Effect of Class II elastics on different mandibular arch preparation stabilized with aligners and stainless-steel wires: A FEM study.

Finite element models that simulate the effects of class II elastics on the mandibular arch in six different scenarios, using various immobilization methods of the posterior dentition, were studied. Per-element distribution of linear elastic stress-strain and total displacement was computed. Maximum strain on the PDL and maximum stress on alveolar bone increased with posterior tip-back and with the use of archwires vs. aligners. The configuration of the dentition affects the performance of aligners. They perform best on an unlevelled mandibular arch. Applying class II elastics results in vertical side effects that can be modulated by various mandibular stabilization methods. This is likely to be clinically relevant for high-angle patients and may explain the differing effects on the facial profile observed using various treatment modalities. 1-Increasing mandibular molar tip-back generally resulted in less eruption tendencies, with mandibular anchorage preparation resulting in the least amount of calculated vertical displacement. 2-Unexpectedly, with class II forces the use of aligner technology on an unlevelled curve of Spee resulted in improved vertical control when compared to aligner use on a levelled dentition. 3-Generally, using an archwire results in better transmission of stresses to adjacent teeth than the use of aligners. 4-Simulating interarch elastics requires implementing a medial component/orientation of the forces to better emulate clinical situations. 5-A hypothetical configuration: 15o tip-back of the mandibular second molar and aligner stabilization displayed the least amount of vertical movement and the most forward horizontal movement of the 2nd molar.

Facial Fractures: Pearls and Perspectives.

LEARNING OBJECTIVES: After studying this article, the participant should be able to: 1. Describe the A-frame configuration of anterior facial buttresses, recognize the importance of restoring anterior projection in frontal sinus fractures, and describe an alternative design and donor site of pericranial flaps in frontal sinus fractures. 2. Describe the symptoms and cause of pseudo-Brown syndrome, describe the anatomy and placement of a buttress-spanning plate in nasoorbitoethmoid fractures, and identify appropriate nasal support alternatives for nasoorbitoethmoid fractures. 3. Describe the benefits and disadvantages of different lower lid approaches to the orbital floor and inferior rim, identify late exophthalmos as a complication of reconstructing the orbital floor with nonporous alloplast, and select implant type and size for correction of secondary enophthalmos. 4. Describe closed reduction of low-energy zygomatic body fractures with the Gillies approach and identify situations where internal fixation may be unnecessary, identify situations where plating the inferior orbital rim may be avoided, and select fixation points for osteosynthesis of uncomplicated displaced zygomatic fractures. 5. Understand indications and complications of use for intermaxillary screw systems, understand sequencing panfacial fractures, describe the sulcular approach to mandible fractures, and describe principles and techniques of facial reconstruction after self-inflicted firearm injuries. SUMMARY: Treating patients with facial trauma remains a core component of plastic surgery and a significant part of the value of a plastic surgeon to a health system.

Anthropometrically-Based Surgical Technique for Tessier 3 Cleft Reconstruction.

Craniofacial clefts are rare entities, with an incidence reported as 1.43 to 4.85 per 100,000 births. The Tessier number 3 cleft, the most medial of the oblique clefts, can manifest as clefting of the lip between the canine and lateral incisors, colobomas of the nasal ala and lower eyelid, and inferior displacement of the medial canthus-frequently disrupting the lacrimal system with extreme variability in expressivity (Eppley).Literature on cleft lip repair is extensive and has evolved to incorporate anthropometric techniques, based on identifiable landmarks and anthropometric measurements that are compared with contralateral unaffected anatomy or population means and tracked over time to assess impact on growth. Recent focus has been placed on "subunit" repair that repairs "like with like." These approaches have resulted in a remarkable reproducibility of methods and outcomes.Facial cleft surgery publications are sparse due to the rarity of the disorders, and consensus has yet to develop on standardized landmarks, reference measurements, and principles of repair. The authors describe a method of correcting incomplete unilateral Tessier 3 cleft based on the principles described above. Intraoperative photographs, including secondary revisions, as well as immediate and long-term postoperative results are presented.

