The prominent mandibular angle: preoperative management, operative technique, and results in 42 patients

A prominent mandibular angle is considered to be unattractive in the Orient because it gives the face a square and muscular appearance. While described infrequently in the United States, this entity is commonly encountered in the Orient owing to different facial characteristics and different aesthetic sensibilities. We present a retrospective study of 42 female patients who presented requesting the reduction of a prominent mandibular angle for cosmetic reasons. We describe our approach, which utilizes formal planimetry, cephalometric tracings, and Panorex mandibular radiographs. We utilize the intraoral approach and use an oscillating saw to resect the predetermined segment of bone. In 18 of the 42 patients, we resected muscle as well. We also describe using the preauricular incision in a patient undergoing a concomitant rhytidectomy. Our cosmetic results have been generally satisfactory, with only one inaccurate osteotomy. We had three infections which resolved without sequelae.     

Treatment of craniomaxillofacial fibrous dysplasia: how early and how extensive?

Twenty-eight craniomaxillofacial fibrous dysplasia patients were treated as early as the symptoms occurred. The principles of surgical treatment were based on the zones of involvement: total excision of dysplastic bone of fronto-orbital, zygoma, and upper maxillary origin (zone 1) and bone reconstruction primarily; conservative excision on hair-bearing skull (zone 2), central cranial base (zone 3), and tooth-bearing bones (zone 4); and optic canal decompression on patients with orbital dysplasia and decreasing visual acuity. Patients were followed for 1 to 11 years (average 5.3 years). No recurrence or invasion of the fibrous dysplasia into the grafted bone was seen. One patient had orthognathic maxillary osteotomy on the reconstructed maxilla 6 years after initial reconstruction. Five of 19 patients with alveolar dysplasia had a recurrence and were reshaped. One patient had mandibular sagittal osteotomies to set back the prognathic, fibrous dysplasic mandible after three attempts at conservative shaving. Another patient with mandibular fibrous dysplasia had recurrence with pain and a hemimandibulectomy with successful immediate free vascularized iliac bone graft reconstruction.     

A simple method for establishing the position of the condylar segment in sagittal split osteotomy of the mandible

When a rigid fixation of the mandibular sagittal split osteotomy is performed, the exact position of the condyle has to be maintained. We report a simple method for determining the preoperative position of the proximal segment. The method is fast and does not require additional technical equipment. Preliminary results indicate that a decrease in postoperative temporomandibular joint problems can be achieved by using this method. A follow-up will show whether the method also can decrease the incidence of skeletal relapse.     

Midface position after LeFort III advancement

Nineteen of 30 patients who had midface advancement procedures between 1972 and 1980 had sufficient cephalometric data to be included in this retrospective study. The position of the midface in relation to the cranium and mandible was evaluated immediately postoperatively and for a period of 2 to 11 years (mean 5.8 years). At 1 year, midface position after LeFort III advancement was stable in 12 of 19 patients. Of these 12 patients, 8 showed some evidence of downward and/or forward movement of the midface. The remaining 7 patients showed a minor degree of midface relapse in the first year of follow-up. In 15 of 19 patients, at 2 years or more postoperatively, the final position of the midface was either at, anterior to, or inferior to its immediate postoperative location. Correction of exorbitism remained stable in all but one patient, who required a second advancement of the orbital segment. Three patients required subsequent LeFort I osteotomy to correct class III occlusion. Prognathism was determined to be secondary to mandibular growth, not midface relapse.     

Lengthening of the reconstructed mandible using extraoral distraction devices: report of five cases

Fibular and scapular osteocutaneous free-tissue transfer represents the workhorse procedure in the reconstruction of large oromandibular defects. However, transplanted bone segments for mandibular reconstruction may be too short for a correct interarch alignment, which is a prerequisite for further functional rehabilitation. Extraoral distraction osteogenesis was performed in the neomandible of five patients after tumor resection following neoadjuvant radiotherapy-chemotherapy. The neomandible was distracted bilaterally in two patients and unilaterally in three patients. Gradual distraction was applied at a rate of 0.5 mm twice a day after osteotomy in the region of vascularized fibular and scapular reconstruction. An average sagittal bone gain of 11 mm was achieved following active distraction. In three patients, the distraction procedure rendered good results with full compensation of the deficit; in one patient, the sagittal bone gain did not compensate for a lateral deviation of the mandible; and in another patient, the fixation pins loosened and had to be reaffixed. Osteodistraction is a treatment option in patients in whom vascularized bone grafts have been used for mandibular reconstruction, but due to contractures or lack of hard and soft tissues, no satisfactory interarch alignment could be achieved. Distraction procedures in irradiated and reconstructed neomandibles bear a higher risk of failure and complications than those in nonirradiated tissues. A correct and stable intermaxillary relation always has to be attempted in the first surgical approach, as osteodistraction cannot be suggested as a routine procedure in this special group of patients.     

