Analysis of skeletal movements in mandibular distraction osteogenesis

Helical distraction is superior to linear and circular distraction in mandibular distraction osteogenesis: an in silico study

Helical mandibular distraction is theoretically better than linear or circular distraction. However, it is not known whether this more complex treatment will result in unquestionably better outcomes. Therefore, the best attainable outcomes of mandibular distraction osteogenesis were evaluated in silico, given the constraints of linear, circular, and helical motion. This cross-sectional kinematic study included 30 patients with mandibular hypoplasia who had been treated with distraction, or to whom this treatment had been recommended. Demographic information and the computed tomography (CT) scans showing the baseline deformity were collected. The CT scans of each patient were segmented and three-dimensional models of the face created. Then, the ideal distraction outcomes were simulated. Next, the most favorable helical, circular, and linear distraction movements were calculated. Finally, errors were measured: misalignment of key mandibular landmarks, misalignment of the occlusion, and changes in intercondylar distance. Helical distraction produced trivial errors. In contrast, circular and linear distractions resulted in errors that were statistically and clinically significant. Helical distraction also preserved the planned intercondylar distance, while circular and linear distractions led to unwanted changes in the intercondylar distance. It is now evident that helical distraction offers a new strategy to improve the outcomes of mandibular distraction osteogenesis.

Helical distraction is superior to linear distraction in maxillary distraction osteogenesis: an in silico study

This in silico kinematic study was performed to evaluate the best attainable outcomes of maxillary distraction osteogenesis given the constraints of linear and helical motion. The study sample included the retrospective records of 30 patients with maxillary retrusion who had been treated with distraction or had been recommended this treatment. The primary outcomes were the errors of linear and helical distraction. The study measured two types of error: misalignment of key upper jaw landmarks and misalignment of the occlusion. Concerning the misalignment of key landmarks, the median misalignments resulting from helical distraction were minimal; the interquartile ranges were also minimal. The median misalignments and interquartile ranges that resulted from linear distraction were significantly larger. Regarding the occlusal misalignments, helical distraction produced minor occlusal misalignments, while linear distraction produced significantly larger errors. The results of this study confirmed that helical motion is the ideal motion for LeFort I distraction.

Continuous distraction osteogenesis device with MAAC controller for mandibular reconstruction applications

Background

Distraction osteogenesis (DO) is a novel technique widely used in human body reconstruction. DO has got a significant role in maxillofacial reconstruction applications (MRA); through this method, bone defects and skeletal deformities in various cranio-maxillofacial areas could be reconstructed with superior results in comparison to conventional methods. Recent studies revealed in a DO solution, using an automatic continuous distractor could significantly improve the results while decreasing the existing issues. This study is aimed at designing and developing a novel automatic continuous distraction osteogenesis (ACDO) device to be used in the MRA.

Methods

The design is comprised of a lead screw translation mechanism and a stepper motor, placed outside of the mouth to generate the desired continuous linear force. This externally generated and controlled distraction force (DF) is transferred into the moving bone segment via a flexible miniature transition system. The system is also equipped with an extra-oral ACDO controller, to generate an accurate, reliable, and stable continuous DF.

Results

Simulation and experimental results have justified the controller outputs and the desired accuracy of the device. Experiments have been conducted on a sheep jaw bone and results have showed that the developed device could offer a continuous DF of 38 N with distraction accuracy of 7.6 nm on the bone segment, while reducing the distraction time span.

Conclusion

Continuous DF with high resolution positioning control, along with the smaller size of the distractor placed in the oral cavity will help in improving the result of the reconstruction operation and leading to a successful DO procedure in a shorter time period. The developed ACDO device has less than 1% positioning error while generating sufficient DF. These features make this device a suitable distractor for an enhanced DO treatment in MRA.

