula was extended to the buccal side at the external oblique line and passed through the buccal cortex in the region of the first or second molar. The osteotomy was finished at the lower mandibular border. The osteotomy of the mandible was then completed with a Smith ramus separator and sagittal separator left/right (Biomet Microfixation, Jacksonville, FL, USA) without the use of chisels. After advancement, the mandible was positioned according to the planned occlusion using a thin interocclusal acrylic splint (wafer) and fixed with stainless steel intermaxillary wires.

The osteotomy was then stabilized with titanium miniplates (2.0 plates; Synthes GmbH, Solothurn, Switzerland). The miniplates were fixed with at least two monocortical 5- or 7-mm screws on each side of the osteotomy. The intermaxillary fixation was then released and the occlusion was checked. After 1 week, guiding elastic bands (if required) were placed for 4–6 weeks.

Distraction osteogenesis (DO)

The mucosa was infiltrated with articaine (Ultracaine DS forte). The mandibular body and angle were exposed and a buccal vertical bone incision including the mandibular lower border was made just behind the second molar. If present, the third molar was removed at this stage. The corticotomy was extended distal to the second molar, to the lingual side of the mandible, with a fissure bur. Before completion of the corticotomy, a unidirectional distractor device (Zurich Distractor; KLS Martin GmbH & Co, Tuttlingen, Germany) was adapted, installed, and fixed in place with at least two monocortical screws on each side of the distraction device. The distractor was placed parallel to the occlusal plane. After removal of the distractor, the corticotomy was completed on the lingual side of the mandible. Finally, the distractor device was reattached in the marked position and fixed with six monocortical screws. Before closure of the wounds, the distractor was activated to confirm proper functioning, and finally the distractor was returned to its original position. After a latency period of 5–7 days, the distractor devices were activated by 0.5 mm two times per day. Distraction was continued until a class I occlusion was achieved. Intermaxillary guiding elastic bands were used during this period to prevent opening of the bite. The bone consolidation period lasted 8–10 weeks, after which the devices were removed under general anaesthesia.

Perioperative protocol and questionnaires

Postoperatively, patients in the BSSO group were asked to refrain from chewing for 6 weeks and those in the DO group for 8–10 weeks.

During surgery the patients were given opioids. Patients were asked to record the pain they experienced on each postoperative day, starting the day after surgery, using a visual analogue scale (VAS) (0–100 mm). At the end of each postoperative day the patients recorded three VAS scores for pain: they were asked to register the lowest perceived pain score of the day, the highest perceived pain score of the day, and the pain score they were experiencing at the time they completed the VAS evaluation in the evening. The mean of these three VAS scores was calculated to give a final VAS score for each postoperative day.

Patients were also asked to register the daily number of analgesics administered. A combination of ibuprofen 600 mg three times a day and paracetamol 500 mg eight times a day was usually prescribed. For each painkiller, the score was related to the maximum dose per day for each drug. A score of 1 represented the maximum dose of one analgesic per day, and a score of 0.66 meant that the patient had used two-thirds of the maximum dose of that analgesic per day. Thus, if the patient used ibuprofen 600 mg three times a day, this was scored as 1; if the patient took the maximum prescribed number of ibuprofen and paracetamol, this was scored as 2. Some patients combined these two analgesics with a third – tramadol 50 mg three times per day. When these three analgesics were taken to the maximum, the score was 3.

Finally, the actual operating time, blood loss, total costs, and occurrence of postoperative infection related to the mandibular surgery were also recorded. The duration of hospital admission was registered for all patients.

Statistical analysis

The data were analyzed using SPSS version 18.0 software (SPSS Inc., Chicago, IL, USA). Continuous data were analyzed with a Student’s t -test and dichotomous data with a Pearson χ ² test.