Marcelo Pires Prado

Keratoconus prediction using a finite element model of the cornea with local biomechanical properties

PURPOSEnThe ability to predict and understand which biomechanical properties of the cornea are responsible for the stability or progression of keratoconus may be an important clinical and surgical tool for the eye-care professional. We have developed a finite element model of the cornea, that tries to predict keratoconus-like behavior and its evolution based on material properties of the corneal tissue.nnnMETHODSnCorneal material properties were modeled using bibliographic data and corneal topography was based on literature values from a schematic eye model. Commercial software was used to simulate mechanical and surface properties when the cornea was subject to different local parameters, such as elasticity.nnnRESULTSnThe simulation has shown that, depending on the corneal initial surface shape, changes in local material properties and also different intraocular pressures values induce a localized protuberance and increase in curvature when compared to the remaining portion of the cornea.nnnCONCLUSIONSnThis technique provides a quantitative and accurate approach to the problem of understanding the biomechanical nature of keratoconus. The implemented model has shown that changes in local material properties of the cornea and intraocular pressure are intrinsically related to keratoconus pathology and its shape/curvature.

Cartilage lesions and ankle osteoarthrosis: review of the literature and treatment algorithm,

The main etiology of ankle osteoarthrosis is post-traumatic and its prevalence is highest among young individuals. Thus, this disease has a great socioeconomic impact and gives rise to significant losses of patients’ quality of life. The objective of its treatment is to eliminate pain and keep patients active. Therefore, the treatment should be staged according to the degree of degenerative evolution, etiology, joint location, systemic condition, bone quality, lower-limb alignment, ligament stability and age. The treatment algorithm is divided into non-surgical therapeutic methods and options for surgical treatment. Joint preservation, joint replacement and arthrodesis surgical procedures have precise indications. This article presents a review on this topic and a proposal for a treatment algorithm for this disease.

CUBOID-NAVICULAR TARSAL COALITION.

The authors present the case of a nine-year-old female patient who presented with pain in her right foot associated with physical activities. After this case was diagnosed as cuboid-navicular tarsal coalition, the patient was treated surgically with resection of the coalition, thereby resolving the symptoms. The literature was reviewed and the importance of adequate physical examination and imaging assessment for investigating foot pain in children and adolescents was discussed.

Coalizão tarsal cuboide-navicular

The authors present a case of a 9-year-old female patient who presents with complaints of pain in her right foot associated with physical activities. After the diagnosis of an osseous cuboid navicular coalition she was treated surgically with resection of the coalition, with symptoms resolved. The literature is reviewed and the importance of adequate physical examination and image exams to investigate foot pain in children and teenagers is discussed.

Estabilização da artrodese da articulação tarsometatársica: estudo biomecânico

SUMMARY Introduction: Tarsometatarsal arthrodeses are an effective the- rapeutic alternative for treating symptomatic osteoarthroses of the Lisfranc joint. Stabilization methods available include: Kirschners wires, cortical screws, plates and screws and sta- ples. The stability provided and the surgical technique employed with each material is discussed in literature. Purpose: To com- pare compression forces and biomechanical stability of tarso- metatarsal joint fixation with cortical screws and staples. Case series and method: Ten fresh male cadavers with ages ranging from 35 to 49 years were selected and submitted to bilateral dissection of the cuboidal and 4th metatarsal bones, with joint surfaces decortification and fixation with cortical screw - Cortical Screw 3.5mm Impol, and Uni-clip ® Staple 2.0 NewDeal. Results: All the 20 biomechanical assays were completed. The statistical analysis of the methods using staples vs. cortical screw con- cerning accrued energy until reaching the assays peak force p= 0.047, and the accrued energy until the completion of the assay p= 0.047 showed a significant difference. Conclusion: Load peaks supported by staples and cortical screws are sig- nificantly reduced with age. Superior force values are found for staples in osteoporotic bones. The accrued energy on graphs work areas in assays with staples is shown to be statistically superior to cortical screws values.