Multiple-segment osteotomy in maxillofacial surgery

Multiple-segment osteotomy is defined as an osteotomy that divides the tooth-bearing arch of the maxilla or mandible into three or more segments. Combining large-segment orthognathic surgery and unitooth or small-segment surgery is an effective approach for dealing with a wide range of dentofacial deformities with occlusal problems. The indications for a multiple-segment osteotomy included dentofacial deformities and malocclusions requiring stable correction within a short overall treatment period. From 1991 to 1997, a total of 85 patients had multiple-segment osteotomy orthognathic procedures performed at Chang Gung Memorial Hospital. The indications for surgery were maxillary protrusion/deformity (31 patients), mandibular prognathism (51 patients), and noncleft maxillary retrusion (three patients). The types of osteotomies performed were Le Fort I, anterior segmental osteotomies of the maxilla or the mandible, palatal split, posterior segment, and unitooth or double-tooth segments. Follow-up ranged from 6 months to 7 years; stability was seen in movements, with only three complications (one partial gingival loss and two inferior mental paresthesias). No osteotomized segments were lost. The average overall treatment time was approximately 15 months, including 3 to 6 months of preoperative and 9 to 12 months of postoperative orthodontic treatment. This is at least 6 months shorter than traditional orthognathic surgery. Experience with 85 consecutive patients has shown that the results are good and the procedure is safe, with minimal complications.     

Tensioning technique and fixator stability of a circular external fixator with threaded fine wires

Hybrid external fixators have become more popular over recent years, and although biomechanical tests show varying results from paper to paper, a consistent finding is shear motion occurring at the fracture/osteotomy site during loading. This can be reduced to some extent by frame configuration, and with the use of olive stop wires, but both of these have limitations. We have investigated the use of threaded fine wires in a circular hybrid fixator. A reliable tensioning method is described which minimises movement at the wire-bone interface during tensioning, and threaded wires are seen to offer a significant improvement in fracture site shear stiffness when compared to smooth fine wires.     

Evaluation of bone height in osseous free flap mandible reconstruction: an indirect measure of bone mass

Osseous free flaps have become the preferred method of mandibular reconstruction after oncologic surgical ablation. To elucidate the long-term effects of free flap mandibular reconstruction on bone mass, maintenance or reduction in bone height over time was used as an indirect measure of preservation or loss in bone mass. Factors potentially influencing bone mass preservation were evaluated; these included site of reconstruction (central, body, ramus), patient age, length of follow-up, adjuvant radiotherapy, and the delayed placement of osseointegrated dental implants. A retrospective analysis of patients undergoing osseous free flap mandible reconstruction for oncologic surgical defects between 1987 and 1995 was performed. Postoperative Panorex examinations were used to evaluate bone height and bony union after osteotomy. Fixation hardware was used as a reference to eliminate magnification as a possible source of error in measurement. There were 48 patients who qualified for this study by having at least 24 months of follow-up. There were 27 male and 21 female patients, with a mean age of 45 years (range, 5 to 75 years). Mandibular defects were anterior (24) and lateral (24). Osseous donor sites included the fibula (35), radius (6), scapula (4), and ilium (3). There were between zero and four segmental osteotomies per patient (excluding the ends of the graft). Nineteen percent of all patients had delayed placement of osseointegrated dental implants. Initial Panorex examinations were taken between 1 and 9 months postoperatively (mean, 2 months). Follow-up Panorex examinations were taken 24 to 104 months postoperatively (mean, 47 months). The bony union rate after osteotomy was 97 percent. Bone height measurements were compared by site and type of reconstruction. The mean loss in fibula height by site of reconstruction was 2 percent in central segments, 7 percent in body segments, and 5 percent in ramus segments. The mean loss in bone height after radial free flap mandible reconstruction was 33 percent in central segments and 37 percent in body segments; ramus segments did not lose height. The central and body segments reconstructed with scapular free flaps did not lose height, but one ramus segment lost 20 percent of height. There was no loss in bone height in mandibular body reconstruction with the ilium free flap. Fibula free flaps did not significantly lose bone height when evaluated with respect to age, follow-up, radiation therapy, or dental implant placement. The retention in bone height demonstrated in this study suggests that bone mass is preserved after osseous free flap mandible reconstruction. The greatest amount of bone loss was seen after multiply osteotomized radial free flaps were used for central mandibular reconstruction. The ability of the fibula free flap to maintain mass over time, coupled with its known advantages, further supports its use as the "work horse" donor site for mandible reconstruction.     

