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Many terms such as twist, compress, bend, and stretch, describe how materials behave when subjected to mechanical stresses. Subjective adjectives to describe the property of materials such as hard or brittle are imprecise and impedes proper understanding of important principles needed in planning and performing surgical treatments. The viability of tissue and time dependent variables effect healing and compound the issue. Some parameters are time dependent (strain rate), while others are nearly independent of time (Young’s modulus). The craniofacial skeleton and enveloping soft tissues are viscoelastic composite materials which undergo time-dependent changes upon loading. The ability to remodel and respond to environmental changes makes them “smart,” reenforcing where needed and removing where not required based on a set of predetermined upper and lower thresholds. This mini review has 7 sections on engineering principles that underpin craniofacial surgery: (1) The general concept of mechanics: load, force, stress, strain, compression, tension, shear, stress-strain curves and values derived from them such as Young’s modulus, fatigue damage, and load- shearing. (2) Material properties of bone and suture and structural engineering of the craniofacial skeleton in normal and pathological conditions. (3) Fixation using wires, screws, and plates: anatomy and function of screws and plates, locking plates, lag screws, internal and external fixators. (4) Biomechanics of distraction osteogenesis and the effects of radiation. (5) Finite element analysis and other computational biomechanical tools. (6) Virtual surgical planning, cutting guides, and intra-operative navigation. (7) Tissue engineering: design goals, criteria, and constraints. An appreciation and understanding of these biomechanical principles will help craniofacial surgeons to facilitate intrinsic optimization and better treat complex morphological problems, helping one achieve the most favorable and durable results. The biological responses to mechanical stress are extremely important as well, but due to space constraints, they will be the subject of a separate dedicated review. more...

BACKGROUND Variations in the clinical presentation of the unilateral cleft lip resulted in numerous surgical repair techniques used around the world. No universally accepted method exists to evaluate aesthetic surgical results. The purpose of this study is to use the Hubli lip grading system, developed by Smile Train, to evaluate the aesthetic results of unilateral cleft lip repairs based on the surgical technique used. METHODS A retrospective review was conducted of unilateral cleft lip repair operations performed by Smile Train surgeons throughout Africa, Americas, Asia Pacific, and Europe and Middle East between 2014 and 2018. Using the Hubli lip grading criteria, factoring in cleft severity, acceptable outcomes were identified and compared with the surgical technique used. RESULTS Eight thousand forty-one unilateral cleft lip repairs were reviewed. The majority utilized the rotational advancement technique (n = 5541, 68.9%) with a statistically significant percentage of acceptable outcomes (92.1%), followed by an acceptance rate of 91.9% with variations of the z-plasty technique, 90.5% with the straight-line repair and its variations, and 88.4% using "other" techniques (P more...

Objective: Viral infections during pregnancy can cause disturbance in normal craniofacial morphogenesis. While some pathogens such as cytomegalovirus and herpes simplex are familiar to us, others remain obscure. This review examines the arbovirus-induced cranial deformities and combines biomechanics with growth dynamics to gain a deeper appreciation of this complex morphogenetic process. Materials and Methods: Using Wolfram Alpha, we analyzed the impact of cell population changes. The growth dynamics of the brain, and thus the size of the calvarium, followed 2 potential logistic curves: compensated and uncompensated. To understand the potential mechanism of cell loss, we performed literature review on maternal immune activation and viral tropism for neurons and glial cells. Results: With arboviral infections such as Zika, uncompensated loss of cells during the critical phases of fetal brain development reduces the intracranial mass and therefore decreases the tensile stress across the cranial sutures. The deflationary effect produces microcephaly by subduction and reduced osteogenesis seen clinically in these infants. Conclusion: Many viral infections cause intense maternal immune activation, some have neurotropism and can result in cell loss within the developing cranium. Unable to overcome this loss, the cranium assumes a new, abnormal shape and volume. Secondary calvarial deformities is due to, and should not cause, changes in brain development. more...