Cephalometric Improvement of Severe Microretrognathia With an Anterior Open Bite Using Curvilinear Mandibular Distraction Osteogenesis

Curvilinear mandibular distraction osteogenesis (MDO) provides for multidimensional augmentation and rotation in mandibles with complex, abnormal morphology. This study aims to demonstrate cephalometric changes after curvilinear MDO.A prospectively maintained craniofacial database was queried for patients undergoing curvilinear MDO from 2009 to 2015. Demographic and operative data were collected. Cephalometric measurements were obtained from preoperative and postdistraction imaging, including sella-nasion-B point angle (SNB), mandibular plane angle (MPA), occlusal plane angle (OPA), and gonial angle (GA). Measurements were compared using a paired t test.Nine patients exhibiting microretrognathia and an anterior open-bite deformity had a mean age of 8.4 ± 6.0 years and a mean follow-up of 23.2 ± 25.3 months. Mean distance distracted was 32.6 ± 7.2 mm, with augmentation in length and height, and rotatory closure of anterior open bites. Preoperative SNB versus postdistraction was 66.9 ± 4.2 versus 78 ± 9.1° (P = 0.0029). MPA, OPA, and GA all decreased (61.0 ± 10.7 vs. 45.7 ± 11.1°, P = 0.0066, 37.3 ± 8.9 vs. 25.7 ± 6.0°, P = 0.0025, 140.3 ± 16.1 vs. 127.3 ± 13.2°, P = 0.0019, MPA, OPA, and GA, respectively), trending toward normalization. Airway diameter increased by 7.1 ± 2.8 mm. Anterior bite improved by 7.2 ± 1.9 mm. Complications arose in 2 subjects including device malfunction and wound infection.Curvilinear MDO results in dramatic cephalometric improvement in patients with severe microretrognathia and anterior open-bite. The procedure is associated with a high rate of complications, and long-term stability of movement has yet to be documented.

Bilateral Continuous Automated Distraction Osteogenesis: Proof of Principle

The purpose of this study was to demonstrate that automated, continuous, curvilinear distraction osteogenesis (DO) in a minipig model is effective when performed bilaterally, at rates up to 3 mm/day, to achieve clinically relevant lengthening. A Yucatan minipig in the mixed dentition phase underwent bilaterally, at a continuous DO at a rate of 2 mm/day at the center of rotation; 1.0 and 3.0 mm/day at the superior and inferior regions, respectively. The distraction period was 13 days with no latency period. Vector and rate of distraction were remotely monitored without radiographs, using the device sensor. After fixation and euthanasia, the mandible and digastric muscles were harvested. The ex vivo appearance, stability, and radiodensity of the regenerate were evaluated using a semiquantitative scale. Percent surface area (PSA) occupied by bone, fibrous tissue, cartilage, and hematoma were calculated using histomorphometrics. The effects of DO on the digastric muscles and mandibular condyles were assessed via microscopy, and degenerative changes were quantified. The animal was distracted to 21 mm and 24 mm on the right and left sides, respectively. Clinical appearance, stability, and radiodensity were scored as "3" bilaterally indicating osseous union. The total PSA occupied by bone (right = 75.53 ± 2.19%; left PSA = 73.11 ± 2.18%) approached that of an unoperated mandible (84.67 ± 0.86%). Digastric muscles and condyles showed negligible degenerative or abnormal histologic changes. This proof of principle study is the first report of osseous healing with no ill-effect on associated soft tissue and the mandibular condyle using bilateral, automated, continuous, and curvilinear DO at rates up to 3 mm/day. The model approximates potential human application of continuous automated distraction with a semiburied device.

Three-dimensional preoperative design of distraction osteogenesis for hemifacial microsomia

The purpose of this research was to simulate mandibular movement calculated from three-dimensional computed tomography (CT) data to determine the linear distractor position to correct mandibular deformities in a series of patients with hemifacial microsomia (HFM). Preoperative CT scans from 6 HFM patients were obtained and imported into a CT-based software program (Mimics) to produce three-dimensional images and data. After measurement of the mandibular deficiency in 3 dimensions (horizontal and vertical), the angle between the distraction device and the ramus was determined by a geometric calculation, and then the surgery was performed on the three-dimensional model constructed using the rapid prototyping technique. This planning method was finally used in the treatment of 6 HFM patients. The HFM was corrected, and a symmetrical facial contour obtained without any complications in these 6 patients. The results matched the expectation before surgery that the distractor elongation would range from 18 to 22 mm. The distraction tracing model fitted the actual postdistraction tracing to within 2 mm. The preoperative design and three-dimensional modeling technique are considered to be helpful in enhancing the predictability and improving the outcome of the treatment of distraction osteogenesis.