Anthropometric Effect of Mucoperiosteal Nostril Floor Reconstruction in Complete Cleft Lip.

OBJECTIVE: The primary objective of this study was to investigate whether growth impairment in children with cleft lip is caused by reconstructing the nostril floor using lateral nasal and premaxillary mucoperiosteal flaps. The effects on growth and symmetry of tip rhinoplasty at the time of initial repair, as well as cleft sidedness are similarly investigated. METHODS: An Institutional Review Board approved, retrospective, single-center study at an academic children's hospital from July 2005 to 2010 was designed. Seventy-four patients with unilateral cleft lip ± palate were followed postsurgical repair of the cleft lip deformity. Serial digital photographs from clinical encounters were analyzed. Anthropometric measurements of 10 soft tissue landmarks were extracted from anteroposterior and submental vertex views at serial visits; growth velocities, defined as c = Δd/Δt, were generated using linear mixed models on selected measurements to study time-related changes on growth. The effects on growth and symmetry of primary tip rhinoplasty on perinasal landmarks and nostril floor reconstruction with medial and lateral nasal mucoperiosteal flaps on perioral and perinasal landmarks were analyzed. Proxies for midfacial height (en-al) and maxillary height (al-ch) were used to evaluate the effect of mucoperiosteal dissection, whereas nostril width, height, and angle were used as proxies to evaluate the effects of tip rhinoplasty. RESULTS: Seventy-four patients met the inclusion criteria. Midface height (En-Al) growth velocity was 0.014 mm/month and maxillary height (Al-Ch) was relatively stable at -0.0059 mm/month with no difference between the subgroups. Nostril height growth was -0.0046 mm/month, nostril width was 0.03 mm/mo, and nostril angle -0.09 °/mo showed no difference between patient with or without primary tip rhinoplasty. Patients with complete cleft showed more asymmetry than those with incomplete clefts in lip and maxillary landmarks at T0 (P < 0.001). CONCLUSIONS: Mucoperiosteal reconstruction of the nostril floor at the time of lip repair does not affect anthropometric growth velocities over a 5-year follow-up. Within the limitations of the selected landmarks, primary tip rhinoplasty did not significantly improve symmetry at 5 years, but also did not affect the growth of the nose. Patients with complete clefts display more postoperative asymmetry than those with incomplete clefts.

Dual-porosity poroviscoelasticity and quantitative hydromechanical characterization of the brain tissue with experimental hydrocephalus data.

Hydromechanical brain models often involve constitutive relations which must account for soft tissue deformation and creep, together with the interstitial fluid movement and exchange through capillaries. The interaction of rather unknown mechanisms which produce, absorb, and circulate the cerebrospinal fluid within the central nervous system can further add to their complexity. Once proper models for these phenomena or processes are selected, estimation of the associated parameters could be even more challenging. This paper presents the results of a consistent, coupled poroviscoelastic modeling and characterization of the brain tissue as a dual-porosity system. The model draws from Biot's theory of poroviscoelasticity, and adopts the generalized Kelvin's rheological description of the viscoelastic tissue behavior. While the interstitial space serves as the primary porosity through which the bulk flow of the interstitial fluid occurs, a secondary porosity network comprising the capillaries and venous system allows for its partial absorption into the blood. The correspondence principle is used in deriving a time-dependent analytical solution to the proposed model. It allows for identical poroelastic formulation of the original poroviscoelastic problem in the Laplace transform space. Hydrocephalus generally refers to a class of medical conditions which share the ventricles enlargement as a common feature. A set of published data from induced hydrocephalus and follow-up perfusion of cats' brains is used for quantitative characterization of the proposed model. A selected portion of these data including the ventricular volume and rate of fluid absorption from the perfused brain, together with the forward model solution, is utilized via an inverse problem technique to find proper estimations of the model parameters. Results show significant improvement in model predictions of the experimental data. The convoluted and coupled solution results are presented through the time-dependent plots of the ventricular volume undergoing the perfusion experiment. The plots demonstrate the intricate interplay of viscous and poroelastic diffusive time scales, and their competition in reaching the steady state response of the system.