Background Unilateral lambdoid synostosis (ULS) is the rarest form of craniosynostosis. Due to the associated cranio-caudal shift seen in ULS, surgical correction is technically challenging from a morphological standpoint. Herein, the authors present a novel "Sand-Dollar and Staves" technique for the repair of ULS. Methods A zigzag coronal incision is performed, and an anteriorly-based pericranial flaps are elevated. Prefabricated cutting guides are placed and the calvarium is marked. To treat the flattening on the ipsilateral side, a wedged suturectomy is performed with additional barrel staves. A large circle centered over the bulging on the contralateral side is cut out above the open lambdoid suture. This piece is barrel staved in a radial fashion, leaving the center intact and creating a Sand-Dollar appearance. This disk is then flattened and trimmed. The modified Sand-Dollar is fixed using an absorbable plating system. While gentle pressure is applied to the Sand-Dollar piece as it is being secured, the ipsilateral side demonstrates compensatory filling. Results are evaluated using the Whitaker Classification. Results Four patients underwent surgical correction with this technique. The procedure was performed at mean age of 11.7 months. The mean operative time was 2.5 hours. Intraoperative blood loss was 50 to 100 ml. Total hospitalization time was 2 to 3 days. No post-operative complications were encountered. Whitaker scores ranged from 1 to 1.5. The mean follow-up was 10 months. Conclusion The Sand-Dollar and Staves procedure is a novel, single-stage approach for the management of ULS with decreased operative time, blood loss, and hospital stay with satisfactory aesthetic outcomes. more...

Dermoid cysts are rare, benign neoplasms that develop when ectodermal tissue is ectopically included during neural tube closure. Only 0.7% to 1.8% of dermoid cysts occur intracranially, and these make up only 0.3% of all intracranial tumors. Definitive management of intracranial dermoid cysts is achieved with surgical excision, with the primary goal being removal of the lesion before rupture or infection occurs. The authors report the multidisciplinary management of a 6-month-old patient with a midline intranasal dermoid cyst with intracranial involvement successfully treated with surgical resection. The surgical approach included Neurosurgical access with a bifrontal approach to remove the intracranial portion, then Plastic Surgery accessed and removed the intranasal portion through a transcolumellar and infracartilaginous dissection. The entire cyst was successfully removed without rupture. The patient's postoperative course was without complication.Timely preoperative imaging and diagnosis were crucial to the success of this operation. When considering the possibility of a midline dermoid cyst with intracranial extension, it is essential to obtain proper imaging to distinguish between lesions on the differential diagnosis and to define extent of extension. Once diagnosed, surgical planning requires a multidisciplinary approach. Considerations for the optimal surgical approach to intracranial, intranasal dermoids include maximizing surgical exposure and ensuring an aesthetically pleasing reconstructive outcome. more...

In patients with Pierre Robin sequence (PRS), understanding the mechanism of airway obstruction and the potential for concurrent airway lesions is important for determining appropriate intervention. When concomitant airway anomalies are present with PRS, mandibular distraction osteogenesis alone is often contraindicated and unsuccessful at alleviating the obstruction, mandating the need for tracheostomy. Herein, the authors present the second-reported case of PRS with concomitant complete tracheal rings and highlight the importance collaborative surgical efforts to avoid tracheostomy. Our patient was born with signs and symptoms of PRS and concomitant complete tracheal rings. At birth, he developed respiratory compromise that was resistant to invasive and noninvasive intervention and was transferred to our care. The severity of his airway compromise necessitated operative intervention. Due to the patient's complex medical condition, avoiding the long-term sequelae of a tracheostomy and performing mandibular distraction was favorable. However, due to his multi-level airway disease, a 2-staged approach was planned: sliding tracheoplasty to release the tracheal rings, followed by mandibular distraction to correct the micrognathia. The patient tolerated both procedures and was successfully distracted and eventually weaned into room air. When managing patients with PRS in the setting of severe respiratory distress, securing the airway and carefully evaluating for concomitant airway anomalies is crucial. Even in the setting of multi-level airway disease where mandibular distraction is typically contraindicated, by directly addressing each anatomic level of airway obstruction, the airway can be safely secured and the resultant consequences of tracheostomy can be avoided. Careful planning with a multidisciplinary team is essential. more...

