Applied mechanics of the Puricelli osteotomy: a linear elastic analysis with the finite element method

<p>Abstract</p> <p>Background</p> <p>Surgical orthopedic treatment of the mandible depends on the development of techniques resulting in adequate healing processes. In a new technical and conceptual alternative recently introduced by Puricelli, osteotomy is performed in a more distal region, next to the mental foramen. The method results in an increased area of bone contact, resulting in larger sliding rates among bone segments. This work aimed to investigate the mechanical stability of the Puricelli osteotomy design.</p> <p>Methods</p> <p>Laboratory tests complied with an Applied Mechanics protocol, in which results from the Control group (without osteotomy) were compared with those from Test I (Obwegeser-Dal Pont osteotomy) and Test II (Puricelli osteotomy) groups. Mandible edentulous prototypes were scanned using computerized tomography, and digitalized images were used to build voxel-based finite element models. A new code was developed for solving the voxel-based finite elements equations, using a reconditioned conjugate gradients iterative solver. The Magnitude of Displacement and von Mises equivalent stress fields were compared among the three groups.</p> <p>Results</p> <p>In Test Group I, maximum stress was seen in the region of the rigid internal fixation plate, with value greater than those of Test II and Control groups. In Test Group II, maximum stress was in the same region as in Control group, but was lower. The results of this comparative study using the Finite Element Analysis suggest that Puricelli osteotomy presents better mechanical stability than the original Obwegeser-Dal Pont technique. The increased area of the proximal segment and consequent decrease of the size of lever arm applied to the mandible in the modified technique yielded lower stress values, and consequently greater stability of the bone segments.</p> <p>Conclusion</p> <p>This work showed that Puricelli osteotomy of the mandible results in greater mechanical stability when compared to the original technique introduced by Obwegeser-Dal Pont. The increased area of the proximal segment and consequent decrease of the size of lever arm applied to the mandible in the modified technique yield lower stress values and displacements, and consequently greater stability of the bone segments.</p

Adult cerebellar medulloblastoma: CT and MRI findings in eight cases

Medulloblastoma is a brain tumor of neuroepithelial origin, which represents 15 to 30% of all pediatric brain tumors, and less than 1% of CNS adult neoplasms. We report the imaging findings of 8 adult patients with medulloblastoma. The mean age was 35 years, ranging from 20 to 65 years, and the male:female rate was 3:5. The tumors were predominantly lateral (63%), hyperdense on CT scans (83%), and on the MRI, hypointense on T1 (100%) and hyperintense on T2 (80%) weighted images. It was seen intratumoral necrosis and cysts in six cases and calcifications in three. Hydrocephalus was observed in 5 cases and brain stem invasion in four. The imaging findings of medulloblastomas in adults are different of those in child, and also nonspecific. Although these tumors are uncommon in adults, they must be considered in the differential diagnosis of cerebellar masses in the posterior fossa of this age group

Immunoglobulins intrathecal synthesis evaluation in bone marrow transplantation

The central nervous system involvement in chronic graft versus host disease (GVHD) has been suggested. Chronic GVHD resembles auto immune connective tissue disorders. In order to investigate the immunoglobulin intra blood brain barrier (BBB) synthesis during chronic GVHD, and contribute to understanding the pathophysiology of the disease, we studied 33 patients who underwent allogeneic bone marrow transplants (BMT) from HLA identical related donors. Immunoglobulin intra BBB synthesis was investigated quantitative and qualitatively. The samples were collected pre BMT, pos BMT and during chronic GVHD. There were no evidence of immunoglobulin intra BBB synthesis, and no oligoclonal bands were found. Only isolated cases suggested IgG and IgA intra BBB synthesis, and in one case IgM during GVHD.UNIV FED PARANA,HOSP CLIN,SERV TMO,BR-80060900 CURITIBA,PARANA,BRAZILUNIV FED PARANA,HOSP CLIN,DISCIPLINA NEUROL,BR-80060900 CURITIBA,PARANA,BRAZILUNIFESP,ESCOLA PAULISTA MED,DISCIPLINA IMUNOL,SAO PAULO,BRAZILUNIV SAO PAULO,FAC MED,CTR INVEST NEUROL,BR-05508 SAO PAULO,BRAZILUNIFESP,ESCOLA PAULISTA MED,DISCIPLINA IMUNOL,SAO PAULO,BRAZILWeb of Scienc