Safety and efficacy of recombinant human bone morphogenetic protein 2 on cranial defect closure in the pediatric population.

BACKGROUND: Traditional reconstructive options for cranial defects include autogenous bone graft, bone substitutes, and synthetic materials. The established standard for repairing cranial defects is autogenous bone. However, young children do not have abundant donor sites for bone harvest, which leads to challenges in closing calvarial defects. Synthetic materials are not ideal alternatives because they require subsequent retrieval and are prone to infection. Their long-term effects on growth of the skull are also not well studied. Bone morphogenetic protein 2 (BMP-2), are shown to positively affect closure of cranial defects in animal models. We present a study comparing the efficacy and safety of closure of cranial defect with bone graft augmented with recombinant human BMP-2 (rhBMP-2) and compared with a series of patients treated with bone graft alone. METHODS: This study is a retrospective multicenter evaluation of 36 patients spanning 5 years. Twenty-one patients undergoing cranial defect closure augmented with rhBMP-2 were compared with 15 patients who underwent cranial defect closure using cranial bone shavings alone. We measured preoperative and postoperative defect size on volumetric computed tomographic scan reconstructions to compare defect sizes. RESULTS: The rhBMP-2 group had slightly increased proportional closure compared with the control group, 86% versus 76% (P < 0.018), respectively. Two patients in the rhBMP-2 group had postoperative fusion of a suture that was known to be patent at the time of cranial defect closure. No instances of brain edema, herniation, airway compromise, or other adverse effects directly attributable to rhBMP-2 were observed. CONCLUSIONS: Bone morphogenetic protein 2 may increase the amplitude and uptake of cranial bone grafts in cranial defect closure. This study shows that defect sizes of up to 16 cm can be reliably closed using this technique. Postoperative fusion of uninvolved sutures in 2 patients indicates that rhBMP-2 may have unreported adverse effects; consideration of this finding should be weighed against the benefit of improved closure of calvarial defects.

Resolution and recurrence of vitiligo following excision of congenital melanocytic nevus.

Vitiligo associated with halo congenital melanocytic nevus (CMN) is rare. There are limited reports in the literature, especially with regard to CMN excision. We present the case of a 5-year-old girl who presented with vitiligo of the periorbital and axillary regions and halo formation around CMN of the buttock. The lesion was excised, and all areas of vitiligo improved, but 18 months postoperatively, a halo of depigmentation appeared around the excision scar and later in the periorbital and axillary regions. In review of literature, there is only one report of excision of halo CMN and resultant improvement of vitiligo. Although initial resolution of vitiligo in this case was promising, the recurrence indicates that this complex process is not reliably controlled with excision of the inciting lesion.

Biomechanical effects of cranioplasty for defects using autogenous calvarial bone.

INTRODUCTION: Harvesting autogenous calvarial bone grafts can potentially weaken the donor site and make it more susceptible to trauma. Conversely, restoring the integrity of the cranial vault structure can result in better dissipation of traumatic energy. This study proposes to mathematically model traumatic situations to evaluate the effect of cranioplasty on biomechanical properties of the craniofacial skeleton. METHODS: Preoperative and 6-month postoperative computed tomography-generated DICOM data were used to extract a tetrahedral volumetric representation of the craniofacial skeleton. These data were then used in finite element solver-simulating traumatic events. RESULTS: Deformational stresses accumulate around defect edges and can serve as seed points for calvarial fractures at much lower energy levels in the preoperative models when compared to the postoperative models. Accumulation of stresses in the orbital roof/medial orbital wall areas was observed, similar to fracture patterns observed in the younger pediatric population CONCLUSIONS: Restoring architectural integrity of the craniofacial skeleton results in significant increased resistance to deformational stresses despite structural weakening caused by harvesting cranial bone.

A novel technique for attaining maxillomandibular fixation in the edentulous mandible fracture.

