After the patient admitted to having concealed a serious bone disease from his treating physicians, so as not to jeopardize the execution of his desired orthodontic-surgical treatment, several medical treatment documents could be requested, from which a complex, long-term illness could be traced. The patient had already been diagnosed with OI as a 14-year-old. Since the sixth month of life, he had experienced about 20 fractures until the establishment of the pediatric diagnosis. The medical documents showed that he had already been classified as OI type I due to his medical history, proof of blue sclera, thoracic kyphosis, and DI. The diagnosis was made simultaneously with his 18-year-old brother, who also showed DI but was less severely affected as far as the number of bone fractures is concerned. However, after the diagnosis, a BP medication was not immediately started. At 21 years of age, the patient received more than 1 year of intravenous (IV) BP therapy with Aredia  (pamidronate, 30 mg) every 3 months for the prophylaxis of further fractures. Thereafter, the medication was changed to weekly Alendron  (alendronate, 70 mg) for 1 year. From the age of 24 to 29 years, the patient received IV Bonviva  (ibandronate, 150 mg, once a month). Indeed, the patient discontinued his current BP medication only for a short period of time after the completion of pre-surgical orthodontics. That means, this measure ("drug holiday") was effective only during the short period of consecutive orthognathic surgical procedures. After completion of surgery, the patient restarted his antiresorptive medication after consultation with the treating orthopedist. Since the age of 29 years, the patient has been treated with IV Prolia  (denosumab, 60 mg) every 6 months. 
The extractions of four premolars and consecutive wound healing proceeded inconspicuously according to the stage. 
The very late knowledge about the patient's bone disease and his current medication led to the decision to control the operative procedure and, therefore, to proceed in individual steps. In our opinion, there was an increased risk of bleeding during and after the procedure. In addition, given the long-term use of BP medication, the capacity for bone healing was not reliable. For this reason, a two-stage procedure was performed in the osteotomies of the jaws. After coordination with his orthopedic doctor, he was told to interrupt the medication.
Surgical therapy took place about 1 year after the beginning of orthodontic therapy (patient age: 26 years). For the surgical correction of jaw positions, an osteotomy was performed at the Le Fort I level with a saw and chisel. After a downfracture of the detached maxilla was performed, the maxilla was mobilized and posteriorly impacted, and the occlusal splint was incorporated. Osteosynthesis of the segment was done with four miniplates. The displacement of the maxilla caused it to rotate posteriorly, which improved the overbite. By correcting the tilted occlusal plane, a unilateral open bite resulted on the left side. For postoperative stabilization, a composite buildup was installed on the first and second molar of the lower left side and was left in place until the second surgical step. The anterior crossbite remained and was corrected by the following mandibular procedure. 
Vertical oblique osteotomy of the mandibular ramus combined with advancing genioplasty was performed 3 1/2 months after the maxillary procedure. This procedure resulted in setback of the mandible and shortening of the ramus on the left side. The right side only received rotation of the ramus with minimal setback. The following advancement of the chin was symmetrical, because the correction for panfacial asymmetry was already performed by jaw surgery. After the mandibular osteotomy, the stabilization resulted from MMF via the orthodontic appliances and integrated splint. The second splint had three perforations, each 1 cm2 in size, for easier breathing and allowing liquid nutrition. This second procedure also proceeded without major bleeding. In this case, the intraoperative procedure gave the impression that, without the knowledge of the underlying disease, the operative course of the procedure would not have differed from that of a patient not suffering from OI.
The surgical treatment documentation is shown in Figure 1 (Fig. 1), Figure 3 (Fig. 3), Figure 4 (Fig. 4), Figure 5 (Fig. 5), and Table 2 (Tab. 2).
Tissue samples of the ablated maxilla in the osteotomy line showed normal bone formation in the histological examination.
The last follow-up of the patient took place 3 years after the second surgical procedure. At this time, the patient had a stable class I occlusion, no signs of osteonecrosis, and radiologically unremarkable healed osteotomies of the jaw. The patient reported that he had suffered further fractures of the extremities after completion of orthognathic surgery and orthodontic procedures while continuing to receive denosumab medication. The skeletal function of the jaw had remained stable and uncomplicated since the orthodontic-surgical measures.
The literature review (Table 4 (Tab. 4)) included 27 reports of jaw osteotomies in patients with OI, including the present case (mean age: 22.59 years). Thirteen women and 12 men were treated (no information: two patients). The age of the women at the time of treatment was on average 23.38 years (range: 17.5 to 36 years) and that of men was on average 22.5 years (range: 12 to 40 years). 