Imaging, virtual planning, design, and production of patient-specific implants and clinical validation in craniomaxillofacial surgery

The purpose of this article was to describe the workflow from imaging, via virtual design, to manufacturing of patient-specific titanium reconstruction plates, cutting guide and mesh, and its utility in connection with surgical treatment of acquired bone defects in the mandible using additive manufacturing by electron beam melting (EBM). Based on computed tomography scans, polygon skulls were created. Following that virtual treatment plans entailing free microvascular transfer of fibula flaps using patient-specific reconstruction plates, mesh, and cutting guides were designed. The design was based on the specification of a Compact UniLOCK 2.4 Large (Synthes(®), Switzerland). The obtained polygon plates were bent virtually round the reconstructed mandibles. Next, the resections of the mandibles were planned virtually. A cutting guide was outlined to facilitate resection, as well as plates and titanium mesh for insertion of bone or bone substitutes. Polygon plates and meshes were converted to stereolithography format and used in the software Magics for preparation of input files for the successive step, additive manufacturing. EBM was used to manufacture the customized implants in a biocompatible titanium grade, Ti6Al4V ELI. The implants and the cutting guide were cleaned and sterilized, then transferred to the operating theater, and applied during surgery. Commercially available software programs are sufficient in order to virtually plan for production of patient-specific implants. Furthermore, EBM-produced implants are fully usable under clinical conditions in reconstruction of acquired defects in the mandible. A good compliance between the treatment plan and the fit was demonstrated during operation. Within the constraints of this article, the authors describe a workflow for production of patient-specific implants, using EBM manufacturing. Titanium cutting guides, reconstruction plates for fixation of microvascular transfer of osteomyocutaneous bone grafts, and mesh to replace resected bone that can function as a carrier for bone or bone substitutes were designed and tested during reconstructive maxillofacial surgery. A clinically fit, well within the requirements for what is needed and obtained using traditional free hand bending of commercially available devices, or even higher precision, was demonstrated in ablative surgery in four patients.

Reproducibility of three-dimensional coordinate systems based on craniofacial landmarks: a tentative evaluation of four systems created on images obtained by cone-beam computed tomography with a large field of view

OBJECTIVES

To propose a method for evaluating the reproducibility of anatomical coordinate systems based on craniofacial skeletal landmarks and to tentatively evaluate four systems created on preoperative cone-beam computed tomography (CBCT) data obtained from mandibular prognathism patients in order to confirm the utility for actual patients' data.

MATERIALS AND METHODS

In three-dimensional images of 10 patients obtained by a CBCT with a large field of view, six dentists set four coordinate systems that were created in different ways, twice by plotting some landmarks situated in the superior portion of the maxillofacial skeletons. The 95% confidence ellipse of six objective landmarks related to the jaw and teeth (upper incisor, left upper first molar, lower incisor, left lower first molar, menton, and left gonion) were three-dimensionally drawn for each coordinate system. The ellipsoid volume was calculated to evaluate the reproducibility of the coordinate systems.

RESULTS

The reproducibility could be evaluated for each coordinate system using the method proposed. The coordinate systems that were created by landmarks situated at greater distances from each other showed relatively small ellipsoid volume in comparison to those with shorter distances between landmarks.

CONCLUSION

Anatomical coordinate systems with larger distances between the landmarks used were stable when landmarks related to the jaw and teeth were assigned as objective landmarks. The method proposed here was effective in terms of the reproducibility evaluation of a coordinate system.