Mandibular osteotomy-induced hypoxia enhances osteoclast activation and acid secretion by increasing glycolysis

The rapid bone remodeling after osteotomy has been reported for a long time. However, the underlying mechanism promoting the active bone reconstruction was still to be elucidated. Since not only the bone, blood vessels, and supportive tissues, but also the local microenvironment were destroyed, if the changes on the cell metabolism was contributed to the accelerated bone remodeling came into sight. In present study, we found that the mandibular osteotomy in rabbit activated osteoclasts, as well as the expression of hypoxia-inducible factor 1α (HIF-1α) in alveolar bone. Hypoxia or HIF-1α could enhanced osteoclastogenesis, bone absorption, and lactic acid concentration in receptor activator of nuclear factor κΒ ligand-induced RAW264.7 cells. Coincided with the upregulated HIF-1α expression, HIF-driven glycolytic enzymes, such as lactate dehydrogenase A (LDHA), glucokinase (GCK), pyruvate kinase M2 (PKM2), and phosphofructokinase1 (PFK1), were found massively increased in both hypoxic RAW264.7 cells and the alveolar HIF-1α-positive osteoclasts after mandibular osteotomy. Knockdown of HIF-1α suppressed not only the hypoxia-mediated glycolysis, but also the hypoxia-induced acid secretion and bone resorption in RAW264.7 cells. Application of inhibitor on glycolysis gave rise to the similar results as HIF-1α knockdown. Our findings suggested that hypoxia-driven glycolysis in osteoclasts was an adaptive mechanism to permit alveolar bone remodeling after mandibular osteotomy.     

The Le Fort III advancement osteotomy in the child under 7 years of age

This is a longitudinal study of 12 patients with craniofacial synostosis syndromes (Crouzon's, Apert's, Pfeiffer's) who underwent Le Fort III advancement under the age of 7 years (average age 5.1 years, range 4.0 to 6.7 years). The average follow-up was 5.0 years and included clinical, dental, and cephalometric examinations according to a prescribed protocol. The study demonstrated that the procedure could be safely performed in the younger child with an acceptable level of morbidity. There was a remarkable degree of postoperative stability of the maxillary segment. However, although vertical (inferior) growth or movement of the midfacial segment was demonstrated, there was minimal, if any, anterior or horizontal growth. Any occlusal disharmony developing during the period of follow-up could be attributed to anticipated mandibular development and could be corrected by orthognathic surgery. The roles of surgical overcorrection and anterior-pull headgear therapy after release of intermaxillary fixation are also discussed. The Le Fort III osteotomy is justifiably indicated during early childhood for psychological and physiologic reasons.     

Removal of mandibular tooth follicles before distraction osteogenesis

Distraction osteogenesis is an innovative technique that has transformed the treatment of craniofacial malformations in young children. Bone generation obviates the need for graft material, which is in short supply in young patients, thus making possible surgical procedures on the craniofacial skeleton in young children. Sufficient mandibular volume is required for the osteotomy and placement of the device screws and/or pins. To have adequate bone stock and to facilitate distraction, the authors preoperatively examined all patients radiographically and selected those with tooth follicles that precluded successful osteotomy and pin placement for planned mandibular distraction. This report is of the first 13 children, aged 9 months to 6 years, who underwent predistraction enucleation. The osteotomy and device placement were performed successfully at least 4 months after enucleation. The described procedure has minimal morbidity and has resulted in successful subsequent distraction. The advantages, disadvantages, and cost-benefit issues are discussed.     

The Biomechanical Effects of Sagittal Split Ramus Osteotomy on Temporomandibular Joint

Abstract

The aim of this study was to evaluate the stress distributions and deformations of the temporomandibular joint (TMJ) during different periods before and after sagittal split ramus osteotomy (SSRO). A three-dimensional finite element model of the mandible and TMJ was established, based on the preoperative CT of a patient with mandibular prognathism. Numerical SSRO was performed and the models of three postoperative periods were established. Contact elements were used to simulate the interaction between the articular discs and the articular cartilages. Nonlinear cable elements were used to simulate the disc attachments and the ligaments. Muscle forces and boundary conditions corresponding to the central occlusion were applied on all the models. The results showed that the stress distributions of the patient’s TMJs were not the same as those of asymptomatic subjects. The stress distributions and deformations of the disc, condylar and temporal cartilage were changed at different periods after SSRO. The biomechanical parameters of TMJ were improved after SSRO. And the postoperative results showed that appropriate functional training could help to avoid TMJ diseases. Therefore SSRO could improve the stress distributions of the TMJ and relieve the symptoms of temporomandibular disorder (TMD).     