The diagnosis of OI was certain in all cases (Table 1 (Tab. 1)). Typing of OI was missing for seven patients. In another case, the typing could not unambiguously distinguish between two classes. OI type I was the predominant diagnosis (14 patients), followed by a few cases that had either OI type III (three patients) or type IV (two patients). None of the reports on orthognathic surgery in OI patients refer to an OI severity grading system when describing the individual phenotype of the respective patient(s). However, orofacial or maxillofacial findings are not an assessment factor for a recently proposed severity classification.
A Le Fort I osteotomy was chosen as access to the skull base solely in order to treat basilar impression in a report detailing treatment of four patients. The report mentioned some maxillary advancement combined with spine surgery in one of these cases. Transposition of the divided jaws was carried out in all other cases or at least intended.
In 13 cases, only one jaw was osteotomized (women: 4, men: 9). Both jaws were osteotomized in 14 cases, of which two were temporally separate procedures for the same respective jaw. 
Osteotomies at Le Fort I level were made in 21 patients (women: 11, men 8, unspecified: 2). Lower jaw osteotomies (including genioplasty) were performed in 20 patients (women: 8, men: 10, unspecified: 2). Maxillary osteotomies were performed in all to achieve sagittal advancement of the maxilla.
In the lower jaw, the osteotomy aimed to relocate the corpus. Sagittal osteotomy of the mandibular ramus was the most frequently used technique (10 cases), followed by vertical ramus osteotomy (5 cases) and osteotomy within the mandibular corpus (3 cases). From the reports, it can be derived that the osteotomy of the lower jaw was used for setback of the corpus.
The osteosynthesis material corresponds to the developments of the procedures over the long period in which the recorded reports have been carried out. Wire osteosynthesis, which was previously used, has been replaced almost everywhere in later operations by miniplate osteosynthesis. However, a recent report shows that occasionally wire osteosynthesis is still used, combined with screw osteosynthesis. While some reports highlight the fragility and narrowness of bones, none of the reports on OI patients subjected to orthognathic procedures appear to have another fracture outside the selected osteotomy line that would have required surgical care.
BP medications are mentioned in three reports and are listed in detail for our own case. All other reports mention no such medication. For OI patients whose osteotomies were performed before the year 2000, it is assumed that BP medication is unlikely. In one case, BP medication was only mentioned and not specified. In another case, monotherapy with alendronate was performed; and in our own case, several medications of this type and another drug with similar activity were used before and after treatment. A short phase of interruption of medication for the operative treatment phase was known for two of the three cases. The fourth report was about successful orthognathic surgery on an OI patient. In this case, only a small amount of treatment information was found in the brief communication.
OI diagnosis had an impact on planning of the surgical strategy for a variety of reasons. The timing of the diagnosis had also been an important factor in therapy decisions. In one case, referring to the increased risk of complications during osteotomy, the surgical concept was adapted whereby the incomplete dentition allowed for prosthetic compensation of the unbalanced jaw relation. In another case, distraction of the segment was performed in the upper jaw after osteotomy instead of immediate transposition for the same reasons, as to avoid bleeding complications. In a third case, the bimaxillary operation was divided into two separate procedures, one jaw osteotomized each to minimize blood loss during and after surgery. In this case, for religious reasons, the patient had already refused transfusion of blood prior to surgical treatment. Despite these precautions with a long interval between interventions (7 months), perioperative hemorrhage occurred at the second procedure, necessitating omission of bone grafting. In our own case, the diagnosis of OI combined with the knowledge of pharmacotherapy led to the decision to osteotomize each jaw individually in one operation and to wait for a longer period of time between the procedures. These two patients are the only bimaxillary osteotomies in this review that were planned as two-time interventions. Another report indicates that previously unknown OI was noticed in two cases by the surgeon during osteotomy of the jaw due to significant brittleness of the bones. This finding has led to the adaptation of orthognathic intervention planning. In both cases, the osteotomy of the second jaw was omitted. Intraoperative suspicion of OI or very late knowledge of the disease is therefore available for at least three out of 27 patients.
Surgical complications, such as severe bleeding from the surgical situs, have been reported only for patients in whom no administration of BP medication was known or suspected. These reports described incidents more than 20 years ago. The brittleness of the bones and the difficult osteotomy are emphasized in individual reports.