Curvilinear mandibular distraction results and long-term stability effects in a group of 40 patients

BACKGROUND

The mandibular internal curvilinear distractor design produces a curvilinear vector to provide ideal three-dimensional curvilinear movements compared with the limited straight unidirectional predecessor devices. In this manner, it corrects craniofacial deformities as anatomically as possible, allowing simultaneous bidirectional (rotational and translational) mandibular movement and multidirectional distraction. The aim of this study was to quantify the sagittal and vertical mandibular changes achieved through curvilinear distraction and to assess the long-term effect of this generated bone.

METHODS

Forty patients (20 male and 20 female), with ages ranging from 5 to 55 years, who underwent mandibular distraction from December of 1999 to August of 2007 at Lucile Packard Children's Hospital in Stanford, California, were included. Preoperatively, postoperatively, and at follow-up (at least 2 years following distraction), panoramic and lateral cephalometric radiographs were traced by plotting different skeletal landmark points and were then analyzed.

RESULTS

All patients tolerated the curvilinear distraction process well through completion. The average of the mandibular body elongation recorded was 8 to 9 mm and 6 to 8 mm in the panoramic and cephalometric radiographs, respectively; whereas the vertical change of the mandibular ramus achieved was 10 to 12 mm and 10 to 11 mm, respectively. The curvilinear distraction effect on the mandible was found to be significantly stable when the long-term follow-up measurements were compared with the postoperative data revealed in the panoramic and lateral cephalometric radiographs for the two dimensions.

CONCLUSION

The internal curvilinear device is an effective tool that achieves a stable mandibular distraction, resulting in the correction of craniofacial deformities.

Mandibular hypoplasia with curvilinear distraction

Mandibular distraction with intraoral curvilinear distractor is an effective procedure for lengthening the mandibular corpus and ramus dimensions. Mandibular distractor is valuable for the treatment of hypoplastic mandible. The aim of this article was to describe the treatment of a patient with hypoplastic and severely retrognathic mandible resulting from isolated Pierre Robin sequence, by means of curvilinear distraction osteogenesis followed by fixed orthodontic treatment. As a result, the curvilinear path of distraction can form a new mandibular angle and bring the mandible significantly forward. Attention should be given for the stability of the treatment results.

Clinical application of curvilinear distraction osteogenesis for correction of mandibular deformities

PURPOSE

To report the use of a semiburied curvilinear distraction device, with a 3-dimensional (3D) computed tomography treatment planning system, for correction of mandibular deformities.

MATERIALS AND METHODS

This was a retrospective evaluation of 13 consecutive patients, with syndromic and nonsyndromic micrognathia, who underwent correction by curvilinear distraction osteogenesis. A 3D computed tomography scan was obtained for each patient and imported into a 3D treatment planning system (Slicer/Osteoplan). Surgical guides were constructed to localize the osteotomy and to drill holes to secure the distractor's proximal and distal footplates to the mandible. Postoperatively, patients were followed by clinical examination and plain radiographs to ensure the desired vector of movement. At end distraction, when possible, a 3D computed tomography scan was obtained to document the final mandibular position.

RESULTS

Of the 13 patients, 8 were females and 5 were males, with a mean age of 11.9 years (range 15 months to 39 years). All 13 underwent bilateral mandibular curvilinear distraction. Of the 13 patients, 8 were 16 years old or younger and 5 were younger than 6 years of age. The diagnoses included Treacher Collins syndrome (n = 3), Nager syndrome (n = 3), craniofacial microsomia (n = 2), post-traumatic ankylosis (n = 1), and micrognathia (syndromic, n = 3; nonsyndromic, n = 1). The correct distractor placement, vector of movement, and final mandibular position were achieved in 10 of 13 patients. In the other 3 patients, the desired jaw position was achieved by "molding" the regenerate.

CONCLUSIONS

The use of a semiburied curvilinear distraction device, with 3D treatment planning, is a potentially powerful tool to correct complex mandibular deformities.