Background The Millard rotation-advancement cleft lip repair is the most commonly performed cleft lip repair. An extended perialar incision allows for further advancement of the lateral lip element and improved positioning of the alar base. There is a lack of data evaluating differences in nasal alar growth when the perialar incision is utilized. This study compares the long-term effects of a perialar incision on the alar surface area of unilateral cleft lip patients who underwent a Millard cleft lip repair. Methods Thirty-seven patients with a diagnosis of unilateral cleft lip treated with a Millard primary lip repair were studied. A perialar incision was utilized in 16 patients while 21 patients underwent a standard Millard repair. 3dMD facial images were taken at least 10 years after the initial lip repair. Using the patient's non-cleft side as an internal control, the Alar Ratio (AR) was calculated, defined as the cleft alar surface area divided by the non-cleft alar surface area. Results The AR was significantly greater in the standard Millard repair group compared to the perialar incision group, 0.74 and 0.64 respectively (P = .02). The incomplete cleft population demonstrated a more profound difference between the treatment groups (0.82 and 0.62, respectively). Conclusions This study reveals an association between a perialar incision and decreased alar surface area. Long-term follow up results suggest a perialar scar restricts alar growth leading to significant asymmetry between the cleft and non-cleft sides. Therefore, surgical technique must be carefully considered prior to utilizing a perialar incision during unilateral cleft lip repair. more...

Pierre Robin sequence is a triad of micrognathia, glossoptosis, and airway obstruction that has reported associations with numerous birth defects and anomalies including craniocervical pathologies. Given the number of airway assessments and neck manipulations these neonates experience, undetected cervical instability can result in detrimental consequences. The authors present a case of a neonate with non-syndromic Pierre Robin sequence planned for mandibular distraction osteogenesis that developed abnormal motor activity following intubation. The patient was eventually diagnosed with cervical spine stenosis and craniocervical instability after radiologic investigation. This paper demonstrates the significance of preoperative cervical spine evaluation and the importance of maintaining high level of suspicion when performing neck manipulations in those high-risk infants. more...

This chapter is a synopsis of diabetic wounds. We begin with an overview of the scope of the problem and examine tissue equilibrium in quantitative details, incorporating concepts of basic biomechanics and endurance limits. The key points are the interdependence of cell and the extracellular matrix (ECM): with the cells producing ECM and ECM affecting cell fate and behavior. This is followed by biochemical and cellular basis of pathogenesis of diabetic wounds. There is clearly a dysregulation of energy metabolism with sustained nutrient and caloric excess. With persistent intake of carbohydrates and fat exceeding the nominal capacity to process, predictable detrimental effects are inevitable. It is at this level, prevention should be seriously contemplated and implemented. It is much better to not be obese and diabetic to begin with. However, once overweight and hyperglycemic, the local regional and the systemic effects combine to cause cellular swelling, apoptosis, necrosis, ischemia, hypoxia, ischemia-reperfusion, protein glycation, neuropathy, microangiopathy, persistent inflammation, and eventually tissue breakdown and chronic wounds. When the normal sequence of events is disrupted, a diabetic wound can remain in a pro-inflammatory stage and resist innate and therapeutic attempts to regain the normal cadence. We then inventoried the current, standard, clinical protocols and available commercial products, emphasizing those few that are evidence-based. Of particular importance are the roles of oxygen as free radicals are highly detrimental but paradoxically some evidences suggest a beneficial role of hyperbaric oxygen. The personalized approach will be realized with a proposed proteomic assessment of the wound, to precisely determine what are in excess and what are insufficient to allow targeted and individualized therapy. The advances in stem cell biotechnology and tissue derivatives are translating into the clinical arena; and together with surgical managements, constitute the subjects of the last two sections. more...

Damage-associated molecular patterns (DAMPs) are released following tissue injury and cell death and can activate pro-inflammatory pathways. Prototypical DAMPs include the high-mobility group box 1 (HMGB1) protein which is released from necrotic cells. We have shown that pressure overload increases infarct size in association with poorer functional recovery of the heart subjected to an ischemia-reperfusion insult. In this study, we tested the hypothesis that pressure overload increases HMGB1 expression in association with increased pro-inflammatory changes and consequent cell death. Accordingly, hearts of male Sprague-Dawley rats were subjected to an ischemia (40 min) reperfusion (15 min) insult with perfusion pressure set at either 80 or 160 cmH 2 O. Thereafter, hearts were processed for flow cytometry-based, Western blotting and immunostaining studies. The ischemic-reperfused hearts subjected to the high pressure displayed greater expression of HMGB-1 in association with increased phosphorylation of c-jun-NH2-terminal kinase (JNK) and production of the inflammasome-associated cytokine, interleukin-1β. These changes were associated with greater disruption of mitochondrial membrane potential and increased apoptotic and necrotic cell death in hearts subjected to the high pressure. Collectively, the results suggest that pressure-related upregulation of HMGB1-inflammasome signaling contributes importantly to exacerbated cell death in the ischemic-reperfused heart. more...