Edentulous mandible fractures present a unique and challenging surgical problem, particularly because of lack of occlusive dental surfaces to capitalize upon maxillomandibular fixation (MMF). We present a novel technique to achieve MMF using rigid plates spanning the oral cavity to fixate the maxilla to the mandible. The process is rapid and allows stability using the established principles of rigidity, external fixation, and osteosynthesis. This technique allows for a faster MMF than with a Gunning splint and allows for easier oral hygiene. An illustrative case and pre- and postoperative imaging are provided.

Spontaneous resolution of diabetes insipidus after cranioplasty and cranial defect repair.

We describe the resolution of persistent diabetes insipidus after cranioplasty with autogenous bone and bone morphogentic protein 2-infused collagen matrix in a patient who had large bilateral craniectomies for trauma. A potential pathogenic mechanism is presented.

Volumetric analysis of cranial vault distraction for cephalocranial disproportion.

The purpose of this study was to provide an objective analysis and quantify the intracranial volume change produced by cranial vault distraction osteogenesis. We recently published a technique to expand the cranial vault by distraction in symptomatic patients with findings of cephalocranial disproportion. Resolution of symptoms was documented in that publication. In this current study, we analyzed postdistraction intracranial volume changes in 11 consecutive patients retrospectively from 10/2001 to 11/2010 with institutional review board approval. These 11 patients were treated by cranial vault distraction osteogenesis for symptomatic cephalocranial disproportion. Pre- and postoperative CT DICOM data were analyzed using specialized software to generate finite element models. Intracranial and ventricular volumes were calculated. Topographical surface maps were generated to document and quantify areas of change. Possible effects on brain physiology are discussed. Pre- and postoperative CT scans were obtained at an average of 3.5 months prior to, and 4.2 months following distraction, respectively. Average age at distraction was 55.72 months (range 26-104 months). Operative time averaged 2 h 44 min (range 127-198 min, SD = 30.6). Intracranial and ventricular volumes increased by an average of 77.01 and 4.85 ml, respectively. Nonventricular intracranial volumes increased by 5.91%, 71.67 ml following distraction. All postoperative volume changes were statistically significant (p ≤ 0.000025). The ability to use the same methodology to quantify ventricular volume changes was unexpected. The fact that all ventricles expanded after distraction at approximately 10% of the total intracranial volume increase indicates that compensatory mechanisms had been activated. We conclude that this occurs at the expense of cerebral blood flow.

Delayed development of toxic shock syndrome following abdominal tissue expansion in a pediatric reconstruction patient: case report.

Toxic shock syndrome (TSS) is a potentially fatal postoperative complication, and even more so if the diagnosis is delayed. We present the case of a 7-month-old male infant who developed TSS as a complication of tissue expansion using an external port device. There have been 5 documented cases of TSS after tissue expander or breast prosthesis placement occurring in the adult population, however, there has not been a reported case of TSS in an infant. The long interval to development of TSS like symptoms, 4 months in this case, should not exclude TSS from the differential diagnosis. In a pediatric patient, a diffuse macular rash without the severe systemic symptoms on initial presentation can present as a diagnostic challenge. New diagnosis techniques are discussed that can shorten the time to a diagnosis of TSS. In this case, because the local bacterial count was low, the expanded tissue was transferred without complication.

Hyoid bone abnormalities in Pierre Robin patients.

Hyoid bone abnormalities have not been previously documented in association with Pierre Robin Sequence. Using three-dimensional (3D) reconstructions of helical computed tomography scans, we examined the hyoid bones of neonates affected with Pierre Robin Sequence and compared them to helical scans of unaffected controls. Severe hyoid bone abnormalities were observed in 7/28 cases, and mild abnormalities in another 16. The presence of severe abnormalities was significantly associated with swallowing dysfunction, while none of the neonates affected with Stickler's syndrome were observed to have severe hyoid abnormalities. The significance of these findings is unknown. Clinicians should be aware of these abnormalities because of the wide availability of 3D reformats.