Use of virtual surgery and stereolithography-guided osteotomy for mandibular reconstruction with the free fibula

Fibular osteotomy remains a challenging aspect of mandibular microsurgical reconstruction, dependent largely on surgeon experience, intraoperative judgment, and technical speed. Virtual surgical planning and stereolithographic modeling is a relatively new technique that can allow for reduction in the learning curve associated with neomandible contouring, enhanced levels of accuracy, and acceleration of a time-consuming intraoperative step. The authors present a video (narrated and edited from planning sessions and intraoperative use of technique to illustrate the technology) and describe their favorable results. Five patients underwent composite resection of the mandible and free fibula osteocutaneous reconstruction over a 6-month period (December of 2009 to June of 2010) at a single institution using a virtual planning session and stereolithographic modeling. Outcomes assessed included technical accuracy, aesthetic contour, and functional outcomes. All patients achieved negative margins with cutting guide-directed resection. Use of this technique eliminated the need for intraoperative measurement and yielded fibular segments with excellent apposition and faithful duplication of the preoperative plan. Minimal adjustments were needed for inset. Flap survival was 100 percent. All patients have maintained preoperative occlusion and a symmetric mandibular contour on Panorex study, three-dimensional computed tomography, and clinical examination. Accuracy of the reconstructed contour was confirmed using computed tomographic image overlay. This virtual surgical planning technique combined with stereolithographic model-guided osteotomy is the mainstay of the authors' approach to fibular osteotomy when dealing with patients requiring mandibular reconstruction. The authors feel this technology facilitates realization of technical accuracy, aesthetic contour, and functional outcomes and may be particularly useful if free fibular mandibular reconstruction is performed less frequently. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.     

Early embryonic development of the head region of Gryllus assimilis Fabricius, 1775 (Orthoptera,Insecta)

We report our investigations on the embryonic development of Gryllus assimilis, with particular attention to the head. Significant findings revealed with scanning electron microscopy (SEM) images include: (1) the pre-antennal lobes represent the anterior-most segment that does not bear any appendages; (2) each of the lobes consists of central and marginal regions; (3) the central region thereof develops into the protocerebrum and the optic lobes, whereas the marginal region thereof becomes the anterior portion of the head capsule; (4) the initial position of the antennal segment is posterior to the mouth region; (5) appendage anlagen are transitorily present in the intercalary segment, and they later vanish together with the segment itself; (6) a bulged sternum appears to develop from the ventral surface of the mandibular, maxillary and labial segments. Embryonic features are then compared across the Insecta and further extended to the embryos of a spider (Araneae, Chelicerata). Striking similarities shared by the anterior-most region of the insect and spider embryos lead the authors to conclude that such comparison should be further undertaken to cover the entire Euarthropoda. This will help us to understand the embryology and evolution of the arthropod head.     

Self-stabilizing osteotomy for frontal bar advancement

This technique is simple, quick to perform, and produces a rigid block against posterior relapse of the advanced frontal bar in surgery for bicoronal synostosis. This stability is achieved without the need to place a bone graft across the craniectomy site in small infants with rapidly expanding brains. Finer and fewer interosseous wires are required, decreasing the chance of transcutaneous palpation, and this principle can be incorporated into most osteotomy patterns around the orbits.     

Mandibular reconstruction in the radiated patient: the role of osteocutaneous free tissue transfers

This paper discusses our experience with the second metatarsal and iliac crest osteocutaneous transfers for mandibular reconstruction. The prime indication for this type of reconstruction was for anterior mandibular defects when the patient had been previously resected. Midbody to midbody defects were reconstructed with the metatarsal and larger defects with the iliac crest. In most cases, an osteotomy was done to create a mental angle. The evaluation of speech, oral continence, and swallowing revealed good results in all patients unless lip or tongue resection compromised function. Facial contour was excellent in metatarsal reconstructions. The iliac crest cutaneous flap provided a generous supply of skin for both intraoral reconstruction and external skin coverage but tended to be bulky, particularly when used in the submental area. Thirty three of 36 flaps survived completely. Flap losses were due to anastomosis thrombosis (1), pedicle compression (1), and pedicle destruction during exploration for suspected carotid blowout (1). Ninety three percent of bone junctions developed a solid bony union despite the mandible having had a full therapeutic dose of preoperative radiation. Despite wound infections in 8 patients, and intraoral dehiscence with bone exposure in 12 patients, all but one of these transfers went on to good bony union without infection in the bone graft.