Reproducibility of maxillofacial anatomic landmarks on 3-dimensional computed tomographic images determined with the 95% confidence ellipse method

OBJECTIVE

To assess the plotting reproducibility of landmarks on 3-dimensional computed tomography (3D-CT) images through use of the 95% confidence ellipse in order to propose sufficiently stable coordinate systems for 3D-CT measurements.

MATERIALS AND METHODS

Six dentists plotted 19 landmarks twice on 3D-CT images. Scatterplots and the 95% ellipses were produced 3-dimensionally, and the areas of the ellipses were calculated for evaluating the reproducibility of landmarks.

RESULTS

The plotting reproducibility of each landmark showed characteristic features. Among five landmarks (the sella [S], nasion [N], basion [Ba], orbitale [Or], and true porion [Po]) that are frequently used as reference points on cephalograms, Ba showed the smallest areas for all three coordinate axes, indicating high reproducibility. The coronoid process (CP) and the tooth-related landmarks showed relatively high reproducibility.

CONCLUSION

Sufficiently stable coordinate axes could be proposed for different treatments and studies.

Comparison of different registration methods for surgical navigation in cranio-maxillofacial surgery

BACKGROUND

Surgical navigation requires registration of the pre-operative image dataset with the patient in the operation theatre. Various marker and marker-free registration techniques are available, each bearing an individual level of precision and clinical practicability. In this study the precision of four different registration methods in a maxillofacial surgical setting is analyzed.

MATERIALS AND METHODS

A synthetic full size human skull model was registered with its computer tomography-dataset using (a) a dentally mounted occlusal splint, (b) the laser surface scanning, (c) five facial bone implants and (d) a combination of dental splint and two orbital bone implants. The target registration error was computed for 170 landmarks spread over the entire viscero- and neurocranium in 10 repeats using the VectorVision2 (BrainLAB AG, Heimstetten, Germany) navigation system. Statistical and graphical analyses were performed by anatomical region.

RESULTS

An average precision of 1mm was found for the periorbital region irrespective of registration method (range 0.6-1.1mm). Beyond the mid-face, precision linearly decreases with the distance from the reference markers. The combination of splint with two orbital bone markers significantly improved precision from 1.3 to 0.8mm (p<0.001) on the viscerocranium and 2.3-1.2mm (p<0.001) on the neurocranium.

CONCLUSIONS

An occlusal splint alone yields poor precision for navigation beyond the mid-face. The precision can be increased by combining an occlusal splint with just two bone implants inserted percutaneously on the lateral orbital rim of each side.

Range of Curvilinear Distraction Devices Required for Treatment of Mandibular Deformities

PURPOSE

The purpose of this study was to determine the range of fixed trajectory curvilinear distraction devices required to correct a variety of severe mandibular deformities.

MATERIALS AND METHODS

Preoperative computed tomography (CT) scans from 18 patients with mandibular deformities were imported into a CT-based software program (Osteoplan). Three-dimensional virtual models of the individual skulls were made with landmarks to track movements. An ideal treatment plan was created for each patient. Upper and lower boundaries for the dimensions of curvilinear distractors were established based on manufacturing and geometric constraints. Then, anatomically acceptable distractor attachment points were identified on the models using proximal and distal grids. Treatment plans were simulated for a series of distractors with varying radii of curvature, elongations (arc-length of device), and placements along the grids. The outcomes using these distractors were compared with the ideal treatment plans. Discrepancies were quantified in millimeters by comparing landmarks in the simulated versus ideal movements.

RESULTS

Approximately 400,000 simulated 3-dimensional movements, based on the distractor parameters and variations in placement were computationally evaluated for the 18 cases. It was determined that, by varying distractor placement, a family of 5 distractors, with 3, 5, 7, and 10 cm radii of curvature and a straight-line device, could be used to treat all 18 cases to within 1.8 mm of error.

CONCLUSIONS

The results of this study indicate that a family of 5 curvilinear distractors may suffice to treat a broad range of mandibular deformities.